Hedgehog signalling in breast cancer

Stimulation of skeletal stem cells in the growth plate promotes linear bone growth

Recently, skeletal stem cells were shown to be present in the epiphyseal growth plate (epiphyseal skeletal stem cells, epSSCs), but their function in connection with linear bone growth remains unknown. Here, we explore the possibility that modulating the number of epSSCs can correct differences in leg length. First, we examined regulation of the number and activity of epSSCs by Hedgehog (Hh) signaling. Both systemic activation of Hh pathway with Smoothened agonist (SAG) and genetic activation of Hh pathway by Patched1 (Ptch1) ablation in Pthrp-creER Ptch1fl/fl tdTomato mice promoted proliferation of epSSCs and clonal enlargement. Transient intra-articular administration of SAG also elevated the number of epSSCs. When SAG-containing beads were implanted into the femoral secondary ossification center of 1 leg of rats, this leg was significantly longer 1 month later than the contralateral leg implanted with vehicle-containing beads, an effect that was even more pronounced 2 and 6 months after implantation. We conclude that Hh signaling activates growth plate epSSCs, which effectively leads to increased longitudinal growth of bones. This opens therapeutic possibilities for the treatment of differences in leg length.

Usability of serum hedgehog signalling proteins as biomarkers in canine mammary carcinomas

BACKGROUND

The hedgehog signalling pathway has been implicated in tumourigenesis and progression of many tumour types. This pathway has recently emerged as a therapeutic target, and inhibitors of hedgehog signalling have gained considerable attention. In dogs, the roles of hedgehog signals in several types of tumours have been investigated, but their relationship with canine mammary gland tumours (MGTs) has not been established. This study aimed to evaluate the expression of sonic hedgehog (SHH) and glioma-associated oncogene 1 (GLI-1) in the serum and mammary tumour tissues of dogs.

RESULTS

SHH and GLI-1 protein expression levels were significantly higher in MGT tissues than in normal mammary gland tissues, as well as in malignant MGT specimens than in benign MGT specimens. Serum levels of SHH and GLI-1 were higher in MGT patients than in healthy controls (p < .001 and .001, respectively). Serum SHH level showed a statistically significant relationship with metastatic status (p = .01), and serum GLI-1 level showed a statistically significant relationship with histologic grade (p = 0.048) and metastatic status (p = 0.007). Serum hedgehog signalling protein levels were not significantly associated with breed size, sex, tumour size, or histologic type.

CONCLUSIONS

Hedgehog signalling protein expression in canine MGT tissue and serum differed according to the histological classification (benign and malignant) and metastatic status, indicating a relationship between the hedgehog signalling pathway and canine MGT. Thus, the hedgehog signalling pathway may serve as a new biomarker and therapeutic target in canine MGT patients.

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

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

Targeted Therapy and Mechanisms of Drug Resistance in Breast Cancer

Breast cancer is the most common cause of cancer-related death in women worldwide. Multidrug resistance (MDR) has been a large hurdle in reducing BC death rates. The drug resistance mechanisms include increased drug efflux, enhanced DNA repair, senescence escape, epigenetic alterations, tumor heterogeneity, tumor microenvironment (TME), and the epithelial-to-mesenchymal transition (EMT), which make it challenging to overcome. This review aims to explain the mechanisms of resistance in BC further, identify viable drug targets, and elucidate how those targets relate to the progression of BC and drug resistance.

FN1 overexpression is correlated with unfavorable prognosis and immune infiltrates in breast cancer

Objective: To investigate the correlation of fibronectin 1 (FN1) expression with prognosis and tumor-infiltrating immune cells in breast cancer (BRCA).

Methods: FN1 mRNA and protein expressions were analyzed through Tumor Immune Estimation Resource (TIMER), Gene Set Cancer Analysis (GSCA), Human Protein Atlas (HPA) databases, and immunohistochemical analysis. The clinicopathological characteristics and genetic factors affecting the FN1 mRNA expression were assessed by various public databases. Then, we analyzed the prognostic value of FN1 in BRCA by Kaplan-Meier plotter, receiver operating characteristic, and Cox regression analyses. Further, the UCSC Xena database was used to retrieve TCGA-BRCA expression profiles for functional enrichment analysis and immune cell infiltration analysis. The potential drugs for the BRCA patients with high- FN1 expression were identified using the connectivity map analysis.

Results: FN1 was upregulated in BRCA tissues compared with normal tissues. High FN1 mRNA expression was correlated with poor clinical outcomes and had good performance in predicting the survival status of BRCA patients. Further, Cox regression analysis showed that FN1 was an independent prognostic factor for predicting the overall survival of patients with BRCA. Moreover, hypermethylation of FN1 contributed to a better prognosis for BRCA patients. Functional enrichment analyses revealed the ECM-receptor interaction pathway and focal adhesion as the common pathways. Moreover, FN1 showed a significant association with tumor-infiltrating immune cells and immune checkpoint inhibitors. Several drugs such as telmisartan, malotilate, and seocalcitol may have therapeutic effects in BRCA patients with high FN1 expression.

Conclusion: FN1 might serve as a novel prognostic biomarker and a novel therapeutic target for BRCA. Besides, the association of FN1 with immune cells and immune checkpoint inhibitors may provide assistance for BRCA treatment.

Cilia-localized GID/CTLH ubiquitin ligase complex regulates protein homeostasis of sonic hedgehog signaling components

Cilia are evolutionarily conserved organelles that orchestrate a variety of signal transduction pathways, such as sonic hedgehog (SHH) signaling, during embryonic development. Our recent studies have shown that loss of GID ubiquitin ligase function results in aberrant AMP-activated protein kinase (AMPK) activation and elongated primary cilia, which suggests a functional connection to cilia. Here, we reveal that the GID complex is an integral part of the cilium required for primary cilia-dependent signal transduction and the maintenance of ciliary protein homeostasis. We show that GID complex subunits localize to cilia in both Xenopus laevis and NIH3T3 cells. Furthermore, we report SHH signaling pathway defects that are independent of AMPK and mechanistic target of rapamycin (MTOR) activation. Despite correct localization of SHH signaling components at the primary cilium and functional GLI3 processing, we find a prominent reduction of some SHH signaling components in the cilium and a significant decrease in SHH target gene expression. Since our data reveal a critical function of the GID complex at the primary cilium, and because suppression of GID function in X. laevis results in ciliopathy-like phenotypes, we suggest that GID subunits are candidate genes for human ciliopathies that coincide with defects in SHH signal transduction.

Hedgehog Pathway Inhibitors as Targeted Cancer Therapy and Strategies to Overcome Drug Resistance

Hedgehog (Hh) signaling is a highly conserved pathway that plays a vital role during embryonic development. Recently, uncontrolled activation of this pathway has been demonstrated in various types of cancer. Therefore, Hh pathway inhibitors have emerged as an important class of anti-cancer agents. Unfortunately, however, their reputation has been tarnished by the emergence of resistance during therapy, necessitating clarification of mechanisms underlying the drug resistance. In this review, we briefly overview canonical and non-canonical Hh pathways and their inhibitors as targeted cancer therapy. In addition, we summarize the mechanisms of resistance to Smoothened (SMO) inhibitors, including point mutations of the drug binding pocket or downstream molecules of SMO, and non-canonical mechanisms to reinforce Hh pathway output. A distinct mechanism involving loss of primary cilia is also described to maintain GLI activity in resistant tumors. Finally, we address the main strategies to circumvent the drug resistance. These strategies include the development of novel and potent inhibitors targeting different components of the canonical Hh pathway or signaling molecules of the non-canonical pathway. Further studies are necessary to avoid emerging resistance to Hh inhibitors and establish an optimal customized regimen with improved therapeutic efficacy to treat various types of cancer, including basal cell carcinoma.

