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: Methionine addiction is a fundamental and general hallmark of cancer cells. Recombinant methioninase (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.