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Repression of MAL tumour suppressor activity by promoter methylation during cervical carcinogenesis
Author(s) -
Overmeer Renée M,
Henken Florianne E,
Bierkens Mariska,
Wilting Saskia M,
Timmerman Ilse,
Meijer Chris JLM,
Snijders Peter JF,
Steenbergen Renske DM
Publication year - 2009
Publication title -
the journal of pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.964
H-Index - 184
eISSN - 1096-9896
pISSN - 0022-3417
DOI - 10.1002/path.2598
Subject(s) - methylation , carcinogenesis , gene silencing , dna methylation , biology , cancer research , microbiology and biotechnology , promoter , transfection , ectopic expression , gene expression , cell culture , cancer , gene , genetics
We recently identified MAL (T‐lymphocyte maturation associated protein) as the most down‐regulated gene in cervical oncogenesis. Here, we examined the mechanism underlying MAL silencing, its functional role in cervical carcinogenesis, and the relevance of detecting MAL alterations for risk assessment of hrHPV‐positive women. MAL mRNA expression and promoter methylation were analysed in primary keratinocytes, hrHPV‐immortalized keratinocytes, cervical cancer cell lines, biopsies, and scrapings by quantitative (methylation‐specific) PCR. SiHa cells were transfected with MAL cDNA and assayed for proliferation, migration, and anchorage‐independent growth. MAL mRNA was (nearly) undetectable in all HPV‐immortalized and cervical cancer cells, but could be up‐regulated upon methylation inhibition. MAL promoter methylation at two promoter regions (M1 and M2) was detected in all HPV‐immortalized cells and cancer cells. Ectopic expression of MAL in SiHa cells suppressed proliferation, migration, and anchorage‐independent growth. None (0/22) of normal cervical biopsies, 9% (6/66) of CIN1 lesions, 53% (34/64) of CIN3 lesions, 90% (85/94) of cervical squamous cell carcinomas (SCCs), and 93% (26/28) of cervical adenocarcinomas (AdCAs) demonstrated MAL promoter methylation at both promoter regions. Moreover, detection of MAL promoter methylation in cervical scrapings was predictive for underlying high‐grade lesions. Both in biopsies and in scrapings, MAL promoter methylation was significantly correlated with reduced mRNA expression. MAL gene silencing by promoter methylation is a frequent and biologically essential event in HPV‐induced cervical carcinogenesis. Hence, MAL promoter methylation and/or mRNA expression analysis on cervical scrapings may provide a valuable diagnostic tool to improve the detection of CIN3, SCC, and AdCA. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.