SLC19A1’s genetic variants affect antifolate response, showing a crucial role in the treatment of cancers and inflammatory diseases such as rheumatoid arthritis, psoriasis, and inflammatory bowel disease (Zhao and Goldman, 2003; Jansen et al., 2004; Matherly et al., 2007; Yee et al., 2010; Kanarek et al., 2018; O’Connor et al., 2021). This evidence concerns the gene SLC19A1 and cancer.