Notch Signaling Activation as a Hallmark for Triple-Negative Breast Cancer Subtype

Expression of NOTCH1, NOTCH4, HLA-DMA and HLA-DRA is synergistically associated with T cell exclusion, immune checkpoint blockade efficacy and recurrence risk in ER-negative breast cancer

PURPOSE

Reliable biomarkers to predict the outcome and treatment response of estrogen receptor (ER)-negative breast cancer (BC) are urgently needed. Since immune-related signaling plays an important role in the tumorigenesis of ER-negative BC, we asked whether Notch genes, alone or in combination with other immune genes, can be used to predict the clinical outcome and immune checkpoint blockade (ICB) for this type of cancer.

METHODS

We analyzed transcriptome data of 6918 BC samples from five independent cohorts, 81 xenograft triple-negative BC tumors that respond differently to ICB treatment and 754 samples of different cancer types from patients treated with ICB agents.

RESULTS

We found that among four Notch genes, the expression levels of NOTCH1 and NOTCH4 were positively associated with recurrence of ER-negative BC, and that combined expression of these two genes (named Notch14) further enhanced this association, which was comparable with that of the Notch pathway signature. Analysis of 1182 immune-related genes revealed that the expression levels of most HLA genes, particularly HLA-DMA and -DRA, were reversely associated with recurrence in ER-negative BC with low, but not high Notch14 expression. A combined expression signature of NOTCH1, NOTCH4, HLA-DMA and HLA-DRA was more prognostic for ER-negative and triple-negative BCs than previously reported immune-related signatures. Furthermore, we found that the expression levels of these four genes were also synergistically associated with T cell exclusion score, infiltration of specific T cells and ICB efficacy in ER-negative BC, thereby providing a potential molecular mechanism for the synergistic effect of these genes on BC.

CONCLUSIONS

Our data indicate that a gene signature composed of NOTCH1, NOTCH4, HLA-DMA and HLA-DRA may serve as a potential promising biomarker for predicting ICB therapy efficacy and recurrence in ER-negative/triple-negative BCs.

Identification of Potential RBPJ-Specific Inhibitors for Blocking Notch Signaling in Breast Cancer Using a Drug Repurposing Strategy

Notch signaling is a key parameter in regulating cell fate during tissue homeostasis, and an aberrant Notch pathway can result in mammary gland carcinoma and has been associated with poor breast cancer diagnosis. Although inhibiting Notch signaling would be advantageous in the treatment of breast cancer, the currently available Notch inhibitors have a variety of side effects and their clinical trials have been discontinued. Thus, in search of a more effective and safer Notch inhibitor, inhibiting recombinant signal binding protein for immunoglobin kappaJ region (RBPJ) specifically makes sense, as RBPJ forms a transcriptional complex that activates Notch signaling. From our established database of more than 10,527 compounds, a drug repurposing strategy-combined docking study and molecular dynamic simulation were used to identify novel RBPJ-specific inhibitors. The compounds with the best performance were examined using an in vitro cellular assay and an in vivo anticancer investigation. Finally, an FDA-approved antibiotic, fidaxomicin, was identified as a potential RBPJ inhibitor, and its ability to block RBPJ-dependent transcription and thereby inhibit breast cancer growth was experimentally verified. Our study demonstrated that fidaxomicin suppressed Notch signaling and may be repurposed for the treatment of breast cancer.

Emergence of Nanotechnology as a Powerful Cavalry against Triple-Negative Breast Cancer (TNBC)

Triple-negative breast cancer (TNBC) is considered one of the un-manageable types of breast cancer, involving devoid of estrogen, progesterone, and human epidermal growth factor receptor 2 (HER 2) receptors. Due to their ability of recurrence and metastasis, the management of TNBC remains a mainstay challenge, despite the advancements in cancer therapies. Conventional chemotherapy remains the only treatment regimen against TNBC and suffers several limitations such as low bioavailability, systemic toxicity, less targetability, and multi-drug resistance. Although various targeted therapies have been introduced to manage the hardship of TNBC, they still experience certain limitations associated with the survival benefits. The current research thus aimed at developing and improving the strategies for effective therapy against TNBC. Such strategies involved the emergence of nanoparticles. Nanoparticles are designated as nanocavalries, loaded with various agents (drugs, genes, etc.) to battle the progression and metastasis of TNBC along with overcoming the limitations experienced by conventional chemotherapy and targeted therapy. This article documents the treatment regimens of TNBC along with their efficacy towards different subtypes of TNBC, and the various nanotechnologies employed to increase the therapeutic outcome of FDA-approved drug regimens.

Characterization of Pyroptosis-Related Subtypes via RNA-Seq and ScRNA-Seq to Predict Chemo-Immunotherapy Response in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is associated with poor prognosis and invalid therapeutical response to immunotherapy due to biological heterogeneity. There is an urgent need to screen for reliable indices, especially immunotherapy-associated biomarkers that can predict patient outcomes. Pyroptosis, as an inflammation-induced type of programmed cell death, is shown to create a tumor-suppressive environment and improve the chemotherapeutic response in multiple tumors. However, the specific therapeutic effect of pyroptosis in TNBC remains unclear. In this study, we present a consensus clustering by pyroptosis-related signatures of 119 patients with TNBC into two subtypes (clusterA and clusterB) with distinct immunological and prognostic characteristics. First, clusterB, associated with better outcomes, was characterized by a significantly higher pyroptosis-related signature expression, tumor microenvironment prognostic score, and upregulation of immunotherapy checkpoints. A total of 262 differentially expressed genes between the subtypes were further identified and the Ps-score was built using LASSO and COX regression analyses. The external GEO data set demonstrated that cohorts with low Ps-scores consistently had higher expression of pyroptosis-related signatures, immunocyte infiltration levels, and better prognosis. In addition, external immunotherapy and chemotherapy cohorts validated that patients with lower Ps-scores exhibited significant therapeutic response and clinical benefit. Combined with other clinical characteristics, we successfully constructed a nomogram to effectively predict the survival rate of patients with TNBC. Finally, using the scRNA-seq data sets, we validated the landscape of cellular subtypes of TNBC and successfully constructed an miRNA-Ps-score gene interaction network. These findings indicated that the systematic assessment of tumor pyroptosis and identification of Ps-scores has potential clinical implications and facilitates tailoring optimal immunotherapeutic strategies for TNBC.

Therapeutic progress and challenges for triple negative breast cancer: targeted therapy and immunotherapy

Triple negative breast cancer (TNBC) is a subtype of breast cancer, with estrogen receptor, human epidermal growth factor receptor 2 and progesterone receptor negative. TNBC is characterized by high heterogeneity, high rates of metastasis, poor prognosis, and lack of therapeutic targets. Now the treatment of TNBC is still based on surgery and chemotherapy, which is effective only in initial stage but almost useless in advanced stage. And due to the lack of hormone target, hormonal therapies have little beneficial effects. In recent years, signaling pathways and receptor-specific targets have been reported to be effective in TNBC patients under specific clinical conditions. Now targeted therapies have been approved for many other cancers and even other subtypes of breast cancer, but treatment options for TNBC are still limited. Most of TNBC patients showed no response, which may be related to the heterogeneity of TNBC, therefore more effective treatments and predictive biomarkers are needed. In the present review, we summarize potential treatment opinions for TNBC based on the dysregulated receptors and signaling pathways, which play a significant role in multiple stages of TNBC development. We also focus on the application of immunotherapy in TNBC, and summarize the preclinical and clinical trials of therapy for patients with TNBC. We hope to accelerate the research and development of new drugs for TNBC by understanding the relevant mechanisms, and to improve survival.

NOTCH1 PEST domain variants are responsive to standard of care treatments despite distinct transformative properties in a breast cancer model

Activating variants in the PEST region of NOTCH1 have been associated with aggressive phenotypes in human cancers, including triple-negative breast cancer (TNBC). Previous studies suggested that PEST domain variants in TNBC patients resulted in increased cell proliferation, invasiveness, and decreased overall survival. In this study, we assess the phenotypic transformation of activating NOTCH1 variants and their response to standard of care therapies. AAV-mediated gene targeting was used to isogenically incorporate 3 NOTCH1 variants, including a novel TNBC frameshift variant, in two non-tumorigenic breast epithelial cell lines, MCF10A and hTERT-IMEC. Two different variants at the NOTCH1 A2241 site (A2441fs and A2441T) both demonstrated increased transformative properties when compared to a non-transformative PEST domain variant (S2523L). These phenotypic changes include proliferation, migration, anchorage-independent growth, and MAPK pathway activation. In contrast to previous studies, activating NOTCH1 variants did not display sensitivity to a gamma secretase inhibitor (GSI) or resistance to chemotherapies. This study demonstrates distinct transformative phenotypes are specific to a given variant within NOTCH1 and these phenotypes do not correlate with sensitivities or resistance to chemotherapies or GSIs. Although previous studies have suggested NOTCH1 variants may be prognostic for TNBC, our study does not demonstrate prognostic ability of these variants and suggests further characterization would be required for clinical applications.

