Preliminary Study On The Role C-jun In Inhibition Of Proliferation Of MCF7Human Breast Cancer Cells By Tamoxifen

Objectives:Tamoxifen （TAM）, the non-steroidal anti-estrogen most widely administered tobreast cancer patients, acts, at least in part, by competing blockade of the estrogen receptor（ER）. This study was designed to research the effect of TAM on cell proliferation,expression of c-Jun and AP-1activity in breast cancer cells. To explore the role of c-Jun intamoxifen inhibit breast cancer cell proliferation.Methods:1. Estrogen receptor-positive MCF-7human breast cancer cells and estrogenreceptor-negative MDA-MB-435human breast cancer cells were treated with differentconcentration of TAM，then cell proliferation was analyzed by CCK-8kit，the expressionof c-Jun was detected by RT-PCR and Western Blot. Using Dual-luciferase reporter assaysystem to investigate the potentially role of TAM on signaling pathway including AP1（PMA） andAP1in MCF-7and MDA-MB-435cells.2. Expression vector of sense c-Jun was constructed: The full-length sequence of thec-Jun gene was cloned by PCR method, and inserted into the eukaryotic expression vectorpIRES2-EGFP. The recombinant plasmid expression vectors identified by restrictionenzyme digestion and sequencing. Expression vector pIRES2-c-Jun and silencing plasmidspGPU6/GFP/Neo-shRNA of c-Jun were transected into MCF-7cells, then the cells weretreated with different concentration of TAM, cell proliferation was analyzed by CCK-8kit.Results:1. The effect of TAM on the growth of cells and the expression of c-Jun: CCK-8results showed that, compared with the control group, different concentrations of TAM could inhibit the proliferation of MCF-7cells and MDA-MB-435cells, and the inhibitionrate increased with the dose increased; RT-PCR, Western Blot test results showed thatdifferent concentrations of TAM had no statistically significant effect on expression ofc-Jun; The results of the luciferase reporter gene showed that, AP1（PMA） signalingpathway in MCF-7cells were dose-dependent activated by TAM.2. Construction of recombinant plasmid expression vectors: the c-Jun expressionvector confirmed successfully constructed by restriction enzyme digestion and sequencing.The roles of c-Jun in the implications of TAM inhibited the MCF-7cell proliferation:CCK-8results showed that, high expression of c-Jun could enhance the inhibitory effect ofTAM on MCF-7cell proliferation; low expression of c-Jun reduced the inhibitory effect ofTAM on MCF-7cell proliferation.Conclusions:1. TAM could both inhibit the proliferation of ER-positive breast cancer MCF-7cellsand ER-negative breast cancer cells MDA-MB-435; TAM had no statistically significanteffect on expression of c-Jun, but TAM could activate the PKC pathway and induce AP-1activity in MCF-7cells.2. The c-Jun expression vector was successfully constructed, c-Jun might be involvedin the TAM inhibition of breast cancer MCF-7cells proliferation.In summary, different concentrations of TAM inhibited MCF-7cells andMDA-MB-435cells proliferation and inhibition rates increased with the dose increased,further studies had shown that TAM inhibited the proliferation of MCF-7cells through thePKC pathway activated c-Jun.