The many facets of Notch signaling in breast cancer: toward overcoming therapeutic resistance

DLL4-targeted CAR-T therapy sensitizes neoadjuvant chemotherapy via eliminating cancer stem cells and reshaping immune microenvironment in HER2+ breast cancer

BACKGROUND

Neoadjuvant therapy with trastuzumab, pertuzumab and paclitaxel (THP) has significantly improved the prognosis of patients with human epidermal growth factor receptor 2 (HER2)+ breast cancer (BC). However, there remains a subset of non-responsive patients. Thus, this study sought to identify key regulators of THP neoadjuvant therapy resistance and potential targets to sensitize sensitivity.

METHODS

The Cancer Genome Atlas database, Gene Expression Omnibus and membrane protein database were used to identify the key regulator of THP neoadjuvant resistance. The biological functions and mechanisms of delta-like 4 proteins (DLL4) in THP therapy resistance were investigated in vitro and in vivo using the bioinformatic analysis, multiplex immunofluorescence, flow cytometry, sphere formation assays and chromatin immunoprecipitation, etc. Furthermore, DLL4-targeted chimeric antigen receptor (CAR)-T cells were established to sensitize THP therapy.

RESULTS

DLL4 was identified as a key target in THP neoadjuvant therapy resistance for HER2+ BC. Mechanistically, DLL4+ tumor cells exhibited enhanced stemness and resistance to the THP neoadjuvant chemotherapy. Additionally, soluble DLL4 can split away from tumor cells and diffuse into the stroma, where it can activate the Notch signaling pathway in neutrophils, inducing the formation and release of neutrophil extracellular traps (NETs) by regulating the transcription of MPO, PDIA4 and ELANE. This led to the exclusion of lymphocyte infiltration, thereby enhancing therapy resistance. What is more, we designed a DLL4-targeted CAR-T to eliminate DLL4+ tumor cells and reverse the resistant status.

CONCLUSIONS

Our study revealed novel functions of DLL4 in cell stemness and immune infiltration, including NET formation and T cell exclusion, which collectively contributed to THP neoadjuvant therapy resistance in HER2+ BC. Furthermore, we provided a CAR-T-based therapy to sensitize the THP neoadjuvant therapy.

Breast cancer genomic analyses reveal genes, mutations, and signaling networks

Breast cancer (BC) is the most commonly diagnosed cancer and the predominant cause of death in women. BC is a complex disorder, and the exploration of several types of BC omic data, highlighting genes, perturbations, signaling and cellular mechanisms, is needed. We collected mutational data from 9,555 BC samples using cBioPortal. We classified 1174 BC genes (mutated ≥ 40 samples) into five tiers (BCtier_I-V) and subjected them to pathway and protein‒protein network analyses using EnrichR and STRING 11, respectively. BCtier_I possesses 12 BC genes with mutational frequencies > 5%, with only 5 genes possessing > 10% frequencies, namely, PIK3CA (35.7%), TP53 (34.3%), GATA3 (11.5%), CDH1 (11.4%) and MUC16 (11%), and the next seven BC genes are KMT2C (8.8%), TTN (8%), MAP3K1 (8%), SYNE1 (7.2%), AHNAK2 (7%), USH2A (5.5%), and RYR2 (5.4%). Our pathway analyses revealed that the five top BC pathways were the PI3K-AKT, TP53, NOTCH, HIPPO, and RAS pathways. We found that BC panels share only seven genes. These findings show that BC arises from genetic disruptions evident in BC signaling and protein networks.

Inhibition of γ-secretase/Notch pathway as a potential therapy for reversing cancer drug resistance

The mechanism of tumor drug resistance is complex and may involve stem cell maintenance, epithelial-mesenchymal transition, the activation of survival signaling pathways, transporter protein expression, and tumor microenvironment remodeling, all of which are linked to γ-secretase/Notch signaling. Increasing evidence has shown that the activation of the γ-secretase/Notch pathway is a key driver of cancer progression and drug resistance development and that γ-secretase inhibitors (GSIs) may be the most promising agents for reversing chemotherapy resistance of tumors by targeting the γ-secretase/Notch pathway. Here, we systematically summarize the roles in supporting γ-secretase/Notch activation-associated transformation of cancer cells into cancer stem cells, promotion of the EMT process, PI3K/Akt, MEK/ERK and NF-κB activation, enhancement of ABC transporter protein expression, and TME alteration in mediating tumor drug resistance. Subsequently, we analyze the mechanism of GSIs targeting the γ-secretase/Notch pathway to reverse tumor drug resistance and propose the outstanding advantages of GSIs in treating breast cancer drug resistance over other tumors. Finally, we emphasize that the development of GSIs for reversing tumor drug resistance is promising.

