title: Pyrimethamine induces apoptosis of melanoma cells via a caspase and cathepsin double-edged mechanism.
abstract: The unresponsiveness of metastatic melanoma to conventional chemotherapeutic and biological agents is largely due to the development of resistance to apoptosis. Pyrimethamine belongs to the group of antifolate drugs, and in addition to antiprotozoan effects, it exerts a strong proapoptotic activity, which we recently characterized in human T lymphocytes. However, no data regarding pyrimethamine anticancer activity are available thus far. To this end, we examined the in vitro effects of pyrimethamine on apoptosis, cell cycle distribution, and cell proliferation of human metastatic melanoma cell lines. The in vivo antitumor potential of pyrimethamine was evaluated in a severe combined immunodeficiency (SCID) mouse xenotransplantation model. Our data indicate that pyrimethamine, when used at a clinically relevant concentration, induced apoptosis in metastatic melanoma cells via the activation of the cathepsin B and the caspase cascade (i.e., caspase-8 and caspase-9) and subsequent mitochondrial depolarization. This occurred independently from CD95/Fas engagement. Moreover, pyrimethamine induced a marked inhibition of cell growth and an S-phase cell cycle arrest. Results obtained in SCID mice, injected s.c. with metastatic melanoma cells and treated with pyrimethamine, indicated a significant inhibitory effect on tumor growth. In conclusion, our results suggest that pyrimethamine-induced apoptosis may be considered as a multifaceted process, in which different inducers or regulators of apoptosis are simultaneously implicated, thus permitting death defects of melanoma cells to be bypassed or overcome. On these bases, we hypothesize that pyrimethamine could represent an interesting candidate for the treatment of metastatic melanoma.
authors.affiliation: Department of Drug Research and Evaluation, Istituto Superiore di Sanità, Rome, Italy.
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Giammarioli
authors.forename: Angela
authors.initials: A
authors.lastname: Maselli
authors.forename: Andrea
authors.initials: A
authors.lastname: Casagrande
authors.forename: Lucrezia
authors.initials: L
authors.lastname: Gambardella
authors.forename: Angelo
authors.initials: A
authors.lastname: Gallina
authors.forename: Massimo
authors.initials: M
authors.lastname: Spada
authors.forename: Antonello
authors.initials: A
authors.lastname: Giovannetti
authors.forename: Enrico
authors.initials: E
authors.lastname: Proietti
authors.forename: Walter
authors.initials: W
authors.lastname: Malorni
authors.forename: Marina
authors.initials: M
authors.lastname: Pierdominici
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000502:physiology*; D002403:Cathepsins / Q000502:physiology*; D049109:Cell Proliferation / Q000187:drug effects; D005260:Female; D005493:Folic Acid Antagonists / Q000494:pharmacology; D006801:Humans; D008545:Melanoma / Q000201:enzymology / Q000473:pathology*; D051379:Mice; D016513:Mice, SCID; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009362:Neoplasm Metastasis; D011739:Pyrimethamine / Q000494:pharmacology*; D016196:S Phase / Q000187:drug effects; D047368:Tumor Burden / Q000187:drug effects; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D005493:Folic Acid Antagonists; D002403:Cathepsins; D020169:Caspases; D011739:Pyrimethamine