Breast cancer stem cell: the roles and therapeutic implications

Extracellular vesicles and cancer stem cells: a deadly duo in tumor progression

The global incidence of cancer is increasing, with estimates suggesting that there will be 26 million new cases and 17 million deaths per year by 2030. Cancer stem cells (CSCs) and extracellular vesicles (EVs) are key to the resistance and advancement of cancer. They play a crucial role in tumor dynamics and resistance to therapy. CSCs, initially discovered in acute myeloid leukemia, are well-known for their involvement in tumor initiation, progression, and relapse, mostly because of their distinct characteristics, such as resistance to drugs and the ability to self-renew. EVs, which include exosomes, microvesicles, and apoptotic bodies, play a vital role in facilitating communication between cells within the tumor microenvironment (TME). They have a significant impact on cellular behaviors and contribute to genetic and epigenetic changes. This paper analyzes the mutually beneficial association between CSCs and EVs, emphasizing their role in promoting tumor spread and developing resistance mechanisms. This review aims to investigate the interaction between these entities in order to discover new approaches for attacking the complex machinery of cancer cells. It highlights the significance of CSCs and EVs as crucial targets in the advancement of novel cancer treatments, which helps stimulate additional research, promote progress in ideas for cancer treatment, and provide renewed optimism in the effort to reduce the burden of cancer.

Vitamin D suppresses CD133+/CD44 + cancer stem cell stemness by inhibiting NF-κB signaling and reducing NLRP3 expression in triple-negative breast cancer

BACKGROUND AND OBJECTIVE

This study aims to investigate the role of Vitamin D (VD) in regulating the stemness and survival of CD133+/CD44 + breast cancer stem cells, and to explore the role of NLRP3 in this process.

METHODS

Breast cancer tissues were collected for RXRα and VDR expression analysis. A triple-negative breast cancer cell line was cultured and stem-like cells (CD133 + CD44+) isolated using flow cytometry. These cells were treated with VD, analyzing their stem-like properties, apoptosis and proliferation, as well as P65 nuclear expression and NLRP3 expression. After NLRP3 inflammasome activator treatment, the parameters were reassessed. RXRα and VDR interaction was confirmed using co-immunoprecipitation (CoIP). Finally, a subcutaneous xenograft model of triple-negative breast cancer was treated with VD and subsequently analyzed for stem-like properties, proliferation, apoptosis, and NLRP3 expression levels.

RESULTS

CD133+/CD44 + stem cells expressed high levels of SOX2 and OCT4. VD treatment resulted in a significant decrease in SOX2 and OCT4 expression, fewer sphere-forming colonies, lower proliferation ability, and more apoptosis. Additionally, VD treatment inhibited NF-κB signaling and reduced NLRP3 expression. The NLRP3 activator BMS-986,299 counteracted the effects of VD in vitro. In vivo, VD inhibited the growth of breast cancer stem cells, reducing both tumor volume and weight, and decreased NLRP3, SOX2, and OCT4 expression within tumor tissues.

CONCLUSION

Findings elucidate that VD mediates the modulation of stemness in CD133+/CD44 + breast cancer stem cells through the regulation of NLRP3 expression. The research represents novel insights on the implications for the application of VD in cancer therapies.

KSR1 regulates small-cell lung carcinoma tumor initiation and cisplatin resistance

Small-cell lung cancer (SCLC) is designated a recalcitrant cancer due to its five-year relative survival rate of less than 7%. First line SCLC treatment has changed modestly in the last 40 years. The NeuroD1 subtype of SCLC (SCLC-N) commonly harbors MYC amplifications and other hallmarks of aggressive behavior. Finding novel therapeutic options that effectively eliminate residual disease observed after initial response to therapy is essential to improving SCLC patient outcome. Here we show that Kinase Suppressor of Ras 1 (KSR1), a molecular scaffold for the Raf/MEK/ERK signaling cascade is critical for clonogenicity and tumor initiation in vitro and in vivo in the highly aggressive, metastatic and therapy resistant NeuroD1 subtype of SCLC. Tumor-initiating cells (TICs) are reported as the sanctuary population within the bulk tumor responsible for therapeutic resistance and relapse. Previous studies concluded ERK activation was inhibitory to growth and tumor development. We show that signaling through KSR1 is conserved in SCLC-N and that it regulates tumor initiation through interaction with ERK. We further show that KSR1 mediates cisplatin resistance in SCLC-N cells. While 50% of control SCLC-N cells show resistance after 6 weeks of exposure to cisplatin, CRISPR/Cas9-mediated KSR1 knockout prevents resistance in >90% of SCLC-N cells. KSR1 KO also significantly enhances the ability of cisplatin to decrease SCLC-N TICs, indicating that targeting KSR1 might be selectively toxic to cells responsible for therapeutic resistance and tumor initiation. Thus, KSR1 function in SCLC-N serves as a novel model for understanding the role of KSR1-dependent signaling in normal and malignant tissues. These findings shed light on a key distinct protein responsible for regulation in SCLC-N tumors, and a potential subtype specific therapeutic target.

Therapeutic vulnerabilities in triple negative breast cancer: Stem-like traits explored within molecular classification

Triple Negative Breast Cancer (TNBC) is the most aggressive type of breast cancer (BC). Despite advances in the clinical management of TNBC, recurrence-related mortality remains a challenge. The stem-like phenotype of TNBC plays a significant role in the persistence of minimal disease residue after therapy. Individuals exhibiting stem-like characteristics are particularly prone to inducing malignant relapse accompanied by strong resistance. Therefore, stem-like traits have been broadly proposed as therapeutic vulnerabilities to treat TNBC and reduce recurrence. However, heterogeneity within TNBC often generally restricts the stability of the therapeutic efficacy. To understand the heterogeneity and manage TNBC more precisely, multiple TNBC subtyping categories have been reported, providing the basis for profile-according therapeutic regimens. To provide more insight into targeting stem-like traits to ablate TNBC and reduce recurrence in the context of heterogeneity, this paper reviewed the molecular subtyping of TNBC, identified the consensus subtypes with distinct stem-like phenotypes, characterized the stemness hierarchy of TNBC, outlined the biological models for stem-like TNBC subtypes, summarized the therapeutic vulnerabilities in stem-like traits of the subtypes, and proposed potential therapeutic regimens targeting stem-like characteristics to improve TNBC prognosis.

Molecular Changes in Breast Cancer Induced by Radiation Therapy

PURPOSE

Breast cancer treatments are based on prognostic clinicopathologic features that form the basis for therapeutic guidelines. Although the utilization of these guidelines has decreased breast cancer-associated mortality rates over the past three decades, they are not adequate for individualized therapy. Radiation therapy (RT) is the backbone of breast cancer treatment. Although a highly successful therapeutic modality clinically, from a biological perspective, preclinical studies have shown RT to have the potential to alter tumor cell phenotype, immunogenicity, and the surrounding microenvironment, potentially changing the behavior of cancer cells and resulting in a significant variation in RT response. This review presents the recent advances in revealing the complex molecular changes induced by RT in the treatment of breast cancer and highlights the complexities of translating this information into clinically relevant tools for improved prognostic insights and the revelation of novel approaches for optimizing RT.

METHODS AND MATERIALS

Current literature was reviewed with a focus on recent advances made in the elucidation of tumor-associated radiation-induced molecular changes across molecular, genetic, and proteomic bases. This review was structured with the aim of providing an up-to-date overview over the very broad and complex subject matter of radiation-induced molecular changes and radioresistance, familiarizing the reader with the broader issue at hand.

RESULTS

The subject of radiation-induced molecular changes in breast cancer has been broached from various physiological focal points including that of the immune system, immunogenicity and the abscopal effect, tumor hypoxia, breast cancer classification and subtyping, molecular heterogeneity, and molecular plasticity. It is becoming increasingly apparent that breast cancer clinical subtyping alone does not adequately account for variation in RT response or radioresistance. Multiple components of the tumor microenvironment and immune system, delivered RT dose and fractionation schedules, radiation-induced bystander effects, and intrinsic tumor physiology and heterogeneity all contribute to the resultant RT outcome.

CONCLUSIONS

Despite recent advances and improvements in anticancer therapies, tumor resistance remains a significant challenge. As new analytical techniques and technologies continue to provide crucial insight into the complex molecular mechanisms of breast cancer and its treatment responses, it is becoming more evident that personalized anticancer treatment regimens may be vital in overcoming radioresistance.

