Anticancer effects of a Captopril Montmorillonite formulation in oral cancer cells through apoptosis and redox modulation

Abstract Background Oral squamous cell carcinoma (OSCC) remains challenging due to the limited efficacy and toxicity of current therapies. This study investigates the anticancer potential of Captopril–Montmorillonite (CP–MMT) (nanoclay-based delivery system), a drug-repurposing approach in which Captopril is incorporated within MMT nanoclay layered silicate carrier. To our knowledge, this formulation has not been previously investigated in OSCC cell lines, demonstrating enhanced anticancer efficacy. The aim of the work was to compare the anticancer effects of CP–MMT formulation with free Captopril in OSCC cell lines, focusing on cytotoxicity, apoptosis, cell-cycle arrest, oxidative stress, and key molecular markers. Methods CP–MMT nanoclay-based formulation was synthesised via solution-intercalation, characterised (particle size, polydispersity, and zeta potential), and biologically evaluated in laryngeal (HEP-2) and tongue cancer (HN-9) cells using cytotoxicity (MTT), apoptosis (Annexin V/PI), cell-cycle profiling, oxidative stress assays, including Total Antioxidant Capacity (TAC), Glutathione (GSH), and gene expression analysis for molecular markers (BAX, BCL-2, P53, CASPASE-3, Ki-67, and IL-6). Results CP–MMT formulation significantly increased apoptosis, induced robust G2 and S-phase arrest, increased pro-apoptotic gene expression (BAX: 3.8-fold, P53: 2.9-fold, CASPASE-3: 2.7-fold), and downregulated anti-apoptotic and proliferative markers (BCL-2: 0.6-fold, Ki-67: 0.3-fold, and IL-6: 0.3-fold ; p < 0.05). CP–MMT formulation reduced cell viability, with IC₅₀ values of 30 µM in HN-9, ~ 40 µM in HEP-2, ~ 115 µM in OEC, compared to the minimal effects of free Captopril. Oxidative stress was increased, as shown by reduced TAC (0.2 mM) and GSH (0.2 mg/dL) levels in CP–MMT-treated HN-9 cells. Conclusions The CP–MMT formulation showed enhanced anticancer activity compared to free Captopril in vitro, with effects on apoptosis, cell proliferation, and cellular redox balance. These findings are limited to in vitro conditions and should be interpreted cautiously. Further validation in in vivo and advanced 3D tumour models is required.