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

초록

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 th