NOTCH1 inhibition in vivo results in mammary tumor regression and reduced mammary tumorsphere-forming activity in vitro

Chromosome evolution screens recapitulate tissue-specific tumor aneuploidy patterns

Whole chromosome and arm-level copy number alterations occur at high frequencies in tumors, but their selective advantages, if any, are poorly understood. Here, utilizing unbiased whole chromosome genetic screens combined with in vitro evolution to generate arm- and subarm-level events, we iteratively selected the fittest karyotypes from aneuploidized human renal and mammary epithelial cells. Proliferation-based karyotype selection in these epithelial lines modeled tissue-specific tumor aneuploidy patterns in patient cohorts in the absence of driver mutations. Hi-C-based translocation mapping revealed that arm-level events usually emerged in multiples of two via centromeric translocations and occurred more frequently in tetraploids than diploids, contributing to the increased diversity in evolving tetraploid populations. Isogenic clonal lineages enabled elucidation of pro-tumorigenic mechanisms associated with common copy number alterations, revealing Notch signaling potentiation as a driver of 1q gain in breast cancer. We propose that intrinsic, tissue-specific proliferative effects underlie tumor copy number patterns in cancer.

Breast cancer stem cells as novel biomarkers

Breast cancer is the most common cancer and the leading cause of mortality worldwide. Despite advancements in detection and treatment, it remains a major cause of cancer-related deaths in women. Breast cancer stem cells (BCSCs) are a crucial group of cells responsible for carcinogenesis, metastasis, medication resistance, and tumor recurrence. Identifying and understanding their molecular pathways is essential for developing effective breast cancer therapy. BCSCs are responsible for tumor genesis, development, metastasis, treatment resistance, and recurrence. Biomarkers are essential tools for identifying high-risk patients, improving diagnostic accuracy, developing follow-up programs, assessing treatment susceptibility, and predicting prognostic outcomes. Stem cell intervention therapy can provide specialized tools for precision therapy. Biomarker analysis in cancer patients is crucial to identify cells associated with disease progression and post-therapeutic relapse. However, negative post-therapeutic impacts can enhance cancer stemness by boosting BCSCs plasticity phenotypes, activating stemness pathways in non-BCSCs, and promoting senescence escape, leading to tumor relapse and metastasis. Despite the advancements in precision medicine, challenges persist in identifying stem cell markers, limiting the number of eligible patients for treatment. The diversity of biomedical research hinders the development of individualization-based preventative, monitoring, and treatment strategies, especially in oncology. Integrating and interpreting clinical and scientific data remains challenging. The development of stem cell-related indicators could significantly improve disease precision, enabling stem cell-targeted therapy and personalized treatment plans, although BCSCs are promising for breast cancer treatment optimization, serving as biomarkers for current therapy modalities. This summary discusses recent advancements in breast cancer stem cell research, including biomarkers, identification methods, molecular mechanisms, and tools for studying their biological origin and lineage development for precision medicine.

Comprehensive single cell aging atlas of mammary tissues reveals shared epigenomic and transcriptomic signatures of aging and cancer

Aging is the greatest risk factor for breast cancer; however, how age-related cellular and molecular events impact cancer initiation is unknown. We investigate how aging rewires transcriptomic and epigenomic programs of mouse mammary glands at single cell resolution, yielding a comprehensive resource for aging and cancer biology. Aged epithelial cells exhibit epigenetic and transcriptional changes in metabolic, pro-inflammatory, or cancer-associated genes. Aged stromal cells downregulate fibroblast marker genes and upregulate markers of senescence and cancer-associated fibroblasts. Among immune cells, distinct T cell subsets (Gzmk+, memory CD4+, γδ) and M2-like macrophages expand with age. Spatial transcriptomics reveal co-localization of aged immune and epithelial cells in situ. Lastly, transcriptional signatures of aging mammary cells are found in human breast tumors, suggesting mechanistic links between aging and cancer. Together, these data uncover that epithelial, immune, and stromal cells shift in proportions and cell identity, potentially impacting cell plasticity, aged microenvironment, and neoplasia risk.

Signaling pathways governing the maintenance of breast cancer stem cells and their therapeutic implications

Breast cancer stem cells (BCSCs) represent a distinct subpopulation of cells with the ability to self-renewal and differentiate into phenotypically diverse tumor cells. The involvement of CSC in treatment resistance and cancer recurrence has been well established. Numerous studies have provided compelling evidence that the self-renewal ability of cancer stem cells is tightly regulated by specific signaling pathways, which exert critical roles to maintain an undifferentiated phenotype and prevent the differentiation of CSCs. Signaling pathways such as Wnt/β-catenin, NF-κB, Notch, Hedgehog, TGF-β, and Hippo have been implicated in the promotion of self-renewal of many normal and cancer stem cells. Given the pivotal role of BCSCs in driving breast cancer aggressiveness, targeting self-renewal signaling pathways holds promise as a viable therapeutic strategy for combating this disease. In this review, we will discuss the main signaling pathways involved in the maintenance of the self-renewal ability of BCSC, while also highlighting current strategies employed to disrupt the signaling molecules associated with stemness.

Total flavonoids of Litchi seed attenuate stem cell-like properties in breast cancer by regulating Notch3 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Breast cancer has been the most commonly-diagnosed cancer worldwide, and the treatment and prognosis of which are often limited by breast cancer stem cells (BCSCs). Litchi seeds have shown good anti-cancer activity in various cancers including prostate cancer, lung cancer and breast cancer. However, the activity and underlying mechanism of Litchi seeds against BCSCs remain unknown.

AIM OF THE STUDY

To investigate the activity and mechanism of total flavonoids of litchi seed (TFLS) against BCSCs in vitro and in vivo.

MATERIALS AND METHODS

Two orthotopic xenograft mouse models were established using HCC1806 cells pretreated or untreated with TFLS to determine whether TFLS could target BCSCs in vivo. Mammosphere formation and flow cytometry assays were employed to evaluate the effect of TFLS on BCSCs in vitro. The underlying mechanism was investigated using RT-qPCR, Western blot, immunohistochemistry and immunofluorescence experiments.

RESULTS

TFLS could significantly inhibit the viability of HCC1806, MCF-7 and HCC1937 cells in vitro and suppress the growth of HCC1806 cells in vivo. TFLS attenuated stem cell-like properties of breast cancer through reducing the percentage of CD44⁺CD24^-/low cells, inhibiting the mammospheres formation and down-regulating the mRNA and protein levels of cancer stem cells related markers (Oct4, Nanog, Sox2) in MCF-7 and HCC1806 cells. Meanwhile, TFLS suppressed the tumor-initiating ability of BCSCs via reducing the percentage of CD44⁺CD24^-/low cells in tumor and lowering tumor incidence rate in orthotopic xenograft mice. In addition, TFLS treatments restricted the expression and nuclear translocation of Notch3, subsequently down-regulated Hes1 and Runx2 expressions.

CONCLUSIONS

TFLS could suppress the growth of breast cancer and eliminate breast cancer stem cells by inhibiting the Notch3 signaling pathway.

High expression of DLL3 is associated with a poor prognosis and immune infiltration in invasive breast cancer patients

BACKGROUND

Previous studies have shown the prognostic value of delta like canonical Notch ligand 3 (DLL3) in patients with different types of tumors, but the role and predictive value of DLL3 in invasive breast cancer (IBC) have not been reported. In this study, we explored the prognostic ability and potential ways of DLL3 in IBC patients.