The mir-199b-5p encapsulated in adipocyte-derived exosomes mediates radioresistance of colorectal cancer cells by targeting JAG1

Radiotherapy is a key treatment option for colorectal cancer, but its efficacy varies among patients. Our previous studies suggested that adipose tissue may confer the radioresistance of several abdominal tumors, such as pancreatic cancer, biliary cancer, and others. In the present work, the effects of adipocytes in regulating the radiosensitivity of colorectal cancer are explored for the first time. It was found that colony formation was increased and radiation-induced apoptosis decreased in colorectal cancer cells HCT8 and HCT116 co-cultured with adipocytes, which verified the mediation of adipocyte-driven radioresistance in colorectal cancer in vitro. Next, the colorectal cancer cells were incubated with adipocyte-derived exosomes, and a perceptible reduction in radiosensitivity was detected. Furthermore, to investigate the possible mechanisms involved, the exosomes were isolated, the encapsulated microRNAs were extracted and analyzed by small RNA sequencing. Based on bioinformatics analysis and qRT-PCR verification, miR-199b-5p was chosen for functional annotation. It was shown that miR-199b-5p expression was significantly upregulated after 6 Gy irradiation, and overexpressed miR-199b-5p significantly suppressed the radiosensitivity of HCT8 and HCT116 cells. In addition, jagged canonical Notch ligand 1(JAG1) was identified as the target gene of miR-199b-5p by using bioinformatics prediction and dual luciferase reporter gene assay. It was demonstrated that JAG1 conferred the radioresistance of colorectal cancer cells both in vivo and in vitro. Taken together, the present study demonstrates that adipocytes trigger the radioresistance of colorectal cancer cells, probably by targeting JAG1 through an adipocyte-derived exosomal miR-199b-5p.

Onco-Breastomics: An Eco-Evo-Devo Holistic Approach

Known as a diverse collection of neoplastic diseases, breast cancer (BC) can be hyperbolically characterized as a dynamic pseudo-organ, a living organism able to build a complex, open, hierarchically organized, self-sustainable, and self-renewable tumor system, a population, a species, a local community, a biocenosis, or an evolving dynamical ecosystem (i.e., immune or metabolic ecosystem) that emphasizes both developmental continuity and spatio-temporal change. Moreover, a cancer cell community, also known as an oncobiota, has been described as non-sexually reproducing species, as well as a migratory or invasive species that expresses intelligent behavior, or an endangered or parasite species that fights to survive, to optimize its features inside the host's ecosystem, or that is able to exploit or to disrupt its host circadian cycle for improving the own proliferation and spreading. BC tumorigenesis has also been compared with the early embryo and placenta development that may suggest new strategies for research and therapy. Furthermore, BC has also been characterized as an environmental disease or as an ecological disorder. Many mechanisms of cancer progression have been explained by principles of ecology, developmental biology, and evolutionary paradigms. Many authors have discussed ecological, developmental, and evolutionary strategies for more successful anti-cancer therapies, or for understanding the ecological, developmental, and evolutionary bases of BC exploitable vulnerabilities. Herein, we used the integrated framework of three well known ecological theories: the Bronfenbrenner's theory of human development, the Vannote's River Continuum Concept (RCC), and the Ecological Evolutionary Developmental Biology (Eco-Evo-Devo) theory, to explain and understand several eco-evo-devo-based principles that govern BC progression. Multi-omics fields, taken together as onco-breastomics, offer better opportunities to integrate, analyze, and interpret large amounts of complex heterogeneous data, such as various and big-omics data obtained by multiple investigative modalities, for understanding the eco-evo-devo-based principles that drive BC progression and treatment. These integrative eco-evo-devo theories can help clinicians better diagnose and treat BC, for example, by using non-invasive biomarkers in liquid-biopsies that have emerged from integrated omics-based data that accurately reflect the biomolecular landscape of the primary tumor in order to avoid mutilating preventive surgery, like bilateral mastectomy. From the perspective of preventive, personalized, and participatory medicine, these hypotheses may help patients to think about this disease as a process governed by natural rules, to understand the possible causes of the disease, and to gain control on their own health.

