Sodium Butyrate Activity in Colorectal Cancer under Hypoxia: A Potential Role for Carbonic Anhydrase IX

Hypoxia poses a significant challenge to cancer therapy. The impact of hypoxia on butyrate, a gut metabolite that has anti-colorectal-cancer properties, is unclear. Thus, the aim of this study was to determine the activity of sodium butyrate (NaB) under hypoxic conditions. Furthermore, this study was the first to investigate the potential of carbonic anhydrase IX (CA IX), a hypoxia-regulated gene, as a target for NaB.

The Caco-2 and HT-29 colorectal cancer cell lines were exposed to 0, 5, 10, 15, and 20 mM NaB under hypoxic and normoxic conditions for 24 and 48 hours. We assessed cell viability and clonogenicity rates using an MTT assay and a colony-forming assay, respectively. RT-PCR was used to measure the effect of NaB on CA IX expression level.

After 24 hours of treatment with NaB, the percentage of viable HT-29 cells decreased under normoxic conditions, while it remained unchanged under hypoxic conditions. After 48 hours, the percentage of viable HT-29 cells decreased under both oxygen conditions. The viability of normoxic and hypoxic Caco-2 cells was only reduced after 48 hours of NaB application. Interestingly, NaB significantly reduced the number of HT-29 and Caco-2 colonies in normoxic and hypoxic conditions. NaB significantly decreased CA IX mRNA expression level in HT-29 hypoxic cells after 48 hours (p <0.0001), but not after 24 hours.

At the beginning, hypoxia caused an alteration in the anti-colorectal-cancer activity of NaB, which then returned to normal. Our data revealed the novel finding that NaB downregulates CA IX, suggesting a potential therapeutic strategy for colorectal cancer that targets tumor metabolism and pH regulation.