Kuroda T, Ogiwara H, Sasaki M, et al. - In the present work, standard chemotherapeutic options suitable for ARID1A-deficient ovarian clear cell carcinoma (OCCC) patients were investigated. Using multiple ARID1A-knockout cell lines and an OCCC cell line panel, researchers identified drugs with selective toxicity to ARID1A-deficient OCCC cells among six cytotoxic drugs used in standard chemotherapy for OCCC. A xenograft model was used to assess the anti-tumor effects of drug treatment. They identified seven OCCC patients who received single-agent therapy with gemcitabine in a retrospective cohort of 149 OCCC patients to obtain proof of concept in patients. Outcomes revealed selective sensitivity of ARID1A-Deficient Ovarian Clear Cell Carcinoma (OCCC) cells to gemcitabine. Treatment with gemcitabine led to the suppression of the growth of xenograft derived from ARID1A-Deficient OCCC cells. Apoptosis in ARID1A-deficient OCCC cells occurred with gemcitabine treatment. In ARID1A-deficient OCCC patients, better response to gemcitabine was observed than that observed for ARID1A-proficient OCCC patients.