Abstract 82: NuRD dpendent survival of acute leukemia cells

Abstract

Abstract Acute myeloid and T-cell acute lymphoblastic leukemia are aggressive subtypes of acute leukemias with 5-year survival rates ranging from 10% to 50%. CHD4, the ATPase chromatin re-modeling component of the NuRD co-repressor complex, has been shown to promote survival of some solid tumor cells (colon cancer, glioblastoma). Our laboratory has shown that CHD4 depletion increases sensitivity of both AML cell lines and primary cells to standard chemotherapy agents, and reduces colony formation in soft agar. Importantly, CD34+ progenitor cells are spared these phenotypic responses. Apart from CHD4, the classical NuRD complex contains either MBD2 or MBD3, and at least four other proteins (GATAD2A/B, HDAC1/2, MTA1/2/3, RBBP4/7). CHD4 is linked to MBD2 or MBD3 via GATAD2A/B proteins through a coiled-coil interaction. Therefore, we sought to determine whether the observed CHD4 effects on AML cell survival are through NuRD, or by acting outside of NuRD. We showed that depletion of either MBD2 or MBD3 did not reproduce the phenotypes observed with CHD4 depletion in U937 (AML) cell lines. However, depletion of both MBD2 and MBD3 resulted in a four-fold reduction in colony numbers in soft agar, and a two to three fold increased sensitivity to cytosine arabinoside (AraC) and daunorubicin (DNR) (AACR, 2019). In order to determine if these findings hold true for other poor prognosis acute leukemias, we have knocked down CHD4 in T-ALL cell lines (Jurkat, MOLT4) and showed equivalent effects on genotoxic sensitivity and colony formation, as in AML. In addition, we found a two-fold increase in 7-AAD-assessed apoptosis, and a significantly reduced proliferation of CHD4 depleted cells in both T-ALL and AML cell lines. These effects are correlated with and possibly mediated by observed E2F1 depletion in CHD4 knockdown leukemia cell lines. Moreover, a five-fold reduction in the number of colonies of primary AML cells in methylcellulose-based media was observed. Similar to the findings in AML, MBD proteins showed redundancy in Jurkat T-ALL cells, whereby depletion of either MBD2 or MBD3 did not increase genotoxic sensitivity or reduce colony forming potential, but depletion of both together did so by a factor of up to three to five-fold respectively. Restoring MBD2 in U937 leukemia cells depleted of both MBD2 and MBD3 reversed increased genotoxic sensitization, demonstrating the on-target effects of MBD2 shRNA knockdown. We conclude that depletion of CHD4, or combined depletion of MBD2 and MBD3, produce equivalent beneficial phenotypes in both AML and T-ALL cell lines through disruption of the NuRD complex. Thus, targeting the common coiled coil structural motif that links both MBD2 and MBD3 to the GATAD2-CHD4 chromatin remodeling component of the NuRD complex may offer promise for improved therapy in acute leukemias of both myeloid and lymphoblastic origin. Citation Format: Javeria Aijaz, Shengzhe Shang, David C. Williams, Gordon D. Ginder. NuRD dpendent survival of acute leukemia cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 82.