Breast cancers, mammary stem cells, and cancer stem cells, characteristics, and hypotheses

Navigating skeletal wellness after breast cancer

Breast cancer is the leading cause of death in the female population. Hormone receptor-positive cancers are usually treated with surgery in combination with endocrine therapy. The latter is known to lower estrogen levels, contributing, therefore, to loss of bone density (BMD) and higher risk of fracture. Bone-modifying agents (BMAs) can regulate the bone-related adverse effects of cancer treatment. In premenopausal women, intravenous zoledronate effectively prevents bone loss. However, the evidence regarding its ability to reduce disease recurrence remains inconclusive. In postmenopausal women, denosumab demonstrates the most substantial evidence for fracture prevention, supported by one well-powered randomized controlled trial, but has not been shown to confer anticancer benefits. While bisphosphonates effectively prevent and reduce clinical vertebra fractures, their impact on overall fracture risk is unclear. In clinical practice, management of bone health in this group of patients starts with stratification for the risk of fracture. This can be done using the FRAX algorithm; measurements of bone mineral density can help to optimize stratification for individuals at higher fracture risk. Caution is advised when interpreting the results, as the FRAX algorithm has been considered to underestimate the true fracture risk in this population, given that the algorithm has not been adjusted for the effect of anti-cancer agents. Nowadays, clodronate, ibandronate, and zoledronic acid are recommended for bone protection in this group of patients, while denosumab is not. Further research is required to highlight the optimal BMA according to patient characteristics.

Cancer stem cell specificity as new targets in breast tumor treatment

Background

Breast cancer is a prevalent malignant tumor affecting females, with treatment options including surgery, radiotherapy, chemotherapy, and endocrine therapy.

Methods

This review synthesizes existing literature on breast cancer stem cells and their applications in breast cancer treatment. PubMed, Web of Science, and other relevant databases were systematically searched using keywords such as "breast cancer stem cells," "immunotherapy," "gene therapy," and "cell therapy." Studies published in English were included, and their findings were analyzed to provide insights into the characteristics and therapeutic potential of breast cancer stem cells.

Results

Breast cancer stem cells exhibit unique properties that contribute to tumor initiation, progression, recurrence, and therapy resistance. Immunotherapy targeting breast cancer stem cells shows promise in overcoming these challenges, but issues such as lack of specificity and drug resistance need to be addressed.

Conclusions

Breast cancer stem cells represent promising targets for innovative therapeutic strategies aimed at improving treatment outcomes in breast cancer patients.

Super-enhancer-hijacking RBBP7 potentiates metastasis and stemness of breast cancer via recruiting NuRD complex subunit LSD1

BACKGROUND

Aberrant epigenetic and transcriptional events that drive cancer progression could be precisely targeted. We aimed to uncover the epigenetic roles of RBBP7 on breast cancer (BCa) stemness and metastasis.

METHODS

The bioinformatic analysis was used to assess the clinical significance of RBBP7 in BCa. CCK8, colony formation, and Transwell assays were utilized to estimate the oncogenic functions of RBBP7. The ChIP-qPCR and dual-luciferase reporter assays were used to investigate the epigenetic mechanisms of RBBP7. Tumor sphere formation assays were conducted to assess the self-renewal abilities of BCa cells. Tail vein injection models were constructed to assess the in vivo metastatic efficiency of BCa cells. The PDOs and PDX models were used to assess the clinical significance of ORY-1001 in suppressing BCa.

RESULTS

Here, we found that RBBP7 is upregulated in BCa and associated with poor prognosis. Functional experiments demonstrated that RBBP7 enhanced BCa proliferation and distal metastasis. Mechanistically, a novel RBBP7-super-enhancer (SE) was identified using multiple databases in BCa. RBBP7-SE sustained high levels of RBBP7 and CRISPR/Cas9-mediated deletion of SE decreased RBBP7 levels and suppressed BCa malignant features. Further, our data showed that RBBP7 may correlate with stemness pathway and significantly potentiated BCa cancer stem-like properties. Additionally, RBBP7 interacts with LSD1 and relies on LSD1 to erase suppressive H3K9me3 markers in promoters of downstream stemness targets (SOX9/SOX2/OCT4/CCND1). Thus, RBBP7 recruits LSD1 to transcriptionally upregulate the expressions of key stemness genes, and promote tumor stemness capacity. Pharmacological inhibition of LSD1 by ORY-1001 effectively repressed RBBP7-high BCa tumor growth, stemness properties, and distant metastasis.

CONCLUSIONS

Together, our results establish that the SE-RBBP7-LSD1 axis represents a potential therapeutic target for BCa treatment.

Transcription factor Yin Yang 1 enhances epithelial-mesenchymal transition, migration, and stemness of non-small cell lung cancer cells by targeting sonic hedgehog

Non-small cell lung cancer (NSCLC) is a frequent type of lung cancer. Transcription factor Yin Yang 1 (YY1), an endogenous transcription factor containing zinc finger structure, can accelerate NSCLC progression. However, the impact of YY1 on the stemness of NSCLC cells and the mechanism of promoting NSCLC cell progression is unclear. YY1 and Sonic hedgehog (Shh) expressions were monitored by RT-qPCR, western blot, and immunohistochemistry. Overall survival was tested through Kaplan-Meier analysis. The interaction between YY1 and Shh was confirmed. Then, cell migration, stemness, and epithelial-mesenchymal transition (EMT) were assessed with functional experiments in vitro and in vivo. YY1 and Shh were highly expressed in NSCLC tissues and positively correlated with the poor OS of NSCLC patients. Functional experiments denoted that YY1 or Shh overexpression could accelerate EMT, migration, and stemness of NSCLC cells, and YY1 or Shh knockdown played the opposite role to its overexpression. Mechanism analysis disclosed that Shh, as a target gene of YY1, was positively related to YY1. The rescued experiment manifested that Shh silencing could reverse the induction effect of YY1 overexpression on EMT, migration, and stemness of NSCLC cells. In vivo experiments also confirmed that YY1 could accelerate tumor growth and EMT and weaken apoptosis. YY1 promotes NSCLC EMT, migration, and stemness by Shh, which might be novel diagnostic markers and therapeutic targets for NSCLC therapy.

Pubertal low dose exposure to benzophenone-3 (BP-3) alters murine mammary stem cell functions

Benzophenone-3 (BP-3) is an organic UV filter that is widely used in personal care products and has been indicated to have negative impacts on the environment and human health. The mammary glands of humans and rodents have been confirmed to be target organs affected by BP-3 exposure. However, limited information is available on the underlying mechanism currently. In this study, we hypothesized that low-concentration BP3 exposure during puberty might lead to a susceptibility to tumors through the mediation of mammary stem cells. Our findings revealed that BP-3 exposure at 50 mg/kg/day for 5 weeks during puberty led to reproductive outcomes such as reduced body weight, decreased serum estradiol and progesterone levels, and increased terminal end bud (TEB) numbers and areas. These effects were accompanied by a decreased fraction of basal mammary stem cells and decreased self-renewal and differentiation abilities of basal mammary stem cells in vitro and in vivo such as decreased sphere formation ability, a smaller 3D structure, increased branching points and hyperplastic lesions in regenerated mammary glands. Notably, for the regenerated mammary glands formed by the basal mammary stem cells of BP-3-treated mice, a decrease in the fraction of basal mammary stem cells and decreased expression levels of the milk protein β-casein and STAT5 were observed. Taken together, our data suggest that pubertal BP-3 exposure decreases the function of basal mammary stem cells such that they induce the abnormal development of mammary glands.

