The Role of Breast Cancer Stem Cells as a Prognostic Marker and a Target to Improve the Efficacy of Breast Cancer Therapy

Harnessing the synergistic potential of NK1R antagonists and selective COX-2 inhibitors for simultaneous targeting of TNBC cells and cancer stem cells

Triple-negative breast cancer (TNBC) lacks the expression of oestrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2), rendering it unresponsive to endocrine therapy and HER2 targeted treatments. Though certain chemotherapeutics targeting the cell cycle have shown efficacy to a certain extent, the presence of chemotherapy-resistant cancer stem cells (CSCs) presents a significant challenge in tackling TNBC. Multiple lines of evidence suggest the upregulation of neuropeptide Substance P (SP), its NK-1 receptor (NK1R) and the Cyclooxygenase-2 (COX-2) enzyme in TNBC patients. Upregulation of the SP/NK1R system and COX-2 influences major signalling pathways involved in cell proliferation, growth, survival, angiogenesis, inflammation, metastasis and stem cell activity. The simultaneous activation and crosstalk between the pathways activated by SP/NK1R and COX-2 consequently increase the levels of key regulators of self-renewal pathways in CSCs, promoting stemness. The combination therapy with NK1R antagonists and COX-2 inhibitors can simultaneously target TNBC cells and CSCs, thereby enhancing treatment efficacy and reducing the risk of recurrence and relapse. This review discusses the rationale for combining NK1R antagonists and COX-2 inhibitors for the better management of TNBC and a novel strategy to deliver drug cargo precisely to the tumour site to address the challenges associated with off-target binding.

Cytokeratin 15 is a novel and independent predictor of poor outcome in luminal B HER2-negative breast carcinomas

Cytokeratin 15 (CK15) has been described as a stem cell marker in human organs and its expression is seen in breast tissue. CK15 expression is associated with aggressive features in endometrial and oesophageal cancers, but data on the breast are lacking. This study aims to investigate the clinicopathological associations and prognostic significance of CK15 in breast carcinomas. A multi-institute cohort of breast carcinomas were retrieved. Clinicopathological and outcome data were obtained and compared with immunohistochemical expression CK15 and a panel of biomarkers. In total, 1,476 cases were included, with an expression rate of 3.5%, preferentially expressed in luminal subtypes (p=0.024), with luminal B carcinomas being the highest (4.7%), as opposed to basal-like (1%) and HER2-overexpressed carcinomas (0%). Except for nodal stage (p=0.013) and nodal metastasis (p=0.048), oestrogen (p=0.035) and progesterone receptor (p=0.001) positivity, there were no associations with other clinicopathological parameters. A trend was observed with shorter breast cancer specific survival (BCSS) in CK15-positive luminal B carcinomas (p=0.062). On further subgroup multivariate analysis of luminal B HER2-negative carcinomas, CK15 expression exhibited robust correlation with shorter BCSS (HR=9.004, p=0.001) and disease-free survival (HR=7.085, p<0.001). Restricted to luminal breast carcinomas, specifically luminal B HER2-negative, CK15 is demonstrated to be a robust independent predictor of higher risk of recurrence and shorter survival, with potential as a clinical prognostic marker and an exclusive stem cell marker for this subgroup of carcinomas.

GALNT14 in association with GDF-15 promotes stemness and drug resistance through β-catenin signalling pathway in breast cancer

BACKGROUND

Altered glycosylation plays a role in carcinogenesis. GALNT14 promotes cancer stem-like properties and drug resistance. GDF-15 is known to induces drug resistance and stemness markers for maintenance of breast cancer (BC) stem-like cell state. Currently there is lack of data on association of GDF-15 and GALNTs. In this study, the expression and interaction of GALNT14 and GDF-15 with stemness (OCT4 and SOX2) and drug resistance (ABCC5) markers were evaluated in BC.

METHODS

We investigated tumour tissue from 30 BC patients and adjacent non-tumour tissues. Expression of serum GALNT14 from BC patients and matched healthy controls was evaluated. Expression of GALNT14, GDF-15, OCT4, SOX2, ABCC5, and β-catenin in BC tissue was determined by RT-PCR. Knockdown of GALNT14 and GDF-15 in the MCF-7 cell line was done through siRNA, gene expression and protein expression of β-catenin by western blot were determined.

RESULTS

A significant increase in the expression of GALNT14, GDF-15, OCT4, SOX2, ABCC5, and β-catenin was observed in BC tumour tissues compared to adjacent non-tumour tissues. The serum level of GALNT14 was significantly high in BC patients (80.7 ± 65.3 pg/ml) compared to healthy controls (12.2 ± 9.12 pg/ml) (p < 0.000). To further analyse the signalling pathway involved in BC stemness and drug resistance, GALNT14 and GDF-15 were knocked down in the MCF-7 cell line, and it was observed that after knockdown, the expression level of OCT4, SOX2, ABCC5, and β-catenin was decreased, and co-knockdown with GALNT14 and GDF-15 further decreased the expression of genes.

CONCLUSION

It can be concluded that GALNT14, in association with GDF-15, promotes stemness and intrinsic drug resistance in BC, possibly through the β-catenin signalling pathway.

Exploring the Synergistic Effect of Sildenafil and Green Tea Polyphenols on Breast Cancer Stem Cell-like Cells and their Parental Cells: A Potential Novel Therapeutic Approach

BACKGROUND

Many cancer studies have intensely focused on the role of diet, among other factors involved in cancer establishment. The positive effect of green tea polyphenols (GTP) on controlling breast cancer cells has been reported in several studies. Cancer stem cell-like cells (CSC-LCs) possessing self-renewal, metastatic, and drug-resistant capacities are considered prominent therapeutic targets. In many tumors, inducible nitric oxide synthase (iNOS) expression levels are high; however, they have a dual effect on breast cancer pathogenesis.

OBJECTIVE

This study aimed to investigate the cytotoxicity of the iNOS agonist (Sildenafil) and antagonist (LNAME), both alone and in combination with GTP, on MDA-MB-231, CD44+/CD24- CSC-LCs, and their parental cells (MCF-7).

METHODS

The cell viability assay has been studied using the MTT assay. To analyze drug-drug combinations, CompuSyn and Combenefit software were used. The cytotoxicity mechanism was determined using flow cytometric analysis.

RESULTS

L-NAME and GTP showed a synergistic effect on MDA-MB-231 and CSC-LCs. Such an effect was not observed on MCF-7. Sildenafil and GTP, on the other hand, showed synergistic cytotoxicity in all the cells mentioned above. Flow cytometric tests resulted in more than 70% apoptosis in MDA-MB-231 and MCF-7. Also, sub-G1 arrest among MCF-7 cells and a considerable decrease in ROS production by MDA-MB-231 cells following treatment with Sildenafil and GTP were observed.

CONCLUSION

Sildenafil, in combination with flavonoids, may be considered a novel strategy for cancer treatment.

Hypericum roeperianum bark extract suppresses breast cancer proliferation via induction of apoptosis, downregulation of PI3K/Akt/mTOR signaling cascade and reversal of EMT

ETHNOPHARMACOLOGICAL RELEVANCE

Hypericum roeperianum is a medicinal spice traditionally used in West Africa to treat female sterility, fungal infections, and cancer. It has previously been reported that H. roeperianum exhibits cytotoxic potential by reducing the viability of cancer cells involving multidrug-resistant phenotypes, but its underlying molecular mechanism remains unknown.