Sulindac sulfide as a non-immune suppressive γ-secretase modulator to target triple-negative breast cancer

Introduction

Triple-negative breast cancer (TNBC) comprises a heterogeneous group of clinically aggressive tumors with high risk of recurrence and metastasis. Current pharmacological treatment options remain largely limited to chemotherapy. Despite promising results, the efficacy of immunotherapy and chemo-immunotherapy in TNBC remains limited. There is strong evidence supporting the involvement of Notch signaling in TNBC progression. Expression of Notch1 and its ligand Jagged1 correlate with poor prognosis. Notch inhibitors, including g-secretase inhibitors (GSIs), are quite effective in preclinical models of TNBC. However, the success of GSIs in clinical trials has been limited by their intestinal toxicity and potential for adverse immunological effects, since Notch plays key roles in T-cell activation, including CD8 T-cells in tumors. Our overarching goal is to replace GSIs with agents that lack their systemic toxicity and ideally, do not affect tumor immunity. We identified sulindac sulfide (SS), the active metabolite of FDA-approved NSAID sulindac, as a potential candidate to replace GSIs.

Methods

We investigated the pharmacological and immunotherapeutic properties of SS in TNBC models in vitro, ex-vivo and in vivo.

Results

We confirmed that SS, a known γ-secretase modulator (GSM), inhibits Notch1 cleavage in TNBC cells. SS significantly inhibited mammosphere growth in all human and murine TNBC models tested. In a transplantable mouse TNBC tumor model (C0321), SS had remarkable single-agent anti-tumor activity and eliminated Notch1 protein expression in tumors. Importantly, SS did not inhibit Notch cleavage in T- cells, and the anti-tumor effects of SS were significantly enhanced when combined with a-PD1 immunotherapy in our TNBC organoids and in vivo.

Discussion

Our data support further investigation of SS for the treatment of TNBC, in conjunction with chemo- or -chemo-immunotherapy. Repurposing an FDA-approved, safe agent for the treatment of TNBC may be a cost-effective, rapidly deployable therapeutic option for a patient population in need of more effective therapies.

Modulation of Notch Signaling by Small-Molecular Compounds and Its Potential in Anticancer Studies

Notch signaling is responsible for conveying messages between cells through direct contact, playing a pivotal role in tissue development and homeostasis. The modulation of Notch-related processes, such as cell growth, differentiation, viability, and cell fate, offer opportunities to better understand and prevent disease progression, including cancer. Currently, research efforts are mainly focused on attempts to inhibit Notch signaling in tumors with strong oncogenic, gain-of-function (GoF) or hyperactivation of Notch signaling. The goal is to reduce the growth and proliferation of cancer cells, interfere with neo-angiogenesis, increase chemosensitivity, potentially target cancer stem cells, tumor dormancy, and invasion, and induce apoptosis. Attempts to pharmacologically enhance or restore disturbed Notch signaling for anticancer therapies are less frequent. However, in some cancer types, such as squamous cell carcinomas, preferentially, loss-of-function (LoF) mutations have been confirmed, and restoring but not blocking Notch functions may be beneficial for therapy. The modulation of Notch signaling can be performed at several key levels related to NOTCH receptor expression, translation, posttranslational (proteolytic) processing, glycosylation, transport, and activation. This further includes blocking the interaction with Notch-related nuclear DNA transcription. Examples of small-molecular chemical compounds, that modulate individual elements of Notch signaling at the mentioned levels, have been described in the recent literature.

Review deciphering potent therapeutic approaches targeting Notch signaling pathway in breast cancer

In the current period of drug development, natural products have provided an unrivaled supply of anticancer medications. By modifying the cancer microenvironment and various signaling pathways, natural products and their derivatives and analogs play a significant role in cancer treatment. These substances are effective against several signaling pathways, particularly the cell death pathways (apoptosis and autophagy) and embryonic developmental pathways (Notch, Wnt, and Hedgehog pathways). Natural products have a long history, but more research is needed to understand their current function in the research and development of cancer treatments and the potential for natural products to serve as a significant source of therapeutic agents in the future. Several target-specific anticancer medications failed to treat cancer, necessitating research into natural compounds with multiple target properties. To help develop a better treatment plan for managing breast cancer, this review has outlined the anticancerous potential of several therapeutic approaches targeting the notch signaling system in breast tumors.

