TYMS and colorectal carcinoma: Interestingly, in addition to miR-215-5p targeting TYMS expression, also miR-215-3p derived from the opposite arm of the same primary hairpin microRNA has gene silencing activity that influences 5FU cytotoxic activity since ectopic overexpression of miR-215-3p increased the sensitivity of CRC cells to 5FU, and although the exact mechanism has not been discovered, it has been shown to be at least in part related to targeting the CXCR1 chemokine receptor, which is an interleukin-8 receptor (Li et al. 2018a).