| Breast cancer,the most common spontaneous malignancy diagnosed in women,severely threaten women's health.Diet is a major risk factor for breast cancer,but the relationship between dietary free cholesterol,fatty acids and breast cancer remains unclear.Previous studies of association analysis have shown that conjugated cholesterol(cholesterol esters)may be associated with the progression of a variety of cancers,but no studies have shown whether cholesterol esters contribute to the development of breast cancer and other cancers.Therefore,this thesis analyzed the relationship between malignant degree and cholesterol ester content in clinical samples of breast cancer,and used MMTV-PyMT transgenic mice as animal model,animal model can be divided into two groups,in the first group of mice,different concentrations of cholesterol ester was added to the feed,in another group of mice,cholesterol,fatty acid was added to the feed and administrated the cholesteryl ester synthase inhibitor Avasimibe to the transgenic mice to explore the role of cholesteryl ester in the proliferation and invasion of mammary gland tumors and the underlying mechanisms.The following results:(1)The content of cholesteryl ester in mammary gland tumor was positively correlated with the degree of mammary gland tumor progression.This thesis used correlation analysis to explore the relationship between malignant degree of tumor(Ki67)and intratumor cholesteryl ester content in clinical samples of mammary gland tumor.This thesis found that the correlation between cholesteryl ester content and malignant degree of tumor were positive in three subtypes(Luminal A?Luminal B and Her2+).This thesis used GC/MS to detect the difference of cholesterol ester level between the mammary gland tissue of 12-week-old wild-type(WT)mice and the mammary gland tumor tissue of the same week-old MMTV-PyMT mice.This thesis found that the cholesteryl ester levels in tumor was significantly higher than mammary gland.(2)Increasing the content of cholesteryl ester in the diet of mice can accelerate the progression of mammary gland tumor and promoted mammary gland tumor metastasis This thesis fed MMTV-PyMT mice with different concentrations of cholesteryl ester to observe the effect of cholesteryl ester on the occurrence and development of mammary gland tumors by recording tumor development time,tumor quality,and use of H&E staining to observe the condition of lung metastases.This thesis found that cholesteryl ester showed dose-dependent reduced breast tumor latency,improved tumor weight,increased the Ki67 immunohistochemical positive cells,and increased both the number of metastatic lesions and lung metastasis rate.(3)Dietary cholesteryl esters had some effect on glucose and lipid metabolism of mice.This thesis used comprehensive monitoring system and lipidomics to explore the effect of cholesteryl ester on glucose and lipid metabolism in transgenic mice,This thesis found that cholesteryl ester can reduce fasting blood glucose and glucose oxidation rate of mice,reduce the content of TG,StE,CerG1,GM3,SiE and HDL-C,and increase the content of MGDG,and phospholipid such as PC,PG,PI,PA,PEt,PMe.(4)Cholesteryl ester synthase inhibitor(Avasimibe)can inhibit the effect of cholesteryl esters on the proliferation of mammary gland tumors.This thesis fed MMTV-PyMT mice with 0.02 g cholesterol/g feed and 30%high fat feed,and administrated the cholesteryl ester synthase inhibitor Avasimibe to the MMTV-PyMT mice to observe the effect of endogenous cholesteryl ester synthesis on mammary gland tumor proliferation,in addition,this thesis also used GC-MS to detect the effects of different dietary interventions and administrated the cholesteryl ester synthase inhibitor on the cholesteryl ester content in the MMTV-PyMT mice.This thesis found that the combination of cholesterol and fat can improve the content of cholesteryl ester in mammary gland tumor,tumor quality and Ki67 index,while cholesterol and fat alone cannot have the same effect.In addition,administrated Avasimibe,a cholesteryl ester synthase inhibitor,can reduced the content of cholesteryl ester in mammary gland tumor,tumor quality and Ki67 index,compared with the combined effect of cholesterol and fat.The above results showed that increasing the cholesteryl ester content in mice could accelerate the progression of mammary gland tumors,and Avasimibe could reduce the cholesteryl ester content and slow the progression of mammary gland tumors.(5)Cholesteryl esters can accelerate mammary gland tumor proliferation by activating the Akt/mTOR/p70s6k pathway,inhibition of cholesteryl ester synthesis can inhibit the Akt/mTOR/p70s6k pathway and thus inhibit the proliferation of breast tumor cells.Flow cytometry was used to analyze the progress of the cell cycle,and the protein phosphorylation level of Akt/mTOR/p70s6k signaling pathway was detected by Western blot.It was found that Avasimibe could significantly induce an accumulation of cells in the G0/G1 phase,and inhibit MCF-7 cell proliferation;cholesteryl esters can improve mTOR,Akt,P-70s6k protein phosphorylation level;Avasimibe can reduce mTOR,Akt,P-70s6k protein phosphorylation level.(6)Cholesteryl esters can promote lung metastasis of mammary gland tumor by increasing the expression of tumor invasion-related proteins Western blot was used to detect the expression of vimentin in MMTV-PyMTV mice of the 12-week-old normal diet group and the mice of the same week-old cholesteryl esters group.The results showed that cholesteryl ester diet could promote lung metastasis of mammary gland tumor by increasing vimentin expression in mice.In summary,the results of our experiment indicate that cholesteryl esters can promote mammary gland tumor proliferation and the process by activating the Akt/mTOR/p70s6k pathway,while Avasimive can inhibit cell proliferation by inhibiting the Akt/mTOR/p70s6k signaling pathway.Cholesteryl esters can also promoted mammary gland tumor metastasized to the lung by increasing the expression of vimentin.The above results provide a reference for future dietary guidelines and provide some theoretical basis for the treatment of breast cancer. |
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