6-Paradol enhances sorafenib's effects against colorectal cancer and promotes active metabolite formation

AIM: This research aimed to investigate the effect of 6-Paradol on sorafenib cytotoxicity in colorectal cancer (CRC) cell lines (HT-29, HCT-116, LS-174T, CaCo-2) through its effects on cellular processes. BACKGROUND: CRC, which ranks as the third most prevalent cancer, arises in the colon or rectum due to a multifaceted interplay of dietary, lifestyle, genetic, and age-related factors. Sorafenib (multikinase inhibitor), a drug targeting multiple cancer signals, shows promise against liver, thyroid, and kidney tumors but faces resistance in CRC. 6-Paradol (Zingiberaceae), a natural compound, offers the potential for overcoming this resistance. OBJECTIVE: The current study investigates whether 6-paradol potentiates sorafenib's anti-cancer activity in CRC cells by promoting increased drug entrapment, uptake, and metabolism. METHOD: Sulpharodamine B assay, caspase-3 activity, PARP cleavage, cell cycle distribution analysis, and P-gp efflux activity were assessed for Cytotoxicity using CRC cell lines (HT-29, HCT-116, LS-174T, CaCo-2). RESULT: Sorafenib showed potent cytotoxicity across CRC cell lines (IC50: 2.0-11.1 µM). Notably, 6-Paradol synergistically enhanced its effect in HT-29 and HCT-116 cells, reducing IC50 from 338 ± 55.7 to 107 ± 5.3 µM, respectively. 6-Paradol synergized with sorafenib, reducing HCT-116 cell proliferation from from 14.25 ± 0.62 to 20.7 ± 0 fg/cell and Paradol didn't show any significant change in c-PARP concentration which equaled 289.82 ± 27.32 pg/cell, suggesting enhanced cytotoxicity. 6-Paradol exposure resulted in a concentration-dependent (1-100 µM) increase in intracellular p-gp accumulation in CaCo-2, HCT-116, and HT-29. Co-incubation with 6-paradol significantly enhanced sorafenib cellular internalization within CaCo-2 cells, resulting in a concomitant decrease in its extracellular concentration from 1491 ± 132 ng/ml to 216 ± 39 ng/ml. 6-Paradol increased sorafenib intracellular accumulation ranges from 239 ± 16 to 327 ± 34 pg/cell, respectively in HCT-116 cells. 6-Paradol significantly increased the intracellular conversion of sorafenib to its active N-oxide metabolite and facilitated its retention within the CaCo-2 cell compartment. CONCLUSION: In conclusion, 6-Paradol marked elevation in sorafenib's cytotoxic profile by influencing its cellular uptake and metabolism. Future research should expand in vitro studies to diverse cell lines, conducting in vivo elucidating underlying mechanisms and rigorously evaluating safety and toxicity.