Expressions and Prognostic Values of Notch3 and DLL4 in Human Breast Cancer

Background: Notch signaling played a critical role in promoting breast tumorigenesis and progression. However, the role and prognostic value of Notch3 combined with DLL4 expression in breast carcinoma had not been explored. Methods: The retrospective study enrolled 90 breast cancer tissues and 60 noncancerous tissues from (conceal). The expression and prognostic value of Notch3 and DLL4 in patients with breast carcinoma were investigated using Oncomine and UALCAN database. Notch3 and DLL4 expression levels were detected by quantitative real-time polymerase chain reaction, western blotting, and immunohistochemistry. We analyzed the correlation between both proteins expression and clinicopathological parameters and survival data, respectively. Results: The expressions of Notch3 and DLL4 were increased, and Notch3 expression was significantly positively associated with DLL4 in breast carcinoma. The 2 proteins dramatically correlated with advanced stage, high grade and negative Her2 status. The overexpressing of single or both Notch3 and DLL4 resulted in shortened survival of breast cancer patients. And Notch3 overexpression was one of independent risk predictors to poor prognosis. Conclusion: The interaction of Notch3 receptor and DLL4 ligand accelerates oncogenesis, progression, and poor prognosis of breast cancer patients. Notch3 protein may serve as one of biomarker to independently predict prognosis of patients.

Clinical significance of Notch receptors in triple negative breast cancer

BACKGROUND

The Notch signaling pathway is an evolutionary conserved cell signaling pathway that plays an indispensable role in essential developmental processes. Aberrant activation of Notch pathway is known to initiate wide array of diseases and cancers.

OBJECTIVE

To evaluate the clinical significance of Notch receptors in Triple Negative Breast Cancer.

METHODS

We evaluated the association between Notch receptors and clinicopathological parameters including disease-free survival and overall survival of one hundred TNBC patients by immunohistochemistry.

RESULTS

Positive expression of nuclear Notch1 receptor (18%) was found be significantly correlated with positive lymph node (p = 0.009), high BR score (p = 0.02) and necrosis (p = 0.004) while cytoplasmic expression of Notch2 receptor (26%) was significantly correlated with metastasis (p = 0.05), worse DFS (p = 0.05) and poor OS (p = 0.02) in TNBC patients. Membrane (18%) and cytonuclear (3%) Notch3 expression were significantly associated with poorly differentiated tumors (p = 0.007), high BR score (p = 0.002) and necrosis (p = 0.03) respectively. However, cytoplasmic Notch3 and Notch4 expression were negatively correlated with poor prognostic factors.

CONCLUSIONS

Our data indicated that Notch receptors play a key role in promoting TNBC and mainly, Notch2 may contribute to poor prognosis of the disease. Hence, it is implicated that Notch2 may serve as a potential biomarker and therapeutic target for TNBC.

Notch signaling pathway: a comprehensive prognostic and gene expression profile analysis in breast cancer

Breast cancer is a complex disease exhibiting a great degree of heterogeneity due to different molecular subtypes. Notch signaling regulates the differentiation of breast epithelial cells during normal development and plays a crucial role in breast cancer progression through the abnormal expression of the Notch up-and down-stream effectors. To date, there are only a few patient-centered clinical studies using datasets characterizing the role of Notch signaling pathway regulators in breast cancer; thus, we investigate the role and functionality of these factors in different subtypes using publicly available databases containing records from large studies. High-throughput genomic data and clinical information extracted from TCGA were analyzed. We performed Kaplan-Meier survival and differential gene expression analyses using the HALLMARK_NOTCH_SIGNALING gene set. To determine if epigenetic regulation of the Notch regulators contributes to their expression, we analyzed methylation levels of these factors using the TCGA HumanMethylation450 Array data. Notch receptors and ligands expression is generally associated with the tumor subtype, grade, and stage. Furthermore, we showed gene expression levels of most Notch factors were associated with DNA methylation rate. Modulating the expression levels of Notch receptors and effectors can be a potential therapeutic approach for breast cancer. As we outline herein, elucidating the novel prognostic and regulatory roles of Notch implicate this pathway as an essential mediator controlling breast cancer progression.

