p16INK4A and p15INK4B Gene Alteration Associated with Oxidative Stress in Renal Cell Carcinomas After the Chernobyl Accident (Pilot Study)

Abstract

Our study was undertaken to better understand the role of G1/S transition abnormalities in the malignant progression of renal cell carcinomas (RCCs), exposed to long-term low doses of ionizing radiation (IR), from patients living in radiocontaminated areas of the Ukraine after the Chernobyl accident. We studied p16 and p15 gene alteration in association with oxidative stress markers, including inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX2). We analyzed 88 samples collected from 22 patients with RCCs and with different exposure to IR. Homozygous deletion of the p16 and p15 genes, as well as hypermethylation of the 5CpG island in the promoter region of the same genes, were analyzed by differential PCR and Methylation-Specific PCR respectively, in association with histopathology and immunohistochemical analysis of p16 and p15 proteins. COX2 and iNOS expression in the same tumors were likewise analyzed. Aberrant hypermethylation was observed in 7 (32%) and 5 (23%) cases accompanied, by immunohistochemical loss of expression for p16 and p15 genes respectively, in both high stage and grade tumors from patients living in radiocontaminated areas, this being especially outstanding for the p16 gene. An association with COX2 and less iNOS overexpression in the same tumors was observed. Our data suggest that inactivation of p16 gene, but not p15, induced by increased oxidative stress generated by persistent chronic exposure to IR, could be one of the major pathways responsible for RCCs malignant progression.

Quantitative Detection of Promoter Hypermethylation of Multiple Genes in the Tumor, Urine, and Serum DNA of Patients with Renal Cancer

“…QMSP may be more sensitive than conventional MSP but varies based on the tested promoter, primers, and PCR conditions. On the basis of conventional MSP, methylated p16 alleles in the primary renal cell carcinoma were detected from 20 -32% (8). In the present study, p16 was methylated in 35% of primary tumors and in 67% and 50% of matched urine and serum samples, respectively.…”

Methylation of the p16INK4a promoter region in telomerase immortalized human keratinocytes co-cultured with feeder cells

“…Culture of TERT-transduced human cells in more physiologic oxygen conditions may also reduce the necessity for p16 downregulation and reduce the incidence of epigenetic mutations in tumor suppressor genes. This strategy may be particularly relevant to p16 mutations since several studies have found an association between increased levels of reactive oxygen species and p16 methylation during tumor progression (Govindarajan et al, 2002;p16 INK4a Methylation in TERT immortalized keratinocytes BW Darbro et al Romanenko et al, 2002;Jarmalaite et al, 2003). Other studies have shown that oxygen accelerates accumulation of mutations and may even promote telomere attrition, thus providing further impetus to perform immortalization experiments in low oxidative stress conditions.…”

Epigenomics in Environmental Health

“…In human lung adenocarcinoma, CDKN2A methylation occurred more often in workers compared to non-worker controls of the Russian MAYAK weapons-grade plutonium plant, and the prevalence of this methylation exhibited a dose–response with radiation internal exposure dose (Belinsky et al, 2004). Methylation of CDKN2A has also been linked to reactive oxygen species produced by radiation exposures (Romanenko et al, 2002), and murine models of radiation-induced lymphoma have also demonstrated hypermethylation of Cdkn2b (encoding p15ink4b (Malumbres et al, 1997, 1999; Cleary et al, 1999)).…”