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

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

Cancer Stem Cells Contribute to Drug Resistance in Multiple Different Ways

Many tumors are resistant to conventional cancer therapies because a tumor is composed of heterogeneous cell population. Especially, subpopulation of cancer stem cells, which have self-renewal and differentiation properties and responsible for the tumor initiation, is generally considered resistant to chemo-, radio-, and immune therapy. Understanding the mechanism of drug resistance in cancer stem cells should lead to establish more effective therapeutic strategies. Actually, different molecular mechanisms are conceivable for cancer stem cells acquiring drug resistance. These mechanisms include not only cytoplasmic signaling pathways but also the intercellular communications in the tumor microenvironment. Recently, a great deal of successful reports challenged to elucidate the mechanisms of drug resistance and to develop novel treatments targeting cancer stem cells.

Targeting Cancer Stem Cell Markers or Pathways: A Potential Therapeutic Strategy for Oral Cancer Treatment

Cancer stem cells (CSCs) are a small subset of cancer cells with stem cell-like properties, self-renewal potential, and differentiation capacity into multiple cell types. Critical genetic alterations or aberrantly activated signaling pathways associated with drug resistance and recurrence have been observed in multiple types of CSCs. In this context, CSCs are considered to be responsible for tumor initiation, growth, progression, therapeutic resistance, and metastasis. Therefore, to effectively eradicate CSCs, tremendous efforts have been devoted to identify specific target molecules that play a critical role in regulating their distinct functions and to develop novel therapeutics, such as proteins, monoclonal antibodies, selective small molecule inhibitors, and small antisense RNA (asRNA) drugs. Similar to other CSC types, oral CSCs can be characterized by certain pluripotency-associated markers, and oral CSCs can also survive and form 3D tumor spheres in suspension culture conditions. These oral CSC-targeting therapeutics selectively suppress specific surface markers or key signaling components and subsequently inhibit the stem-like properties of oral CSCs. A large number of new therapeutic candidates have been tested, and some products are currently in the pre-clinical or clinical development phase. In the present study, we review new oral CSC-targeted therapeutic strategies and discuss the various specific CSC surface markers and key signaling components involved in the stem-like properties, growth, drug resistance, and tumorigenicity of oral CSCs.

Ubiquitin-specific peptidase 37: an important cog in the oncogenic machinery of cancerous cells

Protein ubiquitination is one of the most crucial posttranslational modifications responsible for regulating the stability and activity of proteins involved in homeostatic cellular function. Inconsistencies in the ubiquitination process may lead to tumorigenesis. Ubiquitin-specific peptidases are attractive therapeutic targets in different cancers and are being evaluated for clinical development. Ubiquitin-specific peptidase 37 (USP37) is one of the least studied members of the USP family. USP37 controls numerous aspects of oncogenesis, including stabilizing many different oncoproteins. Recent work highlights the role of USP37 in stimulating the epithelial-mesenchymal transition and metastasis in lung and breast cancer by stabilizing SNAI1 and stimulating the sonic hedgehog pathway, respectively. Several aspects of USP37 biology in cancer cells are yet unclear and are an active area of research. This review emphasizes the importance of USP37 in cancer and how identifying its molecular targets and signalling networks in various cancer types can help advance cancer therapeutics.

Molecular epigenetic dynamics in breast carcinogenesis

Breast cancer has become one of the most common dreadful diseases that target women across the globe. The most obvious reasons we associate with it are either genetic mutations or dysregulation of pathways. However, there is yet another domain that has a significant role in influencing the genetic mutations and pathways. Epigenetic mechanisms influence these pathways either independently or in association with genetic mutations, thereby expediting the process of breast carcinogenesis. Breast cancer is governed by various transduction pathways such as PI3K/AKT/mTOR, NOTCH, β Catenin, NF-kB, Hedgehog, etc. There are many proteins as well that serve to be tumor suppressors but somehow lose their ability to function. This may be because of either genetic mutation or a process that represses their function. Apart from these, there are a lot of individual factors like puberty, breastfeeding, abortion, parity, circadian rhythm, alcohol consumption, pollutants, and obesity that drive these mutations and hence alter the pathways. Epigenetic mechanisms like DNA methylation, histone modifications, and lncRNAs directly or indirectly bring alterations in the proteins that are involved in the pathways. They do this by either promoting the transcription of genes or by repressing it at the ground genetic level that advances breast carcinogenesis. Epigenetics precedes genetic mutation in driving carcinogenesis and so, it needs to be explored further to diversify the possibilities of target specific treatments. In this review, the general role of DNA methylation, histone modification, and lncRNAs in breast cancer and their role in influencing the oncogenic signaling pathways along with the various factors governing them have been discussed for a better understanding of the role of epigenetics in breast carcinogenesis.

Drug resistance and Cancer stem cells

Therapy resistance is a major problem when treating cancer patients as cancer cells develop mechanisms that counteract the effect of therapeutic compounds, leading to fit and more aggressive clones that contribute to poor prognosis. Therapy resistance can be both intrinsic and/or acquired. These are multifactorial events, and some are related to factors including adaptations in cancer stem cells (CSCs), epithelial-mesenchymal transition (EMT), deregulation of key signaling pathways, drug efflux through ABC transporters, acquired mutations, evading apoptosis, and activation of DNA damage response among others. Among these factors, CSCs represent the major source of therapy resistance. CSCs are a subset of tumor cells that are capable of self-renewal and multilineage progenitor expansion that are known to be intrinsically resistant to anticancer treatments. Multiple clones of CSCs pre-exist, and some can adopt and expand easily to changes in the tumor microenvironment (TME) and/or in response to radio- and chemotherapy. A combination of both intrinsic and extrinsic factors contributes to CSC-mediated therapy resistance. In this review, we will focus on CSCs and therapy resistance as well as suggest strategies to eliminate CSCs and, therefore, overcome resistance. Video abstract.

Targeting the Sonic Hedgehog Pathway to Suppress the Expression of the Cancer Stem Cell (CSC)-Related Transcription Factors and CSC-Driven Thyroid Tumor Growth

Simple Summary

Poorly differentiated and anaplastic thyroid cancers respond poorly to surgery, radiation, and hormone therapy. Cancer stem cells play an important role in tumor growth, drug resistance, and recurrence. This study focuses on how the sonic hedgehog (Shh) pathway maintains thyroid cancer stem cell self-renewal and whether it can be targeted for anticancer therapy. The authors report that the Shh pathway regulates the expression of BMI1 and SOX2, two genes involved in stem cell self-renewal, and that targeting the Shh pathway has little effect on thyroid tumor xenografts but can inhibit the growth of tumor xenografts derived from thyroid cancer stem cells. This study advances the knowledge on how thyroid cancer stem cells regenerate and highlights the potential therapeutic values of targeting the Shh pathway.

Abstract

The sonic hedgehog (Shh) pathway plays important roles in tumorigenesis, tumor growth, drug resistance, and metastasis. We and others have reported earlier that this pathway is highly activated in thyroid cancer. However, its role in thyroid cancer stem cell (CSC) self-renewal and tumor development remains incompletely understood. B lymphoma Mo-MLV insertion region 1 homolog (BMI1) and SRY-Box Transcription Factor 2 (SOX2) are two CSC-related transcription factors that have been implicated in promoting CSC self-renewal. The objective of our current investigation was to determine the role of the Shh pathway in regulating BMI1 and SOX2 expression in thyroid cancer and promoting thyroid tumor growth and development. Here we report that inhibition of the Shh pathway by Gli1 siRNA or by cyclopamine and GANT61 reduced BMI1 and SOX2 expression in SW1736 and KAT-18 cells, two anaplastic thyroid cancer cell lines. The opposite results were obtained in cells overexpressing Gli1 or its downstream transcription factor Snail. The Shh pathway regulated SOX2 and BMI1 expression at a transcriptional and post-transcriptional level, respectively. GANT61 treatment suppressed the growth of SW1736 CSC-derived tumor xenografts but did not significantly inhibit the growth of tumors grown from bulk tumor cells. Clinicopathological analyses of thyroid tumor specimens by immunohistochemical (IHC) staining revealed that BMI1 and SOX2 were highly expressed in thyroid cancer and correlated with Gli1 expression. Our study provides evidence that activation of the Shh pathway leads to increased BMI1 and SOX2 expression in thyroid cancer and promotes thyroid CSC-driven tumor initiation. Targeting the Shh pathway may have therapeutic value for treating thyroid cancer and preventing recurrence.