Adiponectin Influences the Behavior of Stem Cells in Hormone-Resistant Breast Cancer

In the breast tumor microenvironment (TME), adipocytes exert a selective pressure on the behavior of breast cancer stem cells (BCSCs), which are involved in endocrine therapy resistance. In obesity, adipocytes secrete reduced levels of adiponectin, which promotes the growth and progression of ERα-positive breast cancer (BC). Here, we examined how low adiponectin levels affect the enrichment of the BCSC subpopulation and the mechanisms contributing to the maintenance of endocrine therapy resistance in BC. Flow cytometry, qRT-PCR, and Western blotting analysis were performed to assess stemness, the cell cycle, and apoptosis markers in MCF-7 wild-type (WT) and tamoxifen-resistant (TR) mammospheres. nLC-MS/MS was employed to profile and compare the proteome of BCSCs. Differentially expressed proteins were intersected with data from the MetacoreTM dataset. Our study demonstrated that adiponectin increased the percentage of CD44+/CD24-/ALDH1+ stem-like cells in TR MCF-7 mammospheres. Specifically, adiponectin contributed to the maintenance of BCSC bulk in TR MCF-7 cells through a slow cycling rate, supported by decreased levels of Cyclin D1 and Ki67 and increased p21 and p27 expression, and through escape from apoptosis, sustained by reduced ROS production and preserved maintenance of mitochondrial membrane potential. Our results provide new insights into the contribution of adiponectin to poor ERα-positive BC outcomes. Deeply understanding adiponectin's role in stemness may disclose novel therapeutic approaches to treat hormone-resistant obese BC patients.

True cancer stem cells exhibit relative degrees of dormancy and genomic stability

BACKGROUND

Cancer stem cells in human tumors have been defined by stem cell markers, embryonal signaling pathways and characteristic biology, ie., namely the ability to repopulate the proliferating population. However, even if these properties can be demonstrated within a tumor cell subpopulation, it does not mean that they are truly hierarchical stem cells because they could have been derived from the proliferating population in a reversible manner.

METHODS

Using a human PDX, Mary-X, that overall expressed a strong cancer stem cell phenotype, the study conducted both GPP-labelled retroviral transfection and fluorescent microsphere uptake studies to distinguish proliferating from dormant cells and array CGH to identify regions of amplifications (gains) and deletions (losses) on the overall Mary-X population and then applied derived probes by FISH on individual cells to identify a genomically stable subpopulation.

RESULTS

Whereas 97-99 % of the cells expressed retroviral GFP and not fluorescent particles and showed numerous gene amplifications and deletions, approximately 1-3 % of the cells showed the opposite. The subpopulation with the retained fluorescent microspheres and exhibiting genomic stability was significantly smaller in size than their GFP-expressing and genomically unstable counterparts. Sorting Mary-X spheroids on the basis of either CD133 or ALDH positivity further enriched for this subpopulation.

CONCLUSIONS

These studies indicate that a truly biological cancer stem cell subpopulation exists that exhibits both dormancy and genomic stability. This subpopulation could not have been derived from the proliferating and resulting genomically unstable population and therefore represents a truly hierarchical stem cell subpopulation capable of only unidirectional differentiation.

Fetal Mammary Gland Development and Offspring's Breast Cancer Risk in Adulthood

While advancements in early detection and improved access to care have significantly enhanced breast cancer survival rates, the disease remains a significant global malignancy, constituting approximately 12.5% of all new cancer cases and claiming nearly 700,000 lives in 2020. As a result, there is widespread consensus that the most sustainable solution lies in prevention. Indeed, preventive strategies, including lifestyle modifications and research into risk-reducing interventions, offer the potential to address the root causes of noncommunicable diseases such as breast cancer. While conventional wisdom has long attributed established risk factors for breast cancer to age, lifestyle, familial history, and reproductive factors, evidence highlights the maternal environment as a pivotal stage for fetal programming of disease risk, as elucidated in the developmental origins of health and disease (DOHaD) framework. Consequently, a growing body of research has been focused on elucidating epigenomic signatures that influence fetal development while shaping health outcomes and susceptibility to diseases later in life. This review aims to identify fetal mammary developmental genes that have been implicated in breast cancer etiology and the potential interplay of maternal environment in epigenetic programming of breast cancer risk in adulthood.

Cancer immune evasion, immunoediting and intratumour heterogeneity

Cancers can avoid immune-mediated elimination by acquiring traits that disrupt antitumour immunity. These mechanisms of immune evasion are selected and reinforced during tumour evolution under immune pressure. Some immunogenic subclones are effectively eliminated by antitumour T cell responses (a process known as immunoediting), which results in a clonally selected tumour. Other cancer cells arise to resist immunoediting, which leads to a tumour that includes several distinct cancer cell populations (referred to as intratumour heterogeneity (ITH)). Tumours with high ITH are associated with poor patient outcomes and a lack of responsiveness to immune checkpoint blockade therapy. In this Review, we discuss the different ways that cancer cells evade the immune system and how these mechanisms impact immunoediting and tumour evolution. We also describe how subclonal antigen presentation in tumours with high ITH can result in immune evasion.

Adipocyte-derived fatty acid uptake induces obesity-related breast cancer progression: a review

Obesity is a metabolic disorder that occurs when excess energy taken into the body is stored as fat. It is known that this metabolic imbalance affects the development of other diseases such as cancer, cardiovascular diseases, insulin resistance, and diabetes. The main cellular component of adipose tissue is adipocytes, and the environmental interactions of adipocytes are important to study the mechanism of disorder formation. Breast tissue is rich in adipose tissue and obesity is known to be an important risk factor in the development of breast cancer. Altered adipogenesis and lipogenesis processes in adipocytes in breast tissue support tumor development through the transfer of fatty acids released from adipocytes. We believe that blending adipocyte biology with breast cancer development is important for investigating the mechanisms that regulate breast tumor malignant behavior and providing new targets for treatment. Fatty acids, which are an energy source for breast cancer cells, are discussed from molecular perspectives in this review.

The Genomic and Biologic Landscapes of Breast Cancer and Racial Differences

Breast cancer is a significant health challenge worldwide and is the most frequently diagnosed cancer among women globally. This review provides a comprehensive overview of breast cancer biology, genomics, and microbial dysbiosis, focusing on its various subtypes and racial differences. Breast cancer is primarily classified into carcinomas and sarcomas, with carcinomas constituting most cases. Epidemiology and breast cancer risk factors are important for public health intervention. Staging and grading, based on the TNM and Nottingham grading systems, respectively, are crucial to determining the clinical outcome and treatment decisions. Histopathological subtypes include in situ and invasive carcinomas, such as invasive ductal carcinoma (IDC) and invasive lobular carcinoma (ILC). The review explores molecular subtypes, including Luminal A, Luminal B, Basal-like (Triple Negative), and HER2-enriched, and delves into breast cancer's histological and molecular progression patterns. Recent research findings related to nuclear and mitochondrial genetic alterations, epigenetic reprogramming, and the role of microbiome dysbiosis in breast cancer and racial differences are also reported. The review also provides an update on breast cancer's current diagnostics and treatment modalities.

