Abstract B23: Selective and rapid killing of mixed lineage leukemia and CALM-AF10 leukemia by SM7, a novel small molecule identified by chemical library screening

Abstract

Abstract Translocations involving the Mixed Lineage Leukemia (MLL) gene define the major proportion of infant leukemia, a disease that is characterised by a dismal prognosis due to treatment toxicity and therapy resistance. There is an urgent need for the development of less toxic, more selective and targeted therapies for this disease. In this study, we performed a cell-based chemical library screen on an infant MLL cell line, PER-485, in order to identify selective inhibitors of MLL leukemia. After screening initial hits for viability against a panel of 25 cell lines including MLL rearranged and wild-type MLL leukemia, solid tumors and control cells, SM7 was identified as a compound that significantly and selectively decreased the viability of MLL-rearranged (four out of seven) and related CALM-AF10 (two out of two) leukemia cell lines, without killing cell lines derived from wild-type MLL leukemia, solid tumours or normal cells. In contrast to currently developed MLL-inhibitors, the effect of SM7 in suppressing the characteristic MLL-driven gene expression signature in MLL-rearranged cells, with downregulation of leukemogenic HoxA9 and Meis1 expression, occurred within an hour after treatment. The transcript levels of cMyc and Bcl2, important survival proteins regulated by HoxA9, were also rapidly decreased in response to SM7. SM7 induced a rapid caspase-dependent apoptosis, with mitochondrial depolarization within twenty four hours of treatment. This is distinct from the action of other previously described MLL small molecule inhibitors. The rapid and selective toxicity of SM7 towards MLL-rearranged and CALM-AF10 leukemia cell lines suggests an important new avenue in the development of targeted therapies for this disease. Citation Format: Daria Chudakova, Klaartje Somers, Shiloh Middlemiss, Victoria Wen, Alan Kwek, Bing Liu, Molly Clifton, Sukey Pan, Sarah Cruikshank, Marissa Scandlyn, Tim Failes, Wendy Hoang, Ursula Kees, Olga Chernova, Andrei V. Gudkov, Michelle Haber, Murray Norris, Michelle Henderson. Selective and rapid killing of mixed lineage leukemia and CALM-AF10 leukemia by SM7, a novel small molecule identified by chemical library screening. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Pediatric Cancer Research: From Mechanisms and Models to Treatment and Survivorship; 2015 Nov 9-12; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(5 Suppl):Abstract nr B23.