The Combination of Methionine Adenosyltransferase 2A (MAT2A) Inhibitor AG-270 and Recombinant Methioninase Is Not Cancer-selective in a Co-culture Model of Colon Cancer Cells and Normal Fibroblasts

Background/Aim: (rMETase) degrades extracellular methionine. rMETase, or other means of restricting methionine, in combination with numerous types of chemotherapy have shown synergistic cancer-selective efficacy. AG-270, a methionine adenosyltransferase 2A (MAT2A) inhibitor, blocks intracellular conversion of methionine to S-adenosylmethionine (SAM), the central reaction of the methionine cycle. The present study aimed to evaluate the synergistic and cancer-selective efficacy of the combination of AG-270 and rMETase in a co-culture model of cancer and normal cells. Materials and Methods: HCT116 human colon-cancer cells expressing green fluorescent protein (GFP) and human Hs-27 normal fibroblasts were co-cultured in Dulbecco's Modified Eagle's Medium (DMEM) with 10% fetal bovine serum in 12-well plates. Co-cultures were treated with AG-270 (6 μM and 10 µM) and rMETase (0.3 U/ml and 0.5 U/ml) alone or in combination. Cell growth and viability were assessed by phase-contrast microscopy and fluorescence imaging over 6 days. Results: Treatment with AG-270 or rMETase alone inhibited HCT116 colon-cancer cell viability in a dose-dependent manner, whereas Hs-27 normal fibroblasts remained viable on day 6 in co-culture. In contrast, the combination of AG-270 and rMETase produced a strong, synergistic reduction of the viability of both HCT116 and Hs-27 cells, accompanied by extensive morphological damage, in co-culture. GFP-expressing HCT116 colon-cancer cells were nearly eradicated by the combination treatment, as visualized by fluorescence imaging on day 6 in co-culture with Hs-27 fibroblasts. Conclusion: Dual inhibition of methionine metabolism by AG-270 and rMETase was toxic to both cancer cells and normal fibroblasts in a co-culture model which is internally controlled. In contrast, rMETase combined with numerous first-line chemotherapeutic drugs acted selectively and synergistically against cancer cells while sparing normal cells, including co-culture models. The present results suggest that AG-270 may have limited potential as an anticancer agent.