Integrated single-cell analysis reveals distinct epigenetic-regulated cancer cell states and a heterogeneity-guided core signature in tamoxifen-resistant breast cancer

BACKGROUND

Inter- and intra-tumor heterogeneity is considered a significant factor contributing to the development of endocrine resistance in breast cancer. Recent advances in single-cell RNA sequencing (scRNA-seq) and single-cell ATAC sequencing (scATAC-seq) allow us to explore inter- and intra-tumor heterogeneity at single-cell resolution. However, such integrated single-cell analysis has not yet been demonstrated to characterize the transcriptome and chromatin accessibility in breast cancer endocrine resistance.

METHODS

In this study, we conducted an integrated analysis combining scRNA-seq and scATAC-seq on more than 80,000 breast tissue cells from two normal tissues (NTs), three primary tumors (PTs), and three tamoxifen-treated recurrent tumors (RTs). A variety of cell types among breast tumor tissues were identified, PT- and RT-specific cancer cell states (CSs) were defined, and a heterogeneity-guided core signature (HCS) was derived through such integrated analysis. Functional experiments were performed to validate the oncogenic role of BMP7, a key gene within the core signature.

RESULTS

We observed a striking level of cell-to-cell heterogeneity among six tumor tissues and delineated the primary to recurrent tumor progression, underscoring the significance of these single-cell level tumor cell clusters classified from scRNA-seq data. We defined nine CSs, including five PT-specific, three RT-specific, and one PT-RT-shared CSs, and identified distinct open chromatin regions of CSs, as well as a HCS of 137 genes. In addition, we predicted specific transcription factors (TFs) associated with the core signature and novel biological/metabolism pathways that mediate the communications between CSs and the tumor microenvironment (TME). We finally demonstrated that BMP7 plays an oncogenic role in tamoxifen-resistant breast cancer cells through modulating MAPK signaling pathways.

CONCLUSIONS

Our integrated single-cell analysis provides a comprehensive understanding of the tumor heterogeneity in tamoxifen resistance. We envision this integrated single-cell epigenomic and transcriptomic measure will become a powerful approach to unravel how epigenetic factors and the tumor microenvironment govern the development of tumor heterogeneity and to uncover potential therapeutic targets that circumvent heterogeneity-related failures.

Dissection of triple-negative breast cancer microenvironment and identification of potential therapeutic drugs using single-cell RNA sequencing analysis

Breast cancer remains a leading cause of mortality in women worldwide. Triple-negative breast cancer (TNBC) is a particularly aggressive subtype characterized by rapid progression, poor prognosis, and lack of clear therapeutic targets. In the clinic, delineation of tumor heterogeneity and development of effective drugs continue to pose considerable challenges. Within the scope of our study, high heterogeneity inherent to breast cancer was uncovered based on the landscape constructed from both tumor and healthy breast tissue samples. Notably, TNBC exhibited significant specificity regarding cell proliferation, differentiation, and disease progression. Significant associations between tumor grade, prognosis, and TNBC oncogenes were established via pseudotime trajectory analysis. Consequently, we further performed comprehensive characterization of the TNBC microenvironment. A crucial epithelial subcluster, E8, was identified as highly malignant and strongly associated with tumor cell proliferation in TNBC. Additionally, epithelial-mesenchymal transition (EMT)-associated fibroblast and M2 macrophage subclusters exerted an influence on E8 through cellular interactions, contributing to tumor growth. Characteristic genes in these three cluster cells could therefore serve as potential therapeutic targets for TNBC. The collective findings provided valuable insights that assisted in the screening of a series of therapeutic drugs, such as pelitinib. We further confirmed the anti-cancer effect of pelitinib in an orthotopic 4T1 tumor-bearing mouse model. Overall, our study sheds light on the unique characteristics of TNBC at single-cell resolution and the crucial cell types associated with tumor cell proliferation that may serve as potent tools in the development of effective anti-cancer drugs.

Exploring the interplay between triple-negative breast cancer stem cells and tumor microenvironment for effective therapeutic strategies

Triple-negative breast cancer (TNBC) is a highly aggressive and metastatic malignancy with poor treatment outcomes. The interaction between the tumor microenvironment (TME) and breast cancer stem cells (BCSCs) plays an important role in the development of TNBC. Owing to their ability of self-renewal and multidirectional differentiation, BCSCs maintain tumor growth, drive metastatic colonization, and facilitate the development of drug resistance. TME is the main factor regulating the phenotype and metastasis of BCSCs. Immune cells, cancer-related fibroblasts (CAFs), cytokines, mesenchymal cells, endothelial cells, and extracellular matrix within the TME form a complex communication network, exert highly selective pressure on the tumor, and provide a conducive environment for the formation of BCSC niches. Tumor growth and metastasis can be controlled by targeting the TME to eliminate BCSC niches or targeting BCSCs to modify the TME. These approaches may improve the treatment outcomes and possess great application potential in clinical settings. In this review, we summarized the relationship between BCSCs and the progression and drug resistance of TNBC, especially focusing on the interaction between BCSCs and TME. In addition, we discussed therapeutic strategies that target the TME to inhibit or eliminate BCSCs, providing valuable insights into the clinical treatment of TNBC.

Diagnostic and predictive significance of the ferroptosis-related gene TXNIP in lung adenocarcinoma stem cells based on multi-omics

BACKGROUND

Lung cancer stands as the foremost cause of cancer-related fatalities globally. The presence of cancer stem cells (CSCs) poses a challenge, rendering current targeted tumor therapies ineffective. This study endeavors to investigate a novel therapeutic approach focusing on ferroptosis and delves into the expression of ferroptosis-related genes within lung CSCs.

METHODS

We systematically examined RNA-seq datasets derived from lung tumor cells (LTCs) and lung cancer stem cells (LSCs), as previously investigated in our research. Our focus was on analyzing differentially expressed genes (DEGs) related to ferroptosis. Utilizing the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO), we conducted functional analysis of these ferroptosis-related DEGs. Additionally, we employed protein‒protein interaction networks to identify hub genes. LC‒MS/MS analysis of LTCs and LSCs was conducted to pinpoint the crucial ferroptosis-related gene-thioredoxin-interacting protein (TXNIP).Further, we delved into the immune cell infiltration landscape of LTCs and LSCs, examining the correlation between TXNIP and lung adenocarcinoma (LUAD) using data from The Cancer Genome Atlas (TCGA) database. To complement these findings, we measured the expression levels of TXNIP, glutathione peroxidase 4(GPX4), nuclear receptor coactivator 4 (NCOA4) in LUAD tissues through immunohistochemistry (IHC) staining.

RESULTS

A total of 651 DEGs were identified, with 17 of them being ferroptosis-related DEGs. These seventeen genes were categorized into four groups: driver genes, suppressor genes, unclassified genes, and inducer genes. Enrichment analysis revealed significant associations with oxidative stress, cell differentiation, tissue development, and cell death processes. The RNA-seq analysis demonstrated consistent gene expression patterns with protein expression, as evidenced by mass spectrometry analysis. Among the identified genes, SFN and TXNIP were singled out as hub genes, with TXNIP showing particularly noteworthy expression. The expression of the ferroptosis-related gene TXNIP exhibited correlations with the presence of an immunosuppressive microenvironment, TNM stages, and the degree of histological differentiation.Also, the ferroptosis-markers GPX4 and NCOA4 displayed correlations with LUAD. This comprehensive analysis underscores the significance of TXNIP in the context of ferroptosis-related processes and their potential implications in cancer development and progression.

