Breast cancer stem cells: Features, key drivers and treatment options

A 3'-pre-tRNA-derived small RNA tRF-1-Ser regulated by 25(OH)D promotes proliferation and stemness by inhibiting the function of MBNL1 in breast cancer

BACKGROUND

We explored the potential novel anticancer mechanisms of 25-hydroxyvitamin D (25(OH)D), a vitamin D metabolite with antitumour effects in breast cancer. It is stable in serum and is used to assess vitamin D levels in clinical practice. Transfer RNA-derived small RNAs are small noncoding RNAs that generate various distinct biological functions, but more research is needed on their role in breast cancer.

METHODS

Small RNA microarrays were used to explore the novel regulatory mechanism of 25(OH)D. High-throughput RNA-sequencing technology was used to detect transcriptome changes after 25(OH)D treatment and tRF-1-Ser knockdown. RNA pull-down and high-performance liquid chromatography-mass spectrometry/mass spectrometry were used to explore the proteins bound to tRF-1-Ser. In vitro and in vivo functional experiments were conducted to assess the influence of 25(OH)D and tRF-1-Ser on breast cancer. Semi-quantitative PCR was performed to detect alternative splicing events. Western blot assay and qPCR were used to assess protein and mRNA expression.

RESULTS

The expression of tRF-1-Ser is negatively regulated by 25(OH)D. In our breast cancer (BRCA) clinical samples, we found that the expression of tRF-1-Ser was higher in cancer tissues than in paired normal tissues, and was significantly associated with tumour invasion. Moreover, tRF-1-Ser inhibits the function of MBNL1 by hindering its nuclear translocation. Functional experiments and transcriptome data revealed that the downregulation of tRF-1-Ser plays a vital role in the anticancer effect of 25(OH)D.

CONCLUSIONS

In brief, our research revealed a novel anticancer mechanism of 25(OH)D, unveiled the vital function of tRF-1-Ser in BRCA progression, and suggested that tRF-1-Ser could emerge as a new therapeutic target for BRCA.

Harnessing the potential of long non-coding RNAs in breast cancer: from etiology to treatment resistance and clinical applications

Breast cancer (BC) is the most common malignancy among women and a leading cause of cancer-related deaths of females worldwide. It is a complex and molecularly heterogeneous disease, with various subtypes that require different treatment strategies. Despite advances in high-resolution single-cell and multinomial technologies, distant metastasis and therapeutic resistance remain major challenges for BC treatment. Long non-coding RNAs (lncRNAs) are non-coding RNAs with more than 200 nucleotides in length. They act as competing endogenous RNAs (ceRNAs) to regulate post-transcriptional gene stability and modulate protein-protein, protein-DNA, and protein-RNA interactions to regulate various biological processes. Emerging evidence suggests that lncRNAs play essential roles in human cancers, including BC. In this review, we focus on the roles and mechanisms of lncRNAs in BC progression, metastasis, and treatment resistance, and discuss their potential value as therapeutic targets. Specifically, we summarize how lncRNAs are involved in the initiation and progression of BC, as well as their roles in metastasis and the development of therapeutic resistance. We also recapitulate the potential of lncRNAs as diagnostic biomarkers and discuss their potential use in personalized medicine. Finally, we provide lncRNA-based strategies to promote the prognosis of breast cancer patients in clinical settings, including the development of novel lncRNA-targeted therapies.

A promising target for breast cancer: B7-H3

Breast cancer (BC) is the second-leading factor of mortality for women globally and is brought on by a variety of genetic and environmental causes. The conventional treatments for this disease have limitations, making it difficult to improve the lifespan of breast cancer patients. As a result, extensive research has been conducted over the past decade to find innovative solutions to these challenges. Targeting of the antitumor immune response through the immunomodulatory checkpoint protein B7 family has revolutionized cancer treatment and led to intermittent patient responses. B7-H3 has recently received attention because of its significant demodulation and its immunomodulatory effects in many cancers. Uncontrolled B7-H3 expression and a bad outlook are strongly associated, according to a substantial body of cancer research. Numerous studies have shown that BC has significant B7-H3 expression, and B7-H3 induces an immune evasion phenotype, consequently enhancing the survival, proliferation, metastasis, and drug resistance of BC cells. Thus, an innovative target for immunotherapy against BC may be the B7-H3 checkpoint.In this review, we discuss the structure and regulation of B7-H3 and its double costimulatory/coinhibitory function within the framework of cancer and normal physiology. Then we expound the malignant behavior of B7-H3 in BC and its role in the tumor microenvironment (TME) and finally focus on targeted drugs against B7-H3 that have opened new therapeutic opportunities in BC.

The crucial role of fascin-1 in the pathogenesis, metastasis, and chemotherapeutic resistance of breast cancer

Breast cancer (BC) is the most common type of cancer in women to be diagnosed, and it is also the second leading cause of cancer death in women globally. It is the disease that causes the most life years adjusted for disability lost among women, making it a serious worldwide health issue. Understanding and interpreting carcinogenesis and metastatic pathways is critical for curing malignancy. Fascin-1 was recognized as an actin-bundling protein with parallel, rigid bundles as a result of the cross-linking of F-actin microfilaments. Increasing levels of fascin-1 have been associated with bad prognostic profiles, aggressiveness of clinical courses, and poor survival outcomes in a variety of human malignancies. Cancer cells that overexpress fascin-1 have higher capabilities for proliferation, invasion, migration, and metastasis. Fascin-1 is being considered as a potential target for therapy as well as a potential biomarker for diagnostics in a variety of cancer types. This review aims to provide an overview of the FSCN1 gene and its protein structure, elucidate its physiological and pathological roles, and throw light on its involvement in the initiation, development, and chemotherapeutic resistance of BC.

Liposome-enabled bufalin and doxorubicin combination therapy for trastuzumab-resistant breast cancer with a focus on cancer stem cells

Breast cancer stem cells (BCSCs) play a key role in therapeutic resistance in breast cancer treatments and disease recurrence. This study aimed to develop a combination therapy loaded with pH-sensitive liposomes to kill both BCSCs and the okbulk cancer cells using trastuzumab-sensitive and resistant human epidermal growth factor receptor 2 positive (HER2+) breast cancer cell models. The anti-BCSCs effect and cytotoxicity of all-trans retinoic acid, salinomycin, and bufalin alone or in combination with doxorubicin were compared in HER2+ cell line BT-474 and a validated trastuzumab-resistant cell line, BT-474R. The most potent anti-BCSC agent was selected and loaded into a pH-sensitive liposome system. The effects of the liposomal combination on BCSCs and bulk cancer cells were assessed. Compared with BT-474, the aldehyde dehydrogenase positive BCSC population was elevated in BT-474R (3.9 vs. 23.1%). Bufalin was the most potent agent and suppressed tumorigenesis of BCSCs by ∼50%, and showed strong synergism with doxorubicin in both BT-474 and BT-474R cell lines. The liposomal combination of bufalin and doxorubicin significantly reduced the BCSC population size by 85%, and inhibited both tumorigenesis and self-renewal, although it had little effect on the migration and invasiveness. The cytotoxicity against the bulk cancer cells was also enhanced by the liposomal combination than either formulation alone in both cell lines (p < 0.001). The liposomal bufalin and doxorubicin combination therapy may effectively target both BCSCs and bulk cancer cells for a better outcome in trastuzumab-resistant HER2+ breast cancer.

