Enhancement of 5-fluorouracil-induced cytotoxicity by leucovorin in 5-fluorouracil-resistant gastric cancer cells with upregulated expression of thymidylate synthase

Ayako Nakamura,Yurin Kondoh,Toshinori Kanemura,Masakazu Yamamoto,Ryuji Okuyama,Teiji Takechi,Go Nakajima,Hidekazu Kuramochi,Kazuhiko Hayashi

doi:10.1007/s10120-013-0249-7

Ayako Nakamura, Yurin Kondoh + Show 7 more

Open Access

https://doi.org/10.1007/s10120-013-0249-7

Copy DOI

Abstract

BackgroundElucidation of the mechanisms by which gastric cancer cells acquire resistance to 5-fluorouracil (5FU) may provide important clues to the development of effective chemotherapy for 5FU-resistant gastric cancerMethodsFour 5FU-resistant cell lines (MKN45/5FU, MKN74/5FU, NCI-N87/5FU, and KATOIII/5FU) were established by continuous exposure of the cells to progressively increasing concentrations of 5FU for about 1 year. Then, mRNA expression levels of four genes associated with 5FU metabolism, i.e., thymidylate synthase (TS), dihydropyrimidine dehydrogenase, thymidine phosphorylase, and orotate phosphoribosyltransferase, were quantitatively evaluated by real-time reverse transcriptase-polymerase chain reaction. In addition, TS protein expression was measured by Western blot analysis.ResultsAs compared with the parent cell lines, the 5FU-resistant cell lines showed 3.8- to 11.6-fold higher resistance to 5FU, as well as 1.9- to 3.5-fold higher TS mRNA expression and 1.6- to 7.1-fold higher TS protein expression. In contrast, the expressions of other genes did not differ significantly among the cell lines. The cytotoxicity of 5FU was enhanced 2.3- to 2.8 fold by leucovorin (LV) against three of the four 5FU-resistant cell lines.ConclusionsCollectively, LV enhanced the cytotoxicity of 5FU not only against the parent gastric cancer cell lines, but also against the 5FU-resistant cell lines, even those with elevated TS expression levels. These results suggest that clinical studies of a combination of 5FU and LV are warranted in patients who have recurrent gastric cancer after 5FU-based therapy.

Highlights

Worldwide, gastric cancer ranks third among males and fifth among females among all causes of death from cancer [1]
Collectively, LV enhanced the cytotoxicity of 5FU against the parent gastric cancer cell lines, and against the 5FU-resistant cell lines, even those with elevated Thymidylate synthase (TS) expression levels
These results suggest that clinical studies of a combination of 5FU and LV are warranted in patients who have recurrent gastric cancer after 5FU-based therapy

Summary

Introduction

Gastric cancer ranks third among males and fifth among females among all causes of death from cancer [1]. Significant survival benefits of 5-fluorouracil (5FU)based chemotherapy have been reported in patients with metastatic gastric cancer as well as those who have undergone surgery [2,3,4,5]. Such regimens have improved response, many patients have recurrence after. Several clinical studies have examined the relationships of clinical response and survival to the tumor expression levels of TS and other enzymes involved in 5FU metabolism, such as dihydropyrimidine dehydrogenase (DPD), thymidine phosphorylase (TP), and orotate phosphoribosyltransferase (OPRT), in patients with cancer who received 5FU-based chemotherapy [9,10,11,12].

Methods

Results

Conclusion