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[Relationship between the level of RRM1 expression and the sensitivity to gemcitabine in the esophageal squamous cell carcinoma cell lines].

OBJECTIVE
Ribonucleotide reductase subunit M1 (RRM1) is the intracellular target of gemcitabine (GEM). The aim of this study is to explore the relationship between the level of RRM1 expression and the sensitivity to GEM in the esophageal squamous cell carcinoma cell lines.


METHODS
Four esophageal squamous cell carcinoma cell lines (Kyse-150, Kyse-450, 9706 and Eca-109) were cultured in vitro. In the same period, RRM1 expression level was measured by RT-PCR and Western blot, and cell sensitivity to GEM was determined by CCK-8 assay. The relation between cell sensitivity and RRM1 expression was further analyzed. Kyse-450 cells were continuously cultured in the medium containing 50 nM GEM. RRM1 expression was measured at different time points to monitor the dynamic changes in the surviving cells. Inhibition of RRM1 expression by RNAi method was applied and the effect on GEM-sensitivity was further examined.


RESULTS
The IC(50) of Eca-109, Kyse-150, Kyse-450 and 9706 cells were (0.92 +/- 0.17), (0.48 +/- 0.11), (0.29 +/- 0.06) and (0.02 +/- 0.01) mmol/L, respectively. The expressions of RRM1 protein and mRNA of Eca-109 cell line were the highest detected by Western blot and RT-PCR, followed by Kyse-150 and Kyse-450, and the lowest one was 9706 cell line. When Kyse-450 cells were continuously treated with 50 nmol/L GEM, the level of RRM1 protein was increasing in the surviving cells. RRM1 siRNA could effectively knock down the expression of RRM1 and significantly increase the cell sensitivity to GEM (P = 0.035).


CONCLUSION
The level of RRM1 expression correlates with the cell sensitivity to gemcitabine. The cells with a lower level of RRM1 expression are more sensitive to gemcitabine.