A Novel Mechanism For A Resveratrol Oligomer Diptoindonesin G To Enhance Sensitivity To Tamoxifen Thearapy By Promoting Luminal Differentiation In Tnbc Cells

Triple-negative breast cancer(TNBC),defined by a lack of expression of estrogen receptor(ER)and progesterone receptor(PR)as well as human epidermal growth factor receptor 2(HER2),accounts for 12-17% of breast cancer in Asia.TNBC has a high rate of local recurrence and systemic metastasis that are unresponsive to current therapies.The lack of targeted therapies and the poor disease prognosis have fostered a major effort to discover potential molecular targets to treat patients with TNBC.Resveratrol is a natural plant polyphenol antitoxin with a variety of biological activities.In recent years,several studies have reported that resveratrol has anti-oxidant,anti-aging,antitumor,immune regulation,and neuroprotective effects.Previous research found that Diptoindonesin G,a 1.5-fold resveratrol small molecule compound,can be used as a selective estrogen receptor modulator to treat human breast cancer.Recent study has also found that Dip G can inhibit acute myeloid leukemia(AML)by inducing leukemia differentiation.The purpose of this study is to evaluate the activity of Dip G in TNBC,to explore new mechanisms for inhibiting TNBC and to provide new ideas for the treatment of TNBC in clinical.In the first chapter,we reviewed several main research objects involved in this thesis systematically and summarized the current research status.Research topics include the research status of resveratrol/resveratrol oligomers/Dip G,triple-negative breast cancer and its treatment,and the role of the GABARAPL1.In chapter two,firstly,we found that Dip G inhibited cell proliferation of the TNBC cell lines including MDA-MB-231,MDA-MB-468 and SUM1315 by using the trypan blue dye exclusion,soft agar colony formation,and bromodeoxyuridine assays.The inhibition of TNBC cell proliferation by Dip G was not related to apoptosis,necrosis and autophagy.Next,through experiments such as flow cytometry,western blot,q PCR,and oil red staining,we found that Dip G promoted the luminal-like morphology and function in TNBC cells.It also reduced the expression of stemness-related genes in TNBC cells.These results suggest that Dip G exerts its inhibitory effects on TNBC proliferation through inducing TNBC luminal differationtion.Finally,we performed gene expression profile analysis and found that Dip G induces a partial transcriptome shift from basal to luminal gene expression signatures.In Chapter 3,by comparison analysis between gene profile data in Dip G-treated AML cells and TNBC cells,we found that among the common differentially regulated genes,the most significantly regulated gene was found to be GABARAPL1.Dip G significantly increased the gene and protein levels of GABARAPL1 in TNBC cells.Dip G-induced inhibition of TNBC cell proliferation was weakened after knocking down GABARAPL1.Due to the linkage of Dip G,GABARAPL1 and Estrogen receptor(ER),we examined the changes of ER in TNBC cells after treatment with Dip G,and found that Dip G reduced the expression of ESR1 while increasing the expression of ESR2.After knocking down ESR2,the differentiation-promoting effects of Dip G were weakened,indicating that Dip G promotes cell differentiation by inducing the expression of ESR2 in TNBC cells,which activates the transcription and expression of GABARAPL1.In Chapter 4,we established a mouse model of TNBC xenograft tumors,and set different treatment groups of Dip G,chemotherapeutic drugs PTX and tamoxifen.It was found that Dip G inhibited the growth of TNBC tumors,promoted tumor cell differentiation,and inhibited lung metastasis of tumors in vivo.The combination of Dip G and tamoxifen has a stronger effect,which has a good indication for the treatment direction of triple-negative breast cancer.In summary,in this study,we found that Dip G can inhibit the proliferation and invasion of triple-negative breast cancer in vitro and in vivo.Mechanistically,Dip G can promote the differentiation of TNBC cells by inducing the expression of GABARAPL1 in a ERβ-dependent manner.Inhibiting the proliferation and migration ability of TNBC cells has a good antitumor effect in vivo and in vitro.This has great guiding significance for the application of Dip G and the treatment of TNBC.To our knowledge,Dip G is the first natural product that triggers the phenotype switch in basal-like breast cancer.Our findings also reveal a previously unappreciated role for GABARAPL1 as a determinant of the molecular subtype of breast cancer.This work shed light on new therapeutic opportunities for basal-like breast cancer via a phenotype switch and indicate that Dip G may serve as a leading compound for the therapy of basal-like breast cancer.