15648 Background: Combinations of cytotoxic drugs lead to increased activity and minimize resistance compared to single agents in tumor therapy. Similarly, antiangiogenic treatment could be improved by combinations targeting different pathways. We investigated a combination of endogenous inhibitors using endostatin (ES), soluble Neuropilin-1 (sNP-1), and thrombospondin-2 (TSP-2) in a model of renal cell carcinoma. Methods: Porcine aortic endothelial cells have been engineered for stable production of angiogenic inhibitors by lipofection and were encapsulated in sodium alginate microbeads. Proliferation of human umbilical vein endothelial cells or Renca renal carcinoma cells was examined after incubation with different microbeads. Similarly, effects of inhibitors on endothelial cell function were tested in tube formation and in vitro wound assays. Microbeads were implanted into SCID mice with subcutaneously growing tumors derived from Renca cells or in mice developing lung metastases after intravenous injection of tumor cells. Results: Factors released from microbeads inhibited endothelial cell function but had no effect on tumor cell proliferation in vitro. In vivo, subcutaneous tumor growth was inhibited similarly by each angiogenic inhibitor alone. After 30 days mean tumor weight was 1.3 g in controls and 0.17, 0.18, 0.18g in ES, sNP-1, and TSP-2 treated mice, respectively. Tumor weight in mice treated with all three inhibitors was further reduced to 0.03g. Histological analyses confirmed antiangiogenic activity by inhibition of microvessel density in treated tumors. In a metastastic model treatment with angiogenic inhibitors induced a significant reduction in size and number of lung metastases with additive effects when factors were used in combination. Conclusions: We conclude that combination therapy targeting multiple angiogenic pathways has synergistic activity and could help to avoid resistance to single inhibitors in tumor treatment. No significant financial relationships to disclose.
In vitro effects of waterpipe smoke condensate on endothelial cell function: A potential risk factor for vascular disease