Cyclopamine inhibition of human breast cancer cell growth independent of Smoothened (Smo)

Interactions between hedgehog signaling pathway and the complex tumor microenvironment in breast cancer: current knowledge and therapeutic promises

Breast cancer ranks as one of the most common malignancies among women, with its prognosis and therapeutic efficacy heavily influenced by factors associated with the tumor cell biology, particularly the tumor microenvironment (TME). The diverse elements of the TME are engaged in dynamic bidirectional signaling interactions with various pathways, which together dictate the growth, invasiveness, and metastatic potential of breast cancer. The Hedgehog (Hh) signaling pathway, first identified in Drosophila, has been established as playing a critical role in human development and disease. Notably, the dysregulation of the Hh pathway is recognized as a major driver in the initiation, progression, and metastasis of breast cancer. Consequently, elucidating the mechanisms by which the Hh pathway interacts with the distinct components of the breast cancer TME is essential for comprehensively evaluating the link between Hh pathway activation and breast cancer risk. This understanding is also imperative for devising novel targeted therapeutic strategies and preventive measures against breast cancer. In this review, we delineate the current understanding of the impact of Hh pathway perturbations on the breast cancer TME, including the intricate and complex network of intersecting signaling cascades. Additionally, we focus on the therapeutic promise and clinical challenges of Hh pathway inhibitors that target the TME, providing insights into their potential clinical utility and the obstacles that must be overcome to harness their full therapeutic potential.

Therapeutic and pharmacological efficacy of plant-derived bioactive compounds in targeting breast cancer

Breast cancer (BC) ranks number one among cancers affecting women globally. Serious concerns include delayed diagnosis, poor prognosis, and adverse side effects of conventional treatment, leading to residual morbidity. Therefore, an alternative treatment approach that is safe and effective has become the need of the hour. In this regard, plant-based medicines via a combination of conventional drugs are gaining increasing acceptance worldwide, playing a pivotal role in cancer management as proven by their efficacy evaluation studies. This review aims to fill the knowledge gaps by providing the preclinical evidence of cellular and molecular mechanisms of Indian phytomedicines in targeting varied pathways of breast cancer progression. A comprehensive search was performed on different platforms, followed by screening of relevant studies for review. In this article, the in-depth of various botanical drugs covering their nomenclature, dosage, toxicity, and modus operandi in BC cells have been extensively discussed. Various signaling pathways like Notch signaling, MAPK signaling, apoptosis, Wnt signaling, etc. regulated by herbal medicine treatment in BC are also highlighted to understand the drug mechanism better. This will guide the researchers to plan future strategies and generate more robust integrated evidence of plant-based drugs or botanical formulations for their potential role in the management of BC.

Targeting breast cancer stem cells through retinoids: A new hope for treatment

Breast cancer is a complex and diverse disease accounting for nearly 30% of all cancers diagnosed in females. But unfortunately, patients develop resistance to the existing chemotherapeutic regimen, resulting in approximately 90% treatment failure. With over half a million deaths annually, it is imperative to explore new therapeutic approaches to combat the disease. Within a breast tumor, a small sub-population of heterogeneous cells, with a unique ability of self-renew and differentiation and responsible for tumor formation, initiation, and recurrence are referred to as breast cancer stem cells (BCSCs). These BCSCs have been identified as one of the main contributors to chemoresistance in breast cancer, making them an attractive target for developing novel therapeutic strategies. These cells exhibit surface biomarkers such as CD44+, CD24-/LOW, ALDH, CD133, and CD49f phenotypes. Higher expression of CD44+ and ALDH activity has been associated with the formation of tumors in various cancers. Moreover, the abnormal regulation of signaling pathways, including Hedgehog, Notch, β-catenin, JAK/STAT, and P13K/AKT/mTOR, leads to the formation of cancer stem cells, resulting in the development of tumors. The growing drug resistance in BC is a significant challenge, highlighting the need for new therapeutic strategies to combat this dreadful disease. Retinoids, a large group of synthetic derivatives of vitamin A, have been studied as chemopreventive agents in clinical trials and have been shown to regulate various crucial biological functions including vision, development, inflammation, and metabolism. On a cellular level, the retinoid activity has been well characterized and translated and is known to induce differentiation and apoptosis, which play important roles in the outcome of the transformation of tissues into malignant. Retinoids have been investigated extensively for their use in the treatment and prevention of cancer due to their high receptor-binding affinity to directly modulate gene expression programs. Therefore, in this study, we aim to summarize the current understanding of BCSCs, their biomarkers, and the associated signaling pathways. Retinoids, such as Adapalene, a third-generation retinoid, have shown promising anti-cancer potential and may serve as therapeutic agents to target BCSCs.

