Low cytosine triphosphate synthase 2 expression renders resistance to 5-fluorouracil in colorectal cancer

Item Type:	Article
Title:	Low cytosine triphosphate synthase 2 expression renders resistance to 5-fluorouracil in colorectal cancer
Creators Name:	Tan, W.L. and Bhattacharya, B. and Loh, M. and Balasubramanian, I. and Akram, M. and Dong, D. and Wong, L. and Thakkar, B. and Salto-Tellez, M. and Soo, R.A. and Fichtner, I. and Iacopetta, B. and Soong, R.
Abstract:	Understanding the determinants of resistance of 5-fluorouracil (5FU) is of significant value to optimising administration of the drug, and introducing novel agents and treatment strategies. Here, the expression of 92 genes involved in 5FU transport, metabolism, co-factor (folate) metabolism and downstream effects was measured by real-time PCR low density arrays in 14 patient-derived colorectal cancer xenografts characterised for 5FU resistance. Candidate gene function was tested by siRNA and uridine modulation, and immunoblotting, apoptosis and cell cycle analysis. Predictive significance was tested by immunohistochemistry of tumours from 125 stage III colorectal cancer patients treated with and without 5FU. Of 8 genes significantly differentially expressed between 5FU sensitive and resistant xenograft tumours, CTPS2 was the gene with the highest probability of differential expression (p=0.008). Reduction of CTPS2 expression by siRNA increased the resistance of colorectal cancer cell lines DLD1 and LS174T to 5FU and its analogue, FUDR. CTPS2 siRNA significantly reduced cell S-phase accumulation and apoptosis following 5FU treatment. Exposure of cells to uridine, a precursor to the CTPS2 substrate uridine triphosphate, also increased 5FU resistance. Patients with low CTPS2 did not gain a survival benefit from 5FU treatment (p=0.072), while those with high expression did (p=0.003). Low CTPS2 expression may be a rationally-based determinant of 5FU resistance. : See commentary: : Biomarkers of 5-FU response in colon cancer.
Keywords:	5-Fluorouracil, Cytidine Triphosphate Synthase, Drug Resistance, Pharmacogenomics, Fluoropyrimidine, Antimetabolites, Pathway Analysis, Animals, Mice
Source:	Cancer Biology & Therapy
ISSN:	1538-4047
Publisher:	Landes Bioscience
Volume:	11
Number:	6
Page Range:	599-608
Date:	15 March 2011
Official Publication:	https://doi.org/10.4161/cbt.11.6.14670
PubMed:	View item in PubMed

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