Hedgehog Signaling: Implications in Cancers and Viral Infections

The hedgehog (SHH) signaling pathway is primarily involved in embryonic gut development, smooth muscle differentiation, cell proliferation, adult tissue homeostasis, tissue repair following injury, and tissue polarity during the development of vertebrate and invertebrate organisms. GLIoma-associated oncogene homolog (GLI) family of zinc-finger transcription factors and smoothened (SMO) are the signal transducers of the SHH pathway. Both SHH ligand-dependent and independent mechanisms activate GLI proteins. Various transcriptional mechanisms, posttranslational modifications (phosphorylation, ubiquitination, proteolytic processing, SUMOylation, and acetylation), and nuclear-cytoplasmic shuttling control the activity of SHH signaling pathway proteins. The dysregulated SHH pathway is associated with bone and soft tissue sarcomas, GLIomas, medulloblastomas, leukemias, and tumors of breast, lung, skin, prostate, brain, gastric, and pancreas. While extensively studied in development and sarcomas, GLI family proteins play an essential role in many host-pathogen interactions, including bacterial and viral infections and their associated cancers. Viruses hijack host GLI family transcription factors and their downstream signaling cascades to enhance the viral gene transcription required for replication and pathogenesis. In this review, we discuss a distinct role(s) of GLI proteins in the process of tumorigenesis and host-pathogen interactions in the context of viral infection-associated malignancies and cancers due to other causes. Here, we emphasize the potential of the Hedgehog (HH) pathway targeting as a potential anti-cancer therapeutic approach, which in the future could also be tested in infection-associated fatalities.

Prognostic significance of hedgehog signaling network-related gene expression in breast cancer patients

Breast cancer continues to be a serious public health problem. The role of the hedgehog pathway in normal development of the mammary gland as well as in carcinogenesis and progression of breast cancer is the subject of intense investigation, revealing functional interactions with cell surface heparan sulfate. Nevertheless, its influence on breast cancer prognosis, and its relation to specific sulfation motifs in heparan sulfate have only been poorly studied in large patient cohorts. Using the public database KMplotter that includes gene expression and survival data of 3951 patients, we found that the higher expression of SHH, HHAT, PTCH1, GLI1, GLI2, and GLI3 positively influences breast cancer prognosis. Stratifying patients according to the expression of hormone receptors, histological grade, lymph node metastasis, and systemic therapy, we observed that GLI1, GLI2, and GLI3 expression, as well as co-expression of SHH and ELP1 were associated with worse relapse-free survival in patients with HER2-positive tumors. Moreover, GLI1 expression in progesterone receptor-negative tumors and GLI3 expression in grade 3 tumors correlated with poor prognosis. SHH, in a panel of cell lines representing different breast cancer subtypes, and HHAT, PTCH1, GLI1, GLI2, and GLI3 were mostly expressed in cell lines classified as HER2-positive and basal-like. Expression of SHH, HHAT, GLI2, and GLI3 was differentially affected by overexpression of the heparan sulfate sulfotransferases HS2ST1 and HS3ST2 in vitro. Although high HS2ST1 expression was associated with poor prognosis in KMplotter analysis, high levels of HS3ST2 were associated with a good prognosis, except for ER-positive breast cancer. We suggest the GLI transcription factors as possible markers for the diagnosis, treatment, and prognosis of breast cancer especially in HER2-positive tumors, but also in progesterone receptor-negative and grade-3 tumors. The pathway interaction and prognostic impact of specific heparan sulfate sulfotransferases provide novel perspectives regarding a therapeutical targeting of the hedgehog pathway in breast cancer.

Downregulation of miR-506-3p Facilitates EGFR-TKI Resistance through Induction of Sonic Hedgehog Signaling in Non-Small-Cell Lung Cancer Cell Lines

Non-small-cell lung cancer (NSCLC) patients with epidermal growth factor receptor (EGFR) mutation eventually develop resistance to EGFR-targeted tyrosine kinase inhibitors (TKIs). Treatment resistance remains the primary obstacle to the successful treatment of NSCLC. Although drug resistance mechanisms have been studied extensively in NSCLC, the regulation of these mechanisms has not been completely understood. Recently, increasing numbers of microRNAs (miRNAs) are implicated in EGFR-TKI resistance, indicating that miRNAs may serve as novel targets and may hold promise as predictive biomarkers for anti-EGFR therapy. MicroRNA-506 (miR-506) has been identified as a tumor suppressor in many cancers, including lung cancer; however, the role of miR-506 in lung cancer chemoresistance has not yet been addressed. Here we report that miR-506-3p expression was markedly reduced in erlotinib-resistant (ER) cells. We identified Sonic Hedgehog (SHH) as a novel target of miR-506-3p, aberrantly activated in ER cells. The ectopic overexpression of miR-506-3p in ER cells downregulates SHH signaling, increases E-cadherin expression, and inhibits the expression of vimentin, thus counteracting the epithelial-mesenchymal transition (EMT)-mediated chemoresistance. Our results advanced our understanding of the molecular mechanisms underlying EGFR-TKI resistance and indicated that the miR-506/SHH axis might represent a novel therapeutic target for future EGFR mutated lung cancer treatment.

Pan-cancer analysis of differential DNA methylation patterns

Background

DNA methylation is a key epigenetic regulator contributing to cancer development. To understand the role of DNA methylation in tumorigenesis, it is important to investigate and compare differential methylation (DM) patterns between normal and case samples across different cancer types. However, current pan-cancer analyses call DM separately for each cancer, which suffers from lower statistical power and fails to provide a comprehensive view for patterns across cancers.

Methods

In this work, we propose a rigorous statistical model, PanDM, to jointly characterize DM patterns across diverse cancer types. PanDM uses the hidden correlations in the combined dataset to improve statistical power through joint modeling. PanDM takes summary statistics from separate analyses as input and performs methylation site clustering, differential methylation detection, and pan-cancer pattern discovery. We demonstrate the favorable performance of PanDM using simulation data. We apply our model to 12 cancer methylome data collected from The Cancer Genome Atlas (TCGA) project. We further conduct ontology- and pathway-enrichment analyses to gain new biological insights into the pan-cancer DM patterns learned by PanDM.

Results

PanDM outperforms two types of separate analyses in the power of DM calling in the simulation study. Application of PanDM to TCGA data reveals 37 pan-cancer DM patterns in the 12 cancer methylomes, including both common and cancer-type-specific patterns. These 37 patterns are in turn used to group cancer types. Functional ontology and biological pathways enriched in the non-common patterns not only underpin the cancer-type-specific etiology and pathogenesis but also unveil the common environmental risk factors shared by multiple cancer types. Moreover, we also identify PanDM-specific DM CpG sites that the common strategy fails to detect.

Conclusions

PanDM is a powerful tool that provides a systematic way to investigate aberrant methylation patterns across multiple cancer types. Results from real data analyses suggest a novel angle for us to understand the common and specific DM patterns in different cancers. Moreover, as PanDM works on the summary statistics for each cancer type, the same framework can in principle be applied to pan-cancer analyses of other functional genomic profiles. We implement PanDM as an R package, which is freely available at http://www.sta.cuhk.edu.hk/YWei/PanDM.html.