METHODS

We retrospectively enrolled 130 IBC patients from a single institution from 2004 to 2019 for bioinformatics and statistical analysis. The Cancer Genome Atlas breast invasive carcinoma (TCGA-BRCA) cohort was used for verification.

RESULTS

High expression of DLL3 was associated with overall survival (OS) in IBC patients (P = 0.023). Multivariate analysis further showed that DLL3 expression was an independent prognostic factor (hazard ratio [HR]: 1.08; 95% confidence interval [CI]: 1.01-1.15; P = 0.017). Time-dependent receiver operating characteristic (ROC) with the area under the curve (0.786) demonstrated that DLL3 expression can predict the survival outcome of IBC patients. Furthermore, the expression of DLL3 was related to a variety of tumor infiltrating immune cells (TIICs), particularly T cells regulatory (Tregs). Gene set enrichment analysis (GSEA) and immunohistochemistry (IHC) results indicated that DLL3 was closely related to p53 signaling pathway.

CONCLUSIONS

High expression of DLL3 was associated with poor prognosis and immune cell infiltration in IBC patients. Moreover, P53 signaling pathway may be the key pathway.

miR-34a mimic or pre-mir-34a, which is the better option for cancer therapy? KatoIII as a model to study miRNA action in human gastric cancer cells

Background

Aberrantly expressed microRNAs play important roles in gastric tumorigenesis. However, use of miRNAs as a therapeutic option in gastric cancer still remains as a challenging problem.

Methods

We performed transient transfection of miR-34a-5p mimic and stable transfection of pre-mir-34a into KatoIII cells. Then, we evaluated the effect of transfected miRNAs on numerous cellular and molecular processes.

Results

Following transient transfection of miR-34a-5p mimic at 25 nM—a commonly used concentration—into KatoIII cells, inhibition of two target genes expression, namely Notch1 and β-catenin, was not observed, but a non-significant marginal increase of these genes was detected. No changes were detected in the percentage of apoptotic cells as well as in CD44 + and EpCAM + cells after 25 nM miR-34a-5p mimic transfection. Interestingly, stable transfection of pre-mir-34a into KatoIII cells (named as KatoIII-pGFPC1-34a cells) caused a significant repression in β-catenin protein and Notch1 mRNA levels (p < 0.05 and p < 0.01, respectively) relative to equivalent control (KatoIII- pGFPC1-empty cells). The percentage of CD44 + cells in the KatoIII-pGFPC1-34a cells (< 40%) was significantly lower than that in control cells (~ 95%) (p < 0.05). An increase of ~ 3.5% in apoptotic cells and a slower proliferation rate were detected in KatoIII-pGFPC1-34a cells.

Conclusions

Our study revealed that the effect of miR mimic in target gene repression can be dependent to its concentration as well as to the cell type. Meanwhile, our findings further support a regulatory function for pre-miRNAs in target repression and will help to develop effective therapeutic strategies in cancer treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-01872-5.

miR-520b Promotes Breast Cancer Stemness Through Hippo/YAP Signaling Pathway

Introduction

The breast cancer stem cells contribute to the initiation, progression, recurrence, metastasis as well as resistance of breast cancer. However, the mechanisms underlying the maintenance of breast cancer stemness have not been fully understood.

Materials and methods

TCGA and GEO data were used for measuring miR-520b expression in breast cancer tissues. Kaplan-meier analysis was used for determining the relationship between miR-520b expression level and the prognosis of patients. Genetic manipulation was performed by lentivirus system and miR-520b inhibitor was used for knockdown of miR-520b. qRT-PCR and Western blot were employed to determine the mRNA and protein levels, respectively. The stemness and EMT (Epithelial to mesenchymal transition) were assessed by sphere-formation and transwell assay as well as the expression of the related markers. The target genes of miR-520b were identified using the online database starBase V3.0.

Results

miR-520b is upregulated in cancer tissues of breast cancer patients and predicts poor prognosis. Upregulation of miR-520b was found in breast cancer stem cells. Ectopic expression of miR-520b promotes the stemness of the breast cancer cells, conversely, depletion of miR-520b attenuates the stemness of these cells. miR-520b positively regulates Hippo/YAP signaling pathway and overexpression of LAST2 abolished the effect of miR-520b on the stemness of breast cancer cells.

Conclusion

miR-520b promotes the stemness of breast cancer patients by activating Hippo/YAP signaling via targeting LATS2.

Human-specific RNA analysis shows uncoupled epithelial-mesenchymal plasticity in circulating and disseminated tumour cells from human breast cancer xenografts

Blood samples, bone marrow, tumours and metastases where possible were collected from SCID mice bearing orthotopic xenografts of the triple-negative MDA-MB-468 cell line or a transplantable ER-positive patient derived xenograft (ED-03), and assessed using human-specific, tandem-nested RT-qPCR for markers relating to detection of circulating (CTCs) and disseminated tumour cells (DTCs), breast cancer clinicopathology, the 'cancer stem cell' phenotype, metabolism, hypoxia and epithelial-mesenchymal plasticity (EMP). Increased levels of SNAI1, ILK, NOTCH1, CK20, and PGR, and a decrease/loss of EPCAM in CTCs/DTCs were observed relative to the primary xenograft across both models. Decreased CD24 and EGFR was restricted to the MDA-MB-468 model, while increased TFF1 was seen in the ED-03 model. The major metabolic regulator PPARGC1A, and several hypoxia-related markers (HIF1A, APLN and BNIP3) were significantly elevated in both models. Increased expression of mesenchymal markers including SNAI1 was seen across both models, however CDH1 did not decrease concordantly, and several other epithelial markers were increased, suggesting an uncoupling of EMP to produce an EMP hybrid or partial-EMT. Single cell analysis of ED-03 CTCs, although limited, indicated uncoupling of the EMP axis in single hybrid cells, rather than distinct pools of epithelial or mesenchymal-enriched cells, however dynamic heterogeneity between CTCs/DTCs cannot be ruled out. Reduced CD24 expression was observed in the MDA-MB-468 CTCs, consistent with the 'breast cancer stem cell' phenotype, and metastatic deposits in this model mostly resembled the primary xenografts, consistent with the mesenchymal-epithelial transition paradigm.

Estrogen receptor α-NOTCH1 axis enhances basal stem-like cells and epithelial-mesenchymal transition phenotypes in prostate cancer

Background

Prostate cancer (PCa) is the second leading cause of mortality and a leading cause of malignant tumors in males. Prostate cancer stem cells (PCSCs) are likely the responsible cell types for cancer initiation, clinical treatment failure, tumor relapse, and metastasis. Estrogen receptor alpha (ERα) is mainly expressed in the basal layer cells of the normal prostate gland and has key roles in coordinating stem cells to control prostate organ development. Here, we investigated the roles of the estrogen-ERα signaling pathway in regulating PCSCs.

Methods

Correlation of CD49f and ERα/NOTCH1 was analyzed in human clinical datasets and tissue samples. Flow cytometry was used to sort CD49f^Hi and CD49f^Low cells. EZH2 recruitment by ERα and facilitation of ERα binding to the NOTCH1 promoter was validated by Co-IP and ChIP. Primary tumor growth, tumor metastasis and sensitivity to 17β-estradiol (E2) inhibitor (tamoxifen) were evaluated in castrated mice.