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

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

CD24hiCD27+ Bregs within Metastatic Lymph Nodes Promote Multidrug Resistance in Breast Cancer

PURPOSE

Axillary lymph nodes (LN) are the primary and dominant metastatic sites in breast cancer. However, the interaction between tumor cells and immune cells within metastatic LNs (mLN) remains poorly understood. In our study, we explored the effect of CD24hiCD27+ regulatory B cells (Breg) within mLNs on orchestrating drug resistance of breast cancer cells.

EXPERIMENTAL DESIGN

We collected mLN samples from patients with breast cancer who had received standard neoadjuvant therapy (NAT) and analyzed the spatial features of CD24hiCD27+ Bregs through multicolor immunofluorescence staining. The effect of CD24hiCD27+ Bregs on drug resistance of breast cancer cells was evaluated via in vitro experiments. A mouse model with mLNs was used to evaluate the strategies with blocking the interactions between Bregs and breast cancer for improving tumor regression within mLNs.

RESULTS

In patients with breast cancer who had received NAT, there is a close spatial correlation between activated CD24hiCD27+ Bregs and residual tumor cells within mLNs. Mechanistically, CD24hiCD27+ Bregs greatly enhance the acquisition of multidrug resistance and stem-like features of breast cancer cells by secreting IL6 and TNFα. More importantly, breast cancer cells further promote the activation of CD24hiCD27+ Bregs via CD40L-dependent and PD-L1-dependent proximal signals, forming a positive feedback pattern. PD-L1 blockade significantly attenuates the drug resistance of breast cancer cells induced by CD24hiCD27+ Bregs, and addition of anti-PD-L1 antibody to chemotherapy improves tumor cell remission in mLNs.

CONCLUSIONS

Our study reveals the pivotal role of CD24hiCD27+ Bregs in promoting drug resistance by interacting with breast cancer cells in mLNs, providing novel evidence for an improved strategy of chemoimmunotherapy combination for patients with breast cancer with mLNs.

Regulation and signaling pathways in cancer stem cells: implications for targeted therapy for cancer

Cancer stem cells (CSCs), initially identified in leukemia in 1994, constitute a distinct subset of tumor cells characterized by surface markers such as CD133, CD44, and ALDH. Their behavior is regulated through a complex interplay of networks, including transcriptional, post-transcriptional, epigenetic, tumor microenvironment (TME), and epithelial-mesenchymal transition (EMT) factors. Numerous signaling pathways were found to be involved in the regulatory network of CSCs. The maintenance of CSC characteristics plays a pivotal role in driving CSC-associated tumor metastasis and conferring resistance to therapy. Consequently, CSCs have emerged as promising targets in cancer treatment. To date, researchers have developed several anticancer agents tailored to specifically target CSCs, with some of these treatment strategies currently undergoing preclinical or clinical trials. In this review, we outline the origin and biological characteristics of CSCs, explore the regulatory networks governing CSCs, discuss the signaling pathways implicated in these networks, and investigate the influential factors contributing to therapy resistance in CSCs. Finally, we offer insights into preclinical and clinical agents designed to eliminate CSCs.

Single Cell Phenotypic Analysis for Cancer Stem Cell Identification by Dual-Isotope ICP-QMS

Single cell phenotypic analysis is significant for clinical diagnosis, treatment, and prognosis of cancer. Accurate differentiation of cancer stem cell (CSC) subpopulations from a large number of cancer cells may become a cancer surveillance tool and provide important implications for the development of new CSC-targeted therapy strategies. Herein, we report a new approach based on dual-isotope inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) for single cell phenotypic analysis. High-throughput single cell sampling was achieved by a spiral channel microfluidic chip for cell focusing and alignment, and single cell analysis was performed with time-resolved ICP-QMS by identifying the highly specific probes. This enables the monitoring of two surface protein markers (EpCAM and MUC1) of three cell types, i.e., HeLa, MCF-7, and HepG2, at single cell level. The analysis of breast cancer stem cells further confirmed its capability in distinguishing rare cell phenotypes. The present study provides promising possibilities for adopting ICP-QMS in biomedical investigations in terms of cell typing, stemness identification of tumor cells, and cell heterogeneity analysis.

NFAT signaling dysregulation in cancer: Emerging roles in cancer stem cells

The nuclear factor of activated T cells (NFAT) was first identified as a transcriptional regulator of activated T cells. The NFAT family is involved in the development of tumors. Furthermore, recent evidence reveals that NFAT proteins regulate the development of inflammatory and immune responses. New discoveries have also been made about the mechanisms by which NFAT regulates cancer progression through cancer stem cells (CSC). Here, we discuss the role of the NFAT family in the immune system and various cancer types.

SPDEF enhances cancer stem cell-like properties and tumorigenesis through directly promoting GALNT7 transcription in luminal breast cancer

BACKGROUND

Luminal breast cancer (BC) is the predominant subtype of breast cancer with a sustained risk of late recurrence and death. Understanding the molecular mechanisms for the oncogenesis of luminal BC would improve the prognosis for this large subset of patients. SPDEF was reported to be dysregulated in breast cancers. However, the biological functions and underlying molecular mechanism of SPDEF in luminal BC remains largely unknown. The aim of the present study was to elucidate the potential roles of SPDEF underlying subtype-specific functions in BC, especially in luminal subtypes.

METHODS

The expressions and clinicopathological characteristics of SPDEF in luminal BC patients were evaluated bioinformatically. In vitro and in vivo assays were performed to investigate the oncogenic function and stemness maintenance of SPDEF in luminal BC. Chromatin immunoprecipitation (ChIP) and dual luciferase reporter assays were conducted to determine the transcription regulation of GALNT7 by SPDEF. GALNT7 levels in serum from luminal BC patients were further detected by enzyme-linked immunosorbent assay (ELISA).

RESULTS

SPDEF is markedly upregulated in luminal BC and positively associated with tumor progression and poor prognosis. Furthermore, we confirmed that SPDEF enhanced the proliferation, migration, invasion and stemness of luminal BC cells in vitro as well the tumorigenicity in vivo. Mechanistically, we demonstrated the stimulative effect of SPDEF on the progression and stemness of luminal BC, which is mediated by its directly transcriptional target GALNT7. Clinically, we verified that the GALNT7 can be used as a noninvasive diagnostic marker. Noteworthy, the combined detection of serum GALNT7 and traditional tumor markers can enhance diagnostic accuracy thus is of vital importance in the early diagnosis of luminal BC.

CONCLUSIONS

Our study reveals a novel mechanism by which SPDEF transcriptionally activates GALNT7 via directly binding to its promoter to promote cell proliferation, motility and stemness, and led to luminal BC tumorigenesis and poor prognosis.

Cancer stem cells promote lymph nodes metastasis of breast cancer by reprogramming tumor microenvironment

Breast cancer progression and metastasis are governed by a complex interplay within the tumor immune microenvironment (TIME), involving numerous cell types. Lymph node metastasis (LNM) is a key prognostic marker associated with distant organ metastasis and reduced patient survival, but the mechanisms underlying its promotion by breast cancer stem cells (CSCs) remain unclear. Our study sought to unravel how CSCs reprogram TIME to facilitate LNM. Utilizing single-cell RNA sequencing, we profiled TIME in primary cancer and corresponding metastatic lymph node samples from patients at our institution. To verify the derived data, we cultured CSCs and performed validation assays employing flow cytometry and CyTOF. Our analysis revealed distinct differences in cellular infiltration patterns between tumor and LNM samples. Importantly, RAC2 and PTTG1 double-positive CSCs, which exhibit the highest stem-like attributes, were markedly enriched in metastatic lymph nodes. These CSCs are hypothesized to foster metastasis via activation of specific metastasis-related transcription factors and signaling pathways. Additionally, our data suggest that CSCs might modulate adaptive and innate immune cell evolution, thereby further contributing to metastasis. In summary, this study illuminates a critical role of CSCs in modifying TIME to facilitate LNM. The enrichment of highly stem-like CSCs in metastatic lymph nodes offers novel therapeutic targeting opportunities and deepens our understanding of breast cancer metastasis.

