Both the retinoblastoma and p53 pathways are often genetically altered in human cancers and their complex regulation is in part mediated by the three gene products p16, p14(ARF), and p15 of the INK4 locus on chromosome 9p21.
The tumor suppressor genes p53, retinoblastoma (RB), p16, and p15 encode proteins that regulate the cell cycle cooperatively by controlling the transition from G1 to S phase and may play an important role in cell growth and differentiation.
Alterations of the RB, p53, p16(CDKN2), and p15 genes in human astrocytomas were screened by single strand conformation polymorphism analysis of polymerase chain reaction products (PCR-SSCP analysis) and then confirmed by dideoxy sequencing.