In addition, using a CCK-8 assay in MDA-MB-231 and MDA-MB-468 cancer cells, we observed that CHK1 knockdown potentiated ADR-induced cytotoxicity (Figure 2B, C; Figure S2A, B), whereas the overexpression of CHK1 significantly reduced ADR cytotoxicity (Figure S3C, D). The gene discussed is CHEK1; the disease is cancer.