Frequent epigenetic inactivation of hSRBC in gastric cancer and its implication in attenuated p53 response to stresses.
hSRBC is a putative tumor suppressor located at 11p15.4, at which frequent genomic loss has been observed in several human malignancies. To explore the candidacy of hSRBC as a suppressor of gastric tumorigenesis, we analyzed the expression and mutation status of hSRBC in gastric tissues and cell lines. hSRBC transcript was expressed in all normal and benign tumor tissues examined, but undetectable or very low in 73% (11/15) cancer cell lines and 41% (46/111) primary tumors. Loss or reduction of hSRBC expression was tumor-specific and correlated with stage and grade of tumors. While allelic loss or somatic mutations of the gene were infrequent, its expression was restored in tumor cells by 5-aza-2'-deoxycytidine treatment and aberrant hypermethylation of 23 CpG sites in the promoter region showed a tight association with altered expression. Transient or stable expression of hSRBC led to a G(1) cell cycle arrest and apoptosis of tumor cells, and strongly suppresses colony forming ability and xenograft tumor growth. In addition, hSRBC elevated apoptotic sensitivity of tumor cells to genotoxic agents, such as 5-FU, etoposide and ultraviolet. Interestingly, hSRBC increased the protein stability of p53 and expression of p53 target genes, such as p21(Waf1), PUMA and NOXA, while hSRBC-mediated cell cycle arrest and apoptosis were abolished by blockade of p53 function. Our findings suggest that hSRBC is a novel tumor suppressor whose epigenetic inactivation contributes to the malignant progression of gastric tumors, in part, through attenuated p53 response to stresses.
Lee
Jin-Hee
JH
School of Life Sciences and Biotechnology, Korea University, Seoul, Korea.
Byun
Do-Sun
DS
Lee
Min-Goo
MG
Ryu
Byung-Kyu
BK
Kang
Min-Ju
MJ
Chae
Kwon-Seok
KS
Lee
Kil Yeon
KY
Kim
Hyo-Jong
HJ
Park
Heonyong
H
Chi
Sung-Gil
SG
D000230:Adenocarcinoma / Q000235:genetics; D000236:Adenoma / Q000235:genetics; D017209:Apoptosis; D015152:Blotting, Northern; D045744:Cell Line, Tumor; D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation; D015536:Down-Regulation; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D020868:Gene Silencing; D006222:Hamartoma / Q000235:genetics; D006801:Humans; D015151:Immunoblotting; D020287:In Situ Nick-End Labeling; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism; D014411:Neoplastic Stem Cells; D011127:Polyps / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013274:Stomach Neoplasms / Q000235:genetics*; D014183:Transplantation, Heterologous; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000235:genetics* / Q000378:metabolism
C505360:CAVIN3 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins