Given that SLFN11 expression, both alone and in combination with BRCA deficiency, leads to increased ssDNA gaps and hypersensitivity to PARPis, we conducted a retrospective analysis of SLFN11 expression using immunohistochemistry in a cohort of 73 ovarian cancer patients who had received olaparib as maintenance therapy at Keio University Hospital (Fig. 7A, B). The gene discussed is SLFN11; the disease is ovarian carcinoma.