Veratrum parviflorum: An Underexplored Source for Bioactive Steroidal Alkaloids

Plants of the Veratrum genus have been used throughout history for their emetic properties, rheumatism, and for the treatment of high blood pressure. However, inadvertent consumption of these plants, which resemble wild ramps, induces life-threatening side effects attributable to an abundance of steroidal alkaloids. Several of the steroidal alkaloids from Veratrum spp. have been investigated for their ability to antagonize the Hedgehog (Hh) signaling pathway, a key pathway for embryonic development and cell proliferation. Uncontrolled activation of this pathway is linked to the development of various cancers; most notably, basal cell carcinoma and acute myeloid leukemia. Additional investigation of Veratrum spp. may lead to the identification of novel alkaloids with the potential to serve as chemotherapeutics. V. parviflorum is a relatively uncommon species of Veratrum that resides in the southeastern regions of North America. The phytochemical profile of this plant remains largely unexplored; however, bioactive steroidal alkaloids, including cyclopamine, veratramine, veratridine, and verazine were identified in its extract. The structural elucidation and bioactivity assessment of steroidal alkaloids in lesser abundance within the extract of V. parviflorum may yield potent Hh pathway inhibitors. This review seeks to consolidate the botanical and phytochemical information regarding V. parviflorum.

Dhh signaling pathway regulates reconstruction of seminiferous tubule-like structure

The reconstruction of a tubule-like structure in vitro has provided a promising system to analyze factors that drive morphogenesis and the underlying mechanisms. In this study, we took advantage of the inhibitor cyclopamine and a smoothened agonist to detect the role of the Dhh signaling pathway in the reconstructed tubule-like structure. Sertoli cells did not show polarity, rounded peritubular myoid cells and scattered Leydig cells were observed, combined with less laminin and lower proliferation of Leydig, peritubular myoid, germ, and Sertoli cells. However, in the presence of SAG, elongated peritubular myoid cells gathered at the bottom of polarized Sertoli cells, and most of the Leydig cells gathered at the outer part of the elongated peritubular myoid cells. Moreover, SAG promoted the secretion of laminin, assisting in the formation of the basal membrane and promoting the proliferation of Leydig, peritubular myoid, and germ cells. The level of Gli1 was significantly downregulated when treated with cyclopamine, whereas it was significantly upregulated when treated with SAG. These results indicate that the Dhh signaling pathway regulates the reconstruction of tubule-like structures by regulating the expression of Gli1.

Chemistry and bioactivities of natural steroidal alkaloids

Steroidal alkaloids possess the basic steroidal skeleton with a nitrogen atom in rings or side chains incorporated as an integral part of the molecule. They have demonstrated a wide range of biological activities, and some of them have even been developed as therapeutic drugs, such as abiraterone acetate (Zytiga^®), a blockbuster drug, which has been used for the treatment of prostate cancer. Structurally diverse natural steroidal alkaloids present a wide spectrum of biological activities, which are attractive for natural product chemistry and medicinal chemistry communities. This review comprehensively covers the structural classification, isolation and various biological activities of 697 natural steroidal alkaloids discovered from 1926 to October 2021, with 363 references being cited.

Review: Veratrum californicum Alkaloids

Veratrum spp. grow throughout the world and are especially prevalent in high mountain meadows of North America. All parts of Veratrum plants have been used for the treatment of ailments including injuries, hypertension, and rheumatic pain since as far back as the 1600s. Of the 17-45 Veratrum spp., Veratrum californicum alkaloids have been proven to possess favorable medicinal properties associated with inhibition of hedgehog (Hh) pathway signaling. Aberrant Hh signaling leads to proliferation of over 20 cancers, including basal cell carcinoma, prostate and colon among others. Six of the most well-studied V. californicum alkaloids are cyclopamine (1), veratramine (2), isorubijervine (3), muldamine (4), cycloposine (5), and veratrosine (6). Recent inspection of the ethanolic extract from V. californicum root and rhizome via liquid chromatography-mass spectrometry has detected up to five additional alkaloids that are proposed to be verazine (7), etioline (8), tetrahydrojervine (9), dihydrojervine (10), 22-keto-26-aminocholesterol (11). For each alkaloid identified or proposed in V. californicum, this review surveys literature precedents for extraction methods, isolation, identification, characterization and bioactivity to guide natural product drug discovery associated with this medicinal plant.

