FZD7 has a critical role in cell proliferation in triple negative breast cancer

Combination of Fish Oil and Selenium Enhances Anticancer Efficacy and Targets Multiple Signaling Pathways in Anti-VEGF Agent Treated-TNBC Tumor-Bearing Mice

Fish oil (FO) and selenium (Se) possess antiangiogenic potential in malignant tumors. This study aimed to determine whether combination of FO and Se enhanced treatment efficacy of low-dose antiangiogenic agent Avastin (bevacizumab) in a dose-dependent manner and targeted multiple signaling pathways in triple-negative breast cancer (TNBC)-bearing mice. Randomized into five groups, mice received treatment with either physiological saline (control), Avastin alone, or Avastin in combination with low, medium, and high doses of FO/Se. The target signaling molecules for anticancer were determined either by measuring protein or mRNA expression. Avastin-treated mice receiving FO/Se showed lower tumor growth and metastasis than did mice treated with Avastin alone. Combination-treated mice exhibited lower expressions in multiple proangiogenic (growth) factors and their membrane receptors, and altered cytoplasmic signaling molecules (PI3K-PTEN-AKT-TSC-mTOR-p70S6K-4EBP1, Ras-Raf-MEK-ERK, c-Src-JAK2-STAT3-TMEPAI-Smad, LKB1-AMPK, and GSK3β/β-catenin). Dose-dependent inhibition of down-stream targets including epithelial-to-mesenchymal transition transcription factors, nuclear cyclin and cyclin-dependent kinases, cancer stem cell markers, heat shock protein (HSP-90), hypoxia-inducible factors (HIF-1α/-2α), matrix metalloprotease (MMP-9), and increased apoptosis were observed. These results suggest that combination treatment with FO and Se increases the therapeutic efficacy of Avastin against TNBC in a dose-dependent manner through multiple signaling pathways in membrane, cytoplasmic, and nucleic targets.

Identification of Hub Genes and Pathways of Triple Negative Breast Cancer by Expression Profiles Analysis

Purpose

Triple negative breast cancer (TNBC) is an intrinsic subtype of breast cancer with a poor prognosis, characterized by a lack of ER and PR expression and the absence of HER2 amplification. The aim of this study is to characterize hub genes (key genes in the molecular interaction network) expression in TNBC, which may serve as prognostic predictors for TNBC treatment.

Methods

Four transcriptome microarray datasets GSE27447, GSE39004, GSE43358 and GSE45827 were obtained from the Gene Expression Omnibus (GEO) database, and R package limma and RobustRankAggreg were employed to identify common differentially expressed genes (DEGs). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were conducted by DAVID and KOBAS database. Thereafter, protein–protein interaction (PPI) network was constructed according to STRING online database. Functional modules and hub genes were screened by MCODE and cytohubba plug-ins, and the Cancer Genome Atlas (TCGA) survival analysis and qRT-PCR were utilized to validate the expression of these hub genes on TNBC.

Results

A total of 134 DEGs were identified by differential expression analysis, consisting of 88 up- and 46 down-regulated genes. GO and KEGG analyses showed that the terms and pathways enriched were mainly associated with cell adhesion, tumorigenesis and cellular immunity. From the PPI network, we identified six hub genes, including CD3D, CD3E, CD3G, FYN, GRAP2 and ITK. Survival analysis and the qRT-PCR results confirmed the robustness of the identified hub genes.

Conclusion

This study provides a new insight into the understanding of the molecular mechanisms associated with TNBC and suggested that the hub genes may serve as prognostic predictors.

Identification of novel prognostic genes of triple-negative breast cancer using meta-analysis and weighted gene co-expressed network analysis

Background

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer with high rates of metastasis and recurrence. Conventional clinical treatments are ineffective for it as it lacks therapeutic biomarkers. Figuring out the biomarkers related to TNBC will be beneficial for its clinical treatment and prognosis.

Methods

Five independent datasets downloaded from the Gene Expression Omnibus database were merged to identify differentially expressed genes between TNBC and non-TNBC samples by using the MetaDE.ES method followed by mapping the differentially expressed genes into a protein-protein interaction network. Meanwhile, the weighted gene co-expressed network analysis (WGCNA) of The Cancer Genome Atlas data was performed to screen the hub genes. The gene functional analyses were conducted by Gene Ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. The correlation between gene expression level and patient overall survival was evaluated by survival analysis.

Results

A total of 11 differentially expressed genes (CDH1, SP1, MYC, FAF2, IFI16, MDM2, AR, DBN1, HSPB1, FLNA, YWHAB) were obtained from the protein-protein interaction network with degree >10. WGCNA revealed 5 hub genes (TPX2, CTPS1, KIF2C, MELK, CDCA8) that were significantly associated with TNBC. Cell cycle, oocyte meiosis, spliceosome were the pathways significantly enriched in these genes according to GO functionally annotated terms and KEGG pathways analysis. The Kaplan-Meier curves showed that the expression levels of HSPB1, IFI16, TPX2 were significantly associated with the survival time of TNBC patients (P<0.05).

Conclusions

A total of 16 genes significantly associated with TNBC were identified by bioinformatic analyses. Among these 16 genes, HSPB1, IFI16, TPX2 might be able to be used as biomarkers of TNBC.

Regulation of Wnt Signaling Pathways at the Plasma Membrane and Their Misregulation in Cancer

Wnt signaling is one of the key signaling pathways that govern numerous physiological activities such as growth, differentiation and migration during development and homeostasis. As pathway misregulation has been extensively linked to pathological processes including malignant tumors, a thorough understanding of pathway regulation is essential for development of effective therapeutic approaches. A prominent feature of cancer cells is that they significantly differ from healthy cells with respect to their plasma membrane composition and lipid organization. Here, we review the key role of membrane composition and lipid order in activation of Wnt signaling pathway by tightly regulating formation and interactions of the Wnt-receptor complex. We also discuss in detail how plasma membrane components, in particular the ligands, (co)receptors and extracellular or membrane-bound modulators, of Wnt pathways are affected in lung, colorectal, liver and breast cancers that have been associated with abnormal activation of Wnt signaling. Wnt-receptor complex components and their modulators are frequently misexpressed in these cancers and this appears to correlate with metastasis and cancer progression. Thus, composition and organization of the plasma membrane can be exploited to develop new anticancer drugs that are targeted in a highly specific manner to the Wnt-receptor complex, rendering a more effective therapeutic outcome possible.

Frizzled-7 Identifies Platinum-Tolerant Ovarian Cancer Cells Susceptible to Ferroptosis

Defining traits of platinum-tolerant cancer cells could expose new treatment vulnerabilities. Here, new markers associated with platinum-tolerant cells and tumors were identified using in vitro and in vivo ovarian cancer models treated repetitively with carboplatin and validated in human specimens. Platinum-tolerant cells and tumors were enriched in ALDH+ cells, formed more spheroids, and expressed increased levels of stemness-related transcription factors compared with parental cells. Additionally, platinum-tolerant cells and tumors exhibited expression of the Wnt receptor Frizzled-7 (FZD7). Knockdown of FZD7 improved sensitivity to platinum, decreased spheroid formation, and delayed tumor initiation. The molecular signature distinguishing FZD7+ from FZD7- cells included epithelial-to-mesenchymal (EMT), stemness, and oxidative phosphorylation-enriched gene sets. Overexpression of FZD7 activated the oncogenic factor Tp63, driving upregulation of glutathione metabolism pathways, including glutathione peroxidase 4 (GPX4), which protected cells from chemotherapy-induced oxidative stress. FZD7+ platinum-tolerant ovarian cancer cells were more sensitive and underwent ferroptosis after treatment with GPX4 inhibitors. FZD7, Tp63, and glutathione metabolism gene sets were strongly correlated in the ovarian cancer Tumor Cancer Genome Atlas (TCGA) database and in residual human ovarian cancer specimens after chemotherapy. These results support the existence of a platinum-tolerant cell population with partial cancer stem cell features, characterized by FZD7 expression and dependent on the FZD7-β-catenin-Tp63-GPX4 pathway for survival. The findings reveal a novel therapeutic vulnerability of platinum-tolerant cancer cells and provide new insight into a potential "persister cancer cell" phenotype. SIGNIFICANCE: Frizzled-7 marks platinum-tolerant cancer cells harboring stemness features and altered glutathione metabolism that depend on GPX4 for survival and are highly susceptible to ferroptosis.

