The inverse relationship between reduced folate carrier function and pemetrexed activity in a human colon cancer cell line.

Abstract

Pemetrexed, a new generation antifolate recently approved for the treatment of mesothelioma and non-small cell lung cancer, is an excellent substrate for the reduced folate carrier (RFC). To explore the carrier's effect on pemetrexed activity, RFC was inactivated in HCT-15 colon cancer cells by mutagenesis and PT632 selective pressure. A clone (PT1) was obtained with a glycine to arginine substitution at amino acid 401, resulting in the loss of RFC function. PT1 cells were resistant to PT632 (178-fold), methotrexate (4-fold), and ZD1694 (Tomudex, raltitrexed; 20-fold), but were 3-fold collaterally sensitive to pemetrexed when grown in 25 nmol/L of 5-formyltetrahydrofolate. PT1 cells transfected with wild-type RFC had antifolate sensitivities comparable to that of wild-type HCT-15 cells, indicating that the RFC mutation was the sole basis for resistance. Folate pools were contracted in PT1 cells by 32% or 60%, as measured by radiolabeling intracellular folates or by an enzyme binding assay, respectively. This was reflected in marked (6.5-fold) collateral sensitivity to trimetrexate. The initial uptake of pemetrexed in PT1 cells was markedly reduced ( approximately 85%) but intracellular pemetrexed levels increased to approximately 60% and approximately 70% to that of wild-type cells after 2 hours and 6 days, respectively. There was increased pemetrexed inhibition of glycinamide ribonucleotide transformylase and, to a lesser extent, thymidylate synthase in PT1 cells growing in 5-formyltetrahydrofolate based on nucleoside protection analyses. Hence, loss of RFC function leads to collateral sensitivity to pemetrexed in HCT-15 cells, likely due to cellular folate pool contraction resulting in partial preservation of pemetrexed polyglutamylation and increased target enzyme inhibition. micro

• Authors: Shrikanta Chattopadhyay, Rongbao Zhao, Sergey A Krupenko, Natalia Krupenko, I David Goldman
• Journal: Molecular cancer therapeutics (Mol Cancer Ther) Vol. 5 Issue 2 Pg. 438-49 (Feb 2006) ISSN: 1535-7163 [Print] United States
• PMID: 16505119 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Antineoplastic Agents
• Carrier Proteins
• Folate Receptors, GPI-Anchored
• Folic Acid Antagonists
• Glutamates
• Purines
• Pyrimidines
• Quinazolines
• Receptors, Cell Surface
• Thiophenes
• Pemetrexed
• Guanine
• Arginine
• Thymidylate Synthase
• Phosphoribosylglycinamide Formyltransferase
• raltitrexed
• Leucovorin
• Glycine
• Methotrexate

Topics

• Amino Acid Substitution
• Antineoplastic Agents (metabolism)
• Arginine (chemistry, genetics)
• Carrier Proteins (genetics, metabolism)
• Cell Line, Tumor
• Colonic Neoplasms (genetics, metabolism)
• Drug Resistance, Neoplasm (genetics)
• Folate Receptors, GPI-Anchored
• Folic Acid Antagonists (pharmacology)
• Glutamates (metabolism)
• Glycine (chemistry, genetics)
• Guanine (agonists, analogs & derivatives, metabolism)
• Humans
• Leucovorin (metabolism)
• Methotrexate (metabolism)
• Mutation
• Pemetrexed
• Phosphoribosylglycinamide Formyltransferase (antagonists & inhibitors)
• Purines (pharmacology)
• Pyrimidines (pharmacology)
• Quinazolines (metabolism)
• Receptors, Cell Surface (genetics, metabolism)
• Thiophenes (metabolism)
• Thymidylate Synthase (antagonists & inhibitors)