the peritoneum has the structure and functions of an organ that is organized for the protection of the integrity of other abdominal organs and viscera . the surface epithelium of the serous membrane of the peritoneum and serosa , is attached to a basement membrane lying on a stroma of variable thickness , and is comprised of collagen - based matrix , blood vessels , lymphatics , nerve fibers , and , in the normal state , rare hematogenous cells . the structural and functional configuration of the peritoneum allows for an important homeostatic role through rapid mobilization of inflammatory mechanisms that can efficiently localize an injury or infection . the peritoneal surface layer has spaces or stomata between the surface mesothelial cells that could readily allow transfer of molecules or possibly cells between the stroma and the peritoneal cavity , or vice versa . immunohistochemically documented structures in the submesothelial layer include type i and iii collagen , fibronectin , elastin , and laminin at the basement membrane stromal interface and glycosaminoglycans . epithelial inclusions , referred to as endosalpingosis , can occur , though its cause is unknown . ultrastructurally , both tight junctions and intercellular spaces are present . the presence of these junctions can affect the transfer of particles or cells . molecules may transit either across or between the cells to the stromal compartment and vice versa . peritoneal and serosal seeding is a frequent occurrence in eoc , but there is little known about the role of the multi - structured peritoneum in contributing to invasion , metastasis , and tumor proliferation . it is possible , if not probable , that critical alterations in the peritoneum surface and stroma precede either lymphatic or hematogenous spread to distant sites . in eoc patients , there may be substantial alterations to the peritoneum both at the macroscopic and submacroscopic levels . such alterations may include thickening of the surface membrane with or without malignant ascites formation and overtly enhanced vascularity . in certain patients , the peritoneum may have a florid appearance of peritonitis with edema , enhanced vascularity , and soft adhesions . at the microscopic level , there may be multilayering of the surface epithelium ( hyperplasia ) and an inflammatory infiltrate comprised of different leukocyte populations . retroperitoneal fibrosis can be extensive and can interfere mechanically with anatomic structures in extraperitoneal locations , including ureters , lymphatics , and the bowel in different locations . it would appear that a reorganization of the collagen - based matrix associated with the malignant process in eoc patients might accompany an inflammatory cell reaction . this could be similar to the situation in the peritoneum of renal fibrosis , which results in hyperplasia of the surface layer and extensive macrophage infiltrates into the stroma . since the peritoneal and serosal membranes lie in proximity to the primary tumor or its metastases , the question could be asked whether soluble products of tumor masses and nodules might transfer to the normal surface mesothelial cells and penetrate the subjacent stromal tissues . molecules such as cytokines or chemokines released from the tumor into the peritoneal cavity could possibly prime these tissues for tumor spread , proliferation , and metastasis . the peritoneum can easily permit transperitoneal passage of molecules , even up to the size of albumin , and , depending on their adherence and reactivity with stromal compartment structures , might either transfer to the capillary bed or accumulate in the subperitoneal compartment , with later entry to the lymphatics . the dynamics of molecule transfer across the peritoneum as it applies to intraperitoneal therapy pharmacology and pharmacodynamics are reviewed elsewhere . peritoneal membrane and stromal structures exhibiting adherence properties for such molecules or cells , however , might retard their removal from this site , contributing to a sensitizing effect on the peritoneum . there is substantial data to support the presence of immune cell infiltration in eoc and its microenvironment . in earlier studies , we had shown that t cells comprised about 70% of mononuclear leukocytes in solid eoc tumors , and results from a number of experiments by us and by others suggested that the presence of these t cells could be associated with an antigen - driven immune response [ 12 - 17 ] . this effect is supported by the presence of clonally expanded t cell transcripts in ovarian til . notwithstanding these findings , we   and others   have found little evidence for the presence of an active ongoing adaptive immunity in vivo . this is supported by the absence of ifn transcripts in solid tumors and their infrequent detection in ascitic t cells . others have also reported absent cd3 tcr on til , and absent or low levels of ifn protein