The inverse correlation of RB and p16INK4 expression and the absence of p16INK4 inactivation in RB (-/-) SCLC lines (0/48) confirms a common p16INK4/RB growth suppressor pathway in human cancers and provides evidence that p16INK4, and not an adjacent gene on chromosome 9p, is a specific target for mutational events.
Loss of the p16 gene is frequent in and highly specific to lymphoid malignancies (54 of 183 [30%] in lymphoid tumor v2 of 219 [1%] in myeloid tumors; P < .0001).
The tumor suppressor genes p16INK4A and p15INK4B map to the 9p21 chromosomal locus and are either homozygously deleted or mutated in a wide range of human cancer cell lines and tumors.
Our findings suggest that homozygous deletion of the p16 gene is seen in about 15% of ALL cases, is not restricted to cases with cytogenetically detectable 9p deletion, and could have a pathogenetic role in this malignancy.
Carcinogenesis is a multistage process involving activation of protooncogenes, e.g., ras, and inactivation of tumor suppressor genes, e.g., p53 and p16INK4.p53 is a prototype tumor suppressor gene that is well suited for analysis of mutational spectrum in human cancers; it is the most common genetic lesion in human cancers, it is a reasonable size for a molecular target, and it may indicate selection of mutations with pathobiological significance.
These results are consistent with the idea that p16 allelic variants that decrease Cdk interaction predispose individuals who carry them to an increased risk of cancer.
One half of all cancer cell lines and one fourth of lung cancer cell lines examined to date contain homozygous deletions (i.e., both alleles lost) of CDKN2.
PCR-single strand conformational polymorphism analysis of CDKN2 exons 2 and 3 and MTS2 exon 2 failed to demonstrate mutations in either CDKN2 or MTS2 in any of the T- or B-cell malignancies, with two possible exceptions.
We analysed the DNAs from 37 gliomas of several grades of malignancy for allelic loss of chromosome 9p and aberrations of the MTS1/p16 and MTS2/p15 genes.
Recent data suggest that homozygous deletion of the cyclin-dependent kinase 4 inhibitor gene (CDKN2), a putative tumour suppressor gene located on chromosome 9p21, represents a common genetic event in human cancer.
Loss of heterozygosity studies in melanoma and pancreatic carcinoma from gene carriers strongly support the view that CDKN2 is a general tumour suppressor gene predisposing not only to melanoma but also to other malignancies.
Our data confirm the predicted reciprocity between Rb inactivation and p16 expression in a common human malignancy and define differential p16 expression as a fundamental distinction between NSCLC and SCLC.
p16INK4A, a specific inhibitor of cyclin-dependent kinase (cdk)4 and cdk6, is a candidate tumor suppressor in malignancies with wild-type retinoblastoma (Rb).
Molecular genetic studies have revealed that deletion of the p16 and p15 genes occurs frequently in cancer cell lines and in certain malignant neoplasms.
In order to determine whether MTS-1 sequences are deleted or mutated in cell lines derived from these cancers, we performed PCR amplification of MTS-1 exons 1 and 2.
Furthermore, CDKN2 mRNA levels were similar in the 9 cancer cell lines that retain CDKN2, as compared to normal human ovarian surface epithelial cell lines.