The emerging role of heparanase in tumor initiation, growth, metastasis, and chemoresistance is well recognized and is encouraging the development of heparanase inhibitors as anticancer drugs. Unlike the function of heparanase in cancer cells, very little attention has been given to heparanase contributed by cells composing the tumor microenvironment. Here we used a genetic approach and examined the behavior and function of macrophages isolated from wild-type (WT) and heparanase-knockout (Hpa-KO) mice. Hpa-KO macrophages express lower levels of cytokines (e.g., TNFα, IL1-β) and exhibit lower motility and phagocytic capacities. Intriguingly, inoculation of control monocytes together with Lewis lung carcinoma (LLC) cells into Hpa-KO mice resulted in nearly complete inhibition of tumor growth. In striking contrast, inoculating LLC cells together with monocytes isolated from Hpa-KO mice did not affect tumor growth, indicating that heparanase is critically required for activation and function of macrophages. Mechanistically, we describe a linear cascade by which heparanase activates Erk, p38, and JNK signaling in macrophages, leading to increased c-Fos levels and induction of cytokine expression in a manner that apparently does not require heparanase enzymatic activity. These results identify heparanase as a key mediator of macrophage activation and function in tumorigenesis and cross-talk with the tumor microenvironment.

Mounting evidence suggests that bone marrow-derived cells (BMDC) contribute to tumor growth, angiogenesis, and metastasis. In acute reactions to cancer therapy, several types of BMDCs are rapidly mobilized to home tumors. Although this host reaction to therapy can promote tumor regrowth, its contribution to metastasis has not been explored. To focus only on the effects of chemotherapy on the host, we studied non-tumor-bearing mice. Plasma from animals treated with the chemotherapy paclitaxel induced angiogenesis, migration, and invasion of tumor cells along with host cell colonization. Lesser effects were seen with the chemotherapy gemcitabine. Conditioned medium from BMDCs and plasma from chemotherapy-treated mice each promoted metastatic properties in tumor cells by inducing matrix metalloproteinase-9 (MMP9) and epithelial-to-mesenchymal transition. In mice in which Lewis lung carcinoma cells were injected intravenously, treatment with paclitaxel, but not gemcitabine or vehicle, accelerated metastases in a manner that could be blocked by an MMP9 inhibitor. Moreover, chimeric mice reconstituted with BMDC where MMP9 activity was attenuated did not support accelerated metastasis by carcinoma cells that were pretreated with chemotherapy before their introduction to host animals. Taken together, our findings illustrate how some chemotherapies can exert prometastatic effects that may confound treatment outcomes. Cancer Res; 71(22); 6986-96. Ó2011 AACR.

SummaryWhile chemotherapy strongly restricts or reverses tumor growth, the response of host tissue to therapy can counteract its anti-tumor activity by promoting tumor re-growth and/or metastases, thus limiting therapeutic efficacy. Here, we show that vascular endothelial growth factor receptor 3 (VEGFR3)-expressing macrophages infiltrating chemotherapy-treated tumors play a significant role in metastasis. They do so in part by inducing lymphangiogenesis as a result of cathepsin release, leading to VEGF-C upregulation by heparanase. We found that macrophages from chemotherapy-treated mice are sufficient to trigger lymphatic vessel activity and structure in naive tumors in a VEGFR3-dependent manner. Blocking VEGF-C/VEGFR3 axis inhibits the activity of chemotherapy-educated macrophages, leading to reduced lymphangiogenesis in treated tumors. Overall, our results suggest that disrupting the VEGF-C/VEGFR3 axis not only directly inhibits lymphangiogenesis but also blocks the pro-metastatic activity of macrophages in chemotherapy-treated mice.

Acquired resistance to therapy is a major obstacle in clinical oncology, and little is known about the contributing mechanisms of the host response to therapy. Here, we show that the proinflammatory cytokine IL1b is overexpressed in response to paclitaxel chemotherapy in macrophages, subsequently promoting the invasive properties of malignant cells. In accordance, blocking IL1b, or its receptor, using either genetic or pharmacologic approach, results in slight retardation of primary tumor growth; however, it accelerates metastasis spread. Tumors from mice treated with combined therapy of paclitaxel and the IL1 receptor antagonist anakinra exhibit increased number of M2 macrophages and vessel leakiness when compared with paclitaxel monotherapy-treated mice, indicating a prometastatic role of M2 macrophages in the IL1b-deprived microenvironment. Taken together, these findings demonstrate the dual effects of blocking the IL1 pathway on tumor growth. Accordingly, treatments using "add-on" drugs to conventional therapy should be investigated in appropriate tumor models consisting of primary tumors and their metastases. Mol Cancer Ther; 14(6); 1385-94. Ó2015 AACR.