AIM OF THE STUDY

The mechanistic involvement of H. roeperianum methanolic crude extract (HRC) in attenuating breast cancer progression by exploring the effects on mitochondrial apoptosis and epithelial-mesenchymal transition (EMT) was investigated.

MATERIALS AND METHODS

In the present study, we examined the anticancer properties of HRC through MTT assay, colony formation, wound healing assay, spheroid formation, DNA fragmentation and flow cytometry for cell cycle arrest, apoptosis (Annexin V/PI staining) and mitochondrial membrane potential (MMP) (JC-1) detection. In addition, western blot analysis of various proteins and quantitative real time PCR of various genes involved in apoptosis, EMT and the PI3K/Akt/mToR signal transduction pathway were performed.

RESULTS

This study revealed that HRC treatment significantly decreased breast cancer cell viability, colony forming efficiency and reduced the ability of cell migration and spheroid formation. HRC also induced apoptosis in MDA-MB-231 and MCF-7 via promoting G0/G1 cell cycle arrest, disruption of mitochondrial membrane potential and induction of DNA damage. The crude extract induced apoptosis by activating the intrinsic pathway with a stronger effect that relies on the combined potency of associated molecular markers including Bax, Bad, Bcl-2, cytochrome C, caspase-9, and cleaved-PARP. It was also found that HRC regulates the PI3K/Akt/mToR pathway. In addition, HRC inhibited EMT by expressional alteration of Vimentin and E-cadherin, as well as the regulatory transcription factors such as Snail and Slug. The in vitro findings reflected similar mechanistic approach in 4T1 cell induced syngeneic mice model, indicating the reduction of tumor volume along with the significant expressional alteration of EMT and apoptotic markers.

CONCLUSION

Taken together the findings concluded that H. roeperianum is a potential source of cytotoxic phytochemicals that exhibit abortifacient effect on breast cancer, both in vitro and in vivo, thus could further be utilized in breast cancer therapy.

TET1 regulates stem cell properties and cell cycle of Cancer stem cells in triple-negative breast cancer via DNA demethylation

The role of cancer stem cells in metastasis, recurrence, and resistance to conventional therapies is significant. Addressing these cells could potentially decrease cancer reoccurrences and mortality rates. TET1, a crucial gene involved in stem cell self-renewal and potency, may also play a part in cancer stem cells, which warrants further research. To explore the role of TET1 in cancer stem cells, we conducted experiments involving loss and gain. We then analyzed factors such as migration, invasion, cell cycle, cell viability, mammosphere formation, and the CD44+/CD24- subpopulation of cancer cells. We also investigate the influence of TET1 on CCNB1, CDK1, and OCT4. Our study reveals that TET1 can regulate the phenotype of cancer stem cells via OCT4. Additionally, it can control the cell cycle by increasing CDK1 and CCNB1 levels. These findings suggest that targeting DNA methylation and TET1 could be an effective strategy to overcome obstacles posed by Cancer stem cells. Our research also indicates that TET1 can influence the phenotype of cancer stem cells and the cell cycle of breast cancer cells potentially through OCT4, CCNB1, and CDK1. This highlights the importance of TET1 in breast cancer cases and suggests a potential therapeutic approach through DNA methylation and modulation of TET1.

Construction of stemness gene score by bulk and single-cell transcriptome to characterize the prognosis of breast cancer

Breast cancer (BC) is a heterogeneous disease characterized by significant differences in prognosis and therapy response. Numerous prognostic tools have been developed for breast cancer. Usually these tools are based on bulk RNA-sequencing (RNA-Seq) and ignore tumor heterogeneity. Consequently, the goal of this study was to construct a single-cell level tool for predicting the prognosis of BC patients. In this study, we constructed a stemness-risk gene score (SGS) model based on single-sample gene set enrichment analysis (ssGSEA). Patients were divided into two groups based on the median SGS. Patients with a high SGS scores had a significantly worse prognosis than those with a low SGS, and these groups exhibited differences in several tumor characteristics, such as immune infiltration, gene mutations, and copy number variants. Our results indicate that the SGS is a reliable tool for predicting prognosis and response to immunotherapy in BC patients.

Multi-Targeted and On-Demand Non-Coding RNA Regulation Nanoplatform against Metastasis and Recurrence of Triple-Negative Breast Cancer

Dysregulation of microRNAs (miRs) is the hallmark of triple-negative breast cancer (TNBC), which is closely involved with its growth, metastasis, and recurrence. Dysregulated miRs are promising targets for TNBC therapy, however, targeted and accurate regulation of multiple disordered miRs in tumors is still a great challenge. Here, a multi-targeting and on-demand non-coding RNA regulation nanoplatform (MTOR) is reported to precisely regulate disordered miRs, leading to dramatical suppression of TNBC growth, metastasis, and recurrence. With the assistance of long blood circulation, ligands of urokinase-type plasminogen activator peptide and hyaluronan located in multi-functional shells enable MTOR to actively target TNBC cells and breast cancer stem cell-like cells (BrCSCs). After entering TNBC cells and BrCSCs, MTOR is subjected to lysosomal hyaluronidase-induced shell detachment, leading to an explosion of the TAT-enriched core, thereby enhancing nuclear targeting. Subsequently, MTOR could precisely and simultaneously downregulate microRNA-21 expression and upregulate microRNA-205 expression in TNBC. In subcutaneous xenograft, orthotopic xenograft, pulmonary metastasis, and recurrence TNBC mouse models, MTOR shows remarkably synergetic effects on the inhibition of tumor growth, metastasis, and recurrence due to its on-demand regulation of disordered miRs. This MTOR system opens a new avenue for on-demand regulation of disordered miRs against growth, metastasis, and recurrence of TNBC.

Basal-like mammary carcinomas stimulate cancer stem cell properties through AXL-signaling to induce chemotherapy resistance

Basal-like breast cancer (BLBC) is the most aggressive and heterogeneous breast cancer (BC) subtype. Conventional chemotherapies represent next to surgery the most frequently employed treatment options. Unfortunately, resistant tumor phenotypes often develop, resulting in therapeutic failure. To identify the early events occurring upon the first drug application and initiating chemotherapy resistance in BLBC, we leveraged the WAP-T syngeneic mammary carcinoma mouse model and we developed a strategy combining magnetic-activated cell sorting (MACS)-based tumor cell enrichment with high-throughput transcriptome analyses. We discovered that chemotherapy induced a massive gene expression reprogramming toward stemness acquisition to tolerate and survive the cytotoxic treatment in vitro and in vivo. Retransplantation experiments revealed that one single cycle of cytotoxic drug combination therapy (Cyclophosphamide, Adriamycin and 5-Fluorouracil) suffices to induce resistant tumor cell phenotypes in vivo. We identified Axl and its ligand Pros1 as highly induced genes driving cancer stem cell (CSC) properties upon chemotherapy in vivo and in vitro. Furthermore, from our analysis of BLBC patient datasets, we found that AXL expression is also strongly correlated with CSC-gene signatures, a poor response to conventional therapies and worse survival outcomes in those patients. Finally, we demonstrate that AXL inhibition sensitized BLBC-cells to cytotoxic treatment in vitro. Together, our data support AXL as a promising therapeutic target to optimize the efficiency of conventional cytotoxic therapies in BLBC.