CONCLUSION

The investigation conducted in this study systematically delved into the role of the ferroptosis-related gene TXNIP in Lung CSCs. The identification of TXNIP as a potentially valuable biomarker in this context could have significant implications for refining prognostic assessments and optimizing therapeutic strategies for advanced lung cancer.

Exploring the promising potential of induced pluripotent stem cells in cancer research and therapy

The advent of iPSCs has brought about a significant transformation in stem cell research, opening up promising avenues for advancing cancer treatment. The formation of cancer is a multifaceted process influenced by genetic, epigenetic, and environmental factors. iPSCs offer a distinctive platform for investigating the origin of cancer, paving the way for novel approaches to cancer treatment, drug testing, and tailored medical interventions. This review article will provide an overview of the science behind iPSCs, the current limitations and challenges in iPSC-based cancer therapy, the ethical and social implications, and the comparative analysis with other stem cell types for cancer treatment. The article will also discuss the applications of iPSCs in tumorigenesis, the future of iPSCs in tumorigenesis research, and highlight successful case studies utilizing iPSCs in tumorigenesis research. The conclusion will summarize the advancements made in iPSC-based tumorigenesis research and the importance of continued investment in iPSC research to unlock the full potential of these cells.

Regulation of the stem‑like properties of estrogen receptor‑positive breast cancer cells through NR2E3/NR2C2 signaling

Cancer stem cells (CSCs) are major drivers of metastasis, drug resistance and recurrence in numerous cancers. However, critical factors that can modulate CSC stemness have not been clearly identified. Nuclear receptor subfamily 2 group E member 3 (nr2e3) expression has been previously reported to be positively associated with drug sensitivity and favorable clinical outcomes in patients with estrogen receptor (ER)+ breast cancer. This suggests that nr2e3 expression may be inversely associated with CSC stemness in this type of tumor cells. The present study aimed to investigate the regulatory roles of NR2E3 in the stem-like properties of ER+ breast cancer cells and to identify the underlying mechanisms. Bioinformatics analysis was performed using the data derived from the Cancer Genome Atlas database. Nr2e3-specific shRNA and nuclear receptor subfamily 2 group C member 2 (nr2c2) overexpressed plasmids were constructed to silence and enhance the expression of nr2e3 and nr2c2, respectively. Transwell and wound healing experiments were conducted to evaluate the migration and invasion ability of MCF7 cells, while colony formation tests were used to evaluate the clonality. Flow cytometry was used to detect the percentage of CD44+CD24-/low cells. Reverse transcription-quantitative PCR and western blotting were performed to detect expression at the mRNA and protein levels. The results showed that compared with normal breast tissues and MCF10A cells, the expression of nr2e3 was increased in ER+ breast tumor tissues and cell lines. Nr2e3 silencing promoted the migration, invasion and colony-forming ability of the ER+ MCF7 cells. It also increased the expression of epithelial-mesenchymal transition markers and stem cell-related transcription factors, in addition to the percentage of CD44+CD24-/low cells. The expression of nr2e3 and nr2c2 was found to be positively correlated. Nr2e3 knockdown decreased the mRNA and protein expression levels of nr2c2, whereas nr2c2 overexpression reversed the elevated CD44+CD24-/low cell ratio and the increased migratory activity caused by nr2e3 silencing. The results of the present study suggest that NR2E3 may serve an important role in modulating the stem-like properties of ER+ breast cancer cells, where NR2E3/NR2C2 signaling may be a therapeutic target in ER+ breast cancer.

Phloridzin Docosahexaenoate Inhibits Spheroid Formation by Breast Cancer Stem Cells and Exhibits Cytotoxic Effects against Paclitaxel-Resistant Triple Negative Breast Cancer Cells

The eradication of cancer stem cells (CSCs) is vital to successful cancer treatment and overall disease-free survival. CSCs are a sub-population of cells within a tumor that are defined by their capacity for continuous self-renewal and recapitulation of new tumors, demonstrated in vitro through spheroid formation. Flavonoids are a group of phytochemicals with potent anti-oxidant and anti-cancer properties. This paper explores the impact of the flavonoid precursor phloridzin (PZ) linked to the ω-3 fatty acid docosahexaenoate (DHA) on the growth of MCF-7 and paclitaxel-resistant MDA-MB-231-TXL breast cancer cell lines. Spheroid formation assays, acid phosphatase assays, and Western blotting were performed using MCF-7 cells, and the cell viability assays, Annexin-V-488/propidium iodide (PI) staining, and 7-aminoactinomycin D (7-AAD) assays were performed using MDA-MB-231-TXL cells. PZ-DHA significantly reduced spheroid formation, as well as the metabolic activity of MCF-7 breast cancer cells in vitro. Treatment with PZ-DHA also suppressed the metabolic activity of MDA-MB-231-TXL cells and led to apoptosis. PZ-DHA did not have an observable effect on the expression of the drug efflux transporters ATP-binding cassette super-family G member 2 (ABCG2) and multidrug resistance-associated protein 1 (MRP1). PZ-DHA is a potential treatment avenue for chemo-resistant breast cancer and a possible novel CSC therapy. Future pre-clinical studies should explore PZ-DHA as a chemo-preventative agent.

Cancer Stem Cells are Actually Stem Cells with Disordered Differentiation: the Monophyletic Origin of Cancer

Cancer stem cells (CSCs) play an important role in cancer development. Based on advancements in CSC research, we propose a monophyletic model of cancer. This model is based on the idea that CSCs are stem cells with disordered differentiation whose original purpose was to repair damaged tissues. Inflammatory responses and damage repair signals are crucial for the creation and maintenance of CSCs. Normal quiescent stem cells are activated by environmental stimulation, such as an inflammatory response, and undergo cell division and differentiation. In the initial stage of cancer development, stem cell differentiation leads to heteromorphism due to the accumulation of gene mutations, resulting in the development of metaplasia or precancerosis. In the second stage, accumulated mutations induce poor differentiation and lead to cancer development. The monophyletic model illustrates the evolution, biological behavior, and hallmarks of CSCs, proposes a concise understanding of the origin of cancer, and may encourage a novel therapeutic approach.

A Tumor Microenvironment-Driven Network Regulated by STAT3 and p65 Negatively Controls the Enrichment of Cancer Stem Cells in Human HR+/HER2- Breast Cancer

Hormone receptor-positive and HER2-negative (HR+/HER2-; luminal A) tumors are prevalent in breast cancer. Our past studies demonstrated that "TME Stimulation" (estrogen + TNFα + EGF, representing three arms of the tumor microenvironment, TME) has enriched metastasis-forming cancer stem cells (CSCs) in HR+/HER2- human breast cancer cells. Here, following information obtained by RNAseq analyses of TME-stimulated CSCs and Non-CSCs, we found that TME Stimulation has induced the activation of S727-STAT3, Y705-STAT3, STAT1 and p65. Upon TME Stimulation, stattic (STAT3 inhibitor) usage demonstrated that Y705-STAT3 activation negatively controlled CSC enrichment and epithelial-to-mesenchymal transition (EMT) traits, while inducing CXCL8 (IL-8) and PD-L1 expression. However, STAT3 knock-down (siSTAT3) had no effect on these functions; in terms of CSC enrichment, p65 had down-regulatory roles that compensated for the loss of an entire STAT3 protein. Y705-STAT3 and p65 acted additively in reducing CSC enrichment, and Y705A-STAT3 variant + sip65 has enriched chemo-resistant CSCs. Clinical data analyses revealed an inverse correlation between Y705-STAT3 + p65 phosphorylation and CSC signature in luminal A patients, and connection to improved disease course. Overall, we find regulatory roles for Y705-STAT3 and p65 in TME-stimulated HR+/HER2- tumors, with the ability to limit CSC enrichment. These findings raise concerns about using inhibitors of STAT3 and p65 as therapeutic strategies in the clinic.