Long Non-Coding RNAs as Regulators for Targeting Breast Cancer Stem Cells and Tumor Immune Microenvironment: Biological Properties and Therapeutic Potential

Breast cancer stem cells (BCSCs) is a subpopulation of cancer cells with self-renewal and differentiation capacity, have been suggested to give rise to tumor heterogeneity and biologically aggressive behavior. Accumulating evidence has shown that BCSCs play a fundamental role in tumorigenesis, progression, and recurrence. The development of immunotherapy, primarily represented by programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) inhibitors, has greatly changed the treatment landscape of multiple malignancies. Recent studies have identified pervasive negative associations between cancer stemness and anticancer immunity. Stemness seems to play a causative role in the formation of cold tumor immune microenvironment (TIME). The multiple functions of long non-coding RNAs (lncRNAs) in regulating stemness and immune responses has been recently highlighted in breast cancer. The review focus on lncRNAs and keys pathways involved in the regulation of BCSCs and TIME. Potential clinical applications using lncRNAs as biomarkers or therapies will be discussed.

microRNA-944 inhibits breast cancer cell proliferation and promotes cell apoptosis by reducing SPP1 through inactivating the PI3K/Akt pathway

Breast cancer is a common malignancy in women with poor prognosis. This study aimed to investigate the molecular mechanism of microRNA-944 (miR-944) mediated secreted phosphoprotein-1 (SPP1) in breast cancer progression and its regulatory effect on the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway. Differential gene analysis was performed to identify key genes associated with breast cancer development by screening breast cancer-related microarray data. The expression of miR-944 and SPP1 and their relationship were determined in clinical samples and cells. sh-SPP1, oe-SPP1, LY294002 or miR-944 mimic were transfected into MCF-7 cells to investigate the role of miR-944 mediated SPP1 in breast cancer development and its regulatory effect on the PI3K/Akt pathway. Finally, the tumorigenicity of breast cancer cells was observed in nude mice. Through bioinformatics analysis, we identified SPP1 as a key gene in breast cancer, and miR-944 as an upstream miRNA of SPP1. In breast cancer tissues and cells, the expression of miR-944 was decreased while that of SPP1 was increased. miR-944 negatively regulated the expression of SPP1. In breast cancer cells, SPP1 activated the PI3K/Akt pathway to promote cell proliferation and inhibit apoptosis. In vitro cell experiments showed that the downregulation of miR-944 promoted the high expression of SPP1, which then activated the PI3K/Akt signaling pathway, promoting breast cancer cell proliferation. In vivo experiments further confirmed the anti-cancer role of miR-944 mediated SPP1 in breast cancer. Our study highlights the role of miR-944 mediated SPP1 in inhibiting breast cancer progression by blocking the PI3K/Akt pathway.

Small molecule inhibition of TFF3 overcomes tamoxifen resistance and enhances taxane efficacy in ER+ mammary carcinoma

Even though tamoxifen has significantly improved the survival of estrogen receptor positive (ER+) mammary carcinoma (MC) patients, the development of drug resistance with consequent disease recurrence has limited its therapeutic efficacy. Trefoil factor-3 (TFF3) has been previously reported to mediate anti-estrogen resistance in ER+MC. Herein, the efficacy of a small molecule inhibitor of TFF3 (AMPC) in enhancing sensitivity and mitigating acquired resistance to tamoxifen in ER+MC cells was investigated. AMPC induced apoptosis of tamoxifen-sensitive and resistant ER+MC cells and significantly reduced cell survival in 2D and 3D culture in vitro. In addition, AMPC reduced cancer stem cell (CSC)-like behavior in ER+MC cells in a BCL2-dependent manner. Synergistic effects of AMPC and tamoxifen were demonstrated in ER+MC cells and AMPC was observed to improve tamoxifen efficacy in tamoxifen-sensitive cells and to re-sensitize cells to tamoxifen in tamoxifen-resistant ER+MC in vitro and in vivo. Additionally, tamoxifen-resistant ER+MC cells were concomitantly resistant to anthracycline, platinum and fluoropyrimidine drugs, but not to Taxanes. Taxane treatment of tamoxifen-sensitive and resistant ER+MC cells increased TFF3 expression indicating a combination vulnerability for tamoxifen-resistant ER+MC cells. Taxanes increased CSC-like behavior of tamoxifen-sensitive and resistant ER+MC cells which was reduced by AMPC treatment. Taxanes synergized with AMPC to promote apoptosis and reduce CSC-like behavior in vitro and in vivo. Hence, AMPC restored the sensitivity of tamoxifen and enhanced the efficacy of Taxanes in tamoxifen-resistant ER+MC. In conclusion, pharmacological inhibition of TFF3 may serve as an effective combinatorial therapeutic strategy for the treatment of tamoxifen-resistant ER+MC.

Natural products derived from medicinal plants and microbes might act as a game-changer in breast cancer: a comprehensive review of preclinical and clinical studies

Breast cancer (BC) is the most prevalent neoplasm among women. Genetic and environmental factors lead to BC development and on this basis, several preventive - screening and therapeutic interventions have been developed. Hormones, both in the form of endogenous hormonal signaling or hormonal contraceptives, play an important role in BC pathogenesis and progression. On top of these, breast microbiota includes both species with an immunomodulatory activity enhancing the host's response against cancer cells and species producing proinflammatory cytokines associated with BC development. Identification of novel multitargeted therapeutic agents with poly-pharmacological potential is a dire need to combat advanced and metastatic BC. A growing body of research has emphasized the potential of natural compounds derived from medicinal plants and microbial species as complementary BC treatment regimens, including dietary supplements and probiotics. In particular, extracts from plants such as Artemisia monosperma Delile, Origanum dayi Post, Urtica membranacea Poir. ex Savigny, Krameria lappacea (Dombey) Burdet & B.B. Simpson and metabolites extracted from microbes such as Deinococcus radiodurans and Streptomycetes strains as well as probiotics like Bacillus coagulans and Lactobacillus brevis MK05 have exhibited antitumor effects in the form of antiproliferative and cytotoxic activity, increase in tumors' chemosensitivity, antioxidant activity and modulation of BC - associated molecular pathways. Further, bioactive compounds like 3,3'-diindolylmethane, epigallocatechin gallate, genistein, rutin, resveratrol, lycopene, sulforaphane, silibinin, rosmarinic acid, and shikonin are of special interest for the researchers and clinicians because these natural agents have multimodal action and act via multiple ways in managing the BC and most of these agents are regularly available in our food and fruit diets. Evidence from clinical trials suggests that such products had major potential in enhancing the effectiveness of conventional antitumor agents and decreasing their side effects. We here provide a comprehensive review of the therapeutic effects and mechanistic underpinnings of medicinal plants and microbial metabolites in BC management. The future perspectives on the translation of these findings to the personalized treatment of BC are provided and discussed.

Targeting mitochondrial dynamics by AZD5363 in triple-negative breast cancer MDA-MB-231 cell-derived spheres

Breast cancer stem cells (BCSCs) have been suggested to contribute to chemotherapeutic resistance and disease relapse in breast cancer. Thus, BCSCs represent a promising target in developing novel breast cancer treatment strategies. Mitochondrial dynamics in BCSCs were recently highlighted as an available approach for targeting BCSCs. In this study, a three-dimensional (3D) cultured breast cancer stem cell spheres model was constructed. Mitochondrial dynamics and functions were analyzed by flow cytometry and confocal microscopy. We have demonstrated that the protein levels of FIS 1 and Mitofusin 1 were significantly increased in BCSCs. Moreover, Capivasertib (AZD5363) administration could suppress Mitofusin1 expression in BCSCs. Our use of MitoTracker Orange and annexin V double-staining assay suggested that AZD5363 could induce apoptosis in BCSCs. The sensitivity of stem cell spheres to doxorubicin was investigated by CCK8 assay, and our results indicated that AZD5363 could re-sensitize BCSCs to Doxo. Flow cytometry analysis identified doxo-induced CD44 and CD133 expression in BCSCs could be suppressed by AZD5363. In combination with AZD536, doxo-induced apoptosis in the BCSCs was significantly increased. In conclusion, our study explored, for the first time, that AZD5363 could target mitochondrial dynamics in 3D cultured stem cell spheres (BCSCs) by regulating Mitofusin.

