PARP1 and nasopharyngeal carcinoma: For instance, the sustained activation of Poly(ADP-Ribose) Polymerase 1 (PARP1) in tumor cells with low epithelial cell transforming 2 (ECT2) expression inhibits nucleolar transcription, thereby promoting ribosomal DNA damage repair and causing radiotherapy resistance in lung cancer and nasopharyngeal carcinoma [8].