Role of platelets and breast cancer stem cells in metastasis

The high mortality rate of breast cancer is mainly caused by the metastatic ability of cancer cells,resistance to chemotherapy and radiotherapy,and tumor regression capacity.In recent years,it has been shown that the presence of breast cancer stem cells is closely associated with the migration and metastatic ability of cancer cells,as well as with their resistance to chemotherapy and radiotherapy.The tumor microenvironment is one of the main molecular factors involved in cancer and metastatic processes development,in this sense it is interesting to study the role of platelets,one of the main communicator cells in the human body which are activated by the signals they receive from the microenvironment and can generate more than one response.Platelets can ingest and release RNA,proteins,cytokines and growth factors.After the platelets interact with the tumor microenvironment,they are called"tumor-educated platelets."Tumor-educated platelets transport material from the tumor microenvironment to sites adjacent to the tumor,thus helping to create microenvironments conducive for the development of primary and metastatic tumors.It has been observed that the clone capable of carrying out the metastatic process is a cancer cell with stem cell characteristics.Cancer stem cells go through a series of processes,including epithelial-mesenchymal transition,intravasation into blood vessels,movement through blood vessels,extravasation at the site of the establishment of a metastatic focus,and site colonization.Tumor-educated platelets support all these processes.

Let-7 miRNA and CDK4 siRNA co-encapsulated in Herceptin-conjugated liposome for breast cancer stem cells

Recently,breast cancer stem cells(BCSCs)have rapidly emerged as a novel target for the therapy of breast cancer as they play critical roles in tumor growth,maintenance,metastasis,and recurrence.Let-7 miRNA is known to be downregulated in a variety of cancers,especially BCSCs,whereas CDK4 being overexpressed in human epidermal growth factor receptor 2(HER-2)overexpressing tumor cells.In this study,let-7 miRNA and CDK4-specific siRNA were chosen as therapeutic agents and co-encapsulated in Herceptinconjugated cationic liposomes for breast cancer therapy.Particle size,zeta potential,and encapsulation efficacy of mi/siRNA-loaded PEGylated liposome conjugated with Herceptin(Her-PEG-Lipo-mi/siRNA)were 176 nm,28.1 mV,and 99.7%±0.1%,respectively.Enhanced cellular uptake(86%)was observed by fluorescence microscopy when SK-BR-3 cells were treated with Her-PEG-Lipo-mi/siRNA.Also,the increased amount of let-7a mRNA and decreased amount of cellular CDK4 mRNA were observed by qRT-PCR when SK-BR-3 cells were treated with Her-PEG-Lipo-mi/siRNA,which was even more so when SK-BR-3 stem cells were used(197 vs 768 times increase for let-7a,62%vs 68%decrease for CDK4).Growth inhibition(65%)andmigration arrest(0.5%)of the cellswere achieved by the treatment of the cells with Her-PEG-Lipo-mi/siRNA,but not withmi/siRNA complex or other formulations.In conclusion,an efficient liposomal delivery system for the combination of miRNA and siRNA to target the BCSCs was developed and could be used as an efficacious therapeuticmodality for breast cancer.

Epithelial-Mesenchymal Transition and Breast Cancer Stem Cells in Breast Cancer Progression

Breast cancer stem cells (BCSCs) are a small subpopulation of cancer cells having the ability of self-renewing and multi-lineage differentiation, which have also been termed as “tumor-initiating cells”. And in recent years, the role of epithelial mesenchymal transition (EMT) in malignant tumors has been valued. This paper will briefly review and discuss the relationship between BCSCs and EMT.

