Cannabidiol impairs tumor-associated behaviors and modulates apoptosis- and autophagy-related pathways in cisplatin-resistant head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) remains a challenge due to recurrence, metastasis, and resistance to conventional therapies, particularly in human papillomavirus (HPV)-negative tumors. Cannabidiol (CBD), a non-psychoactive phytocannabinoid, has demonstrated antitumor activity in several cancer models; however, its effects in chemoresistant HNSCC are not well established. This study evaluates the antitumor effects of CBD and cellular mechanisms in a cisplatin -resistant, HPV-negative HNSCC model. Cytotoxic effects of CBD were assessed in HN13 cells and compared with fibroblasts and keratinocytes using MTT and selectivity index analysis. Migration, invasion, metalloproteinase activity, clonogenic survival, and cytotoxicity on 3D spheroids were evaluated. Cell death-related mechanisms were investigated using acridine orange/propidium iodide staining and Western blot analysis of apoptosis, autophagy, and cell-cycle regulation. Antitumor activity and vascular safety were further assessed using the chorioallantoic membrane model and HET-CAM assay. The combined effect of CBD and CIS was evaluated using the combination index analysis. CBD exhibited selective cytotoxicity toward HN13 cells and reduced migration, invasion, matrix metalloproteinase-2/9 activity, clonogenic survival, and 3D spheroid growth. CBD altered proteins associated with apoptosis, autophagy, and cell-cycle regulation. Pharmacological inhibition with 3-MA enhanced CBD-associated apoptotic signaling, increasing PARP and caspase-3 cleavage. In the CAM, CBD reduced tumor growth and vascular area without inducing vascular irritation. Furthermore, CBD and CIS demonstrated synergistic cytotoxic effects in HN13 cells. CBD exerted selective antitumor effects on CIS-resistant HN13 HNSCC cells, affecting tumor-associated behaviors and modulating apoptosis and autophagy-related signaling, while acting synergistically with cisplatin. These findings support further preclinical investigation of CBD as a potential adjunct approach in HNSCC, particularly in chemoresistant settings.