Effects of extremely low-frequency magnetic fields on human MDA-MB-231 breast cancer cells: proteomic characterization

Extremely low-frequency electromagnetic fields (ELF-MF) can modify the cell viability and regulatory processes of some cell types, including breast cancer cells. Breast cancer is a multifactorial disease where a role for ELF-MF cannot be excluded. ELF-MF may influence the biological properties of breast cells through molecular mechanisms and signaling pathways that are still unclear. This study analyzed the changes in the cell viability, cellular morphology, oxidative stress response and alteration of proteomic profile in breast cancer cells (MDA-MB-231) exposed to ELF-MF (50 Hz, 1 mT for 4 h). Non-tumorigenic human breast cells (MCF-10A) were used as control cells. Exposed MDA-MB-231 breast cancer cells increased their viability and live cell number and showed a higher density and length of filopodia compared with the unexposed cells. In addition, ELF-MF induced an increase of the mitochondrial ROS levels and an alteration of mitochondrial morphology. Proteomic data analysis showed that ELF-MF altered the expression of 328 proteins in MDA-MB-231 cells and of 242 proteins in MCF-10A cells. Gene Ontology term enrichment analysis demonstrated that in both cell lines ELF-MF exposure up-regulated the genes enriched in "focal adhesion" and "mitochondrion". The ELF-MF exposure decreased the adhesive properties of MDA-MB-231 cells and increased the migration and invasion cell abilities. At the same time, proteomic analysis, confirmed by Real Time PCR, revealed that transcription factors associated with cellular reprogramming were upregulated in MDA-MB-231 cells and downregulated in MCF-10A cells after ELF-MF exposure. MDA-MB-231 breast cancer cells exposed to 1 mT 50 Hz ELF-MF showed modifications in proteomic profile together with changes in cell viability, cellular morphology, oxidative stress response, adhesion, migration and invasion cell abilities. The main signaling pathways involved were relative to focal adhesion, mitochondrion and cellular reprogramming.

Preclinical and Clinical Trials of New Treatment Strategies Targeting Cancer Stem Cells in Subtypes of Breast Cancer

Breast cancer (BC) can be classified into various histological subtypes, each associated with different prognoses and treatment options, including surgery, radiation, chemotherapy, and endocrine therapy. Despite advances in this area, many patients still face treatment failure, the risk of metastasis, and disease recurrence, which can ultimately lead to death. Mammary tumors, like other solid tumors, contain a population of small cells known as cancer stem-like cells (CSCs) that have high tumorigenic potential and are involved in cancer initiation, progression, metastasis, tumor recurrence, and resistance to therapy. Therefore, designing therapies specifically targeting at CSCs could help to control the growth of this cell population, leading to increased survival rates for BC patients. In this review, we discuss the characteristics of CSCs, their surface biomarkers, and the active signaling pathways associated with the acquisition of stemness in BC. We also cover preclinical and clinical studies that focus on evaluating new therapy systems targeted at CSCs in BC through various combinations of treatments, targeted delivery systems, and potential new drugs that inhibit the properties that allow these cells to survive and proliferate.

Breastfeeding reduces the risk of breast cancer: A call for action in high-income countries with low rates of breastfeeding

Women in the UK have a 15% lifetime risk of developing breast cancer. Like other high-income countries, women in the UK are having children later in life which increases their risk. The risk of breast cancer is reduced by 4.3% for every 12 months of breastfeeding, this is in addition to the 7.0% decrease in risk observed for each birth. Breastfeeding reduces the risk of Triple-Negative Breast Cancer (20%) and in carriers of BRCA1 mutations (22-55%). The mechanisms of reduced risk as a result of pregnancy are related to changes in RNA processing and cellular differentiation. The UK has a low rate of breastfeeding (81%) and this is contrasted to countries with higher (Sweden, Australia) and lower rates (Ireland). The low UK rate is in part due to a lack of experience in the population, todays grandmothers have less experience with breastfeeding (62%) than their daughters. An estimated 4.7% of breast cancer cases in the UK are caused by not breastfeeding. The UK only has 43% of maternity services with full Baby-Friendly accreditation which promotes compliance with the WHO 'Ten Steps to Successful Breast Feeding'. Legislation in the UK and Europe is far short of the WHO Guidance on restricting the advertising of formula milk. Expansion of the Baby-Friendly Hospital Initiative, stricter laws on the advertising of formula milk and legislation to support nursing mothers in the workplace have the potential to increase breastfeeding in the UK. Women with a family history of breast cancer should particularly be supported to breastfeed as a way of reducing their risk.

Raloxifene potentiates the effect of gefitinib in triple-negative breast cancer cell lines

Triple-negative breast cancers (TNBCs) are characterized by a lack of approved targeted therapies and remain a challenge in the clinic. Several overexpressed proteins, including epidermal growth factor receptor (EGFR), have been associated with TNBCs and are considered potential therapeutic targets. However, EGFR inhibitors alone failed to demonstrate a cutting-edge advantage for treating TNBCs over conventional chemotherapies. Studies have shown that selective estrogen receptor modulators (SERMs) tamoxifen and raloxifene also affect TNBC cell viability. The combination of gefitinib and raloxifene was assessed against TNBC cell lines in vitro. Two TNBC cell lines, MDA-MB-231 and MDA-MB-468, were used to investigate the combination of gefitinib and raloxifene on cell viability, DNA synthesis, and apoptosis. The combination was assessed on intracellular signaling pathways, colony formation, migration, and angiogenesis. In the present study, raloxifene, in combination with gefitinib, decreased cell viability. The combination potentiates apoptosis and affects the expression and phosphorylation pattern of proteins involved in cell proliferation, such as NFκB, β-catenin, and EGFR. Furthermore, evidence of apoptosis activation was also observed, along with a decreased cell migration and tumorigenicity of TNBC cells. Moreover, the combined treatment decreased the ability of neovascularization as assessed by tube formation of endothelial cells. These results suggested the potential of the combination of raloxifene and gefitinib for the prevention of TNBC growth and the appearance of metastatic events. Our findings provide the basis for future studies on the mechanism involved in raloxifene-gefitinib inhibition of ER-negative tumor growth.

Quercetin Effects on Cell Cycle Arrest and Apoptosis and Doxorubicin Activity in T47D Cancer Stem Cells

BACKGROUNDS

Targeting breast cancer stem cells with the CD44+/CD24- phenotype is critical for complete eradication of cancer cells due to its Self-renewal, differentiation, and therapeutic resistance ability. Quercetin is a popular flavonoid with lower adverse effects and has anti-tumor properties. Therefore, we assessed the anticancer activity of Quercetin and Doxorubicin alone and in combination in the T47D cells of human breast cancer and their isolated Cancer stem cells (CSCs).

