Macrophage infiltration in human non-small-cell lung cancer: the role of CC chemokines

Bronchogenic carcinoma is the leading cause of malignancy-related mortality in the United States, with an overall 5-year survival rate of less than 15 %. This aggressive behavior reflects, among other traits, the capacity of t he tumor to evade normal host immune defenses, and to induce a pro-angiogen ic environment. A central feature of any immune response toward tumors is t he recruitment of specific immune cell populations. In the present study we investigated the infiltration of monocytes in human specimens of non-small -cell lung cancer (NSCLC). The presence of macrophages in NSCLC tumors was documented by immunohistochemistry. In vitro chemotaxis assays demonstrated higher monocyte chemotactic activity in NSCLC tumor homogenates than in no rmal lung tissue. We next investigated the expression of CC chemokines with in specimens of NSCLC tumors. Levels of the CC chemokines were higher in NS CLC tumor tissue than in normal lung tissue. Immunolocalization showed that the cells associated with antigenic CC chemokines were the malignant tumor cells, as well as occasional stromal cells. Maximal inhibition of monocyte chemotaxis induced by NSCLC in vitro occurred in the presence of neutraliz ing antibodies to MCP-1 and MIP-1 beta. On follow-up of 15 patients in whom we quantified macrophage infiltration, we found that those with recurrence of disease had higher levels of macrophage infiltration in their initial t umors. However, the functional significance of CC-chemokine-mediated macrop hage infiltration into NSCLC remains to be determined.