PARP1 and triple-negative breast carcinoma: MUC1-C also forms nuclear complexes with poly(ADP-ribose) polymerase 1 (PARP1), which can catalyze the poly-ADP-ribosylation (PARylation) of itself and multiple target proteins to initiate the repair of single-strand and double-strand breaks in triple-negative breast cancer (TNBC) 23.