The anti-breast cancer stem cell properties of gold(i)-non-steroidal anti-inflammatory drug complexes

The anti-breast cancer stem cell (CSC) properties of a series of gold(i) complexes comprising various non-steroidal anti-inflammatory drugs (NSAIDs) and triphenylphosphine 1-8 are reported. The most effective gold(i)-NSAID complex 1, containing indomethacin, exhibits greater potency for breast CSCs than bulk breast cancer cells (up to 80-fold). Furthermore, 1 reduces mammosphere viability to a better extent than a panel of clinically used breast cancer drugs and salinomycin, an established anti-breast CSC agent. Mechanistic studies suggest 1-induced breast CSC death results from breast CSC entry, cytoplasm localisation, an increase in intracellular reactive oxygen species levels, cyclooxygenase-2 downregulation and inhibition, and apoptosis. Remarkably, 1 also significantly inhibits tumour growth in a murine metastatic triple-negative breast cancer model. To the best of our knowledge, 1 is the first gold complex of any geometry or oxidation state to demonstrate anti-breast CSC properties.

Notch signaling sculpts the stem cell niche

Adult stem cells depend on their niches for regulatory signaling that controls their maintenance, division, and their progeny differentiation. While communication between various types of stem cells and their niches is becoming clearer, the process of stem cell niche establishment is still not very well understood. Model genetic organisms provide simplified systems to address various complex questions, for example, how is a stem cell niche formed? What signaling cascades induce the stem cell niche formation? Are the mechanisms of stem cell niche formation conserved? Notch signaling is an evolutionarily conserved pathway first identified in fruit flies, crucial in fate acquisition and spatiotemporal patterning. While the core logic behind its activity is fairly simple and requires direct cell-cell interaction, it reaches an astonishing complexity and versatility by combining its different modes of action. Subtleties such as equivalency between communicating cells, their physical distance, receptor and ligand processing, and endocytosis can have an effect on the way the events unfold, and this review explores some important general mechanisms of action, later on focusing on its involvement in stem cell niche formation. First, looking at invertebrates, we will examine how Notch signaling induces the formation of germline stem cell niche in male and female Drosophila. In the developing testis, a group of somatic gonadal precursor cells receive Delta signals from the gut, activating Notch signaling and sealing their fate as niche cells even before larval hatching. Meanwhile, the ovarian germline stem cell niche is built later during late larval stages and requires a two-step process that involves terminal filament formation and cap cell specification. Intriguingly, double security mechanisms of Notch signaling activation coordinated by the soma or the germline control both steps to ensure the robustness of niche assembly. Second, in the vast domains of mammalian cellular signaling, there is an emerging picture of Notch being an active player in a variety of tissues in health and disease. Notch involvement has been shown in stem cell niche establishment in multiple organs, including the brain, muscle, and intestine, where the stem cell niches are essential for the maintenance of adult stem cells. But adult stem cells are not the only cells looking for a home. Cancer stem cells use Notch signaling at specific stages to gain an advantage over endogenous tissue and overpower it, at the same time acquiring migratory and invasive abilities to claim new tissues (e.g., bone) as their territory. Moreover, in vitro models such as organoids reveal similar Notch employment when it comes to the developing stem cell niches. Therefore, a better understanding of the processes regulating stem cell niche assembly is key for the fields of stem cell biology and regenerative medicines.

Targeting Breast Cancer Stem Cells Using Naturally Occurring Phytoestrogens

Breast cancer therapies have made significant strides in improving survival for patients over the past decades. However, recurrence and drug resistance continue to challenge long-term recurrence-free and overall survival rates. Mounting evidence supports the cancer stem cell model in which the existence of a small population of breast cancer stem cells (BCSCs) within the tumor enables these cells to evade conventional therapies and repopulate the tumor, giving rise to more aggressive, recurrent tumors. Thus, successful breast cancer therapy would need to target these BCSCs, as well the tumor bulk cells. Since the Women’s Health Initiative study reported an increased risk of breast cancer with the use of conventional hormone replacement therapy in postmenopausal women, many have turned their attention to phytoestrogens as a natural alternative. Phytoestrogens are plant compounds that share structural similarities with human estrogens and can bind to the estrogen receptors to alter the endocrine responses. Recent studies have found that phytoestrogens can also target BCSCs and have the potential to complement conventional therapy eradicating BCSCs. This review summarized the latest findings of different phytoestrogens and their effect on BCSCs, along with their mechanisms of action, including selective estrogen receptor binding and inhibition of molecular pathways used by BCSCs. The latest results of phytoestrogens in clinical trials are also discussed to further evaluate the use of phytoestrogen in the treatment and prevention of breast cancer.

Breast Cancer Therapy: The Potential Role of Mesenchymal Stem Cells in Translational Biomedical Research

The potential role of mesenchymal stem cells (MSCs) in the treatment of metastatic cancers, including breast cancer, has been investigated for many years leading to encouraging results. The role of fat grafting and the related adipose-derived mesenchymal stem cells (AD-MSCs) has been detailed and described for breast reconstruction purposes confirming the safety of AD-MSCs. MSCs have great potential for delivering anticancer agents, suicide genes, and oncolytic viruses to tumors. Currently, many studies have focused on the products of MSCs, including extracellular vesicles (EVs), as a cell-free therapy. This work aimed to review and discuss the current knowledge on MSCs and their EVs in breast cancer therapy.

Computationally repurposing drugs for breast cancer subtypes using a network-based approach

‘De novo’ drug discovery is costly, slow, and with high risk. Repurposing known drugs for treatment of other diseases offers a fast, low-cost/risk and highly-efficient method toward development of efficacious treatments. The emergence of large-scale heterogeneous biomolecular networks, molecular, chemical and bioactivity data, and genomic and phenotypic data of pharmacological compounds is enabling the development of new area of drug repurposing called ‘in silico’ drug repurposing, i.e., computational drug repurposing (CDR). The aim of CDR is to discover new indications for an existing drug (drug-centric) or to identify effective drugs for a disease (disease-centric). Both drug-centric and disease-centric approaches have the common challenge of either assessing the similarity or connections between drugs and diseases. However, traditional CDR is fraught with many challenges due to the underlying complex pharmacology and biology of diseases, genes, and drugs, as well as the complexity of their associations. As such, capturing highly non-linear associations among drugs, genes, diseases by most existing CDR methods has been challenging. We propose a network-based integration approach that can best capture knowledge (and complex relationships) contained within and between drugs, genes and disease data. A network-based machine learning approach is applied thereafter by using the extracted knowledge and relationships in order to identify single and pair of approved or experimental drugs with potential therapeutic effects on different breast cancer subtypes. Indeed, further clinical analysis is needed to confirm the therapeutic effects of identified drugs on each breast cancer subtype.