A novel humanized Frizzled-7-targeting antibody enhances antitumor effects of Bevacizumab against triple-negative breast cancer via blocking Wnt/β-catenin signaling pathway

BACKGROUND

Anti-angiogenic therapy has been widely applied to the clinical treatment of malignant tumors. However, the efficacy of such treatments has been called into question, especially in triple-negative breast cancer (TNBC). Bevacizumab, the first anti-angiogenic agent approved by FDA, actually increases invasive and metastatic properties of TNBC cells, resulting from the activation of Wnt/β-catenin signaling in response to hypoxia. As a critical receptor of Wnt/β-catenin signaling, Frizzled-7 (Fzd7) is aberrantly expressed in TNBC, indicating Fzd7 a potential target for developing drugs to be combined with anti-angiogenic agents.

METHODS

Hybridoma technique and antibody humanization technique were utilized to generate a Fzd7-targeting antibody (SHH002-hu1). Biolayer interferometry (BLI) assay and near infrared (NIR) imaging were conducted to detect the affinity and targeting ability of SHH002-hu1. Next, whether SHH002-hu1 could suppress the invasion and migration of TNBC cells induced by Bevacizumab were validated, and the underlying molecular mechanisms were elucidated by luciferase reporter and western blot assays. The nude-mice transplanted TNBC models were established to assess the anti-TNBC activities of SHH002-hu1 when combined with Bevacizumab. Then, the effects on putative TNBC stem-like cells and Wnt/β-catenin signaling were evaluated by immunofluorescence (IF). Further, the tumor-initiating and self-renew capacity of TNBC cells were studied by secondary nude mouse xenograft model and sphere formation assay. In addition, the effects of SHH002-hu1 on the adaptation of TNBC cells to hypoxia were evaluated by the detection of vasculogenic mimicry (VM) and hypoxia-inducible factor-1α (HIF-1α) transcriptional activity.

RESULTS

The novel humanized antibody targeting Fzd7 (SHH002-hu1) exhibited extremely high affinity with Fzd7, and specifically targeted to Fzd7⁺ cells and tumor tissues. SHH002-hu1 repressed invasion, migration and epithelial-mesenchymal cell transformation (EMT) of TNBC cells induced by Bevacizumab through abating Wnt/β-catenin signaling. SHH002-hu1 significantly enhanced the capacity of Bevacizumab to inhibit the growth of TNBC via reducing the subpopulation of putative TNBC stem-like cells, further attenuating Bevacizumab-enhanced tumor-initiating and self-renew capacity of TNBC cells. Moreover, SHH002-hu1 effectively restrained the adaptation of TNBC cells to hypoxia via disrupting Wnt/β-catenin signaling.

CONCLUSION

SHH002-hu1 significantly enhances the anti-TNBC capacity of Bevacizumab, and shows the potential of preventing TNBC recurrence, suggesting SHH002-hu1 a good candidate for the synergistic therapy together with Bevacizumab.

Targeting Oncogenic WNT Signalling with WNT Signalling-Derived Peptides

WNT signalling is known to be a crucial regulator of embryonic development and tissue homeostasis. Aberrant expression of WNT signalling elements or their mutations has been implicated in carcinogenesis and/or the progression of several different cancer types. Investigations of how WNT signalling affects carcinogenesis and cancer progression have revealed that it has essential roles in the regulation of proliferation, apoptosis, and cancer stemness and in angiogenesis and metastasis. Consequently, WNT-targeted therapy has gained much attention and has resulted in the development of several small molecules, the majority of which act as inhibitors of different WNT signalling events. However, although numerous inhibitory WNT signalling drug candidates have been included in clinical trials, no significant breakthroughs have been made. This could possibly be due to problems with inefficient binding to the target, compensatory signalling mechanisms and toxicity towards normal cells. Therapeutic peptides targeting WNT signalling in cancer cells have been developed as an alternative approach, with the hope that they might overcome the limitations reported for small WNT inhibitory molecules. In this chapter, we describe recent developments made in the design and characterization of WNT signalling-derived peptides aiming at their use as alternative cancer therapeutics and/or combined adjuvant therapy to conventional therapies.

Mining Natural Compounds to Target WNT Signaling: Land and Sea Tales

WNT signaling plays paramount roles in organism development, physiology, and disease, representing a highly attractive target for drug development. However, no WNT-modulating drugs have been approved, with several candidates trudging through the early clinical trials. This delay instigates alternative approaches to discover WNT-modulating drugs. Natural products were the source of therapeutics for centuries, but the chemical diversity they offer, especially when looking at different taxonomic groups and habitats, is still to a large extent unexplored. These considerations urge researchers to screen natural compounds for the WNT-modulatory activities. Since several reviews on such endeavors exist, we here have attempted to present these efforts as "Land and sea tales" (citing the book title by Rudyard Kipling) superimposing them onto the traditional pipeline of drug discovery and early development. In doing so, we illustrate each step of the pipeline with case studies stemming from our own research. It will become obvious that several steps of the pipeline need to be modified when applied to natural products rather than to synthetic libraries. Yet the main message of this chapter is that natural compounds represent a powerful source for the WNT signaling modulators and can be developed towards drug candidates against WNT-dependent maladies.

Zooming in on the WNT/CTNNB1 Destruction Complex: Functional Mechanistic Details with Implications for Therapeutic Targeting

WNT/CTNNB1 signaling is crucial for balancing cell proliferation and differentiation in all multicellular animals. CTNNB1 accumulation is the hallmark of WNT/CTNNB1 pathway activation and the key downstream event in both a physiological and an oncogenic context. In the absence of WNT stimulation, the cytoplasmic and nuclear levels of CTNNB1 are kept low because of its sequestration and phosphorylation by the so-called destruction complex, which targets CTNNB1 for proteasomal degradation. In the presence of WNT proteins, or as a result of oncogenic mutations, this process is impaired and CTNNB1 levels become elevated.Here we discuss recent advances in our understanding of destruction complex activity and inactivation, focusing on the individual components and interactions that ultimately control CTNNB1 turnover (in the "WNT off" situation) and stabilization (in the "WNT on" situation). We especially highlight the insights gleaned from recent quantitative, image-based studies, which paint an unprecedentedly detailed picture of the dynamic events that control destruction protein complex composition and function. We argue that these mechanistic details may reveal new opportunities for therapeutic intervention and could result in the destruction complex re-emerging as a target for therapy in cancer.

An In Silico Analysis Identified FZD9 as a Potential Prognostic Biomarker in Triple-Negative Breast Cancer Patients

OBJECTIVE

Breast cancer (BC) is the main cause of cancer-related deaths in women across the world. It can be classified into different subtypes, including triple-negative (TN), which is characterized by the absence of hormone receptors for estrogen and progesterone and the lack of the human epidermal growth factor receptor 2. These tumors have high heterogeneity, acquire therapeutic resistance, and have no established target-driven treatment yet. The identification of differentially expressed genes in TN breast tumors and the in silico validation of their prognostic role in these tumors.

MATERIALS AND METHODS

We employed a microarray dataset and, by using the GEO2R tool, we identified a list of differentially expressed genes. The in silico validation was conducted using several online platforms including the KM Plotter, cBioPortal, bc-GenExMiner, Prognoscan, and Roc Plotter.

RESULTS

We observed that FZD9 was among the top differentially expressed genes in a cohort of patients with different TNBC subtypes. The FZD9 expression was significantly different in TN breast tumors than in non-TN (nTN) breast tumors (p<0.0001), and the basal TN subtype showed the highest levels (p<0.0001). In addition, the FZD9 levels were significantly inversely and positively proportional (p<0.0001) to estrogen receptor, progesterone receptor, and human epidermal growth factor receptor-2 clinical parameters. The high levels of FZD9 were associated with worse overall survival (p=0.007), relapse-free survival (p=5.8e-05), and worse survival in patients who received chemotherapy (p=3.2e-05; 0.007).

CONCLUSION

Our cumulative results demonstrated that FZD9 plays an important role in TNBC and may be a potential prognostic biomarker. Nevertheless, further in vitro and in vivo assays are necessary to confirm our findings and to strengthen the evidences about the mechanisms by which FZD9 functions in these tumors.

