Major histocompatibility complex class I (MHC 1) expression in clear cell renal cell carcinoma: Correlation with clinical outcome.

Abstract

541 Background: Most patients with clear cell renal cell carcinoma (ccRCC) initially present with localized disease but a fraction subsequently develop metastases. Current predictive models of ccRCC recurrence are imperfect, suggesting a need for additional predictors. Metastatic ccRCC may be modulated by the immune system, suggesting that the immune system plays a role in tumor progression. Major histocompatibility complex class I (MHC I) expression on tumor cells is critical for immune system recognition. Here, we analyzed MHC I expression in ccRCC and its correlation with clinical outcomes. Methods: ccRCC patients who underwent radical nephrectomy with a ≥4 years of follow-up, without T4 disease or metastasis at presentation were included. All slides were re-reviewed by a single Urologic Pathologist and blocks with tumor and adjacent renal parenchyma were selected for each case for immunohistochemical staining for MHC I . Whole slide scanning and automated image analysis was used; representative areas of tumor and normal kidney were selected and averaged with Aperio image analysis software (positive pixel count v. 9). Unpaired t-test and one-way ANOVA were performed in GraphPad Prism. Results: 34 patients were analyzed. Fuhrman nuclear grades (FNG) were: FNG 2 10/34 (29%), FNG 3 20/34 (59%) and FNG 4 4/34 (11%). Although there was no correlation with FNG and MHC1 (ANOVA, p=0.800), patients who were alive at follow up had increased MHCI expression (80.1% average positivity score) than those who died (53% average positivity score; t-test, p<0.0001). Patients living with recurrence had increased MHCI expression (81.3% positivity score) compared to those who succumbed to their disease (53.2% positivity score; t-test, p<0.0001). Conclusions: MHCI expression may be an important prognostic factor in ccRCC for recurrence free survival, and also for prognosis of those patients with recurrence. This is the first study to show that increased MHCI expression is a favorable prognostic indicator in metastatic ccRCC. These results suggest that MHCI expression plays an important role in tumor-host immune system interaction of ccRCC and merits further study.