Multidrug resistance genes in infant acute lymphoblastic leukemia: Ara-C is not a substrate for the breast cancer resistance protein.
Infants with acute lymphoblastic leukemia (ALL) are more resistant to chemotherapeutic drugs than older children with ALL, except for Ara-C. Drug resistance mechanisms in infant ALL, however, remain unknown. Possibly, multidrug resistance (MDR) proteins like P-glycoprotein, MDR-associated protein (MRP1), lung resistance-related protein (LRP/MVP) and the breast cancer resistance protein (BCRP) play a role. Accordingly, we measured the mRNA levels of these proteins in infants (n=13) and non-infants (n=13) with ALL, using quantitative RT-PCR. Infants expressed 2.4-fold less BCRP mRNA (P=0.009) than non-infants with ALL. MDR1, MRP1 and LRP/MVP expression did not differ between both groups. MDR gene expression levels did not correlate to prednisolone, vincristine, daunorubicin or Ara-C cytotoxicity, except for BCRP expression, which correlated with resistance to Ara-C (Rs=0.53, P=0.012), suggesting that Ara-C might be a BCRP substrate. However, culturing patients ALL cells in the presence of the BCRP inhibitor Ko143 had no effect on Ara-C sensitivity. Inhibiting Bcrp1 in the Mdr1a-, Mdr1b- and Mrp1-deficient and Bcrp1-overexpressing mouse cell line Mef3.8/T6400, also did not modulate Ara-C cytotoxicity. Therefore, we conclude that Ara-C is not a substrate for BCRP and that MDR proteins do not play a significant role in drug resistance in infant ALL.
Department of Pediatric Oncology/Hematology, Erasmus MC/Sophia Children's Hospital, Rotterdam, The Netherlands. r.stam@erasmusmc.nl
R W
RW
Stam
M M
MM
van den Heuvel-Eibrink
M L
ML
den Boer
M E G
ME
Ebus
G E
GE
Janka-Schaub
J D
JD
Allen
R
R
Pieters
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics*; D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D003561:Cytarabine / Q000378:metabolism*; D018432:Drug Resistance, Multiple / Q000235:genetics*; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005347:Fibroblasts / Q000378:metabolism; D015973:Gene Expression Regulation, Leukemic; D006801:Humans; D007223:Infant; D051379:Mice; D009363:Neoplasm Proteins / Q000235:genetics*; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019772:Topotecan / Q000494:pharmacology; D020394:Vault Ribonucleoprotein Particles / Q000235:genetics; D000099187:Major Vault Protein
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D000964:Antimetabolites, Antineoplastic; D000970:Antineoplastic Agents; D003561:Cytarabine; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D019772:Topotecan; D020394:Vault Ribonucleoprotein Particles; D000099187:Major Vault Protein; C116614:ABCG2 protein, human