The first two authors have equally contributed to this paper.
Reduced folate carrier mutations are not the mechanism underlying methotrexate resistance in childhood acute lymphoblastic leukemia
Article first published online: 23 DEC 2003
Copyright © 2003 American Cancer Society
Volume 100, Issue 4, pages 773–782, 15 February 2004
How to Cite
Kaufman, Y., Drori, S., Cole, P. D., Kamen, B. A., Sirota, J., Ifergan, I., Arush, M. W. B., Elhasid, R., Sahar, D., Kaspers, G. J. L., Jansen, G., Matherly, L. H., Rechavi, G., Toren, A. and Assaraf, Y. G. (2004), Reduced folate carrier mutations are not the mechanism underlying methotrexate resistance in childhood acute lymphoblastic leukemia. Cancer, 100: 773–782. doi: 10.1002/cncr.20018
- Issue published online: 3 FEB 2004
- Article first published online: 23 DEC 2003
- Manuscript Revised: 13 NOV 2003
- Manuscript Accepted: 13 NOV 2003
- Manuscript Received: 4 SEP 2003
- Star Foundation
- acute lymphoblastic leukemia (ALL);
- methotrexate (MTX);
- reduced folate carrier (RFC);
- drug transport;
- drug resistance
Although the majority of children with acute lymphoblastic leukemia (ALL) are cured with combination chemotherapy containing methotrexate (MTX), drug resistance contributes to treatment failure for a substantial fraction of patients. The primary transporter for folates and MTX is the reduced folate carrier (RFC). Impaired drug transport is a documented mechanism of MTX resistance in patients with ALL; however, to the authors' knowledge it is not known whether inactivating RFC mutations are a contributing factor.
The authors devised a genomic polymerase chain reaction-single strand conformational polymorphism assay followed by sequencing and screened the entire RFC coding region for sequence alterations in DNA from 246 leukemia specimens from patients with diverse ethnic variation, 24 at the time of recurrence and the rest at the time of diagnosis. This cohort was comprised of 203 B-precursor ALL specimens (82.5%), 32 T-lineage ALL specimens (13%), and 11 acute myeloblastic leukemia specimens (4.5%).
Of 246 DNA samples, only 3 diagnosis B-precursor ALL specimens (1.2%) were found to harbor alterations in the RFC gene, including heterozygous single nucleotide changes resulting in D56H and D522N substitutions in the first extracellular loop and the C-terminus of this transporter, respectively. The third sample had a sequence alteration in exon 3 that could not be identified because of the lack of availability of DNA.
Whereas inactivating RFC mutations are a frequent mechanism of MTX resistance in human leukemia cell lines and in patients with osteosarcoma, they are not common and do not appear to play any significant role in intrinsic or acquired resistance to MTX in childhood leukemia. This is the first study of RFC mutations in multiple pediatric leukemia specimens. Cancer 2004;100:773–82. © 2003 American Cancer Society.