Title of Invention: ESTROGEN RECEPTOR ALPHA POLYPEPTIDE SEQUENCE, DIAGNOSTIC AND THERAPEUTIC APPLICATIONS THEREOF Abstract: The present invention presents new insights in the mechanism of action of the estrogen receptor alpha in breast cancer cells and provides means and tools for modulating said mechanisms of action, thereby influencing the proliferation of estrogen-positive cells such as cancer cells. Detailed Description: FIELD OF THE INVENTION The present invention is situated in the medical field, more in particular in the field of medical diagnosis and treatment, more specifically in the diagnosis and treatment of cancers such as breast cancer, using a new diagnostic and therapeutic target peptide issued from the Estrogen Receptor alpha (ER-alpha). BACKGROUND OF THE INVENTION The Estrogen Receptor alpha (ER-alpha) has been associated with a variety of cancers, including breast cancer, endometrial cancer, cervical cancer and ovarian cancer. In breast cancer, positive ER-alpha status is associated with favorable prognostic attributes including a lower rate of cell proliferation and histologic evidence of tumor differentiation. During the first several years following diagnosis, patients having ER-alpha-positive tumors tend to have a lower recurrence rate, but this is balanced by a higher recurrence rate in subsequent years, which results in an overall modest prognostic significance. A useful aspect to having ER-alpha-positive cancer is in predicting response to hormonal therapy, both in the adjuvant setting and for advanced disease. Several therapies, including prevention and treatment, are available for ER-alpha positive cancers, although tamoxifen, a triphenylethilene derivative, is currently the most prevalent. Tamoxifen reduces proliferation of ER-alpha-positive cancer cells through an estradiol antagonist mechanism, although patients develop resistance to it. Moreover, the drug increases the risk for endometrial cancer. ER-alpha is commonly depicted as a transcription factor which, once bound to the appropriate hormone (e.g., 1713-estradiol; E2), regulates the expression of target genes. However, in view of discoveries made over the last decade, this simplistic concept must be reconsidered since the transcription of estrogen-regulated genes is actually a transient and cyclic mechanism involving successive recruitments and dissociations of a large number of corepressors and coactivators. These coregulators, which modulate ER-alpha activity to the same extent as cognate ligands, should not be viewed as “accessory proteins”, but rather as products of particular genes, historically called “master genes”, that orchestrate coherent and synchronized events. According to this view, the search for drugs able to specifically interfere with coregulator recruitment may open new therapeutic avenues for the treatment of ER-alpha-related diseases. In order to design such compounds, one must have a clear understanding of the molecular mechanisms underlying the formation of active ER-alpha oligomeric structures. In this perspective, we previously described the regulatory function of the ER-alpha P295-T311 amino-acid sequence, which harbors a binding site for calmodulin (CaM) (Gallo et al., Mol Cell Endocrinol 2007; 268:37-49), a coregulator playing a role of major importance in the ER-alpha mechanism of action. The P295-T311 sequence, located between the D-(hinge) and E-(Ligand Binding Domain; LBD) domains, appeared to be involved in both the stability and the transcriptional activity of the receptor. This short sequence, actually situated in the AF-2a (autonomous activation function) domain, can be considered as a platform for various posttranslational modifications such as phosphorylation, acetylation, SUMOylation, monoubiquitination and methylation (see Gallo et al., Mol Cell Endocrinol 2008; 291:20-26). This motif also contains the third nuclear localization signal of the receptor, as well as a proteolysis site and a binding site for CaM, a coregulator which enhances both the transactivation and the stabilization of the receptor by impeding its E6-AP-(E6-Associated Protein) mediated polyubiquitination (Li et al., J Biol Chem 2006; 281:1978-85). Surprisingly, the ER-alpha-17p peptide was shown to elicit estrogenic responses in ER-alpha-expressing breast carcinoma cells (Gallo et al., Mol Cell Endocrinol 2007; 268:37-49; Gallo et al., Mol Cell Endocrinol 2007; 268:37-49; Gallo et al., J Steroid Biochem Mol Biol 2008; 109:138-149). The mechanism by which ER-alpha-17p operates is not established as yet, although their intracellular penetration seems to be required. In this regard, it should be stressed that ER-alpha, like other nuclear hormone receptors, is subject to a constant trafficking between various intracellular compartments and targets, especially in the absence of (anti)estrogenic stimulation. Note that in this context we do not know if a particular or all forms of ER-alpha (nuclear, cytoplasmic, membrane-associated, posttranslationally modified, etc.) are implicated in the mode of action of ER-alpha-17p. Recent investigations from our laboratory have revealed that ER-alpha-17p binds to purified recombinant human ER-alpha (Gallo et al., Letters in Drug Design & Discovery 2007; 4:346-355.), most likely disrupting intramolecular interactions suspected to confer upon the receptor an inactive conformation. The mechanism underlying these observations was however not elucidated, making it impossible to use it in e.g. anti-cancer drug design. The present invention has investigated further the underlying mechanism and provides new and interesting possibilities for anti-cancer treatment based on these findings. SUMMARY OF THE INVENTION The present invention is built around the surprising observation that an endogenous polypeptide breakdown product/peptide of the ER-alpha protein can be detected in the extracellular space of breast cancer cells when treated with estradiol (E2). In addition, the inventors have established that treatment of ER-alpha-positive breast cancer cells with a synthetic peptide corresponding to this breakdown product/peptide increases their proliferation. Accordingly, sequestering said breakdown product/peptide using e.g. specific binding molecules to the endogenous polypeptide, significantly reduces the proliferation rate of said breast cancer cells in the presence of E2. The present invention thus generally provides new methods for diagnosing estrogen receptor positive (ER-alpha-positive) disorders. Possible disorders envisaged by the methods of the invention are ER-alpha-positive cancers such as breast cancer, endometrial cancer, cervical cancer or ovarian cancer, preferably breast cancer. In a specific embodiment, the present invention provides methods for diagnosing ER-alpha-related disorders such as breast cancer, endometrial cancer, cervical cancer or ovarian cancer, preferably breast cancer in a subject comprising the steps of: a) detecting in a sample of a subject under analysis, the concentration of an