Abstract A11: Radio-sensitivities and angiogenic signaling pathway of irradiated endothelial cells isolated from cancer and normal tissue of human breasts in vitro

Abstract

Abstract Despite the strong possibility that endothelial cells of tumors and normal tissues may be different in various aspects, most of the previous studies on endothelial cells have been conducted using normal endothelial cells. Therefore, we have developed a novel method for harvesting endothelial cells from blood vessels of freshly obtained cancer and adjacent normal tissue of human breast, and further investigated radio-sensitivities and angiogenic signaling pathway in the alternation of angiogenic process observed after the purified cancer-derived endothelial cells (CECs) and normal tissue-derived endothelial cells (NECs) were irradiated in vitro. When human breast tissues including cancer were embedded in Matrigel and cultured in endothelial cell culture medium (ECM) containing growth factors, endothelial cells grew out of the tissues. The endothelial cells were harvested, cultured as monolayer cells in plates coated with gelatin, and exposed to radiation, and then the changes in clonogenic cell survival, tube formation capacity, γH2AX foci, gene expression, and cellular signaling pathways were determined. Both CECs and NECs expressed almost the same levels of surface markers CD31, CD105 and TEM-8 (tumor endothelial marker-8), which are known to be expressed in angiogenic endothelial cells, i.e., mitotically active endothelial cells. CECs were significantly more radiosensitive in treatment of single dose (4 Gy) and hyperfractionation (4 Gy in 2 or 4 equal fractions) of ionizing radiation (IR) than their normal counterparts although hyperfractionated IR reduced clonogenic cell death in both NECs and CECs than single dose of IR. In addition, we found that IR-induced foci formation of γH2AX in NECs increased 1 hr and declined afterwards when the cells were treated with 4 Gy of IR. On the contrary, it was remained up to 4 hr in CECs. In NECs, 4 Gy of IR induced an increase in the capillary-like tube formation, the expression of matrix metalloproteinase-2 (MMP-2), and the activation of ERK pathway. However, in CECs, 4 Gy of IR significantly reduced the capillary-like tube formation, and induced the expression of angiostatin and the activation of both AKT and JNK pathways. Additionally, inhibition of ERK with a pharmacological inhibitor or a small interfering RNA markedly suppressed the capillary-like tube formation and the expression of MMP-2 caused by IR in NECs. In CECs, inhibition of either AKT or JNK with a pharmacological inhibitor or a small interfering RNA clearly attenuated inhibition of the capillary-like tube formation, and the expression of angiostatin caused by IR. Furthermore, hypoxia increased the capillary-like tube formation and radioresistance in both NECs and CECs, but the delineation of the mechanisms remains to be studied. We have developed a simple and efficient new method for isolating endothelial cells from cancer and normal tissue. Moreover, our results collectively demonstrate that there are distinct differences in the radiation responses of NECs and CECs, and might provide important clues for improving the efficacy of radiation therapy. [This research was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (MRC: NRF-2014R1A5A2009392 and NRF-2013M2A2A7043703] Citation Format: Eun-Taex Oh, Min-Jeong Song, Hyemi Lee, Yun-Jeong Choi, Heon Joo Park. Radio-sensitivities and angiogenic signaling pathway of irradiated endothelial cells isolated from cancer and normal tissue of human breasts in vitro. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Angiogenesis and Vascular Normalization: Bench to Bedside to Biomarkers; Mar 5-8, 2015; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl):Abstract nr A11.