Epithelial-to-Mesenchymal Transition Signaling Pathways Responsible for Breast Cancer Metastasis

Breast carcinoma is highly metastatic and invasive. Tumor metastasis is a convoluted and multistep process involving tumor cell disseminating from their primary site and migrating to the secondary organ. Epithelial-mesenchymal transition (EMT) is one of the crucial steps that initiate cell progression, invasion, and metastasis. During EMT, epithelial cells alter their molecular features and acquire a mesenchymal phenotype. The regulation of EMT is centered by several signaling pathways, including primary mediators TGF-β, Notch, Wnt, TNF-α, Hedgehog, and RTKs. It is also affected by hypoxia and microRNAs (miRNAs). All these pathways are the convergence on the transcriptional factors such as Snail, Slug, Twist, and ZEB1/2. In addition, a line of evidence suggested that EMT and cancer stem like cells (CSCs) are associated. EMT associated cancer stem cells display mesenchymal phenotypes and resist to chemotherapy or targeted therapy. In this review, we highlighted recent discoveries in these signaling pathways and their regulation in breast cancer metastasis and invasion. While the clinical relevance of EMT and breast cancers remains controversial, we speculated a convergent signaling network pivotal to elucidating the transition of epithelial to mesenchymal phenotypes and onset of metastasis of breast cancer cells.

Different Expression Levels of DLK2 Inhibit NOTCH Signaling and Inversely Modulate MDA-MB-231 Breast Cancer Tumor Growth In Vivo

NOTCH signaling is implicated in the development of breast cancer tumors. DLK2, a non-canonical inhibitor of NOTCH signaling, was previously shown to be involved in skin and breast cancer. In this work, we studied whether different levels of DLK2 expression influenced the breast cancer characteristics of MDA-MB-231 cells. We found that DLK2 overexpression inhibited NOTCH activation in a dose-dependent manner. Moreover, depending on the level of inhibition of NOTCH1 activation generated by different levels of DLK2 expression, cell proliferation, cell cycle dynamics, cell apoptosis, cell migration, and tumor growth in vivo were affected in opposite directions. Low levels of DLK2 expression produced a slight inhibition of NOTCH1 activation, and enhanced MDA-MB-231 cell invasion in vitro and cell proliferation both in vitro and in vivo. In contrast, MDA-MB-231 cells expressing elevated levels of DLK2 showed a strong inhibition of NOTCH1 activation, decreased cell proliferation, increased cell apoptosis, and were unable to generate tumors in vivo. In addition, DLK2 expression levels also affected some members of other cell signaling pathways implicated in cancer, such as ERK1/2 MAPK, AKT, and rpS6 kinases. Our data support an important role of DLK2 as a protein that can finely regulate NOTCH signaling and affect the tumor properties and growth dynamics of MDA-MB-231 breast cancer cells.

Triptonide effectively inhibits triple-negative breast cancer metastasis through concurrent degradation of Twist1 and Notch1 oncoproteins

Background

Triple-negative breast cancer (TNBC) is highly metastatic and lethal. Due to a lack of druggable targets for this disease, there are no effective therapies in the clinic.

Methods

We used TNBC cells and xenografted mice as models to explore triptonide-mediated inhibition of TNBC metastasis and tumor growth. Colony formation assay was used to quantify the tumorigenesis of TNBC cells. Wound-healing and cell trans-well assays were utilized to measure cell migration and invasion. Tube formation assay was applied to access tumor cell-mediated vasculogenic mimicry. Western blot, quantitative-PCR, immunofluorescence imaging, and immunohistochemical staining were used to measure the expression levels of various tumorigenic genes in TNBC cells.

Results

Here, we showed that triptonide, a small molecule from the traditional Chinese medicinal herb Tripterygium wilfordii Hook F, potently inhibited TNBC cell migration, invasion, and vasculogenic mimicry, and effectively suppressed TNBC tumor growth and lung metastasis in xenografted mice with no observable toxicity. Molecular mechanistic studies revealed that triptonide strongly triggered the degradation of master epithelial-mesenchymal transition (EMT)-inducing protein Twist1 through the lysosomal system and reduced Notch1 expression and NF-κB phosphorylation, which consequently diminished the expression of pro-metastatic and angiogenic genes N-cadherin, VE-cadherin, and vascular endothelial cell growth factor receptor 2 (VEGFR2).

Conclusions

Triptonide effectively suppressed TNBC cell tumorigenesis, vasculogenic mimicry, and strongly inhibited the metastasis of TNBC via degradation of Twist1 and Notch1 oncoproteins, downregulation of metastatic and angiogenic gene expression, and reduction of NF-κB signaling pathway. Our findings provide a new strategy for treating highly lethal TNBC and offer a potential new drug candidate for combatting this aggressive disease.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13058-021-01488-7.

Overcoming Therapy Resistance and Relapse in TNBC: Emerging Technologies to Target Breast Cancer-Associated Fibroblasts

Breast cancer is the most diagnosed cancer and is the leading cause of cancer mortality in women. Triple-negative breast cancer (TNBC) is an aggressive form of breast cancer. Often, TNBC is not effectively treated due to the lack of specificity of conventional therapies and results in relapse and metastasis. Breast cancer-associated fibroblasts (BCAFs) are the predominant cells that reside in the tumor microenvironment (TME) and regulate tumorigenesis, progression and metastasis, and therapy resistance. BCAFs secrete a wide range of factors, including growth factors, chemokines, and cytokines, some of which have been proved to lead to a poor prognosis and clinical outcomes. This TME component has been emerging as a promising target due to its crucial role in cancer progression and chemotherapy resistance. A number of therapeutic candidates are designed to effectively target BCAFs with a focus on their tumor-promoting properties and tumor immune response. This review explores various agents targeting BCAFs in TNBC, including small molecules, nucleic acid-based agents, antibodies, proteins, and finally, nanoparticles.

The tumour-associated Tn antigen fosters lung metastasis and recruitment of regulatory T cells in triple negative breast cancer

Cancer is a leading cause of death worldwide, accounting for nearly 10 million deaths. Among breast cancers (BC) subtypes, triple-negative (TN) BC, is characterized by metastatic progression and poor patient prognosis. Although, TNBC is initially sensitive to chemotherapy, many TNBC patients rapidly develop resistance, at which point metastatic disease is highly lethal. Cancer cells present phenotypic changes or molecular signatures that distinguish them from healthy cells. The Tn antigen (GalNAc-O-Thr/Ser), that constitutes a powerful tool as tumour marker, was recently reported to contribute to tumour growth. However, its role in BC-derived metastasis has not yet been addressed. In this work we generated a pre-clinical orthotopic Tn+ model of metastatic TNBC, that mimics the patient surgical treatment and is useful to study the role of Tn in metastasis and immunoregulation. We obtained two different cell clones which differed in their Tn antigen expression: a high Tn-expressing and a non-expressing clone. Interestingly, the Tn-positive cell line generated significantly larger tumours and higher degree of lung metastases associated with a lower survival rate than the Tn-negative and parental cell line. Furthermore, we also found that both tumours and draining-lymph nodes from Tn+-tumour bearing mice presented a higher frequency of CD4+ FoxP3+ T cells, while their splenocytes expressed higher levels of IL-10. In conclusion, this work suggests that the Tn antigen participates in breast tumour growth and spreading, favouring metastases to the lungs that are associated to an immunoregulatory state, suggesting that Tn-based immunotherapy could be a strategy of choice to treat these tumours.

KIAA1522 is a new biomarker of promoting the tumorigenesis and distant metastasis of colorectal carcinoma

PURPOSE

Our research was absorbed into exploring the expression, clinicopathological value, biological significance and signaling pathway of KIAA1522 in colorectal carcinoma and its distant metastasis.