Periostin drives extracellular matrix degradation, stemness, and chemoresistance by activating the MAPK/ERK signaling pathway in triple-negative breast cancer cells

BACKGROUND

Adipose tissue, which is mainly composed of adipocytes, is a crucial component of the tumor microenvironment, particularly in breast cancer. Adipocytes surround breast cancer cells and may participate in cell‒cell interactions in the breast microenvironment. However, little is currently known about how adipocytes influence the biological behavior of the surrounding breast cancer cells. Hence, this study sought to investigate the role and underlying mechanisms of periostin in triple-negative breast cancer (TNBC) cells cocultured with adipogenic conditioned medium (ACM) and palmitic acid (PA).

METHODS

Human TNBC cell lines (MDA‒MB‒231 and SUM159PT) were treated with ACM and PA, then the expression of periostin, matrix metalloproteinases (MMPs) and stemness-related molecules were assessed by Western blotting and RT‒qPCR. The cellular viability was assessed using CCK‒8 assay. Plasmid transfection, RNA sequencing, and pathway inhibitor were used to explore the specific mechanisms of periostin.

RESULTS

ACM and PA elevated the expression of both MMPs and stemness-related molecules in TNBCs. MMPs can promote tumor cell infiltration and migration by degrading the extracellular matrix, and stemness expression increases the development of tumor chemoresistance. Additionally, ACM and PA increased periostin expression, while inhibiting periostin disrupted the involvement of ACM and PA in promoting extracellular matrix degradation, stemness, and chemoresistance in TNBCs. Furthermore, this study found that periostin promoted TNBC progression by activating the MAPK/ERK signaling pathway and that inhibition of MAPK/ERK signaling reduced the phenotype caused by periostin upregulation in TNBCs treated with ACM or PA. Finally, the present results showed that the high expression of POSTN, which encodes periostin, was substantially related to worse survival in TNBC patients.

CONCLUSIONS

The results of the study elucidated for the first time how periostin is the key protein secreted in TNBCs in response to the adipocyte-regulated tumor microenvironment, while periostin-neutralizing antibodies may serve as potential therapeutic agents in relation to TNBC progression.

CircNCOR1 regulates breast cancer radiotherapy efficacy by regulating CDK2 via hsa-miR-638 binding

BACKGROUND

Despite aggressive local and regional therapy, triple-negative breast cancer (TNBC) is characterized by an increased risk of locoregional recurrence. RNA-sequencing data has identified a large number of circRNAs in primary breast cancers, but the role of specific circRNAs in regulating the radiosensitivity of TNBC is not fully understood. This research aimed to investigate the function of circNCOR1 in the radiosensitivity of TNBC.

METHODS

CircRNA high-throughput sequencing was conducted on two breast cancer MDA-MB-231 and BT549 cell lines after 6 Gy radiation. The relationship between circNCOR1, hsa-miR-638, and CDK2 was determined by RNA immunoprecipitation (RIP), FISH and luciferase assays. The proliferation and apoptosis of breast cancer cells were measured by CCK8, flow cytometry, colony formation assays, and western blot.

RESULTS

Differential expression of circRNAs was closely related to the proliferation of breast cancer cells after irradiation. Overexpression of circNCOR1 facilitated the proliferation of MDA-MB-231 and BT549 cells and impaired the radiosensitivity of breast cancer cells. Additionally, circNCOR1 acted as a sponge for hsa-miR-638 to regulate the downstream target protein CDK2. Overexpression of hsa-miR-638 promoted apoptosis of breast cancer cells, while overexpression of CDK2 alleviated apoptosis and increased proliferation and clonogenicity. In vivo, overexpression of circNCOR1 partially reversed radiation-induced loosening of tumor structures and enhanced tumor cell proliferation.

CONCLUSION

Our results demonstrated that circNCOR1 bounds to hsa-miR-638 and targets CDK2, thereby regulating the radiosensitivity of TNBC.

Cuproptosis engages in c-Myc-mediated breast cancer stemness

BACKGROUND

Intra-tumoral heterogeneity (ITH) is a distinguished hallmark of cancer, and cancer stem cells (CSCs) contribute to this malignant characteristic. Therefore, it is of great significance to investigate and even target the regulatory factors driving intra-tumoral stemness. c-Myc is a vital oncogene frequently overexpressed or amplified in various cancer types, including breast cancer. Our previous study indicated its potential association with breast cancer stem cell (BCSC) biomarkers.

METHODS

In this research, we performed immunohistochemical (IHC) staining on sixty breast cancer surgical specimens for c-Myc, CD44, CD24, CD133 and ALDH1A1. Then, we analyzed transcriptomic atlas of 1533 patients with breast cancer from public database.

RESULTS

IHC staining indicated the positive correlation between c-Myc and BCSC phenotype. Then, we used bioinformatic analysis to interrogate transcriptomics data of 1533 breast cancer specimens and identified an intriguing link among c-Myc, cancer stemness and copper-induced cell death (also known as "cuproptosis"). We screened out cuproptosis-related characteristics that predicts poor clinical outcomes and found that the pro-tumoral cuproptosis-based features were putatively enriched in MYC-targets and showed a significantly positive correlation with cancer stemness.

CONCLUSION

In addition to previous reports on its oncogenic roles, c-Myc showed significant correlation to stemness phenotype and copper-induced cell toxicity in breast cancer tissues. Moreover, transcriptomics data demonstrated that pro-tumoral cuproptosis biomarkers had putative positive association with cancer stemness. This research combined clinical samples with large-scale bioinformatic analysis, covered description and deduction, bridged classic oncogenic mechanisms to innovative opportunities, and inspired the development of copper-based nanomaterials in targeting highly heterogeneous tumors.

Changes of Mutations and Copy-Number and Enhanced Cell Migration during Breast Tumorigenesis

Although cancer stem cells (CSCs) play a major role in tumorigenesis and metastasis, the role of genetic alterations in invasiveness of CSCs is still unclear. Tumor microenvironment signals, such as extracellular matrix (ECM) composition, significantly influence cell behaviors. Unfortunately, these signals are often lost in in vitro cell culture. This study determines putative CSC populations, examines genetic changes during tumorigenesis of human breast epithelial stem cells, and investigates single-cell migration properties on ECM-mimetic platforms. Whole exome sequencing data indicate that tumorigenic cells have a higher somatic mutation burden than non-tumorigenic cells, and that mutations exclusive to tumorigenic cells exhibit higher predictive deleterious scores. Tumorigenic cells exhibit distinct somatic copy number variations (CNVs) including gain of duplications in chromosomes 5 and 8. ECM-mimetic topography selectively enhances migration speed of tumorigenic cells, but not of non-tumorigenic cells, and results in a wide distribution of tumorigenic single-cell migration speeds, suggesting heterogeneity in cellular sensing of contact guidance cues. This study identifies mutations and CNVs acquired during breast tumorigenesis, which can be associated with enhanced migration of breast tumorigenic cells, and demonstrates that a nanotopographically-defined platform can be applied to recapitulate an ECM structure for investigating cellular migration in the simulated tumor microenvironment.

Immunotherapy: Review of the Existing Evidence and Challenges in Breast Cancer

Breast cancer (BC) is a representative malignant tumor that affects women across the world, and it is the main cause of cancer-related deaths in women. Although a large number of treatment methods have been developed for BC in recent years, the results are sometimes unsatisfying. In recent years, treatments of BC have been expanded with immunotherapy. In our article, we list some tumor markers related to immunotherapy for BC. Moreover, we introduce the existing relatively mature immunotherapy and the markers' pathogenesis are involved. The combination of immunotherapy and other therapies for BC are introduced in detail, including the combination of immunotherapy and chemotherapy, the combined use of immunosuppressants and chemotherapy drugs, immunotherapy and molecular targeted therapy. We summarize the clinical effects of these methods. In addition, this paper also makes a preliminary exploration of the combination of immunotherapy, radiotherapy, and nanotechnology for BC.

