Silencing Of ERK5 Reverses Adriamycin Resistance In Human Breast Cancer Cells MCF-7/ADM

Background:According to the World Health Organization(WHO)International Agency for Research on Cancer(IARC)newly released report on the global burden of cancer in 2020,the number of new cases of breast cancer is as high as 2.26 million,surpassing lung cancer as the largest number of malignant tumors in the world.And the number of deaths reached 680,000,making it the deadliest malignancy in women.Breast cancer is mainly treated with surgery,accompanied by radiotherapy and chemotherapy,endocrine therapy and targeted therapy.Although due to the rapid development of modern medicine and the improvement of people’s awareness of cancer screening,the early diagnosis and treatment of breast cancer has been greatly improved compared with the past,and the mortality rate has decreased significantly.However,drug resistance of breast cancer has a very high proportion in clinical treatment of breast cancer,which is an important reason for poor treatment effect,recurrence and metastasis of breast cancer.Therefore,it is of great significance to search for target genes regulating drug resistance in breast cancer.Extracellular signal-regulated kinase 5(ERK5)is a member of the mitogen-activated protein kinase(MAPK)family.It is composed of 816 amino acids and has a molecular weight of about 110kDa.ERK5 is an important kinase for normal cell survival,growth,proliferation,migration and differentiation.At the same time,more and more studies have shown that it is also involved in the invasion,metastasis and drug resistance of tumor cells.In this study,it was found that the expression of ERK5 was significantly increased in adriamycin-resistant breast cancer cells MCF-7/ADM.After that,the expression of ERK5 was knocked down in MCF-7/ADM cells of the experimental group transfected with lent-virus carrying ERK5-shRNA,and the cell model was constructed with MCF-7/ADM cells of the negative control group.After comparison,it was confirmed that silencing ERK5 can enhance the drug sensitivity of MCF-7/ADM to adriamycin,inhibit its proliferation and promote its apoptosis.Objective:In this study,ERK5 silenced breast cancer adriamycin-resistant cells MCF-7/ADM and negative control MCF-7/ADM cell models were constructed to observe the effects of silenced ERK5 on the biological functions of MCF-7/ADM cells and to explore the mechanism of action.To seek a new therapeutic direction for the clinical treatment of drug-resistant breast cancer.Methods:1.The expression levels of ERK5 mRNA in MCF-7/ADM,MCF-7 and HS578BST breast cancer cells were detected by qRT-PCR.2.MCF-7/ADM cells were transfected with lentiviral vectors carrying ERK5-shRNA and negative control shRNA respectively,and the lentiviral infection rate of the two groups of cells was observed by fluorescence inverted microscope,and the expression level of ERK5 mRNA in the transfected cells of the two groups was detected by qRT-PCR.ERK5 silencing efficiency of ERK5-shRNA transfected cells was calculated.Subsequent cell models were constructed.3.After culture,the experimental cells were divided into two groups:shERK5 group and shCtrl group.The culture was continued by changing the medium containing different concentrations of adriamycin,and the sensitivity of the cells in the two groups to adriamycin was detected by CCK-8 method,and the inhibition rate of the cells at each drug concentration was calculated.4.The experimental cells were divided into four groups:The shERK5+ adriamycin intervention group(15ug/ml),the shCtrl+adriamycin intervention group(15ug/ml),the shERK5+adriamycin free group and the shCtrl+adriamycin free group were divided into groups.After routine culture,the cells were fixed,stained,air-dried,photographed,and the proliferation ability of cells in each group was detected by clone counting.5.The experimental cells were divided into four groups:The shERK5+ adriamycin intervention group(15ug/ml),shCtrl+adriamycin intervention group(15ug/ml),shCtrl+adriamycin free group(15ug/ml),shCtrl+adriamycin free group(15ug/ml)were divided into groups.After culture,the cells were washed and centrifugalized,and the apoptosis and cycle distribution of MCF-7/ADM cells were detected by flow cytometry.6.SPSS22.0 software was used for statistical analysis,and P<0.05 was considered statistically significant difference between the data.Results:Compared with non-drug-resistant breast cancer cell line MCF-7 and normal breast cancer cell line HS578BST,ERK5 was highly expressed in breast cancer adriamycin resistant cell line MCF-7/ADM(P<0.05).Silencing ERK5 could effectively inhibit the proliferation and promote the apoptosis of MCF-7/ADM cells under the effect of adriamycin(P<0.05).At the same time,silencing ERK5 can also enhance the sensitivity of MCF-7/ADM cells to adriamycin,and to a certain extent,block the cells in G0/G1 phase,and inhibit the growth of cancer cells.Conclusions:This study confirmed that the expression level of ERK5 in MCF-7/ADM was significantly higher than that of MCF-7 and HS578BST,suggesting that ERK5 may be involved in the regulation of drug resistance in breast cancer cells.At the same time,by silencing the expression of ERK5 in MCF-7/ADM,the growth and proliferation of MCF-7/ADM can be effectively inhibited,and the sensitivity of MCF-7/ADM can be improved.This suggested that silencing ERK5 could reverse the drug resistance of breast cancer resistant cells.Therefore,targeted therapy for ERK5 may be a new direction in the treatment of drug-resistant breast cancer.