We studied in vitro activity of four PARPi in Ets‐1‐expressing MDA‐MB‐231 and Ets‐1‐non‐expressing MCF‐7 breast cancer cell lines and we demonstrated that PARP‐1 inhibition increases oxidative DNA damage and oxidative stress only in MDA‐MB‐231. The gene discussed is PARP1; the disease is breast carcinoma.