# Modulation of the Antitumor Response to Metformin, Caffeine, and Sodium Dichloroacetate by the Hypoxic Microenvironment in Lung Cancer Cells

## TL;DR

This study shows that the effectiveness of combining metformin with caffeine or DCA in lung cancer cells is reduced under low oxygen conditions, which are common in tumors.

## Contribution

The study reveals that hypoxia in tumors causes antagonism in drug combinations of metformin with caffeine or DCA, despite additive effects under normal oxygen conditions.

## Key findings

- Under normoxia, metformin combined with DCA or caffeine showed additive effects on lung cancer cell viability.
- In hypoxia, the same drug combinations exhibited significant antagonism, reducing their therapeutic potential.
- Hypoxia alters the pharmacological interaction of metformin with caffeine or DCA, highlighting the need to consider tumor oxygenation in treatment design.

## Abstract

Metformin, caffeine, and dichloroacetate (DCA) have shown antitumor effects. The hypoxic tumor microenvironment can modulate drug response. We aimed to analyze the interaction of metformin with caffeine or DCA in lung cancer cells (HCC827) under normoxia and hypoxia conditions. Cell viability was evaluated using the crystal violet assay after individual and combined drug treatment under normoxia (21% O2) and hypoxia (1% O2) conditions. Combination effects were analyzed using isobolographic analysis. The results show that under normoxia conditions, the combination of metformin with DCA (γ = 0.98 ± 0.35, p > 0.05) or caffeine (γ = 0.90 ± 0.34, p > 0.05) revealed additivity. However, in hypoxia, both combinations exhibited significant antagonism, with γ values appearing greater than one for metformin + DCA (γ = 4.20 ± 1.44, p < 0.05) and metformin + caffeine (γ = 2.88 ± 0.90, p < 0.05). Hypoxia significantly alters the pharmacological interaction of metformin with caffeine or DCA, which could limit their combined therapeutic potential in hypoxic tumors despite metformin’s activity in this environment. The importance of considering tumor oxygenation status in the design of combined therapies for lung cancer is emphasized.