Enhancing Anti-Cancer Efficacy in Colorectal Cancer Through Cannabinoid and Sodium Pentaborate Co-Therapy

Background: Colorectal cancer (CRC) is characterized by pronounced genetic and phenotypic heterogeneity, which substantially influences therapeutic response and limits the efficacy of uniform treatment strategies. Cannabinoid-derived phytochemicals and boron-based compounds have independently been reported to modulate cancer cell proliferation, survival, and redox balance. However, the extent to which these agents interact at the cellular level and whether such interactions are dependent on tumor-specific molecular contexts remains poorly defined. Methods: Sodium pentaborate (NaB) was combined with non-cytotoxic concentrations of cannabidiol (CBD) or cannabigerol (CBG) and evaluated in HCT-116 and HT-29 colorectal cancer cell lines. Cell viability and drug interactions were assessed by MTS and combination index analyses. Apoptotic responses were examined by Annexin V/PI staining, caspase-3/7 activity assays, and transcriptional profiling of apoptosis-related genes. Cell cycle dynamics and proliferation-associated markers were analyzed by flow cytometry and quantitative PCR. In parallel, ferroptosis-associated gene expression patterns were investigated to evaluate alterations in redox and iron metabolism pathways. Results: NaB–cannabinoid combinations produced divergent biological outcomes depending on cellular background. HT-29 cells exhibited dose-dependent antiproliferative responses to NaB + CBD and NaB + CBG, with synergistic interactions observed only at selected dose combinations accompanied by increased early apoptosis. In contrast, HCT-116 cells primarily responded with cell cycle arrest and transcriptional stress signaling rather than enhanced cytotoxicity. Modulation of ferroptosis-related gene expression further indicated differential redox adaptation between the two cell models. Conclusions: NaB–cannabinoid combinations elicit distinct biological outcomes in colorectal cancer cells that are strongly determined by cellular context. While HT-29 cells are selectively sensitized to combination dose level, HCT-116 cells predominantly respond through cell cycle arrest and adaptive stress-response pathway activation. These findings emphasize the necessity of context-aware combination strategies and provide a mechanistic framework for the further development of boron–cannabinoid-based therapeutic approaches in colorectal cancer.