Mode of action of methotrexate-albumin in a human T-cell leukemia line and activity against an MTX-resistant clone.

Abstract

Limitations of low mol. wt anticancer drugs are short tumor exposure times and toxicity to normal tissue. Methotrexate (MTX) covalently linked to human serum albumin (HSA) as a macromolecular carrier caused tumor regressions concomitant with a favorable toxicity profile in a clinical phase I trial (Hartung et aL, Clin. Cancer Res., 1999, 5, 753). We examined the uptake, intracellular degradation, metabolism and thymidylate synthase (TS) inhibition of MTX-HSA in the T-cell leukemia line CCRF-CEM and the MTX transport resistant clone CCRF-CEM/MTX. The number of MTX molecules per albumin molecule was determined by electrospray mass spectrometry. A loading ratio (LR) of approximately 1.4 mol MTX/albumin revealed intact complexes with one and two MTX molecules/albumin. In the complex with an LR of 5.7, albumin with up to 16 MTX molecules was seen. MTX-HSA was taken up by CCRF-CEM cells via endocytosis and cleaved by lysosomal enzymes. Liberated MTX was a poor substrate of folylpolyglutamate synthetase and was exported into the medium. TS was inhibited and cell survival was impaired by MTX-HSA in a time- and concentration-dependent manner. CCRF-CEM/MTX cells exhibited a growth inhibition of 30-40% after MTX-HSA treatment, but no TS inhibition. The alternative uptake route via endocytosis enables MTX-HSA to overcome transport resistance to MTX.

• Authors: M Weigand, G Hartung, J Roboz, S Sieger, M Wolf, H Sinn, H H Schrenk, M Wiessler, E Frei
• Journal: Anti-cancer drug design (Anticancer Drug Des) 2001 Aug-Oct Vol. 16 Issue 4-5 Pg. 227-37 ISSN: 0266-9536 [Print] United States
• PMID: 12049481 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antimetabolites, Antineoplastic
• Carrier Proteins
• Serum Albumin
• Polyglutamic Acid
• Thymidylate Synthase
• Methotrexate

Topics

• Antimetabolites, Antineoplastic (metabolism, pharmacology)
• Carrier Proteins (genetics, metabolism)
• Clone Cells
• Drug Resistance, Neoplasm
• Humans
• Immunochemistry
• Leukemia, T-Cell (drug therapy, pathology)
• Lysosomes (metabolism)
• Methotrexate (metabolism, pharmacology)
• Molecular Weight
• Polyglutamic Acid (metabolism)
• Protein Binding
• Serum Albumin (pharmacology)
• Spectrometry, Mass, Electrospray Ionization
• Survival Analysis
• Thymidylate Synthase (metabolism)
• Tumor Cells, Cultured