Background: As the most abundant tumor-infiltrating immune cells, tumor-associated macrophages (TAMs) are significant for fostering tumor progression. CD68(+) TAMs display diversely polarized programs comprising CD11c(+) proinflammatory macrophages (M1) and CD206(+) immunosuppressive macrophages (M2). The aim of this study was to determine the survival impact of diametrically polarized TAMs in clear-cell renal cell carcinoma (ccRCC) and their application to stratification of patients according to their prognostic values.
Methods: The study included 185 consecutive patients with ccRCC who underwent nephrectomy between 1999 and 2001. CD68(+) total and diametrically polarized (CD11c(+) M1 and CD206(+) M2) TAM densities were assessed by immunohistochemistry, and the relationships with clinicopathologic features and prognosis were evaluated.
Results: Low CD11c(+) TAM density and high CD206(+) TAM density were associated with reduced cancer-specific survival (P = 0.043 and P = 0.017, respectively), whereas CD68(+) TAM density only had borderline prognostic significance (P = 0.062). Furthermore, combined analysis of CD11c(+) and CD206(+) TAMs (CD11c/CD206 signature) had a better power to predict patients' outcome (P = 0.010). Together with TNM stage, tumor necrosis, and performance status, CD11c/CD206 signature was an independent prognostic factor (P = 0.010). When applied to the University of California Integrated Staging System intermediate-/high-risk group for localized ccRCC, CD11c/CD206 signature could further distinguish patients with dismal prognosis (P = 0.004).
Conclusions: Intratumoral balance of diametrically polarized TAMs is a novel independent predictor for survival in patients with ccRCC. Tipping the balance toward an antitumoral phenotype might be a promising target of postoperative adjuvant therapy.