One bout of endurance exercise does not change gene expression or proliferation in a C26 colon carcinoma in immunocompetent mice
Purpose. Exercise typically reduces tumour growth, proliferation, and improves outcomes. Many of these effects require exercise to change gene expression within a tumour, but whether exercise affects gene expression within a tumour has not been investigated yet. The aim of this study was therefore to find out whether one bout of endurance exercise alters gene expression and proliferation in a C26 carcinoma in immunocompetent mice. Methods. BALB/c were injected with C26 colon carcinoma cells. Once the tumours had formed, the mice either ran for 65 min with increasing intensity or rested before the tumour was dissected. The tumours were then analysed by RNA-Seq and stained for the proliferation marker KI67.  Results. One bout of running for 65 minutes did not systematically change gene expression in C26 carcinomas of BALB/c mice that ran for 65 minutes when compared to BALB/c mice that were rested. However, when analysed for sex, the RNA expression of 17, mostly skeletal muscle-related genes was higher in the samples of the female mice taken post exercise. Further histological analysis showed that this signal likely comes from the presence of muscle fibres from the panniculus carnosus muscle inside the tumours. Also, we found no differences in the positivity for the proliferation marker KI67 in the control and exercise C26 carcinomas. Conclusion. A bout of exercise did not systematically affect gene expression or proliferation in C26 carcinomas in immunocompetent BALB/c mice. Overall design: BALB/c were injected with C26 colon carcinoma cells. Once the tumours had formed, the mice either ran for 65 min with increasing intensity or rested before the tumour was dissected. The tumours were then analysed by RNA-Seq and stained for the proliferation marker KI67.