LncRNA HOTAIR promotes breast cancer progression through regulating the miR-129-5p/FZD7 axis

Breast cancer is the most common malignancies worldwide. LncRNA HOX transcript antisense intergenic RNA (HOTAIR) has been shown to promote progression and metastasis of various cancers, including breast cancer. This reasearch aimed to investigate the downstream regulatory pathways of HOTAIR in breast cancer. The levels of HOTAIR and miR-129-5p were examined in breast cancer tissues and SKBR3 and MCF7 cells by quantitative real-time PCR (qRT-PCR). Cell proliferation was examined by Cell Counting Kit-8 (CCK-8) assay. Cell migration and invasion were estimated by transwell assay. Epithelial-to-mesenchymal transition (EMT)-related markers (E-cadherin, N-cadherin and Vimentin) were measured by Western blot assay. The expression of Frizzled 7 (FZD7) was detected using qRT-PCR or Western blot assay. Bioinformatics analysis, luciferase reporter assay or RNA Immunoprecipitation (RIP) assay was performed to explore the molecular mechanism of HOTAIR in breast cancer. Xenograft analysis was utilized to evaluate the tumor growth in vivo. HOTAIR and FZD7 were upregulated, while miR-129-5p was down-regulated in breast cancer tissues and cells. Knockdown of miR-129-5p reversed the effect of HOTAIR knockdown on cell proliferation, migration, invasion and EMT. FZD7 restored the inhibition of miR-129-5p on breast cancer progression. Furthermore, HOTAIR was a sponge of miR-129-5p and FZD7 was a target of miR-129-5p. Knockdown of HOTAIR inhibited the tumor growth in vivo. HOTAIR facilitated breast cancer progression by regulating the miR-129-5p/FZD7 axis, indicating that HOTAIR may be a potential biomarker and therapeutic target for breast cancer.

Activation barriers in Class F G protein-coupled receptors revealed by umbrella sampling simulations

The Class F G protein-coupled receptors (GPCRs) include Smoothened and the ten Frizzled receptors, which are major cell membrane receptors in the Hedgehog and Wnt signalling pathways respectively and of enormous interest in embryonic development and as therapeutic targets in cancer. Recent crystal structures of Smoothened provide the opportunity to investigate the structural biology of Class F GPCRs in more detail, in turn, informing the development of therapeutics. A key question in this area is how one receptor may trigger distinct pathways - particularly relevant for Wnt signalling, in which signals may be transduced from a Frizzled via Dishevelled or G proteins, depending on the context. In this study, we employ adiabatic biased molecular dynamics and umbrella sampling to investigate the activation of Smoothened and Frizzled-7 in both the native state and bound to endogenous ligands, as well as how the clinically used Smoothened antagonist vismodegib alters this signalling. The results highlight key energetic barriers in the activation of these receptors, and the molecular features of the receptors mediating these barriers, demonstrating our approach as a robust means of investigating signalling through these receptors.

FZD5 contributes to TNBC proliferation, DNA damage repair and stemness

Chemotherapy currently remains the standard treatment for triple-negative breast cancer (TNBC). However, TNBC frequently develop chemoresistance, which is responsible for cancer recurrence and distal metastasis. Both DNA damage repair and stemness are related to chemoresistance. FZD5, a member in Frizzled family, was identified to be preferentially expressed in TNBC, and associated with unfavorable prognosis. Loss and gain of function studies revealed that FZD5 contributed to TNBC cell G1/S transition, DNA replication, DNA damage repair, survival, and stemness. Mechanistically, transcription factor FOXM1, which promoted BRCA1 and BIRC5 transcription, acted as a downstream effecter of FZD5 signaling. FOXM1 overexpression in FZD5-deficient/low TNBC cells induced FZD5-associated phenotype. Finally, Wnt7B, a specific ligand for FZD5, was shown to be involved in cell proliferation, DNA damage repair, and stemness. Taken together, FZD5 is a novel target for the development of therapeutic strategies to overcome chemoresistance and prevent recurrence in TNBC.

Wnt signaling in breast cancer: biological mechanisms, challenges and opportunities

Wnt signaling is a highly conserved signaling pathway that plays a critical role in controlling embryonic and organ development, as well as cancer progression. Genome-wide sequencing and gene expression profile analyses have demonstrated that Wnt signaling is involved mainly in the processes of breast cancer proliferation and metastasis. The most recent studies have indicated that Wnt signaling is also crucial in breast cancer immune microenvironment regulation, stemness maintenance, therapeutic resistance, phenotype shaping, etc. Wnt/β-Catenin, Wnt-planar cell polarity (PCP), and Wnt-Ca2+ signaling are three well-established Wnt signaling pathways that share overlapping components and play different roles in breast cancer progression. In this review, we summarize the main findings concerning the relationship between Wnt signaling and breast cancer and provide an overview of existing mechanisms, challenges, and potential opportunities for advancing the therapy and diagnosis of breast cancer.

Wnt and Vitamin D at the Crossroads in Solid Cancer

Simple Summary

The Wnt/β-catenin signaling pathway is aberrantly activated in most colorectal cancers and less frequently in a variety of other solid neoplasias. Many epidemiological and experimental studies and some clinical trials suggest an anticancer action of vitamin D, mainly against colorectal cancer. The aim of this review was to analyze the literature supporting the interference of Wnt/β-catenin signaling by the active vitamin D metabolite 1α,25-dihydroxyvitamin D₃. We discuss the molecular mechanisms of this antagonism in colorectal cancer and other cancer types. Additionally, we summarize the available data indicating a reciprocal inhibition of vitamin D action by the activated Wnt/β-catenin pathway. Thus, a complex mutual antagonism between Wnt/β-catenin signaling and the vitamin D system seems to be at the root of many solid cancers.

Abstract

Abnormal activation of the Wnt/β-catenin pathway is common in many types of solid cancers. Likewise, a large proportion of cancer patients have vitamin D deficiency. In line with these observations, Wnt/β-catenin signaling and 1α,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃), the active vitamin D metabolite, usually have opposite effects on cancer cell proliferation and phenotype. In recent years, an increasing number of studies performed in a variety of cancer types have revealed a complex crosstalk between Wnt/β-catenin signaling and 1,25(OH)₂D₃. Here we review the mechanisms by which 1,25(OH)₂D₃ inhibits Wnt/β-catenin signaling and, conversely, how the activated Wnt/β-catenin pathway may abrogate vitamin D action. The available data suggest that interaction between Wnt/β-catenin signaling and the vitamin D system is at the crossroads in solid cancers and may have therapeutic applications.

Drug Repurposing for Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is the most aggressive type of breast cancer which presents a high rate of relapse, metastasis, and mortality. Nowadays, the absence of approved specific targeted therapies to eradicate TNBC remains one of the main challenges in clinical practice. Drug discovery is a long and costly process that can be dramatically improved by drug repurposing, which identifies new uses for existing drugs, both approved and investigational. Drug repositioning benefits from improvements in computational methods related to chemoinformatics, genomics, and systems biology. To the best of our knowledge, we propose a novel and inclusive classification of those approaches whereby drug repurposing can be achieved in silico: structure-based, transcriptional signatures-based, biological networks-based, and data-mining-based drug repositioning. This review specially emphasizes the most relevant research, both at preclinical and clinical settings, aimed at repurposing pre-existing drugs to treat TNBC on the basis of molecular mechanisms and signaling pathways such as androgen receptor, adrenergic receptor, STAT3, nitric oxide synthase, or AXL. Finally, because of the ability and relevance of cancer stem cells (CSCs) to drive tumor aggressiveness and poor clinical outcome, we also focus on those molecules repurposed to specifically target this cell population to tackle recurrence and metastases associated with the progression of TNBC.

Frizzled Receptors in Tumors, Focusing on Signaling, Roles, Modulation Mechanisms, and Targeted Therapies

Wnt molecules play crucial roles in development and adult homeostasis through their receptors Frizzled proteins (Fzds). Fzds mediate canonical β-catenin pathway and various noncanonical β-catenin-independent pathways. Aberrant Fzd signaling is involved in many diseases including cancer. Wnt/β-catenin is a well-established oncogenic pathway involved in almost every aspect of tumor development. However, Fzd-mediated noncanonical Wnt pathways function as both tumor promoters and tumor suppressors depending on cellular context. Fzd-targeted therapies have proven to be effective on cultured tumor cells, tumor cell xenografts, mouse tumor models, and patient-derived xenografts (PDX). Moreover, Fzd-targeted therapies synergize with chemotherapy in preclinical models. However, the occurrence of fragility fractures in patients treated with Fzd-targeted agents such as OMP-54F28 and OMP-18R5 limits the development of this combination. Along with new insights on signaling, roles, and modulation mechanisms of Fzds in human tumors, more Fzd-related therapeutic targets will be developed.