Vaccines in Breast Cancer: Challenges and Breakthroughs

Breast cancer is a problem for women's health globally. Early detection techniques come in a variety of forms ranging from local to systemic and from non-invasive to invasive. The treatment of cancer has always been challenging despite the availability of a wide range of therapeutics. This is either due to the variable behaviour and heterogeneity of the proliferating cells and/or the individual's response towards the treatment applied. However, advancements in cancer biology and scientific technology have changed the course of the cancer treatment approach. This current review briefly encompasses the diagnostics, the latest and most recent breakthrough strategies and challenges, and the limitations in fighting breast cancer, emphasising the development of breast cancer vaccines. It also includes the filed/granted patents referring to the same aspects.

Managing a Long and Winding Road: Estrogen Receptor-Positive Breast Cancer

We review key topics in the management of estrogen receptor (ER)-positive human epidermal growth factor receptor 2-negative breast cancer. The single biggest challenge in management of this disease is late relapse, and we review new methods for identifying which patients are at risk of late relapse and potential therapeutic approaches in clinical trials. CDK4/6 inhibitors have become a standard treatment option for high-risk patients in both the adjuvant setting and the first-line metastatic setting, and we review data on optimal treatment after progression on CDK4/6 inhibitors. Targeting the estrogen receptor remains the single most effective way of targeting the cancer, and we review the developments in new oral selective ER degraders that are becoming a standard of care in cancers with ESR1 mutations and potential future directions.

Analysis of Differential Gene Expression and Core Canonical Pathways Involved in the Epithelial to Mesenchymal Transition of Triple Negative Breast Cancer Cells by Ingenuity Pathway Analysis

Triple Negative Breast Cancer (TNBC) is a malignant form of cancer with very high mortality and morbidity. Epithelial to Mesenchymal Transition (EMT) is the most common pathophysiological change observed in cancer cells of epithelial origin that promotes metastasis, drug resistance and cancer stem cell formation. Since the information regarding differential gene expression in TNBC cells and cell signaling events leading to EMT is limited, this investigation was done by comparing transcriptomic data generated by RNA isolation and sequencing of a EMT model TNBC cell line in comparison to regular TNBC cells. RNA sequencing and Ingenuity Pathway Software Analysis (IPA) of the transcriptomic data revealed several upregulated and downregulated gene expressions along with novel core canonical pathways including Sirtuin signaling, Oxidative Phosphorylation and Mitochondrial dysfunction events involved in EMT changes of the TNBC cells.

Downregulation of the long noncoding RNA DSCR9 (Down syndrome critical region 9) delays breast cancer progression by modulating microRNA-504-5p-dependent G protein-coupled receptor 65

Possible roles of long noncoding RNAs (lncRNAs) in cancer stem cells (CSCs) have often been reported. Here, we focused on the regulatory function of the lncRNA Down syndrome critical region 9 (DSCR9) in breast cancer stem cells (BCSCs). Through bioinformatics analysis, DSCR9, microRNA-504-5p (miR-504-5p), and G protein-coupled receptor 65 (GPR65) were identified as targets implicated in breast cancer development. Then, clinical tissue samples, breast cancer cells, and isolated BCSCs were used to determine the expression of DSCR9, miR-504-5p, and GPR65. The results confirmed the overexpression of DSCR9 and GPR65 but low expression of miR-504-5p in breast cancer tissues and cells as well as in BCSCs. Following mechanistic investigation, it was found that DSCR9 targeted miR-504-5p, and that silencing DSCR9 inhibited the proliferation of BCSCs by elevating the expression of miR-504-5p. Additionally, miR-504-5p targeted GPR65 and inhibited its expression. Moreover, GPR65 activated the MEK/ERK signaling pathway to regulate BCSC proliferation. Finally, animal study verified that depletion of DSCR9 inhibited the proliferation of BCSCs in vivo and that BCSC proliferation was restored by overexpression of GPR65. Altogether, our findings revealed that DSCR9 elevated GPR65 expression by targeting miR-504-5p to exacerbate breast cancer, highlighting a new treatment modality for breast cancer.

Role of Escin in breast cancer therapy: potential mechanism for inducing ferroptosis and synergistic antitumor activity with cisplatin

Breast cancer (BC) has threatened women worldwide for a long time, and novel treatments are needed. Ferroptosis is a new form of regulated cell death that is a potential therapeutic target for BC. In this study, we identified Escin, a traditional Chinese medicine, as a possible supplement for existing chemotherapy strategies. Escin inhibited BC cell growth in vitro and in vivo, and ferroptosis is probable to be the main cause for Escin-induced cell death. Mechanistically, Escin significantly downregulated the protein level of GPX4, while overexpression of GPX4 could reverse the ferroptosis triggered by Escin. Further study revealed that Escin could promote G6PD ubiquitination and degradation, thus inhibiting the expression of GPX4 and contributing to the ferroptosis. Moreover, proteasome inhibitor MG132 or G6PD overexpression could partially reverse Escin-induced ferroptosis, when G6PD knockdown aggravated that. In vivo study also supported that downregulation of G6PD exacerbated tumor growth inhibition by Escin. Finally, our data showed that cell apoptosis was dramatically elevated by Escin combined with cisplatin in BC cells. Taken together, these results suggest that Escin inhibits tumor growth in vivo and in vitro via regulating the ferroptosis mediated by G6PD/GPX4 axis. Our findings provide a promising therapeutic strategy for BC.

eIF2Bδ blocks the integrated stress response and maintains eIF2B activity and cancer metastasis by overexpression in breast cancer stem cells

Breast cancer (BC) metastasis involves cancer stem cells (CSCs) and their regulation by micro-RNAs (miRs), but miR targeting of the translation machinery in CSCs is poorly explored. We therefore screened miR expression levels in a range of BC cell lines, comparing non-CSCs to CSCs, and focused on miRs that target translation and protein synthesis factors. We describe a unique translation regulatory axis enacted by reduced expression of miR-183 in breast CSCs, which we show targets the eIF2Bδ subunit of guanine nucleotide exchange factor eIF2B, a regulator of protein synthesis and the integrated stress response (ISR) pathway. We report that reduced expression of miR-183 greatly increases eIF2Bδ protein levels, preventing strong induction of the ISR and eIF2α phosphorylation, by preferential interaction with P-eIF2α. eIF2Bδ overexpression is essential for BC cell invasion, metastasis, maintenance of metastases, and breast CSC expansion in animal models. Increased expression of eIF2Bδ, a site of action of the drug ISRIB that also prevents ISR signaling, is essential for breast CSC maintenance and metastatic capacity.

