Abstract 4380: Effect of sunitinib on endothelial-pericyte cell interaction

Background: Sunitinib is a multitargeted tyrosine kinase receptor inhibitor, which has been used for the last 5 years as an anti-angiogenic drug for the treatment of metastasic renal cell carcinoma (RCC). Sunitinib treatment induces an initial favorable response in patients with RCC, however, resistant to sunitinib occurs in the majority of patients after ∼11 months of treatment. One of the mechanism that has been hypothesized to explain the resistance of RCC to sunitinib is an increase in pericyte cell coverage in the tumor vasculature. In vivo, pericytes and endothelial cells are in close proximity and they frequently have direct contact with each other through gap junctions. Endothelial-pericytes interactions regulate vascular development, endothelial cell permeability, vessel stabilization, vessel maturation, and remodeling. Moreover, pericytes have been demonstrated to secrete paracrine factors that stimulate signaling pathways implicated in endothelial cell differentiation and survival. Previous studies have shown that anti-angiogenic drugs may disrupt the physical interaction between endothelial cells and pericytes in vivo. Moreover, in vitro studies have demonstrated that the loss of endothelial-pericyte contact may decrease the level of expression of SMA and NG2, the two most important pericyte markers used in vivo. The aim of this study is to analyze the endothelial-pericyte cell interactions in vitro and the effect that sunitinib has in these interactions. Methods and Results: HUVEC (Human Umbilical Vein Endothelial Cells) and hPC-PL (Human Pericytes from Placenta) cells were utilized to characterize in vitro the effect of sunitinib in endothelial-pericyte cell interactions. The effect of sunitinib in cell proliferation of each primary culture was determined by using crystal violet and growth curve assays. Sunitinib, at 1uM concentration, decreases proliferation rate of endothelial and pericyte cells, process that was reversible after sunitinib withdrawal. Cocultures of HUVEC and hPC-PL cells showed that both cells types start to physically interact after 24 hours. After 48 hours of co-culture, hPC-PL cells in close proximity to endothelial cells overexpressed the pericyte markers NG2 and SMA, process that have been reported to be dependent on gap junction formation. Use of conditioned media obtained from endothelial cells did not induce overexpression of NG2 or SMA in hPC-PL cells, which suggests physical contact between pericyte and endothelial cells was necessary for pericyte to over-express NG2 and SMA. In addition, co-culture experiments performed in the presence of sunitinib did not affect the physical cell-to-cell interaction between HUVEC and hPC-PL. Conclusion: These results indicate endothelial-pericyte cell interactions are not only an important mechanism for endothelial survival signaling, but also are necessary to maintain pericyte differentiation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4380. doi:1538-7445.AM2012-4380