CCND1 and mesothelioma: Christensen et al. demonstrated that several cell cycle genes—APC, CCND2, CDKN2A, CDKN2B, APPBP1, and RASSF1—are methylated in older mesothelioma patients, and those with methylation of RASSF1, a gene that encodes an activator of G1/S cell cycle arrest, through sequestering of CCND1, is significantly associated with elevated asbestos body counts and therefore longer asbestos exposure [38].