Active Targeting of Versatile Nanocomplex Using the Novel Biomarker of Breast Cancer Stem Cells

Breast cancer in women is one of the most common life-threatening malignancies. Despite of the development for the improved treatment, there are still many limitations to overcome. Among them, cancer stem cells (CSCs) are well known for tumor formation, development, cellular heterogeneity, and cancer recurrence. Therefore, to completely cure breast cancer, treatment of both cancer and CSC is required. To selectively target CSCs, we generated a liposome-based smart nano complex using CEACAM 6 (CD66c) antibody (Ab), a novel cell-surface biomarker of breast-derived CSCs (BCSCs) discovered in our previous research. Selective and increased cellular uptake was observed in BCSCs treated with CD66c Ab-conjugated rhodamine-labeled liposomes (CDRHOL) depending on the expression level of CD66c. CD66c Ab-conjugated doxorubicin (DOX)-loaded liposomes (CDDOXL) selectively showed increased cell killing effects in BCSCs with high CD66c expression levels. In an in vivo animal study, CDRHOL showed enhanced accumulation in xenografted BCSC tumors with low delivery into non-target organs. Moreover, mice treated with CDDOXL have assessed the decreased induction ability of immune response by low expression levels of pro-inflammatory cytokines and reduced liver toxicity by histopathological analysis. Finally, the improved antitumor effect of CDDOXL was evaluated in a metastatic BCSC mouse model via systemic administration. Collectively, our study is the first to demonstrate that a multi-functional nano complex using a novel surface biomarker of BCSC may be a more effective therapeutic agent for the treatment of cancer and CSCs.

Construction and Validation of a Prognostic Model Based on mRNAsi-Related Genes in Breast Cancer

Background

Breast cancer is a big threat to the women across the world with substantial morbidity and mortality. The pressing matter of our study is to establish a prognostic gene model for breast cancer based on mRNAsi for predicting patient's prognostic survival.

Methods

From The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases, we downloaded the expression profiles of genes in breast cancer. On the basis of one-class logistic regression (OCLR) machine learning algorithm, mRNAsi of samples was calculated. Kaplan-Meier (K-M) and Kruskal-Wallis (K-W) tests were utilized for the assessment of the connection between mRNAsi and clinicopathological variables of the samples. As for the analysis on the correlation between mRNAsi and immune infiltration, ESTIMATE combined with Spearman test was employed. The weighted gene coexpression network analysis (WGCNA) network was established by utilizing the differentially expressed genes in breast cancer, and the target module with the most significant correlation with mRNAsi was screened. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were conducted to figure out the biological functions of the target module. As for the construction of the prognostic model, univariate, least absolute shrinkage and selection operator (LASSO) and multivariate Cox regression analyses were performed on genes in the module. The single sample gene set enrichment analysis (ssGSEA) and tumor mutational burden were employed for the analysis on immune infiltration and gene mutations in the high- and low-risk groups. As for the analysis on whether this model had the prognostic value, the nomogram and calibration curves of risk scores and clinical characteristics were drawn.

Results

Nine mRNAsi-related genes (CFB, MAL2, PSME2, MRPL13, HMGB3, DCTPP1, SHCBP1, SLC35A2, and EVA1B) comprised the prognostic model. According to the results of ssGSEA and gene mutation analysis, differences were shown in immune cell infiltration and gene mutation frequency between the high- and low-risk groups.

Conclusion

Nine mRNAsi-related genes screened in our research can be considered as the biomarkers to predict breast cancer patients' prognoses, and this model has a potential relationship with individual somatic gene mutations and immune regulation. This study can offer new insight into the development of diagnostic and clinical treatment strategies for breast cancer.

Selectively Targeting Breast Cancer Stem Cells by 8-Quinolinol and Niclosamide

Cancer maintenance, metastatic dissemination and drug resistance are sustained by cancer stem cells (CSCs). Triple negative breast cancer (TNBC) is the breast cancer subtype with the highest number of CSCs and the poorest prognosis. Here, we aimed to identify potential drugs targeting CSCs to be further employed in combination with standard chemotherapy in TNBC treatment. The anti-CSC efficacy of up to 17 small drugs was tested in TNBC cell lines using cell viability assays on differentiated cancer cells and CSCs. Then, the effect of 2 selected drugs (8-quinolinol -8Q- and niclosamide -NCS-) in the cancer stemness features were evaluated using mammosphere growth, cell invasion, migration and anchorage-independent growth assays. Changes in the expression of stemness genes after 8Q or NCS treatment were also evaluated. Moreover, the potential synergism of 8Q and NCS with PTX on CSC proliferation and stemness-related signaling pathways was evaluated using TNBC cell lines, CSC-reporter sublines, and CSC-enriched mammospheres. Finally, the efficacy of NCS in combination with PTX was analyzed in vivo using an orthotopic mouse model of MDA-MB-231 cells. Among all tested drug candidates, 8Q and NCS showed remarkable specific anti-CSC activity in terms of CSC viability, migration, invasion and anchorage independent growth reduction in vitro. Moreover, specific 8Q/PTX and NCS/PTX ratios at which both drugs displayed a synergistic effect in different TNBC cell lines were identified. The sole use of PTX increased the relative presence of CSCs in TNBC cells, whereas the combination of 8Q and NCS counteracted this pro-CSC activity of PTX while significantly reducing cell viability. In vivo, the combination of NCS with PTX reduced tumor growth and limited the dissemination of the disease by reducing circulating tumor cells and the incidence of lung metastasis. The combination of 8Q and NCS with PTX at established ratios inhibits both the proliferation of differentiated cancer cells and the viability of CSCs, paving the way for more efficacious TNBC treatments.

Long non-coding RNAs affecting cell metabolism in cancer

Metabolic reprogramming is commonly recognized as one important hallmark of cancers. Cancer cells present significant alteration of glucose metabolism, oxidative phosphorylation, and lipid metabolism. Recent findings demonstrated that long non-coding RNAs control cancer development and progression by modulating cell metabolism. Here, we give an overview of breast cancer metabolic reprogramming and the role of long non-coding RNAs in driving cancer-specific metabolic alteration.

Phenazine derivatives attenuate the stemness of breast cancer cells through triggering ferroptosis

Breast cancer stem cells (BCSCs) are positively correlated with the metastasis, chemoresistance, and recurrence of breast cancer. However, there are still no drugs targeting BCSCs in clinical using for breast cancer treatment. Here, we tried to screen out small-molecule compounds targeting BCSCs from the phenazine library established by us before. We focused on the compounds without affecting cell viability and screened out three potential compounds (CPUL119, CPUL129, CPUL149) that can significantly attenuate the stemness of breast cancer cells, as evident by the decrease of stemness marker expression, CD44+/CD24- subpopulation, mammary spheroid-formation ability, and tumor-initiating capacity. Additionally, these compounds suppressed the metastatic ability of breast cancer cells in vitro and in vivo. Combined with the transcriptome sequencing analysis, ferroptosis was shown on the top of the most upregulated pathways by CPUL119, CPUL129, and CPUL149, respectively. Mechanistically, we found that these three compounds could trigger ferroptosis by accumulating and sequestering iron in lysosomes through interacting with iron, and by regulating the expression of proteins (IRP2, TfR1, ferritin) engaged in iron transport and storage. Furthermore, inhibition of ferroptosis rescued the suppression of these three compounds on breast cancer cell stemness. This study suggests that CPUL119, CPUL129, and CPUL149 can specifically inhibit the stemness of breast cancer cells through triggering ferroptosis and may be the potential compounds for breast cancer treatment.

TRG16, targeted by miR-765, inhibits breast cancer stem cell-like properties via regulating the NF-κB pathway

Previous studies reported that cancer stem cells (CSCs) might be responsible for drug resistance and cancer progression. Transformation-Related Gene 16 Protein (TRG16), a pseudokinase, was reported to be a suppressor in some types of cancer and its overexpression impaired hepatocellular carcinoma cell stemness. However, the function of TRG16 in BC remains unclear. We found that TRG16 expression was significantly downregulated in BC tissues compared with adjacent tissues (n = 40; P < 0.001) and BC patients with lower expression of TRG16 had a worse prognosis. Forced expression of TRG16 inhibited BC stem cell-like properties as evidenced by decreased CD44-positive cells (CSC marker), reduced mammosphere quantity, and downregulated Nanog, aldehyde dehydrogenase, octamer-binding transcription factor 4, and SRY-box transcription factor 2 expression (CSC markers). Moreover, TRG16 overexpression inhibited self-renewal and invasion capabilities of BC cells in vitro as well as tumor growth in vivo but increased cisplatin sensitivity. However, TRG16 silencing had the opposite effects. Further mechanistic studies revealed that TRG16 was targeted and negatively regulated by miR-765, a facilitator of BC progression. TRG16 could suppress the activation of the NF-κB pathway in BC cells, which is a positive pathway in BC progression and contributes to the maintenance of cancer cell stemness. In conclusion, the results above demonstrate that TRG16, negatively regulated by miR-765, may inhibit the BC progression by regulating BC stem cell-like properties and this inhibition may be mediated by the NF-κB pathway. Our findings indicate that TRG16 may be a potential therapeutic targetable node for BC. TRG16, negatively regulated by miR-765, may inhibit the BC progression through regulating BC stem cell-like properties and this inhibition may be mediated by the NF-κB pathway.

