Mechanisms of p16INK4A Inactivation in Non Small-Cell Lung Cancers

Oncogene. 1998 Jan 29;16(4):497-504. doi: 10.1038/sj.onc.1201559.

Abstract

The cyclin-dependent kinase inhibitor p16 (p16INK4A/CDKN2/MTS1) is a potent inhibitor of the cyclin D-dependent phosphorylation of the retinoblastoma gene (Rb) product, the inactivation of which induces loss of Rb-dependent G1 arrest through inappropriate phosphorylation of the Rb protein. To analyse the role of p16INK4A as a tumor suppressor in the genesis of non small cell lung cancers (NSCLC) and correlate loss of p16INK4A protein expression to genetic or epigenetic mechanisms, we have performed a comprehensive study of p16 status in a series of 43 NSCLC. To this end, we have investigated p16INK4A protein expression with immunohistochemistry, deletions of the gene by FISH, and determined the methylation status of exon 1alpha using a PCR-based methylation assay. Finally, possible mutations were studied by SSCP and subsequent sequencing. Twenty one of the 43 (49%) NSCLC studied exhibited an absence of p16INK4A nuclear staining. Of these, three (14%) had frameshift or missense mutations, seven (33%) displayed methylation of exon 1alpha and 10 (48%) displayed homozygous deletions. In total, 95% of the tumors with p16INK4A negative staining carried one of these three alternative genetic or epigenetic alterations. Furthermore, a high degree of chromosome 9 polysomy was found (58%) in those tumors with p16INK4A inactivation. Taken together these results suggest that deregulation of the p16 gene locus is a frequently occurring event in NSCLC through distinct mechanisms including rare point mutations, promotor methylation and frequent homozygous deletions. Furthermore, our data show that immunohistochemistry is a rapid and an accurate technique for screening of p16INK4A gene inactivation events that result in loss of protein expression.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenocarcinoma / genetics
  • Adenocarcinoma / metabolism
  • Adenocarcinoma / pathology
  • Carcinoma, Non-Small-Cell Lung / genetics*
  • Carcinoma, Non-Small-Cell Lung / metabolism
  • Carcinoma, Non-Small-Cell Lung / pathology
  • Carcinoma, Squamous Cell / genetics
  • Carcinoma, Squamous Cell / metabolism
  • Carcinoma, Squamous Cell / pathology
  • Carcinoma, Transitional Cell / genetics
  • Carcinoma, Transitional Cell / metabolism
  • Carcinoma, Transitional Cell / pathology
  • Chromosomes, Human, Pair 9 / genetics
  • Cyclin-Dependent Kinase Inhibitor p16 / genetics*
  • Cyclin-Dependent Kinase Inhibitor p16 / metabolism
  • DNA Methylation
  • Exons / genetics
  • Gene Deletion*
  • Gene Expression Regulation, Neoplastic
  • Genes, Tumor Suppressor / genetics*
  • Humans
  • In Situ Hybridization, Fluorescence
  • Lung Neoplasms / genetics*
  • Lung Neoplasms / metabolism
  • Lung Neoplasms / pathology
  • Neoplasm Proteins / genetics*
  • Neoplasm Proteins / metabolism

Substances

  • Cyclin-Dependent Kinase Inhibitor p16
  • Neoplasm Proteins