CD47 Expression Predicts Unfavorable Prognosis in Clear Cell Renal Cell Carcinoma after Curative Resection

The role of CD47 expression as a ‘do not eat me’ signal that inhibits phagocytosis of tumor cells by macrophages is well established. Immune checkpoint therapy that targets CD47 has been successful in preclinical trials and is currently undergoing clinical investigation for various human malignancies. Here, the clinicopathological correlation with CD47 expression in clear cell renal cell carcinoma (ccRCC) was explored. CD47 expression was evaluated by immunohistochemical staining in tissue microarray sections of 235 ccRCC tissues. CD47 expression was observed in 28 (11.9%) of 235 ccRCC tissues and was significantly associated with higher WHO/ISUP grade (p = 0.001), frequent lymphovascular invasion (p = 0.036), frequent renal vein thrombus (p = 0.018), frequent sinus fat invasion (p = 0.004), frequent sarcomatous change (p = 0.001), higher pT stage (p = 0.002), higher pN stage (p = 0.002), higher pM stage (p < 0.001), and advanced American Joint Committee on Cancer stage (p = 0.002). In the survival analyses, positive CD47 expression was associated with cancer-specific survival (p = 0.003). However, positive CD47 expression was not associated with recurrence-free survival. In conclusion, CD47 expression was associated with adverse clinicopathological parameters and cancer-specific survival in patients with ccRCC.