endogenous degradation product/peptide of the estrogen receptor-alpha (ER-alpha) protein consisting of any one of the sequences defined by SEQ ID NOs:2 to 29, or 32 to 225, wherein the fragment of SEQ ID NO:29, carries a methylated lysine at position K303, and b) comparing the obtained concentration of said peptide in the sample of the subject to a control concentration of said peptide in a healthy subject, wherein an elevated concentration of said peptide indicates the subject may be suffering from said ER-alpha-related disorder. In a specific embodiment, the degradation product/peptide to be detected is a peptide defined by SEQ ID NO:2, (i.e. K268RQRDDGEGRGEVGSAGDMRAANLWPSPLMIKRSKKNSLALSLT311) of the full-length ER-alpha protein (gene: ERS1). In an even more preferred embodiment, the peptide detected is defined by SEQ ID NO:2 and comprises one or more of the following post-translational modifications: methylation of K268, R269, K303, and/or oxidation of M286, and/or phosphorylation of S282. In a further preferred embodiment, said endogenous degradation product/peptide of the ER-alpha is P295LMIKRSKK303NSLALSLT31 carrying a methylated lysine at position 303 (SEQ ID NO:29). In preferred embodiments, the method according to the invention is used for diagnosing ER-alpha-positive cancers selected from the group consisting of: breast cancer, endometrial cancer, cervical cancer and ovarian cancer, preferably breast cancer. In preferred embodiments, the sample used in the method according to the invention is a sample of bodily fluid or tissue that is in direct contact or in close proximity to the tumour or cancer cells, i.e. samples comprising the secreted ER-alpha polypeptide of the invention in detectable quantities e.g. blood, acsites fluid, fluid surrounding tumour or cancer cells, etc. Most preferably, said sample is a serum sample of the subject. The invention further provides a composition comprising an isolated endogenous ER-alpha peptide consisting of the amino acid sequence of SEQ ID NO:2, or a fragment thereof, preferably comprising the isolated endogenous ER-alpha peptide consisting of the amino acid sequence of SEQ ID NO:2; most preferably comprising one or more of the following post-translational modifications: methylation of K268, R269, K303, and/or oxidation of M286, and/or phosphorylation of S282. The composition can comprise the endogenous ER-alpha peptide consisting of the amino acid sequence of SEQ ID NO:2, or any fragment thereof that minimally comprises the 17 amino acid sequence PLMIKRSKKNSLALSLT, in which the K303 residue can be methylated. Alternatively, composition comprises any one of the following fragments of the endogenous ER-alpha polypeptide according to the present invention, consisting of the sequence: K268RQRDDGEGRGEVGS282AGDM286RAANLWPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:2), R269QRDDGEGRGEVGS282AGDM286RAANLWPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:3), Q270RDDGEGRGEVGS282AGDM286RAANLWPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:4), R271DDGEGRGEVGS282AGDM286RAANLWPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:5), D272DGEGRGEVGS282AGDM286RAANLWPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:6), D273GEGRGEVGS282AGDM286RAANLWPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:7), G274EGRGEVGS282AGDM286RAANLWPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:8), E275GRGEVGS282AGDM286RAANLWPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:9), G276RGEVGS282AGDM286RAANLWPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:10), R277GEVGS282AGDM286RAANLWPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:11), G278EVGS282AGDM286RAANLWPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:12), E279VGS282AGDM286RAANLWPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:13), V280GS282AGDM286RAANLWPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:14), G281S282AGDM286RAANLWPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:15), S282AGDM286RAANLWPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:16), A283GDM286RAANLWPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:17), G284DM286RAANLWPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:18), D285M286RAANLWPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:19), M286RAANLWPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:20), R287AANLWPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:21), A288ANLWPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:22), A289NLWPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:23), N290LWPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:24), L291WPSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:25), W292PSPLMIKRSKK303NSLALSLT311 (SEQ ID NO:26), P293SPLMIKRSKK303NSLALSLT311 (SEQ ID NO:27), S294PLMIKRSKK303NSLALSLT311 (SEQ ID NO:28), P295LMIKRSKK303NSLALSLT311 (SEQ ID NO:29), or any one of the sequences defined by SEQ ID Nos 32 to 225, wherein in any one of the sequences listed above, one or more of the following post translational modifications can be present: methylation of K268, R269, K303, and/or oxidation of M286, and/or phosphorylation of S282. The subscripts used in said sequences refer to the positions of the corresponding residues in the full-length ER-alpha amino acid sequence. In a specific embodiment of said composition, the degradation product/peptide to be detected is a peptide defined by SEQ ID NO:2, (i.e. K268RQRDDGEGRGEVGSAGDMRAANLWPSPLMIKRSKKNSLALSLT311) of the full-length ER-alpha protein (gene: ERS1). In an even more preferred embodiment, the peptide detected is defined by SEQ ID NO:2 and comprises one or more of the following post-translational modifications: methylation of K268, R269, K303, and/or oxidation of M286, and/or phosphorylation of S282. In a further preferred embodiment of said composition, said endogenous degradation product/peptide of the ER-alpha is P295LMIKRSKK303NSLALSLT31 carrying a methylated lysine at position 303 (SEQ ID NO:29). In a further preferred embodiment, the composition comprises an antigenic fragment of said endogenous ER-alpha degradation product/peptide, as defined by any one of SEQ ID Nos 32 to 225. The composition of the present invention can be linked to a carrier molecule such as bovine serum albumine (BSA) or keyhole limpit hemocyanine (KLH), or can be comprised within a lipid composition such as, a lipid particle, a nanocapsule, a liposome, or lipid vesicle. Preferably, said composition comprises a pharmaceutical excipient. The composition according to the present invention can be used in vaccination against ER-alpha-positive cancers. The present invention thus provides for the use of the composition according to the invention for use as a vaccine and/or for use in vaccination. In a preferred embodiment, said vaccination is against human breast cancer. The composition in accordance with the invention can be for use in preparing a vaccine for preventing or treating ER-alpha-positive cancers or for use in preparing a cancer inhibitor that specifically binds to the