Non-canonical Fzd7 signaling contributes to breast cancer mesenchymal-like stemness involving Col6a1

Mesenchymal-like stemness is characterized by epithelial-mesenchymal transition (EMT). Breast cancer (BC) cell mesenchymal-like stemness is responsible for distal lung metastasis. Interrogation of databases showed that Fzd7 was closely associated with a panel of mesenchymal-related genes and a panel of stemness-related genes. Fzd7 knockdown in mesenchymal-like MDA-MB-231 and Hs578T cells reduced expression of Vimentin, Slug and Zeb1, induced an epithelial-like morphology, inhibited cell motility, impaired mammosphere formation and decreased Lgr5⁺ subpopulation. In contrast, Fzd7 overexpression in MCF7 cells resulted in opposite changes. Fzd7 knockdown delayed xenograft tumor formation, suppressed tumor growth, and impaired lung metastasis. Mechanistically, Fzd7 combined with Wnt5a/b and modulated expression of phosphorylated Stat3 (p-STAT3), Smad3 and Yes-associated protein 1 (Yap1). Moreover, Fzd7-Wnt5b modulated expression of collagen, type VI, alpha 1 (Col6a1). Both Wnt5b knockdown and Col6a1 knockdown disrupted BC cell mesenchymal phenotype and stemness. Taken together, Fzd7 contributes to BC cell EMT and stemness, inducing tumorigenesis and metastasis, mainly through a non-canonical Wnt5b pathway. Col6a1 is implicated in Fzd7-Wnt5b signaling, and mediates Fzd7-Wnt5b -induced mesenchymal-like stemness.

Downregulation of beta-catenin in chemo-tolerant TNBC through changes in receptor and antagonist profiles of the WNT pathway: Clinical and prognostic implications

PURPOSE

In approximately 30% of triple-negative breast cancer (TNBC) patients a complete pathological response is achieved. However, after neo-adjuvant chemotherapy treatment (NACT) residual tumour cells can be intrinsically resistant to chemotherapy. In this study, associations of the WNT/beta-catenin pathway with chemo-tolerance of NACT treated TNBC patients were compared to that of pre-treatment TNBC patients.

METHODS

Expression analyses were performed in both pre-treatment and NACT treated TNBC samples using immunohistochemistry and qRT-PCR, along with DNA copy number variation (CNV) and promoter methylation analyses to elucidate the mechanism(s) underlying chemo-tolerance. In addition, in vitro validation experiments were performed in TNBC cells followed by in vivo clinicopathological correlation analyses.

RESULTS

A reduced expression (41.1%) of nuclear beta-catenin together with a low proliferation index was observed in NACT samples, whereas a high expression (59.0%) was observed in pre-treatment samples. The reduced nuclear expression of beta-catenin in the NACT samples showed concordance with reduced expression levels (47-52.9%) of its associated receptors (FZD7 and LRP6) and increased expression levels (35.2-41.1%) of its antagonists (SFRP1, SFRP2, DKK1) compared to those in the pre-treatment samples. The expression levels of the receptors showed no concordance with its respective gene copy number/mRNA expression statuses, regardless treatment. Interestingly, however, significant increases in promoter hypomethylation of the antagonists were observed in the NACT samples compared to the pre-treatment samples. Similar expression patterns of the antagonists, receptors and beta-catenin were observed in the TNBC-derived cell line MDA-MB-231 using the anthracyclines doxorubicin and nogalamycin, suggesting the importance of promoter hypomethylation in chemotolerance. NACT patients showing reduced receptor and/or beta-catenin expression levels and high antagonist expression levels exhibited a comparatively better prognosis than the pre-treatment patients.

CONCLUSIONS

Our data suggest that reduced nuclear expression of beta-catenin in NACT TNBC samples, due to downregulation of its receptors and upregulation of its antagonists through promoter hypomethylation of the WNT pathway, plays an important role in chemo-tolerance.

Contribution of the Low-Density Lipoprotein Receptor Family to Breast Cancer Progression

The low-density lipoprotein receptor (LDLR) family comprises 14 single-transmembrane receptors sharing structural homology and common repeats. These receptors specifically recognize and internalize various extracellular ligands either alone or complexed with membrane-spanning co-receptors that are then sorted for lysosomal degradation or cell-surface recovery. As multifunctional endocytic receptors, some LDLR members from the core family were first considered as potential tumor suppressors due to their clearance activity against extracellular matrix-degrading enzymes. LDLRs are also involved in pleiotropic functions including growth factor signaling, matricellular proteins, and cell matrix adhesion turnover and chemoattraction, thereby affecting both tumor cells and their surrounding microenvironment. Therefore, their roles could appear controversial and dependent on the malignancy state. In this review, recent advances highlighting the contribution of LDLR members to breast cancer progression are discussed with focus on (1) specific expression patterns of these receptors in primary cancers or distant metastasis and (2) emerging mechanisms and signaling pathways. In addition, potential diagnosis and therapeutic options are proposed.

Concurrent Wnt pathway component expression in breast and colorectal cancer

Wnt signaling pathway regulates important cell functions such as proliferation and migration and is frequently deregulated in colorectal and breast cancer. Thus, it constitutes an attractive therapeutic target with many drugs being investigated in clinical trials. Eighty-two breast and 102 colorectal carcinomas were analyzed for: relative mRNA expression levels of Wnt pathway components namely Wnt3 ligand, Frizzled 7 receptor and LEF1 transcriptional factor, their concurrent expression patterns and their correlation with clinicopathological features. Regarding breast carcinomas, increased relative mRNA expression levels of WNT3 were found in 54 % of cases whereas decreased relative mRNA expression levels were observed in FZD7 and LEF1 in 82 % and 43 % of cases, respectively. Expression levels of WNT3 were significantly correlated with tumour grade (p = 0.021) in breast cancer. As far as colorectal carcinomas are concerned, increased relative mRNA expression levels of WNT3, FZD7 and LEF1 were found in 60 %, 37 % and 48 % of cases respectively. A statistically significant correlation emerged between LEF1expression levels and pT-category (p = 0.027), suggesting a possible association with tumour aggressiveness in colorectal carcinomas. Statistically significant linear correlations were observed between the expression of WNT3/LEF1 (R = 0.233, p = 0.035) and FZD7/LEF1 (R = 0.359, p = 0.001) in breast carcinomas as well as in colorectal carcinomas (R = 0.536, p < 0.01 and R = 0.210, p = 0.034) respectively. Our results demonstrate a possible clinical significance of Wnt pathway gene expression levels in both tumour types. The distinct expression patterns and simultaneous expression of the investigated genes underscore the complexity of this pathway in breast and colorectal carcinogenesis and highlights the necessity of patient selection with regard to the effectiveness of Wnt pathway inhibitors.

Inhibition of Wnt signaling by Frizzled7 antibody-coated nanoshells sensitizes triple-negative breast cancer cells to the autophagy regulator chloroquine

Despite improvements in our understanding of the biology behind triple-negative breast cancer (TNBC), it remains a devastating disease due to lack of an effective targeted therapy. Inhibiting Wnt signaling is a promising strategy to combat TNBC because Wnt signaling drives TNBC progression, chemoresistance, and stemness. However, Wnt inhibition can lead to upregulation of autophagy, which confers therapeutic resistance. This provides an opportunity for combination therapy, as autophagy inhibitors applied concurrently with Wnt inhibitors could increase treatment efficacy. Here, we applied the autophagy inhibitor chloroquine (CQ) to TNBC cells in combination with Frizzled7 antibody-coated nanoshells (FZD7-NS) that suppress Wnt signaling by blocking Wnt ligand/FZD7 receptor interactions, and evaluated this dual treatment in vitro. We found that FZD7-NS can inhibit Axin2 and CyclinD1, two targets of canonical Wnt signaling, and increase the expression of LC3, an autophagy marker. When FZD7-NS and CQ are applied together, they reduce the expression of several stemness genes in TNBC cells, leading to inhibition of TNBC cell migration and self-renewal. Notably, co-delivery of FZD7-NS and CQ is more effective than either therapy alone or the combination of CQ with free FZD7 antibodies. This demonstrates that the nanocarrier design is important to its therapeutic utility. Overall, these findings indicate that combined regulation of Wnt signaling and autophagy by FZD7-NS and CQ is a promising strategy to combat TNBC.