LINC01140 Targeting miR-452-5p/RGS2 Pathway to Attenuate Breast Cancer Tumorigenesis

Background

LINC01140 has been known to be involved in various cancers. However, its underlying molecular mechanism in breast cancer (BC) needs further exploration.

Methods

The LINC01140, miR-452-5p, and RGS2 levels in BC cells and tissues were evaluated by means of RT-qPCR and western blotting. The variations in the biological functions of BC cells were analyzed through CCK-8, transwell, western blotting, and xenograft experiments to observe cell viability, migration, levels of apoptosis-related proteins (Bax and Bcl-2), and tumor growth. The correlations existing among LINC01140, miR-452-5p, and RGS2 were validated through luciferase reporter and RIP assays.

Results

LINC01140 and RGS2 were remarkably downregulated in BC cells and tissues, whereas miR-452-5p was upregulated. LINC01140 overexpression diminished BC cell viability, migration, and tumor growth and facilitated apoptosis. MiR-452-5p upregulation enhanced cell viability and migration and suppressed apoptosis. Nevertheless, the additional upregulation of LINC01140 could reverse the promotive effects of miR-452-5p upregulation. Additionally, RGS2 overexpression inhibited the malignant phenotypes of BC cells, but miR-452-5p upregulation abolished this effect. In terms of mechanisms, LINC01140 acted as a miR-452-5p sponge. Moreover, RGS2 was determined to be miR-452-5p's downstream target gene in BC.

Conclusion

LINC01140 functioned as an antitumor agent in BC by sponging miR-452-5p to release RGS2. This hints that LINC01140 is a promising therapeutic target for BC.

[JAG1 promotes migration, invasion, and adhesion of triple-negative breast cancer cells by promoting angiogenesis]

OBJECTIVE

To investigate the effect of JAG1 on the malignant phenotype of triple-negative breast cancer (TNBC) and its role in angiogenesis in breast cancer microenvironment.

METHODS

The expressions of Notch molecules were detected in human TNBC 231 and 231B cells using RT-qPCR. Five female nude mice were inoculated with 231 cells and another 5 with 231B cells into the mammary fat pads, and 4-6 weeks later, the tumors were collected for immunohistochemical and immunofluorescence tests. 231 cells and 231B cells were treated with recombinant JAG (rJAG) protein and DAPT, respectively, and changes in their malignant phenotypes were assessed using CCK-8 assay, Hoechst 33258 staining, wound healing assay, Transwell chamber assay and endothelial cell adhesion assay. Western blotting was used to detect the changes in the expressions of proteins related with the malignant phenotypes of 231 and 231B cells. The effects of conditioned medium (CM) derived from untreated 231 and 231 B cells, rJAG1-treated 231 cells and DAPT-treated 231B cells on proliferation and tube formation ability of cultured human umbilical vein endothelial cells (HUVECs) were evaluated using CCK-8 assay and tube-forming assay.

RESULTS

The expression of JAG1 was higher in 231B cells than in 231 cells (P < 0.05). Tumor 231B showed higher expression of VEGFA and CD31. Compared with 231-Blank group, the migration, invasion and adhesion of 231 cells in 231-rJAG1 were significantly enhanced (P < 0.05). Protein levels of Twist1 and Snail increased (P < 0.01), anti-apoptotic protein Bcl-2 increased (P < 0.05), while DAPT inhibited the related phenomena and indicators of 231B. The 231-rJAG1-CM increased the cell number and tubule number of HUVEC (P < 0.05).

CONCLUSION

JAG1 may affect the malignant phenotype of TNBC and promote angiogenesis in the tumor microenvironment.

Interaction between BEND5 and RBPJ suppresses breast cancer growth and metastasis via inhibiting Notch signaling

High frequent metastasis is the major cause of breast cancer (BC) mortality among women. However, the molecular mechanisms underlying BC metastasis remain largely unknown. Here, we identified six hub BC metastasis driver genes (BEND5, HSD11B1, NEDD9, SAA2, SH2D2A and TNFSF4) through bioinformatics analysis, among which BEND5 is the most significant gene. Low BEND5 expression predicted advanced stage and shorter overall survival in BC patients. Functional experiments showed that BEND5 could suppress BC growth and metastasis in vitro and in vivo. Mechanistically, BEND5 inhibits Notch signaling via directly interacting with transcription factor RBPJ/CSL. BEN domain of BEND5 interacts with the N-terminal domain (NTD) domain of RBPJ, thus preventing mastermind like transcriptional coactivator (MAML) from forming a transcription activation complex with RBPJ. Our study provides a novel insight into regulatory mechanisms underlying Notch signaling and suggests that BEND5 may become a promising target for BC therapy.

