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During the 25-year period subsequent to the Chernobyl accident, the morbidity of malignant renal tumors in Ukraine has increased from 4.7 to 10.7 per 100,000 of the total population. Recent studies of our group have shown that increases in morbidity, aggressiveness, and proliferative activity of renal cell carcinomas (RCCs), especially clear-cell renal cell carcinoma (CCRCC), in Ukrainian patients continuously inhabiting the radio-contaminated areas could be explained by specific molecular changes influenced by the so-called "chronic persistent low-dose ionizing radiation" (CPLDIR) exposure. This study aimed to examine the role of angiogenesis in CCRCC carcinogenesis associated with CPLDIR in patients living more than 20 years in cesium 137 ((137)Cs) contaminated areas after the Chernobyl accident in Ukraine. Paraffin-embedded specimens of 106 CCRCs were studied: Control cases were 18 tumors from Spanish patients (group 1), 25 tumors from Ukrainian patients from so-called clean areas without known radio-contamination (group 2), and 63 tumors from Ukrainian patients from radio-contaminated areas (group 3). For intratumoral microvessel density (MVD) determination, anti-CD31 antibody was used. A computerized image analysis program was used to quantitatively calculate the vascular density. Seventy-three percent of group 3 and 72 % of group 2 CCRCCs displayed the highest MVD. A striking increase in MVD was seen in group 3 CCRCCs, in comparison with groups 1 and 2 (p < 0.001). The majority of the hot spot vessels in group 3 was poorly differentiated. Moreover, MVD values for total vessels as well as for capillaries and tumor grade were strongly correlated. When we compared only tumor-node-metastasis tumor stages I and II, the differences remained statistically significant (p < 0.1). The ratio of the average total vessels and capillaries in the Ukrainian groups combined was 1.65:1 in comparison to the Spanish group. Our results provide evidence that CPLDIR exposure increases MVD (particularly capillary) in CCRCCs and is associated with a higher histological grade.

Previous studies have shown that during the period subsequent to the Chernobyl accident, increases in morbidity, aggressivity and proliferative activity of renal-cell carcinomas (RCCs) in Ukrainian patients were recognized. The present paper describes the molecular alterations of those tumor suppressor genes located on chromosome 9p21 ( INK4a/ARF locus and p15(INK4B)) in 26 primary renal-cell epithelial tumors from patients with different degrees of radiation exposure after the Chernobyl accident in Ukraine. Radiometric measurement of Cesium 137 ((137)Cs) was conducted with 1-day urine from all patients before surgery. Our results demonstrate that RCCs from patients living in the radio-contaminated areas showed aberrant hypermethylation of p14(ARF) and p16(INK4A) genes, associated with increased p38MAPK, p14(ARF), mdm2, cyclinD1 and Ki67 protein expression levels. Present findings show the possibility that chronic long-term low-dose radiation activates the INK4a/ARF locus, targeted by activation of the p38MAPK cascade. These actions could lead to disruptions and loss of cell cycle checkpoints and, thereby, to cellular transformation.

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.

After the Chernobyl accident, the morbidity of renal-cell carcinomas in Ukraine increased gradually from 4.7 to 7.5 per 100,000 of the total population. Cesium 137 (137Cs) is responsible for 80-90% of the internal radioactivity in people living in radiocontaminated areas of Ukraine, and 90% of 137Cs is eliminated through the kidneys. Histological and immunohistochemical study of proliferating cell nuclear antigen (PCNA) and K-ras protein was performed in peritumoral kidney tissues of 167 Ukrainian patients (groups I-III, according to varying degrees of internal exposure to radiation), and of 85 analog Spanish patients, as a control group. Our data showed in the majority of Ukrainian patients a radiation sclerosing proliferative atypical nephropathy (RSPAN) in association with an increase in the incidences of tubular epithelial nuclear atypia and carcinoma in situ (CIS). Areas of epithelial nuclear atypia and CIS of the cortex and medulla showed significant PCNA expression with means of extent as 12, 14, and 15% of stained nuclei in groups I, II, and III respectively. K-ras expression of the same areas occurred in 67, 87, and 85% of cases in groups I, II, and III respectively. The present study points to a strong relationship between the long term of low-dose radiation exposure of the Ukrainian population and the development of RSPAN as a possible precursor of malignancy. In addition, it confirms the possible initiator, promoter, or progressor role of chronic low-level radiation of renal human carcinogenesis in Ukraine.

During the 13-year period subsequent to the Chernobyl accident, the morbidity of malignant renal tumors in Ukraine has increased from 4. 7 to 7.5 per 100,000 of total population. Cesium 137 ((137)Cs) accounts for 90% of the incorporated radioactivity in the Ukrainian population, which has been exposed to long-term, low dose ionizing radiation and 90% of the more labile pool of ((137)Cs) is excreted via kidneys. The present study was performed to evaluate the histopathological features and the immunohistochemical status of proliferating cell nuclear antigen (PCNA) and K-ras in renal cell carcinomas (RCCs) of 236 Ukrainian patients (groups I to V), which represents a varying degrees of internal exposure to radiation and were operated in 2 different periods of time after the Chernobyl accident. The control group VI of 112 analog patients with RCCs was selected in Spain. The strong significant differences between the Ukrainian and Spanish groups were found in tumoral nuclear grade, in the percentage of sarcomatoid changes, the level of the peritumoral inflammatory response as well as in the peritumoral lesions. The dramatic increase of aggressivity and proliferative activity supported by strong PCNA and K-ras expression of RCCs from Ukrainian groups, associated with chronic radiation nephropathy of peritumoral kidney tissue, showed good correlation with the duration of radiation exposure and confirmed the influence of chronic but regular and sustained low dose of ionizing radiation on renal carcinogenesis of the Ukrainian population., (Copyright 2000 Wiley-Liss, Inc.)