PDCD1 and cancer: In vitro: Reduces proliferation of cancer cells, induces apoptosis, and decreases both the rate of extracellular acidification and oxygen utilization in CRC cells. In vivo: Inhibits the growth of CRC xenograft tumors, increases tumor cell apoptosis, enhances lymphocyte infiltration, and potentiates the antitumor efficacy of PD-1 inhibitors