PB1699 A SCREENING OF ANTINEOPLASTIC DRUGS FOR ACUTE MYELOID LEUKEMIA REVEALS THAT FLUDARABINE AND CYTARABINE HAVE WEAK CAPACITY AS INDUCERS OF IMMUNOGENIC CELL DEATH

Abstract

Background:Although antineoplastic drugs used as induction chemotherapy for patients with acute myeloid leukemia (AML) result in high rate of complete remission, disease relapse occurs in the majority of cases, unless stem cell transplant is not performed. Development of new therapies is, then, a major medical need. Among them, strategies harnessing the immune system against leukemia are under active investigation. It is known that the cancer cell death induced by some antineoplastics drugs, such as anthracyclines, is highly immunogenic and results in the maturation of dendritic cells (DCs) and in the efficient cross‐priming of anti‐tumor T cells. This process, named immunogenic cell death (ICD), is characterized by Calreticulin (CRT) and Heat Shock Proteins 70 and 90 (HSP70/90) translocation to cell membrane and release of HMGB1 protein from nucleus.Aims:In this study, we were interested in in vitro comparison of five among the most widely used drugs for AML as ICD inducers.Methods:HL‐60 AML cell lines were treated with Daunorubicin (DNR), Cytarabine (Ara‐C), Etoposide (VP‐16), Fludarabine (Fluda) and Bortezomib. After apoptosis detection by flow cytometry, traslocation of CRT, HSPs70/90 and HMGB1 release from nucleus were evaluated using flow cytometry and immunofluorescence. Successively, the treated cells were used for loading into healthy donor‐derived DCs which were used to induce T cell proliferation as evaluated by flow cytometry using CFSE.Results:All five tested drugs induced a comparable levels of apoptosis. While Bortezomib and VP16 as well as DNR, which is a well‐known ICD inducer, were capable to induce CRT and HSP70/90 traslocation and HMGB1 release from nucleus, Fluda and Ara‐C have low, if any, capacity to induce ICD‐related events. Importantly, only DNR, Bortezomib and VP16 treatment, but not Ara‐C and Fluda, induced DC maturation, thus confirming that ICD‐related events correlate with immunogenic changes in DCs. At the functional level, VP16 was comparable to DNR at eliciting T‐cell proliferation via DCs, whereas Bortezomib, despite its capacity of inducing DC maturation via ICD, had low effect on T‐cell proliferation. Again, Ara‐C and Fluda had no effect on T‐cell proliferation.Summary/Conclusion:Our results indicate a novel and poorly‐investigated feature of antineoplastic drugs, commonly used for the treatment of AML, which is based on their different immunogenic potential. Under this viewpoint, Fluda and Ara‐C have weak, if any, capacity as inducers of immunogenic cell death, whereas VP16 and DNR are very effective. Further experiments, addressing the synergistic effects of these different drugs, may help to combine their conventional cytotoxic activity with their immunogenic capacity, thus providing the platform for a novel approach to anti‐leukemia chemotherapy.