PDGFRA and gastrointestinal stromal tumor: However, siRNA-mediated depletion of WEE1 led to significantly decreased viability in both isogenic lines (viability score = 0.48 in GIST-T1+Cas9; 0.41 in GIST-T1+D842V KITKO), whereas knockdown of MAP3K3 affected viability in the PDGFRA mutant cell line (viability score = 0.39).