Stimulation of Oncogene-Specific Tumor-Infiltrating T Cells through Combined Vaccine and αPD-1 Enable Sustained Antitumor Responses against Established HER2 Breast Cancer

PURPOSE

Despite promising advances in breast cancer immunotherapy, augmenting T-cell infiltration has remained a significant challenge. Although neither individual vaccines nor immune checkpoint blockade (ICB) have had broad success as monotherapies, we hypothesized that targeted vaccination against an oncogenic driver in combination with ICB could direct and enable antitumor immunity in advanced cancers.

EXPERIMENTAL DESIGN

Our models of HER2⁺ breast cancer exhibit molecular signatures that are reflective of advanced human HER2⁺ breast cancer, with a small numbers of neoepitopes and elevated immunosuppressive markers. Using these, we vaccinated against the oncogenic HER2Δ16 isoform, a nondriver tumor-associated gene (GFP), and specific neoepitopes. We further tested the effect of vaccination or anti-PD-1, alone and in combination.

RESULTS

We found that only vaccination targeting HER2Δ16, a driver of oncogenicity and HER2-therapeutic resistance, could elicit significant antitumor responses, while vaccines targeting a nondriver tumor-specific antigen or tumor neoepitopes did not. Vaccine-induced HER2-specific CD8⁺ T cells were essential for responses, which were more effective early in tumor development. Long-term tumor control of advanced cancers occurred only when HER2Δ16 vaccination was combined with αPD-1. Single-cell RNA sequencing of tumor-infiltrating T cells revealed that while vaccination expanded CD8 T cells, only the combination of vaccine with αPD-1 induced functional gene expression signatures in those CD8 T cells. Furthermore, we show that expanded clones are HER2-reactive, conclusively demonstrating the efficacy of this vaccination strategy in targeting HER2.

CONCLUSIONS

Combining oncogenic driver targeted vaccines with selective ICB offers a rational paradigm for precision immunotherapy, which we are clinically evaluating in a phase II trial (NCT03632941).

Association of the Epithelial-Mesenchymal Transition (EMT) with Cisplatin Resistance

Therapy resistance is a characteristic of cancer cells that significantly reduces the effectiveness of drugs. Despite the popularity of cisplatin (CP) as a chemotherapeutic agent, which is widely used in the treatment of various types of cancer, resistance of cancer cells to CP chemotherapy has been extensively observed. Among various reported mechanism(s), the epithelial-mesenchymal transition (EMT) process can significantly contribute to chemoresistance by converting the motionless epithelial cells into mobile mesenchymal cells and altering cell-cell adhesion as well as the cellular extracellular matrix, leading to invasion of tumor cells. By analyzing the impact of the different molecular pathways such as microRNAs, long non-coding RNAs, nuclear factor-κB (NF-ĸB), phosphoinositide 3-kinase-related protein kinase (PI3K)/Akt, mammalian target rapamycin (mTOR), and Wnt, which play an important role in resistance exhibited to CP therapy, we first give an introduction about the EMT mechanism and its role in drug resistance. We then focus specifically on the molecular pathways involved in drug resistance and the pharmacological strategies that can be used to mitigate this resistance. Overall, we highlight the various targeted signaling pathways that could be considered in future studies to pave the way for the inhibition of EMT-mediated resistance displayed by tumor cells in response to CP exposure.

GANT61 and curcumin-loaded PLGA nanoparticles for GLI1 and PI3K/Akt-mediated inhibition in breast adenocarcinoma

Current conventional mono and combination therapeutic strategies often fail to target breast cancer tissue effectively due to tumor heterogeneity comprising cancer stem cells (CSCs) and bulk tumor cells. This is further associated with drug toxicity and resistivity in the long run. A nanomedicine platform incorporating combination anti-cancer treatment might overcome these challenges and generate synergistic anti-cancer effects and also reduce drug toxicity. GANT61 and curcumin were co-delivered via polymeric nanoparticles (NPs) for the first time to elicit enhanced anti-tumor activity against heterogeneous breast cancer cell line MCF-7. We adopted the single-emulsion-solvent evaporation method for the preparation of the therapeutic NPs. The GANT61-curcumin PLGA NPs were characterized for their size, shape and chemical properties, and anti-cancer cell studies were undertaken for the plausible explanation of our hypothesis. The synthesized GANT61-curcumin PLGA NPs had a spherical, smooth surface morphology, and an average size of 347.4 d. nm. The NPs induced cytotoxic effects in breast cancer cells at a mid-minimal dosage followed by cell death via autophagy and apoptosis, reduction in their target protein expression along with compromising the self-renewal property of CSCs as revealed by their in vitro cell studies. The dual-drug NPs thus provide a novel perspective on aiding existing anti-cancer nanomedicine therapies to target a heterogeneous tumor mass effectively.

ITGA3 interacts with VASP to regulate stemness and epithelial-mesenchymal transition of breast cancer cells

BACKGROUND

The interaction of integrin and extracellular matrix (ECM) has a profound implication on pathological conditions such as tumor growth and infiltration. Related reports have confirmed that integrin α3 (ITGA3) influences the development of bladder cancer, head and neck cancer, colorectal cancer and other cancers. However, the mechanism of ITGA3 in breast cancer is unknown.

METHODS

The impact of ITGA3 on the biological features of breast cancer cells was explored using the Transwell and wound healing assays. In addition, its influence on stemness of breast cancer cells was examined with the sphere formation assay. The possible mechanism by which ITGA3 regulates breast cancer was explored using Western blot. The interaction between ITGA3 and VASP was determined by co-immunoprecipitation and immunofluorescence staining assays.

RESULTS

Results show that downregulation of ITGA3 promotes breast cancer cell proliferation, apoptosis, invasion and migration. Indeed, suppression of ITGA3 negatively regulates the stemness of breast cancer cells and EMT process. Our findings indicate that ITGA3 interacts with VASP and regulates its expression, and knockdown of ITGA3 inhibits the activity of the PI3K-AKT axis.

CONCLUSION

Our results show that ITGA3-VASP modulates breast cancer cell stemness, EMT and PI3K-AKT pathways. Therefore, ITGA3 might be a druggable target for clinical breast cancer management.

Hedgehog/GLI signaling in tumor immunity - new therapeutic opportunities and clinical implications

Uncontrolled activation of the Hedgehog/Glioma-associated oncogene (HH/GLI) pathway is a potent oncogenic driver signal promoting numerous cancer hallmarks such as proliferation, survival, angiogenesis, metastasis and metabolic rewiring. Several HH pathway inhibitors have already been approved for medical therapy of advanced and metastatic basal cell carcinoma and acute myeloid leukemia with partially impressive therapeutic activity. However, de novo and acquired resistance as well as severe side effects and unexplained lack of therapeutic efficacy are major challenges that urgently call for improved treatment options with more durable responses. The recent breakthroughs in cancer immunotherapy have changed our current understanding of targeted therapy and opened up promising therapeutic opportunities including combinations of selective cancer pathway and immune checkpoint inhibitors. Although HH/GLI signaling has been intensely studied with respect to the classical hallmarks of cancer, its role in the modulation of the anti-tumoral immune response has only become evident in recent studies. These have uncovered HH/GLI regulated immunosuppressive mechanisms such as enhanced regulatory T-cell formation and production of immunosuppressive cytokines. In light of these exciting novel data on oncogenic HH/GLI signaling in immune cross-talk and modulation, we summarize and connect in this review the existing knowledge from different HH-related cancers and chronic inflammatory diseases. This is to provide a basis for the investigation and evaluation of novel treatments combining immunotherapeutic strategies with approved as well as next-generation HH/GLI inhibitors. Further, we also critically discuss recent studies demonstrating a possible negative impact of current HH/GLI pathway inhibitors on the anti-tumoral immune response, which may explain some of the disappointing results of several oncological trials with anti-HH drugs.