Gli activation by the estrogen receptor in breast cancer cells: Regulation of cancer cell growth by Gli3

BACKGROUND

Gli is an oncogenic transcription factor family thought to be involved in breast cancer (BrCa) cell growth. Gli activity is regulated by a post-translational proteolytic process that is suppressed by Hedgehog signaling. In prostate cancer cells, however, Gli activation is mediated by an interaction of active androgen receptor proteins with Gli3 that stabilizes Gli3 in its un-proteolyzed form. Here we show that the estrogen receptor (ER), ERα, also binds Gli3 and activates Gli in BrCa cells. Moreover, we show that ER + BrCa cells are dependent on Gli3 for cancer cell growth.

METHODS

Transfection with Gli-luciferase reporter was used to report Gli activity in 293FT or BrCa cells (MCF7, T47D, MDA-MB-453) with or without steroid ligands. Co-immunoprecipitation and proximity ligation were used to show association of Gli3 with ERα. Gli3 stability was determined by western blots of BrCa cell extracts. ERα knockdown or destabilization (by fulvestrant) was used to assess how loss of ERα affects estradiol-induced Gli reporter activity, formation of intranuclear ERα-Gli3 complexes and Gli3 stability. Expression of Gli1 and/or other endogenous Gli-target genes in BrCa cells were measured by qPCR in the presence or absence of estradiol. Gli3 knockdown was assessed for effects on BrCa cell growth using the Cyquant assay.

RESULTS

ERα co-transfection increased Gli reporter activity in 293FT cells that was further increased by estradiol. Gli3 co-precipitated in ERα immunoprecipitates. Acute (2 h) estradiol increased Gli reporter activity and the formation of intranuclear ERα-Gli3 complexes in ER + BrCa cells but more chronic estradiol (48 h) reduced ERα-Gli complexes commensurate with reduced ERα levels. Gli3 stability and endogenous activity was only increased by more chronic estradiol treatment. Fulvestrant or ERα knockdown suppressed E2-induction of Gli activity, intranuclear ERα-Gli3 complexes and stabilization of Gli3. Gli3 knockdown significantly reduced the growth of BrCa cells.

CONCLUSIONS

ERα interacts with Gli3 in BrCa cells and estradiol treatment leads to Gli3 stabilization and increased expression of Gli-target genes. Furthermore, we found tthat Gli3 is necessary for BrCa cell growth. These results support the idea that the ERα-Gli interaction and Gli3 may be novel targets for effective control of BrCa growth.

The Antiasthma Medication Ciclesonide Suppresses Breast Cancer Stem Cells through Inhibition of the Glucocorticoid Receptor Signaling-Dependent YAP Pathway

Ciclesonide is an FDA-approved glucocorticoid used to treat asthma and allergic rhinitis. However, whether it has anticancer and anti-cancer stem cell (CSC) effects is unknown. This study focused on investigating the effect of ciclesonide on breast cancer and CSCs and determining its underlying mechanism. Here, we showed that ciclesonide inhibits breast cancer and CSC formation. Similar glucocorticoids-dexamethasone and prednisone-did not inhibit CSC formation. Ciclesonide-induced glucocorticoid receptor (GR) degradation was dependent on ubiquitination. We showed via GR small interfering RNA (siRNA) that GR plays an important role in CSC formation. We showed via western blot and immunofluorescence assays that ciclesonide reduces the nuclear level of GR. The GR antagonist RU-486 also inhibited CSC formation. Ciclesonide reduced the protein level of the Hippo transducer Yes-associated protein (YAP). GR siRNA induced a decrease in YAP protein expression and inhibited mammosphere formation. The YAP inhibitor verteporfin inhibited CSC formation and transcription of the connective tissue growth factor and cysteine-rich protein 61 genes. The GR/YAP1 pathway regulated breast CSC formation. We showed that the GR/YAP signaling pathway regulates breast CSC formation and revealed a new approach for targeting GR and YAP to inhibit CSC formation.