MATERIALS AND METHODS

The expression of KIAA1522 and survival analysis in colorectal carcinoma (CRC) were assessed using GEPIA databases. Then we evaluated the expression of KIAA1522 immunohistochemically in tissue samples of 57 patients with colorectal carcinoma liver metastasis (CRLM). The correlations between the expression of KIAA1522, clinical significance and prognosis of these 57 patients with CRLM were analyzed. The migration and invasion of KIAA1522 were explored by western blotting, CCK-8, colony formation, flow cytometry, wound healing assays and transwell invasion in vitro and tail vein injection models in vivo. Then, transcriptome sequencing and gene set enrichment analysis was performed to identify the signaling pathways involved, while western blotting analysis and immunohistochemistry (IHC) were used to identify the expression of key genes in Notch signaling.

RESULTS

KIAA1522 was overexpressed in CRLM tissues and colon cancer cell lines, and the expression of KIAA1522 in metastatic sites was positively correlated with that in primary sites. In addition, the overexpression of KIAA1522 is associated with poor clinicopathological features. Survival analysis showed that the overexpression of KIAA1522 predicted a low overall survival rate in patients with CRLM. Functional studies suggested that KIAA1522 promotes the proliferation, invasion and migration of colon carcinoma in vitro. KIAA1522 could promote distant metastasis of CRC in vivo. Moreover, KIAA1522 upregulated the Notch signaling pathway in colorectal cancer cell lines in vitro and lung metastatic nodes in vivo.

CONCLUSION

In conclusion, it is suggested that the upregulation of KIAA1522 might promote the tumorigenicity and metastasis of colorectal carcinoma through Notch signaling pathway. KIAA1522 plays a carcinogenic role in the metastasis of colorectal carcinoma and might serve as a new molecular target for the treatment.

A review on epidermal growth factor receptor's role in breast and non-small cell lung cancer

Epithelial growth factor receptor (EGFR) is a cell surface transmembrane receptor that mediates the tyrosine signaling pathway to carry the extracellular messages inside the cell and thereby alter the function of nucleus. This leads to the generation of various protein products to up or downregulate the cellular function. It is encoded by cell erythroblastosis virus oncogene B1, so called C-erb B1/ERBB2/HER-2 gene that acts as a proto-oncogene. It belongs to the HER-2 receptor-family in breast cancer and responds best with anti-Herceptin therapy (anti-tyrosine kinase monoclonal antibody). HER-2 positive breast cancer patient exhibits worse prognosis without Herceptin therapy. Similar incidence and prognosis are reported in other epithelial neoplasms like EGFR + lung non-small cell carcinoma and glioblastoma (grade IV brain glial tumor). Present study highlights the role and connectivity of EGF with various cancers via signaling pathways, cell surface receptors mechanism, macromolecules, mitochondrial genes and neoplasm. Present study describes the EGFR associated gene expression profiling (in breast cancer and NSCLC), relation between mitrochondrial genes and carcinoma, and several in vitro and in vivo models to screen the synergistic effect of various combination treatments. According to this study, although clinical studies including targeted treatments, immunotherapies, radiotherapy, TKi-EGFR combined targeted therapy have been carried out to investigate the synergism of combination therapy; however still there is a gap to apply the scenarios of experimental and clinical studies for further developments. This review will give an idea about the transition from experimental to most advanced clinical studies with different combination drug strategies to treat cancer.

Targeting Notch to Maximize Chemotherapeutic Benefits: Rationale, Advanced Strategies, and Future Perspectives

Simple Summary

The Notch signaling pathway regulates cell proliferation, apoptosis, stem cell self-renewal, and differentiation in a context-dependent fashion both during embryonic development and in adult tissue homeostasis. Consistent with its pleiotropic physiological role, unproper activation of the signaling promotes or counteracts tumor pathogenesis and therapy response in distinct tissues. In the last twenty years, a wide number of studies have highlighted the anti-cancer potential of Notch-modulating agents as single treatment and in combination with the existent therapies. However, most of these strategies have failed in the clinical exploration due to dose-limiting toxicity and low efficacy, encouraging the development of novel agents and the design of more appropriate combinations between Notch signaling inhibitors and chemotherapeutic drugs with improved safety and effectiveness for distinct types of cancer.

Abstract

Notch signaling guides cell fate decisions by affecting proliferation, apoptosis, stem cell self-renewal, and differentiation depending on cell and tissue context. Given its multifaceted function during tissue development, both overactivation and loss of Notch signaling have been linked to tumorigenesis in ways that are either oncogenic or oncosuppressive, but always context-dependent. Notch signaling is critical for several mechanisms of chemoresistance including cancer stem cell maintenance, epithelial-mesenchymal transition, tumor-stroma interaction, and malignant neovascularization that makes its targeting an appealing strategy against tumor growth and recurrence. During the last decades, numerous Notch-interfering agents have been developed, and the abundant preclinical evidence has been transformed in orphan drug approval for few rare diseases. However, the majority of Notch-dependent malignancies remain untargeted, even if the application of Notch inhibitors alone or in combination with common chemotherapeutic drugs is being evaluated in clinical trials. The modest clinical success of current Notch-targeting strategies is mostly due to their limited efficacy and severe on-target toxicity in Notch-controlled healthy tissues. Here, we review the available preclinical and clinical evidence on combinatorial treatment between different Notch signaling inhibitors and existent chemotherapeutic drugs, providing a comprehensive picture of molecular mechanisms explaining the potential or lacking success of these combinations.

Transcription Factor RBPJL Is Able to Repress Notch Target Gene Expression but Is Non-Responsive to Notch Activation

Simple Summary

The transcription factor RBPJ is an integral part of the Notch signaling cascade. RBPJ can function as a coactivator when Notch signaling is activated but acts as a repressor in the absence of a Notch stimulus. Here, we characterized the function of RBPJL, a pancreas-specific paralog of RBPJ. Upon depletion of RBPJ using CRISPR/Cas9, we observed specific upregulation of Notch target gene expression. Reconstitution with RBPJL can compensate for the lack of RBPJ function in the repression of Notch target genes but is not able to mediate the Notch-dependent activation of gene expression. On the molecular level, we identified a limited capacity of RBPJL to interact with activated Notch1–4.

Abstract

The Notch signaling pathway is an evolutionary conserved signal transduction cascade present in almost all tissues and is required for embryonic and postnatal development, as well as for stem cell maintenance, but it is also implicated in tumorigenesis including pancreatic cancer and leukemia. The transcription factor RBPJ forms a coactivator complex in the presence of a Notch signal, whereas it represses Notch target genes in the absence of a Notch stimulus. In the pancreas, a specific paralog of RBPJ, called RBPJL, is expressed and found as part of the heterotrimeric PTF1-complex. However, the function of RBPJL in Notch signaling remains elusive. Using molecular modeling, biochemical and functional assays, as well as single-molecule time-lapse imaging, we show that RBPJL and RBPJ, despite limited sequence homology, possess a high degree of structural similarity. RBPJL is specifically expressed in the exocrine pancreas, whereas it is mostly undetectable in pancreatic tumour cell lines. Importantly, RBPJL is not able to interact with Notch−1 to −4 and it does not support Notch-mediated transactivation. However, RBPJL can bind to canonical RBPJ DNA elements and shows migration dynamics comparable to that of RBPJ in the nuclei of living cells. Importantly, RBPJL is able to interact with SHARP/SPEN, the central corepressor of the Notch pathway. In line with this, RBPJL is able to fully reconstitute transcriptional repression at Notch target genes in cells lacking RBPJ. Together, RBPJL can act as an antagonist of RBPJ, which renders cells unresponsive to the activation of Notch.

Reduction of Derlin activity suppresses Notch-dependent tumours in the C. elegans germ line

Regulating the balance between self-renewal (proliferation) and differentiation is key to the long-term functioning of all stem cell pools. In the Caenorhabditis elegans germline, the primary signal controlling this balance is the conserved Notch signaling pathway. Gain-of-function mutations in the GLP-1/Notch receptor cause increased stem cell self-renewal, resulting in a tumour of proliferating germline stem cells. Notch gain-of-function mutations activate the receptor, even in the presence of little or no ligand, and have been associated with many human diseases, including cancers. We demonstrate that reduction in CUP-2 and DER-2 function, which are Derlin family proteins that function in endoplasmic reticulum-associated degradation (ERAD), suppresses the C. elegans germline over-proliferation phenotype associated with glp-1(gain-of-function) mutations. We further demonstrate that their reduction does not suppress other mutations that cause over-proliferation, suggesting that over-proliferation suppression due to loss of Derlin activity is specific to glp-1/Notch (gain-of-function) mutations. Reduction of CUP-2 Derlin activity reduces the expression of a read-out of GLP-1/Notch signaling, suggesting that the suppression of over-proliferation in Derlin loss-of-function mutants is due to a reduction in the activity of the mutated GLP-1/Notch(GF) receptor. Over-proliferation suppression in cup-2 mutants is only seen when the Unfolded Protein Response (UPR) is functioning properly, suggesting that the suppression, and reduction in GLP-1/Notch signaling levels, observed in Derlin mutants may be the result of activation of the UPR. Chemically inducing ER stress also suppress glp-1(gf) over-proliferation but not other mutations that cause over-proliferation. Therefore, ER stress and activation of the UPR may help correct for increased GLP-1/Notch signaling levels, and associated over-proliferation, in the C. elegans germline.

