Consistently, subcutaneous tumors formed by NICD1-mutant NSCLC cells presented significantly increased levels of RFC4, CCND1, and PCNA and a decreased proportion of TUNNEL-positive tumor cells as compared to those formed by vector-control cells, whereas subcutaneous tumors formed by RFC4-silenced NICD1-mutant NSCLC cells presented remarkable reductions in RFC4 protein levels and only marginally altered levels of NICD1, CCND1, or PCNA expression or apoptotic tumor cell proportion (Fig. 6d). The gene discussed is PCNA; the disease is non-small cell lung carcinoma.