PGK1-coupled HSP90 stabilizes GSK3βexpression to regulate the stemness of breast cancer stem cells

Objective:Glycogen synthase kinase-3β(GSK3β)has been recognized as a suppressor of Wnt/β-catenin signaling,which is critical for the stemness maintenance of breast cancer stem cells.However,the regulatory mechanisms of GSK3βprotein expression remain elusive.Methods:Co-immunoprecipitation and mass spectral assays were performed to identify molecules binding to GSK3β,and to characterize the interactions of GSK3β,heat shock protein 90(Hsp90),and co-chaperones.The role of PGK1 in Hsp90 chaperoning GSK3βwas evaluated by constructing 293T cells stably expressing different domains/mutants of Hsp90α,and by performing a series of binding assays with bacterially purified proteins and clinical specimens.The influences of Hsp90 inhibitors on breast cancer stem cell stemness were investigated by Western blot and mammosphere formation assays.Results:We showed that GSK3βwas a client protein of Hsp90.Hsp90,which did not directly bind to GSK3β,interacted with phosphoglycerate kinase 1 via its C-terminal domain,thereby facilitating the binding of GSK3βto Hsp90.GSK3β-bound PGK1 interacted with Hsp90 in the“closed”conformation and stabilized GSK3βexpression in an Hsp90 activity-dependent manner.The Hsp90 inhibitor,17-AAG,rather than HDN-1,disrupted the interaction between Hsp90 and PGK1,and reduced GSK3βexpression,resulting in significantly reduced inhibition ofβ-catenin expression,to maintain the stemness of breast cancer stem cells.Conclusions:Our findings identified a novel regulatory mechanism of GSK3βexpression involving metabolic enzyme PGK1-coupled Hsp90,and highlighted the potential for more effective cancer treatment by selecting Hsp90 inhibitors that do not affect PGK1-regulated GSK3βexpression.

The p38/MAPK pathway as a therapeutic target to prevent therapeutic escape of breast cancer stem cells

Cancer stem cells(CSCs)play an important role in metastasis development,tumor recurrence,and treatment resistance,and are essential for the eradication of cancer.Currently,therapies fail to eradicate CSCs due to their therapeutic stress-induced cellular escape,which leads to enhanced aggressive behaviors compared with CSCs that have never been treated.However,the underlying mechanisms regulating the therapeutic escape remain unknown.To this end,we established a model to isolate the therapeutic escaped CSCs(TSCSCs)from breast CSCs and performed the transcription profile to reveal the mechanism.Mechanistically,we demonstrated that the behavior of therapeutic escape was regulated through the p38/MAPK signaling pathway,resulting in TSCSCs exhibiting enhanced motility and metastasis.Notably,blocking the p38/MAPK signaling pathway effectively reduced motility and metastasis ability both in vitro and in vivo,which were further supported by downregulated motility-related genes and epithelial-mesenchymal transition(EMT)-related proteins vimentin and N-cadherin.The obtained findings reveal the p38/MAPK pathway as a potential therapeutic target for TSCSCs and would provide profound implications for cancer therapy.

UBE2T mediates the stemness properties of breast cancer cells through the mTOR signaling pathway

Objectives:This study aimed to reveal the role and possible mechanism of the ubiquitin-conjugating enzyme 2T(UBE2T)in the biological activities of breast cancer stem cells(BCSCs).Methods:The specific protein and gene expression were quantified by Western blotting and quantitative real-time polymerase chain reaction,the proportion of BCSCs was examined by flow cytometry,and the self-renewal and proliferation of BCSCs were verified by serial sphere formation and soft agar.Results:Increasing expression of UBE2T was drastically found in breast cancer than that in adjacent tissues.Furthermore,UBE2T overexpression significantly increased the proportion of BCSCs in breast cancer cells and promoted their self-renewal and proliferation.Silent UBE2T exhibited the opposite functions.UBE2T increased the levels of the mammalian target of rapamycin and the phosphorylated mammalian target of rapamycin.Mammalian target of rapamycin(mTOR)inhibitor rapamycin inhibited the function of UBE2T in BCSCs.Conclusion:UBE2T plays a role in BCSCs through mTOR pathway and may suggest a novel therapeutic strategy for breast cancer.

Research Progress of Breast Cancer Stem Cell Stemness and Breast Cancer Recurrence

Currently, breast cancer is the most common malignant tumour in Chinese women with a high incidence rate, and recurrence and metastasis are the main reasons affecting survival. Breast Cancer Stem Cells (BCSCs) are stem cells capable of continuous regeneration in vivo with strong self-renewal ability and multidirectional differentiation potential, which are highly tumourigenic and insensitive to radiotherapy and chemotherapy, and are highly susceptible to breast cancer recurrence. Therefore, exploring the stemness of BCSCs and their mechanism associated with recurrence is important for developing new therapeutic strategies, improving therapeutic efficacy, and improving patient prognosis.