estrogen receptor polypeptide. The invention further provides for the use of a composition in accordance with the invention in the manufacture of a medicament for use in treating ER-alpha-positive cancers, preferably breast cancer. Instead of a protein or polypeptide as such, the present invention also provides for nucleotides encoding any one of the ER-alpha degradation product polypeptides or fragments as defined herein. The invention further provides for the use of such a nucleic acid according to the invention for use in DNA-vaccination; wherein said nucleic acid is transferred into the host cell, where it expresses the polypeptide of the invention (e.g. of SEQ ID NO:2), to which an immune response is to be elicited e.g. in order to reduce cancer growth. Delivery of said nucleic acid can be done by direct administration of the DNA molecule, or can be done through a bacterial or viral expression system known in the art of gene therapy. The invention thus provides for an isolated nucleic acid that encodes any one of the peptides containing the sequence defined by SEQ ID Nos 2 to 29, or 32 to 225. In a preferred embodiment, said nucleic acid is defined by SEQ ID NO:1 and encodes the polypeptide as defined in SEQ-ID NO:2. The invention thus provides for the nucleic acids as defined herein for use in preparing a medicament or vaccine for treating ER-alpha-positive cancers or for the use of said nucleic acid in the manufacture of a medicament or vaccine for use in treating ER-alpha-positive cancers. In a preferred embodiment, said nucleic acid is in the form of RNA, mRNA, DNA, or cDNA. In addition, the invention provides for a recombinant vector that expresses a (poly)peptide as defined herein. Such a recombinant vector can also be used for gene-therapy, whereby said nucleic acid as defined herein is transferred to the host and made to express the (poly)peptide it is encoding into said host, thereby eliciting an immune response to said polypeptide in the host. Said recombinant vector can be for use in preparing a medicament or vaccine for treating cancer or can be used in the manufacture of a medicament or vaccine for use in treating cancer. Viral delivery of RNA or DNA encoding the polypeptide according to the invention for vaccination purposes is also envisaged using known methodologies. Furthermore, a recombinant host cell expressing the nucleic acid as defined herein, polypeptide as defined herein or the recombinant vector as defined herein is envisaged by the present invention, as well as its use in preparing a medicament or vaccine for treating cancer. Preferably, said host cell is a mammalian cell, e.g. a human cell, a bacterial cell, e.g. an E. coli, Salmonella, or Pseudomonas cell. The invention further provides for a method of reducing estrogen receptor activity in a cell, comprising providing to said cell an effective inhibitory amount of an inhibitor composition as defined herein. In a preferred embodiment, said cell is comprised within an animal, and said composition is administered to said animal, preferably, said cell is an animal cell, more preferably said cell is comprised within an animal that has cancer, preferably breast cancer. The invention further provides for a method of reducing proliferation of a cancer cell, comprising providing to said cancer cell a therapeutically effective amount of an inhibitor of the ER-alpha receptor as defined herein. In addition, the invention provides for a method of vaccinating a subject comprising the steps of providing to said subject a polypeptide as defined herein, a nucleic acid as defined herein, a recombinant vector as defined herein or a host cell as defined herein. The invention furthermore provides for a method of treating ER-alpha-positive cancers in a subject, comprising the steps of: (a) identifying a subject having increased estrogen receptor activity; and (b) administering to said subject a therapeutically-effective amount of the inhibitor of ER-alpha, ER-alpha-vaccine or composition according to the present invention. Preferably, said composition is formulated in a pharmaceutical excipient for administration intravenously, parenterally, orally, topically, or as an inhalant, aerosol or spray. Preferably, said subject is a human. In an alternative embodiment, the method of treating ER-alpha-positive cancers in an animal further comprises administering at least a second anticancer agent to said animal, such as cyclophosphamide, methotrexate, fluorouracil, adriamycin, tamoxifen, doxorubicin, etoposide, verapamil, podophyllotoxin, and an analog or salt thereof. The invention furthermore provides for binding molecules that specifically bind to the ER-alpha degradation product/peptide as defined herein, preferably to the polypeptide consisting of the amino acid sequence of SEQ ID NO:2. Preferably, said binding molecule specifically binds to the polypeptide as defined in SEQ ID NO:2, comprising one or more of the following post-translational modifications: methylation of K268, R269, K303, and/or oxidation of M286, and/or phosphorylation of S282. In a further embodiment, said antibody binds to a fragment of the endogenous ER-alpha degradation product/peptide as defined herein, i.e. to any one of the (poly)peptides consisting of the sequence defined by SEQ ID Nos 1 to 29, or 32 to 225. Examples of binding molecules envisaged hereby are antibodies, monoclonal- or polyclonal antibodies, nanobodies, affybodies, antibody fragments, aptamers, photoaptamers, oligonucleotides, lipocalins, specifically interacting small molecules, Molecular Imprinting Polymers (MIPs), DARPins, ankyrins, specifically interacting proteins, peptidomimetics, biomimetics or peptides, and other molecules that specifically bind to said polypeptide. Both monoclonal, polyclonal or single chain antibodies or fragments thereof that bind one of the biomarkers of the present invention are useful in the methods and kits of the present invention. Such binding molecules can also act as inhibitors of the ER-alpha function. The invention thus also provides a pharmaceutical composition comprising an inhibitor of ER-alpha for treating cancer or for use in the manufacturing of a medicament for treating cancer. Preferably, said inhibitor is a binding molecule as defined herein, e.g. specifically binding to the endogenous ER-alpha degradation product/peptide of the invention as defined by SEQ ID NO:2, optionally specifically binding to the polypeptide of the invention as defined by SEQ ID NO:2 comprising one or more of the following post-translational modifications: methylation of K268, R269, K303, and/or oxidation of M286, and/or phosphorylation of S282. In a preferred embodiment, said binding molecule is an antibody or fragment thereof. In a preferred embodiment, said binding molecule binds specifically to a fragment of the endogenous ER-alpha degradation product/peptide as defined herein, i.e. to any one of the (poly)peptides consisting of the sequence defined by SEQ ID Nos 1 to 29, or 32 to 225. The antibody according