Overexpression of MCAM induced by SMYD2-H3K36me2 in breast cancer stem cell properties

BACKGROUND

Melanoma cell adhesion molecule (MCAM) is highly expressed in various malignancies. However, studies on the effects of MCAM on stemness of cancer stem cells are limited. Here, we aimed to explore the relationship between MCAM and stem cell phenotype in breast cancer (BC).

METHODS

We analyzed the genes differentially expressed in BC from the oncomine database, followed by TCGA-BRCA database validation. We then used gene set enrichment analysis to analyze the signaling pathways enriched to the relevant genes, followed by loss-of-function experiments to analyze the role of MCAM in the growth of BC cells and the maintenance of stem cell properties. We analyzed the cause for the MCAM overexpression using ChIP-seq and clarified the upstream mechanism by constructing SE-Deleted cells. Finally, the role of SMYD2 in the growth of BC cells and the maintenance of stem cell properties were verified by rescue experiments.

RESULTS

MCAM was significantly overexpressed in BC, which predicted somber prognosis in patients. Knockdown of MCAM drastically hindered the growth and metastasis of BC cells in vitro and in vivo. Subsequently, the MCAM promoter was observed to have significant H3K36me2 modification and that SMYD2 could significantly promote the expression of MCAM. In addition, further overexpression of SMYD2 in cells with MCAM knockdown increased MCAM expression and promoted the growth as well as stemness of BC cells.

CONCLUSION

SMYD2 can elevate the expression of MCAM by promoting its H3K36me2 modification, which in turn expedites the growth and stem cell properties of BC cells.

Breast Cancer Stem Cell Membrane Biomarkers: Therapy Targeting and Clinical Implications

Breast cancer is the most common malignancy affecting women worldwide. Importantly, there have been significant improvements in prevention, early diagnosis, and treatment options, which resulted in a significant decrease in breast cancer mortality rates. Nevertheless, the high rates of incidence combined with therapy resistance result in cancer relapse and metastasis, which still contributes to unacceptably high mortality of breast cancer patients. In this context, a small subpopulation of highly tumourigenic cancer cells within the tumour bulk, commonly designated as breast cancer stem cells (BCSCs), have been suggested as key elements in therapy resistance, which are responsible for breast cancer relapses and distant metastasis. Thus, improvements in BCSC-targeting therapies are crucial to tackling the metastatic progression and might allow therapy resistance to be overcome. However, the design of effective and specific BCSC-targeting therapies has been challenging since there is a lack of specific biomarkers for BCSCs, and the most common clinical approaches are designed for commonly altered BCSCs signalling pathways. Therefore, the search for a new class of BCSC biomarkers, such as the expression of membrane proteins with cancer stem cell potential, is an area of clinical relevance, once membrane proteins are accessible on the cell surface and easily recognized by specific antibodies. Here, we discuss the significance of BCSC membrane biomarkers as potential prognostic and therapeutic targets, reviewing the CSC-targeting therapies under clinical trials for breast cancer.

Abnormal lipid synthesis as a therapeutic target for cancer stem cells

Cancer stem cells (CSCs) comprise a subpopulation of cancer cells with stem cell properties, which exhibit the characteristics of high tumorigenicity, self-renewal, and tumor initiation and are associated with the occurrence, metastasis, therapy resistance, and relapse of cancer. Compared with differentiated cells, CSCs have unique metabolic characteristics, and metabolic reprogramming contributes to the self-renewal and maintenance of stem cells. It has been reported that CSCs are highly dependent on lipid metabolism to maintain stemness and satisfy the requirements of biosynthesis and energy metabolism. In this review, we demonstrate that lipid anabolism alterations promote the survival of CSCs, including de novo lipogenesis, lipid desaturation, and cholesterol synthesis. In addition, we also emphasize the molecular mechanism underlying the relationship between lipid synthesis and stem cell survival, the signal trans-duction pathways involved, and the application prospect of lipid synthesis reprogramming in CSC therapy. It is demonstrated that the dependence on lipid synthesis makes targeting of lipid synthesis metabolism a promising therapeutic strategy for eliminating CSCs. Targeting key molecules in lipid synthesis will play an important role in anti-CSC therapy.

Targeting the metabolism of cancer stem cells by energy disruptor molecules

Cancer stem cells (CSCs) have been identified in various tumor types. CSCs are believed to contribute to tumor metastasis and resistance to conventional therapy. So targeting these cells could be an effective strategy to eliminate tumors and a promising new type of cancer treatment. Alterations in metabolism play an essential role in CSC biology and their resistance to treatment. The metabolic properties pathways in CSCs are different from normal cells, and to some extent, are different from regular tumor cells. Interestingly, CSCs can use other nutrients for their metabolism and growth. The different metabolism causes increased sensitivity of CSCs to agents that disrupt cellular homeostasis. Compounds that interfere with the central metabolic pathways are known as energy disruptors and can reduce CSC survival. This review highlights the differences between regular cancer cells and CSC metabolism and discusses the action mechanisms of energy disruptors at the cellular and molecular levels.

Metal complexes against breast cancer stem cells

With the highest incidence, breast cancer is the leading cause of cancer deaths among women in the world. Tumor metastasis is the major contributor of high mortality in breast cancer, and the existence of cancer stem cells (CSCs) has been proven to be the cause of tumor metastasis. CSCs are a small proportion of tumor cells, and they are associated with self-renewal and tumorigenic potential. Given the significance of CSCs in tumor initiation, expansion, relapse, resistance, and metastasis, studies should investigate and discover effective anticancer agents that can not only inhibit the proliferation of differentiated tumor cells but also reduce the tumorigenic capability of CSCs. Thus, new therapies must be discovered to treat and prevent this severely hazardous disease of human beings. The success of platinum complexes in cancer treatment has laid the basic foundation for the utilization of metal complexes in the treatment of malignant cancers, in particular the highly aggressive triple-negative breast cancer. Importantly, metal complexes currently have diverse and versatile competences in the therapeutic targeting of CSCs. The anti-CSC properties provide a strong impetus for the development of novel metal-based compounds for the targeting of CSCs and treatment of chemotherapy-resistant and relapsed tumors. In this review, we provide the latest advances in metal complexes including platinum, ruthenium, osmium, iridium, manganese, cobalt, nickel, copper, zinc, palladium, and tin complexes against breast CSCs obtained over the past decade, with pertinent literature including those published until 2021.

Analyzing mRNAsi-Related Genes Identifies Novel Prognostic Markers and Potential Drug Combination for Patients with Basal Breast Cancer

Basal breast cancer subtype is the worst prognosis subtypes among all breast cancer subtypes. Recently, a new tumor stemness index-mRNAsi is found to be able to measure the degree of oncogenic differentiation of tissues. The mRNAsi involved in a variety of cancer processes is derived from the innovative application of one-class logistic regression (OCLR) machine learning algorithm to the whole genome expression of various stem cells and tumor cells. However, it is largely unknown about mRNAsi in basal breast cancer. Here, we find that basal breast cancer carries the highest mRNAsi among all four subtypes of breast cancer, especially 385 mRNAsi-related genes are positively related to the high mRNAsi value in basal breast cancer. This high mRNAsi is also closely related to active cell cycle, DNA replication, and metabolic reprogramming in basal breast cancer. Intriguingly, in the 385 genes, TRIM59, SEPT3, RAD51AP1, and EXO1 can act as independent protective prognostic factors, but CTSF and ABHD4B can serve as independent bad prognostic factors in patients with basal breast cancer. Remarkably, we establish a robust prognostic model containing the 6 mRNAsi-related genes that can effectively predict the survival rate of patients with the basal breast cancer subtype. Finally, the drug sensitivity analysis reveals that some drug combinations may be effectively against basal breast cancer via targeting the mRNAsi-related genes. Taken together, our study not only identifies novel prognostic biomarkers for basal breast cancers but also provides the drug sensitivity data by establishing an mRNAsi-related prognostic model.