Notch signaling is a highly conserved signaling pathway that is utilized in many cell fate decisions in many organisms. In the C. elegans germline, Notch signaling is the primary signal that regulates the balance between stem cell proliferation and differentiation. Notch gain-of-function mutations cause the receptor to be active, even when a signal that is normally needed to activate the receptor is absent. In the germline of C. elegans, gain-of-function mutations in GLP-1, a Notch receptor, results in over-proliferation of the stem cells and tumour formation. Here we demonstrate that a reduction or loss of Derlin activity, which is a conserved family of proteins involved in endoplasmic reticulum-associated degradation (ERAD), suppresses over-proliferation due to GLP-1/Notch gain-of-function mutations. Furthermore, we demonstrate that a surveillance mechanism utilized in cells to monitor and react to proteins that are not folded properly (Unfolded Protein Response-UPR) must be functioning well in order for the loss of Derlin activity to supress over-proliferation caused by glp-1/Notch gain-of-function mutations. This suggests that activation of the UPR may be the mechanism at work for suppressing this type of over-proliferation, when Derlin activity is reduced. Therefore, decreasing Derlin activity may be a means of reducing the impact of phenotypes and diseases due to certain Notch gain-of-function mutations.

Drivers and suppressors of triple-negative breast cancer

To identify regulators of triple-negative breast cancer (TNBC), gene expression profiles of malignant parts of TNBC (mTNBC) and normal adjacent (nadj) parts of the same breasts have been compared. We are interested in the roles of estrogen receptor β (ERβ) and the cytochrome P450 family (CYPs) as drivers of TNBC. We examined by RNA sequencing the mTNBC and nadj parts of five women. We found more than a fivefold elevation in mTNBC of genes already known to be expressed in TNBC: BIRC5/survivin, Wnt-10A and -7B, matrix metalloproteinases (MMPs), chemokines, anterior gradient proteins, and lysophosphatidic acid receptor and the known basal characteristics of TNBC, sox10, ROPN1B, and Col9a3. There were two unexpected findings: 1) a strong induction of CYPs involved in activation of fatty acids (CYP4), and in inactivation of calcitriol (CYP24A1) and retinoic acid (CYP26A1); and 2) a marked down-regulation of FOS, FRA1, and JUN, known tethering partners of ERβ. ERβ is expressed in 20 to 30% of TNBCs and is being evaluated as a target for treating TNBC. We used ERβ⁺ TNBC patient-derived xenografts in mice and found that the ERβ agonist LY500703 had no effect on growth or proliferation. Expression of CYPs was confirmed by immunohistochemistry in formalin-fixed and paraffin-embedded (FFPE) TNBC. In TNBC cell lines, the CYP4Z1-catalyzed fatty acid metabolite 20-hydroxyeicosatetraenoic acid (20-HETE) increased proliferation, while calcitriol decreased proliferation but only after inhibition of CYP24A1. We conclude that CYP-mediated pathways can be drivers of TNBC but that ERβ is unlikely to be a tumor suppressor because the absence of its main tethering partners renders ERβ functionless on genes involved in proliferation and inflammation.

An insight into the cancer stem cell survival pathways involved in chemoresistance in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is the most complex, aggressive and fatal subtype of breast cancer. Owing to the lack of targeted therapy and heterogenic nature of TNBC, chemotherapy remains the sole treatment option for TNBC, with taxanes and anthracyclines representing the general chemotherapeutic regimen in TNBC therapy. But unfortunately, patients develop resistance to the existing chemotherapeutic regimen, resulting in approximately 90% treatment failure. Breast cancer stem cells (BCSCs) are one of the major causes for the development of chemoresistance in TNBC patients. After surviving the chemotherapy damage, the presence of BCSCs results in relapse and recurrence of TNBC. Several pathways are known to regulate BCSCs' survival, such as the Wnt/β-catenin, Hedgehog, JAK/STAT and HIPPO pathways. Therefore it is imperative to target these pathways in the context of eliminating chemoresistance. In this review we will discuss the novel strategies and various preclinical and clinical studies to give an insight into overcoming TNBC chemoresistance. We present a detailed account of recent studies carried out that open an exciting perspective in relation to the mechanisms of chemoresistance.

Targeted Drug Therapy to Overcome Chemoresistance in Triple-negative Breast Cancer

Triple-negative Breast Cancer (TNBC) is the most aggressive and prevailing breast cancer subtype. The chemotherapeutics used in the treatment of TNBC suffer from chemoresistance, dose-limiting toxicities and off-target side effects. As a result, conventional chemotherapeutics are unable to prevent tumor growth, metastasis and result in failure of therapy. Various new targets such as BCSCs surface markers (CD44, CD133, ALDH1), signaling pathways (IL-6/JAK/STAT3, notch), pro and anti-apoptotic proteins (Bcl-2, Bcl-xL, DR4, DR5), hypoxic factors (HIF-1α, HIF-2α) and drug efflux transporters (ABCC1, ABCG2 and ABCB1) have been exploited to treat TNBC. Further, to improve the efficacy and safety of conventional chemotherapeutics, researchers have tried to deliver anticancer agents specifically to the TNBCs using nanocarrier based drug delivery. In this review, an effort has been made to highlight the various factors responsible for the chemoresistance in TNBC, novel molecular targets of TNBC and nano-delivery systems employed to achieve sitespecific drug delivery to improve efficacy and reduce off-target side effects.

Precision Medicine and Triple-Negative Breast Cancer: Current Landscape and Future Directions

Simple Summary

The implementation of precision medicine will revolutionize cancer treatment paradigms. Notably, this goal is not far from reality: genetically similar cancers can be treated similarly. The heterogeneous nature of triple-negative breast cancer (TNBC) made it a suitable candidate to practice precision medicine. Using TNBC molecular subtyping and genomic profiling, a precision medicine-based clinical trial is ongoing. This review summarizes the current landscape and future directions of precision medicine and TNBC.

Abstract

Triple-negative breast cancer (TNBC) is an aggressive and heterogeneous subtype of breast cancer associated with a high recurrence and metastasis rate that affects African-American women disproportionately. The recent approval of targeted therapies for small subgroups of TNBC patients by the US ‘Food and Drug Administration’ is a promising development. The advancement of next-generation sequencing, particularly somatic exome panels, has raised hopes for more individualized treatment plans. However, the use of precision medicine for TNBC is a work in progress. This review will discuss the potential benefits and challenges of precision medicine for TNBC. A recent clinical trial designed to target TNBC patients based on their subtype-specific classification shows promise. Yet, tumor heterogeneity and sub-clonal evolution in primary and metastatic TNBC remain a challenge for oncologists to design adaptive precision medicine-based treatment plans.

A High Epigenetic Risk Score Shapes the Non-Inflamed Tumor Microenvironment in Breast Cancer

Background: Epigenetic dysregulation via aberrant DNA methylation has gradually become recognized as an efficacious signature for predicting tumor prognosis and response to therapeutic targets. However, reliable DNA methylation biomarkers describing tumorigenesis remain to be comprehensively explored regarding their prognostic and therapeutic potential in breast cancer (BC). Methods: Whole-genome methylation datasets integrated from the Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) database were profiled (n = 1,268). A three-stage selection procedure (discovery, training, and external validation) was utilized to screen out the prominent biomarkers and establish a robust risk score from more than 300,000 CpG sites after quality control, rigorous filtering, and reducing dimension. Moreover, gene set enrichment analyses guided us to systematically correlate this epigenetic risk score with immunological characteristics, including immunomodulators, anti-cancer immunity cycle, immune checkpoints, tumor-infiltrating immune cells and a series of signatures upon modulating components within BC tumor microenvironment (TME). Multi-omics data analyses were performed to decipher specific genomic alterations in low- and high-risk patients. Additionally, we also analyzed the role of risk score in predicting response to several treatment options. Results: A 10-CpG-based prognostic signature which could significantly and independently categorize BC patients into distinct prognoses was established and sufficiently validated. And we hypothesize that this signature designs a non-inflamed TME in BC based on the evidence that the derived risk score is negatively correlated with tumor-associated infiltrating immune cells, anti-cancer immunity cycle, immune checkpoints, immune cytolytic activity, T cell inflamed score, immunophenoscore, and the vast majority of immunomodulators. The identified high-risk patients were characterized by upregulation of immune inhibited oncogenic pathways, higher TP53 mutation and copy number burden, but lower response to cancer immunotherapy and chemotherapy. Conclusion: Our work highlights the complementary roles of 10-CpG-based signature in estimating overall survival in BC patients, shedding new light on investigating failed events concerning immunotherapy at present.