to the present invention can alternatively be attached to a detectable label. The inhibitors or binding molecules as indicated above can also be used independently, i.e. not in a pharmaceutical composition, for example for the detection of said polypeptide of the invention. The invention thus provides for inhibitors or binding molecules of the ER-alpha receptor protein as such, defined by their ability to bind specifically to the endogenous ER-alpha degradation product/peptide as defined herein, preferably defined by SEQ ID NO:2, optionally specifically binding to the polypeptide of the invention as defined by SEQ ID NO:2 comprising one or more of the following post-translational modifications: methylation of K268, R269, K303, and/or oxidation of M286, and/or phosphorylation of S282. In a preferred embodiment, said binding molecule is an antibody or fragment thereof. In a preferred embodiment, said binding molecule binds specifically to a fragment of the endogenous ER-alpha degradation product/peptide as defined herein, i.e. to any one of the (poly)peptides consisting of the sequence defined by SEQ ID Nos 1 to 29, or 32 to 225. In particular, the invention thus provides the following points: 1. A method for diagnosing estrogen receptor alpha positive cancer in a subject comprising the steps of: a) detecting in a sample of a subject under analysis, the concentration of an endogenous degradation peptide of the estrogen receptor-alpha (ER-alpha) consisting of any one of the sequences defined by SEQ ID NOs:2 to 29, or 32 to 225, wherein the fragment of SEQ ID NO:29, carries a methylated lysine at position K303, and b) comparing the obtained concentration of said peptide in the sample of the subject to a control concentration of said peptide in a healthy subject, wherein an elevated concentration of said peptide indicates the subject may be suffering of an ER-alpha-positive cancer. 2. The method according to point 1, wherein said endogenous degradation peptide of the ER-alpha is P295LMIKRSKK303NSLALSLT31 carrying a methylated lysine at position 303 (SEQ ID NO:29). 3. The method according to point 1 or 2, wherein said endogenous degradation peptide consists of the sequence of SEQ ID NO:2. 4. The method according to any one of points 1 to 3, wherein said endogenous degradation peptide carriers one or more of the following post-translational modifications: methylation of K268, R269, K303, and/or oxidation of M286, and/or phosphorylation of S282. 5. The method according to any one of points 1 to 4, wherein said ER-alpha-positive cancer is preferably selected from the group consisting of: breast cancer, endometrial cancer, cervical cancer and ovarian cancer, most preferably human breast cancer. 6. The method according to any one of points 1 to 5, wherein the sample is preferably selected from the consisting of: whole blood, plasma, serum, nipple aspirate, ductal lavage, tumour exudates, tumour cavity fluid, pleural effusion, acsites fluid, fluid surrounding tumour or cancer cells, lymph, any other bodily fluid in close contact with the tumour or cancer. 7. An isolated estrogen receptor-alpha (ER-alpha) polypeptide consisting of any one of the sequences defined by SEQ ID NOs:2 to 29, or 32 to 225, wherein the fragment of SEQ ID NO:29, carries a methylated lysine at position K303, 8. The isolated polypeptide according to point 7, carrying one or more of the following post-translational modifications: methylation of K268, R269, K303, and/or oxidation of M286, and/or phosphorylation of S282. 9. A composition comprising the isolated ER-alpha polypeptide according to point 7 or 8, wherein said peptide is linked to a carrier molecule such as bovine serum albumine or keyhole limpet hemocyanin, or comprised within a lipid composition such as, a lipid particle, a nanocapsule, a liposome, or lipid vesicle, optionally further comprising a pharmaceutical excipient. 10. The composition according to point 9, additionally comprising an adjuvant. 11. The polypeptide according to point 7 or 8 or the composition according to point 9 or 10, for use in treatment of, or vaccination against ER-alpha-positive cancers, preferably breast cancer, endometrial cancer, cervical cancer and ovarian cancer, most preferably human breast cancer. 12. A nucleic acid molecule encoding the polypeptide according to point 7. 13. The nucleic acid according to point 12, consisting of a polynucleotide sequence having at least 90% identity to SEQ ID NO.1, more preferably consisting of the polynucleotide sequence of SEQ ID NO:1. 14. The nucleic acid molecule according to point 12 or 13, for use in treatment of, or vaccination against ER-alpha-positive cancers, preferably breast cancer, endometrial cancer, cervical cancer and ovarian cancer, most preferably human breast cancer. 15. A recombinant vector that expresses a peptide according to point 7, or comprises the nucleic acid molecule according to point 12 or 13. 16. The recombinant vector according to point 15, for treatment of, or vaccinating against ER-alpha-positive cancers, preferably breast cancer, endometrial cancer, cervical cancer and ovarian cancer, most preferably human breast cancer. 17. A host cell comprising a polypeptide according to point 7 or 8, the composition according to point 9 or 10, the nucleic acid molecule according to point 12 or 13, or the recombinant vector according to point 14, wherein said cell preferably is a mammalian cell, e.g. a human cell, a yeast cell, a bacterial cell, e.g. an E. coli, Salmonella, or Pseudomonas cell. 18. The host cell according to point 17, for treatment of, or vaccinating against ER-alpha-related diseases, preferably breast cancer, endometrial cancer, cervical cancer and ovarian cancer, most preferably human breast cancer. 19. A purified binding molecule that specifically binds to the polypeptide according to point 7 or 8, preferably antibodies, monoclonal- or polyclonal antibodies, nanobodies, affybodies, antibody fragments, aptamers, photoaptamers, oligonucleotides, lipocalins, specifically interacting small molecules, Molecular Imprinting Polymers (MIPs), DARPins, ankyrins, specifically interacting proteins, peptidomimetics, biomimetics or peptides, and other molecules that specifically bind to said polypeptide. 20. An immunodetection kit comprising: a) a binding molecule according to point 19, b) a reference value of the amount of corresponding peptide to which said binding molecule specifically binds, in a healthy subject and c) instructions to compare the amounts of said peptide in a sample of the subject under investigation and in a sample of a healthy subject in order to conclude whether said subject has ER-alpha positive cancer or not. 21. The use of the polypeptide according to point 7 or 8, as a biomarker for diagnosing, predicting, prognosticating and/or monitoring an ER-alpha positive cancer, preferably breast cancer, endometrial cancer, cervical cancer and ovarian cancer, most preferably human breast cancer. 