Aldehyde dehydrogenase 1 (ALDH1) immunostaining in axillary lymph node metastases is an independent prognostic factor in ALDH1-positive breast cancer

Objective

To determine whether aldehyde dehydrogenase 1 (ALDH1) immunostaining in axillary lymph node metastases in patients with breast cancer is associated with poor clinical prognosis.

Methods

This retrospective study reviewed data from the medical records of patients with immunohistochemistry-confirmed invasive ductal carcinoma (IDC) and 1–3 metastatic lymph nodes in the ipsilateral axilla between December 2012 and July 2015. The association between ALDH1 immunostaining in axillary lymph node metastases and clinical parameters and prognosis was analysed using χ²-test, Kaplan–Meier survival analysis, univariate and multivariate Cox regression analyses.

Results

A total of 229 patients with IDC were enrolled in the study. The median follow-up was 61 months (range, 20–89 months). Patients with ALDH1-positive axillary lymph node metastases had significantly shorter relapse-free survival and overall survival compared with those with ALDH1-negative axillary lymph node metastases. ALDH1 immunostaining in axillary lymph node metastases was a significant predictor of poor prognosis in univariate and multivariate analyses.

Conclusion

This large study with long-term follow-up suggests that ALDH1 immunostaining in axillary lymph node metastases is an independent predictor of poor prognosis in patients with breast cancer. The clinical relevance of this finding should be confirmed in further well-designed prospective studies.

Mineralized and GSH-responsive hyaluronic acid based nano-carriers for potentiating repressive effects of sulforaphane on breast cancer stem cells-like properties

Breast cancer stem cell (BCSC) properties are correlated with the malignancy of tumor cells. Sulforaphane (SFN), a natural isothiocyanate, has anti-cancer effects. However, SFN is an oil-like, hydrophobic and unstable substance. To enhance the inhibitory effect of SFN on BCSC-like properties, the mineralized hyaluronic acid-SS-tetradecyl nano-carriers (M-HA-SS-TA) were prepared. The nano-carriers possessed high SFN entrapment rate (92.36%) and drug-loading efficiency (33.64%). The carriers were responsive to the high reducing and mild acidic tumor micro-environment, leading to rapid SFN releasing from SFN-loaded nano-drug (SFN/M-HA-SS-TA). Through the specific recognition of breast cancer cells bearing CD44+ by HA, M-HA-SS-TA nano-carriers showed excellent tumor-targeting ability. Moreover, compared with free SFN, SFN/M-HA-SS-TA showed much stronger inhibition on the BCSC-like properties (invasiveness, self-renewal and tumor growth) both in vitro and in vivo. Together, these results suggested M-HA-SS-TA nano-carriers were promising platforms for tumor-targeted delivery of SFN, enhancing the therapeutic efficacy against BCSC-like properties by SFN.

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.

Wnt/β-Catenin Inhibition Disrupts Carboplatin Resistance in Isogenic Models of Triple-Negative Breast Cancer

Triple-Negative Breast Cancer (TNBC) is the most aggressive breast cancer subtype, characterized by limited treatment options and higher relapse rates than hormone-receptor-positive breast cancers. Chemotherapy remains the mainstay treatment for TNBC, and platinum salts have been explored as a therapeutic alternative in neo-adjuvant and metastatic settings. However, primary and acquired resistance to chemotherapy in general and platinum-based regimens specifically strongly hampers TNBC management. In this study, we used carboplatin-resistant in vivo patient-derived xenograft and isogenic TNBC cell-line models and detected enhanced Wnt/β-catenin activity correlating with an induced expression of stem cell markers in both resistant models. In accordance, the activation of canonical Wnt signaling in parental TNBC cell lines increases stem cell markers' expression, formation of tumorspheres and promotes carboplatin resistance. Finally, we prove that Wnt signaling inhibition resensitizes resistant models to carboplatin both in vitro and in vivo, suggesting the synergistic use of Wnt inhibitors and carboplatin as a therapeutic option in TNBC. Here we provide evidence for a prominent role of Wnt signaling in mediating resistance to carboplatin, and we establish that combinatorial targeting of Wnt signaling overcomes carboplatin resistance enhancing chemotherapeutic drug efficacy.

Chemoresistance and Metastasis in Breast Cancer Molecular Mechanisms and Novel Clinical Strategies

Breast cancer is the most common malignant tumor in females worldwide. Chemotherapy is the standard breast cancer treatment; however, chemoresistance is often seen in patients with metastatic breast cancer. Owing to high heterogeneity, the mechanisms of breast cancer chemoresistance and metastasis have not been fully investigated. The possible molecular mechanisms of chemoresistance in breast cancer include efflux transporters, signaling pathways, non-coding RNAs, and cancer stem cells. However, to overcome this hurdle, the use of novel clinical strategies such as drug carriers, immunotherapy, and autophagy regulation, are being investigated. The goal of this review is to summarize the current data about the molecular mechanisms of breast cancer chemoresistance and the novel clinical strategies; thus, providing a useful clinical tool to explore optimal treatment for breast cancer.

miR-145-5p as a predictive biomarker for breast cancer stemness by computational clinical investigation

BACKGROUND

Breast tumors enriched with breast cancer stem cells (BCSCs), play a crucial role in metastasis and tumor relapse. Hence, targeting BCSCs may lead to efficacious breast cancer therapy. BCSCs have a unique expression of stemness markers, including Nanog, POU5F1, SOX2, and CD44, which play a vital role in cancer stem cell properties. However, the regulation of microRNAs (miRNAs)-mediated cancer stem cell marker expressions is largely unclear.

METHODS

MIENTURNET was used to predict miRNA-target interactions. miR-TV, UALCAN and GEPIA databases were used to analyze the expression of miR-145-5p and SOX2. Survival analysis was obtained by cBioportal, KM plotter and Breast Cancer Gene-Expression Miner. RNAComposer was used to perform miRNA-mRNA duplex prediction. In vitro mRNA and miRNA analysis was performed by qRT-PCR.

RESULTS

It was observed that miR-145-5p was the common miRNA targeting stemness markers. miR-145-5p expression was found to be lower in breast cancer patients compared to healthy subjects. Based on survival analysis, low expression of miR-145-5p and high expression of SOX2 led to a poor overall survival rate in breast cancer patients. Pathway enrichment analysis indicated that SOX2 was highly enriched with transcription factors. Moreover, SOX2 expression level was also upregulated in axillary metastatic lymph nodules. Further, in vitro ectopic expression of miR-145-5p by its mimic downregulated the SOX2 expression compared to the control mimic. Overall, SOX2 was a direct target for miR-145-5p as per the binding and minimal-free energy.

CONCLUSIONS

In this study, miR-145-5p targeting SOX2 was identified as a potential predictive biomarker for breast cancer stemness.

Lactate Dehydrogenase-A (LDH-A) Preserves Cancer Stemness and Recruitment of Tumor-Associated Macrophages to Promote Breast Cancer Progression

Increasing evidence reveals that breast cancer stem cells (BCSCs) subtypes with distinct properties are regulated by their abnormal metabolic changes; however, the specific molecular mechanism and its relationship with tumor microenvironment (TME) are not clear. In this study, we explored the mechanism of lactate dehydrogenase A (LDHA), a crucial glycolytic enzyme, in maintaining cancer stemness and BCSCs plasticity, and promoting the interaction of BCSCs with tumor associated macrophages (TAMs). Firstly, the expression of LDHA in breast cancer tissues was much higher than that in adjacent tissues and correlated with the clinical progression and prognosis of breast cancer patients based on The Cancer Genome Atlas (TCGA) data set. Moreover, the orthotopic tumor growth and pulmonary metastasis were remarkable inhibited in mice inoculated with 4T1-shLdha cells. Secondly, the properties of cancer stemness were significantly suppressed in MDA-MB-231-shLDHA or A549-shLDHA cancer cells, including the decrease of ALDH⁺ cells proportion, the repression of sphere formation and cellular migration, and the reduction of stemness genes (SOX2, OCT4, and NANOG) expression. However, the proportion of ALDH⁺ cells (epithelial-like BCSCs, E-BCSCs) was increased and the proportion of CD44⁺ CD24^- cells (mesenchyme-like BCSCs, M-BCSCs) was decreased after LDHA silencing, suggesting a regulatory role of LDHA in E-BCSCs/M-BCSCs transformation in mouse breast cancer cells. Thirdly, the expression of epithelial marker E-cadherin, proved to interact with LDHA, was obviously increased in LDHA-silencing cancer cells. The recruitment of TAMs and the secretion of CCL2 were dramatically reduced after LDHA was knocked down in vitro and in vivo. Taken together, LDHA mediates a vicious cycle of mutual promotion between BCSCs plasticity and TAMs infiltration, which may provide an effective treatment strategy by targeting LDHA for breast cancer patients.

