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1.
J Exp Clin Cancer Res ; 41(1): 45, 2022 Feb 01.
Article in English | MEDLINE | ID: mdl-35105345

ABSTRACT

BACKGROUND: Multiple myeloma (MM) remains an incurable cancer despite advances in therapy. Therefore, the search for new targets is still essential to uncover potential treatment strategies. Metabolic changes, induced by the hypoxic bone marrow, contribute to both MM cell survival and drug resistance. Pyrroline-5-carboxylate reductase 1 and 2 (PYCR1 and PYCR2) are two mitochondrial enzymes that facilitate the last step in the glutamine-to-proline conversion. Overexpression of PYCR1 is involved in progression of several cancers, however, its' role in hematological cancers is unknown. In this study, we investigated whether PYCR affects MM viability, proliferation and response to bortezomib. METHODS: Correlation of PYCR1/2 with overall survival was investigated in the MMRF CoMMpass trial (653 patients). OPM-2 and RPMI-8226 MM cell lines were used to perform in vitro experiments. RPMI-8226 cells were supplemented with 13C-glutamine for 48 h in both normoxia and hypoxia (< 1% O2, by chamber) to perform a tracer study. PYCR1 was inhibited by siRNA or the small molecule inhibitor pargyline. Apoptosis was measured using Annexin V and 7-AAD staining, viability by CellTiterGlo assay and proliferation by BrdU incorporation. Differential protein expression was evaluated using Western Blot. The SUnSET method was used to measure protein synthesis. All in vitro experiments were performed in hypoxic conditions. RESULTS: We found that PYCR1 and PYCR2 mRNA expression correlated with an inferior overall survival. MM cells from relapsed/refractory patients express significantly higher levels of PYCR1 mRNA. In line with the strong expression of PYCR1, we performed a tracer study in RPMI-8226 cells, which revealed an increased conversion of 13C-glutamine to proline in hypoxia. PYCR1 inhibition reduced MM viability and proliferation and increased apoptosis. Mechanistically, we found that PYCR1 silencing reduced protein levels of p-PRAS40, p-mTOR, p-p70, p-S6, p-4EBP1 and p-eIF4E levels, suggesting a decrease in protein synthesis, which we also confirmed in vitro. Pargyline and siPYCR1 increased bortezomib-mediated apoptosis. Finally, combination therapy of pargyline with bortezomib reduced viability in CD138+ MM cells and reduced tumor burden in the murine 5TGM1 model compared to single agents. CONCLUSIONS: This study identifies PYCR1 as a novel target in bortezomib-based combination therapies for MM.


Subject(s)
Antineoplastic Agents/therapeutic use , Bortezomib/therapeutic use , Multiple Myeloma/drug therapy , Protein Synthesis Inhibitors/therapeutic use , Pyrroline Carboxylate Reductases/therapeutic use , Animals , Antineoplastic Agents/pharmacology , Bortezomib/pharmacology , Cell Proliferation , Humans , Mice , Multiple Myeloma/mortality , Multiple Myeloma/pathology , Protein Synthesis Inhibitors/pharmacology , Pyrroline Carboxylate Reductases/pharmacology , Survival Analysis
2.
Exp Eye Res ; 41(6): 767-75, 1985 Dec.
Article in English | MEDLINE | ID: mdl-3841659

ABSTRACT

Addition of pyrroline-5-carboxylate (P5C) or its precursors to rat lenses cultured for 24 hr in TC-199 medium containing 14C-glucose results in an apparent concentration-dependent increase in hexose monophosphate-pentose (HMP) pathway activity. Addition of proline, the reduction product of P5C, did not result in an increase, suggesting that stimulation of the HMP pathway is related to the reduction of P5C to proline by the enzyme P5C reductase. No apparent feedback inhibition on P5C reductase was observed. Stimulation of HMP pathway activity by P5C was also observed in the lenses of Philly and Nakano mouse, two models of congenital osmotic cataracts. Compared with its genetic control, the Swiss--Webster mouse, generally no difference in the lenticular levels of HMP pathway activity was observed in the Philly mouse--even after the onset of cataract. Stimulation of the HMP pathway in the Philly lens by P5C, however, was consistently lower than its control. In the lenses from the Nakano mouse and its genetic control, the Balb/c mouse, no difference in the percentage stimulation of the HMP pathway resulting from the addition of P5C was observed, but HMP pathway activity in the Nakano lens was consistently lower than that of the control.


Subject(s)
Lens, Crystalline/enzymology , Oxidoreductases Acting on CH-NH Group Donors/pharmacology , Pentose Phosphate Pathway/drug effects , Pyrroline Carboxylate Reductases/pharmacology , Aging , Animals , Female , Glucose/metabolism , Glutamine/pharmacology , Male , Mice , Mice, Inbred Strains , Ornithine/pharmacology , Proline/metabolism , Pyrroles/pharmacology , Rats , Rats, Inbred Strains
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