Results

ERα expression was significantly higher in CD49f^Hi prostate cancer basal stem-like cells (PCBSLCs), which showed basal and EMT features with susceptibility to E2 treatment. ERα-induced estrogen effects were suggested to drive the NOTCH1 signaling pathway activity via binding to the NOTCH1 promoter. Moreover, EZH2 was recruited by ERα and acted as a cofactor to assist ERα-induced estrogen effects in regulating NOTCH1 in PCa. In vivo, E2 promoted tumor formation and metastasis, which were inhibited by tamoxifen.

Conclusions

Our results implicated CD49f+/ERα + prostate cancer cells associated with basal stem-like and EMT features, named EMT-PCBSLCs, in heightened potential for promoting metastasis. NOTCH1 was regulated by E2 in CD49f^Hi EMT-PCBSLCs. These results contribute to insights into the metastatic mechanisms of EMT-PCBSLCs in PCa.

Electronic supplementary material

The online version of this article (10.1186/s12964-019-0367-x) contains supplementary material, which is available to authorized users.

Endocrine Resistance in Hormone Receptor Positive Breast Cancer-From Mechanism to Therapy

The importance and role of the estrogen receptor (ER) pathway has been well-documented in both breast cancer (BC) development and progression. The treatment of choice in women with metastatic breast cancer (MBC) is classically divided into a variety of endocrine therapies, 3 of the most common being: selective estrogen receptor modulators (SERM), aromatase inhibitors (AI) and selective estrogen receptor down-regulators (SERD). In a proportion of patients, resistance develops to endocrine therapy due to a sophisticated and at times redundant interference, at the molecular level between the ER and growth factor. The progression to endocrine resistance is considered to be a gradual, step-wise process. Several mechanisms have been proposed but thus far none of them can be defined as the complete explanation behind the phenomenon of endocrine resistance. Although multiple cellular, molecular and immune mechanisms have been and are being extensively studied, their individual roles are often poorly understood. In this review, we summarize current progress in our understanding of ER biology and the molecular mechanisms that predispose and determine endocrine resistance in breast cancer patients.

Notch and Wnt Dysregulation and Its Relevance for Breast Cancer and Tumor Initiation

Breast cancer is the second leading cause of cancer deaths among women in the world. Treatment has been improved and, in combination with early detection, this has resulted in reduced mortality rates. Further improvement in therapy development is however warranted. This will be particularly important for certain sub-classes of breast cancer, such as triple-negative breast cancer, where currently no specific therapies are available. An important therapy development focus emerges from the notion that dysregulation of two major signaling pathways, Notch and Wnt signaling, are major drivers for breast cancer development. In this review, we discuss recent insights into the Notch and Wnt signaling pathways and into how they act synergistically both in normal development and cancer. We also discuss how dysregulation of the two pathways contributes to breast cancer and strategies to develop novel breast cancer therapies starting from a Notch and Wnt dysregulation perspective.

Inhibition of HER2 Increases JAGGED1-dependent Breast Cancer Stem Cells: Role for Membrane JAGGED1

Purpose: HER2-positive breast cancer is driven by cells possessing stem-like properties of self-renewal and differentiation, referred to as cancer stem cells (CSC). CSCs are implicated in radiotherapy, chemotherapy resistance, and tumor recurrence. NOTCH promotes breast CSC survival and self-renewal, and overexpression of NOTCH1 and the NOTCH ligand JAGGED1 predict poor outcome. Resistance to anti-HER2 therapy in HER2⁺ breast cancer requires NOTCH1, and that combination of trastuzumab and a gamma secretase inhibitor (GSI) prevents tumor relapse in xenograft models.Experimental Design: The current study investigates mechanisms by which HER2 tyrosine kinase activity regulates NOTCH-dependent CSC survival and tumor initiation.Results: Lapatinib-mediated HER2 inhibition shifts the population of HER2⁺ breast cancer cells from low membrane JAGGED1 expression to higher levels, independent of sensitivity to anti-HER2 treatment within the bulk cell population. This increase in membrane JAGGED1 is associated with higher NOTCH receptor expression, activation, and enrichment of CSCs in vitro and in vivo Importantly, lapatinib treatment results in growth arrest and cell death of JAGGED1 low-expressing cells while the JAGGED1 high-expressing cells continue to cycle. High membrane JAGGED1 protein expression predicts poor overall cumulative survival in women with HER2⁺ breast cancer.Conclusions: These results indicate that higher membrane JAGGED1 expression may be used to either predict response to anti-HER2 therapy or for detection of NOTCH-sensitive CSCs posttherapy. Sequential blockade of HER2 followed by JAGGED1 or NOTCH could be more effective than simultaneous blockade to prevent drug resistance and tumor progression. Clin Cancer Res; 24(18); 4566-78. ©2018 AACR.

Molecular and proteomic insight into Notch1 characterization in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) ranks fifth in frequency worldwide amongst all human cancers causing one million deaths annually. Despite many promising treatment options, long-term prognosis remains dismal for the majority of patients who develop recurrence or present with advanced disease. Notch signaling is an evolutionarily conserved pathway crucial for the development and homeostasis of many organs including liver. Herein we showed that aberrant Notch1 is linked to HCC development, tumor recurrence and invasion, which might be mediated, at least in part, through the Notch1-E-Cadherin pathway. Collectively, these findings suggest that targeting Notch1 has important therapeutic value in hepatocellular carcinoma. In this regard, comparative analysis of the secretome of HepG2 and HepG2 Notch1 depleted cells identified novel secreted proteins related to Notch1 expression. Soluble E-Cadherin (sE-Cad) and Thrombospondin-1 (Thbs1) were further validated in human serum as potential biomarkers to predict response to Notch1 inhibitors for a tailored individualized therapy.

Breast cancer stem cells-from origins to targeted therapy

Breast cancer is marked as one of the leading causes of malignancy-related morbidities worldwide. In spite of aggressive interventions, the inevitability of relapse and metastasis severely impede survival rates. Mounting evidence highlight the insidious role of cancer stem cells (CSCs), a small but significant subpopulation of undifferentiated cells that drive tumour progression, spread and resistance to conventional therapy. The nature and significance of breast CSCs remains poorly understood, and even disputed by many researchers. This review discusses the origins, biomarkers, signalling pathways, regulatory mechanisms, and targeted therapy of breast CSCs.

Curcumin: the spicy modulator of breast carcinogenesis

Worldwide breast cancer is the most common cancer in women. For many years clinicians and the researchers are examining and exploring various therapeutic modalities for breast cancer. Yet the disease has remained unconquered and the quest for cure is still going on. Present-day strategy of breast cancer therapy and prevention is either combination of a number of drugs or a drug that modulates multiple targets. In this regard natural products are now becoming significant options. Curcumin exemplifies a promising natural anticancer agent for this purpose. This review primarily underscores the modulatory effect of curcumin on the cancer hallmarks. The focus is its anticancer effect in the complex pathways of breast carcinogenesis. Curcumin modulates breast carcinogenesis through its effect on cell cycle and proliferation, apoptosis, senescence, cancer spread and angiogenesis. Largely the NFkB, PI3K/Akt/mTOR, MAPK and JAK/STAT are the key signaling pathways involved. The review also highlights the curcumin mediated modulation of tumor microenvironment, cancer immunity, breast cancer stem cells and cancer related miRNAs. Using curcumin as a therapeutic and preventive agent in breast cancer is perplexed by its diverse biological activity, much of which remains inexplicable. The information reviewed here should point toward potential scope of future curcumin research in breast cancer.