Emerging role of sirtuins in breast cancer metastasis and multidrug resistance: Implication for novel therapeutic strategies targeting sirtuins

Sirtuins (SIRTs), a class III histone deacetylases (HDACs) that require NAD⁺ as a cofactor and include SIRT1-7 proteins in mammals. Accumulative evidence has established that every sirtuin possesses exclusive and poised biology, implicating their role in the regulation of multifaceted biological functions leading to breast cancer initiation, progression, and metastasis. This article provides an outline of recent developments in the role of sirtuins in breast cancer metastasis and development of multidrug resistance (MDR). In addition, we have also highlighted the impending prospects of targeting SIRTs to overcome MDR to bring advancement in breast cancer management. Further, this review will focus on strategies for improving the activity and efficacy of existing cancer therapeutics by combining (adjuvant treatment/therapy) them with sirtuin inhibitors/modulators. All available as well as newly discovered synthetic and dietary sirtuin inhibitors, activators/modulators have been extensively reviewed and compiled to provide a rationale for targeting sirtuins. Further, we discuss their potential in developing future therapeutics against sirtuins proposing their use along with conventional chemotherapeutics to overcome the problem of breast cancer metastasis and MDR.

Narrowing the focus: Therapeutic cell surface targets for refractory triple-negative breast cancer

Triple-negative breast cancer (TNBC) is defined as a type of breast cancer with lack of expression of estrogen receptor, progesterone receptor and human epidermal growth factor 2 protein. In comparison to other types of breast cancer, TNBC characterizes for its aggressive behavior, more prone to early recurrence and a disease with poor response to molecular target therapy. Although TNBC is identified in only 25%-30% of American breast cancer cases annually, these tumors continue to be a therapeutic challenge for clinicians for several reasons: Tumor heterogeneity, limited and toxic systemic therapy options, and often resistance to current standard therapy, characterized by progressive disease on treatment, residual tumor after cytotoxic chemotherapy, and early recurrence after complete surgical excision. Cell-surface targeted therapies have been successful for breast cancer in general, however there are currently no approved cell-surface targeted therapies specifically indicated for TNBC. Recently, several cell-surface targets have been identified as candidates for treatment of TNBC and associated targeted therapies are in development. The purpose of this work is to review the current clinical challenges posed by TNBC, the therapeutic approaches currently in use, and provide an overview of developing cell surface targeting approaches to improve outcomes for treatment resistant TNBC.

CDDO-Me Elicits Anti-Breast Cancer Activity by Targeting LRP6 and FZD7 Receptor Complex

Aberrant activation of the Wnt/β-catenin pathway leads to the development of multiple cancers, including breast cancer. Development of therapeutic agents against this signaling pathway is an urgent need. In this study, we found that 2-cyano-3, 12-dioxooleana-1, 9(11)-dien-28-oic acid-methyl ester (CDDO-Me) could inhibit Wnt/β-catenin signaling mainly through targeting the low-density lipoprotein receptor-related protein (LRP) 6 and Frizzled (FZD) 7 receptor complex. This compound induced the degradation and ubiquitination of LRP6 and Fzd7 via the lysosomal pathway. We further showed that CDDO-Me mediated the degradation of FZD7 in an LRP6 ectodomain-dependent manner. In breast cancer cells, treatment with CDDO-Me increased the degradation of LRP6 and FZD7 and reduced the levels of phosphorylated Disheveled (DVL) 2 and active β-catenin, resulting in the downregulation of Wnt target genes and several cancer stem cell (CSC) marker genes. In a murine xenograft bearing mouse mammary tumor virus (MMTV)-Wnt1-driven mammary tumor, administration of CDDO-Me significantly inhibited tumor growth and was accompanied by reduced expression of phosphorylated and total LRP6, phosphorylated and unphosphorylated DVL2, active β-catenin, several Wnt target genes, and CSC marker genes. Collectively, the results of our study present that CDDO-Me is a potent Wnt/β-catenin signaling inhibitor that may be a promising therapeutic agent against breast cancer. SIGNIFICANCE STATEMENT: Blocking the membrane receptor complex consisting of low-density lipoprotein receptor-related protein (LRP) 6 and Frizzled (FZD) 7 may help developing therapeutic approaches for cancers, including breast cancers. Our study indicates that 2-cyano-3, 12-dioxooleana-1, 9(11)-dien-28-oic acid-methyl ester (CDDO-Me) can inhibit Wnt/β-catenin signaling by inducing the ubiquitination and degradation of LRP6/FZD7 membrane receptor complex via a lysosomal pathway. We also found that the ectodomain of LRP6 is essential for CDDO-Me-induced FZD7 degradation. Defining CDDO-Me as a novel inhibitor of Wnt/β-catenin signaling, our results provide insight into the mechanism of its anticancer activity.

Role of cell polarity and planar cell polarity (PCP) proteins in spermatogenesis

Studies on cell polarity proteins and planar cell polarity (PCP) proteins date back to almost 40 years ago in Drosophila and C. elegans when these proteins were shown to be crucial to support apico-basal polarity and also directional alignment of polarity cells across the plane of an epithelium during morphogenesis. In adult mammals, cell polarity and PCP are most notable in cochlear hair cells. However, the role of these two groups of proteins to support spermatogenesis was not explored until a decade earlier when several proteins that confer cell polarity and PCP proteins were identified in the rat testis. Since then, there are several reports appearing in the literature to examine the role of both cell polarity and PCP in supporting spermatogenesis. Herein, we provide an overview regarding the role of cell polarity and PCP proteins in the testis, evaluating these findings in light of studies in other mammalian epithelial cells/tissues. Our goal is to provide a timely evaluation of these findings, and provide some thought provoking remarks to guide future studies based on an evolving concept in the field.

Anti-metastatic properties of a potent herbal combination in cell and mice models of triple negative breast cancer

AIM

To determine the anti-metastatic potential of combinations of two bioactive carotenoids of saffron, crocin and crocetin, on 4T1 breast cancer and on a mice model of TNBC, and assess the effect of the most potent combination on the Wnt/β-catenin pathway.

MAIN METHODS

The effects of the carotenoid combinations on the viability of 4T1 cells were determined by MTT assay. The effects of the nontoxic doses on migration, mobility, invasion and adhesion to ECM were examined by scratch assay, Transwell/Matrigel-coated Transwell chamber and adhesion assay respectively. Tumors were inoculated by injecting mice with 4T1 cells. The weights and survival rates of the mice and tumor sizes were monitored. Histological analysis of the tissues was conducted. The expression levels of Wnt/β-catenin pathway genes were measured by Real-time PCR and western blotting.

KEY FINDINGS

Treatment of 4T1 cells with combination doses inhibited viability in a dose-dependent manner. The nontoxic combinations significantly inhibited migration, cell mobility and invasion, also attenuating adhesion to ECM. The combination therapy mice possessed more weight, higher survival rates and smaller tumors. Histological examination detected remarkably fewer metastatic foci in their livers and lungs. It was also demonstrated that the combinations exerted anti-metastatic effects by disturbing the Wnt/β-catenin target genes in the liver and tumors.

SIGNIFICANCE

Our findings propose a carotenoid combination as an alternative potent herbal treatment for TNBC, which lacks the adverse effects associated with either chemotherapeutic agents or herb-chemotherapeutic drugs.

Aberrant WNT/CTNNB1 Signaling as a Therapeutic Target in Human Breast Cancer: Weighing the Evidence

WNT signaling is crucial for tissue morphogenesis during development in all multicellular animals. After birth, WNT/CTNNB1 responsive stem cells are responsible for tissue homeostasis in various organs and hyperactive WNT/CTNNB1 signaling is observed in many different human cancers. The first link between WNT signaling and breast cancer was established almost 40 years ago, when Wnt1 was identified as a proto-oncogene capable of driving mammary tumor formation in mice. Since that discovery, there has been a dedicated search for aberrant WNT signaling in human breast cancer. However, much debate and controversy persist regarding the importance of WNT signaling for the initiation, progression or maintenance of different breast cancer subtypes. As the first drugs designed to block functional WNT signaling have entered clinical trials, many questions about the role of aberrant WNT signaling in human breast cancer remain. Here, we discuss three major research gaps in this area. First, we still lack a basic understanding of the function of WNT signaling in normal human breast development and physiology. Second, the overall extent and precise effect of (epi)genetic changes affecting the WNT pathway in different breast cancer subtypes are still unknown. Which underlying molecular and cell biological mechanisms are disrupted as a result also awaits further scrutiny. Third, we survey the current status of targeted therapeutics that are aimed at interfering with the WNT pathway in breast cancer patients and highlight the importance and complexity of selecting the subset of patients that may benefit from treatment.

