Pyrimethamine Inhibits Human Ovarian Cancer by Triggering Lethal Mitophagy via Activating the p38/JNK/ERK Pathway.

Objectives: Ovarian cancer, a leading cause of gynecological malignancy-related mortality, is characterized by limited therapeutic options and a poor prognosis. Although pyrimethamine has emerged as a promising candidate demonstrating efficacy in treating various tumors, the precise mechanisms of its antitumor effects remain obscure. This study was specifically designed to investigate the mode of action underlying the antitumor effects of pyrimethamine in preclinical settings.

Methods: The effects of pyrimethamine on cellular proliferation were meticulously assessed using both the cell counting kit 8 (CCK-8) assay and the colony formation assay, with the effects further confirmed in a murine model. A confocal microscope was utilized to monitor the dynamic alterations in mitochondria within ovarian cancer cells. Additionally, adenosine triphosphate (ATP) and reactive oxygen species (ROS) assays were conducted to measure mitochondrial damage induced by pyrimethamine in ovarian cancer cell lines. The mitochondrial membrane potential was assessed using fluorescent dyes as an indicator of mitochondrial functional status. Furthermore, transcriptome analysis and immunohistochemical techniques were employed to detect the impact of pyrimethamine on ovarian cancer cells.

Results: Our results demonstrated that pyrimethamine induced ovarian cancer cell death through mitochondrial dysfunction and lethal mitophagy. Transcriptome profiling analysis and Western blot demonstrated that activation of the p38/JNK/ERK signaling pathway was implicated in the process of pyrimethamine-induced mitophagy in ovarian cancer cells. Importantly, combination treatment with pyrimethamine and paclitaxel in vitro and in vivo showed a synergistic antitumor effect.

Conclusions: Altogether, these findings indicate that the antitumor effects of pyrimethamine result from the induction of lethal mitophagy via regulation of the p38/JNK/ERK pathway in ovarian cancer. Considering the low toxicity and high tolerance associated with pyrimethamine, it is suggested that pyrimethamine be evaluated in the treatment of ovarian cancer, either as a monotherapy or in combination with paclitaxel.