Combination of Metformin and Laser against Head and Neck Cancer Cells In Vitro

Metformin is a common drug for the treatment of diabetic patients. This drug has been shown to have anti-cancer effects. Metformin acts through the AMPK/mTOR pathway against cancer cells. We hypothesized that metformin, in combination with laser as photodynamic therapy (PDT), may increase cytotoxicity for cancer treatment. This study aimed to evaluate the anti-cancer effect and mechanism of metformin combined with laser irradiation on head and neck cancer cells.

The anti-cancer effect of metformin was evaluated using head and neck cancer cells (HN5 cells) and oral cavity normal cells (HUGU) cells in vitro. Cell viability and phototoxicity were assessed with the MTT assay. Evaluation of protein expression of p-mTOR and mTOR genes was evaluated with the western blot method.

The results showed that the toxic effect of metformin on HN5 cells was dose- and time-dependent. Metformin had significantly more cytotoxic effects on cancer cells than HUGU normal cells. The laser increased the cytotoxic effect of metformin in HUGU and HN5 cells significantly (p<0.05). Metformin down-regulated the level of p-mTOR/mTOR protein, and despite the decreased ratio of p-mTOR/mTOR, the laser has affected the performance of metformin on p-mTOR/mTOR.

In this study, we used the laser without using a photosensitizer, but the simultaneous use of laser light and metformin increased the lethality of metformin on cells, which requires further research to determine whether metformin itself is a functional photosensitizer.

: This study introduces the combination of metformin and laser as a new anti-tumor treatment that needs further studies.