Epigenetic inactivation of a RAS association domain family protein from the lung tumour suppressor locus 3p21.3.
Allelic loss at the short arm of chromosome 3 is one of the most common and earliest events in the pathogenesis of lung cancer, and is observed in more than 90% of small-cell lung cancers (SCLCs) and in 50-80% of non-small-cell lung cancers (NSCLCs). Frequent and early loss of heterozygosity and the presence of homozygous deletions suggested a critical role of the region 3p21.3 in tumorigenesis and a region of common homozygous deletion in 3p21.3 was narrowed to 120 kb (ref. 5). Several putative tumour-suppressor genes located at 3p21 have been characterized, but none of these genes appear to be altered in lung cancer. Here we describe the cloning and characterization of a human RAS effector homologue (RASSF1) located in the 120-kb region of minimal homozygous deletion. We identified three transcripts, A, B and C, derived from alternative splicing and promoter usage. The major transcripts A and C were expressed in all normal tissues. Transcript A was missing in all SCLC cell lines analysed and in several other cancer cell lines. Loss of expression was correlated with methylation of the CpG-island promoter sequence of RASSF1A. The promoter was highly methylated in 24 of 60 (40%) primary lung tumours, and 4 of 41 tumours analysed carried missense mutations. Re-expression of transcript A in lung carcinoma cells reduced colony formation, suppressed anchorage-independent growth and inhibited tumour formation in nude mice. These characteristics indicate a potential role for RASSF1A as a lung tumour suppressor gene.
Dammann
R
R
Department of Biology, Beckman Research Institute, City of Hope Medical Center, Duarte, California, USA.
Li
C
C
Yoon
J H
JH
Chin
P L
PL
Bates
S
S
Pfeifer
G P
GP
D044503:5-Methylcytosine; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics*; D018288:Carcinoma, Small Cell / Q000235:genetics*; D002893:Chromosomes, Human, Pair 3; D018899:CpG Islands; D003596:Cytosine / Q000031:analogs & derivatives / Q000378:metabolism; D019175:DNA Methylation; D018076:DNA, Complementary; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D016147:Genes, Tumor Suppressor; D019073:HT29 Cells; D006367:HeLa Cells; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D051381:Rats; D016329:Sp1 Transcription Factor / Q000378:metabolism; D025521:Tumor Suppressor Proteins; D051760:Xeroderma Pigmentosum Group A Protein; D020726:ral Guanine Nucleotide Exchange Factor / Q000378:metabolism*; D018631:ras Proteins / Q000378:metabolism*
D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D009363:Neoplasm Proteins; C411762:RASSF1 protein, human; D016601:RNA-Binding Proteins; D016329:Sp1 Transcription Factor; D025521:Tumor Suppressor Proteins; C497314:XPA protein, human; D051760:Xeroderma Pigmentosum Group A Protein; C497315:Xpa protein, mouse; D020726:ral Guanine Nucleotide Exchange Factor; D044503:5-Methylcytosine; D003596:Cytosine; D018631:ras Proteins