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Chlorogenic acid enhances the effects of 5-fluorouracil in human hepatocellular carcinoma cells through the inhibition of extracellular signal-regulated kinases.

ABSTRACT: There is an urgent need to search for novel chemosensitizers in the field of cancer therapy. Chlorogenic acid (CGA), a type of polyphenol present in the diet, has many biological activities. The present study is designed to explore the influence of CGA on the effects of 5-fluorouracil (5-FU) on human hepatocellular carcinoma cells (HepG2 and Hep3B). Treatment with 5-FU induced the inhibition of hepatocellular carcinoma cells' proliferation, and the combined treatment with CGA enhanced this inhibition. 5-FU also increased the production of reactive oxygen species (ROS). The combination of 5-FU and CGA led to a more prominent production of ROS and significantly inactivated ERK1/2, although CGA and 5-FU exerted no significant changes when used alone. A previous report has shown that ROS are upstream mediators that inactivate ERK in hepatocellular carcinoma cells. Combined with our results, this indicates that the combination of 5-FU and CGA leads to the inactivation of ERK through the overproduction of ROS. This mediates the enhancement of 5-FU-induced inhibition of hepatocellular carcinoma cells' proliferation, that is, CGA sensitizes hepatocellular carcinoma cells to 5-FU treatment by the suppression of ERK activation through the overproduction of ROS. CGA has shown potential as a chemosensitizer of 5-FU chemotherapy in hepatocellular carcinoma.

SUBMITTER: Yan Y

PROVIDER: S-EPMC4415958 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:AIM:To study the expression and phosphorylation of extracellular signal-regulated kinase (ERK) 1 and ERK2 in multidrug resistant (MDR) hepatocellular carcinoma (HCC) cells. METHODS:MDR HCC cell lines, HepG2/adriamycin (ADM) and SMMC7721/ADM, were developed by exposing parental cells to stepwise increasing concentrations of ADM. MTT assay was used to determine drug sensitivity. Flow cytometry was employed to analyze cell cycle distribution and measure cell P-glycoprotein (P-gp) and multidrug resistant protein 1 (MRP1) expression levels. ERK1 and ERK2 mRNA expression levels were measured by quantitative real-time PCR (QRT-PCR). Expression and phosphorylation of ERK1 and ERK2 were analyzed by Western blot. RESULTS:MTT assay showed that HepG2/ADM and SMMC7721/ADM were resistant not only to ADM, but also to multiple anticancer drugs. The P-gp expression was over 10-fold higher in HepG2/ADM cells than in HepG2 cells (8.92% +/- 0.22% vs 0.88% +/- 0.05%, P < 0.001) and over 4-fold higher in SMMC7721/ADM cells than in SMMC7721 cells (7.37% +/- 0.26% vs 1.74% +/- 0.25%, P < 0.001). However, the MRP1 expression was not significantly higher in HepG2/ADM and SMMC7721/ADM cells than in parental cells. In addition, the percentage of MDR HepG2/ADM and SMMC7721/ADM cells was significantly decreased in the G0/G1 phase and increased in the the S phase or G2/M phase. QRT-PCR analysis demonstrated that the ERK1 and ERK2 mRNA expression increased apparently in HepG2/ADM cells and decreased significantly in SMMC7721/ADM cells. Compared with the expression of parental cells, ERK1 and ERK2 protein expressions were markedly decreased in SMMC7721/ADM cells. However, ERK2 protein expression was markedly increased while ERK1 protein expression had no significant change in HepG2/ADM cells. Phosphorylation of ERK1 and ERK2 was markedly decreased in both HepG2/ADM and SMMC7721/ADM MDR cells. CONCLUSION:ERK1 and ERK2 activities are down-regulated in P-gp-mediated MDR HCC cells. ERK1 or ERK2 might be a potential drug target for circumventing MDR HCC cells.

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Chlorogenic acid enhances the effects of 5-fluorouracil in human hepatocellular carcinoma cells through the inhibition of extracellular signal-regulated kinases.

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