Notch Signalling in Breast Development and Cancer

The Notch signalling pathway is a highly conserved developmental signalling pathway, with vital roles in determining cell fate during embryonic development and tissue homeostasis. Aberrant Notch signalling has been implicated in many disease pathologies, including cancer. In this review, we will outline the mechanism and regulation of the Notch signalling pathway. We will also outline the role Notch signalling plays in normal mammary gland development and how Notch signalling is implicated in breast cancer tumorigenesis and progression. We will cover how Notch signalling controls several different hallmarks of cancer within epithelial cells with sections focussed on its roles in proliferation, apoptosis, invasion, and metastasis. We will provide evidence for Notch signalling in the breast cancer stem cell phenotype, which also has implications for therapy resistance and disease relapse in breast cancer patients. Finally, we will summarise the developments in therapeutic targeting of Notch signalling, and the pros and cons of this approach for the treatment of breast cancer.

Regulation of cancer stem cells in triple negative breast cancer

Triple Negative Breast Cancer (TNBC) is the most lethal subtype of breast cancer. Despite the successes of emerging targeted therapies, relapse, recurrence, and therapy failure rates in TNBC significantly outpace other subtypes of breast cancer. Mounting evidence suggests accumulation of therapy resistant Cancer Stem Cell (CSC) populations within TNBCs contributes to poor clinical outcomes. These CSCs are enriched in TNBC compared to non-TNBC breast cancers. The mechanisms underlying CSC accumulation have been well-characterized and discussed in other reviews. In this review, we focus on TNBC-specific mechanisms that allow the expansion and activity of self-renewing CSCs. We highlight cellular signaling pathways and transcription factors, specifically enriched in TNBC over non-TNBC breast cancer, contributing to stemness. We also analyze publicly available single-cell RNA-seq data from basal breast cancer tumors to highlight the potential of emerging bioinformatic approaches in identifying novel drivers of stemness in TNBC and other cancers.

Potentiating Therapeutic Effects of Epidermal Growth Factor Receptor Inhibition in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is a subset of breast cancer with aggressive characteristics and few therapeutic options. The lack of an appropriate therapeutic target is a challenging issue in treating TNBC. Although a high level expression of epidermal growth factor receptor (EGFR) has been associated with a poor prognosis among patients with TNBC, targeted anti-EGFR therapies have demonstrated limited efficacy for TNBC treatment in both clinical and preclinical settings. However, with the advantage of a number of clinically approved EGFR inhibitors (EGFRis), combination strategies have been explored as a promising approach to overcome the intrinsic resistance of TNBC to EGFRis. In this review, we analyzed the literature on the combination of EGFRis with other molecularly targeted therapeutics or conventional chemotherapeutics to understand the current knowledge and to provide potential therapeutic options for TNBC treatment.

The Role of Notch3 Signaling in Cancer Stemness and Chemoresistance: Molecular Mechanisms and Targeting Strategies

Aberrant Notch signaling profoundly affects cancer progression. Especially the Notch3 receptor was found to be dysregulated in cancer, where its expression is correlated with worse clinicopathological features and poor prognosis. The activation of Notch3 signaling is closely related to the activation of cancer stem cells (CSCs), a small subpopulation in cancer that is responsible for cancer progression. In addition, Notch3 signaling also contributes to tumor chemoresistance against several drugs, including doxorubicin, platinum, taxane, epidermal growth factor receptor (EGFR)–tyrosine kinase inhibitors (TKIs) and gemcitabine, through complex mechanisms. In this review, we mainly focus on discussing the molecular mechanisms by which Notch3 modulates cancer stemness and chemoresistance, as well as other cancer behaviors including metastasis and angiogenesis. What’s more, we propose potential treatment strategies to block Notch3 signaling, such as non-coding RNAs, antibodies and antibody-drug conjugates, providing a comprehensive reference for research on precise targeted cancer therapy.

To Be, or Notch to Be: Mediating Cell Fate from Embryogenesis to Lymphopoiesis

Notch signaling forms an evolutionarily conserved juxtacrine pathway crucial for cellular development. Initially identified in Drosophila wing morphogenesis, Notch signaling has since been demonstrated to play pivotal roles in governing mammalian cellular development in a large variety of cell types. Indeed, abolishing Notch constituents in mouse models result in embryonic lethality, demonstrating that Notch signaling is critical for development and differentiation. In this review, we focus on the crucial role of Notch signaling in governing embryogenesis and differentiation of multiple progenitor cell types. Using hematopoiesis as a diverse cellular model, we highlight the role of Notch in regulating the cell fate of common lymphoid progenitors. Additionally, the influence of Notch through microenvironment interplay with lymphoid cells and how dysregulation influences disease processes is explored. Furthermore, bi-directional and lateral Notch signaling between ligand expressing source cells and target cells are investigated, indicating potentially novel therapeutic options for treatment of Notch-mediated diseases. Finally, we discuss the role of cis-inhibition in regulating Notch signaling in mammalian development.

The Natural Products and Extracts: Anti-Triple-Negative Breast Cancer in Vitro

Triple-negative breast cancer (TNBC) makes up 15 % to 20 % of all breast cancer (BC) cases, and represents one of the most challenging malignancies to treat. For many years, chemotherapy has been the main treatment option for TNBC. Natural products isolated from marine organisms and terrestrial organisms with great structural diversity and high biochemical specificity form a compound library for the assessment and discovery of new drugs. In this review, we mainly focused on natural compounds and extracts (from marine and terrestrial environments) with strong anti-TNBC activities (IC₅₀ <100 μM) and their possible mechanisms reported in the past six years (2015-2021).

Inhibiting of TACC3 Promotes Cell Proliferation, Cell Invasion and the EMT Pathway in Breast Cancer

Accumulating evidences indicate that transforming acidic coiled-coil 3 (TACC3) is a tumor-related gene, was highly expressed in a variety of human cancers, which is involved in cancer development. However, the potential role of TACC3 in breast cancer remains largely unknown. In the present study, we found that TACC3 was highly-expressed in breast cancer tissues, and its level was positively correlated with the clinical features of breast cancer patients. Specifically, TACC3 expression was significantly associated with the estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2) status, nodal status, the scarff-bloom-richardson (SBR) grade, nottingham prognostic index (NPI), age, subtypes, and triple-negative and basal-like status, suggesting that TACC3 may be a potential diagnostic indicator of breast cancer. Furthermore, functional studies have shown that inhibition of TACC3 can significantly promote the cell proliferation and viability of breast cancer cells. Moreover, TACC3 knockdown suppressed the expression of E-cadherin, but increased the expression of N-cadherin, Snail, ZEB1, and TWIST, which indicate that TACC3 may impact the migration of breast cancer cells in vitro. Taken together, these findings indicate that TACC3 may serve as a prognostic and therapeutic indicator of breast cancer.

Actin-Like Protein 8 Promotes the Progression of Triple-Negative Breast Cancer via Activating PI3K/AKT/mTOR Pathway

Objective

The purpose of this study was to investigate the function of actin-like protein 8 (ACTL8) on triple-negative breast cancer (TNBC) and its potential mechanisms.

Methods

In our study, ACTL8 expression and the prognostic values of ACTL8 were evaluated via the dataset from the Cancer Genome Atlas (TCGA). At the same time, the expression of ACTL8 in TNBC cells was measured by Western blot and qRT-PCR. Then, the effects of ACTL8 on the growth and metastasis of TNBC were investigated by using 5-ethynyl-20-deoxyuridine (EdU), colony formation, flow cytometry, wound healing and transwell assays. Mechanistically, Western blot was performed to confirm the interaction between ACTL8 and phosphatidylinositol 3′-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) signaling pathway in TNBC.

Results

ACTL8 expression was upregulated in TNBC and associated with the poor prognosis of TNBC. Silencing ACTL8 suppressed the proliferation, migration and invasion, also promoted the apoptosis in MDA-MB-231 and BT-549 cells. Moreover, we found that silencing ACTL8 could inhibit the activation of PI3K/AKT/mTOR signaling pathway in MDA-MB-231 and BT-549 cells. Meanwhile, the impact of silencing ACTL8 on the proliferation, apoptosis, migration and invasion was enhanced by PI3K/AKT/mTOR pathway inhibitor (Wortmannin) and reversed by PI3K/AKT/mTOR pathway activator (740Y-P).