MATERIALS AND METHODS

The human breast cancer cell line T47D was used for this experiment. T47D CSCs were isolated by magnetic bead sorting using the MACS system. The anticancer activity of Quercetin and Doxorubicin alone and in combination were evaluated using MTT cytotoxicity assay and cell cycle distribution and apoptosis induction by flow cytometry analysis.

RESULTS

We have shown that almost 1% of T47D cell populations are made up of CD44+/CD24- cells, which considered as cancer stem cells. Quercetin and Doxorubicin alone or in combination inhibited cell proliferation and induced apoptosis in breast cancer T47D cells and in lower extent in CD44+/CD24- cells. Quercetin significantly strengthened Doxorubicin's cytotoxicity and apoptosis induction in both cell populations. Quercetin and Doxorubicin and their combination induced G2/M arrest in the T47D cells and to a lesser extent in isolated CSCs. A value of p < 0.05 was considered as indicating a statistically significant difference.

CONCLUSION

These outcomes suggested that CSCs are a minor population of cancer cells, which play a significant role in drug resistance by being quiescent, slow cycling and resistance to apoptosis. Furthermore, our data showed that adding Quercetin to Doxorubicin is an effective approach for the treatment of both CSCs and bulk tumor cells.

Myeloid checkpoints for cancer immunotherapy

Myeloid checkpoints are receptors on the myeloid cell surface which can mediate inhibitory signals to modulate anti-tumor immune activities. They can either inhibit cellular phagocytosis or suppress T cells and are thus involved in the pathogenesis of various diseases. In the tumor microenvironment, besides killing tumor cells by phagocytosis or activating anti-tumor immunity by tumor antigen presentation, myeloid cells could execute pro-tumor efficacies through myeloid checkpoints by interacting with counter-receptors on other immune cells or cancer cells. In summary, myeloid checkpoints may be promising therapeutic targets for cancer immunotherapy.

Breast Cancer with Increased Drug Resistance, Invasion Ability, and Cancer Stem Cell Properties through Metabolism Reprogramming

Breast cancer is a heterogeneous disease, and the survival rate of patients with breast cancer strongly depends on their stage and clinicopathological features. Chemoradiation therapy is commonly employed to improve the survivability of patients with advanced breast cancer. However, the treatment process is often accompanied by the development of drug resistance, which eventually leads to treatment failure. Metabolism reprogramming has been recognized as a mechanism of breast cancer resistance. In this study, we established a doxorubicin-resistant MCF-7 (MCF-7-D500) cell line through a series of long-term doxorubicin in vitro treatments. Our data revealed that MCF-7-D500 cells exhibited increased multiple-drug resistance, cancer stemness, and invasiveness compared with parental cells. We analyzed the metabolic profiles of MCF-7 and MCF-7-D500 cells through liquid chromatography−mass spectrometry. We observed significant changes in 25 metabolites, of which, 21 exhibited increased levels (>1.5-fold change and p < 0.05) and 4 exhibited decreased levels (<0.75-fold change and p < 0.05) in MCF-7 cells with doxorubicin resistance. These results suggest the involvement of metabolism reprogramming in the development of drug resistance in breast cancer, especially the activation of glycolysis, the tricarboxylic acid (TCA) cycle, and the hexamine biosynthesis pathway (HBP). Furthermore, most of the enzymes involved in glycolysis, the HBP, and the TCA cycle were upregulated in MCF-7-D500 cells and contributed to the poor prognosis of patients with breast cancer. Our findings provide new insights into the regulation of drug resistance in breast cancer, and these drug resistance-related metabolic pathways can serve as targets for the treatment of chemoresistance in breast cancer.

Regional gain and global loss of 5-hydroxymethylcytosine coexist in genitourinary cancers and regulate different oncogenic pathways

BACKGROUND

DNA 5-hydroxymethylcytosine (5hmC) is produced by dynamic 5mC oxidation process contributing to tissue specification, and loss of 5hmC has been reported in multiple cancers including genitourinary cancers. However, 5hmC is also cell-type specific, and its variability may exist between differentiated tumor cells and cancer stem cells. Thus, cancer-associated changes in 5hmC may be contributed by distinct sets of tumor cells within the tumor tissues.

RESULTS

Here, we applied a sensitive immunoprecipitation-based method (hMeDIP-seq) to analyze 5hmC changes during genitourinary carcinogenesis (including prostate, urothelial and kidney). We confirmed the tissue-specific distribution of 5hmC in genitourinary tissues and identified regional gain and global loss of 5hmC coexisting in genitourinary cancers. The genes with gain of 5hmC during tumorigenesis were functionally enriched in regulating stemness and hypoxia, whereas were associated with poor clinical prognosis irrespective of their differences in tumor type. We identified that gain of 5hmC occurred in soft fibrin gel-induced 3D tumor spheres with a tumor-repopulating phenotype in two prostate cancer cell lines, 22RV1 and PC3, compared with conventional two-dimensional (2D) rigid dishes. Then, we defined a malignant signature derived from the differentially hydroxymethylated regions affected genes of cancer stem-like cells, which could predict a worse clinical outcome and identified phenotypically malignant populations of cells from prostate cancer tumors. Notably, an oxidation-resistant vitamin C derivative, ascorbyl phosphate magnesium, restored 5hmC and killed the cancer stem cell-like cells leading to apoptosis in prostate cancer cell lines.

CONCLUSIONS

Collectively, our study dissects the regional gain of 5hmC in maintaining cancer stem-like cells and related to poor prognosis, which provides proof of concept for an epigenetic differentiation therapy with vitamin C by 5hmC reprogramming.

MRI Images-Based Evaluation of Efficacy of Neoadjuvant Chemotherapy for Breast Cancer and Its Effect on Depression and Immune Function of Patients

The aim of this study was to investigate the therapeutic value of neoadjuvant chemotherapy for breast cancer (BC) based on magnetic resonance imaging (MRI) and to evaluate its effect on depressive mood and immune function in patients. 70 female patients with BC who received neoadjuvant chemotherapy were selected for the experiment to comprehensively evaluate the MRI image findings, immune cell levels before and after chemotherapy, as well as the depression score and influencing factors of the patients during chemotherapy. The results showed that 49 patients (70%) responded to treatment, and MRI showed that the breast mass after chemotherapy was significantly reduced. 55 patients experienced depressive mood during chemotherapy, and the incidence of depression was 78.5%. Adverse symptoms such as pain, worry, sadness, vertigo, and nausea are important factors in the development of depression in patients. However, there were no significant changes in the levels of CD4+, CD8+, CD4+/CD8+, and killer cells before and after chemotherapy, and only B cells showed a significant decrease (9.78 ± 3.65% and 7.63 ± 3.65%) (P < 0.05). In summary, neoadjuvant chemotherapy can effectively shrink the breast mass and provide favorable conditions for subsequent surgery, and its clinical efficacy can be more accurately assessed by MRI. Neoadjuvant chemotherapy has little effect on the immune function of patients, but it will promote patients to experience depression. It provides a reference for the clinical treatment and prognosis of BC patients.