detected in ascites of eoc . it is possible that cloned t cells in the tumor environment could represent tolerized cells , though antitumor activity can be generated ex vivo when these t cells are exposed to appropriate activation stimuli . the presence of regulatory t cells , and certain macrophages , which are producers of il6 , il10 , and tgf could favor an immunosuppressive environment and may contribute to tumor progression and metastases . the role of il10 remains to be elucidated as , depending on the status of the tumor , this cytokine can either enhance or suppress immune responses . large numbers of monocyte / macrophages ( moma ) are also present in ascitic fluid where they may comprise 50% or more of the mononuclear leukocyte population , whereas the proportion of t - lymphocytes is usually below 40% . in recent preliminary studies , we have found that pelvic peritoneal biopsies from advanced stage eoc patients , even in the absence of tumor involvement of the specimens , also has a high proportion of mo / ma . the mo / ma in eoc comprise several subsets with the notable presence of cd14+dr- and cd14+dr+ cd16 + cells . the differentiation potential and functional capacity of these mo / ma in cancer patients is largely undetermined but clearly there are differences in the phenotypic characteristics between normal and eoc patients . inflammatory infiltrates have long been observed in human cancer tissues , but their significance in the non - lymphomatous solid tumors has largely been ignored by pathologists and clinicians . there is increasing recognition that infiltrating immune cells may contribute to either enhancement of immunity or tumor growth and progression . both mo / ma and t cells may have this dual role , and it remains a challenge to steer the activity of these populations toward an effective antitumor response in vivo . we have recently employed a custom - made standardized cdna microarray that utilizes probes for 16,500 genes to conduct a pilot study on the peritoneum of patients with eoc . biopsies were obtained at the time of peritoneal entry on patients undergoing exploratory surgery for suspected eoc . for controls , we utilized specimens of parietal peritoneum obtained at the same sites from patients undergoing surgery for suspected benign disease . results from this study showed that the superficial layer , including the surface peritoneum and subjacent stroma specimens from the malignant group , revealed unique features at the transcript level compared to the benign group . these features are characterized by a dynamic process including cell attachments , signaling , growth stimulation , and , most importantly , a proinflammatory , pro - angiogenic , and extracellular matrix ( ecm ) remodeling effects . the peritoneum and subperitoneal stroma from the benign cases showed homogeneity in their transcript expression without the proinflammatory signature contrasting with some heterogeneity from patients with eoc , but an emphasis on inflammatory network responses and cell infiltrates . with increased knowledge in endothelial attachment and transcapillary migration , there is now a focus on inflammatory as well as non - inflammatory cell infiltrates and their contribution to cancer cell spread . chemokines and certain of the larger cytokines may contribute to the migration of leukocytic and other cells into a tumor environment among their other properties . the chemokines now have a new nomenclature based on their chemical structure , and extensive reviews have been published . in eoc , particularly in studies on ascites , substantial amounts of certain cc and cxc chemokines have been demonstrated , including ccl18 ( parc ) , cxcl8 ( il8 ) , ccl2 ( mcp1 ) , and ccl3 ( mip1 )   ( table 1 ) . transcripts for ccl4 ( mip1 ) , ccl5 ( rantes ) , ccl7 ( mcp3 ) have been demonstrated in eoc cells   ccl13 , however , is produced by ascitic macrophages and can not be induced in eoc cells . chemokines and cytokines may have in common potent functional properties , such as chemotaxis and proangiogenesis , and typically have effects in proximity to cells producing them . larger cytokine molecules , such as tgf , may also have chemotactic and proangiogenic effects . in advanced disease , tumor cells and other cells of nontumor origin , cxcl8 ( il8 ) is very pleiotropic and is constitutively produced or induced by both hematogenous and non - hematogenous cells and by hypoxia . we found that cxcl8 was overexpressed on the peritoneal stroma along with other network genes and appears to be a pivotal chemokine with substantial interactions at the transcript level with genes that are involved in inflammation , angiogenesis , and chemotaxis . receptors for the chemokines are expressed on a variety of hematogenous cells , including t cells and macrophages . of interest , cxcr4 , the receptor for cxcl12 ( sdf1 ) , appears to be selectively expressed on eoc cells   and may