IL21 and colorectal carcinoma: The decrease in pSTAT3 and increase in pSTAT5 suggest that the cytokines that target the pSTAT5 signalling pathway, such as IL-2 and IL-15, might play a more vital role in the activation and function of NK cells in this cohort of advanced CRC patients over cytokines that primarily signal through the STAT3 pathway, such as IL-12 and IL-21.