22. A method of treating a subject having ER-alpha-positive cancer, comprising administering to said subject a therapeutically effective amount of the peptide according to point 7 or 8, or the composition according to point 9 or 10. 23. A method for vaccinating a subject against the occurrence of ER-alpha-positive cancer, comprising administering to said subject a therapeutically effective amount of the peptide according to point 7 or 8, or the composition according to point 9 or 10. 24. A method of treating ER-alpha-positive cancers, preferably breast cancer, endometrial cancer, cervical cancer and ovarian cancer, most preferably human breast cancer, comprising the steps of administering the polypeptide according to point 7 or 8, the composition according to point 9 or 10, the nucleic acid molecule according to point 12 or 13, the recombinant vector according to point 15, or the host cell according to point 17, to a subject in need thereof, optionally combined with other therapeutic agents that can be beneficial or synergistic to the treatment of said subject. 25. A method of vaccinating a subject in need thereof against developing ER-alpha-positive cancers, preferably breast cancer, endometrial cancer, cervical cancer and ovarian cancer, most preferably human breast cancer, comprising the steps of administering the polypeptide according to point 7 or 8 or the composition according to point 9 or 10, the nucleic acid molecule according to point 12 or 13, the recombinant vector according to point 15, or the host cell according to point 17, to said subject, optionally combined with other therapeutic agents or with adjuvants that can be beneficial or synergistic to the vaccination of said subject. 26. The use of the polypeptide according to point 7 or 8 or the composition according to point 9 or 10, the nucleic acid molecule according to point 12 or 13, the recombinant vector according to point 15, or the host cell according to point 17, for the manufacturing of a medicament for treating ER-alpha-positive cancers, preferably breast cancer, endometrial cancer, cervical cancer and ovarian cancer, most preferably human breast cancer in a subject. 27. The use of the polypeptide according to point 7 or 8 or the composition according to point 9 or 10, the nucleic acid molecule according to point 12 or 13, the recombinant vector according to point 15, or the host cell according to point 17, for the manufacturing of a medicament for vaccinating a subject against developing ER-alpha-positive cancers, preferably breast cancer, endometrial cancer, cervical cancer and ovarian cancer, most preferably human breast cancer. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1: MS/MS Spectrum of an endogenous peptide extracted form conditioned medium of E2-stimulated MCF-7 cells. This peptide encompasses the amino acid sequence K268-T311 and, thus, the sequence of the ER-alpha-17p (precursor charged 6×; m/z=823,26). FIG. 2: Sequence and post-translational modifications of the detected peptide (SEQ ID NO:2) and the corresponding nucleic acid sequence (SEQ ID NO:1) encoding said peptide. FIG. 3: Immunoprecipitation of the endogenous peptide. The peptide was extracted from conditioned medium of MCF-7 cells treated or not (control) with estradiol (10−8M), diethylstibestrol (10−8M), 4-OHTamoxifen (10−7M) or Fulvestrant (10−7M). FIG. 4: Cell growth in the presence or absence of a synthetic peptide corresponding to the ER-alpha breakdown product/peptide (SEQ ID NO:2). MCF-7 cells were incubated with or without (control) ER-alpha-17p or SEQ ID NO:2 peptide both at 10−5M for 72 h. Growth was assessed by crystal violet staining. FIG. 5: Cell growth in the presence or absence of E2 at 10−11 and10−12M with or without an antibody (dilution 1/100) raised against the C-terminal part of the ER-alpha breakdown product/peptide (SEQ ID NO:2) for 72 h. Growth was assessed by crystal violet staining. FIG. 6: Transcriptional activity of ER-alpha. MVLN cells (MCF-7 stably transfected with an ERE-driven luciferase reporter gene; Pons et al., Biotechniques 1990; 9:450-459) in the presence or absence (control) of E2 at 10−10 M or ER-alpha-17p or SEQ ID NO:2 peptide both at 10−5M for 6 h in serum free condition. FIG. 7: cDNA coding sequence of ER-alpha isoform 1 (Genbank Acc. No. NM—000125 (SEQ ID NO:3)). The bold sequence corresponds to SEQ ID NO:1, encoding the peptide of SEQ ID NO:2. FIG. 8: Amino acid sequence of ER-alpha isoform 1 (Genbank Acc. No. NP—000116 (SEQ ID NO: 4)), indicating the identified polypeptide according to the invention (SEQ ID NO:2). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As used herein, the terms “a”, “an”, and “the” include both singular and plural referents unless the context clearly dictates otherwise. The terms “comprising”, “comprises” and “comprised of” as used herein are synonymous with “including”, “includes” or “containing”, “contains”, and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within the respective ranges, as well as the recited endpoints. The term “about” as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of and from the specified value, in particular variations of +/−10% or less, preferably +/−5% or less, more preferably +/−1% or less, and still more preferably +/−0.1% or less of and from the specified value, insofar such variations are appropriate to perform in the disclosed invention. It is to be understood that the value to which the modifier “about” refers is itself also specifically, and preferably, disclosed. All documents cited in the present specification are hereby incorporated by reference in their entirety. Unless otherwise specified, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions may be included to better appreciate the teaching of the present invention. The terms “predicting” or “prediction”, “diagnosing” or “diagnosis” and “prognosticating” or “prognosis” are commonplace and well-understood in medical and clinical practice. By way of example only and without limitation, “predicting” or “prediction” generally refer to an advance declaration, indication or foretelling of a disease or condition in a subject not (yet) having said disease or condition. For example, a prediction of a disease or condition in a subject may indicate a probability, chance or risk that the subject will develop said disease or condition, for example within a certain time period or by a certain age. Said probability, chance or risk may be indicated inter alia as an absolute value, range or statistics, or may be indicated relative to a suitable control subject or subject population (such as, e.g., relative to a general, normal or healthy subject or subject population). Hence, the probability, chance or risk that a subject will develop a disease or condition may be advantageously indicated as increased or decreased, or as fold-increased or fold-decreased relative to a suitable control subject or subject population. The terms “diagnosing” or “diagnosis” generally refer to the process or act of recognising, deciding on or concluding on a disease or condition in a subject on the