Bioinformatic Investigation of Micro RNA-802 Target Genes, Protein Networks, and Its Potential Prognostic Value in Breast Cancer

Background

An increasing number of studies have suggested that unveiling the molecular network of miRNAs may provide novel therapeutic targets or biomarkers. In this study, we investigated the probable molecular functions that are related to microRNA-802 (miR-802) and evaluated its prognostic value in breast cancer utilizing bioinformatics tools.

Methods

PPI network, pathway enrichment and transcription factor analysis were applied to obtain hub genes among overlapping genes of four miRNA target prediction databases. Prognosis value assessments and expression analysis of hub genes using bioinformatics tools, as well as their literature validation were performed.

Results

Our results showed a significant correlation of the miR-802 overexpression with poor patient survival rate (BC, p=2.7e-5). We determined 247 target genes significant for GO and KEGG terms. Analysis of TFs by TRUST showed that RUNX3, FOXO3, and E2F1 are possible TFs that regulate the miR-802 expression and target genes network. According to our analysis; 21 genes might have an important function in miR-802 molecular processes and regulatory networks. The result shows that among these 21 genes, 8 genes (CASC3, ITGA4, AGO3, TARDBP, MED13L, SF1, SNRPE and CRNKL1) are positively correlated with patient survival. Therefore these genes could be considered and experimentally evaluated as a prognostic biomarker for breast cancer.

Conclusion

The comprehensive bioinformatics study on miR-802 target genes provided insight into miR-802 mediated pathways and processes. Furthermore, representing candidate target genes by prognostic values indicates the potential clinical application of miR-802 in breast cancer.

The Role of Circulating Tumor Cells in the Prognosis of Metastatic Triple-Negative Breast Cancers: A Systematic Review of the Literature

Breast cancer is one of the leading causes of death in women worldwide. One subtype of breast cancer is the triple-negative, which accounts for 15% of total breast cancer cases and is known for its poor prognosis. The main cause of death is due to metastasis. Circulating tumor cells (CTCs) play a key role in the metastatic process. CTCs arise either by detaching from the primary tumor or from cancer stem cells undergoing an epithelial-to-mesenchymal transition (EMT). This review aims to present up-to-date data concerning the role of CTC numbers in relation to the prognostic and treatment response in metastatic triple-negative breast cancer (mTNBC) patients, and also to discuss the methods used for CTCs’ identification. A search in the MEDLINE database was performed. A total of 234 articles were identified. The results of the 24 eligible studies showed that positive CTC status is associated with shorter overall survival (OS) and progression-free survival (PFS) in mTNBC patients. Furthermore, a decrease in number of CTCs during therapy seems to be a favorable prognostic factor, making CTCs’ detection an important prognostic tool before and during therapy in mTNBC patients. The methods used for CTC detection are still developing and need further improvement.

Aptamer-armed nanostructures improve the chemotherapy outcome of triple-negative breast cancer

Triple-negative breast cancer is an aggressive subtype of breast cancer that is primarily treated using systemic chemotherapy due to the lack of a specific cell surface marker for drug delivery. Cancer cell-specific aptamer-mediated drug delivery is a promising targeted chemotherapy for marker-unknown cancers. Using a poorly differentiated carcinoma cell-specific DNA aptamer (PDGC21T), we formed a self-assembling circinate DNA nanoparticle (Apt^21TNP) that binds triple-negative breast cancer cells. Using our previously designed pH-sensitive dendrimer-conjugated doxorubicin (DDOX) as the payload, we found that each nanoparticle loaded 30 doxorubicin molecules to form an Apt^21TNP-DDOX nanomedicine that is stable in human plasma. Upon cell binding, Apt^21TNP-DDOX is internalized by triple-negative breast cancer cells through the macropinocytosis pathway. Once inside cells, the low pH microenvironment in lysosomes induces doxorubicin drug payload release from Apt^21TNP-DDOX. Our in vitro studies demonstrate that Apt^21TNP-DDOX can preferentially bind triple-negative breast cancer cells to induce cell death. Further, we show that Apt^21TNP-DDOX can accumulate in subcutaneous MDA-MB-231 tumors in mice following systemic administration to reduce tumor burden, minimize side effects, and improve animal survival. Together, our results demonstrate that Apt^21TNP-mediated doxorubicin delivery is a potent, targeted chemotherapy for triple-negative breast cancer that may alleviate side effects in patients.

Integration of Genomic Profiling and Organoid Development in Precision Oncology

Precision oncology involves an innovative personalized treatment strategy for each cancer patient that provides strategies and options for cancer treatment. Currently, personalized cancer medicine is primarily based on molecular matching. Next-generation sequencing and related technologies, such as single-cell whole-transcriptome sequencing, enable the accurate elucidation of the genetic landscape in individual cancer patients and consequently provide clinical benefits. Furthermore, advances in cancer organoid models that represent genetic variations and mutations in individual cancer patients have direct and important clinical implications in precision oncology. This review aimed to discuss recent advances, clinical potential, and limitations of genomic profiling and the use of organoids in breast and ovarian cancer. We also discuss the integration of genomic profiling and organoid models for applications in cancer precision medicine.

Advances of nanomedicines in breast cancer metastasis treatment targeting different metastatic stages

Breast cancer is the most common tumor in women, and the metastasis further increases the malignancy with extremely high mortality. However, there is almost no effective method in the clinic to completely inhibit breast cancer metastasis due to the dynamic multistep process with complex pathways and scattered occurring site. Nowadays, nanomedicines have been evidenced with great potential in treating cancer metastasis. In this review, we summarize the latest research advances of nanomedicines in anti-metastasis treatment. Strategies are categorized according to the metastasis dynamics, including primary tumor, circulating tumor cells, pre-metastatic niches and secondary tumor. In each different stage of metastasis process, nanomedicines are designed specifically with different functions. At the end of the review, we give our perspectives on current limitations and future directions in anti-metastasis therapy. We expect the review provides comprehensive understandings of anti-metastasis therapy for breast cancer, and boosts the clinical translation in the future to improve women's health.

Extracellular Vesicles and Cancer Stem Cells in Tumor Progression: New Therapeutic Perspectives

Tumor burden is a complex microenvironment where different cell populations coexist and have intense cross-talk. Among them, a heterogeneous population of tumor cells with staminal features are grouped under the definition of cancer stem cells (CSCs). CSCs are also considered responsible for tumor progression, drug resistance, and disease relapse. Furthermore, CSCs secrete a wide variety of extracellular vesicles (EVs) with different cargos, including proteins, lipids, ssDNA, dsDNA, mRNA, siRNA, or miRNA. EVs are internalized by other cells, orienting the microenvironment toward a protumorigenic and prometastatic one. Given their importance in tumor growth and metastasis, EVs could be exploited as a new therapeutic target. The inhibition of biogenesis, release, or uptake of EVs could represent an efficacious strategy to impair the cross-talk between CSCs and other cells present in the tumor microenvironment. Moreover, natural or synthetic EVs could represent suitable carriers for drugs or bioactive molecules to target specific cell populations, including CSCs. This review will discuss the role of CSCs and EVs in tumor growth, progression, and metastasis and how they affect drug resistance and disease relapse. Furthermore, we will analyze the potential role of EVs as a target or vehicle of new therapies.