Functional interplay between long non-coding RNAs and Breast CSCs

Breast cancer (BC) represents aggressive cancer affecting most women’s lives globally. Metastasis and recurrence are the two most common factors in a breast cancer patient's poor prognosis. Cancer stem cells (CSCs) are tumor cells that are able to self-renew and differentiate, which is a significant factor in metastasis and recurrence of cancer. Long non-coding RNAs (lncRNAs) describe a group of RNAs that are longer than 200 nucleotides and do not have the ability to code for proteins. Some of these lncRNAs can be mainly produced in various tissues and tumor forms. In the development and spread of malignancies, lncRNAs have a significant role in influencing multiple signaling pathways positively or negatively, making them promise useful diagnostic and prognostic markers in treating the disease and guiding clinical therapy. However, it is not well known how the interaction of lncRNAs with CSCs will affect cancer development and progression.

Here, in this review, we attempt to summarize recent findings that focus on lncRNAs affect cancer stem cell self-renewal and differentiation in breast cancer development and progression, as well as the strategies and challenges for overcoming lncRNA's therapeutic resistance.

Heavy-Ion-Induced Lung Tumors: Dose- & LET-Dependence

There is a limited published literature reporting dose-dependent data for in vivo tumorigenesis prevalence in different organs of various rodent models after exposure to low, single doses of charged particle beams. The goal of this study is to reduce uncertainties in estimating particle-radiation-induced risk of lung tumorigenesis for manned travel into deep space by improving our understanding of the high-LET-dependent dose-response from exposure to individual ion beams after low particle doses (0.03–0.80 Gy). Female CB6F1 mice were irradiated with low single doses of either oxygen, silicon, titanium, or iron ions at various energies to cover a range of dose-averaged LET values from 0.2–193 keV/µm, using ¹³⁷Cs γ-rays as the reference radiation. Sham-treated controls were included in each individual experiment totally 398 animals across the 5 studies reported. Based on power calculations, between 40–156 mice were included in each of the treatment groups. Tumor prevalence at 16 months after radiation exposure was determined and compared to the age-matched, sham-treated animals. Results indicate that lung tumor prevalence is non-linear as a function of dose with suggestions of threshold doses depending on the LET of the beams. Histopathological evaluations of the tumors showed that the majority of tumors were benign bronchioloalveolar adenomas with occasional carcinomas or lymphosarcomas which may have resulted from metastases from other sites.

A neutrophil-mediated carrier regulates tumor stemness by inhibiting autophagy to prevent postoperative triple-negative breast cancer recurrence and metastasis

Recurrence and metastasis after resection are still the main challenges in clinical treatment of breast cancer. Residual tumor and cancer stem-like cells are the primary culprits of recurrence and metastasis. Recent research studies indicate that autophagy is a cytoprotective mechanism of tumors, which maintains the stemness of cancer cells and promotes tumor proliferation and metastasis. Here, we constructed a "Trojan horse" using neutrophils as the carrier (PH-RL@NEs) to prevent the recurrence and metastasis of postoperative breast cancer. Neutrophils, as a "Trojan horse," can quickly respond to postoperative inflammation and accurately deliver drugs to the residual tumor site. The inflammation-triggered "Trojan horse" was then opened to release the liposomes containing the chemotherapeutic drug paclitaxel (PTX) and the autophagy inhibitor hydroxychloroquine (HCQ). We found that HCQ could effectively inhibit tumor cell autophagy, interfere with tumor epithelial-mesenchymal transition, and reduce the tumor stem cell-like population. In the orthotopic 4T1 postoperative recurrence models, PTX and HCQ synergistically killed tumors and regulated the stemness of tumor cells, thereby significantly inhibiting tumor recurrence and metastasis. Our work proved that the inhibition of autophagy to reduce tumor stemness is feasible and effective, which opens up a new prospect for postoperative tumor treatment. STATEMENT OF SIGNIFICANCE: The present study aimed to solve the issues of postoperative recurrence and metastasis of breast cancer and low efficiency of drug administration after surgery. For this purpose, we constructed neutrophils containing hydroxychloroquine (HCQ) and paclitaxel (PTX) co-loaded liposomes (PH-RL@NEs), which for the first time regulated the stemness of tumor cells by inhibiting autophagy, thereby inhibiting postoperative recurrence and metastasis of breast cancer cells. The results showed that PH-RL@NEs enhanced the targeted drug delivery efficiency, with the help of postoperative inflammation chemotaxis of neutrophils. HCQ effectively inhibited autophagy of tumor cells and reduced tumor stem cell-like cells, thus improving the therapeutic effect in the 4T1 in situ postoperative recurrence model.

QAP14 suppresses breast cancer stemness and metastasis via activation of dopamine D1 receptor

Breast cancer is the second leading cause of cancer-related mortality in women, mainly due to metastasis, which is strongly associated with cancer stemness. Our previous studies showed that the eradication of cancer stem-like cells (CSCs) may be related to the activation of dopamine D1 receptor (D1DR). This study aimed to explicitly demonstrate the target-role of D1DR activation in antimetastatic therapy and to investigate the potential efficacy and the underlying D1DR-related mechanisms of QAP14, a new oral compound. 4T1, MDA-MB-231, and D1DR-knockout 4T1 (4T1-D1DR) cells were selected for in vitro study, while 4T1 and 4T1-D1DR cells were further used to establish a mouse allograft model for in vivo study. Our results showed that D1DR is abundantly expressed in both 4T1 and MDA-MB-231 cells and that knocking out D1DR in 4T1 cells accelerated migration and invasion in vitro as well as lung metastasis in vivo. QAP14 inhibited colony formation, cell motility, mammosphere formation and CSC frequency, induced CSC apoptosis and D1DR expression, and increased cAMP/cGMP levels. Additionally, QAP14 showed inhibitory effects on tumor growth and lung metastasis with acceptable safety in vivo. Knocking out D1DR almost completely abolished the efficacy, confirming that QAP14 exhibits its anti-CSC and antimetastatic effects through D1DR activation. The underlying mechanisms involved suppression of the nuclear factor κB (NF-κB)/protein kinase B (Akt) pathway and consequent downregulation of both epithelial-to-mesenchymal transition (EMT) process and cancer stemness. In summary, our findings suggest a potential candidate compound, QAP14, as well as a potential target, D1DR, for metastatic breast cancer therapy.

Epigenetic Inheritance From Normal Origin Cells Can Determine the Aggressive Biology of Tumor-Initiating Cells and Tumor Heterogeneity

The acquisition of genetic- and epigenetic-abnormalities during transformation has been recognized as the two fundamental factors that lead to tumorigenesis and determine the aggressive biology of tumor cells. However, there is a regularity that tumors derived from less-differentiated normal origin cells (NOCs) usually have a higher risk of vascular involvement, lymphatic and distant metastasis, which can be observed in both lymphohematopoietic malignancies and somatic cancers. Obviously, the hypothesis of genetic- and epigenetic-abnormalities is not sufficient to explain how the linear relationship between the cellular origin and the biological behavior of tumors is formed, because the cell origin of tumor is an independent factor related to tumor biology. In a given system, tumors can originate from multiple cell types, and tumor-initiating cells (TICs) can be mapped to different differentiation hierarchies of normal stem cells, suggesting that the heterogeneity of the origin of TICs is not completely chaotic. TIC’s epigenome includes not only genetic- and epigenetic-abnormalities, but also established epigenetic status of genes inherited from NOCs. In reviewing previous studies, we found much evidence supporting that the status of many tumor-related “epigenetic abnormalities” in TICs is consistent with that of the corresponding NOC of the same differentiation hierarchy, suggesting that they may not be true epigenetic abnormalities. So, we speculate that the established statuses of genes that control NOC’s migration, adhesion and colonization capabilities, cell-cycle quiescence, expression of drug transporters, induction of mesenchymal formation, overexpression of telomerase, and preference for glycolysis can be inherited to TICs through epigenetic memory and be manifested as their aggressive biology. TICs of different origins can maintain different degrees of innate stemness from NOC, which may explain why malignancies with stem cell phenotypes are usually more aggressive.

