Genome-Wide CRISPR-Cas9 Screen Reveals Selective Vulnerability of ATRX-Mutant Cancers to WEE1 Inhibition

The tumor suppressor geneATRXis frequentlymutated in a variety of tumors including gliomas and liver cancers, which are highly unresponsive to current therapies. Here, we performed a genome-wide synthetic lethal screen, using CRISPR-Cas9 genome editing, to identify potential therapeutic targets specific for ATRX-mutated cancers. In isogenic hepatocellular carcinoma (HCC) cell lines engineered forATRXloss, we identified 58 genes, including the checkpoint kinaseWEE1, uniquely required for the cell growth ofATRXnull cells. Treatment with the WEE1 inhibitor AZD1775 robustly inhibited the growth of several ATRX-deficient HCC cell lines in vitro, as well as xenografts in vivo. The increased sensitivity to the WEE1 inhibitor was caused by accumulated DNA damage-induced apoptosis. AZD1775 also selectively inhibited the proliferation of patient-derived primary cell lines from gliomas with naturally occurring ATRX mutations, indicating that the synthetic lethal relationship between WEE1 and ATRX could be exploited in a broader spectrumof human tumors. As WEE1 inhibitors have been investigated in several phase II clinical trials, our discovery provides the basis for an easily clinically testable therapeutic strategy specific for cancers deficient in ATRX. Significance: ATRX-mutant cancer cells depend onWEE1, which provides a basis for therapeutically targeting WEE1 inATRX-deficient cancers.