SLC19A1 and cancer: It has been reported that cancer cells preferentially use the mitochondrial FA pool to synthesize formate, which in turn is converted to 10-formyl-THF, to sustain nucleotide synthesis, but at physiological levels of FA, it seems that certain cell lines (expressing low levels of the folate transporter SLC19A1) also use the cytosolic pathway, thus bypassing the mitochondrial dependence for nucleotide biosynthesis.