p14ARF expression increases dihydrofolate reductase degradation and paradoxically results in resistance to folate antagonists in cells with nonfunctional p53 Journal Article
| Authors: | Magro, P. G.; Russo, A. J.; Li, W. W.; Banerjee, D.; Bertino, J. R. |
| Article Title: | p14ARF expression increases dihydrofolate reductase degradation and paradoxically results in resistance to folate antagonists in cells with nonfunctional p53 |
| Abstract: | The p14ARF protein, the product of an alternate reading frame of the INK4A/ARF locus on human chromosome 9p21, disrupts the ability of MDM2 to target p53 for proteosomal degradation and causes an increase in steady-state p53 levels, leading to a G1 and G2 arrest of cells in the cell cycle. Although much is known about the function of p14ARF in the p53 pathway, not as much is known about its function in human tumor growth and chemosensitivity independently of up-regulation of p53 protein levels. To learn more about its effect on cellular proliferation and chemoresistance independent of p53 up-regulation, human HT-1080 fibrosarcoma cells null for p14ARF and harboring a defective p53 pathway were stably transfected with p14ARF cDNA under the tight control of a doxycycline-inducible promoter. Induction of p14ARF caused a decrease in cell proliferation rate and colony formation and a marked decrease in the level of dihydrofolate reductase (DHFR) protein. The effect of p14ARF on DHFR protein levels was specific, because thymidylate kinase and thymidylate synthase protein levels were not decreased nor were p53 or p21WAF1 protein levels increased. The decrease in DHFR protein was abolished when the cells were treated with the proteasome inhibitor MG132, demonstrating that p14ARF augments proteasomal degradation of the protein. Surprisingly, induction of p14 ARF increased resistance to the folate antagonists methotrexate, trimetrexate, and raltitrexed. Depletion of thymidine in the medium reversed this resistance, indicating that p14ARF induction increases the reliance of these cells on thymidine salvage. |
| Keywords: | cancer chemotherapy; controlled study; unclassified drug; human cell; genetics; methotrexate; cell proliferation; metabolism; cell division; benzyloxycarbonylleucylleucylleucinal; protein stability; chromosome 9p; drug effect; drug resistance; enzymology; pathology; drug resistance, neoplasm; enzyme activity; chemosensitivity; cell line, tumor; protein p53; physiology; biosynthesis; drug antagonism; fibrosarcoma; messenger rna; tumor cell line; western blotting; cancer stem cell; tumor suppressor protein p53; cell cycle g2 phase; tumor suppressor protein p14arf; tumor growth; dihydrofolate reductase; folic acid antagonist; thymidylate synthase; folic acid antagonists; tetrahydrofolate dehydrogenase; quinazolines; fluorescence activated cell sorting; phosphotransferase; quinazoline derivative; cell cycle g1 phase; complementary dna; thymidine; protein mdm2; protein synthesis inhibition; enzyme stability; colony formation; thiophene derivative; thiophenes; raltitrexed; trimetrexate; protein p14arf; tumor stem cells; humans; human; priority journal; article; thymidylate kinase |
| Journal Title: | Cancer Research |
| Volume: | 64 |
| Issue: | 12 |
| ISSN: | 0008-5472 |
| Publisher: | American Association for Cancer Research |
| Date Published: | 2004-06-15 |
| Start Page: | 4338 |
| End Page: | 4345 |
| Language: | English |
| DOI: | 10.1158/0008-5472.can-03-1045 |
| PROVIDER: | scopus |
| PUBMED: | 15205349 |
| DOI/URL: | |
| Notes: | Cancer Res. -- Cited By (since 1996):13 -- Export Date: 16 June 2014 -- CODEN: CNREA -- Source: Scopus |