Conclusion

Our data demonstrated that ACTL8 may facilitate the proliferation, migration and invasion, while inhibiting apoptosis through activating PI3K/Akt/mTOR signaling pathway in TNBC.

Standard of Care and Promising New Agents for the Treatment of Mesenchymal Triple-Negative Breast Cancer

The pathologic definition of triple negative breast cancer (TNBC) relies on the absence of expression of estrogen, progesterone and HER2 receptors. However, this BC subgroup is distinguished by a wide biological, molecular and clinical heterogeneity. Among the intrinsic TNBC subtypes, the mesenchymal type is defined by the expression of genes involved in the epithelial to mesenchymal transition, stromal interaction and cell motility. Moreover, it shows a high expression of genes involved in proliferation and an immune-suppressive microenvironment. Several molecular alterations along different pathways activated during carcinogenesis and tumor progression have been outlined and could be involved in immune evasion mechanisms. Furthermore, reverting epithelial to mesenchymal transition process could lead to the overcoming of immune-resistance. This paper reviews the current knowledge regarding the mesenchymal TNBC subtype and its response to conventional therapeutic strategies, as well as to some promising molecular target agents and immunotherapy. The final goal is a tailored combination of cytotoxic drugs, target agents and immunotherapy in order to restore immunocompetence in mesenchymal breast cancer patients.

RBM10 Regulates Tumor Apoptosis, Proliferation, and Metastasis

The RNA-binding motif protein 10 (RBM10) is involved in alternative splicing and modifies mRNA post-transcriptionally. RBM10 is abnormally expressed in the lung, breast, and colorectal cancer, female genital tumors, osteosarcoma, and other malignant tumors. It can inhibit proliferation, promote apoptosis, and inhibit invasion and metastasis. RBM10 has long been considered a tumor suppressor because it promotes apoptosis through the regulation of the MDM2-p53 negative feedback loop, Bcl-2, Bax, and other apoptotic proteins and inhibits proliferation through the Notch signaling and rap1a/Akt/CREB pathways. However, it has been recently demonstrated that RBM10 can also promote cancer. Given these different views, it is necessary to summarize the research progress of RBM10 in various fields to reasonably analyze the underlying molecular mechanisms, and provide new ideas and directions for the clinical research of RBM10 in various cancer types. In this review, we provide a new perspective on the reasons for these opposing effects on cancer biology, molecular mechanisms, research progress, and clinical value of RBM10.

Triple-negative breast cancer: promising prognostic biomarkers currently in development

Introduction: Triple-negative breast cancer (TNBC) is an aggressive type of breast cancer associated with poor prognosis and limited treatment options. Validated prognostic and predictive biomarkers are needed to guide treatment decisions and prognostication.Areas covered: In this review, we discuss established and developing prognostic and predictive biomarkers in TNBC and associated emerging and approved therapies. Biomarkers reviewed include epidermal growth factor receptor (EGFR), vascular endothelial growth factors (VEGF), fibroblast growth factor receptor (FGFR), human epidermal growth factor receptor 2 (HER2), androgen receptor, NOTCH signaling, oxidative stress/redox signaling, microRNAs, TP53 mutation, breast cancer susceptibility gene 1 or 2 (BRCA1/2) mutation/homologous recombination deficiency (HRD), NTRK gene fusion, PI3K/AKT/mTOR, immune biomarkers (programmed death-ligand 1 (PDL1), tumor-infiltrating lymphocytes (TILs), tumor mutational burden (TMB), neoantigens, defects in DNA mismatch repair proteins (dMMR)/microsatellite instability-high (MSI-H)), circulating tumor cells/cell-free DNA, novel targets of antibody-drug conjugates, and residual disease.Expert opinion: Biomarker-driven care in the management of TNBC is increasing and has helped expand options for patients diagnosed with this subtype of breast cancer. Research efforts are ongoing to identify additional biomarkers and targeted treatment options with the ultimate goal of improving clinical outcomes and survivorship.

The role of EMT-related lncRNA in the process of triple-negative breast cancer metastasis

Triple-negative breast cancer (TNBC) is the most malignant and fatal subtype of breast cancer, which has characterized by negativity expression of ER, PR, and HER2. Metastasis is the main factor affecting the prognosis of TNBC, and the process of metastasis is related to abnormal activation of epithelial–mesenchymal transition (EMT). Recent studies have shown that long non-coding RNA (LncRNA) plays an important role in regulating the metastasis and invasion of TNBC. Therefore, based on the metastasis-related EMT signaling pathway, great efforts have confirmed that LncRNA is involved in the molecular mechanism of TNBC metastasis, which will provide new strategies to improve the treatment and prognosis of TNBC. In this review, we summarized many signal pathways related to EMT involved in the transfer process. The advances from the most recent studies of lncRNAs in the EMT-related signal pathways of TNBC metastasis. We also discussed the clinical research, application, and challenges of LncRNA in TNBC.

Dll1+ quiescent tumor stem cells drive chemoresistance in breast cancer through NF-κB survival pathway

Development of chemoresistance in breast cancer patients greatly increases mortality. Thus, understanding mechanisms underlying breast cancer resistance to chemotherapy is of paramount importance to overcome this clinical challenge. Although activated Notch receptors have been associated with chemoresistance in cancer, the specific Notch ligands and their molecular mechanisms leading to chemoresistance in breast cancer remain elusive. Using conditional knockout and reporter mouse models, we demonstrate that tumor cells expressing the Notch ligand Dll1 is important for tumor growth and metastasis and bear similarities to tumor-initiating cancer cells (TICs) in breast cancer. RNA-seq and ATAC-seq using reporter models and patient data demonstrated that NF-κB activation is downstream of Dll1 and is associated with a chemoresistant phenotype. Finally, pharmacological blocking of Dll1 or NF-κB pathway completely sensitizes Dll1+ tumors to chemotherapy, highlighting therapeutic avenues for chemotherapy resistant breast cancer patients in the near future.

Functional Gene Expression Differentiation of the Notch Signaling Pathway in Female Reproductive Tract Tissues-A Comprehensive Review With Analysis

The Notch pathway involves evolutionarily conserved signaling regulating the development of the female tract organs such as breast, ovary, cervix, and uterine endometrium. A great number of studies revealed Notch aberrancies in association with their carcinogenesis and disease progression, the management of which is still challenging. The present study is a comprehensive review of the available literature on Notch signaling during the normal development and carcinogenesis of the female tract organs. The review has been enriched with our analyses of the TCGA data including breast, cervical, ovarian, and endometrial carcinomas concerning the effects of Notch signaling at two levels: the core components and downstream effectors, hence filling the lack of global overview of Notch-driven carcinogenesis and disease progression. Phenotype heterogeneity regarding Notch signaling was projected in two uniform manifold approximation and projection algorithm dimensions, preceded by the principal component analysis step reducing the data burden. Additionally, overall and disease-free survival analyses were performed with the optimal cutpoint determination by Evaluate Cutpoints software to establish the character of particular Notch components in tumorigenesis. In addition to the review, we demonstrated separate models of the examined cancers of the Notch pathway and its targets, although expression profiles of all normal tissues were much more similar to each other than to its cancerous compartments. Such Notch-driven cancerous differentiation resulted in a case of opposite association with DFS and OS. As a consequence, target genes also show very distinct profiles including genes associated with cell proliferation and differentiation, energy metabolism, or the EMT. In conclusion, the observed Notch associations with the female tract malignancies resulted from differential expression of target genes. This may influence a future analysis to search for new therapeutic targets based on specific Notch pathway profiles.

