Artikel
Inhibition of the epidermal growth factor receptor reverses ATP-binding cassette protein mediated multi-drug resistance in hepatocellular carcinoma
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Veröffentlicht: | 20. Mai 2011 |
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Introduction: Signalling through the epidermal growth factor receptor (EGFR) activated tyrosine kinase cascade and over-expression of multi-drug resistance mediating ATP-binding cassette proteins (ABC transport proteins) play an important role in the development of hepatocellular carcinoma (HCC). Recent evidence suggests an involvement of the EGFR in the regulation of multi-drug resistance in cancer cells. The aim of this study was to systematically explore the effect of EGFR-inhibition in multi-drug resistant HCC cells that overexpress ABC transport proteins.
Materials and methods: Drug resistant HepG2 and HuH7 cells were developed by escalating concentrations of chemotherapeutic agents in the culture media. The effects of EGFR inhibition were investigated by MTT-assay, rhodamine up-take assay, quantitative RT-PCR and western blot.
Results: Treatment with gemcitabine or doxorubicin induces multi-drug resistance and significantly increases the ABC-transport protein expression and function in a time- and dose-dependent manner. Additionally, conventional chemotherapy increased the mRNA expression of tyrosine kinases by up to 50% and enhanced the phosphorylation of ERK. Activation of the tyrosine kinase pathway by EGF increased the multi-drug resistance, up-regulated the ABC-transporter mRNA expression up to 3-fold and enhanced the survival of resistant HCC cells. Consistent with these effects, inhibition of the EGFR using siRNA decreased the ABC transporter protein mRNA expression by up to 56% and inhibited the proliferation of resistant cells. Gefitinib, a clinically approved EGFR inhibitor, restored the chemosensitivity of resistant HCC cells. Simultaneous treatment with Gefitinib caused a dose-dependent reversal of resistance to conventional chemotherapy in HepG2 and HuH7 cells by reducing the mRNA expression and inhibiting the efflux function of ABC transport proteins.
Conclusion: These data provide fort he first time evidence that the multi-drug resistance of HCC is modulated through the EGFR-activated tyrosine kinase cascade. Consequentially, the restoration of chemosensitivity by EGFR inhibition can lead towards new tailored therapies in patients with highly resistant tumors.