Genetic and epigenetic alterations of the reduced folate carrier in untreated diffuse large B-cell lymphoma.
The reduced folate carrier (RFC) is a transmembrane protein that mediates cellular uptake of reduced folates and antifolate drugs, including methotrexate (MTX). Acquired alterations of the RFC gene have been associated with resistance to MTX in cancer cell lines and primary osteosarcomas. Here, we examined RFC for mutations and promoter hypermethylation in (i) the inherently MTX-resistant lymphoma cell line (RL); (ii) 30 paired cases of acute lymphoblastic leukemia (ALL) obtained at diagnosis and at relapse after treatment with MTX; and (iii) 25 cases of diffuse large B-cell lymphoma (DLBCL) at diagnosis, none of which had been previously exposed to MTX. Aberrant hypermethylation of the RFC promoter occurred in RL cells and two of the primary DLBCLs. In one additional DLBCL, a single-base substitution in RFC was identified, leading to the introduction of a premature termination codon (c.1396C>T; p.Q466X). A missense mutation affecting the 11th transmembrane domain of RFC (c.1250T>C; p.I417T) was found in one case of ALL at diagnosis. In ALL, RFC promoter hypermethylation was found neither at diagnosis nor at relapse and thus is not a common cause of low levels of RFC expression associated with adverse outcome. In DLBCL, genetic and epigenetic alterations of RFC were detected at diagnosis in the absence of a selective MTX pressure, suggesting that these alterations may possibly contribute to the development of lymphoma.
Kastrup
Ingelise Bjerring
IB
Institute of Cancer Biology, Danish Cancer Society, Copenhagen, Denmark.
Worm
Jesper
J
Ralfkiaer
Elisabeth
E
Hokland
Peter
P
Guldberg
Per
P
Grønbaek
Kirsten
K
D000293:Adolescent; D000328:Adult; D001706:Biopsy; D002648:Child; D002675:Child, Preschool; D018389:Codon, Nonsense; D019175:DNA Methylation; D004252:DNA Mutational Analysis; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D044127:Epigenesis, Genetic; D005260:Female; D006801:Humans; D016403:Lymphoma, Large B-Cell, Diffuse / Q000209:etiology / Q000235:genetics*; D008297:Male; D026901:Membrane Transport Proteins / Q000235:genetics*; D008727:Methotrexate; D008875:Middle Aged; D009154:Mutation; D020125:Mutation, Missense; D017354:Point Mutation; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma; D011401:Promoter Regions, Genetic; D058978:Reduced Folate Carrier Protein
D018389:Codon, Nonsense; D026901:Membrane Transport Proteins; D058978:Reduced Folate Carrier Protein; C548699:SLC19A1 protein, human; D008727:Methotrexate