Metformin sensitises hepatocarcinoma cells to methotrexate by targeting dihydrofolate reductase

Metformin, the first-line drug for type II diabetes, has recently been considered an anticancer agent. However, the molecular target and underlying mechanism of metformin's anti-cancer effects remain largely unclear. Herein, we report that metformin treatment increases the sensitivity of hepatocarcinoma cells to methotrexate (MTX) by suppressing the expression of the one-carbon metabolism enzyme DHFR. We show that the combination of metformin and MTX blocks nucleotide metabolism and thus effectively inhibits cell cycle progression and tumorigenesis. Mechanistically, metformin not only transcriptionally represses DHFR via E2F4 but also promotes lysosomal degradation of the DHFR protein. Notably, metformin dramatically increases the response of patient-derived hepatocarcinoma organoids to MTX without obvious toxicity to organoids derived from normal liver tissue. Taken together, our findings identify an important role for DHFR in the suppressive effects of metformin on therapeutic resistance, thus revealing a therapeutically targetable potential vulnerability in hepatocarcinoma.

Automated summary

Metformin increases sensitivity of hepatocarcinoma cells to methotrexate by suppressing DHFR expression, blocking nucleotide metabolism, and inhibiting cell cycle progression and tumorigenesis. It represses DHFR transcriptionally via E2F4 and promotes lysosomal degradation of DHFR protein. Metformin enhances patient-derived hepatocarcinoma organoids response to MTX without toxicity to normal liver organoids, suggesting a potential therapeutically targetable vulnerability in hepatocarcinoma.