Fzd2 Contributes to Breast Cancer Cell Mesenchymal-Like Stemness and Drug Resistance

Cancer cell stemness is responsible for cancer relapse, distal metastasis, and drug resistance. Here we identified that Frizzled 2 (Fzd2), one member of Wnt receptor Frizzled family, induced human breast cancer (BC) cell stemness via noncanonical Wnt pathways. Fzd2 was overexpressed in human BC tissues, and Fzd2 overexpression was associated with an unfavorable outcome. Fzd2 knockdown (KD) disturbed the mesenchymal-like phenotype, migration, and invasion of BC cells. Moreover, Fzd2 KD impaired BC cell mammosphere formation, reduced Lgr5⁺ BC cell subpopulation, and enhanced sensitivity of BC cells to chemical agents. Mechanistically, Fzd2 modulated and bound with Wnt5a/b and Wnt3 to activate several oncogenic pathways such as interleukin-6 (IL-6)/Stat3, Yes-associated protein 1 (Yap1), and transforming growth factor-β1 (TGF-β1)/Smad3. These data indicate that Fzd2 contributes to BC cell mesenchymal-like stemness; targeting Fzd2 may inhibit BC recurrence, metastasis, and chemoresistance.

Expression of LGR5, FZD7, TROY, and MIST1 in Perioperatively Treated Gastric Carcinomas and Correlation with Therapy Response

The cancer stem cell model is considered as a putative cause of resistance to chemotherapy and disease recurrence in malignant tumors. In this study, we tested the hypothesis that the response to neoadjuvant/perioperative chemotherapy correlates with the expression of four different putative cancer stem cell markers of gastric cancer (GC), i.e., LGR5, FZD7, TROY, and MIST1. The expression of LGR5, FZD7, TROY, and MIST1 was assessed by immunohistochemistry in 119 perioperatively treated GCs including pretherapeutic biopsies, resected primary GCs, and corresponding nodal and distant metastases. All four markers were detected in our cohort with variable prevalence and histoanatomical distributions. Few tumor cells expressed TROY. LGR5, FZD7, and MIST1 were coexpressed in 41.2% and completely absent in 6.2%. The prevalence of LGR5- and FZD7-positive GCs was higher and of TROY-positive GCs lower in perioperatively treated GCs compared with treatment-naïve tumors. LGR5, FZD7, and MIST1 in the primary tumors correlated significantly with their expression in the corresponding lymph node metastasis. An increased expression of LGR5 in primary GC correlated significantly with tumor regression. The expression of MIST1 in lymph node metastases correlated significantly with the number of lymph node metastases as well as overall and tumor-specific survival. FZD7 did not correlate with any clinicopathological patient characteristic. Our study on clinical patient samples shows that GCs may coexpress independently different stem cell markers; that neoadjuvant/perioperative treatment of GC significantly impacts on the expression of stem cell markers, which cannot be predicted by the analysis of pretherapeutic biopsies; and that their expression and tumor biological effect are heterogeneous and have to be viewed as a function of histoanatomical distribution.

Multiplatform biomarker identification using a data-driven approach enables single-sample classification

BACKGROUND

High-throughput gene expression profiles have allowed discovery of potential biomarkers enabling early diagnosis, prognosis and developing individualized treatment. However, it remains a challenge to identify a set of reliable and reproducible biomarkers across various gene expression platforms and laboratories for single sample diagnosis and prognosis. We address this need with our Data-Driven Reference (DDR) approach, which employs stably expressed housekeeping genes as references to eliminate platform-specific biases and non-biological variabilities.

RESULTS

Our method identifies biomarkers with "built-in" features, and these features can be interpreted consistently regardless of profiling technology, which enable classification of single-sample independent of platforms. Validation with RNA-seq data of blood platelets shows that DDR achieves the superior performance in classification of six different tumor types as well as molecular target statuses (such as MET or HER2-positive, and mutant KRAS, EGFR or PIK3CA) with smaller sets of biomarkers. We demonstrate on the three microarray datasets that our method is capable of identifying robust biomarkers for subgrouping medulloblastoma samples with data perturbation due to different microarray platforms. In addition to identifying the majority of subgroup-specific biomarkers in CodeSet of nanoString, some potential new biomarkers for subgrouping medulloblastoma were detected by our method.

CONCLUSIONS

In this study, we present a simple, yet powerful data-driven method which contributes significantly to identification of robust cross-platform gene signature for disease classification of single-patient to facilitate precision medicine. In addition, our method provides a new strategy for transcriptome analysis.

In Silico Identification of Potential Inhibitors of the Wnt Signaling Pathway in Human Breast Cancer

Triple-negative breast cancer is the leading worldwide cause of cancer-related deaths in women. The prospection and development of new substances with antitumoral potential is of great importance for the treatment of this disease. The objective of this work was to identify a commercial drug or ligand that could potentially bind to the FZD7 transmembrane protein and inactivate the Wnt signaling pathway in triple-negative breast cancer cells. We aimed at computationally modeling the FZD7, Wnt3, and Wnt3a proteins, at making them available in protein model databases, and at conducting docking analysis to assess the binding free energy between FZD7 and the selected ligands. The Wnt3 and Wnt3a proteins were modeled by homology modeling, and the FZD7 protein was modeled by homology modeling and ab initio modeling. The ligands were selected based on their similarity to the palmitoleic acid and were gathered from the ZINC database. A total of 30 commercially available ligands were found in the ZINC database. The docking results show that the ligands zinc08221009, zinc13546050, zinc05260769, zinc04529321, and zinc05972969 are good candidates for novel drug development. The created models and conducted analysis by this work will most certainly help in future research on the Wnt signaling pathway and its components.

Targeting the Versatile Wnt/β-Catenin Pathway in Cancer Biology and Therapeutics: From Concept to Actionable Strategy

This expert review offers a critical synthesis of the latest insights and approaches at targeting the Wnt/β-catenin pathway in various cancers such as colorectal cancer, melanoma, leukemia, and breast and lung cancers. Notably, from organogenesis to cancer, the Wnt/β-catenin signaling displays varied and highly versatile biological functions in animals, with virtually all tissues requiring the Wnt/β-catenin signaling in one way or the other. Aberrant expression of the members of the Wnt/β-catenin has been implicated in many pathological conditions, particularly in human cancers. Mutations in the Wnt/β-catenin pathway genes have been noted in diverse cancers. Biochemical and genetic data support the idea that inhibition of Wnt/β-catenin signaling is beneficial in cancer therapeutics. The interaction of this important pathway with other signaling systems is also noteworthy, but remains as an area for further research and discovery. In addition, formation of different complexes by components of the Wnt/β-catenin pathway and the precise roles of these complexes in the cytoplasmic milieu are yet to be fully elucidated. This article highlights the latest medical technologies in imaging, single-cell omics, use of artificial intelligence (e.g., machine learning techniques), genome sequencing, quantum computing, molecular docking, and computational softwares in modeling interactions between molecules and predicting protein-protein and compound-protein interactions pertinent to the biology and therapeutic value of the Wnt/β-catenin signaling pathway. We discuss these emerging technologies in relationship to what is currently needed to move from concept to actionable strategies in translating the Wnt/β-catenin laboratory discoveries to Wnt-targeted cancer therapies and diagnostics in the clinic.