basis of symptoms and signs and/or from results of various diagnostic procedures (such as, for example, from knowing the presence, absence and/or quantity of one or more biomarkers characteristic of the diagnosed disease or condition). The terms “prognosticating” or “prognosis” generally refer to an anticipation on the progression of a disease or condition and the prospect (e.g., the probability, duration, and/or extent) of recovery. The term “subject” or “patient” as used herein typically denotes humans, but may also encompass reference to non-human animals, preferably warm-blooded animals, more preferably mammals, such as, e.g., non-human primates, rodents, canines, felines, equines, ovines, porcines, and the like. The terms “sample” or “biological sample” as used herein include any biological specimen obtained from a subject. Samples may include, without limitation, whole blood, plasma, serum, red blood cells, white blood cells (e.g., peripheral blood mononuclear cells), saliva, urine, stool (i.e., faeces), tears, sweat, sebum, nipple aspirate, ductal lavage, tumour exudates, tumour cavity fluid, pleural effusion, synovial fluid, cerebrospinal fluid, lymph, fine needle aspirate, amniotic fluid, any other bodily fluid, cell lysates, cellular secretion products, inflammation fluid, semen and vaginal secretions. Preferred samples may include ones comprising the secreted ER-alpha polypeptide of the invention in detectable quantities e.g. blood, acsites fluid, fluid surrounding tumour or cancer cells, etc. In preferred embodiments, the sample may be whole blood or a fractional component thereof such as, e.g., plasma, serum, or a cell pellet. Preferably the sample is readily obtainable by minimally invasive methods. Samples may alternatively also include tissue samples and biopsies, tissue homogenates and the like. The terms “quantity”, “amount” and “level” are synonymous and generally well-understood in the art. The terms as used herein may particularly refer to an absolute quantification of a molecule or an analyte in a sample, or to a relative quantification of a molecule or analyte in a sample, i.e., relative to another value such as relative to a reference value as taught herein. An absolute quantity of a molecule or analyte in a sample may be advantageously expressed as weight or as molar amount, or more commonly as a concentration, e.g., weight per volume or mol per volume. A relative quantity of a molecule or analyte in a sample may be advantageously expressed as an increase or decrease or as a fold-increase or fold-decrease relative to said another value, such as relative to a reference value as taught herein. Performing a relative comparison between first and second parameters (e.g., first and second quantities) may but need not require to first determine the absolute values of said first and second parameters. For example, a measurement method can produce quantifiable readouts (such as, e.g., signal intensities) for said first and second parameters, wherein said readouts are a function of the value of said parameters, and wherein said readouts can be directly compared to produce a relative value for the first parameter vs. the second parameter, without the actual need to first convert the readouts to absolute values of the respective parameters. Also provided are binding molecule capable of specifically binding to the ER-alpha polypeptide as taught herein preferably defined by SEQ ID NO:2 or to its specific forms comprising one or more of the following post-translational modifications: methylation of K268, R269, K303, and/or oxidation of M286, and/or phosphorylation of S282. Such binding molecules may include inter alia an antibody, aptamer, photoaptamer, protein, peptide, peptidomimetic or a small molecule. The term “specifically bind” as used throughout this specification means that an agent (denoted herein also as “specific binding molecule” or “specific binding molecule”) binds to one or more desired molecules or analytes, such as to one or more proteins, polypeptides or peptides of interest or fragments thereof substantially to the exclusion of other molecules which are random or unrelated, and optionally substantially to the exclusion of other molecules that are structurally related. The term “specifically bind” does not necessarily require that a molecule binds exclusively to its intended target(s). For example, a molecule may be said to specifically bind to the target polypeptide(s), peptide(s) and/or fragment(s) thereof of the invention or their post-translationally modified forms, if its affinity for such intended target(s) under the conditions of binding is at least about 2-fold greater, preferably at least about 5-fold greater, more preferably at least about 10-fold greater, yet more preferably at least about 25-fold greater, still more preferably at least about 50-fold greater, and even more preferably at least about 100-fold or more greater, than its affinity for a non-target polypeptide or molecule. Preferably, the binding molecule may bind to its intended target(s) with affinity constant (KA) of such binding KA≧1×106 M−1, more preferably KA≧1×107 M−1, yet more preferably KA≧1×108 M−1, even more preferably KA≧1×109 M−1, and still more preferably KA≧1×1010 M−1 or KA≧1×1011 M−1, wherein KA=[SBM_T]/[SBM][T], SBA denotes the specific-binding molecule, T denotes the intended target. Determination of KA can be carried out by methods known in the art, such as for example, using equilibrium dialysis and Scatchard plot analysis. Specific-binding molecules as used throughout this specification may include inter alia an antibody, aptamer, photoaptamer, protein, peptide, peptidomimetic or a small molecule. As used herein, the term “antibody” is used in its broadest sense and generally refers to any immunologic binding molecule that is specifically binding to a target molecule such as the ER-alpha polypeptide as taught herein or one or more of its post-translationally modified forms as defined herein. The term specifically encompasses intact monoclonal antibodies, polyclonal antibodies, multivalent (e.g., 2-, 3- or more-valent) and/or multi-specific antibodies (e.g., bi- or more-specific antibodies) formed from at least two intact antibodies, and antibody fragments insofar they exhibit the desired biological activity (particularly, ability to specifically bind an antigen of interest), as well as multivalent and/or multi-specific composites of such fragments. The term “antibody” is not only inclusive of antibodies generated by methods comprising immunisation, but also includes any polypeptide, e.g., a recombinantly expressed polypeptide, which is made to encompass at least one complementarity-determining region (CDR) capable of specifically binding to an epitope on an antigen of interest. Hence, the term applies to such molecules regardless whether they are produced in vitro or in vivo. In an embodiment, an antibody may be any of IgA, IgD, IgE, IgG and IgM classes, and preferably IgG class antibody. For therapeutic purposes, IgG