CDKN2A and neoplasm: A similar phenomenon was reported in hTERT-immortalized human fibroblast cell lines (WI-38, Leiden), which have a diploid karyotype and in which Ink4a is deleted [48,49]; however, these cell lines require active H-Ras or H-Ras and inactive p53 for tumor formation, resulting in the acquirement of chromosome abnormalities.