Combined Blockade of Integrin-α4β1 Plus Cytokines SDF-1α or IL-1β Potently Inhibits Tumor Inflammation and Growth

Tumor-associated macrophages promote tumor growth by stimulating angiogenesis and suppressing antitumor immunity. Thus, therapeutics that inhibit macrophage recruitment to tumors may provide new avenues for cancer therapy. In this study, we showed how chemoattractants stromal cell-derived growth factor 1 alpha (SDF-1 alpha) and interleukin 1 beta (IL-1 beta) collaborate with myeloid cell integrin-alpha 4 beta 1 to promote tumor inflammation and growth. We found that SDF-1 alpha and IL-1 beta are highly expressed in the microenvironments of murine lung, pancreatic, and breast tumors; surprisingly, SDF-1 alpha was expressed only by tumor cells, whereas IL-1 beta was produced only by tumor-derived granulocytes and macrophages. In vivo, both factors directly recruited proangiogenic macrophages to tissues, whereas antagonists of both factors suppressed tumor inflammation, angiogenesis, and growth. Signals induced by IL-1 beta and SDF-1 alpha promoted the interaction of talin and paxillin with the cytoplasmic tails of integrin-alpha 4 beta 1, thereby stimulating myeloid cell adhesion to endothelium in vitro and in vivo. Inhibition of integrin-alpha 4 beta 1, SDF-1 alpha, or IL-1 beta was sufficient to block tumor inflammation and growth, and the combined blockade of these molecules greatly accentuated these effects. Furthermore, antagonists of integrin-alpha 4 beta 1 inhibited chemotherapy-induced tumor inflammation and acted synergistically with chemotherapeutic agents to suppress tumor inflammation and growth. These results show that targeting myeloid cell recruitment mechanisms can be an effective approach to suppress tumor progression. Cancer Res; 71(22): 6965-75. (C)2011 AACR.