Study On The Mechanism By Which MEF2D Induces The Resistance Of Hepatocellular Carcinoma To Sorafenib

Obiective:Sorafenib is the first choice for liver cancer treatment,but the drug resistance limits its clinical efficacy.In spite of some advances,the underlying mechanism is still far from complete elucidation.To explore the underlying mechanism of sorafenib resistance and the role of MEF2 D in this process in molecular and cellular level.To further confirm that MEF2 D increased the sorafenib resistance of liver cancers via inhibiting SPRY4 thus activating RAS/ERK pathway.Methods: Firstly,sorafenib-resistant cell strain was established by intermittently exposure to sorafenib.And the morphological changes of sorafenib-resisitant cell were observed under the microscope.Then MTT assay was utilized to valid the resistance index of sorafenib-resistant cell strain.Western blotting was used to detect the expression level of MEK,ERK,p-ERK and MEF2 D of sorafenib-sensitive and sorafenib-resistant strains.In order to address the role of MEF2 D in sorafenib resistant cells,we either utilize RNAi to silence MEF2 D in sorafenib-resistant hepatocarcinoma cells or overexpress MEF2 D in sorafenib-sensitive hepatocarcinoma cells.Then western blot were performed to observe the change of expression level of MEK?p-MEK?ERK?p-ERK?MEF2D.And CCK-8 assay was performed to evaluate the cell viability of sorafenib-resistant strain or sorafenib-sensitive strain after administration of sorafenib.In addition,western blot and RT-PCR were performed to examine the protein and m RNA expression level of SPRY4 in sorafenib-sensitive and sorafenib-resistant strains.Results: Morphological changes observed under microscope and MTT assay results revealed that sorafenib-resistant cell strain was established.The expression levels of MEF2D?p-MEK and p-ERK were significantly higher in sorafenib-resistant hepatocarcinoma cells than sorafenib-sensitive hepatocarcinoma cells.Slienced MEF2 D in sorafenib-resistant hepatocarcinoma cells caused the decrease of p-ERK and p-MEK,thus decreased the resistance of cancer cells to sorafenib.On the contrary,overexpression of MEF2 D in sorafenib-sensitive hepatocarcinoma cells caused a significant elevation of p-ERK and p-MEK.As a result,the ability of these cells to resist sorafenib was increased.In addition,the changes of MEF2 D level triggered an opposite tendency to SPRY4,a negative modulator of RAS/ERK signaling.Conclusion: MEF2 D strengthened the activity of ERK via negatively modulating SPRY4,thus promoting the development of sorafenib resistance.