A Dynamic Role of Mastermind-Like 1: A Journey Through the Main (Path)ways Between Development and Cancer

Major signaling pathways, such as Notch, Hedgehog (Hh), Wnt/β-catenin and Hippo, are targeted by a plethora of physiological and pathological stimuli, ultimately resulting in the modulation of genes that act coordinately to establish specific biological processes. Many biological programs are strictly controlled by the assembly of multiprotein complexes into the nucleus, where a regulated recruitment of specific transcription factors and coactivators on gene promoter region leads to different transcriptional outcomes. MAML1 results to be a versatile coactivator, able to set up synergistic interlinking with pivotal signaling cascades and able to coordinate the network of cross-talking pathways. Accordingly, despite its original identification as a component of the Notch signaling pathway, several recent reports suggest a more articulated role for MAML1 protein, showing that it is able to sustain/empower Wnt/β-catenin, Hh and Hippo pathways, in a Notch-independent manner. For this reason, MAML1 may be associated to a molecular “switch”, with the function to control the activation of major signaling pathways, triggering in this way critical biological processes during embryonic and post-natal life. In this review, we summarize the current knowledge about the pleiotropic role played by MAML proteins, in particular MAML1, and we recapitulate how it takes part actively in physiological and pathological signaling networks. On this point, we also discuss the contribution of MAML proteins to malignant transformation. Accordingly, genetic alterations or impaired expression of MAML proteins may lead to a deregulated crosstalk among the pathways, culminating in a series of pathological disorders, including cancer development. Given their central role, a better knowledge of the molecular mechanisms that regulate the interplay of MAML proteins with several signaling pathways involved in tumorigenesis may open up novel opportunities for an attractive molecular targeted anticancer therapy.

Thioridazine hydrochloride: an antipsychotic agent that inhibits tumor growth and lung metastasis in triple-negative breast cancer via inducing G0/G1 arrest and apoptosis

ABBREVIATIONS

CCK8: Cell Counting Kit-8; CDK: cyclin-dependent kinase; DRD2: dopamine D2 receptor; ERK1/2: extracellular signal-regulated kinase 1/2; GAPDH: glyceraldehyde 3-phosphate dehydrogenase; H&E: hematoxylin and eosin; MMP: membrane potential; NAC: N-acetyl-L-cysteine; PI: Propidium iodide; Rh123: rhodamine-123; ROS: reactive oxygen species; TBST: tris-buffered saline containing 0.1% Tween 20 TNBC: Triple-negative breast cancer; Thi-hyd: Thioridazine hydrochloride.

Targeting Notch in oncology: the path forward

Notch signalling is involved in many aspects of cancer biology, including angiogenesis, tumour immunity and the maintenance of cancer stem-like cells. In addition, Notch can function as an oncogene and a tumour suppressor in different cancers and in different cell populations within the same tumour. Despite promising preclinical results and early-phase clinical trials, the goal of developing safe, effective, tumour-selective Notch-targeting agents for clinical use remains elusive. However, our continually improving understanding of Notch signalling in specific cancers, individual cancer cases and different cell populations, as well as crosstalk between pathways, is aiding the discovery and development of novel investigational Notch-targeted therapeutics.

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

The cellular heterogeneity of breast cancers still represents a major therapeutic challenge. The latest genomic studies have classified breast cancers in distinct clusters to inform the therapeutic approaches and predict clinical outcomes. The mammary epithelium is composed of luminal and basal cells, and this seemingly hierarchical organization is dependent on various stem cells and progenitors populating the mammary gland. Some cancer cells are conceptually similar to the stem cells as they can self-renew and generate bulk populations of nontumorigenic cells. Two models have been proposed to explain the cell of origin of breast cancer and involve either the reprogramming of differentiated mammary cells or the dysregulation of mammary stem cells or progenitors. Both hypotheses are not exclusive and imply the accumulation of independent mutational events. Cancer stem cells have been isolated from breast tumors and implicated in the development, metastasis, and recurrence of breast cancers. Recent advances in single-cell sequencing help deciphering the clonal evolution within each breast tumor. Still, few clinical trials have been focused on these specific cancer cell populations.

A Review of Natural Therapies Potentially Relevant in Triple Negative Breast Cancer Aimed at Targeting Cancer Cell Vulnerabilities

We reviewed the research into the mechanisms of growth of triple negative breast cancer (TNBC) based on laboratory pre-clinical studies that have shaped understanding of the disease over the past decade. In response to these findings, we propose an approach to potentially prevent cancer metabolic adaptation and recurrence. This paper collates pre-clinical results, first to determine the tumor’s mechanisms of growth and then to source natural substances that could potentially suppress those mechanisms. The results from in vivo and in vitro studies of TNBC were combined first to select 10 primary mechanisms (Hypoxia-inducible factor 1α, Hedgehog, MAPK, MTAP, NF-κ B, Notch, P13K, STAT3, and Wnt signaling pathways plus p53 and POL2A gene expression) that promote TNBC growth, and second to propose a treatment array of 21 natural compounds that suppress laboratory models of TNBC via these mechanisms. We included BRCA mutations in the review process, but only pathways with the most preclinical studies utilizing natural products were included. Then we outlined potential biomarkers to assess the changes in the micro-environment and monitor biochemical pathway suppression. This suppression-centric aim targets these mechanisms of growth with the goal of potentially halting tumor growth and preventing cancer cell metabolic adaptation. We chose TNBC to demonstrate this 5-step strategy of supplementary therapy, which may be replicated for other tumor types.

G protein-coupled oestrogen receptor promotes cell growth of non-small cell lung cancer cells via YAP1/QKI/circNOTCH1/m6A methylated NOTCH1 signalling

Results from various studies reveal that the role of G protein‐coupled oestrogen receptor (GPER) is cancer‐context dependent, and the function of GPER in non–small‐cell lung cancer (NSCLC) is still unclear. The present study demonstrated that neoplasm lung tissues expressed higher level of GPER compared with the normal lung tissues. The clinical data also showed that GPER expression level was positively correlated with the tumour stage of NSCLC. Our experimental data confirmed that GPER played an oncogenic role to promote cell growth of NSCLC cells. Mechanistic dissection revealed that GPER could modulate the NOTCH1 pathway to regulate cell growth in NSCLC cells. Further exploration of the mechanism demonstrated that GPER could up‐regulate circNOTCH1, which could compete with NOTCH1 mRNA for METTL14 binding. Because of the lack of m6A modification by METTL14 on the NOTCH1 mRNA, NOTCH1 mRNA was more stable and much easier to undergo protein translation. Subsequently, we found that GPER could prevent YAP1 phosphorylation and promote YAP1‐TEAD's transcriptional regulation on QKI, a transacting RNA‐binding factor involved in circRNA biogenesis, to facilitate circNOTCH1 generation. Supportively, data from preclinical mice model with implantation of H1299 cells also demonstrated that knock‐down of circNOTCH1 could block GPER‐induced NOTCH1 to suppress NSCLC tumour growth. Together, our data showed that GPER could promote NSCLC cell growth via regulating the YAP1/QKI/circNOTCH1/m6A methylated NOTCH1 pathway, and targeting our identified molecules may be a potentially therapeutic approach to suppress NSCLC development.

Cancer-driving mutations and variants of components of the membrane trafficking core machinery

The core machinery for vesicular membrane trafficking broadly comprises of coat proteins, RABs, tethering complexes and SNAREs. As cellular membrane traffic modulates key processes of mitogenic signaling, cell migration, cell death and autophagy, its dysregulation could potentially results in increased cell proliferation and survival, or enhanced migration and invasion. Changes in the levels of some components of the core machinery of vesicular membrane trafficking, likely due to gene amplifications and/or alterations in epigenetic factors (such as DNA methylation and micro RNA) have been extensively associated with human cancers. Here, we provide an overview of association of membrane trafficking with cancer, with a focus on mutations and variants of coat proteins, RABs, tethering complex components and SNAREs that have been uncovered in human cancer cells/tissues. The major cellular and molecular cancer-driving or suppression mechanisms associated with these components of the core membrane trafficking machinery shall be discussed.

Notch3 contributes to T-cell leukemia growth via regulation of the unfolded protein response

Unfolded protein response (UPR) is a conserved adaptive response that tries to restore protein homeostasis after endoplasmic reticulum (ER) stress. Recent studies highlighted the role of UPR in acute leukemias and UPR targeting has been suggested as a therapeutic approach. Aberrant Notch signaling is a common feature of T-cell acute lymphoblastic leukemia (T-ALL), as downregulation of Notch activity negatively affects T-ALL cell survival, leading to the employment of Notch inhibitors in T-ALL therapy. Here we demonstrate that Notch3 is able to sustain UPR in T-ALL cells, as Notch3 silencing favored a Bip-dependent IRE1α inactivation under ER stress conditions, leading to increased apoptosis via upregulation of the ER stress cell death mediator CHOP. By using Juglone, a naturally occurring naphthoquinone acting as an anticancer agent, to decrease Notch3 expression and induce ER stress, we observed an increased ER stress-associated apoptosis. Altogether our results suggest that Notch3 inhibition may prevent leukemia cells from engaging a functional UPR needed to compensate the Juglone-mediated ER proteotoxic stress. Notably, in vivo administration of Juglone to human T-ALL xenotransplant models significantly reduced tumor growth, finally fostering the exploitation of Juglone-dependent Notch3 inhibition to perturb the ER stress/UPR signaling in Notch3-dependent T-ALL subsets.

