Expression of the candidate tumor suppressor gene hSRBC is frequently lost in primary lung cancers with and without DNA methylation.

Published

Journal Article

Recently, the human SRBC (hSRBC) gene, a candidate tumor suppressor gene (TSG), has been mapped to the chromosomal region 11p 15.5--p15.4 where frequent allele loss has been described in lung cancer. Aberrant methylation (referred to as methylation) of the promoter region of TSGs has been identified as an important mechanism for gene silencing. Loss of hSRBC protein expression occurs frequently in lung cancer cell lines and sodium bisulfite sequencing of the promoter region of hSRBC in several lung cancer cell lines suggested that methylation plays an important role in inactivating hSRBC. To determine the methylation status of hSRBC in a large collection of primary lung cancer samples, corresponding nonmalignant lung tissues and lung cancer cell lines (N=52), we designed primers for a methylation-specific PCR assay. Methylation was detected in 41% of primary non-small-cell lung cancers (NSCLC) (N=107) and in 80% of primary small-cell lung cancers (SCLC) (N=5), but was seen only in 4% of corresponding nonmalignant lung tissues (N=103). In all, 79% of lung cancer cell lines were methylated and the frequency of hSRBC methylation was significantly higher in SCLC (100%) than in NSCLC (58%) cell lines. Normal hSRBC protein expression was detected in only 18% of primary NSCLCs (N=93) by immunostaining and a significant association between loss of protein expression and methylation was found. hSRBC re-expression was observed after treatment of lung cancer cells with the demethylating agent 5-aza-2'-deoxycytidine. In addition, 45% of the 76 hSRBC immunostaining-negative NSCLCs did not have hSRBC promoter methylation, indicating that other mechanisms of hSRBC expression silencing also exist. Both hSRBC immunostaining and methylation results did not correlate with clinicopathological characteristics of these patients. Our findings suggest that hSRBC is a candidate TSG involved in lung cancer pathogenesis, where expression is frequently inactivated by methylation and other mechanisms.

Full Text

Duke Authors

Cited Authors

  • Zöchbauer-Müller, S; Fong, KM; Geradts, J; Xu, X; Seidl, S; End-Pfützenreuter, A; Lang, G; Heller, G; Zielinski, CC; Gazdar, AF; Minna, JD

Published Date

  • September 15, 2005

Published In

Volume / Issue

  • 24 / 41

Start / End Page

  • 6249 - 6255

PubMed ID

  • 15940253

Pubmed Central ID

  • 15940253

International Standard Serial Number (ISSN)

  • 0950-9232

Digital Object Identifier (DOI)

  • 10.1038/sj.onc.1208775

Language

  • eng

Conference Location

  • England