contribute to tumor cell migration . there is a lack of detectable change in expression of other chemokine receptors in response to cytokines , except for ccr2 , the receptor for ccl2 and certain other cc chemokines , which appears to be downregulated on eoc ascitic macrophages . this effect may interfere with migration of macrophages away from the tumor site while contributing to a tumor - promoting environment . unlike cytokines , many chemokines may exhibit more promiscuous binding to receptors . several cytokines have been detected in serum and ascites of eoc patients , including tgf isotypes , il10 , il6 , tnf , csf1 and il1 . tgf isotypes are produced by eoc cells   on mononuclear leukocytes , including cd14+dr-   and t regulatory cells . tgf , in its activated form , was previously considered a tumor - inhibitory cytokine but its tumor - reactive properties appear to be more complex ( table 2 ) . tgf also can have a tumor promoting effect in advanced cancer possibly through activation of cdk inhibitors that block the unbinding of the prb / e2f transcripts , and interference with tgf receptor binding mediated by h - ras , as well as consequent to c - myc , its reaction with the e2f transcription factor complex . the signaling pathway of tgf within tumor cells may also be subverted due to mutations , or interactions with other cytokines . a tgf activation response might , however , prevail in the microenvironment where it may contribute to myofibroblast and endothelial cell chemotaxis , tumor adhesion , and suppression of adaptive and innate immunity . il10 is also produced in association with eoc with a large contribution by cd14+dr- mo / ma , and these cells may function as immune regulatory cells . il6 is expressed by eoc tumor cells as well as mesothelial cells and has been detected in the serum and ascites of eoc cells [ 42 - 45 ] . a recent study has shown that il6 and mcp production by submesothelial cells can be enhanced during abdominal surgery . il6 also enhances tumor attachment and proliferation of tumor cells , most likely through the pi 3-k activation mechanisms , and can interfere with the maturation of mo / ma to dc . this finding might contribute to the large number of functionally immature dc in the ascitic fluid and absent levels of il12 , a product of dc maturation   ( and c butts ' unpublished observations ) . chemokines / receptors in eoc * in rna detected on eoc cell lines + proteins detected in ascites dual effects of cytokines on tumor / tumor microenvironment phenotypic and functional characterization of stromal inflammatory and non - inflammatory cell infiltrates will be useful for understanding the biology of metastasis . the chemical composition and dynamics of the extracellular matrix ( ecm ) are also likely to be important . thus , chemokines may " stick " to other proteins in the stromal microenvironment , enhancing their chemoattraction and other properties by accumulating at these sites . proteoglycans , which comprise a protein core , and sulphated or non - sulphated aminoglycan side chains could facilitate this . the proteoglycans include a variety of molecules , such as versican , decorin , hyaluran , and heparan with different side chains . the side chain of decorin can be of the dermatin type or chondroitin so4 type , each having non - overlapping different functions . we have previously shown that decorin chondroitin so4 is expressed with myofibroblasts in the adjacent stroma of eoc tissues   ( figure 2 ) . a recent paper has shown that endothelial cells stimulated in culture on a collagen type i matrix in the presence of il6 and il10 synthesized decorin . this is of particular interest since both il6 and il10 are highly expressed in eoc . chemokines may attach covalently to proteoglycans that express gag sequences , while retaining their effects on tumor microenvironment cells . in contrast , proteoglycans might also interfere with the binding of activated tgf to its receptors . histochemical staining of human ovarian tissue with anti-6-sulfate chondroitin or anti - smooth muscle -actin antibody . serial 5-m sections of paraffin - embedded tumors were stainead with anti-6-sulfate chondroitin ( a ) or anti - smooth muscle -actin ( b ) . a large family of receptors called integrins can regulate many functions at both the cellular and ecm levels . their functions , however , are complex since integrins can associate with other integrins or growth factor receptors or adaptive proteins producing bi - directional effects to and from the cell membrane surface . integrin mediated effects include cytoskeletal changes through complexing with  actinin and other proteins with downstream effects on actin . these changes may affect cell survival , proliferation , motility , and differentiation . depending upon the particular signaling pathway dominance integrins may modulate or enhance the expression of other integrins and receptors , e.g. 1 and 3 integrins , which can influence apoptosis . lack of detection of the cell - to - cell adhesion molecule e - cadherin on cuboidal cells of ovarian surface epithelium in contrast to its upregulated expression on metaplastic intra - ovarian cystic glands and early well - differentiated glandular carcinoma suggest that the latter cells may have been derived from the migrating surface ovarian cells . e - cadherin also inhibits the anti - apoptotic pi3k signaling pathway and e - cadherin expression in advanced eoc metastatic nodules appears to be less prominent than other cadherin molecules . in a 3-d model of breast cancer , chronic activation of the 1 integrin has been shown to enhance the cancer phenotype in contrast to a different signaling effect from 6/4 integrin activation , leading to suppression of the cancer phenotype . in advanced eoc , the reduction or loss of e - cadherin expression is hypothesized to contribute to the spread and progression of the tumor . e - cadherin in both breast and ovarian cancers is considered a late tumor suppressor molecule . the importance of 1 signaling has been shown in experiments that demonstrate reversion of the malignant phenotype when 1 integrin is blocked with anti 1 mabs . these findings overall suggest that altered expression of adhesion molecules , such as cadherein , could serve different functions during the pathogenesis of the eoc disease process . antibody - mediated inhibition of integrin 1 has also been shown to interefere with production of decorin which is an important part of the ecm . representative animal models of eoc need to combine the oncogenic developmental pathways as well as contributions from the cellular and ecm environment of the epithelium and stroma . there has been some recent progress in the development of suitable mouse models for human ovarian cancer . because of marked heterogeneity of ovarian cancer both at histopathologic and clinical levels , the underlying mechanisms that produce the altered gene expression profile in the eoc is not clear . however , it is reasonable to assume that the altered gene expression profile is at least in part due to activation of oncogenic events that transform the ovarian surface epithelial cells . toward this end , it has been shown that oncogenic hrasor krasactivates multiple proinflammtory cytokines and angiogenic factor cytokines during the malignant transformation of ovarian surface epithelial cells in a newly created genetically defined model for ovarian cancer . in this model , introduction of sv40 t / t antigen extended the life span of primary cultured ovarian surface epithelial cells for a few more passages ; however , these t / t antigen - expressing cells are still mortal . introduction of the catalytic subunit of telomerase ( htert ) results in immortalization of these cells . introduction of hrasor krasresults in transformation of these cells as reflected on the increased number of anchorage independent growth and tumor development after subcutaneous injection of these cells . peritoneal injection of the transformed cells produced undifferentiated carcinoma or malignant mixed mullerian tumor and developed ascites , the tumor cells are focally positive for ca125 and mesothelin . gene expression profile analysis of transformed cells revealed elevated expression of several cytokines including interleukin ( il)-1 , il6 , and il8 , that are up - regulated by the nf-b pathway , which is known to contribute to naturally occurring human eoc . incubation with antibodies to il-1 or il8 led to apoptosis in the ras - transformed cells and ovarian cancer cells but not in immortalized cells that had not been transformed . thus , the transformed human ovarian surface epithelial cells recapitulated many features of natural ovarian cancer including a subtype of ovarian cancer histology , formation of ascites , ca125 expression , and nf-b - mediated cytokine activation . these cells provide a novel model system to study human ovarian cancer . because of the remarkable similarity of gene expression between the ras - transformed ovarian surface epithelial cells and peritoneum associated with ovarian cancer , these immortalized preneoplastic ovarian epithelial cell lines may provide a valuable experimental tool to examine the role of each of the cytokines in the peritoneum during ovarian cancer development . susceptibility of the stromal compartment of the peritoneum to proliferative signals has been well documented in animal models of the peritoneal fibrosing syndrome following exposure to chemical peritoneal dialysates . in these models , alterations to the stromal environment occur in response to the dialysate resulting in infiltration of two main cell populations , fibroblasts secreting mcp-1 , vegf , and hsp47 and macrophages which can express tgf , tnf , il1 and fibronectin . macrophages in these models were shown to be recruited by several cc chemokines , mcp-1 , rantes , and mip-1 and