Abstract: Objective To investigate the effects of CD151 down-regulation combined with bevacizumab on colorectal cancer growth and microvessel density. Methods Human colorectal cancer cell line HT-29 and CD151^--HT-29 cells strain(CD151 down-regulated HT-29 cells) were treated with bevacizumab. The cells were divided into four groups: control (HT-29) group, bevacizumab-treatment group, CD151^--HT-29 group, and CD151^--HT-29 + bevacizumab-treatment group. Cell proliferation was observed in each group using the MTS assay. A subcutaneous xenograft model in nude mice was established, and the HT-29 control group and CD151^--HT-29 group were treated with either 0.9% NaCl solution or bevacizumab. The growth of subcutaneous tumors in the four groups was observed, and the volume and weight of the tumors were recorded. Tumor tissues were collected for immunohistochemical staining of endothelial cells to assess microvessel density (MVD). Results Compared with the control group, cell proliferation was significantly reduced in the bevacizumab-treated group and CD151^--HT-29 group(P＜0.001). Cell proliferation in the CD151^--HT-29 + bevacizumab-treated group was slower than that in the single treatment groups (P＜0.001). In the subcutaneous tumor model, the volume, weight, and MVD of tumors in the bevacizumab-treated and CD151^--HT-29 groups were significantly reduced compared to the control group(P＜0.01). In the CD151^--HT-29 + bevacizumab group, the tumor volume, weight, and CD34 expression were significantly lower than in the single treatment groups (P＜0.01). Conclusions CD151 protein may play a role in the regulation of angiogenesis in colorectal cancer tissues and may have a synergistic effect with bevacizumab in inhibiting microvessel formation in tumor tissues.

Key words: colorectal cancer, CD151, bevacizumab, microvessel density