PC-9/ER, erlotinib-resistant non-small cell lung cancer cells with mutations in EGFR (ex 19 del + T790M of EGFR), unlike parental erlotinib-sensitive PC-9 cells, did not show cleavage of PARP in response to anti-cancer drugs such as erlotinib or osimertinib (Figure 1A). Here, EGFR is linked to cancer.