Abstract: Objective To investigate the effects of diabetes on tumor progression, and the effects of diabetes combined with colorectal or breast cancer on the intestinal flora by constructing a diabetes-tumor mouse model, and the differences in body mass, tumor volume, survival rate, and initial flora of the mice in different treatment groups were statistically analyzed. Methods Sixty mice were divided into control, diabetes, colorectal cancer, diabetes + colorectal cancer, breast cancer, and diabetes + breast cancer groups. The diabetic mouse model was established by streptozotocin injection, and solid tumor models of colorectal and breast cancer were further established on this basis. Changes in the body mass, tumor volume, and survival rate of the mice in each group were observed and analyzed. The mouse feces were collected, and then the microbial community sequencing data were analyzed using the QIIME2 platform based on the DATA2 and Vesearch methods. Results The body mass (P < 0.05) and survival rate (P < 0.01) of mice with diabetes combined with colorectal or breast cancer were significantly reduced, but there was no significant difference in tumor volume in mice. Compared with the control group or the colorectal cancer group, the species richness of the intestinal flora in mice in the diabetes + colorectal cancer group was significantly altered (P < 0.05); while the diabetes + breast cancer group did not significantly change (P > 0.05). The beta diversity and bacterial species composition of the intestinal flora in mice with diabetes combined with colorectal or breast cancer were also affected. Conclusion Diabetes promotes the progression of colorectal or breast cancer. Diabetes combined with colorectal or breast cancer has a greater impact on the intestinal flora of mice than colorectal or breast cancer alone.

Key words: Type 2 diabetes, Colorectal cancer, Breast cancer, Intestinal flora, Mice