Additional file 1

Identification of Targetable Pathways in Oral Cancer Patients via Random Forest and Chemical Informatics

Treatment of head and neck cancer has been slow to change with epidermal growth factor receptor (EGFR) inhibitors, PD1 inhibitors, and taxane-/plant-alkaloid-derived chemotherapies being the only therapies approved by the U.S. Food and Drug Administration (FDA) in the last 10 years for the treatment of head and neck cancers. Head and neck cancer is a relatively rare cancer compared to breast or lung cancers. However, it is possible that existing therapies for more common solid tumors or for the treatment of other diseases could also prove effective against oral cancers. Many therapies have molecular targets that could be appropriate in oral cancer as well as the cancer in which the drug gained initial FDA approval. Also, there may be targets in oral cancer for which existing FDA-approved drugs could be applied. This study describes informatics methods that use machine learning to identify influential gene targets in patients receiving platinum-based chemotherapy, non-platinum-based chemotherapy, and genes influential in both groups of patients. This analysis yielded 6 small molecules that had a high Tanimoto similarity (>50%) to ligands binding genes shown to be highly influential in determining treatment response in oral cancer patients. In addition to influencing treatment response, these genes were also found to act as gene hubs connected to more than 100 other genes in pathways enriched with genes determined to be influential in treatment response by a random forest classifier with 20 000 trees trying 320 variables at each tree node. This analysis validates the use of multiple informatics methods to identify small molecules that have a greater likelihood of efficacy in a given cancer of interest.

Hedgehog Signaling: An Achilles' Heel in Cancer

Hedgehog signaling pathway originally identified in the fruit fly Drosophila is an evolutionarily conserved signaling mechanism with crucial roles in embryogenesis, growth and patterning. It exerts its biological effect through a signaling mechanism that terminates at glioma-associated oncogene (GLI) transcription factors which alternate between activator and repressor forms and mediate various responses. The important components of the pathway include the hedgehog ligands (SHH), the Patched (PTCH) receptor, Smoothened (SMO), Suppressor of Fused (SuFu) and GLI transcription factors. Activating or inactivating mutations in key genes cause uncontrolled activation of the pathway in a ligand independent manner. The ligand-dependent aberrant activation of the hedgehog pathway causing overexpression of hedgehog pathway components and its target genes occurs in autocrine as well as paracrine fashion. In adults, aberrant activation of hedgehog signaling has been linked to birth defects and multiple solid cancers. In this review, we assimilate data from recent studies to understand the mechanism of functioning of the hedgehog signaling pathway, role in cancer, its association in various solid malignancies and the current strategies being used to target this pathway for cancer treatment.

Oncogenic Signaling in Tumorigenesis and Applications of siRNA Nanotherapeutics in Breast Cancer

Overexpression of oncogenes and cross-talks of the oncoproteins-regulated signaling cascades with other intracellular pathways in breast cancer could lead to massive abnormal signaling with the consequence of tumorigenesis. The ability to identify the genes having vital roles in cancer development would give a promising therapeutics strategy in combating the disease. Genetic manipulations through siRNAs targeting the complementary sequence of the oncogenic mRNA in breast cancer is one of the promising approaches that can be harnessed to develop more efficient treatments for breast cancer. In this review, we highlighted the effects of major signaling pathways stimulated by oncogene products on breast tumorigenesis and discussed the potential therapeutic strategies for targeted delivery of siRNAs with nanoparticles in suppressing the stimulated signaling pathways.

Smoothened-dependent and -independent pathways in mammalian noncanonical Hedgehog signaling

Hedgehog proteins are pivotal morphogens acting through a canonical pathway involving first activation of ligand binding to Patched followed by alleviation of Smoothened receptor inhibition, leading to activation of Gli transcription factors. Noncanonical Hedgehog signaling remains poorly characterized but is thought to be mainly dependent on Smoothened. However, Smoothened inhibitors have yielded only partial success in combating Hedgehog signal transduction-dependent cancer, suggesting that noncanonical Smoothened-independent pathways also are clinically relevant. Moreover, several Smoothened-dependent effects (e.g. neurite projection) do not require transcriptional activation, further suggesting biological importance of noncanonical Smoothened-dependent pathways. We comprehensively characterized the cellular kinome in Hedgehog-challenged murine WT and Smoothened^-/- fibroblasts as well as Smoothened agonist-stimulated cells. A peptide assay-based kinome analysis (in which cell lysates are used to phosphorylate specific kinase substrates), along with endocytosis, Lucifer Yellow-based, and immunoblotting assays, identified an elaborate signaling network of both Smoothened-dependent and -independent pathways that mediates actin reorganization through Src-like kinases, activates various proinflammatory signaling cascades, and concomitantly stimulates Wnt and Notch signaling while suppressing bone morphogenetic protein (BMP) signaling. The contribution of noncanonical Smoothened-independent signaling to the overall effects of Hedgehog on cellular physiology appears to be much larger than previously envisioned and may explain the transcriptionally independent effects of Hedgehog signaling on cytoskeleton. The observation that Patched-dependent, Smoothened-independent, noncanonical Hedgehog signaling increases Wnt/Notch signaling provides a possible explanation for the failure of Smoothened antagonists in combating Hedgehog-dependent but Smoothened inhibitor-resistant cancer. Our findings suggest that inhibiting Hedgehog-Patched interaction could result in more effective therapies as compared with conventional Smoothened-directed therapies.

Next-Generation Hedgehog/GLI Pathway Inhibitors for Cancer Therapy

The Hedgehog/Glioma-associated oncogene homolog (HH/GLI) signaling pathway regulates self-renewal of rare and highly malignant cancer stem cells (CSC), which have been shown to account for the initiation and maintenance of tumor growth as well as for drug resistance, metastatic spread and relapse. Efficacious therapeutic approaches targeting CSC pathways, such as HH/GLI signaling in combination with chemo, radiation or immunotherapy are, therefore, of high medical need. Pharmacological inhibition of HH/GLI pathway activity represents a promising approach to eliminate malignant CSC. Clinically approved HH/GLI pathway inhibitors target the essential pathway effector Smoothened (SMO) with striking therapeutic efficacy in skin and brain cancer patients. However, multiple genetic and molecular mechanisms resulting in de novo and acquired resistance to SMO inhibitors pose major limitations to anti-HH/GLI therapies and, thus, the eradication of CSC. In this review, we summarize reasons for clinical failure of SMO inhibitors, including mechanisms caused by genetic alterations in HH pathway effectors or triggered by additional oncogenic signals activating GLI transcription factors in a noncanonical manner. We then discuss emerging novel and rationale-based approaches to overcome SMO-inhibitor resistance, focusing on pharmacological perturbations of enzymatic modifiers of GLI activity and on compounds either directly targeting oncogenic GLI factors or interfering with synergistic crosstalk signals known to boost the oncogenicity of HH/GLI signaling.

M2 macrophage-derived IL6 mediates resistance of breast cancer cells to hedgehog inhibition

Hedgehog (Hh) pathway hyperactivation has been observed in various tumors, including breast cancer, and Hh pathway inhibitors have demonstrated antitumor activity in breast cancer. The tumor microenvironment (TME) has been shown to play an important role in modulating cancer cell drug sensitivity, but the TME response to Hh pathway inhibitors is unclear. In the current study, we observed increased TME infiltration of macrophages in breast cancer tissue, and specifically, M2 polarized macrophages after neoadjuvant chemotherapy. Furthermore, we observed an enhanced tolerance to Hh pathway inhibitors in MDA-MB-231 cells after co-culturing with M2 macrophages. In addition, we demonstrated that Hh pathway inhibition significantly induced IL6 expression, and validated that the tolerance to Hh pathway inhibitors was IL6-dependent. This study demonstrates a role of macrophages in Hh pathway inhibition resistance and a role of macrophage-derived IL6 in this resistance of breast cancer cells to Hh inhibition. These data indicate that antagonizing IL6 together with Hh pathway inhibitors may be a novel therapeutic strategy for breast cancer.