antibodies are preferred, especially of the IgG2 or IgG4 type, which induce a lower autoimmune response in the subject. In an embodiment, the antibody may be a polyclonal antibody, e.g., an antiserum or immunoglobulins purified there from (e.g., affinity-purified). In another preferred embodiment, the antibody may be a monoclonal antibody or a mixture of monoclonal antibodies. Monoclonal antibodies can target a particular antigen or a particular epitope within an antigen with greater selectivity and reproducibility. By means of example and not limitation, monoclonal antibodies may be made by the hybridoma method first described by Kohler et al. 1975 (Nature 256: 495), or may be made by recombinant DNA methods (e.g., as in U.S. Pat. No. 4,816,567). Monoclonal antibodies may also be isolated from phage antibody libraries using techniques as described by Clackson et al. 1991 (Nature 352: 624-628) and Marks et al. 1991 (J Mol Biol 222: 581-597), for example. In further embodiments, the antibody binding molecules may be antibody fragments. “Antibody fragments” comprise a portion of an intact antibody, comprising the antigen-binding or variable region thereof. Examples of antibody fragments include Fab, Fab′, F(ab′)2, Fv and scFv fragments; diabodies; linear antibodies; single-chain antibody molecules; and multivalent and/or multispecific antibodies formed from antibody fragment(s), e.g., dibodies, tribodies, and multibodies. The above designations Fab, Fab′, F(ab′)2, Fv, scFv etc. are intended to have their art-established meaning. The term antibody includes antibodies originating from or comprising one or more portions derived from any animal species, preferably vertebrate species, including, e.g., birds and mammals. Without limitation, the antibodies may be chicken, turkey, goose, duck, guinea fowl, quail or pheasant. Also without limitation, the antibodies may be human, murine (e.g., mouse, rat, etc.), donkey, rabbit, goat, sheep, guinea pig, camel (e.g., Camelus bactrianus and Camelus dromaderius), llama (e.g., Lama paccos, Lama glama or Lama vicugna) or horse. A skilled person will understand that an antibody can include one or more amino acid deletions, additions and/or substitutions (e.g., conservative substitutions), insofar such alterations preserve its binding of the respective antigen. An antibody may also include one or more native or artificial modifications of its constituent amino acid residues (e.g., glycosylation, etc.). Methods of producing polyclonal and monoclonal antibodies as well as fragments thereof are well known in the art, as are methods to produce recombinant antibodies or fragments thereof (see for example, Harlow and Lane, “Antibodies: A Laboratory Manual”, Cold Spring Harbour Laboratory, New York, 1988; Harlow and Lane, “Using Antibodies: A Laboratory Manual”, Cold Spring Harbour Laboratory, New York, 1999, ISBN 0879695447; “Monoclonal Antibodies: A Manual of Techniques”, by Zola, ed., CRC Press 1987, ISBN 0849364760; “Monoclonal Antibodies: A Practical Approach”, by Dean & Shepherd, eds., Oxford University Press 2000, ISBN 0199637229; Methods in Molecular Biology, vol. 248: “Antibody Engineering: Methods and Protocols”, Lo, ed., Humana Press 2004, ISBN 1588290921). The term “aptamer” refers to single-stranded or double-stranded oligo-DNA, oligo-RNA or oligo-DNA/RNA or any analogue thereof, that can specifically bind to a target molecule such as the ER-alpha polypeptide as taught herein or one or more of its post-translationally modified forms as defined herein. Advantageously, aptamers can display fairly high specificity and affinity (e.g., KA in the order 1×109 M−1) for their targets. Aptamer production is described inter alia in U.S. Pat. No. 5,270,163; Ellington & Szostak 1990 (Nature 346: 818-822); Tuerk & Gold 1990 (Science 249: 505-510); or “The Aptamer Handbook: Functional Oligonucleotides and Their Applications”, by Klussmann, ed., Wiley-VCH 2006, ISBN +1-832-498-8460, incorporated by reference herein. The term “photoaptamer” refers to an aptamer that contains one or more photoreactive functional groups that can covalently bind to or crosslink with a target molecule. The term “peptidomimetic” refers to a non-peptide agent that is a topological analogue of a corresponding peptide. Methods of rationally designing peptidomimetics of peptides are known in the art. For example, the rational design of three peptidomimetics based on the sulphated 8-mer peptide CCK26-33, and of two peptidomimetics based on the 11-mer peptide Substance P, and related peptidomimetic design principles, are described in Horwell 1995 (Trends Biotechnol 13: 132-134). The term “small molecule” refers to compounds, preferably organic compounds, with a size comparable to those organic molecules generally used in pharmaceuticals. The term excludes biological macromolecules (e.g., proteins, nucleic acids, etc.). Preferred small organic molecules range in size up to about 5000 Da, e.g., up to about 4000, preferably up to 3000 Da, more preferably up to 2000 Da, even more preferably up to about 1000 Da, e.g., up to about 900, 800, 700, 600 or up to about 500 Da. Preferred small molecules are those that specifically bind to a target molecule such as the ER-alpha polypeptide as taught herein or one or more of its post-translationally modified forms as defined herein. Also provided are methods for preparing specific antibodies directed to the peptide of the invention (SEQ ID NO:2), by immunising animals, e.g., non-human animals such as laboratory or farm, animals using (i.e., using as the immunising antigen) the ER-alpha polypeptide as taught herein (e.g. SEQ ID NO:2) or one or more of its post-translationally modified forms as defined herein (cf. FIG. 2), optionally attached to a presenting carrier. Alternatively DNA or RNA immunisation can be applied using the nucleotide defined herein (e.g. SEQ ID NO:1). Immunisation and preparation of antibody reagents from immune sera is well-known per se. The animals to be immunised may include any animal species, preferably warm-blooded species, more preferably vertebrate species, including, e.g., birds and mammals. Without limitation, the antibodies may be chicken, turkey, goose, duck, guinea fowl, quail or pheasant. Also without limitation, the antibodies may be human, murine (e.g., mouse, rat, etc.), donkey, rabbit, goat, sheep, guinea pig, camel, llama or horse. The term “presenting carrier” or “carrier” generally denotes an immunogenic molecule which, when bound to a second molecule, augments immune responses to the latter, usually through the provision of additional T cell epitopes. The presenting carrier may be a (poly)peptidic structure or a non-peptidic structure, such as inter alia glycans, polyethylene glycols, peptide mimetics, synthetic polymers, etc. Exemplary non-limiting carriers include human Hepatitis B virus core protein, multiple C3d domains, tetanus toxin fragment C or yeast Ty particles. Immune sera obtained or obtainable by immunisation as taught herein may be particularly