Synergistic Anti-Leukemic Effect Of Trc105 And Decitabine In AML Xenografts

Acute myeloid leukemia (AML) is an aggressive hematologic malignancy, often characterized by poor prognosis following standard induction therapy. The DNA methyltransferase inhibitor decitabine (DAC) is an alternative to intensive chemotherapy in elderly and relapsed/refractory AML patients. Despite some efficacy, DAC monotherapy does not promote complete remission and overall survival rates are very poor. Therefore, novel therapeutic regimens for AML are warranted. CD105 (endoglin), a receptor for the TGF-ß superfamily, is expressed in various hematopoietic malignancies, including AML in which high expression correlates with poor prognosis. We have recently demonstrated that targeting CD105+ AML blasts with the TRC105 monoclonal antibody abrogates leukemogenesis in vivo. Based on these encouraging findings, here we investigated whether TRC105 in combination with DAC could represent a novel therapeutic option to treat relapsed/refractory AML. Treatment of leukemic mice with DAC in combination with TRC105 resulted in superior survival and significant reduction of leukemia burden in the bone marrow (BM) of AML xenografts compared to DAC monotherapy. To determine if TRC105 anti-leukemogenic effect is mediated by NK cells, we performed in vitro and in vivo studies. In the latter, we tested TRC105 in the context of NK depletion by injecting mice with an antibody to CD122. TRC105 treatment resulted in comparable reduction of leukemia burden in xenografts regardless of NK depletion, demonstrating that the anti-leukemogenic effect of TRC105 in AML is independent of NK cells. Altogether, our findings provide proof-of-principle for the clinical evaluation of TRC105 in combination with DAC in AML patients. Overall design: Human CD45+ cells were isolated from the bone marrow of AML-xenografts models treated with TRC105 (anti-human CD105 antibody) or IgG control. Transcriptomic analysis was performed by isolating total RNAs followed by library generation and sequencing.