MicroRNA-34 dysregulation in gastric cancer and gastric cancer stem cell

Gastric cancer is a major cause of cancer mortality worldwide, with a low survival rate for patients with advanced forms of the disease. Over the recent decades, the investigation of the pathophysiological mechanisms of tumourigenesis has opened promising avenues to understand some of the complexities of cancer treatment. However, tumour regeneration and metastasis impose great difficulty for gastric cancer cure. In recent years, cancer stem cells - a small subset of tumour cells in many cancers - have become a major focus of cancer research. Cancer stem cells are capable of self-renewal and are known to be responsible for tumour initiation, metastasis, therapy resistance and cancer recurrence. Recent studies have revealed the key role of microRNAs - small noncoding RNAs regulating gene expression - in these processes. MicroRNAs play crucial roles in the regulation of a wide range of biological processes in a post-transcriptional manner, though their expression is dysregulated in most malignancies, including gastric cancer. In this article, we review the consequences of aberrant expression of microRNA-34 in cancer and cancer stem cells, with a specific focus on the miR-34 dysregulation in gastric cancer and gastric cancer stem cells. We address the critical effects of the aberrant expression of miR-34 and its target genes in maintaining cancer stem cell properties. Information collection and discussion about the advancements in gastric cancer stem cells and microRNAs can be useful for providing novel insights into patient treatment.

Salinomycin inhibits canine mammary carcinoma in vitro by targeting cancer stem cells

Salinomycin (SAL), a polyether ionophore antibiotic, has been demonstrated to selectively kill cancer stem cells (CSCs) in various types of human tumor. The aim of the present study was to investigate the effects of SAL on canine mammary CSCs. CSCs in canine mammary carcinoma cell lines (CMT7364 and CIPp) were identified using a sphere formation assay and flow cytometry. The chemoresistance, invasive potential and expression of stem cell-associated proteins of these spheres was then analyzed. This demonstrated that the spheres exhibited characteristics of CSCs, including a cluster of differentiation (CD)44⁺/CD24^-/low phenotype, upregulation of Wnt/β-catenin signaling pathway-associated proteins and chemoresistance. The viability of the spheres was decreased in a concentration- and time-dependent manner following treatment with SAL, and the spheres did not exhibit increased resistance to SAL compared with their parental cells. In addition, exposure to SAL inhibited sphere-formation and invasive potential in canine mammary CSCs in a dose-dependent manner. Furthermore, SAL decreased the CD44⁺/CD24^-/low population and downregulated the expression of Wnt/β-catenin signaling-associated proteins (β-catenin, Cyclin D1 and octamer-binding transcription factor 4) in the spheres. In conclusion, the present study demonstrated that SAL is an effective inhibitor of canine mammary CSCs in vitro, indicating that SAL is a promising chemotherapeutic agent for the treatment of canine mammary carcinoma.

Non-epigenetic function of HDAC8 in regulating breast cancer stem cells by maintaining Notch1 protein stability

Here, we report a novel non-epigenetic function of histone deacetylase (HDAC) 8 in activating cancer stem cell (CSC)-like properties in breast cancer cells by enhancing the stability of Notch1 protein. The pan-HDAC inhibitors AR-42 and SAHA, and the class I HDAC inhibitor depsipeptide, suppressed mammosphere formation and other CSC markers by reducing Notch1 expression in MDA-MB-231 and SUM-159 cells. Interrogation of individual class I isoforms (HDAC1-3 and 8) using si/shRNA-mediated knockdown, ectopic expression and/or pharmacological inhibition revealed HDAC8 to be the primary mediator of this drug effect. This suppression of Notch1 in response to HDAC8 inhibition was abrogated by the proteasome inhibitor MG132 and siRNA-induced silencing of Fbwx7, indicating Notch1 suppression occurred through proteasomal degradation. However, co-immunoprecipitation analysis indicated that HDAC8 did not form complexes with Notch1 and HDAC inhibition had no effect on Notch1 acetylation. In a xenograft tumor model, the tumorigenicity of breast cancer cells was decreased by HDAC8 knockdown. These findings suggest the therapeutic potential of HDAC8 inhibition to suppress Notch1 signaling in breast cancer.

Original Research: Featured Article: Imatinib mesylate (Gleevec) inhibits Notch and c-Myc signaling: Five-day treatment permanently rescues mammary development

Wap-Int3 transgenic females expressing the Notch4 intracellular domain (designated Int3) from the whey acidic protein promoter exhibit two phenotypes in the mammary gland: blockage of lobuloalveolar development and lactation, and tumor development with 100% penetrance. Previously, we have shown that treatment of Wap-Int3 tumor bearing mice with Imatinib mesylate (Gleevec) is associated with complete regression of the tumor. In the present study, we show that treatment of Wap-Int3 mice during day 1 through day 6 of pregnancy with Gleevec leads to the restoration of their lobuloalveolar development and ability to lactate in subsequent pregnancies in absence of Gleevec treatment. In addition, these mice do not develop mammary tumors. We investigated the mechanism for Gleevec regulation of Notch signaling and found that Gleevec treatment results in a loss of Int3 protein but not of Int3 mRNA in HC11 mouse mammary epithelial cells expressing Int3. The addition of MG-132, a proteasome inhibitor, shows increased ubiquitination of Int3 in the presence of Gleevec. Thus, Gleevec affects the stability of Int3 by promoting the degradation of Int3 via E3 ubiquitin ligases targeting it for the proteasome degradation. Gleevec is a tyrosine kinase inhibitor that acts on c-Kit and PDGFR. Therefore, we investigated the downstream substrate kinase GSK3β to ascertain the possible role that this kinase might play in the stability of Int3. Data show that Gleevec degradation of Int3 is GSK3β dependent. We have expanded our study of the effects Gleevec has on tumorigenesis of other oncogenes. We have found that anchorage-independent growth of HC11-c-Myc cells as well as tumor growth in nude mice is inhibited by Gleevec treatment. As with Int3, Gleevec treatment appears to destabilize the c-Myc protein but not mRNA. These results indicate that Gleevec could be a potential therapeutic drug for patients bearing Notch4 and/or c-Myc positive breast carcinomas.

Simultaneous targeted activation of Notch1 and Vhl-disruption in the kidney proximal epithelial tubular cells in mice

Clear cell renal cell carcinoma (ccRCC) is the most common subtype of kidney cancer, representing approximately 75% of all renal neoplasms. ccRCC is known to be strongly associated with silencing of the von Hippel Lindau (VHL) tumor suppressor gene, yet VHL deficiency alone does not seem to be sufficient to drive the oncogenic transformation of normal renal epithelium and induce renal tumorigenesis. We, and others, have previously suggested that constitutive activation of the Notch signaling pathway, alongside with VHL loss, contribute to the oncogenic features of ccRCC. Here we report a prevailing hyperactivation of the Notch1 receptor in human ccRCC relative to the healthy counterpart. To explore the consequences of the elevated Notch1 signaling observed in ccRCC patient material, we made use of a conditional mouse model based on concurrent ectopic expression of constitutively active Notch1 (NICD1) and deletion of the Vhl gene. Histological examination of the kidneys of the conditional mice demonstrate the existence of nests of dysplastic cells with a clear cytoplasm as a consequence of lipid accumulation, thus displaying a one important hallmark of human ccRCC.