Proteomics and its applications in breast cancer

Breast cancer is an individually unique, multi-faceted and chameleonic disease, an eternal challenge for the new era of high-integrated precision diagnostic and personalized oncomedicine. Besides traditional single-omics fields (such as genomics, epigenomics, transcriptomics and metabolomics) and multi-omics contributions (proteogenomics, proteotranscriptomics or reproductomics), several new "-omics" approaches and exciting proteomics subfields are contributing to basic and advanced understanding of these "multiple diseases termed breast cancer": phenomics/cellomics, connectomics and interactomics, secretomics, matrisomics, exosomics, angiomics, chaperomics and epichaperomics, phosphoproteomics, ubiquitinomics, metalloproteomics, terminomics, degradomics and metadegradomics, adhesomics, stressomics, microbiomics, immunomics, salivaomics, materiomics and other biomics. Throughout the extremely complex neoplastic process, a Breast Cancer Cell Continuum Concept (BCCCC) has been modeled in this review as a spatio-temporal and holistic approach, as long as the breast cancer represents a complex cascade comprising successively integrated populations of heterogeneous tumor and cancer-associated cells, that reflect the carcinoma's progression from a "driving mutation" and formation of the breast primary tumor, toward the distant secondary tumors in different tissues and organs, via circulating tumor cell populations. This BCCCC is widely sustained by a Breast Cancer Proteomic Continuum Concept (BCPCC), where each phenotype of neoplastic and tumor-associated cells is characterized by a changing and adaptive proteomic profile detected in solid and liquid minimal invasive biopsies by complex proteomics approaches. Such a profile is created, beginning with the proteomic landscape of different neoplastic cell populations and cancer-associated cells, followed by subsequent analysis of protein biomarkers involved in epithelial-mesenchymal transition and intravasation, circulating tumor cell proteomics, and, finally, by protein biomarkers that highlight the extravasation and distant metastatic invasion. Proteomics technologies are producing important data in breast cancer diagnostic, prognostic, and predictive biomarkers discovery and validation, are detecting genetic aberrations at the proteome level, describing functional and regulatory pathways and emphasizing specific protein and peptide profiles in human tissues, biological fluids, cell lines and animal models. Also, proteomics can identify different breast cancer subtypes and specific protein and proteoform expression, can assess the efficacy of cancer therapies at cellular and tissular level and can even identify new therapeutic target proteins in clinical studies.

Mesenchymal Stem Cells in Adipose Tissue and Extracellular Vesicles in Ovarian Cancer Patients: A Bridge toward Metastatic Diffusion or a New Therapeutic Opportunity?

Ovarian cancer is one of the deadliest malignancies among women. Approximately 75% of the patients with ovarian cancer are diagnosed with advanced disease that already has metastasis, particularly to the omentum. The omentum constitutes the ideal soil for ovarian cancer metastasis due to a complex intraperitoneal milieu that favors and supports the whole metastatic process. Adipose-derived stem/stromal cells (ADSCs) are part of this microenvironment and foster tumor progression via sustained paracrine secretion, including extracellular vesicles (EVs). Nonetheless, the preferential relationship between ADSCs, ADSC-derived EVs, and ovarian cancer cells could be exploited to use ADSCs and EVs as a vehicle for anti-cancer therapies. This review will analyze the strict relations between tumor progression, metastatic disease, and adipose tissue with its staminal components. In addition, we will describe the crosstalk and biologic relationship between ADSCs and tumor cells, the role of EVs in intercellular communication, the establishment of drug resistance, metastatic capacity, and ovarian cancer progression. We will analyze the new therapeutic opportunities in treating ovarian cancer offered by ADSCs and EVs as a vehicle for therapeutic molecules to target precisely tumor cells and limit the systemic adverse effects. Finally, we will discuss the limitations of these therapeutic approaches.

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.

Expression analysis of CD24 and CD44 transcripts in Iranian breast cancer patients

BACKGROUND

The importance of cancer stem cells (CSCs) in initiation and progression of breast cancer has been well established. This population of cells is characterized by high expression of CD44 and low expression of CD24.

OBJECTIVE

However, the relative abundance of CD24 and CD44 transcripts in breast cancer tissues and adjacent non-cancerous tissues (ANCTs) has not been quantified yet.

METHODS

In the present investigation, we assessed expression of CD24 and CD44 at transcript level in breast cancer tissues and ANCTs in association with clinical determinants of patients' outcome and parameters that predict response to therapeutic options.

RESULTS

There was no significant difference in expression of CD24 and CD44 in breast cancer tissues compared with ANCTs (Expression ratios: 1.03 and 0.84, P values: 0.92 and 0.61, respectively). However, CD44 expression was associated with tumor size in a way this gene was up-regulated in all of small sized (≤2 cm) tumors compared with the corresponding ANCTs (P value = 0.04). Besides, CD44 expression was significantly higher in tumors with extracapsular nodal extension compared with those without extension (P = 0.04). Expression of CD24 was higher in grade 3 tumors compared with grade 2 tumors (P = 0.04).

CONCLUSION

Expression levels of CD24 and CD44 were correlated with each other in ANCTs but not in tumoral tissues. The current study shows another aspect of CSC markers in the development of breast cancer.

Biological characteristics of a sub-population of cancer stem cells from two triple-negative breast tumour cell lines

Triple-negative breast tumours (TNBTs) make up 15-20% of all breast tumours. There is no treatment for them, and the role that cancer stem cells (CSCs) have in carcinogenesis is still unclear, so finding markers and therapeutic targets in CSC exosomes requires these cells to exist as a homogeneous cell population. The objective of this work was to determine differences in ultrastructural morphology, proliferative capacity, and mouse-xenotransplantation characteristics of the MDA-MB-231 and MDA-MB-436 TNBT cell lines with the CD44 high /CD24 low phenotype in order to study their exosomes. The results show that the CD44 high /CD24 low MBA-MB-231 cells had a population doubling time of 41.56 h, compared to 44.79 h in the MDA-MB-436 cell line. After magnetic immunoseparation, 18.75% and 14.56% of the stem cell population of the MDA-MB-231 and MDA-MB-436 cell lines, respectively, were of the CD44 high /CD24 low phenotype, which were expanded to reach purities of 80.4% and 87.6%. The same expanded lineage in both cell lines was shown to possess the pluripotency markers Nanog and Oct4. Under a scanning electron microscope, the CD44 high /CD24 low lineage of the MBA-MD-231 cell line formed groups of more interconnected cells than this lineage of the MBA-MD-436 line. A total of 16% of the mice inoculated with the CD44 high /CD24 low lineage of either cell line presented tumours of the breast, lung, and submandibular ganglia, in whose tissues variable numbers of inoculated cells were found 30 days post-inoculation. By magnetic immunoselection, it was possible to isolate in similar quantities and characterize, expand, and xenotransplant the CD44 high /CD24 low lineage of the MDA-MB-231 and MDA-MB-436 cell lines. The former cell line has greater proliferative capacity, the two lines differ under scanning electron microscopy in how they intercommunicate, and both cell lines induce new tumours in mice and persist at least 30 days post-inoculation in the transplanted animal so their exosomes would also be different.

