In CRC, it has been shown that, as a secondary effect, 5-FU treatment positively regulates the expression of ABCB1, ABCC1, and ABCG2a through the activation of the IRE1α-XBP1 pathway; thus, favoring the chemoresistance and inhibition of this protein decreased the ABC transporter expression and in turn restored the efficacy of 5-FU treatment in colon cancer cells [38,40]. The gene discussed is ABCG2; the disease is colorectal carcinoma.