Abnormally elevated USP37 expression in breast cancer stem cells regulates stemness, epithelial-mesenchymal transition and cisplatin sensitivity

Background

Recent studies have indicated that deubiquitinating enzymes (DUBs) are related to the stem-cell pathway network and chemo-resistance in cancer. Ubiquitin-specific peptidase 37 (USP37), a novel DUB, was identified to be a potential factor associated with tumor progression. However, the biological functions of USP37 in breast cancer remain unclear.

Methods

The distribution of USP37 expression in breast cancer and the correlation between USP37 expression and the overall survival rate were detected by The Cancer Genome Atlas (TCGA) database. Gene set enrichment analysis (GSEA) was utilized to evaluate potential mechanism of USP37 in breast cancer. The USP37 expression in breast cancer tissues and breast cancer cell lines were detected by immunohistochemistry and western blotting. Sorting of breast cancer stem cells (BCSCs) were by using MACS assay. In vitro and in vivo assays were performed to examine the biological functions of USP37 in breast cancer cells. MG132, CHX chase, immunofluorescence staining and co-immunoprecipitation assays were used to test the interaction between USP37 and Gli-1.

Results

Bioinformatics analysis demonstrated that USP37 gene was elevated in breast cancer tissues and its overexpression was strongly correlated with the increased mortality rate. GSEA analysis showed that USP37 expression was positively associated with cell growth and metastasis while negatively related to cell apoptosis in the TCGA breast cancer samples. USP37 expression was elevated in breast cancer tissues and breast cancer cell lines. Moreover, we also detected that USP37 was overexpressed in BCSCs. USP37 regulated the ability of cell invasion, epithelial-mesenchymal transition (EMT), stemness and cisplatin sensitivity in breast cancer cell lines. Additionally, USP37 knockdown inhibited tumorigenicity and increased anticancer effect of cisplatin in vivo. Knockdown of USP37 significantly decreased hedgehog (Hh) pathway components Smo and Gli-1. Gli-1 was stabilized by USP37 and they interacted with each other. Further studies indicated that USP37 knockdown could inhibit the stemness, cell invasion and EMT in breast cancer via downregulation of Hh pathway.

Conclusions

These findings reveal that USP37 is highly expressed in BCSCs and is correlated with poor prognosis in breast cancer patients. USP37 can regulate the stemness, cell invasion and EMT via Hh pathway, and decreased USP37 confers sensitivity to cisplatin in breast cancer cells. USP37 is required for the regulation of breast cancer progression, as well as a critical target for clinical treatment of breast cancer.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0934-9) contains supplementary material, which is available to authorized users.

Hedgehog Signaling in Cancer: A Prospective Therapeutic Target for Eradicating Cancer Stem Cells

The Hedgehog (Hh) pathway is a signaling cascade that plays a crucial role in many fundamental processes, including embryonic development and tissue homeostasis. Moreover, emerging evidence has suggested that aberrant activation of Hh is associated with neoplastic transformations, malignant tumors, and drug resistance of a multitude of cancers. At the molecular level, it has been shown that Hh signaling drives the progression of cancers by regulating cancer cell proliferation, malignancy, metastasis, and the expansion of cancer stem cells (CSCs). Thus, a comprehensive understanding of Hh signaling during tumorigenesis and development of chemoresistance is necessary in order to identify potential therapeutic strategies to target various human cancers and their relapse. In this review, we discuss the molecular basis of the Hh signaling pathway and its abnormal activation in several types of human cancers. We also highlight the clinical development of Hh signaling inhibitors for cancer therapy as well as CSC-targeted therapy.

HER2-mediated GLI2 stabilization promotes anoikis resistance and metastasis of breast cancer cells

Breast cancer metastasis is a multi-step process and requires cells to overcome anoikis. Anoikis is defined as cell-death that occurs due to loss of cell adhesion. During the course of cancer progression, tumor cells acquire resistance to anoikis. However, mechanisms of anoikis resistance are not clear. Human epidermal growth receptor 2 (HER2) overexpressing breast tumors are known to be highly aggressive and metastatic. The mechanisms correlating HER2 with metastasis are poorly understood. We observed increased anoikis resistance in HER2 overexpressing breast cancer cells. In addition, we identified that HER2 overexpression was also associated with increased sonic hedgehog (SHH) signaling especially GLI2, and that inhibition of SHH pathway suppressed anoikis resistance. GSK3β is known to facilitate proteasome-mediated degradation of GLI2. Moreover, we observed that silencing of GLI2 resulted in reduced migration and invasion of HER2 overexpressing cells. Anoikis resistant HER2 overexpressing cells also showed increased rate and extent of metastasis in vivo, as compared to wild type anoikis resistant cells. Taken together, this study indicates a novel role of HER2/GSK3β/GLI2 axis in anoikis resistance and metastasis, and that GLI2 could be a potential target for anti-cancer therapies.

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.

Glioma-Associated Oncogene Homolog Inhibitors Have the Potential of Suppressing Cancer Stem Cells of Breast Cancer

Overexpression of Sonic Hedgehog signaling (Shh) pathway molecules is associated with invasiveness and recurrence in breast carcinoma. Therefore, inhibition of the Shh pathway downstream molecule Glioma-associated Oncogene Homolog (Gli) was investigated for its ability to reduce progression and invasiveness of patient-derived breast cancer cells and cell lines. Human primary breast cancer T2 cells with high expression of Shh signaling pathway molecules were compared with breast cancer line MDA-MB-231 cells. The therapeutic effects of Gli inhibitors were examined in terms of the cell proliferation, apoptosis, cancer stem cells, cell migration and gene expression. Blockade of the Shh signaling pathway could reduce cell proliferation and migration only in MDA-MB-231 cells. Hh pathway inhibitor-1 (HPI-1) increased the percentages of late apoptotic cells in MDA-MB-231 cells and early apoptotic cells in T2 cells. It reduced Bcl2 expression for cell proliferation and increased Bim expression for apoptosis. In addition, Gli inhibitor HPI-1 decreased significantly the percentages of cancer stem cells in T2 cells. HPI-1 worked more effectively than GANT-58 against breast carcinoma cells. In conclusion, HPI-1 could inhibit cell proliferation, reduce cell invasion and decrease cancer stem cell population in breast cancer cells. To target Gli-1 could be a potential strategy to suppress breast cancer stem cells.

Extracellular retention of a cyclopamine nanoformulation leveraging larger size and more negative charge for improved breast cancer treatment

We achieved greater extracellular retention of nanoparticles, by leveraging their larger size and negative charge, for improving the effects of a drug with extracellular targeting sites.

Risk Factors and Preventions of Breast Cancer

Breast cancer is the second leading cause of cancer deaths among women. The development of breast cancer is a multi-step process involving multiple cell types, and its prevention remains challenging in the world. Early diagnosis of breast cancer is one of the best approaches to prevent this disease. In some developed countries, the 5-year relative survival rate of breast cancer patients is above 80% due to early prevention. In the recent decade, great progress has been made in the understanding of breast cancer as well as in the development of preventative methods. The pathogenesis and tumor drug-resistant mechanisms are revealed by discovering breast cancer stem cells, and many genes are found related to breast cancer. Currently, people have more drug options for the chemoprevention of breast cancer, while biological prevention has been recently developed to improve patients' quality of life. In this review, we will summarize key studies of pathogenesis, related genes, risk factors and preventative methods on breast cancer over the past years. These findings represent a small step in the long fight against breast cancer.

