title: Low-dose methotrexate enhances cycling of highly anaplastic cancer cells.
abstract: We previously showed that cellular RedOx state governs the G1-S transition of AH130 hepatoma, a tumor spontaneously reprogrammed to the embryonic stem cell stage. This transition is impaired when the mithocondrial electron transport system is blocked by specific inhibitors (antimycin A) or the respiratory chain is saturated by adding to the cells high concentrations of pyruvate. The antimycin A or pyruvate block is removed by the addition of adequate concentrations of folate (F). This suggests that the G1-S transition of AH130 cells depends on a respiration-linked step of DNA synthesis related to folate metabolism. In the study reported here, we characterized the effects of methotrexate (MTX), an inhibitor of dihydofolate-reductase, on the G1-S transition of hepatoma cells, in the absence or the presence of exogenously added F, dihydrofolate (FH2) or tetrahydrofolate (FH4). MTX, at 1 μM or higher concentrations, inhibited G1-S transition. This inhibition was completely removed by exogenous folates. Surprisingly, 10 nM MTX stimulated G1-S transition. The addition of F, but not FH2or FH4, significantly increased this effect. Furthermore, 10 nM MTX removed the block of the G1-S transition operated by antimycin A or pyruvate, an effect which was enhanced in the presence of F. Finally, the stimulatory effect of 10 nM MTX was inhibited in the presence of serine. Our findings indicated that, under certain conditions, MTX may stimulate, rather than inhibiting, the cycling of cancer cells exhibiting a stem cell-like phenotype, such as AH130 cells. This may impact the therapeutic use of MTX and of folates as supportive care.
authors.affiliation: a Department of Experimental and Clinical Biomedical Sciences "Mario Serio ," Università degli Studi di Firenze , Florence , Italy.
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Cipolleschi
authors.affiliation: a Department of Experimental and Clinical Biomedical Sciences "Mario Serio ," Università degli Studi di Firenze , Florence , Italy.
authors.forename: Ilaria
authors.initials: I
authors.lastname: Marzi
authors.affiliation: a Department of Experimental and Clinical Biomedical Sciences "Mario Serio ," Università degli Studi di Firenze , Florence , Italy.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Rovida
authors.affiliation: a Department of Experimental and Clinical Biomedical Sciences "Mario Serio ," Università degli Studi di Firenze , Florence , Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Olivotto
authors.affiliation: a Department of Experimental and Clinical Biomedical Sciences "Mario Serio ," Università degli Studi di Firenze , Florence , Italy.
authors.forename: Persio
authors.initials: P
authors.lastname: Dello Sbarba
mesh_terms: D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D002453:Cell Cycle / Q000187:drug effects*; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D005492:Folic Acid / Q000378:metabolism; D008297:Male; D053858:Metabolic Networks and Pathways / Q000187:drug effects; D008727:Methotrexate / Q000494:pharmacology*; D009369:Neoplasms / Q000473:pathology*; D017208:Rats, Wistar
chemical_list: D000596:Amino Acids; D005492:Folic Acid; D008727:Methotrexate
keywords: cancer stem cells; cell cycle; folates; glycine; methotrexate; serine