Reversal of tamoxifen resistance by artemisinin in ER+breast cancer:bioinformatics analysis and experimental validation

Breast cancer is the leading cause of cancer-related deaths in women worldwide,with Hormone Receptor(HR)+being the predominant subtype.Tamoxifen(TAM)serves as the primary treatment for HR+breast cancer.However,drug resistance often leads to recurrence,underscoring the need to develop new therapies to enhance patient quality of life and reduce recurrence rates.Artemisinin(ART)has demonstrated efficacy in inhibiting the growth of drug-resistant cells,positioning art as a viable option for counteracting endocrine resistance.This study explored the interaction between artemisinin and tamoxifen through a combined approach of bioinformatics analysis and experimental validation.Five characterized genes(ar,cdkn1a,erbb2,esr1,hsp90aa1)and seven drug-disease crossover genes(cyp2e1,rorc,mapk10,glp1r,egfr,pgr,mgll)were identified using WGCNA crossover analysis.Subsequent functional enrichment analyses were conducted.Our findings confirm a significant correlation between key cluster gene expression and immune cell infiltration in tamoxifen-resistant and-sensitized patients.scRNA-seq analysis revealed high expression of key cluster genes in epithelial cells,suggesting artemisinin’s specific impact on tumor cells in estrogen receptor(ER)-positive BC tissues.Molecular target docking and in vitro experiments with artemisinin on LCC9 cells demonstrated a reversal effect in reducing migratory and drug resistance of drug-resistant cells by modulating relevant drug resistance genes.These results indicate that artemisinin could potentially reverse tamoxifen resistance in ER-positive breast cancer.

α-Pyrone Derivatives from a Streptomyces Strain Resensitize Tamoxifen Resistance in Breast Cancer Cells

Tamoxifen resistance(TamR)is the underlying cause of treatment failure in many breast cancer patients receiving tamoxifen.In order to look for noncytotoxic natural products with the ability to reverse TamR,an extract from strain Streptomyces sp.KIB-H0495 was detected to be active.Subsequent large scale fermentation and isolation led to the isolation of four a-pyrone derivatives including two new compounds,violapyrones J(2)and K(3),and two known analogues,violapyrones B(1)and I(4).Further bioactivity assays indicated that only 1 and 3 exerted potent resensitization effects on MCF-7/TamR cells at a concentration of 1 lM.Owing to the simple structures of 1 and 3,these two compounds might have potential for further investigation as novel tamoxifen resensitization agent in breast cancer chemotherapy.

STAT3 mediates resistance of CD44^+CD24^(-/low) breast cancer stem cells to tamoxifen in vitro

We sought to determine whether STAT3 mediated tamoxifen resistance of breast cancer stem cells in vitro.The capacities for mammosphere formation and STAT3 expression of CD44＋CD24-/low MCF-7 and MCF-7 were observed.The CD44＋CD24-/low subpopulation ratio and its sensitivity to adriamycin were analyzed in MCF-7 and TAM resistant（TAM-R） cells.Cell cycle,apoptosis,STAT3 and phospho-STAT3 changes were observed af-ter treatment with tamoxifen.Small interference RNA-mediated knockdown of STAT3 in TAM-R cells was also performed.CD44＋CD24-/low MCF-7 showed higher capacities for mammosphere formation and STAT3 expression than total MCF-7.The CD44＋CD24-/low subpopulation was also upregulated in TAM-R cells with less sensitivity to adriamycin than MCF-7.Cell cycle changes,anti-apoptotic effects and STAT3 changes were also found.Mean-while,the knock-down of STAT3 in TAM-R resulted in an increase in sensitivity to tamoxifen.It is concluded that STAT3 plays an essential role in breast cancer stem cells,which correlated with tamoxifen resistance.

Tamoxifen-resistant breast cancer cells possess cancer stem-like cell properties

Background Cancer stem cells （CSCs） are the cause of cancer recurrence because they are resistant to conventional therapy and contribute to cancer growth and metastasis.Endocrinotherapy is the most common breast cancer therapy and acquired tamoxifen （TAM） resistance is the main reason for endocrinotherapy failure during such therapy.Although acquired resistance to endocrine treatment has been extensively studied,the underlying mechanisms are unclear.We hypothesized that breast CSCs played an important role in TAM-induced resistance during breast cancer therapy.Therefore,we investigated the biological characteristics of TAM-resistant （TAM-R） breast cancer cells.Methods Mammosphere formation and tumorigenicity of wild-type （WT） and TAM-R MCF7 cells were tested by a mammosphere assay and mouse tumor xenografts respectively.Stem-cell markers （SOX-2,OCT-4,and CD133） and epithelial-mesenchymal transition （EMT） markers were tested by quantitative real-time （qRT）-PCR.Morphological observation was performed to characterize EMT.Results After induction of TAM resistance,TAM-R MCF7 cells exhibited increased proliferation in the presence of TAM compared to that of WT MCF7 cells （P ＜0.05）,indicating enhanced TAM resistance of TAM-R MCF7 cells compared to that of WT MCF7 cells.TAM-R MCF7 cells showed enhanced mammosphere formation and tumorigenicity in nude mice compared to that of WT MCF7 cells （P ＜0.01）,demonstrating the elevated CSC properties of TAM-R MCF7 cells.Consistently,qRT-PCR revealed that TAM-R MCF7 cells expressed increased mRNA levels of stem cell markers including SOX-2,OCT-4,and CD133,compared to those of WT MCF7 cells （P ＜0.05）.Morphologically,TAM-R MCF7 cells showed a fibroblastic phenotype,but WT MCF7 cells were epithelial-like.After induction of TAM resistance,qRT-PCR indicated that MCF7 cells expressed increased mRNA levels of Snail,vimentin,and N-cadherin and decreased levels of E-cadherin,which are considered as EMT characteristics （P ＜0.05）.Conclusion TAM-R MCF7 cells possess CSC characteristics and may be responsible for TAM resistance during breast cancer therapy.

TGF-β stimulation of EMT programs elicits non-genomic ER-α activity and anti-estrogen resistance in breast cancer cells

Aim:Estrogen receptor-α(ER-α)activation drives the progression of luminal breast cancers.Signaling by transforming growth factor-β(TGF-β)typically opposes the actions of ER-α;it also induces epithelial-mesenchymal transition(EMT)programs that promote breast cancer dissemination,stemness and chemoresistance.The impact of EMT programs on nongenomic ER-αsignaling remains unknown and was studied herein.Methods:MCF-7 and BT474 cells were stimulated with TGF-βto induce EMT programs,at which point ER-αexpression,localization,and nongenomic interactions with receptor tyrosine kinases and MAP kinases(MAPKs)were determined.Cell sensitivity to anti-estrogens both before and after traversing the EMT program was also investigated.Results:TGF-β-stimulated MCF-7 and BT474 cells to acquire EMT phenotypes,which enhanced cytoplasmic accumulation of ER-αwithout altering its expression.Post-EMT cells exhibited:(1)elevated expression of EGFR and IGF1R,which together with Src formed cytoplasmic complexes with ER-α;(2)enhanced coupling of EGF,IGF-1 and estrogen to the activation of MAPKs;and(3)reduced sensitivity to tamoxifen,an event reversed by administration of small molecule inhibitors against the receptors for TGF-β,EGF,and IGF-1,as well as those against MAPKs.Conclusion:EMT stimulated by TGF-βpromotes anti-estrogen resistance by activating EGFR-,IGF1R-,and MAPK-dependent nongenomic ER-αsignaling.