Global research hotspots and trends of the Notch signaling pathway in the field of cancer: a bibliometric study

OBJECTIVES

To analyze the development status, research hotspots, research frontiers and future development trends of the Notch signaling pathway in cancer through bibliometric analysis.

METHODS

Publications related to the Notch signaling pathway in cancer were obtained from the Web of Science Core Collection (WoSCC), and information was extracted from the articles using Microsoft Excel 2020, CiteSpace V and VOSviewer software for visual analysis.

RESULTS

The country and institution with the most publications are the USA and Harvard University, respectively. PLoS One is the most published journal, and Cancer Research is the most cocited journal. The author with the most published articles was L Miele, and the most cocited author was ZW Wang. The top 3 keywords were activation, differentiation and growth. Metastasis, epithelial-mesenchymal transition (EMT), invasion, target and resistance are the current research hotspots and frontiers in this field.

CONCLUSIONS

Research related to the Notch signaling pathway in cancer is currently booming, and the USA has made the greatest contribution to this field. At present, the research hotspots and research frontiers in this field mainly focus on the regulatory role of the Notch signaling pathway in tumor invasion and metastasis, the regulation of the Notch signaling pathway in tumor progression through EMT, and the participation of the Notch signaling pathway in the regulation of chemotherapy or immunotherapy resistance to tumors.

Embryonic Programs in Cancer and Metastasis—Insights From the Mammary Gland

Cancer is characterized as a reversion of a differentiated cell to a primitive cell state that recapitulates, in many aspects, features of embryonic cells. This review explores the current knowledge of developmental mechanisms that are essential for embryonic mouse mammary gland development, with a particular focus on genes and signaling pathway components that are essential for the induction, morphogenesis, and lineage specification of the mammary gland. The roles of these same genes and signaling pathways in mammary gland or breast tumorigenesis and metastasis are then summarized. Strikingly, key embryonic developmental pathways are often reactivated or dysregulated during tumorigenesis and metastasis in processes such as aberrant proliferation, epithelial-to-mesenchymal transition (EMT), and stem cell potency which affects cellular lineage hierarchy. These observations are in line with findings from recent studies using lineage tracing as well as bulk- and single-cell transcriptomics that have uncovered features of embryonic cells in cancer and metastasis through the identification of cell types, cell states and characterisation of their dynamic changes. Given the many overlapping features and similarities of the molecular signatures of normal development and cancer, embryonic molecular signatures could be useful prognostic markers for cancer. In this way, the study of embryonic development will continue to complement the understanding of the mechanisms of cancer and aid in the discovery of novel therapeutic targets and strategies.

Exploring new pathways in endocrine-resistant breast cancer

The most common breast cancer (BC) subtypes are hormone-dependent, being either estrogen receptor-positive (ER⁺), progesterone receptor-positive (PR⁺), or both, and altogether comprise the luminal subtype. The mainstay of treatment for luminal BC is endocrine therapy (ET), which includes several agents that act either directly targeting ER action or suppressing estrogen production. Over the years, ET has proven efficacy in reducing mortality and improving clinical outcomes in metastatic and nonmetastatic BC. However, the development of ET resistance promotes cancer survival and progression and hinders the use of endocrine agents. Several mechanisms implicated in endocrine resistance have now been extensively studied. Based on the current clinical and pre-clinical data, the present article briefly reviews the well-established pathways of ET resistance and continues by focusing on the three most recently uncovered pathways, which may mediate resistance to ET, namely receptor activator of nuclear factor kappa B ligand (RANKL)/receptor activator of nuclear factor kappa B (RANK), nuclear factor kappa B (NFκB), and Notch. It additionally overviews the evidence underlying the approval of combined therapies to overcome ET resistance in BC, while highlighting the relevance of future studies focusing on putative mediators of ET resistance to uncover new therapeutic options for the disease.

