Researchers are hoping to harness the leukemia-killing antibodies made by cured AML patients to treat others with the disease.
Researchers are hoping to use the antibodies that destroy leukemia cells to treat other patients. These antibodies are made in patients with acute myeloid leukemia who are cured after allogeneic hematopoietic stem cell transplantation (HSCT).
“Patients who survive AML after allogeneic HSCT produce AML-specific antibodies to really unexpected targets, [including] the U5 snRNP200 complex,” lead study author Mette Hazenberg, said when presenting the data at the 2016 European Hematology Association (EHA) Congress, a gathering of thousands of medical professionals in Copenhagen, Denmark.
“Interestingly, when these antibodies bind to this complex, they actually kill the target cell—they kill the leukemic cells. This is a novel phenomenon and we we think we can develop this further into novel therapies,” added Hazenberg, who is one of the principal investigators at the Academisch Medisch Centrum in Amsterdam, The Netherlands.
Patients with AML can be cured with HSCT when the immune system of the donor generates a strong graft versus leukemia (GvL) response. Previous research has determined the contribution of T cells and natural killer (NK) cells to GvL immune responses; however, the role of B cells in this process is less understood. With this study, Hazenberg et al examined antibodies produced by donor-derived B cells to determine their role in GvL responses.
The study involved five patients with high-risk AML who had a potent GvL response after allogeneic HSCT, remaining disease-free for more than five years. The researchers isolated memory B cells from the patients’ peripheral blood that was acquired two-years following the stem-cell transplant. To establish antibody-producing clonal B cell lines, the isolated B-cells were transduced with Bcl-6 and Bcl-xL.
Using immunoprecipitation and mass-spectometry, Hazenberg et al screened the B cell lines and identified 17 antibodies that specifically bound to surface antigens on AML cell lines and blasts that had been isolated from patients in their clinic.
“These antibodies were really selective because they only bound to leukemic cells—blasts and cell lines—but not healthy cells,” said Hazenberg.
Seven of the 17 donor-derived antibodies recognized the U5 snRNP200 complex, which is part of the spliceosome found in the nucleus of healthy cells but located on the cell membrane of AML sells. Antibodies specific to the U5 snRNP200 complex were discovered in four of the five AML patients screened.
Both in vitro and in an AML mouse model, the antibodies specific to the U5 snRNP200 complex destroyed leukemia cells. “Cell death was induced in the absence of cytotoxic leukocytes or of complement, through a nonapoptotic process that depended on destabilization of the cytoskeleton as cell death could be blocked by incubation of the target cells with cytochalasin D, an actin polymerization inhibitor,” Hazenberg et al wrote in their EHA abstract.
The early-phase research with these antibodies—including an additional mouse model—is continuing, with the intent of starting human clinical trials soon.
When asked at EHA about the ideal patient population for such a trial, Hazenberg responded, “There are many patients with AML who cannot receive the standard treatment, such as elderly patients or patients who already received a lot of chemotherapy. I think you would have to start with those types of patients who no longer have other options.”
She also hinted at the potential for combination trials. “In the mice, we saw that these antibodies, by themselves, killed the leukemia, but of course you can also think of combination therapy in which you add this antibody to existing forms of chemotherapy.”