collagen - dependent endothelial cells . moreover , removal of the fibroblast element in a knockout animal model abrogated the ma infiltration and the fibrotic process . a similar process has been described in renal fibrosis , which also involves mononuclear leukocytes and myofibroblasts . in eoc , it is possible that molecules derived from the primary or peritoneal surface metastases could be distributed throughout the peritoneal cavity . even in the absence of ascites , the distribution of these molecules could possibly be facilitated by negative pressure in the peritoneal cavity and peristalsis of the intestines . ascites indicate a more advanced stage of the disease which could be a consequence of alterations in permeability of the peritoneum or extensive lymphatic obstruction . in subperitoneal metastatic growth , the ascites may be almost acellular whereas surface exophytic lesions may be accompanied by large numbers of free - floating tumor cells , mesothelial cells and leukocytes , and in some cases , the ascites has a hemorrhagic appearance . in summary , we have shown that peritoneal structures of patients with eoc are different at the transcript level from those of patients with benign conditions . the changes observed reflect alterations in cytoskeletal and signaling pathways that suggest regional activity from integrins , cytokines , hormone growth factors , and adaptive proteins . in addition , there appears to be intense chemokine activity , particularly of the cxc motif chemokines , suggesting a pattern of chemotactic influence on leukocytic as well as other cell types . enhanced collagenase activity would contribute to remodeling of the stromal compartment and creation of a favorable environment for infiltration of leukocytes as well as other cells , such as myofibroblasts and endothelial cells . gene profiling of the peritoneum may provide hints about early transition steps to cancer or provide insight into changes that may actually facilitate the spread of cancer to adjoining tissues . it is anticipated that future studies using high throughput technologies with a multidimensional approach will enhance understanding of these alterations and their biological significance . these efforts could help identify critical alterations in the environment surrounding the cancer and its metastases and might ultimately lead to advances in diagnosis , prognosis , and novel approaches to therapeutic targeting in eoc . the past few decades have seen considerable progress in chemotherapeutics of eoc that are contributing to an overall reduction in mortality . however , eoc is heterogenous in its histopathology and sensitivity to chemotherapy . in order to overcome redundancies in the pathways and networks that control tumor cell growth , a number of peritoneal structures could serve as useful potential targets , including inflammatory and noninflammatory stromal cells , as well as production of molecules in the ecm , such as chemokines . in vitro experiments it is also likely that malignant cells from the primary tumor or metastasis might modify the microenvironment , preparing both surface epithelial and stromal cells to support the growth and proliferative activity of the tumor . thus , future strategies should attempt to identify those pathways and networks in the microenvironment that are critical to tumor cell survival .
epithelial ovarian cancer ( eoc ) is a significant cause of cancer related morbidity and mortality in women . 
 preferential involvement of peritoneal structures contributes to the overall poor outcome in eoc patients . 
 advances in biotechnology , such as cdna microarray , are a product of the human genome project and are beginning to provide fresh opportunities to understand the biology of eoc . 
 in particular , it is now possible to examine in depth , at the molecular level , the complex relationship between the tumor itself and its surrounding microenvironment.this review focuses on the anatomy , physiology , and current immunobiologic research of peritoneal structures , and addresses certain potentially useful animal models . 
 changes in both the inflammatory and non - inflammatory cell compartments , as well as alterations to the extracellular matrix , appear to be signal events that contribute to the remodeling effects of the peritoneal stroma and surface epithelial cells on tumor growth and spread . 
 these alterations may involve a number of proteins , including cytokines , chemokines , growth factors , either membrane or non - membrane bound , and integrins . 
 interactions between these molecules and molecular structures within the extracellular matrix , such as collagens and the proteoglycans , may contribute to a peritoneal mesothelial surface and stromal environment that is conducive to tumor cell proliferation and invasion . 
 these alterations need to be examined and defined as possible prosnosticators and as therapeutic or diagnostic targets .