Progress of Breast Cancer basic research in China

Breast cancer is the most commonly diagnosed and the most lethal cancer in females both in China and worldwide. Currently, the origin of cancer stem cells, the heterogeneity of cancer cells, the mechanism of cancer metastasis and drug resistance are the most important issues that need to be addressed. Chinese investigators have recently made new discoveries in basic breast cancer researches, especially regarding cancer stem cells, cancer metabolism, and microenvironments. These efforts have led to a deeper understanding of drug resistance and metastasis and have also indicated new biomarkers and therapeutic targets. These findings emphasized the importance of the cancer stem cells for targeted therapy. In this review, we summarized the latest important findings in this field in China.

A novel Lnc408 maintains breast cancer stem cell stemness by recruiting SP3 to suppress CBY1 transcription and increasing nuclear β-catenin levels

Tumor initiation, development, and relapse may be closely associated with cancer stem cells (CSCs). The complicated mechanisms underlying the maintenance of CSCs are keeping in illustration. Long noncoding RNAs (lncRNAs), due to their multifunction in various biological processes, have been indicated to play a crucial role in CSC renewal and stemness maintenance. Using lncRNA array, we identified a novel lncRNA (named lnc408) in epithelial-mesenchymal transition-related breast CSCs (BCSCs). The lnc408 is high expressed in BCSCs in vitro and in vivo. The enhanced lnc408 is critical to BCSC characteristics and tumorigenesis. Lnc408 can recruit transcript factor SP3 to CBY1 promoter to serve as an inhibitor in CBY1 transcription in BCSCs. The high expressed CBY1 in non-BCSC interacts with 14-3-3 and β-catenin to form a ternary complex, which leads a translocation of the ternary complex into cytoplasm from nucleus and degradation of β-catenin in phosphorylation-dependent pattern. The lnc408-mediated decrease of CBY1 in BCSCs impairs the formation of 14-3-3/β-catenin/CBY1 complex, and keeps β-catenin in nucleus to promote CSC-associated CD44, SOX2, Nanog, Klf4, and c-Myc expressions and contributes to mammosphere formation; however, restoration of CBY1 expression in tumor cells reduces BCSC and its enrichment, thus lnc408 plays an essential role in maintenance of BCSC stemness. In shortly, these findings highlight that the novel lnc408 functions as an oncogenic factor by recruiting SP3 to inhibit CBY1 expression and β-catenin accumulation in nucleus to maintain stemness properties of BCSCs. Lnc408-CBY1-β-catenin signaling axis might serve as a new diagnostic and therapeutic target for breast cancer.

Signaling pathways governing breast cancer stem cells behavior

Breast cancer is the second common cancer and the leading cause of malignancy among females overall. Breast cancer stem cells (BCSCs) are a small population of breast cancer cells that play a critical role in the metastasis of breast cancer to other organs in the body. BCSCs have both self-renewal and differentiation capacities, which are thought to contribute to the aggressiveness of metastatic lesions. Therefore, targeting BCSCs can be a suitable approach for the treatment and metastasis of breast cancer. Growing evidence has indicated that the Wnt, NFκB, Notch, BMP2, STAT3, and hedgehog (Hh) signaling pathways govern epithelial-to-mesenchymal transition (EMT) activation, growth, and tumorigenesis of BCSCs in the primary regions. miRNAs as the central regulatory molecules also play critical roles in BCSC self-renewal, metastasis, and drug resistance. Hence, targeting these pathways might be a novel therapeutic approach for breast cancer diagnosis and therapy. This review discusses known signaling mechanisms involved in the stimulation or prevention of BCSC self-renewal, metastasis, and tumorigenesis.

Novel molecular regulators of breast cancer stem cell plasticity and heterogeneity

Tumors consist of heterogeneous cell populations, and tumor heterogeneity plays key roles in regulating tumorigenesis, metastasis, recurrence and resistance to anti-tumor therapies. More and more studies suggest that cancer stem cells (CSCs) promote tumorigenesis, metastasis, recurrence and drug resistance as well as are the major source for heterogeneity of cancer cells. CD24^-CD44⁺ and ALDH⁺ are the most common markers for breast cancer stem cells (BCSCs). Previous studies showed that different BCSC markers label different BCSC populations, indicating the heterogeneity of BCSCs. Therefore, defining the regulation mechanisms of heterogeneous BCSCs is essential for precisely targeting BCSCs and treating breast cancer. In this review, we summarized the novel regulators existed in BCSCs and their niches for BCSC heterogeneity which has been discovered in recent years, and discussed their regulation mechanisms and the latest corresponding cancer treatments, which will extend our understanding on BCSC heterogeneity and plasticity, and provide better prognosis prediction and more efficient novel therapeutic strategies for breast cancer.

All-trans retinoic acid and protein kinase C α/β1 inhibitor combined treatment targets cancer stem cells and impairs breast tumor progression

Breast cancer is the leading cause of cancer death among women worldwide. Blocking a single signaling pathway is often an ineffective therapy, especially in the case of aggressive or drug-resistant tumors. Since we have previously described the mechanism involved in the crosstalk between Retinoic Acid system and protein kinase C (PKC) pathway, the rationale of our study was to evaluate the effect of combining all-trans-retinoic acid (ATRA) with a classical PCK inhibitor (Gö6976) in preclinical settings. Employing hormone-independent mammary cancer models, Gö6976 and ATRA combined treatment induced a synergistic reduction in proliferative potential that correlated with an increased apoptosis and RARs modulation towards an anti-oncogenic profile. Combined treatment also impairs growth, self-renewal and clonogenicity potential of cancer stem cells and reduced tumor growth, metastatic spread and cancer stem cells frequency in vivo. An in-silico analysis of “Kaplan–Meier plotter” database indicated that low PKCα together with high RARα mRNA expression is a favorable prognosis factor for hormone-independent breast cancer patients. Here we demonstrate that a classical PKC inhibitor potentiates ATRA antitumor effects also targeting cancer stem cells growth, self-renewal and frequency.

The Role of Circulating Tumor Cells in Chemoresistant Metastatic Breast Cancer

Breast cancer is the most frequent form of cancer among women and is one of the leading causes of death. Two routes of the metastatic process have been described: linear and parallel progression. A key factor is represented by circulating tumor cells (CTCs). CTCs detach from the primary tumor or develop from cancer stem cells (CSCs) that undergo epithelial-to-mesenchymal transition (EMT). CTCs migrate to the distant site where the reverse process occurs and a new tumor arises. One of the key problems of metastatic disease is chemoresistance, which leads to treatment failure and, eventually, death. The aim of this review is to present up-to-date data regarding the role of CTCs in chemoresistance in metastatic breast cancer (MBC) patients. A search in Cochrane Library and MEDLINE databases was performed. A total of 125 articles were identified. The results of the final 12 eligible studies revealed that CTCs having stem cell features and those with mesenchymal features are aggressive subtypes of cells that survive chemotherapy, being responsible for chemoresistance and thus for disease progression in MBC patients. The hemodynamic shear stress, alongside dynamic changes among CTCs during the disease, is also an important disease progression factor.