Retinoic Acid Sensitivity of Triple-Negative Breast Cancer Cells Characterized by Constitutive Activation of the notch1 Pathway: The Role of Rarβ

Triple-negative breast cancer (TNBC) is a heterogeneous disease that lacks effective therapeutic options. In this study, we profile eighteen TNBC cell lines for their sensitivity to the anti-proliferative action of all-trans retinoic acid (ATRA). The only three cell lines (HCC-1599, MB-157 and MDA-MB-157) endowed with ATRA-sensitivity are characterized by genetic aberrations of the NOTCH1-gene, causing constitutive activation of the NOTCH1 γ-secretase product, N1ICD. N1ICD renders HCC-1599, MB-157 and MDA-MB-157 cells sensitive not only to ATRA, but also to γ-secretase inhibitors (DAPT; PF-03084014). Combinations of ATRA and γ-secretase inhibitors produce additive/synergistic effects in vitro and in vivo. RNA-sequencing studies of HCC-1599 and MB-157 cells exposed to ATRA and DAPT and ATRA+DAPT demonstrate that the two compounds act on common gene sets, some of which belong to the NOTCH1 pathway. ATRA inhibits the growth of HCC-1599, MB-157 and MDA-MB-157 cells via RARα, which up-regulates several retinoid target-genes, including RARβ. RARβ is a key determinant of ATRA anti-proliferative activity, as its silencing suppresses the effects exerted by the retinoid. In conclusion, we demonstrate that ATRA exerts a significant anti-tumor action only in TNBC cells showing constitutive NOTCH1 activation. Our results support the design of clinical trials involving combinations between ATRA and γ-secretase inhibitors for the treatment of this TNBC subtype.

Distinct roles for Notch1 and Notch3 in human adipose-derived stem/stromal cell adipogenesis

The role of the Notch signaling pathway in adipogenesis has long been controversial as the action of individual Notch receptors appears to vary with experimental conditions. In this study, we offer some explanation for the observed contradictions by comparing the role of both Notch1 and Notch3 in regulating the expression of key adipogenic regulator, PPARγ, in human adipose-derived stem/stromal cells (hADSCs) during in vitro adipogenesis. Utilizing qRT-PCR, western blot, and immunofluorescence staining, we demonstrated that Notch3 was expressed prior to the formation of lipid vesicles, while Notch1 only appeared after vesicle formation. In addition, following the induction of adipogenesis, the levels of Notch1 intracellular domain in the nucleus were significantly reduced, while the siRNA-mediated loss of Notch1 reduced transcript but not protein levels of PPARγ. The knockdown of Notch3 led to increased expression of PPARγ during early adipogenesis that was not paralleled by a decreased expression of Hes1 and Hey1, but was accompanied by a marked decrease in the protein level of β-catenin, the key functional component of the canonical Wnt/β-catenin signaling pathway. This study deepens the understanding of the Notch pathway by clarifying the distinct roles of Notch1 and Notch3 during adipogenesis. We showed that Notch3 is involved in early adipogenic differentiation, while Notch1 functions later in the process. In addition, we begin to uncover the interaction between the Notch and Wnt signaling pathways that may offer novel therapeutic targets aimed at obesity and diabetes.

Impact of molecular subtypes on metastatic behavior and overall survival in patients with metastatic breast cancer: A single-center study combined with a large cohort study based on the Surveillance, Epidemiology and End Results database

Breast cancer is a highly heterogeneous disease at the molecular level and >90% of mortalities are due to metastasis and its associated complications. The present study determined the impact of molecular subtypes on metastatic behavior and overall survival (OS) of patients with metastatic breast cancer. The influence of molecular subtypes on the sites and number of metastases in 166 patients with metastatic breast cancer from a single center were assessed; and the influence of molecular subtypes on the sites and number of metastases and OS in 15,322 metastatic cases among 329,770 patients with primary breast cancer from the Surveillance, Epidemiology and End Results database were assessed. Analysis of both datasets revealed that different molecular subtypes exhibited differences in the prevalence of different metastatic sites and number of metastases. A larger proportion of bone metastasis was observed in the hormone receptor (HR)+/human epidermal growth factor receptor 2 (HER2)+ subtype than in other subtypes, more lung metastasis was observed in the HR-/HER2+ subtype and more liver metastasis occurred in the HR+/HER2+ and HR-/HER2+ subtypes. Single-site metastasis was more common for the HR+/HER2- subtype than in other subtypes, while 2-3 sites of metastases were more common for the HR+/HER2+ subtype and ≥4 sites of metastases were more frequent in the HR-/HER2+ and HR-/HER2- subtypes. The mean OS of patients with primary breast cancer in the HR+/HER2- subtype group was the longest (78.5 months), while the HR-/HER2- group had the shortest mean OS (69.1 months). The mean OS of the metastatic HR+/HER2+ group was the longest (46.0 months), while the mean OS of the metastatic HR-/HER2- group was the shortest (18.5 months). In conclusion, the results of the present study suggested that different molecular subtypes of breast cancer have different metastatic behavior, as well as mean OS.

DNA methyltransferase mediates the hypermethylation of the microRNA 34a promoter and enhances the resistance of patient-derived pancreatic cancer cells to molecular targeting agents

DNA methyltransferase (DNMT) participates in the transformation or progression of human cancers by mediating the hypermethylation of cancer suppressors. However, the regulatory role of DNMT in pancreatic cancer cells remains poorly understood. In the present study, we demonstrated that DNMT1 repressed the expression of microRNA 34a (miR-34a) and enhanced the activation of the Notch pathway by mediating the hypermethylation of the miR-34a promoter. In patients with pancreatic cancer, the expression levels of DNMT1 were negatively related with those of miR-34a. Mechanistically, knockdown of DNMT1 decreased the methylation of the miR-34a promoter and enhanced the expression of miR-34a to inhibit the activation of the Notch pathway. Downregulation of the Notch pathway via the DNMT1/miR-34a axis significantly enhanced the sensitivity of pancreatic cells to molecular targeting agents. Therefore, the results of our study suggest that downregulation of DNMT enhances the expression of miR-34a and may be a potential therapeutic target for pancreatic cancer.

Age, sex, and specific gene mutations affect the effects of immune checkpoint inhibitors in colorectal cancer

The effect of age and sex on the predictive value of colorectal cancer (CRC) patients treated with immune checkpoint inhibitors (ICIs) has been controversial, and the effect of specific gene mutations on the predictive value of CRC patients treated with ICIs remains to be explored. Our study analyzed the influence of the above factors on the overall survival (OS) of CRC patients receiving ICIs and explored the influencing mechanism of various predictive biomakers. We performed survival prognostic correlation analysis and bioinformatics analysis on the clinical CRC cohort receiving ICIs in from the Memorial Sloan Kettering Cancer Center (MSKCC) and the clinical and genetic data from The Cancer Genome Atlas (TCGA)-CRC dataset, including immunogenicity analysis, tumor immune microenvironment analysis, and gene set enrichment analysis and so on. We found that mutation count >11 mutation/Mb (tumor mutation burden, TMB-high) (HR = 0.22, 95 %CI: 0.09-0.53; P < 0.001), male (HR = 0.51, 95 %CI: 0.28-0.93; P = 0.029), RNF43-mutant (MT) (HR = 0.12, 95 %CI: 0.03-0.49; P = 0.003), CREBBP-MT (HR = 0.23, 95 %CI: 0.07-0.76; P = 0.016), NOTCH3-MT (HR = 0.17, 95 %CI: 0.04-0.74; P = 0018), PTCH1-MT (HR = 0.27, 95 %CI: 0.08-0.9; P = 0.033), CIC-MT (HR = 0.23, 95 %CI: 0.05-0.93; P = 0.040), DNMT1-MT (HR = 0.12, 95 %CI: 0.02-0.93; P = 0.043) and SPEN-MT (HR = 0.31, 95 %CI: 0.09-0.99; P < 0.049) are all related to longer OS, but age≤65 years (HR = 3.01, 95 %CI: 1.18-7.65; P = 0.021), APC-MT (HR = 2.51, 95 %CI: 1.12-5.63; P = 0.026) and TP53-MT (HR = 1.94, 95 %CI: 1.03-3.65; P = 0.041) are associated with shorter OS. The reason why positive predictive markers provide survival benefits to CRC may be related to higher immunogenicity such as TMB, highly expression of mRNA related to immune response, highly infiltrating immune-active cells such as CD8 + T cells, active immune-active pathways, and DNA damage repair pathways with an increased number of mutations.