Gli1-induced deubiquitinase USP48 aids glioblastoma tumorigenesis by stabilizing Gli1

Aberrant activation of the Hedgehog (Hh) signaling pathway drives the tumorigenesis of multiple cancers. In this study, we screened a panel of deubiquitinases that may regulate the Hh pathway. We find that deubiquitinase USP48 activates Gli-dependent transcription by stabilizing Gli1 protein. Mechanistically, USP48 interacts with Gli1 and cleaves its ubiquitin off directly. In glioblastoma cells, knockdown of USP48 inhibits cell proliferation and the expression of Gli1's downstream targets, which leads to repressed glioblastoma tumorigenesis. Importantly, USP48's effect on cell proliferation and tumorigenesis depends to some extent on Gli1. In addition, we find that the Sonic Hedgehog (SHH) pathway induces USP48 expression through Gli1-mediated transcriptional activation, which forms thus a positive feedback loop to regulate Hh signaling. In human glioblastoma specimens, the expression levels of USP48 and Gli1 proteins are clinically relevant, and high expression of USP48 correlates with glioma malignancy. In summary, our study reveals that the USP48-Gli1 regulatory axis is critical for glioma cell proliferation and glioblastoma tumorigenesis.

EMT cells increase breast cancer metastasis via paracrine GLI activation in neighbouring tumour cells

Recent fate-mapping studies concluded that EMT is not required for metastasis of carcinomas. Here we challenge this conclusion by showing that these studies failed to account for possible crosstalk between EMT and non-EMT cells that promotes dissemination of non-EMT cells. In breast cancer models, EMT cells induce increased metastasis of weakly metastatic, non-EMT tumour cells in a paracrine manner, in part by non-cell autonomous activation of the GLI transcription factor. Treatment with GANT61, a GLI1/2 inhibitor, but not with IPI 926, a Smoothened inhibitor, blocks this effect and inhibits growth in PDX models. In human breast tumours, the EMT-transcription factors strongly correlate with activated Hedgehog/GLI signalling but not with the Hh ligands. Our findings indicate that EMT contributes to metastasis via non-cell autonomous effects that activate the Hh pathway. Although all Hh inhibitors may act against tumours with canonical Hh/GLI signalling, only GLI inhibitors would act against non-canonical EMT-induced GLI activation.

Serum sonic hedgehog (SHH) and interleukin-(IL-6) as dual prognostic biomarkers in progressive metastatic breast cancer

Serum from one hundred and ten breast cancer patients and thirty healthy female volunteers, were prospectively collected and evaluated for serum levels of Shh and IL-6 using human Shh and IL-6 specific enzyme-linked immunoassays. All patients were regularly monitored for event free survival (EFS) and overall survival (OS). Overall outcome analysis was based on serum Shh and IL-6 levels. In patients with progressive metastatic BC, both serum Shh and IL-6 concentrations were elevated in 44% (29 of 65) and 63% (41 of 65) of patients, respectively, at a statistically significant level [Shh (p = 0.0001) and IL-6 (p = 0.0001)] compared to the low levels in healthy volunteers. Serum levels tended to increase with metastatic progression and lymph node positivity. High serum Shh and IL-6 levels were associated with poor EFS and OS opposite to the negative or lower levels in serum Shh and IL-6. The elevated levels of both serum Shh and IL-6 were mainly observed in BC patients who had a significantly higher risk of early recurrence and bone metastasis, and associated with a worse survival for patients with progressive metastatic BC. Further studies are warranted for validating these biomarkers as prognostic tools in a larger patient cohort and in a longer follow-up study.

Cancer Stem Cells Regulate Cancer-Associated Fibroblasts via Activation of Hedgehog Signaling in Mammary Gland Tumors

Many tumors display intracellular heterogeneity with subsets of cancer stem cells (CSC) that sustain tumor growth, recurrence, and therapy resistance. Cancer-associated fibroblasts (CAF) have been shown to support and regulate CSC function. Here, we investigate the interactions between CSCs and CAFs in mammary gland tumors driven by combined activation of Wnt/β-catenin and Hgf/Met signaling in mouse mammary epithelial cells. In this setting, CSCs secrete the Hedgehog ligand SHH, which regulate CAFs via paracrine activation of Hedgehog signaling. CAFs subsequently secrete factors that promote expansion and self-renewal of CSCs. In vivo treatment of tumors with the Hedgehog inhibitor vismodegib reduce CAF and CSC expansion, resulting in an overall delay of tumor formation. Our results identify a novel intracellular signaling module that synergistically regulates CAFs and CSCs. Targeting CAFs with Hedgehog inhibitors may offer a novel therapeutic strategy against breast cancer. Cancer Res; 77(8); 2134-47. ©2017 AACR.

In vitro and in vivo inhibition of breast cancer cell growth by targeting the Hedgehog/GLI pathway with SMO (GDC-0449) or GLI (GANT-61) inhibitors

Aberrant Hedgehog (Hh)/glioma-associated oncogene (GLI) signaling has been implicated in cancer progression. Here, we analyzed GLI1, Sonic Hedgehog (Shh) and NF-κB expression in 51 breast cancer (ductal carcinoma) tissues using immunohistochemistry. We found a positive correlation between nuclear GLI1 expression and tumor grade in ductal carcinoma cases. Cytoplasmic Shh staining significantly correlated with a lower tumor grade. Next, the in vitro effects of two Hh signaling pathway inhibitors on breast cancer cell lines were evaluated using the Smoothened (SMO) antagonist GDC-0449 and the direct GLI1 inhibitor GANT-61. GDC-0449 and GANT-61 exhibited the following effects: a) inhibited breast cancer cell survival; b) induced apoptosis; c) inhibited Hh pathway activity by decreasing the mRNA expression levels of GLI1 and Ptch and inhibiting the nuclear translocation of GLI1; d) increased/decreased EGFR and ErbB2 protein expression, reduced p21-Ras and ERK1/ERK2 MAPK activities and inhibited AKT activation; and e) decreased the nuclear translocation of NF-κB. However, GANT-61 exerted these effects more effectively than GDC-0449. The in vivo antitumor activities of GDC-0449 and GANT-61 were analyzed in BALB/c mice that were subcutaneously inoculated with mouse breast cancer (TUBO) cells. GDC-0449 and GANT-61 suppressed tumor growth of TUBO cells in BALB/c mice to different extents. These findings suggest that targeting the Hh pathway using antagonists that act downstream of SMO is a more efficient strategy than using antagonists that act upstream of SMO for interrupting Hh signaling in breast cancer.

Small molecule Hedgehog pathway antagonists

Leveraging our quinolone-1-(2H)-one based Hedgehog signalling pathway (HSP) inhibitors we have developed two new classes of HSP inhibitors based on: l-tryptophan and benzo[1,3]dioxol-5-ylmethyl-[2-(1H-indol-3-yl)-ethyl]-amine.

Sonic Hedgehog Signaling in Thyroid Cancer

Thyroid cancer is the most common malignancy of the endocrine system. The initiation of thyroid cancer is often triggered by a genetic mutation in the phosphortidylinositol-3 kinase (PI3K) or mitogen-activated protein kinase (MAPK) pathway, such as RAS and BRAF, or by the rearrangement of growth factor receptor tyrosine kinase genes such as RET/PTC. The sonic hedgehog (Shh) pathway is evolutionarily conserved and plays an important role in the embryonic development of normal tissues and organs. Gene mutations in the Shh pathway are involved in basal cell carcinomas (BCC). Activation of the Shh pathway due to overexpression of the genes encoding the components of this pathway stimulates the growth and spread of a wide range of cancer types. The Shh pathway also plays an important role in cancer stem cell (CSC) self-renewal. GDC-0449 and LDE-225, two inhibitors of this pathway, have been approved for treating BCC and are being tested as a single agent or in combination with other drugs for treating various other cancers. Here, we review the recent findings on activation of the Shh pathway in thyroid cancer and its role in maintaining thyroid CSC self-renewal. We also summarize the recent developments on crosstalk of the Shh pathway with the MAPK and PI3K oncogenic pathways, and its implications for combination therapy.

