Differential Expression of VEGFA Isoforms Regulates Metastasis and Response to Anti-VEGFA Therapy in Sarcoma.

Elevated plasma concentrations of soluble VEGFA isoforms are associated with poor prognosis in parallel with improved response to treatment with the anti-VEGFA antibody bevacizumab. To uncover the underlying mechanism to these observations, we administered anti-VEGFA therapy to mice bearing luminescent mouse fibrosarcomas expressing single VEGFA isoforms or their wild-type counterparts expressing all isoforms (fs120, fs164, fs188, or fsWT). Expression of the more soluble isoforms conferred an advantage for lung metastasis from subcutaneous tumors (fs120/164 vs. fs188/WT); fs120 cells also produced more lung colonies than fs188 cells when injected intravenously. Metastasis from subcutaneous fs120 tumors was more sensitive than fs188 to treatment with the anti-VEGFA antibody B20-4.1.1. Despite elevated plasma levels of VEGFA in fs120 tumor-bearing mice and a dependence on VEGF receptor 1 activity for metastasis to the lung, B20-4.1.1 did not affect survival in the lung on intravenous injection. B20-4.1.1 inhibited subcutaneous tumor growth and decreased vascular density in both fs120 and fs188 tumors. However, migration of fs120, but not fs188 cells, in vitro was inhibited by B20-4.1.1. The greater survival of fs120 cells in the lung was associated with VEGFR1-dependent accumulation of CD11b-positive myeloid cells and higher expression of the VEGFR1 ligand, PlGF2, by the fs120 cells in vitro and in the plasma and lungs of fs120 tumor-bearing mice. We conclude that soluble VEGFA isoform expression increases fibrosarcoma metastasis through multiple mechanisms that vary in their sensitivity to anti-VEGF/VEGFR inhibition, with VEGFA-targeted therapy suppressing metastasis through effects on the primary tumor rather than the metastatic site. Cancer Res; 77(10); 2633-46. ©2017 AACR.

Prostate cancer cells home to bone using a novel in vivo model: modulation by the integrin antagonist GLPG0187.

Micrometastasis is a barrier to the development of effective cancer therapies for prostate cancer metastasis to bone. The mechanisms remain incompletely characterised, primarily due to an inability to adequately monitor the initial metastatic events in vivo. This study aimed to establish a new model, allowing the tracking of prostate cancer cells homing to bone, and furthermore, to evaluate the response of this approach to therapeutic modulation, using the integrin antagonist GLPG0187. A single murine metatarsal was engrafted into a dorsal skinfold chamber implanted on a SCID mouse. Fluorescently-labeled human prostate (PC3-GFP) or oral (SCC4-GFP) cancer cells were administered via intracardiac (i.c) injection, with simultaneous daily GLPG0187 or vehicle-control treatment (i.p. 100 mg/kg/day) for the experimental duration. Metatarsal recordings were taken every 48 h for up to 4 weeks. Tissue was harvested and processed for microCT, multiphoton analysis, histology and immunohistochemistry. Cell viability, proliferation and migration in vitro were also quantified following treatment with GLPG0187. Metatarsals rapidly revascularised by inosculation with the host vasculature (day 5-7). PC3-GFP cells adhered to the microvascular endothelium and/or metatarsal matrix 3 days after administration, with adhesion maintained for the experimental duration. GLPG0187 treatment significantly (p < 0.05) reduced PC3 cell number within the metatarsal in vivo and reduced migration (p < 0.05) and proliferation (p < 0.05) but not cell viability in vitro. This new model allows evaluation of the early events of tumour-cell homing and localisation to the bone microenvironment, in addition to determining responses to therapeutic interventions.