Comparison of angiogenetic effects of different dose fractionated radiotherapy on rectal cancer cells

Abstract

Objective To explore the effects of different dose fractionated radiotherapy on angiogenesis in rectal cancer and its potential mechanism. Methods The pathological data of 56 rectal cancer patients admitted to our hospital from 2017 to 2020 were collected for statistical analysis. The microvessel density (MVD) in the rectal cancer tissues under hypofractionated radiotherapy (HFR) and conventional fractionated radiotherapy (CFR) were respectively detected by immunohistochemistry. The expression levels of hypoxia inducible factor 1-alpha (HIF-1α) and vascular endothelial growth factor (VEGF) in the rectal cancer tissues were determined by Western blotting. Then the cultured rectal cancer SW1463 cells and human umbilical vein endothelial cells (HUVECs) were irradiated at doses of 0, 4, 12 and 24 Gy, respectively. CCK-8 assay was subsequently used to test the proliferation of both cells in each group, Western blotting was performed to measure the levels of VEGF and HIF-1α in SW1463 cells, and ELISA assay was adopted to detect the concentration of VEGF in the supernatant of rectal cancer cells. In addition, CCK-8 assay and colony formation assay were carried out to observe the proliferation of HUVECs after intervened with different doses of irradiated cultured medium. Results Chi-square test showed no significant difference in pathological tumor regression grade (TRG) between the HFR and CFR groups. The results of immunohistochemistry indicated that the MVD in the HFR group (32.00±3.61) was significantly higher than that in the CFR group (22.33±3.06, P < 0.05). Western blotting also revealed the protein levels of HIF-1α and VEGF were remarkably up-regulated in the HFR group (P < 0.01). In in vitro study, high-dose radiation dose-dependently reduced the proliferation of SW1463 cells and HUVECs (P < 0.05). However, the expression levels of VEGF and HIF-1α in rectal cancer cells and the content of VEGF in the supernatant were increased gradually with the rise of irradiation dose (P < 0.01). Correspondingly, the proliferation of HUVEC cells was prominently enhanced by the cultured medium of rectal cancer cells after high-dose radiation (P < 0.01). Conclusion High-dose radiotherapy inhibits the proliferation of vascular endothelial cells, while may simultaneously increase the compensatory angiogenesis of tumor vessels by promoting the expression of HIF-1α and VEGF in rectal cancer cells.

Keywords

• rectal cancer
• vascular endothelial cells
• radiotherapy
• hif-1α
• vegf