Natural product Eriocalyxin B suppressed triple negative breast cancer metastasis both in vitro and in vivo

Breast cancer is the most commonly diagnosed cancer among women, and its metastasis to distant organs accounts for the majority of death. Eriocalyxin B (Eri B), an ent-kaurane diterpenoid isolating from Isodon eriocalyx var. laxiflora, has previously been reported to have anti-tumor and anti-angiogenic effects in breast cancer. Here, we investigated the effect of Eri B on cell migration and adhesion in triple negative breast cancer (TNBC) cells, as well as aldehyde dehydrogenases 1 family member A1 (ALDH1A1) expression, colony- and sphere-formation in cancer stem cell (CSC) enriched MDA-MB-231 cells. The in vivo anti-metastatic activities of Eri B were determined in 3 different breast tumor-bearing mouse models. Our results indicated that Eri B inhibited TNBC cell migration and adhesion to extracellular matrix proteins, and also reduced ALDH1A1 expression and colony formation in CSC-enriched MDA-MB-231 cells. The metastasis-related pathways, such as epidermal growth factor receptor/ mitogen-activated protein kinase kinases 1/2/ extracellular regulated protein kinase signaling altered by Eri B was firstly shown in MDA-MB-231 cells. The potent anti-metastatic efficacies of Eri B were demonstrated in breast xenograft-bearing mice and syngeneic breast tumor-bearing mice. Gut microbiome analysis results revealed the change in the diversity and composition of microbiome after Eri B treatment, and the potential pathways that are involved in the anti-cancer efficacy of Eri B. In conclusion, Eri B was shown to inhibit breast cancer metastasis in both in vitro and in vivo models. Our findings further support the development of Eri B as an anti-metastatic agent for breast cancer.

Targeting KK-LC-1 inhibits malignant biological behaviors of triple-negative breast cancer

BACKGROUND

Cancer/testis antigens (CTAs) participate in the regulation of malignant biological behaviors in breast cancer. However, the function and mechanism of KK-LC-1, a member of the CTA family, in breast cancer are still unclear.

METHODS

Bioinformatic tools, immunohistochemistry, and western blotting were utilized to detect the expression of KK-LC-1 in breast cancer and to explore the prognostic effect of KK-LC-1 expression in breast cancer patients. Cell function assays, animal assays, and next-generation sequencing were utilized to explore the function and mechanism of KK-LC-1 in the malignant biological behaviors of triple-negative breast cancer. Small molecular compounds targeting KK-LC-1 were also screened and drug susceptibility testing was performed.

RESULTS

KK-LC-1 was significantly highly expressed in triple-negative breast cancer tissues than in normal breast tissues. KK-LC-1 high expression was related to poor survival outcomes in patients with breast cancer. In vitro studies suggested that KK-LC-1 silencing can inhibit triple-negative breast cancer cell proliferation, invasion, migration, and scratch healing ability, increase cell apoptosis ratio, and arrest the cell cycle in the G0-G1 phase. In vivo studies have suggested that KK-LC-1 silencing decreases tumor weight and volume in nude mice. Results showed that KK-CL-1 can regulate the malignant biological behaviors of triple-negative breast cancer via the MAL2/MUC1-C/PI3K/AKT/mTOR pathway. The small-molecule compound Z839878730 had excellent KK-LC-1 targeting ability and cancer cell killing ability. The EC₅₀ value was 9.7 μM for MDA-MB-231 cells and 13.67 µM for MDA-MB-468 cells. Besides, Z839878730 has little tumor-killing effect on human normal mammary epithelial cells MCF10A and can inhibit the malignant biological behaviors of triple-negative breast cancer cells by MAL2/MUC1-C/PI3K/AKT/mTOR pathway.

CONCLUSIONS

Our findings suggest that KK-LC-1 may serve as a novel therapeutic target for triple-negative breast cancer. Z839878730, which targets KK-LC-1, presents a new path for breast cancer clinical treatment.

PMN-MDSCs modulated by CCL20 from cancer cells promoted breast cancer cell stemness through CXCL2-CXCR2 pathway

Our previous studies have showed that C-C motif chemokine ligand 20 (CCL20) advanced tumor progression and enhanced the chemoresistance of cancer cells by positively regulating breast cancer stem cell (BCSC) self-renewal. However, it is unclear whether CCL20 affects breast cancer progression by remodeling the tumor microenvironment (TME). Here, we observed that polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) were remarkably enriched in TME of CCL20-overexpressing cancer cell orthotopic allograft tumors. Mechanistically, CCL20 activated the differentiation of granulocyte-monocyte progenitors (GMPs) via its receptor C-C motif chemokine receptor 6 (CCR6) leading to the PMN-MDSC expansion. PMN-MDSCs from CCL20-overexpressing cell orthotopic allograft tumors (CCL20-modulated PMN-MDSCs) secreted amounts of C-X-C motif chemokine ligand 2 (CXCL2) and increased ALDH⁺ BCSCs via activating CXCR2/NOTCH1/HEY1 signaling pathway. Furthermore, C-X-C motif chemokine receptor 2 (CXCR2) antagonist SB225002 enhanced the docetaxel (DTX) effects on tumor growth by decreasing BCSCs in CCL20^high-expressing tumors. These findings elucidated how CCL20 modulated the TME to promote cancer development, indicating a new therapeutic strategy by interfering with the interaction between PMN-MDSCs and BCSCs in breast cancer, especially in CCL20^high-expressing breast cancer.

Comprehensive Analysis of the Expression and Prognosis of chromobox Family Members in Breast Cancer

BACKGROUND

Chromobox proteins are canonical components of the Polycomb group family and play pivotal roles in several cancers. However, little is known about the function, prognostic value and drug sensitivity of CBX family members in breast cancer.

METHODS

In this study we investigated the expression, prognosis value and drug sensitivity of CBX family in breast cancer using the ONCOMINE, GEPIA, Human Protein Atlas and Kaplan-Meier Plotter databases, etc. and preliminary verified the expression of CBX family in breast cancer cell lines by RT-qPCR.

RESULTS

We found that the expression levels of CBX1/2/3/4/8 members were elevated in breast cancer tissues compared to adjacent normal breast tissues, while the expression levels of CBX6/7 genes were reduced in breast cancer tissue. In vitro qRT-PCR validated the expression differences of CBX1/2/3/4/8 in breast cancer cell lines. Further analysis showed expression of CBX family members was remarkably correlated with cancer subgroups. As nodal metastasis status increased, the mRNA expression of CBX1/2/3/4/8 members tended to be higher, while CBX6/7 tended to be lower. The expression of CBX1/2/3 was higher in patients with TP53 mutation and CBX6/7 expression tended to be lower in patients with TP53 mutation groups. High transcription levels of CBX2/3 were significantly associated with shorter overall survival in breast cancer patients, while lower expression of CBX4/5/6/7 members was associated with unfavorable overall survival. Moreover, a high mutation rate of CBX gene members (43%) was observed in breast cancer patients, and genetic alterations in CBX genes was associated with poor prognosis.

CONCLUSION

Taken together, our results indicated that CBX2/3/6/7/8 could be considered prognostic and therapeutic biomarkers of breast cancer and are worthy of further study.

Hydroxyethyl starch-folic acid conjugates stabilized theranostic nanoparticles for cancer therapy

Small molecular prodrug-based nanomedicines with high drug-loading efficiency and tumor selectivity have attracted great attention for cancer therapy against solid tumors, including triple negative breast cancers (TNBC). However, abnormal tumor mechanical microenvironment (TMME) severely restricts antitumor efficacy of prodrug nanomedicines by limiting drug delivery and fostering cancer stem cells (CSCs). Herein, we employed carbamate disulfide bridged doxorubicin dimeric prodrug as pharmaceutical ingredient, marketed IR780 iodide as photothermal agent, and biocompatible hydroxyethyl starch-folic acid conjugates as amphiphilic surfactant to prepare a theranostic nanomedicine (FDINs), which could actively target at TNBC 4T1 tumor tissues and achieve reduction-responsive drug release with high glutathione concentration in cancer cells and CSCs. Importantly, in addition to directly causing damage to cancer cells and sensitizing chemotherapy, FDINs-mediated photothermal effect regulates aberrant TMME via reducing cancer associated fibroblasts and depleting extracellular matrix proteins, thereby normalizing intratumor vessel structure and function to facilitate drug and oxygen delivery. Furthermore, FDINs potently eliminate CSCs by disrupting unique CSCs niche and consuming intracellular GSH in CSCs. As a result, FDINs significantly suppress tumor growth in both subcutaneous and orthotopic 4T1 tumors. This study provides novel insights on rational design of prodrug nanomedicines for superior therapeutic effect against stroma- and CSCs-rich solid malignancies.