3D Multicellular Stem-Like Human Breast Tumor Spheroids Enhance Tumorigenicity of Orthotopic Xenografts in Athymic Nude Rat Model

Simple Summary

Breast cancer presents a unique clinical problem because of the variety of cellular subtypes present, including cancer stem cells (CSCs). Breast CSCs can induce the formation of new blood vessels at the site of tumor growth and a develop metastatic phenotype by enhancing a stromal cell response, similar to that of the primary breast cancer. The aim of this study was to investigate breast cancer cells cultured in stromal stem cell factor-supplemented media to generate 3D spheroids that exhibit increased stem-like properties. These 3D stem-like spheroids reproducibly and efficiently established orthotopic breast cancer xenografts in the athymic nude rat. This approach enables a means to develop orthotopic tumors with a stem-like phenotype in a larger athymic rat rodent model of human breast cancer.

Abstract

Therapeutic targeting of stem cells needs to be strategically developed to control tumor growth and prevent metastatic burden successfully. Breast cancer presents a unique clinical problem because of the variety of cellular subtypes present, including cancer stem cells (CSCs). The development of 3D stem-like properties of human breast tumor spheroids in stem cell factor conditioned media was investigated in orthotopic xenografts for enhanced tumorgenicity in the athymic nude rat model. MCF-7, ZR-75-1, and MDA-MB-231 breast cancer cell lines were cultured in serum-free, stem cell factor-supplemented medium under non-adherent conditions and passaged to generate 3rd generation spheroids. The spheroids were co-cultured with fetal lung fibroblast (FLF) cells before orthotopic heterotransplantation into the mammary fat pads of athymic nude rats. Excised xenografts were assessed histologically by H&E staining and immunohistochemistry for breast cancer marker (ERB1), proliferation marker (Ki67), mitotic marker (pHH3), hypoxia marker (HIF-2α), CSC markers (CD47, CD44, CD24, and CD133), and vascularization markers (CD31, CD34). Breast cancer cells cultured in stem cell factor supplemented medium generated 3D spheroids exhibited increased stem-like characteristics. The 3D stem-like spheroids co-cultured with FLF as supporting stroma reproducibly and efficiently established orthotopic breast cancer xenografts in the athymic nude rat.

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.

Drug Resistance in Metastatic Breast Cancer: Tumor Targeted Nanomedicine to the Rescue

Breast cancer, specifically metastatic breast, is a leading cause of morbidity and mortality in women. This is mainly due to relapse and reoccurrence of tumor. The primary reason for cancer relapse is the development of multidrug resistance (MDR) hampering the treatment and prognosis. MDR can occur due to a multitude of molecular events, including increased expression of efflux transporters such as P-gp, BCRP, or MRP1; epithelial to mesenchymal transition; and resistance development in breast cancer stem cells. Excessive dose dumping in chemotherapy can cause intrinsic anti-cancer MDR to appear prior to chemotherapy and after the treatment. Hence, novel targeted nanomedicines encapsulating chemotherapeutics and gene therapy products may assist to overcome cancer drug resistance. Targeted nanomedicines offer innovative strategies to overcome the limitations of conventional chemotherapy while permitting enhanced selectivity to cancer cells. Targeted nanotheranostics permit targeted drug release, precise breast cancer diagnosis, and importantly, the ability to overcome MDR. The article discusses various nanomedicines designed to selectively target breast cancer, triple negative breast cancer, and breast cancer stem cells. In addition, the review discusses recent approaches, including combination nanoparticles (NPs), theranostic NPs, and stimuli sensitive or “smart” NPs. Recent innovations in microRNA NPs and personalized medicine NPs are also discussed. Future perspective research for complex targeted and multi-stage responsive nanomedicines for metastatic breast cancer is discussed.

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.

Apatinib Inhibits Stem Properties and Malignant Biological Behaviors of Breast Cancer Stem Cells by Blocking Wnt/β-catenin Signal Pathway Through Down-regulating LncRNA ROR

BACKGROUND

Cancer stem cells could influence tumor recurrence and metastasis.

OBJECTIVE

To develop a new effective treatment modality targeting breast cancer stem cells (BCSCs), and to explore the role of Apatinib in BCSCs.

METHODS

BCSCs were isolated from MDA-MB-231 cells by immune magnetic beads method. BCSCs were treated with Apatinib, lentiviral plasmids (lncRNA ROR) and iCRT-3 (Wnt pathway inhibitors). Viability, colony numbers, sphere numbers, apoptosis, migration, invasion of BCSCs were detected by MTT, colony formation, tumor sphere, flow cytometry, wound-healing, transwell assays, respectively. The expressions of markers (ABCG2, CD44, CD90, and CD24), epithelial-mesenchymal transition (EMT)-related molecules (E-cadherin, N-cadherin, Vimentin, MMP-2, MMP-9), and Wnt/β-catenin pathway-related proteins (Wnt3a, Wnt5a, β-catenin) in breast cancer stem cells were determined by performing Western blot and qRT-PCR analysis.

RESULTS

Apatinib decreased the viability and colony numbers of BCSCs in a concentration-dependent manner, and it also reduced sphere numbers, suppressed migration, invasion and lncRNA ROR expression, and induced apoptosis of BCSCs. However, these results were partially reversed by lncRNA ROR overexpression. Apatinib suppressed stem property, EMT process and Wnt/β-catenin pathway in BCSCs, which was partially reversed by lncRNA ROR overexpression. Moreover, lncRNA ROR overexpression increased the colony and sphere numbers, and promoted the cell viability, apoptosis inhibition, migration and invasion of BCSCs, but these effects were partially reversed by iCRT-3. LncRNA ROR overexpression increased the stem property, EMT process and Wnt/β-catenin pathway, which were partially counteracted by iCRT-3.

CONCLUSION

Apatinib inhibited stem property and malignant biological behaviors of BCSCs by blocking Wnt/β-catenin signal pathway through down-regulating lncRNA ROR.

Hypoxia-Driven Effects in Cancer: Characterization, Mechanisms, and Therapeutic Implications

Hypoxia, a common feature of solid tumors, greatly hinders the efficacy of conventional cancer treatments such as chemo-, radio-, and immunotherapy. The depletion of oxygen in proliferating and advanced tumors causes an array of genetic, transcriptional, and metabolic adaptations that promote survival, metastasis, and a clinically malignant phenotype. At the nexus of these interconnected pathways are hypoxia-inducible factors (HIFs) which orchestrate transcriptional responses under hypoxia. The following review summarizes current literature regarding effects of hypoxia on DNA repair, metastasis, epithelial-to-mesenchymal transition, the cancer stem cell phenotype, and therapy resistance. We also discuss mechanisms and pathways, such as HIF signaling, mitochondrial dynamics, exosomes, and the unfolded protein response, that contribute to hypoxia-induced phenotypic changes. Finally, novel therapeutics that target the hypoxic tumor microenvironment or interfere with hypoxia-induced pathways are reviewed.