Down-regulation of the zinc-finger homeobox protein TSHZ2 releases GLI1 from the nuclear repressor complex to restore its transcriptional activity during mammary tumorigenesis

Although breast cancer is one of the most common malignancies, the molecular mechanisms underlying its development and progression are not fully understood. To identify key molecules involved, we screened publicly available microarray datasets for genes differentially expressed between breast cancers and normal mammary glands. We found that three of the genes predicted in this analysis were differentially expressed among human mammary tissues and cell lines. Of these genes, we focused on the role of the zinc-finger homeobox protein TSHZ2, which is down-regulated in breast cancer cells. We found that TSHZ2 is a nuclear protein harboring a bipartite nuclear localization signal, and we confirmed its function as a C-terminal binding protein (CtBP)-dependent transcriptional repressor. Through comprehensive screening, we identified TSHZ2-suppressing genes such as AEBP1 and CXCR4, which are conversely up-regulated by GLI1, the downstream transcription factor of Hedgehog signaling. We found that GLI1 forms a ternary complex with CtBP2 in the presence of TSHZ2 and that the transcriptional activity of GLI1 is suppressed by TSHZ2 in a CtBP-dependent manner. Indeed, knockdown of TSHZ2 increases the expression of AEBP1 and CXCR4 in TSHZ2-expressing immortalized mammary duct epithelium. Concordantly, immunohistochemical staining of mammary glands revealed that normal duct cells expresses GLI1 in the nucleus along with TSHZ2 and CtBP2, whereas invasive ductal carcinoma cells, which does not express TSHZ2, show the increase in the expression of AEBP1 and CXCR4 and in the cytoplasmic localization of GLI1. Thus, we propose that down-regulation of TSHZ2 is crucial for mammary tumorigenesis via the activation of GLI1.

SOX2 function and Hedgehog signaling pathway are co-conspirators in promoting androgen independent prostate cancer

Developmentally inclined hedgehog (HH) signaling pathway and pluripotency inducing transcription factor SOX2 have been known to work syngerstically during cellular reprogramming events to facilitate efficient differentiation. Hence, it is not surprising that both the factors are actively involved in arbitrating malignant growth, including prostate cancer progression. Here, we have described in details the potential mechanisms by which SOX2 effects neoplastic characteristics in prostate cancer and investigated the consequences of simultaneous down-regulation of SOX2 and HH pathway in androgen-independent human prostate cancer cells. Expression of SOX2 has been determined by qRT-PCR, western blot, immunohistochemistry and immunocytochemistry analyses; its functional role determined by gene knockdown using RNAi and over-expression via chemical activation in HaCaT, DU145 and PC-3 cells. Changes in level of cell proliferation, migration and apoptosis profiles were measured by MTT, FACS, chromatin condensation and scratch assays respectively. SOX2 was expressed in all the three cell lines and its inhibition reduced cell proliferation and induced apoptosis. Most importantly, when both SOX2 and HH pathway were targeted simultaneously, cell proliferation was greatly reduced, apoptotic cell population increased drastically and migration potential was reduced. Moreover, gene expression of EMT markers such as E-cadherin and apoptosis related Bcl-2 and Bax was also investigated wherein decrease in E-cadherin and Bcl-2 levels and increase in Bax expression further substantiating our claim. These findings could provide the basis for a novel therapeutic strategy targeting both the effector i.e. SOX2 and perpetuator i.e. HH pathway of aggressive tumorigenic properties in androgen independent prostate cancer.

Interleukin-30 Promotes Breast Cancer Growth and Progression

The inflammatory tissue microenvironment that promotes the development of breast cancer is not fully understood. Here we report a role for elevated IL30 in supporting the breast cancer cell viability and invasive migration. IL30 was absent in normal mammary ducts, ductules, and acini of histologically normal breast and scanty in the few stromal infiltrating leukocytes. In contrast, IL30 was expressed frequently in breast cancer specimens where it was associated with triple-negative and HER2⁺ molecular subtypes. In stromal leukocytes found in primary tumors or tumor-draining lymph nodes, which included mainly CD14⁺ monocytes, CD68⁺ macrophages, and CD33⁺/CD11b⁺ myeloid cells, IL30 levels increased with disease stage and correlated with recurrence. A negative correlation was determined between IL30 expression by nodal stromal leukocytes and overall survival. In vitro studies showed that human recombinant IL30 upregulated expression of a pro-oncogenic program, including especially IL6 in both triple-negative and HER2⁺ breast cancer cells. In triple-negative breast cancer cells, IL30 boosted a broader program of proliferation, invasive migration, and an inflammatory milieu associated with KISS1-dependent metastasis. Silencing of STAT1/STAT3 signaling hindered the regulation of the primary growth and progression factors in breast cancer cells. IL30 administration in vivo fostered the growth of triple-negative breast cancer by promoting proliferation and vascular dissemination of cancer cells and the accumulation of intratumoral CD11b⁺/Gr1⁺ myeloid cell infiltrates. Overall, our results show how IL30 regulates breast cancer cell viability, migration, and gene expression to promote breast cancer growth and progression and its impact on patient outcome. Cancer Res; 76(21); 6218-29. ©2016 AACR.

Tamoxifen Resistance: Emerging Molecular Targets

17β-Estradiol (E2) plays a pivotal role in the development and progression of breast cancer. As a result, blockade of the E2 signal through either tamoxifen (TAM) or aromatase inhibitors is an important therapeutic strategy to treat or prevent estrogen receptor (ER) positive breast cancer. However, resistance to TAM is the major obstacle in endocrine therapy. This resistance occurs either de novo or is acquired after an initial beneficial response. The underlying mechanisms for TAM resistance are probably multifactorial and remain largely unknown. Considering that breast cancer is a very heterogeneous disease and patients respond differently to treatment, the molecular analysis of TAM’s biological activity could provide the necessary framework to understand the complex effects of this drug in target cells. Moreover, this could explain, at least in part, the development of resistance and indicate an optimal therapeutic option. This review highlights the implications of TAM in breast cancer as well as the role of receptors/signal pathways recently suggested to be involved in the development of TAM resistance. G protein—coupled estrogen receptor, Androgen Receptor and Hedgehog signaling pathways are emerging as novel therapeutic targets and prognostic indicators for breast cancer, based on their ability to mediate estrogenic signaling in ERα-positive or -negative breast cancer.

Sulforaphene Interferes with Human Breast Cancer Cell Migration and Invasion through Inhibition of Hedgehog Signaling

Although inhibition of mammary tumorigenesis by isothiocyanates has been widely studied, little is known about the effects of sulforaphene on invasiveness of breast cancer. Here, sulforaphene significantly inhibited the migration and invasion of triple-negative SUM159 human breast cancer cells and suppressed the expression and activity of matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9). The Hedgehog (Hh) pathway, as an upstream signaling modulator, was significantly suppressed by sulforaphene. In particular, ciliary localization of Gli1 and its nuclear translocation were blocked by sulforaphene in a time-dependent manner. Consistently, downregulation of Hh signaling by vismodegib and Gli1 knockdown reduced the cellular migration and invasion as well as the expression of MMP-2 and MMP-9. These results indicate that the suppression of Hh/Gli1 signaling by sulforaphene may reduce the MMP-2 and MMP-9 activities and cellular invasiveness of human breast cancer cells, suggesting the potential efficacy of sulforaphene against breast cancer invasion and metastasis.