PCNA and non-small cell lung carcinoma: The protein expressions of the senescence markers cyclin-dependent kinase inhibitor CDKN1A/p21/Waf1/Cip1 and cyclin D1 (CCND1) were further determined by Western blot analyses, and the expression levels were clearly induced upon irradiation, while the expression levels of the proliferating cell nuclear antigen (PCNA) were reduced, without obvious effects concerning the NSCLC-conditioned media treatments (Figure 2F).