Selection hub MicroRNAs as biomarkers in breast cancer stem cells in extracellular matrix using bioinformatics analyses

Background

Breast cancer is one of the most common cancers in women, and many people get it every year. The cancer stem cells are maybe crucial role to exacerbates and relapse the breast cancer. Therefore, finding biomarkers in human secretions can be an suitable solution for early detection and neo adjuvant therapy. This study aimed to investigate the molecular events related to the cancer stem cells in breast cancer, after which we nominated a suitable MicroRNAs participates in breast cancer pathogenesis.

Methods

In this study, we investigated the relationship between molecular pathways using a bioinformatics approach. First, we selected the appropriate RNA-Seq datasets from the GEO database. We used Enrichr, KEGG, and Shiny GO databases to evaluate the signal pathways and gene ontology after isolating the gene expression profiles. In the next step, we used the STRING database to assess the protein network, and we used the Targetscan database to nominate the MicroRNA.

Results

510 high-expression genes and 460 low-expression genes were associated with breast cancer and the cancer stem cells. Highly expressed genes were involved in the cell cycle and cellular aging pathways. On the other hand, low-expression genes were involved in the RNA transports, spliceosome, and apoptosis pathways. After evaluating the ontology of genes and the relationship between proteins, high-expression SPARC, INHBA, FN1, and GBA proteins were nominated. In the next section, the MicroRNAs related to these genes were hsa miR-9.5p, hsa miR-203.3p, and hsa miR-429.

Conclusion

In general, we examined more closely and more the relationship between the cancer stem cells pathway and breast cancer using a regular and accurate bioinformatics framework. Finally, we nominated suitable MicroRNAs that were involved in breast cancer stem cells.

Comprehensive evaluation of breast cancer immunotherapy and tumor microenvironment characterization based on interleukin genes-related risk model

Breast cancer (BRCA) is the most prevalent malignancy and the leading cause of death in women. Interleukin (IL) genes are critical in tumor initiation and control. Nevertheless, the prognosis value of the IL in BRCA remains unclear. We collected data from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO), and 94 IL genes were identified from GeneCard. Based on the random forest (RF), least absolute shrinkage and selection operator (LASSO) analysis, and multivariate Cox regression analysis, we constructed an IL signature. GSE22219, GSE25065, and GSE21653 were derived as validation sets. The expression differences in the tumor microenvironment (TME), immunotherapy, and chemosensitivity of BRCA between the high- and low-risk groups were evaluated. Overall, 21 IL genes were selected to construct an IL risk model, of which IL18BP, IL17D, and IL23A were the first time identified as prognostic genes in BRCA. IL score could distinguish BRCA patients with inferior outcomes, and AUC of it was 0.70, 0.76, and 0.72 for 1-,3- and 5- years, respectively, which was also verified in GSE22219, GSE25065, and GSE21653 cohorts. Meanwhile, compared to luminal A and luminal B, HER2-positive and TNBC had significantly higher IL score. Besides, the high-risk group had a significantly higher prevalence of TP53 and TTN but a lower prevalence of PIK3CA, as well as higher tumor mutation burden (TMB) and neoantigen level. High- and low-risk groups exhibited notable differences in immunomodulators and tumor infiltrates immune cells (TIICs), and the high-risk group had significantly lower Tumor Immune Dysfunction and Exclusion (TIDE) score. Additionally, the high-risk group has more responders to immune or anti-HER2 combination therapy, whereas the low-risk group has higher sensitivity to docetaxel and paclitaxel. Consequently, we constructed a reliable risk model based on the IL genes, which can provide more information on both the risk stratification and personalizing management strategies for BRCA.

Advances in Biomarkers and Endogenous Regulation of Breast Cancer Stem Cells

Breast cancer is one of the most common cancers. Even if breast cancer patients initially respond to treatment, developed resistance can lead to a poor prognosis. Cancer stem cells (CSCs) are a group of undifferentiated cells with self-renewal and multipotent differentiation characteristics. Existing evidence has shown that CSCs are one of the determinants that contribute to the heterogeneity of primary tumors. The emergence of CSCs causes tumor recurrence, metastasis, and therapeutic resistance. Previous studies indicated that different stemness-associated surface markers can identify other breast cancer stem cell (BCSC) subpopulations. Deciphering the critical signaling networks that are involved in the induction and maintenance of stemness is essential to develop novel BCSC-targeting strategies. In this review, we reviewed the biomarkers of BCSCs, critical regulators of BCSCs, and the signaling networks that regulate the stemness of BCSCs.

MTH1 suppression enhances the stemness of MCF7 through upregulation of STAT3

MTH1 protein can sanitize the damaged (d)NTP pool and MTH1 inhibitors have been developed to impede the growth of rapidly proliferating tumor cells; however, the effect of MTH1 inhibition on breast cancer stemness has not been reported yet. Here, we constructed breast cancer cell lines with the stable depletion of MTH1. MTH1 suppression clearly increased the ratio of CD44⁺CD24^-/low subpopulations and promoted the formation of tumorspheres in MCF7 and T47D cells. RNA expression profiling, RT-qPCR and Western blotting showed the upregulation of master stem cell transcription factors Sox2, Oct4 and Nanog in MTH1 knockdown cells. GSEA suggested and Western blotting verified that MTH1 knockdown increased the expression of phosphorylated STAT3 (Tyr705). Furthermore, we indirectly demonstrated that the increased concentration of 8-oxo-dGTP and 8-oxo-GTP in MTH1-knockdown cells and exogenous 8-oxoGTP, rather than 8-oxo-dGTP, could significantly increase the phosphorylation of STAT3. In conclusion, this work indicates that MTH1 inhibition increased the proportion of breast cancer stem cells (BCSCs) and promoted stemness properties in MCF7 cells.

Addiction of Cancer Stem Cells to MUC1-C in Triple-Negative Breast Cancer Progression

Triple-negative breast cancer (TNBC) is an aggressive malignancy with limited treatment options. TNBC progression is associated with expansion of cancer stem cells (CSCs). Few insights are available regarding druggable targets that drive the TNBC CSC state. This review summarizes the literature on TNBC CSCs and the compelling evidence that they are addicted to the MUC1-C transmembrane protein. In normal epithelia, MUC1-C is activated by loss of homeostasis and induces reversible wound-healing responses of inflammation and repair. However, in settings of chronic inflammation, MUC1-C promotes carcinogenesis. MUC1-C induces EMT, epigenetic reprogramming and chromatin remodeling in TNBC CSCs, which are dependent on MUC1-C for self-renewal and tumorigenicity. MUC1-C-induced lineage plasticity in TNBC CSCs confers DNA damage resistance and immune evasion by chronic activation of inflammatory pathways and global changes in chromatin architecture. Of therapeutic significance, an antibody generated against the MUC1-C extracellular domain has been advanced in a clinical trial of anti-MUC1-C CAR T cells and in IND-enabling studies for development as an antibody–drug conjugate (ADC). Agents targeting the MUC1-C cytoplasmic domain have also entered the clinic and are undergoing further development as candidates for advancing TNBC treatment. Eliminating TNBC CSCs will be necessary for curing this recalcitrant cancer and MUC1-C represents a promising druggable target for achieving that goal.

