Immunohistochemical analysis demonstrated the up-regulation of the protein levels of Mcm2, Fen1, Ube2C and cyclin D1 in lung adenocarcinoma tissue of NNK-exposed Gprc5a-knockout mice compared to the levels in normal lung tissue obtained from the same mice (Fig. 7A). The gene discussed is CCND1; the disease is lung adenocarcinoma.