Cancer stem cells and macrophages: molecular connections and future perspectives against cancer

Cancer stem cells (CSCs) have been considered the key drivers of cancer initiation and progression due to their unlimited self-renewal capacity and their ability to induce tumor formation. Macrophages, particularly tumor-associated macrophages (TAMs), establish a tumor microenvironment to protect and induce CSCs development and dissemination. Many studies in the past decade have been performed to understand the molecular mediators of CSCs and TAMs, and several studies have elucidated the complex crosstalk that occurs between these two cell types. The aim of this review is to define the complex crosstalk between these two cell types and to highlight potential future anti-cancer strategies.

Sulfur-Coordinated Organoiridium(III) Complexes Exert Breast Anticancer Activity via Inhibition of Wnt/β-Catenin Signaling

The sulfur-coordinated organoiridium(III) complexes pbtIrSS and ppyIrSS, which contain C,N and S,S (dithione) chelating ligands, were found to inhibit breast cancer tumorigenesis and metastasis by targeting Wnt/β-catenin signaling for the first time. Treatment with pbtIrSS and ppyIrSS induces the degradation of LRP6, thereby decreasing the protein levels of DVL2, β-catenin and activated β-catenin, resulting in downregulation of Wnt target genes CD44 and survivin. Additionally, pbtIrSS and ppyIrSS can suppress cell migration and invasion of breast cancer cells. Furthermore, both complexes show the ability to inhibit sphere formation and mediate the stemness properties of breast cancer cells. Importantly, pbtIrSS exerts potent anti-tumor and anti-metastasis effects in mouse xenograft models through the blockage of Wnt/β-catenin signaling. Taken together, our results indicate that pbtIrSS has great potential to be developed as a breast cancer therapeutic agent with a novel mechanism.

Nuclear receptors: Lipid and hormone sensors with essential roles in the control of cancer development

Nuclear receptors (NRs) are a superfamily of ligand-activated transcription factors that act as biological sensors and use a combination of mechanisms to modulate positively and negatively gene expression in a spatial and temporal manner. The highly orchestrated biological actions of several NRs influence the proliferation, differentiation, and apoptosis of many different cell types. Synthetic ligands for several NRs have been the focus of extensive drug discovery efforts for cancer intervention. This review summarizes the roles in tumour growth and metastasis of several relevant NR family members, namely androgen receptor (AR), estrogen receptor (ER), glucocorticoid receptor (GR), thyroid hormone receptor (TR), retinoic acid receptors (RARs), retinoid X receptors (RXRs), peroxisome proliferator-activated receptors (PPARs), and liver X receptors (LXRs). These studies are key to develop improved therapeutic agents based on novel modes of action with reduced side effects and overcoming resistance.

Cancer Stem Cell-Associated Pathways in the Metabolic Reprogramming of Breast Cancer

Metabolic reprogramming of cancer is now considered a hallmark of many malignant tumors, including breast cancer, which remains the most commonly diagnosed cancer in women all over the world. One of the main challenges for the effective treatment of breast cancer emanates from the existence of a subpopulation of tumor-initiating cells, known as cancer stem cells (CSCs). Over the years, several pathways involved in the regulation of CSCs have been identified and characterized. Recent research has also shown that CSCs are capable of adopting a metabolic flexibility to survive under various stressors, contributing to chemo-resistance, metastasis, and disease relapse. This review summarizes the links between the metabolic adaptations of breast cancer cells and CSC-associated pathways. Identification of the drivers capable of the metabolic rewiring in breast cancer cells and CSCs and the signaling pathways contributing to metabolic flexibility may lead to the development of effective therapeutic strategies. This review also covers the role of these metabolic adaptation in conferring drug resistance and metastasis in breast CSCs.

Repurposing of Fluvastatin as an Anticancer Agent against Breast Cancer Stem Cells via Encapsulation in a Hyaluronan-Conjugated Liposome

Fluvastatin (FLUVA), which is a common anti-hypercholesterolemia drug, exhibits potential anticancer activity as it suppresses the proliferation, angiogenesis, and metastasis of breast cancer cells via inhibiting 3-hydroxy-methyl glutaryl-coenzyme A (HMG-CoA) reductase. In this study, hyaluronan-conjugated FLUVA-encapsulating liposomes (HA-L-FLUVA) were evaluated for their anticancer efficacy in vitro and in vivo. The particle size, zeta potential, and encapsulation efficiency of HA-L-FLUVA were 158.36 ± 1.78 nm, −24.85 ± 6.26 mV, and 35%, respectively. Growth inhibition of breast cancer stem cells (BCSCs) by HA-L-FLUVA was more effective than that by free FLUVA. The half maximal inhibitory concentration (IC₅₀) values of FLUVA, L-FLVUA, and HA-L-FLUVA were 0.16, 0.17, and 0.09 μM, respectively. The in vivo anticancer effect of HA-L-FLUVA in combination with doxorubicin (DOX) was more effective than that of free FLUVA, free DOX, and HA-L-FLUVA. The longest survival of mice was achieved by treatment with FLUVA (15 mg/kg) and HA-L-FLUVA (15 mg/kg) + DOX (3 mg/kg), followed by HA-L-FLUVA (15 mg/kg), Dulbecco’s phosphate buffered saline, and DOX (3 mg/kg). No more than 10% body weight loss was observed in the mice injected with FLUVA, indicating that the drug was not toxic. Taken together, these results indicate that HA-L-FLUVA could serve as an effective anticancer drug by inhibiting the growth of both breast cancer cells and cancer stem cells.

SIPA1 enhances SMAD2/3 expression to maintain stem cell features in breast cancer cells

SIPA1, a GTPase activating protein that negatively regulates Ras-related protein (Rap), is a potential modulator of tumor metastasis and recurrence. In this study, we first showed that SIPA1 facilitated the stemness features of breast cancer cells, such as of tumorsphere formation capability and the expression of stemness marker CD44. In addition, SIPA1 promoted the expression of four stemness-associated transcription factors through increasing the expression of SMAD2 and SMAD3 in vitro and in vivo. The stemness features were abolished by blocking the phosphorylation of SMAD3 with its specific inhibitor SIS3. Furthermore, SIPA1 decreased the breast cancer cell sensitivity to chemotherapy drugs. This effect was, however, competitively reversed by blocking the SMAD3 phosphorylation by SIS3 treatment in breast cancer cells. Taken together, SIPA1 promotes and sustains the stemness of breast cancer cells and their resistance to chemotherapy by increasing the expression of SMAD2 and SMAD3, and blocking SMAD3 phosphorylation could suppress the cancer cell stemness and increase the sensitivity to chemotherapy in breast cancer cells expressing a high level of SIPA1.

Differential sensitivities of triple-negative breast cancer stem cell towards various doses of vitamin C: An insight into the internal antioxidant systems

Cancer stem cells (CSCs) are quiescent and self-renewing, having low levels of reactive oxygen species (ROS), and are responsible for cancer recurrence after chemotherapy and radiotherapy. However, the interplay between the ROS production and scavenging from the oxidative stress has never been studied in breast CSCs. In this present study, we have investigated the cellular energetics of two triple-negative breast cancer stem cells (MDA-MB-231 and MDA-MB-468) treated with two pharmacological doses of vitamin C (10 and 20 mM) that generated ROS. Our results indicate a differential behavior of ROS scavenging by both the CSCs. MDA-MB-468 CSCs exhibited higher resistance to ROS induced damage owing to the higher antioxidant activity, lower mitochondrial damage, and less decrease in membrane potential (ΔΨ_m ) as compared with MDA-MB-231 CSCs. Moreover, MDA-MB-231 CSCs exhibited an intrinsic apoptosis pathway by activating the cytochrome c, caspase-9, 3, 7, and cleaved PARP upon treatment with vitamin C. This data suggests a possible strategy for targeting breast CSCs using vitamin C. Taken together, the CSCs from MDA-MB-231 could be easily targeted by high/pharmacological doses of vitamin C (≥20 mM) thereby indicating a less robust internal antioxidant machinery.

