Background Little is known about epigenetic silencing of genes by promoter hypermethylation in renal cell carcinoma (RCC). The aim of this study was to identify prognostic methylation markers in surgically treated clear cell RCC (ccRCC). Methods Methylation patterns were assayed using the Infinium HumanMethylation450 BeadChip array on pairs of ccRCC and normal tissue from 12 patients. Using quantitative PSQ analysis, tumor-specific hypermethylated genes were validated in 25 independent cohorts and their clinical relevance was also verified in 152 independent cohorts. Results Using genome-wide methylation array, Zinc finger protein 278 ( ZNF278 ), Family with sequence similarity 155 member A ( FAM155A ) and Dipeptidyl peptidase 6 ( DPP6 ) were selected for tumor-specific hypermethylated genes in primary ccRCC. The promoter methylation of these genes occurred more frequently in ccRCC than normal kidney in independent validation cohort. The hypermethylation of three genes were associated with advanced tumor stage and high grade tumor in ccRCC. During median follow-up of 39.2 (interquartile range, 15.4–79.1) months, 22 (14.5%) patients experienced distant metastasis. Multivariate analysis identified the methylation status of these three genes, either alone, or in a combined risk score as an independent predictor of distant metastasis. Conclusion The promoter methylation of ZNF278 , FAM155A and DPP6 genes are associated with aggressive tumor phenotype and early development of distant metastasis in patients with surgically treated ccRCC. These potential methylation markers, either alone, or in combination, could provide novel targets for development of individualized therapeutic and prevention regimens.
Purpose P21-activated kinase 4 (PAK4), a serine/threonine kinase that regulates a number of fundamental cellular processes, has been suggested as a prognostic factor for various human tumors. The aim of the present study was to evaluate the clinical implications of phospho-Ser474 PAK4 (pPAK4 S474 ), an activated form of PAK4, in surgically treated renal cell carcinoma (RCC). Materials and Methods Samples from 131 patients with surgically treated RCC were immunostained to detect PAK4 and pPAK4 S474 . Expression of PAK4 and pPAK4 S474 was compared with clinicopathological characteristics and survival after nephrectomy. Results PAK4 and pPAK4 S474 were expressed predominantly in the nucleus. Overall, 57.3% (75/131) and 24.4% (29/119) of specimens exhibited high expression of pPAK4 S474 and PAK4, respectively. High expression of pPAK4 S474 was associated with adverse pathologic characteristics, including advanced tumor stage and grade (p=0.036 and p=0.002, respectively), whereas this association was not significant for PAK4 expression (each p>0.05). Kaplan-Meier estimates showed that high expression of pPAK4 S474 was associated with shorter recurrence-free survival in a subgroup with localized RCC and with cancer-specific survival in the total RCC cohort (log-rank test: p=0.001 and p=0.005, respectively), whereas PAK4 expression was not. Multivariate Cox regression analysis identified that high pPAK4 S474 expression was an independent predictor of recurrence in the subgroup with localized RCC. Conclusions pPAK4 S474 may be a more accurate prognostic factor than total PAK4 in RCC patients. This marker would be useful for identifying patients with pathologically localized disease who may require further interventions.
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