Functional exosome-mediated co-delivery of doxorubicin and hydrophobically modified microRNA 159 for triple-negative breast cancer therapy

Exosomes (Exo) hold great promise as endogenous nanocarriers that can deliver biological information between cells. However, Exo are limited in terms of their abilities to target specific recipient cell types. We developed a strategy to isolate Exo exhibiting increased binding to integrin α_vβ₃. Binding occurred through a modified version of a disintegrin and metalloproteinase 15 (A15) expressed on exosomal membranes (A15-Exo), which facilitated co-delivery of therapeutic quantities of doxorubicin (Dox) and cholesterol-modified miRNA 159 (Cho-miR159) to triple-negative breast cancer (TNBC) cells, both in vitro and in vivo. The targeted A15-Exo were derived from continuous protein kinase C activation in monocyte-derived macrophages. These cell-derived Exo displayed targeting properties and had a 2.97-fold higher production yield. In vitro, A15-Exo co-loaded with Dox and Cho-miR159 induced synergistic therapeutic effects in MDA-MB-231 cells. In vivo, miR159 and Dox delivery in a vesicular system effectively silenced the TCF-7 gene and exhibited improved anticancer effects, without adverse effects. Therefore, our data demonstrate the synergistic efficacy of co-delivering miR159 and Dox by targeted Exo for TNBC therapy.

Sphingosine Kinase 1 Signaling Promotes Metastasis of Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is the most aggressive breast cancer subtype. To identify TNBC therapeutic targets, we performed integrative bioinformatics analysis of multiple breast cancer patient-derived gene expression datasets and focused on kinases with FDA-approved or in-pipeline inhibitors. Sphingosine kinase 1 (SPHK1) was identified as a top candidate. SPHK1 overexpression or downregulation in human TNBC cell lines increased or decreased spontaneous metastasis to lungs in nude mice, respectively. SPHK1 promoted metastasis by transcriptionally upregulating the expression of the metastasis-promoting gene FSCN1 via NFκB activation. Activation of the SPHK1/NFκB/FSCN1 signaling pathway was associated with distance metastasis and poor clinical outcome in patients with TNBC. Targeting SPHK1 and NFκB using clinically applicable inhibitors (safingol and bortezomib, respectively) significantly inhibited aggressive mammary tumor growth and spontaneous lung metastasis in orthotopic syngeneic TNBC mouse models. These findings highlight SPHK1 and its downstream target, NFκB, as promising therapeutic targets in TNBC. SIGNIFICANCE: SPHK1 is overexpressed in TNBC and promotes metastasis, targeting SPHK1 or its downstream target NFκB with clinically available inhibitors could be effective for inhibiting TNBC metastasis.

Towards the first targeted therapy for triple-negative breast cancer: Repositioning of clofazimine as a chemotherapy-compatible selective Wnt pathway inhibitor

Wnt signaling is overactivated in triple-negative breast cancer (TNBC) and several other cancers, and its suppression emerges as an effective anticancer treatment. However, no drugs targeting the Wnt pathway exist on the market nor in advanced clinical trials. Here we provide a comprehensive body of preclinical evidence that an anti-leprotic drug clofazimine is effective against TNBC. Clofazimine specifically inhibits canonical Wnt signaling in a panel of TNBC cells in vitro. In several mouse xenograft models of TNBC, clofazimine efficiently suppresses tumor growth, correlating with in vivo inhibition of the Wnt pathway in the tumors. Clofazimine is well compatible with doxorubicin, exerting additive effects on tumor growth suppression, producing no adverse effects. Its excellent and well-characterized pharmacokinetics profile, lack of serious adverse effects at moderate (yet therapeutically effective) doses, its combinability with cytotoxic therapeutics, and the novel mechanistic mode of action make clofazimine a prime candidate for the repositioning clinical trials. Our work may bring forward the anti-Wnt targeted therapy, desperately needed for thousands of patients currently lacking targeted treatments.

The FZD7-TWIST1 axis is responsible for anoikis resistance and tumorigenesis in ovarian carcinoma

Frizzled family receptor 7 (FZD7), a Wnt signaling receptor, is associated with the maintenance of stem cell properties and cancer progression. FZD7 has emerged as a potential therapeutic target because it is capable of transducing both canonical and noncanonical Wnt signals. In this study, we investigated the regulatory pathway downstream of FZD7 and its functional roles. We found that FZD7 expression was crucial to the maintenance of the mesenchymal phenotype, anoikis resistance, and spheroid and tumor formation in ovarian cancer (OC). We identified TWIST1 as the crucial downstream effector of the FZD7 pathway. TWIST1, a basic helix loop helix transcription factor, is known to associate with mesenchymal and cancer stem cell phenotypes. Manipulating TWIST1 expression mimicked the functional consequences observed in the FZD7 model, and overexpression of TWIST1 partially rescued the functional phenotypes abolished by FZD7 knockdown. We further proved that FZD7 regulated TWIST1 expression through epigenetic modifications of H3K4me3 and H3K27ac at the TWIST1 proximal promoter. We also identified that the FZD7‐TWIST1 axis regulates the expression of BCL2, a gene that controls apoptosis. Identification of this FZD7‐TWIST1‐BCL2 pathway reaffirms the mechanism of anoikis resistance in OC. We subsequently showed that the FZD7‐TWIST1 axis can be targeted by using a small molecule inhibitor of porcupine, an enzyme essential for secretion and functional activation of Wnts. In conclusion, our results identified that the FZD7‐TWIST1 axis is important for tumorigenesis and anoikis resistance, and therapeutic inhibition results in cell death in OCs.

Molecular mechanism of triple-negative breast cancer-associated BRCA1 and the identification of signaling pathways

BRAC1 has multiple important interactions with triple-negative breast cancer, the specific molecular characteristics of this interaction, however, have not yet been completely elucidated. By examining cell signaling pathways, important information for comprehending the potential mechanisms of this cancer may become known. The aim of the present study was to identify the effects of BRAC1 and to find the signaling pathway(s) involved in the pathogenic mechanism of triple-negative breast cancer. In this study, GSE27447 microarray data were obtained from the Gene Expression Omnibus (GEO) database of the National Center for Biotechnology Information, and differentially expressed genes (DEGs) from GSE27447 were distinguished by Significant Analysis of Microarray. Gene ontology (GO) analysis was carried out on 132 upregulated and 198 downregulated genes with DAVID. The signaling was forecast by the Kyoto Encyclopedia of Genes and Genomes (KEGG). Transcription factors were recognized by TFatS. The BRAC1 relevant protein-protein interaction networks (PPI) were fixed by STRING and visualized by CytoScape. Overall, the upregulated DEGs, which included CR2, IGHM, PRKCB, CARD11, PLCG2, CD79A, IGKC and CD27, were primarily enriched in the terms associated with immune responses, and the downregulated DEGs, which included STARD3, ALDH8A1, SRD5A3, CACNA1H, UGT2B4, SDR16C5 and MED1, were primarily enriched in the hormone metabolic process. In addition, 13 pathways, such as the B-cell receptor-signaling pathway, the hormone synthesis signaling pathway and the oxytocin-signaling pathway, were chosen. MYC, SP1 and CTNNB1 were determined to be enriched in triple-negative breast cancer. A total of 8 genes were identified to be downregulated in the BRAC1-related PPI network. The results of the present study show a fresh angle on the molecular mechanism of triple-negative breast cancer and indicate a possible target for its treatment.

LncRNA AWPPH promotes the growth of triple-negative breast cancer by up-regulating frizzled homolog 7 (FZD7)

Background: LncRNA AWPPH is a recently identified critical player in the development of several types of human malignancies, our study aimed to investigate the role of AWPPH in triple-negative breast cancer. Methods: In the present study, expression of AWPPH in tumor tissues and adjacent healthy tissues of patients with triple-negative breast cancer as well as in plasma of both patients and healthy people was detected by qRT-PCR. Application potentials of AWPPH in the diagnosis and prognosis of triple-negative breast cancer were evaluated by ROC curve analysis and survival curve analysis, respectively. AWPPH expression vectors and frizzled homolog 7 (FZD7) siRNAs were transfected into cells of human breast cancer cell lines. Expression of FZD7 was detected by Western blot, and cell proliferation was detected using CCK-8 kit. Results: We observed that AWPPH was significantly up-regulated in tumor tissues than in paired adjacent healthy tissues of patients. Plasma levels of AWPPH were higher in patients than in controls. AWPPH overexpression promoted cancer cell proliferation and up-regulated FZD7 expression. FZD7 siRNA silencing inhibited cancer cell proliferation but did not significantly affect AWPPH expression. Compared with cells with AWPPH overexpression alone, cells with both FZD7 siRNA silencing and AWPPH overexpression showed significantly reduced proliferation ability. Conclusions: We conclude that LncRNA AWPPH may promote the growth of triple-negative breast cancer by up-regulating FZD7.

