Microbial experience influences B16 melanoma tumor growth

Abstract

Cancer immunity research is traditionally conducted with specific pathogen-free (SPF) mice, which mimic the immune system of a human newborn. This poses a challenge for research aimed at understanding immune responses relevant to humans. We utilized a mouse model to investigate microbial experience impacts on immune population dynamics and responses. By cohousing SPF C57Bl/6 mice with pet store mice, we generated a cohoused (CoH) mouse that more accurately reflects the impact of microbial experience on the human immune system. We hypothesized that CoH mice would mount a more effective anti-tumor response when compared to SPF mice. We challenged the mice with sub-cutaneous B16 melanoma to measure both tumor growth and immune responses. Interestingly, CoH tumor grew more slowly, and tumor weights were significantly reduced when compared to SPF mice on days 7 and 10 post-injection. We investigated CD8+ T cell and monocyte/macrophage phenotypes in various tissues, including the tumors. Control of tumor growth may be related to the observed differences in CD8+ T cell activation profiles and monocyte/macrophage differentiation found in CoH mice. Collectively, our results indicate that microbial experience influences anti-tumor immunity and that cohoused mouse models may prove to have valuable translational applications for future cancer immunity research.