It has been found that multiple circRNAs can regulate SLC1A5 through their miRNA sponge role; therefore, the amino acid metabolism could be affected in non-small cell lung cancer [63,67,68], ovarian cancer [69], oesophageal cancer [62] and other cancer cells [70–72] (Figure 4); and as the results, the development of malignant tumours would be promoted or inhibited. This evidence concerns the gene SLC1A5 and cancer.