PCNA and adenocarcinoma: In the present study, the expression of female hormone receptors (ER and PR), as well as EGFR and PCNA, was examined in NNK-induced lung tumors in female A/J mice (a rodent lung carcinogenesis model) in order to investigate the possible associations between different factors in mouse lung tumors, including adenomas, carcinomas in adenomas and adenocarcinomas.