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

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.

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.

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).

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.