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.

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.

Fucoxanthin Is a Potential Therapeutic Agent for the Treatment of Breast Cancer

Breast cancer (BC) is one of the most common cancers diagnosed and the leading cause of cancer-related death in women. Although there are first-line treatments for BC, drug resistances and adverse events have been reported. Given the incidence of BC keeps increasing, seeking novel therapeutics is urgently needed. Fucoxanthin (Fx) is a dietary carotenoid commonly found in seaweeds and diatoms. Both in vitro and in vivo studies show that Fx and its deacetylated metabolite fucoxanthinol (Fxol) inhibit and prevent BC growth. The NF-κB signaling pathway is considered the major pathway contributing to the anti-proliferation, anti-angiogenesis and pro-apoptotic effects of Fx and Fxol. Other signaling molecules such as MAPK, MMP2/9, CYP and ROS are also involved in the anti-cancer effects by regulating the tumor microenvironment, cancer metastasis, carcinogen metabolism and oxidation. Besides, Fx also possesses anti-obesity effects by regulating UCP1 levels and lipid metabolism, which may help to reduce BC risk. More importantly, mounting evidence demonstrates that Fx overcomes drug resistance. This review aims to give an updated summary of the anti-cancer effects of Fx and summarize the underlying mechanisms of action, which will provide novel strategies for the development of Fx as an anti-cancer therapeutic agent.

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.

Disruption of ZNF334 promotes triple-negative breast carcinoma malignancy through the SFRP1/ Wnt/β-catenin signaling axis

Zinc-finger proteins (ZNFs) constitute the largest transcription factor family in the human genome. The family functions in many important biological processes involved in tumorigenesis. In our research, we identified ZNF334 as a novel tumor suppressor of triple-negative breast cancer (TNBC). ZNF334 expression was usually reduced in breast cancerv (BrCa) tissues and TNBC cell lines MDA-MB-231 (MB231) and YCCB1. We observed that promoter hypermethylation of ZNF334 was common in BrCa cell lines and tissues, which was likely responsible for its reduced expression. Ectopic expression of ZNF334 in TNBC cell lines MB231 and YCCB1 could suppress their growth and metastatic capacity both in vitro and in vivo, and as well induce cell cycle arrest at S phase and cell apoptosis. Moreover, re-expression of ZNF334 in TNBC cell lines could rescue Epithelial-Mesenchymal Transition (EMT) process and restrain stemness, due to up-regulation of SFRP1, which is an antagonist of Wnt/β-catenin signaling. In conclusion, we verified that ZNF334 had a suppressive function of TNBC cell lines by targeting the SFRP1/Wnt/β-catenin signaling axis, which might have the potentials to become a new biomarker for diagnosis and treatment of TNBC patients.

Beyond Immunosuppression: The Multifaceted Functions of Tumor-Promoting Myeloid Cells in Breast Cancers

Breast cancers are commonly associated with an immunosuppressive microenvironment responsible for tumor escape from anti-cancer immunity. Cells of the myeloid lineage account for a major part of this tumor-promoting landscape. These myeloid cells are composed of heterogeneous subsets at different stages of differentiation and have traditionally been described by their cardinal ability to suppress innate and adaptive anticancer immunity. However, evidence has accumulated that, beyond their immunosuppressive properties, breast cancer-induced myeloid cells are also equipped with a broad array of “non-immunological” tumor-promoting functions. They therefore represent major impediments for anticancer therapies, particularly for immune-based interventions. We herein analyze and discuss current literature related to the versatile properties of the different myeloid cell subsets engaged in breast cancer development. We critically assess persisting difficulties and challenges in unequivocally discriminate dedicated subsets, which has so far prevented both the selective targeting of these immunosuppressive cells and their use as potential biomarkers. In this context, we propose the concept of IMCGL, “pro-tumoral immunosuppressive myeloid cells of the granulocytic lineage”, to more accurately reflect the contentious nature and origin of granulocytic cells in the breast tumor microenvironment. Future research prospects related to the role of this myeloid landscape in breast cancer are further considered.

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.

Notch signaling pathway: architecture, disease, and therapeutics

The NOTCH gene was identified approximately 110 years ago. Classical studies have revealed that NOTCH signaling is an evolutionarily conserved pathway. NOTCH receptors undergo three cleavages and translocate into the nucleus to regulate the transcription of target genes. NOTCH signaling deeply participates in the development and homeostasis of multiple tissues and organs, the aberration of which results in cancerous and noncancerous diseases. However, recent studies indicate that the outcomes of NOTCH signaling are changeable and highly dependent on context. In terms of cancers, NOTCH signaling can both promote and inhibit tumor development in various types of cancer. The overall performance of NOTCH-targeted therapies in clinical trials has failed to meet expectations. Additionally, NOTCH mutation has been proposed as a predictive biomarker for immune checkpoint blockade therapy in many cancers. Collectively, the NOTCH pathway needs to be integrally assessed with new perspectives to inspire discoveries and applications. In this review, we focus on both classical and the latest findings related to NOTCH signaling to illustrate the history, architecture, regulatory mechanisms, contributions to physiological development, related diseases, and therapeutic applications of the NOTCH pathway. The contributions of NOTCH signaling to the tumor immune microenvironment and cancer immunotherapy are also highlighted. We hope this review will help not only beginners but also experts to systematically and thoroughly understand the NOTCH signaling pathway.

Chick Chorioallantoic Membrane (CAM) Assays as a Model of Patient-Derived Xenografts from Circulating Cancer Stem Cells (cCSCs) in Breast Cancer Patients

Simple Summary

Circulating cancer cells—and in particular their very rare subpopulation, circulating cancer stem cells (cCSCs)—are responsible for recurrence and metastasis. In this study, we present a novel process in which patient-derived xenograft (PDX) can be harvested on chorioallantoic membrane (CAM) from circulating cancer stem cells. In our opinion, the CAM-based PDX model using circulating cancer stem cells can provide a fast, low-cost, easy-to-use, and efficient preclinical platform for drug screening, therapy optimization, and biomarker discovery.

Abstract

Background: cCSCs are a small subset of circulating tumor cells with cancer stem cell features: resistance to cancer treatments and the capacity for generating metastases. PDX are an appreciated tool in oncology, providing biologically meaningful models of many cancer types, and potential platforms for the development of precision oncology approaches. Commonly, mouse models are used for the in vivo assessment of potential new therapeutic targets in cancers. However, animal models are costly and time consuming. An attractive alternative to such animal experiments is the chicken chorioallantoic membrane assay. Methods: In this study, primary cultures from cCSCs were established using the sphere-forming assay. Subsequently, tumorspheres were transplanted onto the CAM membrane of fertilized chicken eggs to form secondary microtumors. Results: We have developed an innovative in vitro platform for cultivation of cCSCs from peripheral blood of cancer patients. The number of tumorspheres increased significantly with tumor progression and aggressiveness of primary tumor. The number of tumorspheres was positively correlated with Ki-67, Her2 status, and grade score in primary breast tumors. The grafting of tumorspheres onto the CAM was successful and positively correlated with aggressiveness and proliferation capacity of the primary tumor. These tumors pathologically closely resembled the primary tumor. Conclusions: The number of tumorspheres cultured from peripheral blood and the success rate of establishing PDX directly reflect the aggressiveness and proliferation capacity of the primary tumor. A CAM-based PDX model using cCSC provides a fast, low-cost, easy to handle, and powerful preclinical platform for drug screening, therapy optimization, and biomarker discovery.