Withaferin A inhibits in vivo growth of breast cancer cells accelerated by Notch2 knockdown

The present study offers novel insights into the molecular circuitry of accelerated in vivo tumor growth by Notch2 knockdown in triple-negative breast cancer (TNBC) cells. Therapeutic vulnerability of Notch2-altered growth to a small molecule (withaferin A, WA) is also demonstrated. MDA-MB-231 and SUM159 cells were used for the xenograft studies. A variety of technologies were deployed to elucidate the mechanisms underlying tumor growth augmentation by Notch2 knockdown and its reversal by WA, including Fluorescence Molecular Tomography for measurement of tumor angiogenesis in live mice, Seahorse Flux analyzer for ex vivo measurement of tumor metabolism, proteomics, and Luminex-based cytokine profiling. Stable knockdown of Notch2 resulted in accelerated in vivo tumor growth in both cells reflected by tumor volume and/or latency. For example, the wet tumor weight from mice bearing Notch2 knockdown MDA-MB-231 cells was about 7.1-fold higher compared with control (P < 0.0001). Accelerated tumor growth by Notch2 knockdown was highly sensitive to inhibition by a promising steroidal lactone (WA) derived from a medicinal plant. Molecular underpinnings for tumor growth intensification by Notch2 knockdown included compensatory increase in Notch1 activation, increased cellular proliferation and/or angiogenesis, and increased plasma or tumor levels of growth stimulatory cytokines. WA administration reversed many of these effects providing explanation for its remarkable anti-cancer efficacy. Notch2 functions as a tumor growth suppressor in TNBC and WA offers a novel therapeutic strategy for restoring this function.

The role of the aryl hydrocarbon receptor in the development of cells with the molecular and functional characteristics of cancer stem-like cells

BACKGROUND

Self-renewing, chemoresistant breast cancer stem cells are believed to contribute significantly to cancer invasion, migration and patient relapse. Therefore, the identification of signaling pathways that regulate the acquisition of stem-like qualities is an important step towards understanding why patients relapse and towards development of novel therapeutics that specifically target cancer stem cell vulnerabilities. Recent studies identified a role for the aryl hydrocarbon receptor (AHR), an environmental carcinogen receptor implicated in cancer initiation, in normal tissue-specific stem cell self-renewal. These studies inspired the hypothesis that the AHR plays a role in the acquisition of cancer stem cell-like qualities.

RESULTS

To test this hypothesis, AHR activity in Hs578T triple negative and SUM149 inflammatory breast cancer cells were modulated with AHR ligands, shRNA or AHR-specific inhibitors, and phenotypic, genomic and functional stem cell-associated characteristics were evaluated. The data demonstrate that (1) ALDH(high) cells express elevated levels of Ahr and Cyp1b1 and Cyp1a1, AHR-driven genes, (2) AHR knockdown reduces ALDH activity by 80%, (3) AHR hyper-activation with several ligands, including environmental ligands, significantly increases ALDH1 activity, expression of stem cell- and invasion/migration-associated genes, and accelerates cell migration, (4) a significant correlation between Ahr or Cyp1b1 expression (as a surrogate marker for AHR activity) and expression of stem cell- and invasion/migration-associated gene sets is seen with genomic data obtained from 79 human breast cancer cell lines and over 1,850 primary human breast cancers, (5) the AHR interacts directly with Sox2, a master regulator of self-renewal; AHR ligands increase this interaction and nuclear SOX2 translocation, (6) AHR knockdown inhibits tumorsphere formation in low adherence conditions, (7) AHR inhibition blocks the rapid migration of ALDH(high) cells and reduces ALDH(high) cell chemoresistance, (8) ALDH(high) cells are highly efficient at initiating tumors in orthotopic xenografts, and (9) AHR knockdown inhibits tumor initiation and reduces tumor Aldh1a1, Sox2, and Cyp1b1 expression in vivo.

CONCLUSIONS

These data suggest that the AHR plays an important role in development of cells with cancer stem cell-like qualities and that environmental AHR ligands may exacerbate breast cancer by enhancing expression of these properties.

Developmental signaling pathways regulating mammary stem cells and contributing to the etiology of triple-negative breast cancer

Cancer has been considered as temporal and spatial aberrations of normal development in tissues. Similarities between mammary embryonic development and cell transformation suggest that the underlying processes required for mammary gland development are also those perturbed during various stages of mammary tumorigenesis and breast cancer (BC) development. The master regulators of embryonic development Cripto-1, Notch/CSL, and Wnt/β-catenin play key roles in modulating mammary gland morphogenesis and cell fate specification in the embryo through fetal mammary stem cells (fMaSC) and in the adult organism particularly within the adult mammary stem cells (aMaSC), which determine mammary progenitor cell lineages that generate the basal/myoepithelial and luminal compartments of the adult mammary gland. Together with recognized transcription factors and embryonic stem cell markers, these embryonic regulatory molecules can be inappropriately augmented during tumorigenesis to support the tumor-initiating cell (TIC)/cancer stem cell (CSC) compartment, and the effects of their deregulation may contribute for the etiology of BC, in particular the most aggressive subtype of BC, triple-negative breast cancer (TNBC). This in depth review will present evidence of the involvement of Cripto-1, Notch/CSL, and Wnt/β-catenin in the normal mammary gland morphogenesis and tumorigenesis, from fMaSC/aMaSC regulation to TIC generation and maintenance in TNBC. Specific therapies for treating TNBC by targeting these embryonic pathways in TICs will be further discussed, providing new opportunities to destroy not only the bulk tumor, but also TICs that initiate and promote the metastatic spread and recurrence of this aggressive subtype of BC.

MiR-139-5p inhibits the biological function of breast cancer cells by targeting Notch1 and mediates chemosensitivity to docetaxel

OBJECTIVES

MiRNA-139 is located at 11q13.4 and it has anti-oncogenic and antimetastatic activity in humans. However, its role in controlling apoptosis, invasion and metastasis and the development of chemosensitivity to docetaxel in breast cancer cells are not fully understood. The aim of this study was to research the biological function of miR-139-5p and the efficacy of chemosensitivity to docetaxel.

METHODS

MiR-139-5p expression in MCF-7, MCF-7/Doc cells and in selected breast cancer tissue samples was confirmed by real-time PCR; cell viability was analyzed by Cell Counting Kit-8 assay; apoptosis and cell cycle were analyzed by flow cytometry; control of metastasis and invasion of breast cancer cells was measured by transwell assay; expression of Notch1 was measured by western blot; a luciferase reporter vector was constructed to identify the miR-139-5p target gene.

RESULTS

MiR-139-5p was significantly down-regulated in breast cancer cells. MiR-139-5p inhibits the viability of breast cancer cells. MiR-139-5p induces apoptosis, causes cell cycle arrest in S phase, inhibits migration and invasion in breast cancer cells, however, MiR-139-5p play the opposite role in docetaxel-induced breast cancer cells.

CONCLUSIONS

MiR-139-5p not only attenuated the development of breast cancer cells but also mediated drug-resistance by regulating the expression of the downstream target gene Notch1.