Notch Signaling in Breast Tumor Microenvironment as Mediator of Drug Resistance

Notch signaling dysregulation encourages breast cancer progression through different mechanisms such as stem cell maintenance, cell proliferation and migration/invasion. Furthermore, Notch is a crucial driver regulating juxtracrine and paracrine communications between tumor and stroma. The complex interplay between the abnormal Notch pathway orchestrating the activation of other signals and cellular heterogeneity contribute towards remodeling of the tumor microenvironment. These changes, together with tumor evolution and treatment pressure, drive breast cancer drug resistance. Preclinical studies have shown that targeting the Notch pathway can prevent or reverse resistance, reducing or eliminating breast cancer stem cells. In the present review, we will summarize the current scientific evidence that highlights the involvement of Notch activation within the breast tumor microenvironment, angiogenesis, extracellular matrix remodeling, and tumor/stroma/immune system interplay and its involvement in mechanisms of therapy resistance.

Roles of Notch Signaling in the Tumor Microenvironment

The Notch signaling pathway is an architecturally simple signaling mechanism, well known for its role in cell fate regulation during organ development and in tissue homeostasis. In keeping with its importance for normal development, dysregulation of Notch signaling is increasingly associated with different types of tumors, and proteins in the Notch signaling pathway can act as oncogenes or tumor suppressors, depending on the cellular context and tumor type. In addition to a role as a driver of tumor initiation and progression in the tumor cells carrying oncogenic mutations, it is an emerging realization that Notch signaling also plays a role in non-mutated cells in the tumor microenvironment. In this review, we discuss how aberrant Notch signaling can affect three types of cells in the tumor stroma-cancer-associated fibroblasts, immune cells and vascular cells-and how this influences their interactions with the tumor cells. Insights into the roles of Notch in cells of the tumor environment and the impact on tumor-stroma interactions will lead to a deeper understanding of Notch signaling in cancer and inspire new strategies for Notch-based tumor therapy.

Emerging drug targets for triple-negative breast cancer: A guided tour of the preclinical landscape

INTRODUCTION

Triple-negative breast cancer (TNBC) is the most fatal molecular subtype of breast cancer because of its aggressiveness and resistance to chemotherapy. FDA-approved therapies for TNBC are limited to poly(ADP-ribose) polymerase inhibitors, immune checkpoint inhibitors, and trophoblast cell surface antigen 2-targeted antibody-drug conjugate. Therefore, developing a novel effective targeted therapy for TNBC is an urgent unmet need.

AREAS COVERED

In this narrative review, we discuss emerging targets for TNBC treatment discovered in early translational studies. We focus on cancer cell membrane molecules, hyperactive intracellular signaling pathways, and the tumor microenvironment (TME) based on their druggability, therapeutic potency, specificity to TNBC, and application in immunotherapy.

EXPERT OPINION

The significant challenges in the identification and validation of TNBC-associated targets are 1) application of appropriate genetic, molecular, and immunological approaches for modulating the target, 2) establishment of a proper mouse model that accurately represents the human immune TME, 3) TNBC molecular heterogeneity, and 4) failure translation of preclinical findings to clinical practice. To overcome those difficulties, future research needs to apply novel technology, such as single-cell RNA sequencing, thermostable group II intron reverse transcriptase sequencing, and humanized mouse models. Further, combination treatment targeting multiple pathways in both the TNBC tumor and its TME is essential for effective disease control.

LncRNA MNX1-AS1: A novel oncogenic propellant in cancers

To date, recent studies have shown that long non-coding RNAs (lncRNAs) are key players in gene regulation processes involved in cancer pathogenesis. In general, Motor neuron and pancreas homeobox 1-antisense RNA1 (MNX1-AS1) is highly expressed in all cancers as reported so far and exerts oncogenic effects through different mechanisms. In this review, we comprehensively summarize the detailed mechanisms of potential functions of MNX1-AS1 in different cancer types as well as the latest knowledge highlighting the potential of MNX1-AS1 as a therapeutic target for cancer. Aberrant expression of MNX1-AS1 closely correlates with clinicopathological parameters. such as lymphatic metastasis, tumor size, tumor stage, OS and DFS. Thus, MNX1-AS1 can be used as a diagnostic and prognostic biomarker or even a therapeutic prognostic target. This article reviews its function, molecular mechanism and clinical prognosis in various malignancies.

