While studying the response of sarcoma tumors to cyclophosphamide, Daillère et al. found that E. hirae translocated from the small intestine to secondary lymphoid organs and increased the intra-tumoral CD8/Treg ratio; while B. intestinihominis accumulated in the colon and promoted the infiltration of IFN-γ-producing γδT cells in cancer lesions (124). The gene discussed is IFNG; the disease is cancer.