The Effect Of Morin On Growth Inhibition And Its Related Mechanism In Breast Cancer

Breast cancer is currently the world’s highest incidence of female malignanttumors. Although a significant progress in previous study on the prevention andtreatment of breast cancer has been made, there are still many important problems to beresolved. And some report on breast cancer therapy pointed out that GSK-3β kinase hasa closed association with autophagy, which can protect tumor cells from anti-tumor drugor induce cell death by induction of autophagic cell death. Besides, proteasome inhibitorhas become the hotspot for its special effect on cancer cells in cancer research.And Morin is a new natural proteasome inhibitor, which is screened and identifiedin this research through computer simulation and experiment of molecular biology.Other research has verified that Morin can not only enhance the sensitivity of cancercells to anti-tumor drugs but also cause greater cytotoxicity to cancer cells by itself, so itwill play an important role in cancer therapy in the future. As a result, this research usedhuman breast cancer cell line MCF-7as the model compared with human mammaryepithelial cells MCF-10A to analysis the effect of growth inhibition of Morin in breastcancer and its related mechanism.Firstly, Morin’s inhibition effect on purified20S proteasome is confirmed viaproteasome activity assay, and then it was also found that Morin has the special effecton the26S proteasome in MCF-7cells. It would reduce the activity of proteasome andinduce the accumulation of ubiquitinated proteins in MCF-7cells while in MCF-10Acells400μmol/L Morin can only inhibit20%activity of the proteasome.Next, it was discovered that Morin (200μmol/L) can block cell cycle in G2/Mstage in MCF-7cells more easily compared with MCF-10A cells, in which G2/M arresthappens only when the cells were treated with higher dose of Morin (400μmol/L).Meanwhile, MTT results and Western Blot Assay both showed that Morin can reduceproliferation and viability in MCF-7cells and induce the cleavage of PARP in MCF-7cells but not in MCF-10A cells with the same treatment. These results mean that Morinhas a greater cytotoxicity on MCF-7cells and may induce apoptosis, but MCF-10A ismore resistant to Morin.This research also found the up-regulation of autophagy related protein LC3-II/Iratio and expression of Beclin-1in MCF-7cells treated with Morin. After inhibition ofautophagy by the autophagy inhibitor bafolimycin-A1, it was detected that the apoptosisratio of MCF-7cells raised about15%and the cleavage of PARP was also increased inMCF-7cells. As a result, it is believed that autophagy induced by Morin can protectMCF-7cells. Besides, the accumulation of β-catanin and p-GSK-3β (Ser9) in MCF-7cells treated with Morin told that Morin could inhibit the activity of GSK-3β kinase inbreast cancer MCF-7cells. As a conclusion, this research gave a preliminary analysis about the influence onthe growth of breast cancer cells and illuminated part molecular mechanism ofinhibition on its growth by Morin. And all of these results validated the anti-cancerspecificity of Morin.