Targeting of miR34a-NOTCH1 axis reduced breast cancer stemness and chemoresistance

Human breast cancers include cancer stem cell populations as well as nontumorigenic cancer cells. Breast cancer stem cells have self-renewal capability and are resistant to conventional chemotherapy. miRNAs regulate the expression of many target genes; therefore, dysregulation of miRNAs has been associated with the pathogenesis of human diseases, including cancer. However, a role for miRNA dysregulation in stemness and drug resistance has yet to be identified. Members of the miR34 family are reportedly tumor-suppressor miRNAs and are associated with various human cancers. Our results confirm that miR34a expression was downregulated in MCF7/ADR cells compared with MCF7 cells. We hypothesized that this reduction was due to the p53 (TP53) mutation in MCF7/ADR cells. In this study, we found that primary and mature miR34a were suppressed by treatment with p53 RNAi or the dominant-negative p53 mutant in MCF7 cells. Ectopic miR34a expression reduced cancer stem cell properties and increased sensitivity to doxorubicin treatment by directly targeting NOTCH1. Furthermore, tumors from nude mice treated with miR34a were significantly smaller compared with those of mice treated with control lentivirus. Our research suggests that the ectopic expression of miR34a represents a novel therapeutic approach in chemoresistant breast cancer treatment.

Oncogenic suppression of apoptosis uncovers a Rac1/JNK proliferation pathway activated by loss of Par3

Disruption of epithelial organization and loss of growth control are universal features of carcinomas, yet how these features are linked during cancer progression remains poorly understood. Cell polarity proteins control cellular and tissue organization and are emerging as important mediators of cancer progression. The Par3 polarity protein is a molecular scaffold that functions to recruit and spatially organize signaling factors, and was recently identified as a suppressor of breast cancer invasion and metastasis. Here, we show that loss of Par3 in mammary epithelial cells promotes apoptosis, and that oncogenic Notch overcomes the apoptotic signal to reveal an unexpected pro-proliferative role for loss of Par3 in mammary tumors. In this context, loss of Par3 deregulates Rac1 activity to activate Jun N-terminal Kinase-dependent proliferation and tumor growth. Thus, we demonstrate a mechanism by which loss of Par3 promotes proliferation and tumorigenesis, which supports a tumor-suppressive function for Par3 in the mammary epithelium.

Bringing androgens up a NOTCH in breast cancer

While it has been known for decades that androgen hormones influence normal breast development and breast carcinogenesis, the underlying mechanisms have only been recently elucidated. To date, most studies have focused on androgen action in breast cancer cell lines, yet these studies represent artificial systems that often do not faithfully replicate/recapitulate the cellular, molecular and hormonal environments of breast tumours in vivo. It is critical to have a better understanding of how androgens act in the normal mammary gland as well as in in vivo systems that maintain a relevant tumour microenvironment to gain insights into the role of androgens in the modulation of breast cancer development. This in turn will facilitate application of androgen-modulation therapy in breast cancer. This is particularly relevant as current clinical trials focus on inhibiting androgen action as breast cancer therapy but, depending on the steroid receptor profile of the tumour, certain individuals may be better served by selectively stimulating androgen action. Androgen receptor (AR) protein is primarily expressed by the hormone-sensing compartment of normal breast epithelium, commonly referred to as oestrogen receptor alpha (ERa (ESR1))-positive breast epithelial cells, which also express progesterone receptors (PRs) and prolactin receptors and exert powerful developmental influences on adjacent breast epithelial cells. Recent lineage-tracing studies, particularly those focussed on NOTCH signalling, and genetic analysis of cancer risk in the normal breast highlight how signalling via the hormone-sensing compartment can influence normal breast development and breast cancer susceptibility. This provides an impetus to focus on the relationship between androgens, AR and NOTCH signalling and the crosstalk between ERa and PR signalling in the hormone-sensing component of breast epithelium in order to unravel the mechanisms behind the ability of androgens to modulate breast cancer initiation and growth.

Runx2 is a novel regulator of mammary epithelial cell fate in development and breast cancer

Regulators of differentiated cell fate can offer targets for managing cancer development and progression. Here, we identify Runx2 as a new regulator of epithelial cell fate in mammary gland development and breast cancer. Runx2 is expressed in the epithelium of pregnant mice in a strict temporally and hormonally regulated manner. During pregnancy, Runx2 genetic deletion impaired alveolar differentiation in a manner that disrupted alveolar progenitor cell populations. Conversely, exogenous transgenic expression of Runx2 in mammary epithelial cells blocked milk production, suggesting that the decrease in endogenous Runx2 observed late in pregnancy is necessary for full differentiation. In addition, overexpression of Runx2 drove epithelial-to-mesenchymal transition-like changes in normal mammary epithelial cells, whereas Runx2 deletion in basal breast cancer cells inhibited cellular phenotypes associated with tumorigenesis. Notably, loss of Runx2 expression increased tumor latency and enhanced overall survival in a mouse model of breast cancer, with Runx2-deficient tumors exhibiting reduced cell proliferation. Together, our results establish a previously unreported function for Runx2 in breast cancer that may offer a novel generalized route for therapeutic interventions. Cancer Res; 74(18); 5277-86. ©2014 AACR.

Effects of Notch-1 down-regulation on malignant behaviors of breast cancer stem cells

This study examined the effect of Notch-1 signaling on malignant behaviors of breast cancer cells by regulating breast cancer stem cells (BCSCs). BCSCs were enriched by using serum-free medium and knocked out of Notch-1 by using a lentiviral vector. Real-time polymerase chain reaction (RT-PCR) and Western blotting were used to detect the Notch-1 expression levels in breast cancer cell lines and BCSCs, and flow cytometry to detect the proportion of BCSCs in BCSC spheres. The BCSC self-renewal, migration, invasion, and tumorigenicity were examined by the tumor microsphere-forming assay and transwell assay and after xenotransplantation. The results showed that the Notch-1 silencing reduced the number of BCSC spheres, the proportion of BCSCs, and the number of cells penetrating through the transwell membrane. It also decreased the size of tumors that were implanted in the nude mice. These results suggest that Notch-1 signaling is intimately linked to the behaviors of BCSCs. Blocking Notch-1 signaling can inhibit the malignant behaviors of BCSCs, which may provide a promising therapeutical approach for breast cancer.

Modulation of apoptosis-related cell signalling pathways by curcumin as a strategy to inhibit tumor progression

A hallmark of cancer is resistance to apoptosis, with both the loss of proapoptotic signals and the gain of anti-apoptotic mechanisms contributing to tumorigenesis. As inducing apoptosis in malignant cells is one of the most challenging tasks regarding cancer, researchers increasingly focus on natural products to regulate apoptotic signaling pathways. Curcumin, a polyphenolic derivative of turmeric, is a natural compound derived from Curcuma longa, has attracted great interest in the research of cancer during the last half century. Extensive studies revealed that curcumin has chemopreventive properties, which are mainly due to its ability to arrest cell cycle and to induce apoptosis in cancer cells either alone or in combination with chemotherapeutic agents or radiation. The underlying action mechanisms of curcumin are diverse and has not been elucidated so far. By regulating multiple important cellular signalling pathways including NF-κB, TRAIL, PI3 K/Akt, JAK/STAT, Notch-1, JNK, etc., curcumin are known to activate cell death signals and induce apoptosis in pre-cancerous or cancer cells without affecting normal cells, thereby inhibiting tumor progression. Several phase I and phase II clinical trials indicate that curcumin is quite safe and may exhibit therapeutic efficacy. This article reviews the main effects of curcumin on the different apoptotic signaling pathways involved in curcumin induced apoptosis in cancer cells via cellular transduction pathways and provides an in depth assessment of its pharmacological activity in the management of tumor progression.

