Pyrimethamine Triggers the Apoptotic Pathway in Mucoepidermoid Carcinoma in Cell-Based Models

Mucoepidermoid carcinoma (MEC) is the most prevalent salivary gland malignancy, with a poor prognosis in high-grade tumors at diagnosis. This highlights the need for effective antitumor agents for treating MEC. Therefore, we aimed to investigate the antineoplastic efficacy of pyrimethamine (PYR), a Food and Drug Administration-approved antiparasitic medicine, to repurpose it as an alternative therapeutic option for treating human MEC.

The trypan blue exclusion assay, cell counting kit-8 assay, and live/dead assay were performed to assess the antiproliferative efficacy of PYR. PYR-induced apoptosis was confirmed with 4',6-diamidino-2-phenylindole staining, cell cycle analysis, and annexin V/propidium iodide staining. A western blot assay was conducted to measure changes in cleaved caspase 8 and myeloid cell leukemia-1 (Mcl-1) expression after PYR treatment. Mcl-1 overexpression was used to further confirm the apoptosis-inducing activity of PYR. The hanging drop method was employed to assess the efficacy of PYR in a three-dimensional culture system.

PYR-induced apoptotic cell death in the YD-15 high-grade MEC cell line by promoting apoptosis, as evidenced by MCl-1 proteasomal degradation and increased cleaved caspase 8 expression.

Our results indicate that PYR can effectively target human MEC by inducing both intrinsic and extrinsic apoptotic pathways.