Attesting to the relevance of intestinal NK cells and Th1 cells, the S1P-S1PR1/5 axes, and the CXCR3-CXCL9 chemokine gradient in restraining bone tumor growth, blockade of NK and Th1 cell egress from the intestine or blockade of their influx into the BM resulted in accelerated cancer growth in bone, an effect mirroring the consequences of microbiome ablation by antibiotics. Here, S1PR1 is linked to cancer.