DNA repair enzymes are responsible for maintaining genomic integrity by repairing DNA damage. In cancer, mutations in genes encoding these enzymes, such as BRCA1 and BRCA2, can lead to defective DNA repair mechanisms. This results in the accumulation of mutations, genomic instability, and increased cancer risk. Therapies targeting DNA repair pathways, like PARP inhibitors, have shown efficacy in treating cancers with defective DNA repair mechanisms.