Supplementary Material for: High Expression of Major Histocompatibility Complex Class I in Clear Cell Renal Cell Carcinoma Is Associated with Improved Prognosis

Introduction: In this study we analyzed major histocompatibility complex class I (MHCI) expression as a potential prognostic immune marker for patients with clear cell renal cell carcinoma (ccRCC). Patients and Methods: 34 patients with localized ccRCC (pT1-pT3) who had undergone nephrectomy and had at least 4 years of clinical follow-up data were included in the study. Immunohistochemical staining for MHCI was performed on tumor sections. An automated image analysis algorithm was applied to representative tumor areas to quantitate the proportion of stained pixels (positivity score = positive pixels/total pixels) on scanned digital slides. Results: At the end of the study, the patients who were alive had increased MHCI expression (mean positivity score 0.80) compared to those who died of the disease (mean positivity score 0.53; p < 0.0001, t test). Patients who were alive with recurrence had increased MHCI expression (positivity score 0.81) compared to those who succumbed to their disease recurrence (positivity score 0.53; p < 0.0001, t test). Survival was higher among patients with high MHCI expression compared to patients with low MHCI expression (p < 0.0001, Mantel-Cox). Conclusions: With an automated high-throughput image analysis technique, this study shows that higher tumor cell MHCI expression promotes increased survival and reduced incidence of recurrence compared to patients with lower tumor cell MHCI expression.