Prognostic value of gene signatures and proliferation in lymph-node-negative breast cancer

Introduction

The overall survival rate is good for lymph-node-negative breast cancer patients, but they still suffer from serious over- and some undertreatments. Prognostic and predictive gene signatures for node-negative breast cancer have a high number of genes related to proliferation. The prognostic value of gene sets from commercial gene-expression assays were compared with proliferation markers.

Methods

Illumina WG6 mRNA microarray analysis was used to examine 94 fresh-frozen tumour samples from node-negative breast cancer patients. The patients were divided into low- and high-risk groups for distant metastasis based on the MammaPrint-related genes, and into low-, intermediate- and high-risk groups based on the recurrence score algorithm with genes included in Oncotype DX. These data were then compared to proliferation status, as measured by the mitotic activity index, the expressions of phosphohistone H3 (PPH3), and Ki67.

Results

Kaplan-Meier survival analysis for distant-metastasis-free survival revealed that patients with weak and strong PPH3 expressions had 14-year survival rates of 87% (n = 45), and 65% (n = 49, p = 0.014), respectively. Analysis of the MammaPrint classification resulted in 14-year survival rates of 80% (n = 45) and 71% (n = 49, p = 0.287) for patients with low and high risks of recurrence, respectively. The Oncotype DX categorization yielded 14-year survival rates of 83% (n = 18), 79% (n = 42) and 68% (n = 34) for those in the low-, intermediate- and high-risk groups, respectively (p = 0.52). Supervised hierarchical cluster analysis for distant-metastasis-free survival in the subgroup of patients with strong PPH3 expression revealed that the genes involved in Notch signalling and cell adhesion were expressed at higher levels in those patients with distant metastasis.

Conclusion

This pilot study indicates that proliferation has greater prognostic value than the expressions of either MammaPrint- or Oncotype-DX-related genes. Furthermore, in the subgroup of patients with high proliferation, Notch signalling pathway genes appear to be expressed at higher levels in patients who develop distant metastasis.

How pregnancy at early age protects against breast cancer

Pregnancy at an early age has a strong protective effect against breast cancer in humans and rodents. Postulated mechanisms underlying this phenomenon include alterations in the relative dynamics of hormone and growth factor-initiated cell fate-determining signaling pathways within the hierarchically organized mammary gland epithelium. Recent studies in epithelial cell subpopulations isolated from mouse and human mammary glands have shown that early pregnancy decreases the proportion of hormone receptor-positive cells and causes pronounced changes in gene expression as well as decreased proliferation in stem/progenitor cells. The changes include downregulation of Wnt and transforming growth factor β (TGFβ) signaling. These new findings highlight the importance of cell-cell interactions within the mammary gland epithelium in modulating cancer risk and provide potential targets for breast cancer prevention strategies.

Differential expression of Notch1 intracellular domain and p21 proteins, and their clinical significance in gastric cancer

Changes in the expression of the Notch1 intracellular domain (NICD) and p21 proteins have been shown to be closely associated with the development and progression of a number of cancers. The present study aimed to investigate the expression levels of the two proteins in gastric carcinoma and precancerous lesions, and to determine the clinical significance of this. A total of 109 gastric cancer, 57 precancerous gastric lesion, 50 chronic superficial gastritis and 17 normal gastric mucosa patients were recruited for immunohistochemical staining of NICD and p21 protein expression. The protein expression levels in the gastric cancer patient samples were associated with the clinicopathological and survival data. NICD protein levels were upregulated gradually from normal gastric mucosae through chronic superficial gastritis and precancerous gastric lesions to gastric cancer tissues (P<0.01), whereas p21 protein levels were downregulated accordingly (P<0.01). Increased NICD and a loss of p21 expression were closely associated with tumor dedifferentiation, depth of tumor invasion, lymph node metastasis, surface morphology and Lauren classification in gastric cancer. Thus, NICD expression was inversely associated with p21 expression. In addition, the overall survival rate was greater in NICD⁻ and P21⁺ patients than in NICD⁺ and P21⁻ patients, respectively (P<0.05). The COX regression multivariate analysis revealed that NICD⁺, p21⁻, depth of tumor invasion and lymph node metastasis were all independent prognostic factors for patients with gastric cancer. NICD and p21 proteins are differentially expressed in gastric cancer and the aberrant expression of these proteins is associated with an advanced tumor stage, tumor metastasis and overall patient survival. Future studies are required to further evaluate the two proteins as novel prognostic markers for patients with gastric cancer.

LGR5 positivity defines stem-like cells in colorectal cancer

Like normal colorectal epithelium, colorectal carcinomas (CRCs) are organized hierarchically and include populations of cells with stem-like properties. Leucine-rich-repeat-containing G-protein-coupled receptor 5 (LGR5) is associated with these stem cells in normal colorectal epithelium; however, the precise function of LGR5 in CRC remains largely unknown. Here, we analyzed the functional and molecular consequences of short hairpin RNA-mediated silencing of LGR5 in CRC cell lines SW480 and HT-29. Additionally, we exposed Lgr5-EGFP-IRES-CreERT2 mice to azoxymethane/dextrane sodium sulfate (AOM/DSS), which induces inflammation-driven colon tumors. Tumors were then flow-sorted into fractions of epithelial cells that expressed high or low levels of Lgr5 and were molecularly characterized using gene expression profiling and array comparative genomic hybridization. Silencing of LGR5 in SW480 CRC cells resulted in a depletion of spheres but did not affect adherently growing cells. Spheres expressed higher levels of several stem cell-associated genes than adherent cells, including LGR5. Silencing of LGR5 reduced proliferation, migration and colony formation in vitro and tumorigenicity in vivo. In accordance with these results, NOTCH signaling was downregulated upon LGR5 silencing. In AOM/DSS-induced colon tumors, Lgr5 high cells showed higher levels of several stem cell-associated genes and higher Wnt signaling than Lgr5 low tumor cells and Lgr5 high normal colon cells. Array comparative genomic hybridization revealed no genomic imbalances in either tumor cell fraction. Our data elucidate mechanisms that define the role of LGR5 as a marker for stem-like cells in CRC.

Breast cancer stem cells

Cancer metastasis, resistance to therapies and disease recurrence are significant hurdles to successful treatment of breast cancer. Identifying mechanisms by which cancer spreads, survives treatment regimes and regenerates more aggressive tumors are critical to improving patient survival. Substantial evidence gathered over the last 10 years suggests that breast cancer progression and recurrence is supported by cancer stem cells (CSCs). Understanding how CSCs form and how they contribute to the pathology of breast cancer will greatly aid the pursuit of novel therapies targeted at eliminating these cells. This review will summarize what is currently known about the origins of breast CSCs, their role in disease progression and ways in which they may be targeted therapeutically.

