Sanguinarine triggers apoptosis in cutaneous squamous cell carcinoma cells through ROS-dependent JNK-kinase signaling

Abstract Cutaneous Squamous Cell Carcinoma (cSCC), the second most common non-melanoma skin cancer, originates from the malignant transformation of atypical epidermal keratinocytes. In recent decades, contemporary research has widened our comprehension of the molecular pathogenesis of cSCC, propelling the evolution of effective therapies in the management of cSCC. Sanguinarine (Sng), a quaternary benzophenanthridine alkaloid, is a multifaceted natural agent. In consideration of its potent anti-neoplastic activity, the present study evaluated the in vitro cytotoxicity of Sng against primary (A431) and metastatic (A388) cSCC cells and delineated its underlying molecular mechanisms. Treatment with Sng significantly inhibited cell proliferation by inducing sub-G0/G1 cell-cycle arrest and apoptosis in cSCC cells. Sng evoked reactive oxygen species (ROS) generation, intracellular glutathione (GSH) depletion, mitochondrial transmembrane potential (ΔΨ m ) depolarization, and the activation of the JNK pathway as well as that of caspase-3, -8, -9, and PARP. Application of the antioxidant N-acetyl cysteine (NAC) inhibited ROS production, replenished GSH levels, and abolished the apoptosis induced by Sng via downregulating JNK. Our results also showed that z-VAD-FMK, a pan-caspase inhibitor, efficiently blocked cell death induced by Sng. Moreover, pharmacological inhibition of JNK by SP600125 mitigated Sng-induced apoptosis. Finally, Sng ablated the stemness potential in metastatic cSCC cell-derived spheroids. Cumulatively, this investigation revealed that Sng triggers apoptosis in cSCC cells through ROS- dependent activation of the MAPK signaling pathway, thus suggesting its therapeutic potential.