SIK2 maintains breast cancer stemness by phosphorylating LRP6 and activating Wnt/β-catenin signaling

Breast cancer stem cells (BCSCs) are the main drivers of recurrence and metastasis. However, commonly used drugs rarely target BCSCs. Via screenings, we found that Salt-inducible kinase 2 (SIK2) participated in breast cancer (BC) stemness maintenance and zebrafish embryos development. SIK2 was upregulated in recurrence samples. Knockdown of SIK2 expression reduced the proportion of BCSCs and the tumor initiation of BC cells. Mechanistically, SIK2, phosphorylated by CK1α, directly phosphorylated LRP6 in a SIK2 kinase activity-dependent manner, leading to Wnt/β-catenin signaling pathway activation. ARN-3236 and HG-9-91-01, inhibitors of SIK2, inhibited LRP6 phosphorylation and β-catenin accumulation and disturbed stemness maintenance. In addition, the SIK2-activated Wnt/β-catenin signaling led to induction of IDH1 expression, causing metabolic reprogramming in BC cells. These findings demonstrate a novel mechanism whereby Wnt/β-catenin signaling pathway is regulated by different kinases in response to metabolic requirement of CSCs, and suggest that SIK2 inhibition may potentially be a strategy for eliminating BCSCs.

DNA methyltransferase 1 inhibits microRNA-497 and elevates GPRC5A expression to promote chemotherapy resistance and metastasis in breast cancer

Background

Abnormal DNA methylation of tumor suppressor gene promoter has been found in breast cancer. Therefore, the current study set out to explore how DNA methyltransferase 1 (DNMT1) affects breast cancer through mediating miR-497/GPRC5A axis.

Methods

After loss and gain-of-function approaches were conducted in MCF-7/ADR and MCF-7 cells, cell viability, IC50 value, invasion, migration and apoptosis were measured, respectively. In addition, drug resistance, metastasis and apoptosis-related protein expression were examined using immunoblotting. ChIP and dual-luciferase reporter gene assays were carried out to validate relationship among DNMT1, miR-497, and GPRC5RA. Subcutaneous xenograft tumor model in nude mice was established to detect effects of DNMT1 on growth and metastasis of breast cancer in vivo.

Results

It was found that DNMT1 was notably increased, while miR-497 was poorly-expressed in breast cancer. Highly-expressed DNMT1 could promote chemotherapy resistance and metastasis of breast cancer. Meanwhile, DNMT1 modified methylation of CpG island in miR-497 promoter region, thereby repressing miR-497 level. In addition, miR-497 targeted GPRC5A expression to curb chemotherapy resistance and metastasis of breast cancer cells. Lastly, in vivo experiments showed that knockdown of DNMT1 could suppress breast cancer growth and metastasis.

Conclusions

Collectively, our findings indicated that DNMT1 may inhibit miR-497 and boost the expression of GPRC5A through methylation, thus augmenting breast cancer chemotherapy resistance and metastasis, which provides novel mechanistic insight into the unrecognized roles of DNMT1 in breast cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-022-02466-5.

Role of GD3 Synthase ST8Sia I in Cancers

Simple Summary

The carbohydrate moiety of cell surface glycolipids is modified in cancers of neuro–ectoderm origin, leading to the expression of more complex structures with two or more sialic acid residues. These alterations result from the upregulation of the ST8SIA1 gene that encodes GD3 synthase, the enzyme controlling the biosynthesis of complex gangliosides, and are usually associated with a more aggressive phenotype and a poor outcome for patients, making GD3 synthase an interesting target for cancer therapy. This review reports our general knowledge of GD3 synthase gene expression and regulation, its role in both epithelial–mesenchymal transition (EMT) and cancer progression, and the different approaches targeting GD3S expression in cancers.

Abstract

GD3 synthase controls the biosynthesis of complex gangliosides, bearing two or more sialic acid residues. Disialylated gangliosides GD3 and GD2 are tumor-associated carbohydrate antigens (TACA) in neuro–ectoderm-derived cancers, and are directly involved in cell malignant properties, i.e., migration, invasion, stemness, and epithelial–mesenchymal transition. Since GD3 and GD2 levels are directly linked to GD3 synthase expression and activity, targeting GD3 synthase appears to be a promising strategy through which to interfere with ganglioside-associated malignant properties. We review here the current knowledge on GD3 synthase expression and regulation in cancers, and the consequences of complex ganglioside expression on cancer cell signaling and properties, highlighting the relationships between GD3 synthase expression and epithelial–mesenchymal transition and stemness. Different strategies were used to modulate GD3 synthase expression in cancer cells in vitro and in animal models, such as inhibitors or siRNA/lncRNA, which efficiently reduced cancer cell malignant properties and the proportion of GD2 positive cancer stem cells, which are associated with high metastatic properties, resistance to therapy, and cancer relapse. These data show the relevance of targeting GD3 synthase in association with conventional therapies, to decrease the number of cancer stem cells in tumors.

UPF1 contributes to the maintenance of endometrial cancer stem cell phenotype by stabilizing LINC00963

Endometrial cancer stem cells (ECSCs) play a vital role in endometrial cancer (EC) metastasis, relapse, and chemoresistance. However, the molecular mechanisms that sustain ECSCs remain elusive. Here, we showed that the expression of UPF1 was upregulated in EC tissues and ECSCs and correlated with poor clinicopathological characteristics. UPF1 silencing suppressed ECSC hallmarks, such as sphere formation ability, carboplatin resistance, migration and invasion, and cell cycle progression. UPF1 regulated the behavior and fate of ECSCs by stabilizing LINC00963. LINC00963 further shares the same miRNA response element with the core transcription factor SOX2 and relieved the suppression of SOX2 by miR-508-5p in self-renewing ECSCs. Notably, inhibition of UPF1 and LINC00963 in combination severely impaired the in vivo tumorigenic potential of ECSCs. We demonstrate that the UPF1/LINC00963/miR-508-5p/SOX2 axis has potential value in modulating ECSC maintenance, chemoresistance, and tumorigenesis in EC, which highlights a novel promising target for EC treatment.

Psychological Distress, Coping Strategies, and Quality of Life in Breast Cancer Patients Under Neoadjuvant Therapy: Protocol of a Systematic Review

Introduction

Women with breast cancer eligible for neoadjuvant therapy (NAT) present a disorder of biopsychosocial variables and alteration of their quality of life. They cope with this changing by adopting psychological adjustment strategies, either passive or active. This systematic review aims to investigate the psychological distress, coping strategies, and quality of life in breast cancer patients under neoadjuvant therapy.

Methods

Cochrane Library, PubMed, ScienceDirect, Scopus, Web of Science, and Wiley Online library represent the databases that were searched to identify relevant published articles until September 27, 2021. Full-text published articles, written in English and assessing the main outcomes (namely: psychological distress, coping strategies, and quality of life) in women with breast cancer under NAT will be included. Also, we will integrate papers dealing with the related bio psychosocial variables to the main variables. The paper selection, data extraction, and quality assessment of selected studies will be performed independently by two researchers, and disagreements will be resolved through discussions. We will bring together the results of all of the included studies to draw conclusions based on the body of evidence. The narrative approach will be adopted to analyze the results and conclusions extracted and we would perform quantitative groupings if we have similar data.

Ethics and dissemination

Ethical approval is not required as the proposed systematic review will not use primary data. The results of this review will be disseminated through publication in a peer-reviewed journal and conference presentation(s). PROSPERO registration number: CRD42021230300.

