RAD51 and small cell lung carcinoma: The ability of the cells to form RAD51 foci whilst incapable of performing plasmid re-joining by HRR is a novel finding and indicates that the defect is downstream of RAD51, as has been identified in a non-small cell lung cancer cell line, Calu-6, where RAD51 foci fail to resolve leading to their persistence causing incomplete DNA repair [40].