Reducing variability of breast cancer subtype predictors by grounding deep learning models in prior knowledge

Deep learning neural networks have improved performance in many cancer informatics problems, including breast cancer subtype classification. However, many networks experience underspecificationwheremultiplecombinationsofparametersachievesimilarperformance, bothin training and validation. Additionally, certain parameter combinations may perform poorly when the test distribution differs from the training distribution. Embedding prior knowledge from the literature may address this issue by boosting predictive models that provide crucial, in-depth information about a given disease. Breast cancer research provides a wealth of such knowledge, particularly in the form of subtype biomarkers and genetic signatures. In this study, we draw on past research on breast cancer subtype biomarkers, label propagation, and neural graph machines to present a novel methodology for embedding knowledge into machine learning systems. We embed prior knowledge into the loss function in the form of inter-subject distances derived from a well-known published breast cancer signature. Our results show that this methodology reduces predictor variability on state-of-the-art deep learning architectures and increases predictor consistency leading to improved interpretation. We find that pathway enrichment analysis is more consistent after embedding knowledge. This novel method applies to a broad range of existing studies and predictive models. Our method moves the traditional synthesis of predictive models from an arbitrary assignment of weights to genes toward a more biologically meaningful approach of incorporating knowledge.

Development of Dl1.72, a Novel Anti-DLL1 Antibody with Anti-Tumor Efficacy against Estrogen Receptor-Positive Breast Cancer

Simple Summary

Over 70% of breast cancers (BCs) are estrogen receptor-positive (ER⁺). The development of endocrine therapy has considerably improved patient outcomes. However, there is a clinical need for novel effective therapies against ER⁺ BCs, since many of these do not respond to standard therapy, and more than one-third of responders acquire resistance, experience relapse and metastasize. The Notch ligand Delta-like 1 (DLL1) is a key player in ER⁺ BC development and aggressiveness. Contrary to complete Notch pharmacological inhibitors, antibody-targeting of individual Notch components is expected to have superior therapeutic efficacy and be better tolerated. In this study, we developed and characterized a novel specific anti-DLL1 antibody with efficacy in inhibiting BC cell proliferation, mammosphere formation and angiogenesis, as well as anti-tumor and anti-metastatic efficacy in an ER⁺ BC mouse model without side effects. Thus, our data suggest that this anti-DLL1 antibody is a promising candidate for ER⁺ BC treatment.

Abstract

The Notch-signaling ligand DLL1 has emerged as an important player and promising therapeutic target in breast cancer (BC). DLL1-induced Notch activation promotes tumor cell proliferation, survival, migration, angiogenesis and BC stem cell maintenance. In BC, DLL1 overexpression is associated with poor prognosis, particularly in estrogen receptor-positive (ER⁺) subtypes. Directed therapy in early and advanced BC has dramatically changed the natural course of ER⁺ BC; however, relapse is a major clinical issue, and new therapeutic strategies are needed. Here, we report the development and characterization of a novel monoclonal antibody specific to DLL1. Using phage display technology, we selected an anti-DLL1 antibody fragment, which was converted into a full human IgG1 (Dl1.72). The Dl1.72 antibody exhibited DLL1 specificity and affinity in the low nanomolar range and significantly impaired DLL1-Notch signaling and expression of Notch target genes in ER⁺ BC cells. Functionally, in vitro treatment with Dl1.72 reduced MCF-7 cell proliferation, migration, mammosphere formation and endothelial tube formation. In vivo, Dl1.72 significantly inhibited tumor growth, reducing both tumor cell proliferation and liver metastases in a xenograft mouse model, without apparent toxicity. These findings suggest that anti-DLL1 Dl1.72 could be an attractive agent against ER⁺ BC, warranting further preclinical investigation.

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.

Notch signaling in cancer: Complexity and challenges on the path to clinical translation

Notch receptors participate in a conserved pathway in which ligands expressed on neighboring cells trigger a series of proteolytic cleavages that allow the intracellular portion of the receptor to travel to the nucleus and form a short-lived transcription complex that turns on target gene expression. The directness and seeming simplicity of this signaling mechanism belies the complexity of the outcomes of Notch signaling in normal cells, which are highly context and dosage dependent. This complexity is reflected in the diverse roles of Notch in cancers of various types, in which Notch may be oncogenic or tumor suppressive and may have a wide spectrum of effects on tumor cells and stromal elements. This review provides an overview of the roles of Notch in cancer and discusses challenges to clinical translation of Notch targeting agents as well as approaches that may overcome these hurdles.