Racial Disparity and Triple-Negative Breast Cancer in African-American Women: A Multifaceted Affair between Obesity, Biology, and Socioeconomic Determinants

Triple negative breast cancer (TNBC) is a molecularly heterogeneous disease whose incidence is disproportionately higher in African American (AA) women compared to European American (EA) women. Earlier onset, more advanced stage at diagnosis, and aggressive tumor phenotype are some of the characteristic features of TNBC in women with African ethnicity in comparison to EA women, denoting one of the most significant examples of racial disparity in oncology. It is still contentious whether health disparities result in aggressive behavior of TNBC in AA women or it is indeed a molecularly distinct disease. Given the “gaps-in-knowledge” surrounding racial disparity in TNBC, this review discusses various socioeconomic factors and the genetic predispositions contributing to poor prognosis of TNBC in AA women. While socioeconomic factors may contribute to poorer survival, multiple preclinical and clinical studies suggest inherent genetic risk factors and aberrant activation of oncogenic pathways in AA TNBC. Additionally, AA women are more likely to be obese and obesity is known to drive a molecular circuitry resulting in aggressive tumor progression indicating a potential obesity-TNBC axis at work in AA women. Given the multifactorial nature of AA TNBC, a transdisciplinary approach may help bridge the disparity that exists between AA and EA TNBC.

GPCR Modulation in Breast Cancer

Breast cancer is the most prevalent cancer found in women living in developed countries. Endocrine therapy is the mainstay of treatment for hormone-responsive breast tumors (about 70% of all breast cancers) and implies the use of selective estrogen receptor modulators and aromatase inhibitors. In contrast, triple-negative breast cancer (TNBC), a highly heterogeneous disease that may account for up to 24% of all newly diagnosed cases, is hormone-independent and characterized by a poor prognosis. As drug resistance is common in all breast cancer subtypes despite the different treatment modalities, novel therapies targeting signaling transduction pathways involved in the processes of breast carcinogenesis, tumor promotion and metastasis have been subject to accurate consideration. G protein-coupled receptors (GPCRs) are the largest family of cell-surface receptors involved in the development and progression of many tumors including breast cancer. Here we discuss data regarding GPCR-mediated signaling, pharmacological properties and biological outputs toward breast cancer tumorigenesis and metastasis. Furthermore, we address several drugs that have shown an unexpected opportunity to interfere with GPCR-based breast tumorigenic signals.

Wnt receptor Frizzled 8 is a target of ERG in prostate cancer

Prostate cancer (PCa) is one of the most frequently diagnosed cancers among men. Many molecular changes have been detailed during PCa progression. The gene encoding the transcription factor ERG shows recurrent rearrangement, resulting in the overexpression of ERG in the majority of prostate cancers. Overexpression of ERG plays a critical role in prostate oncogenesis and development of metastatic disease. Among the downstream effectors of ERG, Frizzled family member FZD4 has been shown to be a target of ERG. Frizzled-8 (FZD8) has been shown to be involved in PCa bone metastasis. In the present study, we show that the expression of FZD8 is directly correlated with ERG expression in PCa. Furthermore, we show that ERG directly targets and activates FZD8 by binding to its promoter. This activation is specific to ETS transcription factor ERG and not ETV1. We propose that ERG overexpression in PCa leads to induction of Frizzled family member FZD8, which is known to activate the Wnt pathway. Taken together, these findings uncover a novel mechanism for PCa metastasis, and indicate that FZD8 may represent a potential therapeutic target for PCa.

Contribution of the Wnt Pathway to Defining Biology of Glioblastoma

Glioblastoma (GBM), a highly lethal brain tumor, has been comprehensively characterized at the molecular level with the identification of several potential treatment targets. Data concerning the Wnt pathway are relatively sparse, but apparently very important in defining several aspects of tumor biology. The Wnt ligands are involved in numerous basic biological processes including regulation of embryogenic development, cell fate determination, and organogenesis, but growing amount of data also support the roles of Wnt pathways in the formation of many tumors, including gliomas. Two main Wnt pathways are distinguished: the canonical (β-catenin) and non-canonical (planar cell polarity, Wnt/Ca²⁺) routes. Wnt signaling regulates glioma stem cells (GSCs), thereby defining invasive potential, recurrence, and treatment resistance of GBM. Some observations suggest that the Wnt pathways are differentially active in molecular subtypes of this tumor, thereby may also guide prognostication and novel therapeutic decisions. In this review, we highlight main elements and biological relevance of the Wnt pathways, primarily focusing on the pathogenesis and subtypes of GBM. Finally, we briefly summarize newer therapeutic strategies targeting networks of the Wnt signaling cascades and their molecular associates that appear to be marked contributors to GBM aggressiveness.

The "Yin and Yang" of Natural Compounds in Anticancer Therapy of Triple-Negative Breast Cancers

Among the different types of breast cancers, triple-negative breast cancers (TNBCs) are highly aggressive, do not respond to conventional hormonal/human epidermal growth factor receptor 2 (HER2)-targeted interventions due to the lack of the respective receptor targets, have chances of early recurrence, metastasize, tend to be more invasive in nature, and develop drug resistance. The global burden of TNBCs is increasing regardless of the number of cytotoxic drugs being introduced into the market each year as they have only moderate efficacy and/or unforeseen side effects. Therefore, the demand for more efficient therapeutic interventions, with reduced side effects, for the treatment of TNBCs is rising. While some plant metabolites/derivatives actually induce the risk of cancers, many plant-derived active principles have gained attention as efficient anticancer agents against TNBCs, with fewer adverse side effects. Here we discuss the possible oncogenic molecular pathways in TNBCs and how the purified plant-derived natural compounds specifically target and modulate the genes and/or proteins involved in these aberrant pathways to exhibit their anticancer potential. We have linked the anticancer potential of plant-derived natural compounds (luteolin, chalcones, piperine, deguelin, quercetin, rutin, fisetin, curcumin, resveratrol, and others) to their ability to target multiple dysregulated signaling pathways (such as the Wnt/β-catenin, Notch, NF-κB, PI3K/Akt/mammalian target of rapamycin (mTOR), mitogen-activated protein kinase (MAPK) and Hedgehog) leading to suppression of cell growth, proliferation, migration, inflammation, angiogenesis, epithelial-mesenchymal transition (EMT) and metastasis, and activation of apoptosis in TNBCs. Plant-derived compounds in combination with classical chemotherapeutic agents were more efficient in the treatment of TNBCs, possibly with lesser side effects.

Wnt signaling in human and mouse breast cancer: Focusing on Wnt ligands, receptors and antagonists

Wnt proteins, a group of secreted glycoproteins, mainly combine with receptors Frizzled (FZD) and/or low-density-lipoprotein receptor-related proteins 5/6 (LRP5/6), initiating β-catenin-dependent and -independent signaling pathways. These pathways, which can be regulated by some secreted antagonists such as secreted Frizzled-related proteins (SFRP) and dickkopf-related protein (DKK), play a critical role in embryo development and adult homeostasis. Overactivation of Wnt signaling has been implicated in some human diseases including cancer. Wnt transgenic mice provide convincing evidence that Wnt signaling is involved in breast cancer initiation and progression, which is further strengthened by observations on human clinical breast cancer patients and studies on in vitro cultured human breast cancer cells. This review focuses on the roles of Wnt ligands, receptors and antagonists in breast cancer development instead of molecules or signaling transactivating β-catenin independent on Wnt upstream components.

Targeting LRP8 inhibits breast cancer stem cells in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is the most difficult subtype of breast cancer to treat due to a paucity of effective targeted therapies. Many studies have reported that breast cancer stem cells (BCSCs) are enriched in TNBC and are responsible for chemoresistance and metastasis. In this study, we identify LRP8 as a novel positive regulator of BCSCs in TNBC. LRP8 is highly expressed in TNBC compared to other breast cancer subtypes and its genomic locus is amplified in 24% of TNBC tumors. Knockdown of LRP8 in TNBC cell lines inhibits Wnt/β-catenin signaling, decreases BCSCs, and suppresses tumorigenic potential in xenograft models. LRP8 knockdown also induces a more differentiated, luminal-epithelial phenotype and thus sensitizes the TNBC cells to chemotherapy. Together, our study highlights LRP8 as a novel therapeutic target for TNBC as inhibition of LRP8 can attenuate Wnt/β-catenin signaling to suppress BCSCs.