HAVCR2 and cancer: Exosomal circ_UHRF1 was revealed to impair the function of natural killer (NK) cells by sequestering miR-449c-5p that directly targets hepatitis A virus cellular receptor 2 (HAVCR2, also named TIM3), ultimately diminishing the anti-cancer effects of nivolumab, anti-programmed cell death 1 (PD1) antibodies [52] (Figure 2 and Table 1).