Lineage tracing: technology tool for exploring the development, regeneration, and disease of the digestive system

Lineage tracing is the most widely used technique to track the migration, proliferation, and differentiation of specific cells in vivo. The currently available gene-targeting technologies have been developing for decades to study organogenesis, tissue injury repairing, and tumor progression by tracing the fates of individual cells. Recently, lineage tracing has expanded the platforms available for disease model establishment, drug screening, cell plasticity research, and personalized medicine development in a molecular and cellular biology perspective. Lineage tracing provides new views for exploring digestive organ development and regeneration and techniques for digestive disease causes and progression. This review focuses on the lineage tracing technology and its application in digestive diseases.

The Role of Breast Cancer Stem Cell-Related Biomarkers as Prognostic Factors

Breast cancer is one of the leading causes of cancer-related deaths in women worldwide, and its incidence is on the rise. A small fraction of cancer stem cells was identified within the tumour bulk, which are regarded as cancer-initiating cells, possess self-renewal and propagation potential, and a key driver for tumour heterogeneity and disease progression. Cancer heterogeneity reduces the overall efficacy of chemotherapy and contributes to treatment failure and relapse. The cell-surface and subcellular biomarkers related to breast cancer stem cell (BCSC) phenotypes are increasingly being recognised. These biomarkers are useful for the isolation of BCSCs and can serve as potential therapeutic targets and prognostic tools to monitor treatment responses. Recently, the role of noncoding microRNAs (miRNAs) has extensively been explored as novel biomarker molecules for breast cancer diagnosis and prognosis with high specificity and sensitivity. An in-depth understanding of the biological roles of miRNA in breast carcinogenesis provides insights into the pathways of cancer development and its utility for disease prognostication. This review gives an overview of stem cells, highlights the biomarkers expressed in BCSCs and describes their potential role as prognostic indicators.

Single-cell RNA sequencing in breast cancer: Understanding tumor heterogeneity and paving roads to individualized therapy

Single‐cell RNA sequencing (scRNA‐seq) is a novel technology that allows transcriptomic analyses of individual cells. During the past decade, scRNA‐seq sensitivity, accuracy, and efficiency have improved due to innovations including more sensitive, automated, and cost‐effective single‐cell isolation methods with higher throughput as well as ongoing technological development of scRNA‐seq protocols. Among the variety of current approaches with distinct features, researchers can choose the most suitable method to carry out their research. By profiling single cells in a complex population mix, scRNA‐seq presents great advantages over traditional sequencing methods in dissecting heterogeneity in cell populations hidden in bulk analysis and exploring rare cell types associated with tumorigenesis and metastasis. scRNA‐seq studies in recent years in the field of breast cancer research have clustered breast cancer cell populations with different molecular subtypes to identify distinct populations that may correlate with poor prognosis and drug resistance. The technology has also been used to explain tumor microenvironment heterogeneity by identifying distinct immune cell subsets that may be associated with immunosurveillance and are potential immunotherapy targets. Moreover, scRNA‐seq has diverse applications in breast cancer research besides exploring heterogeneity, including the analysis of cell‐cell communications, regulatory single‐cell states, immune cell distributions, and more. scRNA‐seq is also a promising tool that can facilitate individualized therapy due to its ability to define cell subsets with potential treatment targets. Although scRNA‐seq studies of therapeutic selection in breast cancer are currently limited, the application of this technology in this field is prospective. Joint efforts and original ideas are needed to better implement scRNA‐seq technologies in breast cancer research to pave the way for individualized treatment management. This review provides a brief introduction on the currently available scRNA‐seq approaches along with their corresponding strengths and weaknesses and may act as a reference for the selection of suitable methods for research. We also discuss the current applications of scRNA‐seq in breast cancer research for tumor heterogeneity analysis, individualized therapy, and the other research directions mentioned above by reviewing corresponding published studies. Finally, we discuss the limitations of current scRNA‐seq technologies and technical problems that remain to be overcome.

Sphingosine Kinase 1 Regulates the Survival of Breast Cancer Stem Cells and Non-stem Breast Cancer Cells by Suppression of STAT1

Cancer stem cells (CSCs) represent rare tumor cell populations capable of self-renewal, differentiation, and tumor initiation and are highly resistant to chemotherapy and radiotherapy. Thus, therapeutic approaches that can effectively target CSCs and tumor cells could be the key to efficient tumor treatment. In this study, we explored the function of SPHK1 in breast CSCs and non-CSCs. We showed that RNAi-mediated knockdown of SPHK1 inhibited cell proliferation and induced apoptosis in both breast CSCs and non-CSCs, while ectopic expression of SPHK1 enhanced breast CSC survival and mammosphere forming efficiency. We identified STAT1 and IFN signaling as key regulatory targets of SPHK1 and demonstrated that an important mechanism by which SPHK1 promotes cancer cell survival is through the suppression of STAT1. We further demonstrated that SPHK1 inhibitors, FTY720 and PF543, synergized with doxorubicin in targeting both breast CSCs and non-CSCs. In conclusion, we provide important evidence that SPHK1 is a key regulator of cell survival and proliferation in breast CSCs and non-CSCs and is an attractive target for the design of future therapies.

Potential Role of MSC/Cancer Cell Fusion and EMT for Breast Cancer Stem Cell Formation

Solid tumors comprise of maturated cancer cells and self-renewing cancer stem-like cells (CSCs), which are associated with various other nontumorigenic cell populations in the tumor microenvironment. In addition to immune cells, endothelial cells, fibroblasts, and further cell types, mesenchymal stroma/stem-like cells (MSC) represent an important cell population recruited to tumor sites and predominantly interacting with the different cancer cells. Breast cancer models were among the first to reveal distinct properties of CSCs, however, the cellular process(es) through which these cells are generated, maintained, and expanded within neoplastic tissues remains incompletely understood. Here, we discuss several possible scenarios that are not mutually exclusive but may even act synergistically: fusion of cancer cells with MSC to yield hybrid cells and/or the induction of epithelial-mesenchymal transition (EMT) in breast cancer cells by MSC, which can relay signals for retrodifferentiation and eventually, the generation of breast CSCs (BCSCs). In either case, the consequences may be promotion of self-renewal capacity, tumor cell plasticity and heterogeneity, an increase in the cancer cells’ invasive and metastatic potential, and the acquisition of resistance mechanisms towards chemo- or radiotherapy. While specific signaling mechanisms involved in each of these properties remain to be elucidated, the present review article focusses on a potential involvement of cancer cell fusion and EMT in the development of breast cancer stem cells.