Exosomal circCARM1 from spheroids reprograms cell metabolism by regulating PFKFB2 in breast cancer

Cancer stem cells (CSC) are the major obstacle for cancer therapy in clinic. Exosomes are one type of vesicles that containing circular RNA (circRNAs) involved in cell-cell communication. However, the roles of breast CSC (BCSC) exosomes are still unclear, and the purpose of the study was to investigate breast cancer cell metabolism reprogramming by circRNAs from BCSC exosomes. The circRNA array was performed in the exosomes secreted from spheroids of MDA-231 cells. circCARM1 was higher in BCSC exosomes than it in the parent breast cancer cells. Further investigation demonstrated that BCSC exosomes circCARM1 played an important role in breast cancer cell glycolysis by miR-1252-5p/PFKFB2. In a conclusion, BCSC exosome-derived circCARM1 played an important role in breast cancer cell glycolysis by sponging miR-1252-5p which regulated PFKFB2 expression.

Aquaporin-1 in breast cancer

The canonical function of aquaporin (AQP) water channels is to facilitate passive transport of water across cellular membranes making them essential in the regulation of body water homeostasis. Moreover, AQPs, including AQP1, have been found to be overexpressed in multiple cancer types, including breast cancer, where AQP1 overexpression is associated with poor prognosis. AQPs have been shown to affect cellular processes associated with cancer progression and spread including cell migration, angiogenesis, and proliferation. Moreover, AQPs can regulate levels of adhesion proteins at cell-cell junctions, a regulatory role, which is still largely unexplored in cancer. Understanding the molecular mechanisms of how AQP1 contributes to breast cancer progression and metastatic processes is essential to establish AQP1 as a biomarker and to develop targeted anticancer treatments for breast cancer patients. This mini-review focuses on the role of AQP1 in breast cancer.

The Single-Cell Sequencing: A Dazzling Light Shining on the Dark Corner of Cancer

Tumorigenesis refers to the process of clonal dysplasia that occurs due to the collapse of normal growth regulation in cells caused by the action of various carcinogenic factors. These “successful” tumor cells pass on the genetic templates to their generations in evolutionary terms, but they also constantly adapt to ever-changing host environments. A unique peculiarity known as intratumor heterogeneity (ITH) is extensively involved in tumor development, metastasis, chemoresistance, and immune escape. An understanding of ITH is urgently required to identify the diversity and complexity of the tumor microenvironment (TME), but achieving this understanding has been a challenge. Single-cell sequencing (SCS) is a powerful tool that can gauge the distribution of genomic sequences in a single cell and the genetic variability among tumor cells, which can improve the understanding of ITH. SCS provides fundamental ideas about existing diversity in specific TMEs, thus improving cancer diagnosis and prognosis prediction, as well as improving the monitoring of therapeutic response. Herein, we will discuss advances in SCS and review SCS application in tumors based on current evidence.

Single-cell RNA sequencing and bioinformatics as tools to decipher cancer heterogenicity and mechanisms of drug resistance

It is well known that cancer is an aggressive disease, often associated with relapse, in many cases due to drug resistance. Cancer stem cell and clonal evolution are frequently causes of innate or acquired drug resistance. Current RNA sequencing technologies do not distinguish gene expression of different cell lineages because they are based on bulk cell studies. Single-cell RNA sequencing technologies and related bioinformatics clustering and differential expression analysis represent a turning point in cancer research. They are emerging as essential tools for dissecting tumors at single-cell resolution and represent novel tools to understand carcinogenesis and drug response. In this review, we will outline the role of these new technologies in addressing cancer heterogeneity and cell lineage-dependent drug resistance.

Epigenetic Regulation of Breast Cancer Stem Cells Contributing to Carcinogenesis and Therapeutic Implications

Globally, breast cancer has remained the most commonly diagnosed cancer and the leading cause of cancer death among women. Breast cancer is a highly heterogeneous and phenotypically diverse group of diseases, which require different selection of treatments. Breast cancer stem cells (BCSCs), a small subset of cancer cells with stem cell-like properties, play essential roles in breast cancer progression, recurrence, metastasis, chemoresistance and treatments. Epigenetics is defined as inheritable changes in gene expression without alteration in DNA sequence. Epigenetic regulation includes DNA methylation and demethylation, as well as histone modifications. Aberrant epigenetic regulation results in carcinogenesis. In this review, the mechanism of epigenetic regulation involved in carcinogenesis, therapeutic resistance and metastasis of BCSCs will be discussed, and finally, the therapies targeting these biomarkers will be presented.

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.

Characterization of murine mammary stem/progenitor cells in a D-galactose-induced aging model

Aging plays an important role in many diseases, including breast cancer. Aged mammary stem/progenitor cells are perceived to be the cells of origin in breast tumorigenesis; however, the extensive use of mice who have aged naturally for research is hampered by cost, time, disease complications, and high mortality. In this study, we characterized murine mammary stem/progenitor cells in a D-galactose-induced accelerated aging model and compared them with findings from our earlier study on mice from natural aging. Our results showed that mammary glands in the D-galactose-induced aging model mimic natural aging in terms of pathological changes, epithelial cell composition, and mammary stem/progenitor cell function. These changes are accompanied by elevated inflammatory responses both systemically in the blood and locally in the mammary glands, which is similar in mice who age naturally. Our study for the first time evaluated the mammary glands and mammary stem/progenitor function in a D-galactose-induced aging model in rodents, and our findings suggest that D-galactose treatment can be used as a surrogate to study the role aged stem/progenitor cells play in breast tumorigenesis.

LncRNAs and microRNAs as Essential Regulators of Stemness in Breast Cancer Stem Cells

Breast cancer is an aggressive disease with a high incidence in women worldwide. Two decades ago, a controversial hypothesis was proposed that cancer arises from a subpopulation of “tumor initiating cells” or “cancer stem cells-like” (CSC). Today, CSC are defined as small subset of somatic cancer cells within a tumor with self-renewal properties driven by the aberrant expression of genes involved in the maintenance of a stemness-like phenotype. The understanding of the underlying cellular and molecular mechanisms involved in the maintenance of CSC subpopulation are fundamental in the development and persistence of breast cancer. Nowadays, the hypothesis suggests that genetic and epigenetic alterations give rise to breast cancer stem cells (bCSC), which are responsible for self-renewal, tumor growth, chemoresistance, poor prognosis and low survival in patients. However, the prominence of bCSC, as well as the molecular mechanisms that regulates and promotes the malignant phenotypes, are still poorly understood. The role of non-coding RNAs (ncRNAs), such as long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) acting as oncogenes or tumor suppressor genes has been recently highlighted by a plethora of studies in breast cancer. These ncRNAs positively or negatively impact on different signaling pathways that govern the cancer hallmarks associated with bCSC, making them attractive targets for therapy. In this review, we present a current summary of the studies on the pivotal roles of lncRNAs and microRNAs in the regulation of genes associated to stemness of bCSC.