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Downregulation and aberrant promoter methylation of p16INK4A : A possible novel heritable susceptibility marker to retinoblastoma
Author(s) -
Indovina Paola,
Acquaviva Antonio,
De Falco Giulia,
Rizzo Valeria,
Onnis Anna,
Luzzi Anna,
Giorgi Francesca,
Hadjistilianou Theodora,
Toti Paolo,
Tomei Valentina,
Pentimalli Francesca,
Carugi Alessandro,
Giordano Antonio
Publication year - 2010
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.22019
Subject(s) - retinoblastoma , downregulation and upregulation , methylation , dna methylation , cancer research , demethylating agent , biology , tumor suppressor gene , promoter , cancer , gene , genetics , gene expression , carcinogenesis
RB loss has long been recognized as the causative genetic alteration underlying retinoblastoma but it is increasingly evident that other alterations are required for the tumor to develop. Therefore, we set out to identify additional inheritable susceptibility markers and new potential preventive and therapeutic targets for retinoblastoma. We focused on the p16INK4A tumor suppressor gene because of its possible role in retinoblastoma pathogenesis and its involvement in predisposition to familial cancer. p16INK4A expression was analyzed in tumor samples from retinoblastoma patients by immunohistochemistry and in peripheral blood cells from both patients and their parents by real‐time quantitative reverse transcription‐PCR (qRT‐PCR). Since promoter methylation is a common mechanism regulating p16INK4A expression, the methylation status of its promoter was also analyzed in blood samples from patients and their parents by methylation‐specific PCR. A downregulation of p16INK4A was observed in 55% of retinoblastoma patients. Interestingly, in 56% of the cases showing p16INK4A downregulation at least one of the patients' parents bore the same alteration in blood cells. Analysis of p16INK4A promoter methylation showed hypermethylation in most patients with p16INK4A downregulation and in the parents with the same alteration in p16INK4A expression. The finding that p16INK4A was downregulated both in patients and their parents suggests that this alteration could be a novel inheritable susceptibility marker to retinoblastoma. The observation that p16INK4A downregulation seems to be due to its promoter hypermethylation opens the way for the development of new preventive and therapeutic strategies using demethylating agents. J. Cell. Physiol. 223: 143–150, 2010. © 2009 Wiley‐Liss, Inc.