The roles of ncRNAs and histone-modifiers in regulating breast cancer stem cells

Cancer stem cells （CSCs）, a subpopulation of cancer cells with ability of initiating tumorigenesis, exist in many kinds of tumors including breast cancer. Cancer stem cells contribute to treatment resistance and relapse. Conventional treatments only kill differentiated cancer cells, but spare CSCs. Combining conventional treatments with therapeutic drugs targeting to CSCs will eradicate cancer cells more efficiently. Studying the molecular mechanisms of CSCs regulation is essential for developing new therapeutic strategies. Growing evidences showed CSCs are regulated by non-coding RNA （ncRNA） including microRNAs and long non-coding RNAs （IncRNAs）, and histone-modifiers, such as let- 7, miR-93, miR-100, HOTAIR, Bmi-1 and EZH2. Herein we review the roles of microRNAs, IncRNAs and histone- modifiers especially Polycomb family proteins in regulating breast cancer stem cells （BCSCs）.

Downregulation of miRNA-21 and cancer stem cells after chemotherapy results in better outcome in breast cancer patients

Epigenetic modifications have been observed as a decline in miRNA-21 expression and breast cancer stem cell(CSC)population after 3 cycles of standard chemotherapy.The epigenetic response(miRNAs expression)and CSCs are also correlated in patients with Breast Cancer.In patients who tolerated chemotherapy well,miRNA-21(non-coding RNA)expression decreased significantly after three cycles of chemotherapy.The miRNA-21 expression in breast cancer tissue was quantified by quantitative PCR(real-time PCR)using the standard protocol.In addition,breast CSCs(CD44+/CD24-)were also decreased in these patients.The miRNA-21 regulates cell division,proliferation,and autophagy of cancerous cells(as it targets phosphatase and tensin homolog/AKT/transcription factor EB/programmed cell death 4/autophagy-related protein 5 and chemotherapy also produces similar effects),thereby contributing to these benefits.Therefore,when all of the targets on genes have been explored by mimic miRNA,chemotherapy combined with anti-miRNA21 therapy may prove useful in the care of cancer patients.

MicroRNAs in breast cancer and breast cancer stem cells and their potential for breast cancer therapy

The discovery of the first miRNA, lin-4, in Caenorhabditis elegans initiated a new era of miRNA biology. Sincethen, thousands of miRNAs annotated, many of which have have been identified and been shown to play roles in a variety of biological processes, including development, differentiation, apoptosis, proliferation, and cell death） Furthermore, growing evidence indicates that miRNA deregulation is a critical cause of cancer formation. The biogenesis, function, and potential application of miRNAs have become active areas of research. With the development of molecular biological technologies, such as northern blotting with radio-labeled probes, cloning, quantitative PCR, serial analysis of gene expression （SAGE）-based techniques, bead-based profiling methods, and oligonucleotide microarrays,2 it is possible to conduct miRNA research precisely and comprehensively. BIOGENESIS OF MICRORNAS MicroRNAs are derived from introns or exons of protein- coding and non-coding genes,3＇4 and are either transcribed by polymerase II as a long primary transcript （primary miRNA） or originate from the introns of mRNAs. Primary miRNAs are further processed by the Drosha microprocessor complex, which recognizes stem-looped secondary structures within primary miRNAs, resulting in the excision and release of-70 nucleotide hairpin precursors termed pre-miRNAs （precursor microRNAs）.5 The mirtron subclass of miRNAs, which are encoded in the introns of genes, generate pre-miRNAs directly from byproducts of intron splicing and disbranching events in the nucleus with the assistance of a ＂debranching enzyme＂.6 After being exported from the nucleus by exportin-5, the pre-miRNAs are subsequently cleaved by Dicer to release a 22-nucleaotide miRNA-miRNA duplex. One strand of this duplex is incorporated into the RNA-induced silencing complex （miRISC）, and eventually serves as a mature microRNA, while the other strand is degraded. The ＂seed＂ region of the mature microRNA （nucleotides 2-8 at the 5＇ end） can bind partially or completely to the 3＇UTR of specific protein-coding gene mRNAs.7＇8 MicroRNAs regulate their targets by directly cleaving mRNAs or inhibiting protein synthesis, depending on the degree of complementarity with the 3＇UTRs of their targets.4

