Genome-Wide shRNA Screen Identifies WEE1 As a Critical Mediator of Cell Fate and Novel Therapeutic Target in AML,

Abstract 3503

Acute myeloid leukemia (AML) remains a therapeutic challenge despite increasing knowledge of the molecular origins of the disease, as the mechanisms of AML cell escape from chemotherapy remain poorly defined. We hypothesized that AML cells are addicted to specific molecular pathways in the context of chemotherapy and used complementary approaches to identify these addictions. Using novel molecular and computational strategies, we performed genome-wide shRNA screens to identify proteins which mediate AML cell fate in cytarabine in 2 AML cell lines (Molm13 and MV4-11). Over 55,000 shRNAs targeting over 11,000 genes were quantified by deep sequencing to identify shRNAs under-represented in the context of cytarabine as compared to no treatment. Complementary analyses identified 125 genes as mediators of AML cell fate in cytarabine. In addition we performed gene expression profiling of AML cells exposed to cytarabine to identify genes with induced expression in this context and examined existing gene expression data from primary patient samples. The integration of these independent analyses strongly implicates cell cycle checkpoint proteins, particularly WEE1, as critical mediators of AML cell fate in cytarabine. Knockdown of WEE1 in a secondary screen confirmed its role in AML cell survival in cytarabine. Pharmacologic inhibition of WEE1 in several, but not all, AML cell lines is synergistic with cytarabine, suggesting underlying molecular susceptibility to this combination of drugs. A WEE1 inhibitor is in Phase II trials in solid tumors, primarily as a means to abrogate the G2/M checkpoint in tumors with TP53 dysfunction. Further experiments demonstrate that inhibition of WEE1 prevents slowed S-phase progression induced by cytarabine in AML cells, broadening the functions of WEE1 that may be exploited therapeutically. Preliminary experiments indicate synergistic inhibition of AML cellular proliferation with daunorubicin in some AML cell lines. Experiments to determine whether WEE1 inhibition in combination with chemotherapy prolongs survival of mice with leukemia are underway. These data highlight the power of integrating functional and descriptive genomics, and identify WEE1 as potential therapeutic target in AML.