Aronia Berry Extract Inhibits Cancer Stemness and Overcomes 5-Fluorouracil Resistance by Targeting TLR3/NF-κB Signaling in Colorectal Cancer

Background: Colorectal cancer (CRC) remains a major clinical challenge, in part due to the limited efficacy of 5-fluorouracil (5-FU)-based chemotherapy, which is often compromised by the emergence of acquired resistance. Aronia berry extract (ABE), a phenolic-rich natural compound, has gained increasing attention for its anticancer and chemosensitizing properties. This study aimed to investigate whether ABE can overcome 5-FU resistance (5-FU-R) in CRC and to elucidate the molecular mechanisms underlying its therapeutic effects. Methods: We conducted a series of in vitro experiments using 5-FU-R CRC cell lines to evaluate the synergistic effects of combined ABE and 5-FU treatment. Genome-wide transcriptomic profiling was performed to identify key regulatory pathways associated with chemoresistance and to determine potential ABE-responsive targets. Findings were further validated using patient-derived 3D organoids (PDOs). Results: Co-treatment with ABE and 5-FU significantly reduced the effective concentration of 5-FU required to inhibit 5-FU-R CRC cells, yielding a Bliss synergy score greater than 10. The combination markedly suppressed cell viability, clonogenic potential, migration, and invasion. ABE also reduced cancer stemness, as evidenced by reduced CD44, Nanog, and Oct4 expression. Functional inhibition of Toll-like receptor 3 (TLR3) impaired spheroid growth, and PDO experiments corroborated these findings, demonstrating reduced organoid growth, diminished survival, and decreased NF-κB expression following ABE treatment. Conclusions: Our findings reveal that ABE effectively overcomes 5-FU resistance in CRC by targeting the TLR3/NF-κB signaling axis. This study highlights ABE as a safe, accessible, and promising adjunctive strategy to enhance therapeutic responses in 5-FU-resistant CRC.