MicroRNA-34a: Potent Tumor Suppressor, Cancer Stem Cell Inhibitor, and Potential Anticancer Therapeutic

Overwhelming evidence indicates that virtually all treatment-naive tumors contain a subpopulation of cancer cells that possess some stem cell traits and properties and are operationally defined as cancer cell stem cells (CSCs). CSCs manifest inherent heterogeneity in that they may exist in an epithelial and proliferative state or a mesenchymal non-proliferative and invasive state. Spontaneous tumor progression, therapeutic treatments, and (epi)genetic mutations may also induce plasticity in non-CSCs and reprogram them into stem-like cancer cells. Intrinsic cancer cell heterogeneity and induced cancer cell plasticity, constantly and dynamically, generate a pool of CSC subpopulations with varying levels of epigenomic stability and stemness. Despite the dynamic and transient nature of CSCs, they play fundamental roles in mediating therapy resistance and tumor relapse. It is now clear that the stemness of CSCs is coordinately regulated by genetic factors and epigenetic mechanisms. Here, in this perspective, we first provide a brief updated overview of CSCs. We then focus on microRNA-34a (miR-34a), a tumor-suppressive microRNA (miRNA) devoid in many CSCs and advanced tumors. Being a member of the miR-34 family, miR-34a was identified as a p53 target in 2007. It is a bona fide tumor suppressor, and its expression is dysregulated and downregulated in various human cancers. By targeting stemness factors such as NOTCH, MYC, BCL-2, and CD44, miR-34a epigenetically and negatively regulates the functional properties of CSCs. We shall briefly discuss potential reasons behind the failure of the first-in-class clinical trial of MRX34, a liposomal miR-34a mimic. Finally, we offer several clinical settings where miR-34a can potentially be deployed to therapeutically target CSCs and advanced, therapy-resistant, and p53-mutant tumors in order to overcome therapy resistance and curb tumor relapse.

Nanosized Drug Delivery Systems for Breast Cancer Stem Cell Targeting

Breast cancer stem cells (BCSCs), also known as breast cancer initiating cells, are reported to be responsible for the initiation, progression, therapeutic resistance, and relapse of breast cancer. Conventional therapeutic agents mainly kill the bulk of breast tumor cells and fail to eliminate BCSCs, even enhancing the fraction of BCSCs in breast tumors sometimes. Therefore, it is essential to develop specific and effective methods of eliminating BCSCs that will enhance the efficacy of killing breast tumor cells and thereby, increase the survival rates and quality of life of breast cancer patients. Despite the availability of an increasing number of anti-BCSC agents, their clinical translations are hindered by many issues, such as instability, low bioavailability, and off-target effects. Nanosized drug delivery systems (NDDSs) have the potential to overcome the drawbacks of anti-BCSC agents by providing site-specific delivery and enhancing of the stability and bioavailability of the delivered agents. In this review, we first briefly introduce the strategies and agents used against BCSCs and then highlight the mechanism of action and therapeutic efficacy of several state-of-the-art NDDSs that can be used to treat breast cancer by eliminating BCSCs.

MYC dysfunction modulates stemness and tumorigenesis in breast cancer

As a transcription factor and proto-oncogene, MYC is known to be deregulated in a variety of tumors, including breast cancer. However, no consistent conclusion on the role and mechanism of MYC deregulation during breast cancer carcinogenesis has been formed. Here, we used the UALCAN, bc-GenExMiner, TCGA, cBioportal, STRING and Kaplan-Meier Plotter databases to explore the mRNA expression, prognosis, transcriptional profile changes, signal pathway rewiring and interaction with the cancer stem cells of MYC in breast cancer. We found that the expression of MYC varies in different subtypes of breast cancer, with relatively high frequency in TNBC. As a transcription factor, MYC not only participates in the rewiring of cancer signaling pathways, such as estrogen, WNT, NOTCH and other pathways, but also interacts with cancer stem cells. MYC is significantly positively correlated with breast cancer stem cell markers such as CD44, CD24, and ALDH1. Collectively, our results highlight that MYC plays an important regulatory role in the occurrence of breast cancer, and its amplification can be used as a predictor of diagnosis and prognosis. The interaction between MYC and cancer stem cells may play a crucial role in regulating the initiation and metastasis of breast cancer.

Cancer Stem Cells in the Immune Microenvironment

Cancer stem cells are a subpopulation of cancer cells responsible for the most demanding and aggressive cancer cell phenotypes: therapy resistance, a self-protective feature of stem cells; distant metastasis, requiring anchorage independence for survival in the circulation; and recurrence, which is related to the dormant-active cycling of stem cells. Normal tissues are composed of parenchymal cells, supportive connective components, and cellular disposal systems for removing the products of physiological wear and tear. Cancer stem cells develop from normal counterparts and progressively interact with their microenvironments, modifying and conditioning the cancer microenvironment. Cancer-associated myeloid cells constitute a major element of the cancer microenvironment. During the process of carcinogenesis, cancer stem cells and their intimately associated myeloid cells mutually interact and evolve, such that the cancer cells potentiate the activity of the myeloid cells and, in return, the myeloid cells increase cancer stem cell characteristics. Normal myeloid cells function as key accessory cells to maintain homeostasis in normal tissues and organs; in cancers, these cells co-evolve with the malignant parenchymal cells and are involved in every aspect of cancer cell biology, including proliferation, invasion, distant metastasis, and the development of resistance to therapy. In this way, cancer-associated myeloid cells provide two of the key hallmarks of cancer: evasion of immune destruction and cancer-promoting inflammation.

Making radiation therapy more effective in the era of precision medicine

Cancer has become a leading cause of death and constitutes an enormous burden worldwide. Radiation is a principle treatment modality used alone or in combination with other forms of therapy, with 50%–70% of cancer patients receiving radiotherapy at some point during their illness. It has been suggested that traditional radiotherapy (daily fractions of approximately 1.8–2 Gy over several weeks) might select for radioresistant tumor cell sub-populations, which, if not sterilized, give rise to local treatment failure and distant metastases. Thus, the challenge is to develop treatment strategies and schedules to eradicate the resistant subpopulation of tumorigenic cells rather than the predominant sensitive tumor cell population. With continued technological advances including enhanced conformal treatment technology, radiation oncologists can increasingly maximize the dose to tumors while sparing adjacent normal tissues, to limit toxicity and damage to the latter. Increased dose conformality also facilitates changes in treatment schedules, such as changes in dose per treatment fraction and number of treatment fractions, to enhance the therapeutic ratio. For example, the recently developed large dose per fraction treatment schedules (hypofractionation) have shown clinical advantage over conventional treatment schedules in some tumor types. Experimental studies suggest that following large acute doses of radiation, recurrent tumors, presumably sustained by the most resistant tumor cell populations, may in fact be equally or more radiation sensitive than the primary tumor. In this review, we summarize the related advances in radiotherapy, including the increasing understanding of the molecular mechanisms of radioresistance, and the targeting of these mechanisms with potent small molecule inhibitors, which may selectively sensitize tumor cells to radiation.

Eradicating the Roots: Advanced Therapeutic Approaches Targeting Breast Cancer Stem Cells

Accumulating evidences have demonstrated that the existence of breast cancer-initiating cells, which drives the original tumorigenicity, local invasion and migration propensity of breast cancer. These cells, termed as breast cancer stem cells (BCSCs), possess properties including self-renewal, multidirectional differentiation and proliferative potential, and are believed to play important roles in the intrinsic drug resistance of breast cancer. One of the reasons why BCBCs cause difficulties in breast cancer treating is that BCBCs can control both genetic and non-genetic elements to keep their niches safe and sound, which allows BCSCs for constant self-renewal and differentiation. Therapeutic strategies designed to target BCSCs may ultimately result in effective interventions for the treatment of breast cancer. Novel strategies including nanomedicine, oncolytic virus therapy, immunotherapy and induced differentiation therapy are emerging and proved to be efficient in anti-BCSCs therapy. In this review, we summarized breast tumor biology and the current challenges of breast cancer therapies, focused on breast cancer stem cells, and introduced promising therapeutic strategies targeting BCSCs.

Coriolic Acid (13-(S)-Hydroxy-9Z, 11E-octadecadienoic Acid) from Glasswort (Salicornia herbacea L.) Suppresses Breast Cancer Stem Cell through the Regulation of c-Myc

Cancer stem cells have certain characteristics, such as self-renewal, differentiation, and drug resistance, which are related to tumor progression, maintenance, recurrence, and metastasis. In our study, we targeted breast cancer stem cells (BCSCs) using a natural compound, coriolic acid, from Salicornia herbacea L. This compound was isolated by mammosphere formation inhibition bioassay-guided fractionation and identified by using NMR spectroscopy and electrospray ionization mass spectrometry. Coriolic acid inhibited the formation of mammospheres and induced BCSC apoptosis. It also decreased the subpopulation of CD44^high/CD24^low cells, a cancer stem cell (CSC) phenotype, and specific genes related to CSCs, such as Nanog,Oct4, and CD44. Coriolic acid decreased the transcriptional and translational levels of the c-Myc gene, which is a CSC survival factor. These results indicated that coriolic acid could be a novel compound to target BCSCs via regulation of c-Myc.