Mutant p53-Notch1 Signaling Axis Is Involved in Curcumin-Induced Apoptosis of Breast Cancer Cells

Notch1 has been reported to be highly expressed in triple-negative and other subtypes of breast cancer. Mutant p53 (R280K) is overexpressed in MDA-MB-231 triple-negative human breast cancer cells. The present study aimed to determine whether the mutant p53 can be a potent transcriptional activator of the Notch1 in MDA-MB-231 cells, and explore the role of this mutant p53-Notch1 axis in curcumin-induced apoptosis. We found that curcumin treatment resulted in an induction of apoptosis in MDA-MB-231 cells, together with downregulation of Notch1 and its downstream target, Hes1. This reduction in Notch1 expression was determined to be due to the decreased activity of endogenous mutant p53. We confirmed the suppressive effect of curcumin on Notch1 transcription by performing a Notch1 promoter-driven reporter assay and identified a putative p53-binding site in the Notch1 promoter by EMSA and chromatin immunoprecipitation analysis. Overexpression of mutant p53 increased Notch1 promoter activity, whereas knockdown of mutant p53 by small interfering RNA suppressed Notch1 expression, leading to the induction of cellular apoptosis. Moreover, curcumin-induced apoptosis was further enhanced by the knockdown of Notch1 or mutant p53, but it was decreased by the overexpression of active Notch1. Taken together, our results demonstrate, for the first time, that Notch1 is a transcriptional target of mutant p53 in breast cancer cells and suggest that the targeting of mutant p53 and/or Notch1 may be combined with a chemotherapeutic strategy to improve the response of breast cancer cells to curcumin.

Gauging NOTCH1 Activation in Cancer Using Immunohistochemistry

Fixed, paraffin-embedded (FPE) tissues are a potentially rich resource for studying the role of NOTCH1 in cancer and other pathologies, but tests that reliably detect activated NOTCH1 (NICD1) in FPE samples have been lacking. Here, we bridge this gap by developing an immunohistochemical (IHC) stain that detects a neoepitope created by the proteolytic cleavage event that activates NOTCH1. Following validation using xenografted cancers and normal tissues with known patterns of NOTCH1 activation, we applied this test to tumors linked to dysregulated Notch signaling by mutational studies. As expected, frequent NICD1 staining was observed in T lymphoblastic leukemia/lymphoma, a tumor in which activating NOTCH1 mutations are common. However, when IHC was used to gauge NOTCH1 activation in other human cancers, several unexpected findings emerged. Among B cell tumors, NICD1 staining was much more frequent in chronic lymphocytic leukemia than would be predicted based on the frequency of NOTCH1 mutations, while mantle cell lymphoma and diffuse large B cell lymphoma showed no evidence of NOTCH1 activation. NICD1 was also detected in 38% of peripheral T cell lymphomas. Of interest, NICD1 staining in chronic lymphocytic leukemia cells and in angioimmunoblastic lymphoma was consistently more pronounced in lymph nodes than in surrounding soft tissues, implicating factors in the nodal microenvironment in NOTCH1 activation in these diseases. Among carcinomas, diffuse strong NICD1 staining was observed in 3.8% of cases of triple negative breast cancer (3 of 78 tumors), but was absent from 151 non-small cell lung carcinomas and 147 ovarian carcinomas. Frequent staining of normal endothelium was also observed; in line with this observation, strong NICD1 staining was also seen in 77% of angiosarcomas. These findings complement insights from genomic sequencing studies and suggest that IHC staining is a valuable experimental tool that may be useful in selection of patients for clinical trials.

The Notch signaling pathway as a mediator of tumor survival

The Notch signaling pathway is evolutionarily conserved and responsible for cell fate determination in the developing embryo and mature tissue. At the molecular level, ligand binding activates Notch signaling by liberating the Notch intracellular domain, which then translocates into the nucleus and activates gene transcription. Despite the elegant simplicity of this pathway, which lacks secondary messengers or a signaling cascade, Notch regulates gene expression in a highly context- and cell-type-dependent manner. Notch signaling is frequently dysregulated, most commonly by overactivation, across many cancers and confers a survival advantage on tumors, leading to poorer outcomes for patients. Recent studies demonstrate how Notch signaling increases tumor cell proliferation and provide evidence that active Notch signaling maintains the cancer stem-cell pool, induces epithelial-mesenchymal transition and promotes chemoresistance. These studies imply that pharmacological inhibition of Notch signaling may refine control of cancer therapy and improve patient survival. Gamma secretase inhibitors (GSIs) are drugs that inhibit Notch signaling and may be successful in controlling cancer cell growth in conjunction with standard chemotherapy, but substantial side effects have hampered their widespread use. Recent efforts have been aimed at the development of antibodies against specific Notch receptors and ligands with the hope of limiting side effects while providing the same therapeutic benefit as GSIs. Together, studies characterizing Notch signaling and modulation have offered hope that refined methods targeting Notch may become powerful tools in anticancer therapeutics.

Pathways to breast cancer recurrence

Breast cancer remains a deadly disease, even with all the recent technological advancements. Early intervention has made an impact, but an overwhelmingly large number of breast cancer patients still live under the fear of “recurrent” disease. Breast cancer recurrence is clinically a huge problem and one that is largely not well understood. Over the years, a number of factors have been studied with an overarching aim of being able to prognose recurrent disease. This paper attempts to provide an overview of our current knowledge of breast cancer recurrence and its associated challenges. Through a survey of the literature on cancer stem cells (CSCs), epithelial-mesenchymal transition (EMT), various signaling pathways such as Notch/Wnt/hedgehog, and microRNAs (miRNAs), we also examine the hypotheses that are currently under investigation for the prevention of breast cancer recurrence.

Differential gene expression in nuclear label-retaining cells in the developing mouse mammary gland

The immortal strand theory postulates stem cells protect themselves from DNA replication-associated mutations and subsequent cancer risk through selective segregation of template DNA strands. Stem cells self-renew by asymmetric cellular division. During asymmetric division, stem cells maintain their template DNA strands, while the newly synthesized DNA strands segregate to newly formed daughter cells. Previous studies have demonstrated that self-renewing mammary stem cells originate in the expanding mammary ducts during puberty-associated allometric growth. In this study, we labeled newly forming mammary stem cells with the thymidine analog 5-ethynl-2'-deoxyuridine for 2 weeks during allometric ductal expansion. Cells that incorporate and retain the nuclear label following extended chase periods are termed label-retaining cells (LRCs). A second nuclear label, 5-bromodeoxyuridine, was administered before euthanasia to identify cells traversing the cell cycle. Mammary cells collected following euthanasia were sorted based on nuclear label retention. Members of the Notch and Wnt signaling pathways were found differentially expressed by mammary LRCs. These pathways are involved in the regulation of stem cells in the mouse mammary gland. Upon further analysis, we found that in contrast to non-LRCs, Notch1 and Notch2 are expressed and localized in the nuclei of the LRCs. Expression of Notch-inducible genes, Hes1 and Hey2, was elevated in LRCs. Inhibition of Notch1 by shRNA reduced colony forming potential and label retention by mammary epithelial cells in vitro. These results indicate that genes are differentially regulated in the LRC population of mammary glands and Notch1 mediates asymmetric cell division of mammary progenitor cells.

[Modification of a micromethod for determining leukocyte migration inhibition and its significance in oncological patients]

Breast cancer stem cells (BCSC) have been implicated in tumor initiation, progression, metastasis, recurrence, and resistance to therapy. The origins of BCSCs remain controversial due to tumor heterogeneity and the presence of such small side populations for study, but nonetheless, cell surface markers and their correlation with BCSC functionality continue to be identified. BCSCs are driven by persistent activation of developmental pathways, such as Notch, Wnt, Hippo, and Hedgehog and new treatment strategies that are aimed at these pathways are in preclinical and clinical development.