Investigation Of Novel Nuclear Export Inhibitor And The Mechanism For Its Therapeutic Effects On Breast Cancer

Breast cancer is one of the most common cancers worldwide with the highest incidenceof malignancy in women.Although the clinical treatment of breast cancer has been rapidly developed in recent years,the prognosis is still rather poor with easy relapse and metastasis.Hence,the mortality rate is still high so far,especially for triple-negative breast cancer.It has been found that CRM1 which is overexpressed in cancer cells is closely related to the malignant proliferation,anti-apoptosis and drug resistance of cancer cells.Therefore,CRM1 is considered as a potential anti-tumor target.However,the existing CRM1 inhibitors failed to meet the requirements.Therefore,it is rather necessary to develop new types of reversible CRM1 inhibitors for cancer therapy.In this study,we first found a new type of CRM1 inhibitor based on the result of computer virtual screening.Then,we used breast cancer cell lines as experimental subjects to explore the inhibitory effects of the new CRM1 inhibitor on these cell lines as well as its mechanisms.Finally,the in vivo anti-breast cancer effects and the safety profile for the host of the new CRM1 inhibitor were evaluated by animal experiments.The main conclusions are shown as follows:(1)A series of electrophilic pharmacophores were designed based on the mechanism of intereactions between LMB and CRM1.We found the small targeted molecule LFS-01,a natural product,is a new CRM1 inhibitor based on Pubchem database and FIPSDock through computer virtual screening.At the same time,we demonstrated that LFS-01 was targeted to CRM1 by covalently binding to the active amino acid Cys528 of the CRM1 hydrophobic cleft.(2)LFS-01 effectively inhibited the activity of MDA-MB-231,MCF-7 and BT-474 breast cancer cell lines.The half maximal inhibitory concentration(IC50)was 11.72?M,20.29?M and 15.76?M respectively at 72 h.In addition,the primary breast cancer cells were more sensitive to LFS-01 than to clinical chemotherapy drugs in vitro,such as epirubicin,docetaxel,carboplatin and capecitabine.(3)Nrf2,which was accumulated in the MDA-MB-231 cell nucleus through the inhibition of CRM1-mediated nuclear transport by LFS-01,increased the transcription and expression of p62.The increased expression of p62 in turn promoted the further activation of Nrf2.This circus stimulated autophagy continuously in MDA-MB-231 human breast cancer cell.The severity of autophagy was also shown to be time dependent and drug concentration dependent in the experiments we tested.(4)LFS-01 administered by intragastric administration had a certain in vivo anti-tumor effect in MDA-MB-231 human breast cancer nude mice xenografts,but this effect was not as potent as that of epirubicin hydrochloride administered by tail vein injection.However,LFS-01 is safer for nude mice than epirubicin hydrochloride.This study provides a new strategy for breast cancer safely targeted therapy,especially for triple-negative breast cancer.