title: Downregulation and aberrant promoter methylation of p16INK4A: a possible novel heritable susceptibility marker to retinoblastoma.
abstract: 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.
authors.affiliation: Department of Human Pathology and Oncology, University of Siena, Siena, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Indovina
authors.forename: Antonio
authors.initials: A
authors.lastname: Acquaviva
authors.forename: Giulia
authors.initials: G
authors.lastname: De Falco
authors.forename: Valeria
authors.initials: V
authors.lastname: Rizzo
authors.forename: Anna
authors.initials: A
authors.lastname: Onnis
authors.forename: Anna
authors.initials: A
authors.lastname: Luzzi
authors.forename: Francesca
authors.initials: F
authors.lastname: Giorgi
authors.forename: Theodora
authors.initials: T
authors.lastname: Hadjistilianou
authors.forename: Paolo
authors.initials: P
authors.lastname: Toti
authors.forename: Valentina
authors.initials: V
authors.lastname: Tomei
authors.forename: Francesca
authors.initials: F
authors.lastname: Pentimalli
authors.forename: Alessandro
authors.initials: A
authors.lastname: Carugi
authors.forename: Antonio
authors.initials: A
authors.lastname: Giordano
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000032:analysis / Q000235:genetics*; D019175:DNA Methylation; D015536:Down-Regulation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D020022:Genetic Predisposition to Disease; D006801:Humans; D007150:Immunohistochemistry; D007223:Infant; D008297:Male; D010375:Pedigree; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D012313:RNA / Q000032:analysis; D019572:Retinal Neoplasms / Q000737:chemistry / Q000235:genetics* / Q000473:pathology; D012175:Retinoblastoma / Q000737:chemistry / Q000235:genetics* / Q000473:pathology; D016160:Retinoblastoma Protein / Q000032:analysis; D050717:Retinoblastoma-Like Protein p130 / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012307:Risk Factors
chemical_list: D014408:Biomarkers, Tumor; D019941:Cyclin-Dependent Kinase Inhibitor p16; C493837:RBL2 protein, human; D016160:Retinoblastoma Protein; D050717:Retinoblastoma-Like Protein p130; D012313:RNA