Effects of Short Chain Fatty Acids Butyrate and Propionate on Colorectal Cancer Cell Lines in Combination with 5-FU Treatment and Glucose Starvation

Abstract

Colorectal cancer (CRC) is an increasing global health concern, ranking as the third most common cancer worldwide and the second leading cause of cancer related mortality. One of the main risk factors for the development of this disease is gut microbiome dysbiosis. Butyrate (BA) and propionate (PA) are two short chain fatty acids (SCFAs) produced by gut microbiota as a product of bacterial fermentation of dietary fibers. BA and PA have demonstrated promising anti-carcinogenic effects, including inhibition of cell proliferation, induction of apoptosis, and modulation of gene expression in CRC cells. Glucose, a primary energy source for cells, plays an important role in cancer cell metabolism and survival, and altered glucose metabolism is considered as being one of the many hallmarks of cancer. This study aimed to explore the effects of BA and PA, both singularly and combinatorically, as well as a pretreatment to the common chemotherapeutic agent 5-fluorouracil (5-FU), on the three CRC cell lines HCT116, SW948, and Caco-2, under different glucose conditions to stimulate metabolic stress.

Singular treatments decreased cell viability in a dose dependent manner across all cell lines, consistent with their known mechanisms. Under glucose starvation, however, the CRC cells showed increased viability, suggesting utilization of BA and PA as alternative energy sources. The metabolic profiling revealed a biphasic response, where lower BA and PA concentrations enhanced mitochondrial function, while higher concentrations induced mitochondrial stress. Combinatorial treatments of BA and PA showed synergistic effects in cell growth inhibition, especially at lower PA concentrations. Higher PA concentrations reduced the sensitivity to BA. Under glucose starved conditions, the combination treatments increased cytotoxicity compared to the standard physiological concentration of glucose. Pretreatment of BA and PA to 5-FU gave variable results across different concentrations and cell lines, indicating the need for further investigation.

Overall, BA and PA demonstrated interesting potential as therapeutic agents in CRC treatment, warranting further research to optimize protocols and using 3D culture models to more accurately simulate the tumor microenvironment. Exploring the regulation of BA and PA as supplements and/or pre/probiotics could provide insights into implementing their use in clinical settings to improve therapeutic outcomes.