Abstract B83: Multikinase inhibitors for antiangiogenesis and tumor metastasis in zebrafish model

Tumor metastasis is a central issue in the treatment of malignancies, and metastases rather than the primary tumor contributes to about 90% of cancer-related deaths. Current therapies for solid tumors focus on preventing the development of blood vessels supplying nutrients to the tumor; however, metastasis to distant organs leads to relapse and patient mortality and resistance to treatment often results in disease progression. The host microenvironment is a critical regulator of cancer progression because the normal vascular endothelium, unlike the tumor cells, does not carry mutations, which potentially facilitates a clinical response to anti-angiogenesis therapeutic agents. Macrophages and neutrophils play a critical role in this process since macrophage plasticity results in the expression of genes which can switch the macrophage ‘type’ to one which enhances tumor metastasis. Thus, it is beneficial to target immune cells and change their gene expression profile such that they become beneficial to the host and prevent metastasis. The vascular endothelial growth factor (VEGF) pathway is central to regulating angiogenesis and metastasis. The VEGF blocking antibody, bevacizumab and small molecules that inhibit receptor tyrosine kinases including the VEGF receptor, sunitinib and sorafenib, have prolonged lives of cancer patients in the clinic; however, their long term effects in patients is unknown. Based on preclinical mouse model studies indicating that the “anti-angiogenesis” agent sunitinib increased tumor metastases, the anti-angiogenesis approach in cancer has acquired a controversial “paradigm” that anti-angiogenesis therapy can lead to harmful effects on tumor growth and metastasis. This highlights the urgency of unraveling the molecular and cellular mechanism of action of anti-angiogenesis agents on tumor growth and metastasis. Zebrafish/tumor xenograft model is a live, complex, 3-dimensional tumor xenograft animal model allows the continuous delivery of tumor angiogenic factors and includes the participation of host stroma and vasculature in the cellular and molecular events contributing to tumor invasion and metastasis; thus mimicking the host disease. The zebrafish model facilitates the high-throughput manipulation of the host environment using morpholino knockdown of genes and small molecule inhibitors to block tumor angiogenesis. Zebrafish neoplasms induced by carcinogens or oncogenes recapitulate the human disease at the histological, molecular and pathological levels. Moreover, the similarity in gene-expression profile was consistent between zebrafish and human cancer, supporting its use as a model for human tumors. The zebrafish xenograft does not need treatment with immunosuppressive drugs prior to the xenograft, the neo-vascularization can be seen within 24 hours and metastasis can be detected within 6 days of tumor cell transplantation. Recently it was also demonstrated that neutrophils mediated enhanced metastasis in zebrafish/breast cancer xenograft after treatment with sunitinib and macrophages changed their phenotype in response to treatment. Here we determined if specific VEGF inhibitors block tumor angiogenesis without induction of tumor metastasis. Sunitinib is an “anti-angiogenesis” agent acting as a multikinase inhibitor that selectively targets the VEGF receptors but also inhibits PDGFR and KIT. Although sunitinib effectively inhibits neovascularization, it also increased local invasion and distant metastasis in pancreatic neuroendocrine carcinoma and glioblastoma in a mouse xenograft model. In addition, accelerated metastasis of breast cancer and melanoma was observed after short-term treatments with sunitinib, even though it exhibited a potent inhibition of tumor angiogenesis. As with the mouse studies, our zebrafish/tumor xenograft studies demonstrated that sunitinib efficiently suppresses angiogenesis and promotes tumor metastasis. Subsequently, we identified another small molecule multikinase inhibitor, which, like sunitinib, selectively blocks VEGFRs (as well as inhibits PDGFR and KIT), but produces an opposite outcome with respect to metastasis. In our zebrafish/tumor model transplanted with human prostate, lung or pancreatic cancer cells, this newly identified multikinase inhibitor efficiently blocks angiogenesis and effectively suppresses tumor metastasis. This new data promises to shift the current anti-angiogenesis “paradigm” that all anti-angiogenesis agents promote tumor metastasis. Therefore, we argue that different small molecule inhibitors of angiogenesis can successfully target angiogenesis and block metastasis at the same time. Potential stromal-epithelial interactions essential for cancer progression and metastasis through these inhibitors include pathways regulating angiogenesis, hypoxia, inflammation and metastasis. Our data suggest that the mechanism by which two similar receptor tyrosine kinase inhibitors produce the same effect on anti-angiogenesis but have very different outcomes in tumor metastasis by modulating these pathways. Citation Format: Karine F. Ferri-Lagneau, Jamil Haider, TinChung leung. Multikinase inhibitors for antiangiogenesis and tumor metastasis in zebrafish model. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr B83.