Anticancer effect of curcumin on breast cancer and stem cells

Numerous studies have shown that curcumin,a natural compound,exerts anticancer effects by inhibiting cancer cell proliferation and metastasis and by inducing cell cycle arrest and apoptosis.In particular,curcumin exhibits potent inhibitory effects on breast cancer,the most prevalent type of cancer among women worldwide.It has low maximal inhibitory concentration for breast cancer cell lines that express the hormone receptor ER and sensitizes cell lines to anticancer drugs.Moreover,it can induce apoptosis in cell lines independently of hormone receptor expression.In addition,curcumin inhibits the proliferation of breast cancer stem cells(BCSC),an important factor that influences cancer recurrence.The inhibition of BCSC proliferation suppresses metastasis and reattachment,ultimately limiting tumor formation.A xenograft study similarly showed that curcumin exerts tumor-suppression effects on cancer cells and cancer stem cells.Therefore,curcumin is a potential anticancer compound,and its concurrent application with other anticancer drugs appears promising.

Stem cell therapy: A paradigm shift in breast cancer treatment

As per the latest Globocan statistics,the high prevalence rate of breast cancer in low-and middle-income countries has led to it becoming the most common cancer to be diagnosed,hence posing a major public health challenge.As per this data,more than 11.7%of the estimated new cancer cases in 2020 were due to breast cancer.A small but significant subpopulation of cells with self-renewing ability are present in the tumor stroma and have been given the nomenclature of cancer stem cells(CSCs).These cells display a high degree of plasticity owing to their ability to transition from the slowly cycling quiescent phase to the actively proliferating phenotype.This attribute of CSCs allows them to differentiate into various cell types having diverse functions.Breast CSCs have a pivotal role in development,metastasis,treatment resistance and relapse of breast cancers.This review focuses on the pathways regulating breast CSC maintenance and the current strategies that are being explored for directing the development of novel,targeted,therapeutic approaches for limiting and eradicating this aberrant stem cell population.

Angiotensin-(1-7)and Human Chorionic Gonadotropin(hCG)Modulate the Nuclear Transcription Factors or Nuclear Receptors Genes in the Tumorigenic Undifferentiated Breast Cancer Cell Line SKBR3

Breast cancer is the most common cancer among women. Angiotensin-(1 - 7) [Ang-(1 - 7)] has been correlated with cancer antiproliferative and apoptotic effects, similar properties of the human Chorionic Gonadotrofin (hCG). The aims of this work are to evaluate the role of Ang-(1 - 7) and of hCG in modulating the expression of Nuclear Receptors and Coregulators related genes in the tumorigenic breast cell line SK-BR3. Three experimental groups were created: control, hCG and hCG + Ang-(1 - 7). Cells were treated for 11 days and then had their RNA extracted. Samples were loaded into PCR Array plates containing 84 genes relate to Nuclear Receptors and Coregulators pathways. Gene expression data were used to construct canonical pathways (MetacoreTM). hCG and hCG + Ang-(1 - 7) treatments markedly modulate the expression of Nuclear Receptors and Coregulators related genes. hCG differentially expressed 17% of the genes, being 29% upregulated and 71% downregulated. Meanwhile, hCG + Ang-(1 - 7) changed the expression of 30% of the genes on the plate, among these genes 56% were upregulated and 44% downregulated. Among these differentially expressed genes, we highlight Esr1, Nr2f2, and Nr2f1, Esr1, Hdac5, and Nr4A1 (>4 fold). Finally MetaCore analysis based on Gene Ontology (GO) generated six networks for hCG and ten networks for the combined treatment. All generated networks are related to regulation of apoptosis or to Programmed Cell Death processes. In summary, our results herein demonstrate that the modulation of sexual hormones and of other nuclear factor genes expression might underlie the tumorigenic protection effect and the induction of cell differentiation caused by the hormones hCG and Ang-(1 - 7), especially in Cancer Stem Cells.