By using the CRISPR/Cas9 system to completely ablate RECQ1 expression, and reconstitution with wild-type RECQ1 or breast cancer risk-associated RECQ1 variants, we found that MDA-MB-231 breast cancer cells expressing these missense RECQ1 mutants are more sensitive to gemcitabine, a drug that induces replication-associated DNA damage and is used for triple-negative breast cancer [34]. This evidence concerns the gene RECQL and triple-negative breast carcinoma.