Watafiti wana matumaini ya kutumia antibodies za kuua leukemia zinazotengenezwa na wagonjwa waliopona wa AML kutibu wengine walio na ugonjwa huo. Watafiti wanatumaini kutumia kingamwili hizo zinazoangamiza chembe za leukemia kutibu wagonjwa wengine. Vipimo vya antibodi hutengenezwa kwa wagonjwa wenye leukemia ya myeloid kali ambao hupona baada ya kupandikizwa kwa seli za msingi za hematopoietic (HSCT). "Walalamikaji ambao wanaishi baada ya ALT HSCT hutengeneza antibodies maalum ya AML kwa malengo yasiyotarajiwa, ikiwa ni pamoja na U5 snRNP200 complex, ""mwandishi mkuu wa utafiti Mette Hazenberg alisema wakati wa kuwasilisha data katika Mkutano wa Chama cha Hematolojia ya Ulaya (EHA) ya 2016 - mkusanyiko wa maelfu ya wataalamu wa matibabu huko Copenhagen, Denmark." "Inavutia, wakati antibodies hizi kuunganisha kwa tata hii, wao kweli kuua seli lengo"wanaua seli leukemia. "Hii ni jambo jipya na tunafikiri tunaweza kuendeleza hii zaidi katika matibabu mapya, ""aliongeza Hazenberg, ambaye ni mmoja wa watafiti wakuu katika Academisch Medisch Centrum huko Amsterdam, Uholanzi." Wagonjwa wenye ugonjwa wa leukemia ya amyogovya wanaweza kuponywa na HSCT wakati mfumo wa kinga wa mtoaji unazalisha majibu ya nguvu ya graft dhidi ya leukemia (GvL). Utafiti wa awali umegundua mchango wa seli za T na seli za mauaji ya asili (NK) kwa majibu ya kinga ya GvL, hata hivyo, jukumu la seli za B katika mchakato huu halijaeleweka sana. Katika utafiti huu, Hazenberg et al alichunguza kingamwili zinazozalishwa na seli za B zinazotokana na wafadhili ili kuamua jukumu lao katika majibu ya GvL. Utafiti huo ulihusisha wagonjwa watano wenye hatari ya juu ya AML ambao walikuwa na majibu ya GvL baada ya HSCT ya allogeneic, wakibaki bila ugonjwa kwa zaidi ya miaka mitano. Watafiti waliweka kando seli za kumbukumbu za B kutoka kwa damu ya mgonjwa iliyopatikana miaka miwili baada ya kupandikizwa kwa seli za shina. Ili kuanzisha mstari wa seli za B za kloni zinazozalisha kingamwili, seli za B zilizotengwa zilipitishwa na Bcl-6 na Bcl-xL. Kwa kutumia immunoprecipitation na mass-spectometry, Hazenberg na wenzake walichunguza safu za seli za B na kutambua antibodies 17 ambazo zilikuwa zimeunganishwa kwa antigen za uso kwenye safu za seli za AML na blasts ambazo zilikuwa zimetengwa kutoka kwa wagonjwa katika kliniki yao. "Antibodies hizi zilikuwa za kuchagua kwa sababu ziliunganishwa tu na seli za leukemia - blasts na mistari ya seli - lakini si seli zenye afya", alisema Hazenberg. Katika antibodies 17 zilizopatikana kutoka kwa wafadhili, antibodies 7 zilitambua U5 snRNP200 complex, ambayo ni sehemu ya spliceosome inayopatikana katika nyuklia ya seli za afya lakini iko kwenye utando wa seli za AML. Antibodies maalum kwa U5 snRNP200 complex ziligunduliwa katika wagonjwa wanne kati ya watano wa AML waliochunguzwa. Katika majaribio ya in vitro na katika mfano wa panya wa AML, antibodies maalum kwa U5 snRNP200 complex iliharibu seli za leukemia. "Kifo cha seli kilisababishwa na kutokuwepo kwa leukocytes ya cytotoxic au ya complement, kupitia mchakato wa nonapoptotic ambao unategemea kutokuwa na utulivu wa cytoskeleton kama kifo cha seli kinaweza kuzuiwa na incubation ya seli za lengo na cytochalasin D, kizuizi cha polymerization ya actin. """ Utafiti wa awamu ya mapema na antibodies hizi - ikiwa ni pamoja na mfano wa panya wa ziada - unaendelea, kwa nia ya kuanza majaribio ya kliniki ya binadamu hivi karibuni. "Alipoulizwa katika EHA kuhusu idadi bora ya wagonjwa kwa jaribio kama hilo, Hazenberg alijibu, ""Kuna wagonjwa wengi wenye AML ambao hawawezi kupokea matibabu ya kawaida, kama vile wagonjwa wazee au wagonjwa ambao tayari wamepokea kemotherapy nyingi.""" "Nadhani unapaswa kuanza na aina hizo za wagonjwa ambao hawana chaguzi nyingine. "" Pia alidokeza uwezekano wa majaribio ya mchanganyiko." "Katika panya, tuliona kwamba kingamwili hizi, kwa wenyewe, ziliua leukemia, lakini bila shaka unaweza pia kufikiria tiba ya mchanganyiko ambapo unaongeza kingamwili hiki kwa aina zilizopo za tiba ya kemikali. """