Estrogenic chemicals have been shown to increase the expression of the growth factor VEGF in breast cancer cells. Hence, there is some concern that environmental exposure to estrogenic chemicals such as polychlorinated biphenyls (PCBs) may excacerbate the growth of breast cancer via angiogenesis. Highly metastatic breast cancer cells exposed to PCB153 have been reported to produce a significantly greater amount of ROS compared to non-metastatic breast cancer cells. A number of paracrine effects have been reported in tumors exposed to estrogen, however, the role of estrogen-induced ROS in signaling tumor angiogenesis remains to be defined. We previously reported that PCB-induced angiogenesis can be blocked by

Pyk2 siRNA. Therefore, the goal of this study was to determine whether Pyk2 small molecule inhibitors block PCB-induced vascularization in a 3-D breast tumor model. Human umbilical vein endothelial cells (HUVEC) or brain microvascular endothelial cells (hCMEC/D3) were used to study the effect of small molecule inhibitors. The effect of Pyk2 inhibition on breast tumor spheroid angiogenesis was tested in a 3-D co-culture of MDA-MB-231 breast cancer cells. MDA-MB-231 cells exposed to PCB153 produced ROS most likely H2O2; therefore we determined whether external H2O2 exposure increased DNA synthesis of vascular endothelial cells. Our results showed a significant increase in DNA synthesis from exposure to H2O2 for

18hrs. Breast tumor spheroids treated with PF431396 or Pyk2 siRNA showed a significant reduction in microvessel sprouting and length when compared to control. Confocal microscopy of endothelial cells co-cultured with smooth muscle cells and fibroblasts further showed a significant increase in endothelial cell branching when exposed to PCB153. The effects of PCB153 on endothelial cells in co-culture were inhibited by treatments with the ROS scavenger

N-acetylcysteine. We have provided evidence for the role of Pyk2 redox signaling in the aggressive angiogenic phenotype of endothelial cells. Our results suggest that metastatic breast cancer cells exposed to PCBs release ROS that may directly activate the redox sensitive kinase Pyk2 in neighboring endothelial cells. Consequently, Pyk2 redox signaling in neighboring endothelial cells may promote the aggressive spread of breast cancer.

Citation Format: Jayanta K. Das, Quentin H. Felty. PCB153-induced angiogenesis depends on redoxsensitive Pyk2 signaling. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3899. doi:10.1158/1538-7445.AM2013-3899