Clodronate inhibits tumor angiogenesis in mouse models of ovarian cancer.

PURPOSE: Bisphosphonates have been shown to inhibit and deplete macrophages. The effects of bisphosphonates on other cell types in the tumor microenvironment have been insufficiently studied. Here, we sought to determine the effects of bisphosphonates on ovarian cancer angiogenesis and growth via their effect on the microenvironment, including macrophage, endothelial and tumor cell populations. EXPERIMENTAL DESIGN: Using in vitro and in vivo models, we examined the effects of clodronate on angiogenesis and macrophage density, and the overall effect of clodronate on tumor size and metastasis. RESULTS: Clodronate inhibited the secretion of pro-angiogenic cytokines by endothelial cells and macrophages, and decreased endothelial migration and capillary tube formation. In treated mice, clodronate significantly decreased tumor size, number of tumor nodules, number of tumor-associated macrophages and tumor capillary density. CONCLUSIONS: Clodronate is a potent inhibitor of tumor angiogenesis. These results highlight clodronate as a potential therapeutic for cancer.

Notch3 pathway alterations in ovarian cancer.

The Notch pathway plays an important role in the growth of high-grade serous ovarian (HGS-OvCa) and other cancers, but its clinical and biologic mechanisms are not well understood. Here, we found that the Notch pathway alterations are prevalent and significantly related to poor clinical outcome in patients with ovarian cancer. Particularly, Notch3 alterations, including amplification and upregulation, were highly associated with poor patient survival. Targeting Notch3 inhibited ovarian cancer growth and induced apoptosis. Importantly, we found that dynamin-mediated endocytosis was required for selectively activating Jagged-1-mediated Notch3 signaling. Cleaved Notch3 expression was the critical determinant of response to Notch-targeted therapy. Collectively, these data identify previously unknown mechanisms underlying Notch3 signaling and identify new, biomarker-driven approaches for therapy.

Cross-talk between EphA2 and BRaf/CRaf is a key determinant of response to Dasatinib.

PURPOSE: EphA2 is an attractive therapeutic target because of its diverse roles in cancer growth and progression. Dasatinib is a multikinase inhibitor that targets EphA2 and other kinases. However, reliable predictive markers and a better understanding of the mechanisms of response to this agent are needed. EXPERIMENTAL DESIGN: The effects of dasatinib on human uterine cancer cell lines were examined using a series of in vitro experiments, including MTT, Western blot analysis, and plasmid transfection. In vivo, an orthotopic mouse model of uterine cancer was utilized to identify the biologic effects of dasatinib. Molecular markers for response prediction and the mechanisms relevant to response to dasatinib were identified by using reverse phase protein array (RPPA), immunoprecipitation, and double immunofluorescence staining. RESULTS: We show that high levels of CAV-1, EphA2 phosphorylation at S897, and the status of PTEN are key determinants of dasatinib response in uterine carcinoma. A set of markers essential for dasatinib response was also identified and includes CRaf, pCRaf(S338), pMAPK(T202/Y204) (mitogen-activated protein kinase [MAPK] pathway), pS6(S240/244), p70S6k(T389) (mTOR pathway), and pAKT(S473). A novel mechanism for response was discovered whereby high expression level of CAV-1 at the plasma membrane disrupts the BRaf/CRaf heterodimer and thus inhibits the activation of MAPK pathway during dasatinib treatment. CONCLUSIONS: Our in vitro and in vivo results provide a new understanding of EphA2 targeting by dasatinib and identify key predictors of therapeutic response. These findings have implications for ongoing dasatinib-based clinical trials.