M2-macrophage infiltration and macrophage traits of tumor cells in urinary bladder cancer.

BACKGROUND: Tumor-associated macrophages (TAMs) constitute a subset of nonneoplastic cells in tumor stroma and influence cancer progression in solid tumors. The clinical significance of TAMs in urinary bladder cancer (UBC) is controversial.

METHODS: We prospectively studied 103 patients with stage pT1-T4 UBC treated with cystectomy and pelvic lymph node dissection. Tumor sections were immunostained with M2-specific macrophage marker CD163 and proliferation marker Ki-67. The expression of these markers in cancer cells as well as macrophage infiltration (MI) in tumor stroma was analyzed in relation to clinical data and outcome.

RESULTS: The mean rate of CD163 and Ki-67 expressed by cancer cells were 35% and 78%, respectively. With borderline significance, MI was associated with lower rate of lymph node metastasis (P = 0.06). CD163 expression in cancer cells was proportional to MI (P<0.014). Patients with CD163-positive tumors and strong MI had significantly longer cancer-specific survival (CSS) (76 months), compared to patient with CD163-positive tumors and weak MI (28 months) (P = 0.02).

CONCLUSIONS: M2-specific MI tends to be inversely correlated with LN metastasis and improved CSS in UBC. MI might have protective impact in CD163-positive tumors. Expression of CD163 in cancer cells is significantly correlated with MI and might have a tumor promoting impact.