Trifluorothymidine resistance is associated with decreased thymidine kinase and equilibrative nucleoside transporter expression or increased secretory phospholipase A2.
Trifluorothymidine (TFT) is part of the novel oral formulation TAS-102, which is currently evaluated in phase II studies. Drug resistance is an important limitation of cancer therapy. The aim of the present study was to induce resistance to TFT in H630 colon cancer cells using two different schedules and to analyze the resistance mechanism. Cells were exposed either continuously or intermittently to TFT, resulting in H630-cTFT and H630-4TFT, respectively. Cells were analyzed for cross-resistance, cell cycle, protein expression, and activity of thymidine phosphorylase (TP), thymidine kinase (TK), thymidylate synthase (TS), equilibrative nucleoside transporter (hENT), gene expression (microarray), and genomic alterations. Both cell lines were cross-resistant to 2'-deoxy-5-fluorouridine (>170-fold). Exposure to IC(75)-TFT increased the S/G(2)-M phase of H630 cells, whereas in the resistant variants, no change was observed. The two main target enzymes TS and TP remained unchanged in both TFT-resistant variants. In H630-4TFT cells, TK protein expression and activity were decreased, resulting in less activated TFT and was most likely the mechanism of TFT resistance. In H630-cTFT cells, hENT mRNA expression was decreased 2- to 3-fold, resulting in a 5- to 10-fold decreased TFT-nucleotide accumulation. Surprisingly, microarray-mRNA analysis revealed a strong increase of secretory phospholipase-A2 (sPLA2; 47-fold), which was also found by reverse transcription-PCR (RT-PCR; 211-fold). sPLA2 inhibition reversed TFT resistance partially. H630-cTFT had many chromosomal aberrations, but the exact role of sPLA2 in TFT resistance remains unclear. Altogether, resistance induction to TFT can lead to different mechanisms of resistance, including decreased TK protein expression and enzyme activity, decreased hENT expression, as well as (phospho)lipid metabolism. Mol Cancer Ther; 9(4); 1047-57. (c)2010 AACR.
Temmink
Olaf H
OH
Department of Medical Oncology, VU University Medical Center, PO Box 7057, 1007 MB Amsterdam, the Netherlands.
Bijnsdorp
Irene V
IV
Prins
Henk-Jan
HJ
Losekoot
Nienke
N
Adema
Auke D
AD
Smid
Kees
K
Honeywell
Richard J
RJ
Ylstra
Bauke
B
Eijk
Paul P
PP
Fukushima
Masakazu
M
Peters
Godefridus J
GJ
D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D055028:Comparative Genomic Hybridization; D056915:DNA Copy Number Variations / Q000235:genetics; D015536:Down-Regulation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects* / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D033705:Equilibrative Nucleoside Transport Proteins / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D050356:Lipid Metabolism / Q000187:drug effects / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D054497:Phospholipases A2, Secretory / Q000378:metabolism*; D013937:Thymidine Kinase / Q000235:genetics / Q000378:metabolism*; D013940:Thymidylate Synthase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D014271:Trifluridine / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects
D004791:Enzyme Inhibitors; D033705:Equilibrative Nucleoside Transport Proteins; D013940:Thymidylate Synthase; D013937:Thymidine Kinase; D054497:Phospholipases A2, Secretory; D014271:Trifluridine