3022 – METABOLIC AND EPIGENETIC IMPACT OF CD44 ANTIBODY-INDUCED DIFFERENTIATION IMPLICATES THE USE OF EPIGENETIC THERAPIES IN AML TREATMENT

Abstract

Acute myeloid leukemia (AML) is a subset of leukemia characterized by the clonal expansion of abnormal myeloid blasts. The poor prognosis of AML patients caused by low tolerance to intensive chemotherapy and high relapse rates triggered by leukemic stem cells has encouraged the pursuit of alternative therapies. Differentiation therapy, which involves the use of agents that can release the differentiation block in these leukemic stem/blasts has emerged as a promising therapy following the success of All-trans retinoic acid (ATRA) on one AML subtype. Efforts focused on finding differentiation agents that are effective on other AML subtypes brought into light the possibility of using anti-CD44 antibodies to target AML cells. Anti-CD44 has been shown to release the differentiation block in varying AML subtypes and work in our lab is focused on understanding the mechanism by which it induces its effects. Recent studies highlight the role that epigenetic and metabolic regulation plays during hematopoiesis and leukemogenesis, therefore, in this work we investigated the epigenetic and metabolic mechanisms associated with anti-CD44 induced differentiation. Using AML cell lines from different subtypes, we demonstrated that anti-CD44 treatment results in an extensive change of histone modifications. We found that inhibiting CBP/p300 (responsible for H3K9ac) and MLL (responsible for H3K4me1/2/3) attenuated the differentiation promoting effects of anti-CD44. Conversely, inhibition of EZH1/2 (responsible for H3K27me3) enhanced anti-CD44’s effects. The observed increase in H3K4me can be caused by an accumulation of succinate, a metabolite that is part of the tricarboxylic acid cycle. Taken together, these data highlight the promising potential of using anti-CD44 either alone or in combination with epigenetic inhibitor as a therapeutic agent across multiple subtypes in AML. Acute myeloid leukemia (AML) is a subset of leukemia characterized by the clonal expansion of abnormal myeloid blasts. The poor prognosis of AML patients caused by low tolerance to intensive chemotherapy and high relapse rates triggered by leukemic stem cells has encouraged the pursuit of alternative therapies. Differentiation therapy, which involves the use of agents that can release the differentiation block in these leukemic stem/blasts has emerged as a promising therapy following the success of All-trans retinoic acid (ATRA) on one AML subtype. Efforts focused on finding differentiation agents that are effective on other AML subtypes brought into light the possibility of using anti-CD44 antibodies to target AML cells. Anti-CD44 has been shown to release the differentiation block in varying AML subtypes and work in our lab is focused on understanding the mechanism by which it induces its effects. Recent studies highlight the role that epigenetic and metabolic regulation plays during hematopoiesis and leukemogenesis, therefore, in this work we investigated the epigenetic and metabolic mechanisms associated with anti-CD44 induced differentiation. Using AML cell lines from different subtypes, we demonstrated that anti-CD44 treatment results in an extensive change of histone modifications. We found that inhibiting CBP/p300 (responsible for H3K9ac) and MLL (responsible for H3K4me1/2/3) attenuated the differentiation promoting effects of anti-CD44. Conversely, inhibition of EZH1/2 (responsible for H3K27me3) enhanced anti-CD44’s effects. The observed increase in H3K4me can be caused by an accumulation of succinate, a metabolite that is part of the tricarboxylic acid cycle. Taken together, these data highlight the promising potential of using anti-CD44 either alone or in combination with epigenetic inhibitor as a therapeutic agent across multiple subtypes in AML.