useful for generating antibody reagents that specifically bind to the ER-alpha polypeptide as taught herein or one or more of its post-translationally modified forms as defined herein. The invention also teaches a method for selecting specific-binding molecules which bind specifically to the ER-alpha polypeptide as taught herein or one or more of its post-translationally modified forms as defined herein. Conveniently, such methods may be based on subtracting or removing binding molecules which cross-react or cross-bind the non-desired molecules. Such subtraction may be readily performed as known in the art by a variety of affinity separation methods, such as affinity chromatography, affinity solid phase extraction, affinity magnetic extraction, etc. Any existing, available or conventional separation, detection and quantification methods can be used herein to measure the presence or absence (e.g., readout being present vs. absent; or detectable amount vs. undetectable amount) and/or quantity (e.g., readout being an absolute or relative quantity, such as, for example, absolute or relative concentration) of the ER-alpha polypeptide as taught herein or one or more of its post-translationally modified forms as defined herein. For example, such methods may include immunoassay methods, mass spectrometry analysis methods, or chromatography methods, or combinations thereof. The term “immunoassay” generally refers to methods known as such for detecting one or more molecules or analytes of interest in a sample, wherein specificity of an immunoassay for the molecule(s) or analyte(s) of interest is conferred by specific binding between a specific-binding molecule, commonly an antibody, and the molecule(s) or analyte(s) of interest. Immunoassay technologies include without limitation direct ELISA (enzyme-linked immunosorbent assay), indirect ELISA, sandwich ELISA, competitive ELISA, multiplex ELISA, radioimmunoassay (RIA), ELISPOT technologies, FPIA (Fluorescence Polarization Immunoassay) and other similar techniques known in the art. Principles of these immunoassay methods are known in the art, for example John R. Crowther, “The ELISA Guidebook”, 1st ed., Humana Press 2000, ISBN 0896037282. By means of further explanation and not limitation, direct ELISA employs a labelled primary antibody to bind to and thereby quantify target antigen in a sample immobilised on a solid support such as a microwell plate. Indirect ELISA uses a non-labelled primary antibody which binds to the target antigen and a secondary labelled antibody that recognises and allows to quantify the antigen-bound primary antibody. In sandwich ELISA the target antigen is captured from a sample using an immobilised ‘capture’ antibody which binds to one antigenic site within the antigen, and subsequent to removal of non-bound analytes the so-captured antigen is detected using a ‘detection’ antibody which binds to another antigenic site within said antigen, where the detection antibody may be directly labelled or indirectly detectable as above. Competitive ELISA uses a labelled ‘competitor’ that may either be the primary antibody or the target antigen. In an example, non-labelled immobilised primary antibody is incubated with a sample, this reaction is allowed to reach equilibrium, and then labelled target antigen is added. The latter will bind to the primary antibody wherever its binding sites are not yet occupied by non-labelled target antigen from the sample. Thus, the detected amount of bound labelled antigen inversely correlates with the amount of non-labelled antigen in the sample. Multiplex ELISA allows simultaneous detection of two or more analytes within a single compartment (e.g., microplate well) usually at a plurality of array addresses (see, for example, Nielsen & Geierstanger 2004. J Immunol Methods 290: 107-20 and Ling et al. 2007. Expert Rev Mol Diagn 7: 87-98 for further guidance). As appreciated, labelling in ELISA technologies is usually by enzyme (such as, e.g., horse-radish peroxidase) conjugation and the end-point is typically colorimetric, chemiluminescent or fluorescent. Radioimmunoassay (RIA) is a competition-based technique and involves mixing known quantities of radioactively-labelled (e.g., 125I- or 131I-labelled) target antigen with antibody to said antigen, then adding non-labelled or ‘cold’ antigen from a sample and measuring the amount of labelled antigen displaced (see, e.g., “An Introduction to Radioimmunoassay and Related Techniques”, by Chard T, ed., Elsevier Science 1995, ISBN 0444821198 for guidance). Further, mass spectrometry methods are suitable for measuring biomarkers. Generally, any mass spectrometric (MS) techniques that can obtain precise information on the mass of peptides, and preferably also on fragmentation and/or (partial) amino acid sequence of selected peptides (e.g., in tandem mass spectrometry, MS/MS; or in post source decay, TOF MS), are useful herein. Suitable peptide MS and MS/MS techniques and systems are well-known per se (see, e.g., Methods in Molecular Biology, vol. 146: “Mass Spectrometry of Proteins and Peptides”, by Chapman, ed., Humana Press 2000, ISBN 089603609x; Biemann 1990. Methods Enzymol 193: 455-79; or Methods in Enzymology, vol. 402: “Biological Mass Spectrometry”, by Burlingame, ed., Academic Press 2005, ISBN 9780121828073) and may be used herein. MS arrangements, instruments and systems suitable for biomarker peptide analysis may include, without limitation, matrix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF) MS; MALDI-TOF post-source-decay (PSD); MALDI-TOF/TOF; surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF) MS; electrospray ionization mass spectrometry (ESI-MS); ESI-MS/MS; ESI-MS/(MS)n (n is an integer greater than zero); ESI 3D or linear (2D) ion trap MS; ESI triple quadrupole MS; ESI quadrupole orthogonal TOF (Q-TOF); ESI Fourier transform MS systems; desorption/ionization on silicon (DIOS); secondary ion mass spectrometry (SIMS); atmospheric pressure chemical ionization mass spectrometry (APCI-MS); APCI-MS/MS; APCI-(MS)n; atmospheric pressure photoionization mass spectrometry (APPI-MS); APPI-MS/MS; and APPI-(MS)n. Peptide ion fragmentation in tandem MS (MS/MS) arrangements may be achieved using manners established in the art, such as, e.g., collision induced dissociation (CID). In an embodiment, detection and quantification of biomarkers by mass spectrometry may involve multiple reaction monitoring (MRM), such as described among others by Kuhn et al. 2004 (Proteomics 4: 1175-86). In an embodiment, MS peptide analysis methods may be advantageously combined with upstream peptide or protein separation or fractionation methods, such as for example with the chromatographic and other methods described herein below. Chromatography can also be used for measuring biomarkers. As used herein, the term “chromatography” encompasses methods for separating chemical substances, referred to as such and vastly available in the art. In a preferred
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