Planktonic and Biofilm Bifidobacterium infantis : Differential Effects of Cells and Supernatants on Colorectal Cancer Cell Viability and Apoptosis

Colorectal cancer (CRC) is a leading cause of cancer-related mortality worldwide, and dietary factors play a significant role in its pathogenesis. Probiotics and their metabolites have attracted interest as potential functional food ingredients, but the anticancer potential of probiotic bacteria, particularly in biofilm phenotypes, remains underexplored. This study compared the effects of planktonic and biofilm phenotypes of Bifidobacterium infantis, as well as their culture supernatants, on Caco-2 cells. The results showed that B. infantis bacterial cells more strongly reduced Caco-2 cell viability than supernatants and were accompanied by disruption of barrier integrity, increased monolayer permeability, and induction of apoptosis. Under Escherichia coli-induced inflammatory conditions, B. infantis biofilms displayed higher proapoptotic activity than planktonic bacteria. The mechanisms underlying these effects may involve bacterial adhesion, metabolite production, or short-chain fatty acid-mediated actions, but these parameters were not directly measured, and the proposed mechanisms remain speculative. TNF-α levels did not change significantly under these conditions. Collectively, these in vitro findings provide a foundation for further investigation of probiotic biofilms in CRC research and warrant future studies to evaluate their potential as dietary supplements for CRC prevention and management.