Targeting Breast Cancer and Their Stem Cell Population through AMPK Activation: Novel Insights

Despite some significant advancements, breast cancer has become the most prevalent cancer in the world. One of the main reasons for failure in treatment and metastasis has been attributed to the presence of cancer initiating cells—cancer stem cells. Consequently, research is now being focussed on targeting cancer cells along with their stem cell population. Non-oncology drugs are gaining increasing attention for their potent anticancer activities. Metformin, a drug commonly used to treat type 2 diabetes, is the best example in this regard. It exerts its therapeutic action by activating 5′ adenosine monophosphate-activated protein kinase (AMPK). Activated AMPK subsequently phosphorylates and targets several cellular pathways involved in cell growth and proliferation and the maintenance of stem-like properties of cancer stem cells. Therefore, AMPK is emerging as a target of choice for developing effective anticancer drugs. Vanadium compounds are well-known PTP inhibitors and AMPK activators. They find extensive applications in treatment of diabetes and obesity via PTP1B inhibition and AMPK-mediated inhibition of adipogenesis. However, their role in targeting cancer stem cells has not been explored yet. This review is an attempt to establish the applications of insulin mimetic vanadium compounds for the treatment of breast cancer by AMPK activation and PTP1B inhibition pathways.

Ultrasound targeted microbubble destruction-mediated SOCS3 attenuates biological characteristics and epithelial-mesenchymal transition (EMT) of breast cancer stem cells

SOCS3 is low-expressed in breast cancer and may be a potential target. Ultrasound targeted microbubble destruction (UTMD) improved the efficiency of gene transfection. We explored the effects of UTMD-mediated transfection of SOCS3 on the biological characteristics and epithelial-mesenchymal transition (EMT) of breast cancer stem cells (BCSCs). The expression of SOCS3 in breast cancer (BC) and its association with prognosis were evaluated by GEPIA and The Cancer Genome Atlas (TCGA) websites. BCSCs were sorted by flow cytometry and immunomagnetic bead method, followed by sphere formation, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and xenograft assays to test their effects in vitro and in vivo. The levels of SOCS3, EMT- and STAT3 pathway-related genes were determined by RT-qPCR and Western blot, respectively. The effects of liposome and UTMD on BCSCs and mice were compared by the gain-of-function experiments. Low expression of SOCS3 was associated with poor prognosis of BC patients, and found in BC and BCSCs. BCSCs were successfully sorted, with high viability and tumorigenicity. UTMD increased the transfection rate of SOCS3. Moreover, UTMD- and liposome-mediated SOCS3 reduced cell viability, proliferation, migration and invasion, blocked cell cycle, inhibited sphere formation in BCSCs, and retarded tumor growth in mice. Mechanistically, overexpressed SOCS3 inhibited the expressions of EMT-related genes and the activation of STAT3 pathway in BCSCs and mice. The regulatory effects of UTMD-mediated SOCS3 on the above-mentioned biological characteristics were better than liposome-mediated SOCS3. UTMD-mediated SOCS3 has a better therapeutic effect in BC, providing new experimental evidence for the treatment of BC.

An Update on the Roles of circRNA-ZFR in Human Malignant Tumors

CircRNAs (circular RNAs) are single-stranded RNAs that form covalently closed loops and function as important regulatory elements of the genome through multiple mechanisms. Increasing evidence had indicated that circRNAs, which might serve as either oncogenes or tumor suppressors, played vital roles in the pathophysiology of human diseases, especially in tumorigenesis and progression. CircRNA-ZFR (circular RNA zinc finger RNA binding protein) is a circular RNA that had attracted much attention in recent years. It has been found that circRNA-ZFR was abnormally expressed in a variety of malignant tumors, and its dysregulated expression was closely related to tumor stage, cancer metastasis and patients’ prognosis. Recent studies had shown that aberrantly expressed circRNA-ZFR could regulate the malignant biological behaviors of tumors through various mechanisms; further exploration of circRNA-ZFR expression in tumors and its regulation on malignant biological behaviors such as tumor proliferation, invasion and drug resistance will provide new ideas for clinical tumors diagnosis and treatment.

KRT13 promotes stemness and drives metastasis in breast cancer through a plakoglobin/c-Myc signaling pathway

Background

Keratins (KRTs) are intermediate filament proteins that interact with multiple regulatory proteins to initiate signaling cascades. Keratin 13 (KRT13) plays an important role in breast cancer progression and metastasis. The objective of this study is to elucidate the mechanism by which KRT13 promotes breast cancer growth and metastasis.

Methods

The function and mechanisms of KRT13 in breast cancer progression and metastasis were assessed by overexpression and knockdown followed by examination of altered behaviors in breast cancer cells and in xenograft tumor formation in mouse mammary fat pad. Human breast cancer specimens were examined by immunohistochemistry and multiplexed quantum dot labeling analysis to correlate KRT13 expression to breast cancer progression and metastasis.

Results

KRT13-overexpressing MCF7 cells displayed increased proliferation, invasion, migration and in vivo tumor growth and metastasis to bone and lung. Conversely, KRT13 knockdown inhibited the aggressive behaviors of HCC1954 cells. At the molecular level, KRT13 directly interacted with plakoglobin (PG, γ-catenin) to form complexes with desmoplakin (DSP). This complex interfered with PG expression and nuclear translocation and abrogated PG-mediated suppression of c-Myc expression, while the KRT13/PG/c-Myc signaling pathway increased epithelial to mesenchymal transition and stem cell-like phenotype. KRT13 expression in 58 human breast cancer tissues was up-regulated especially at the invasive front and in metastatic specimens (12/18) (p < 0.05). KRT13 up-regulation in primary breast cancer was associated with decreased overall patient survival.

Conclusions

This study reveals that KRT13 promotes breast cancer cell growth and metastasis via a plakoglobin/c-Myc pathway. Our findings reveal a potential novel pathway for therapeutic targeting of breast cancer progression and metastasis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13058-022-01502-6.

Mapping Intellectual Structures and Research Hotspots of Triple Negative Breast Cancer: A Bibliometric Analysis

Background

Triple negative breast cancer (TNBC) is a highly heterogeneous breast cancer subtype with a poor prognosis due to its extremely aggressive nature and lack of effective treatment options. This study aims to summarize the current hotspots of TNBC research and evaluate the TNBC research trends, both qualitatively and quantitatively.

Methods

Scientific publications of TNBC-related studies from January 1, 2010 to October 17, 2020 were obtained from the Web of Science database. The BICOMB software was used to obtain the high-frequency keywords layout. The gCLUTO was used to produce a biclustering analysis on the binary matrix of word-paper. The co-occurrence and collaboration analysis between authors, countries, institutions, and keywords were performed by VOSviewer software. Keyword burst detection was performed by CiteSpace.

Results

A total of 12,429 articles related to TNBC were identified. During 2010-2020, the most productive country/region and institution in TNBC field was the USA and The University of Texas MD Anderson Cancer Center, respectively. Cancer Research, Journal of Clinical Oncology, and Annals of Oncology were the first three periodicals with maximum publications in TNBC research. Eight research hotspots of TNBC were identified by co-word analysis. In the core hotspots, research on neoadjuvant chemotherapy, paclitaxel therapy, and molecular typing of TNBC is relatively mature. Research on immunotherapy and PARP inhibitor for TNBC is not yet mature but is the current focus of this field. Burst detection of keywords showed that studies on TNBC proteins and receptors, immunotherapy, target, and tumor cell migration showed bursts in recent three years.

Conclusion

The current study revealed that TNBC studies are growing. Attention should be paid to the latest hotspots, such as immunotherapy, PARP inhibitors, target, and TNBC proteins and receptors.