CCR9 and renal cell carcinoma: A metagenomic analysis of fecal samples from patients receiving PD-1 blockade treatment for non-small-cell lung cancer (NSCLC) and renal cell carcinoma (RCC) showed that those patients who failed to respond to PD-1 blockade had lower levels of Akkermansia muciniphila, which had been confirmed to facilitate the recruitment of CCR9+, CXCR3+, and CD4+ T lymphocytes via the IL-12 pathway [207].