MTR and cancer: Taken together, our results detail the several beneficial effects of fascaplysin, which allow it to overcome drug resistance for cancer treatment: (1) fascaplysin sensitizes cells to the anti-cancer effect of AKT inhibition-based cancer treatment; (2) fascaplysin causes metabolic stress with decreased intracellular ATP levels and synergistically increases cancer cell apoptosis upon AMPK inhibitor treatment; and (3) fascaplysin suppresses the expression of several folate and purine metabolism-related genes, such as MTR and DHFR, and sensitizes cells to apoptosis caused by MTX.