ESR1 and breast cancer: To confirm that the observed elevated NUDT5 RNA expression correlates with increased NUDT5 protein expression, we performed a Western-blot analysis of breast cancer cells (two normal-like breast cell lines: MCF-10A and MCF-12A; four ER-positive breast cancer cell lines: MCF-7, ZR-75-1, MDA-MB-361 and BT-474; and seven TNBC cell lines: MDA-MB-231, MDA-MB-436, MDA-MB-468, BT-20, HCC1143, HCC1937 and HCC70), all of which were in the exponential phase in cell culture.