A Novel Pyrazole Pyrimidine Derivative MBP346 Induces Cell Death via ROS-Mediated Mitochondrial Damage in Human Head and Neck Squamous Cell Carcinoma

<b>Background</b>: Head and neck squamous cell carcinoma (HNSCC) represents almost 95% of head and neck cancer cases and ranks as the sixth most prevalent malignant tumor globally. Several treatment strategies, such as surgery, radiation, and chemotherapy, are implemented to boost the outcomes for patients with HNSCC. However, the overall survival rate for patients with HNSCC has remained poor. MBP346 is a novel pyrazole pyrimidine compound that is cytotoxic to HNSCC cells. Therefore, this study aims to investigate its effect on HNSCC and to explore its possible molecular mechanism. <b>Methods</b>: Cell viability of HNSCC (Cal33 and Scc15) cells and normal NOK cells treated with MBP346 was determined by Methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay. Colony formation assay and Edu assay were used to detect cell proliferation. Cell cycle and apoptosis were analyzed by flow cytometry. Western blot was used for detecting cell cycle-related and cell apoptotic-related proteins. Immunofluorescence assay was performed to analyze the effect of MBP346 on reactive oxygen species (ROS) and mitochondrial membrane potential (MMP). <b>Results</b>: MBP346 significantly inhibited the proliferation of Cal33 and Scc15 cells, with half inhibitory concentrations of 1.56 ± 0.13 μmol·L^-1 and 4.41 ± 0.28 μmol·L^-1, respectively. The cell cycle-related proteins CyclinD1, CyclinA2, and CDK2 were downregulated, and P21 was upregulated in Cal33 and Scc15 cells treated with MBP346, which blocked the cell cycle in the S phase. MBP346 induced cell apoptosis in Cal33 and Scc15 cells by inducing ROS production. In addition, the elevated ROS decreased MMP to accelerate apoptosis. N-acetylcysteine (NAC), an ROS inhibitor, suppressed MBP346-induced cell apoptosis. <b>Conclusions</b>: MBP346 may serve as a therapeutic agent in HNSCC by inducing cell death. It achieves this by halting cell proliferation through cell cycle arrest and enhancing apoptosis due to increased ROS, which results in mitochondrial dysfunction.