Tumor microenvironment pathways: Cross regulation in breast cancer metastasis

The tumor microenvironment (TME) is heterogeneous and contains a multiple cell population with surrounded immune cells, which plays a major role in regulating metastasis. The multifunctional pathways, Hedgehog (Hh), Wnt, Notch, and NF-kB, cross-regulates metastasis in breast cancer. This review presents substantial evidence for cross-regulation of TME components and signaling pathways, which makes breast TME more heterogeneous and complex, promoting breast cancer progression and metastasis as a highly aggressive form. We discoursed the importance of stromal and immune cells as well as their crosstalk in bridging the metastasis. We also discussed the role of Hh and Notch pathways in the intervention between breast cancer cells and macrophages to support TME; Notch signaling in the bidirectional communication between cancer cells and components of TME; Wnt signal pathway in controlling the factors responsible for EMT and NF-κB pathway in the regulation of genes controlling the inflammatory response. We also present the role of exosomes and their miRNAs in the cross-regulation of TME cells as well as pathways in the reprogramming of breast TME to support metastasis. Finally, we examined and discussed the targeted small molecule inhibitors and natural compounds targeting developmental pathways and proposed small molecule natural compounds as potential therapeutics of TME based on the multitargeting ability. In conclusion, the understanding of the molecular basis of the cross-regulation of TME pathways and their inhibitors helps identify molecular targets for rational drug discovery to treat breast cancers.

A review on traditionally used South African medicinal plants, their secondary metabolites and their potential development into anticancer agents

ETHNOPHARMACOLOGICAL RELEVANCE

Approximately 70% of anticancer drugs were developed or derived from natural products or plants. Southern Africa boasts an enormous floral diversity with approximately 22,755 plant species with an estimated 3000 used as traditional medicines. In South Africa more than 27 million individuals rely on traditional medicine for healthcare. The use of South African plants for the treatment of cancer is poorly documented, however there is potential to develop anticancer agents from these plants. Limited ethnobotanical studies report the use of plants for cancer treatment in traditional medicine. Plants growing in tropical or subtropical regions, such as in South Africa, produce important secondary metabolites as a protective mechanism, which could be used to target various factors that play a key role in carcinogenesis.

AIMS

The aim was to collate information from primary ethnobotanical studies on South African plants traditionally used for the treatment of cancer. Evaluation of literature focused on traditionally used plants that have been tested for their in vitro activity against cancer cells. Secondary metabolites, previously identified within these plant species, were also included for discussion regarding their activity against cancer. The toxicity was evaluated to ascertain the therapeutic potential in further studies. Additionally, the aim was to highlight where a lack of reports were found regarding plant species with potential activity and to substantiate the need for further testing.

MATERIALS AND METHODS

A review of ethnobotanical surveys conducted in South Africa for plants used in the treatment of cancer was performed. Databases such as Science Direct, PubMed and Google Scholar, university repositories of master's dissertations and PhD theses, patents and books were used. Plant species showing significant to moderate activity were discussed regarding their toxicity. Compounds identified within these species were discussed for their activity against cancer cells and toxicity. Traditionally used plants which have not been scientifically validated for their activity against cancer were excluded.

RESULTS

Twenty plants were documented in ethnobotanical surveys as cancer treatments. Numerous scientific reports on the potential in vitro activity against cancer of these plants and the identification of secondary metabolites were found. Many of the secondary metabolites have not been tested for their activity against cancer cells or mode of action and should be considered for future studies. Lead candidates, such as the sutherlandiosides, sutherlandins, hypoxoside and pittoviridoside, were identified and should be further assessed. Toxicity studies should be included when testing plant extracts and/or secondary metabolites for their potential against cancer cells to give an indication of whether further analysis should be conducted.

CONCLUSION

There is a need to document plants used traditionally in South Africa for the treatment of cancer and to assess their safety and efficacy. Traditionally used plants have shown promising activity highlighting the importance of ethnobotanical studies and traditional knowledge. There are many opportunities to further assess these plants and secondary metabolites for their activity against cancer and their toxic effects. Pharmacokinetic studies are also not well documented within these plant extracts and should be included in studies when a lead candidate is identified.

GANT61 and Lithium Chloride Inhibit the Growth of Head and Neck Cancer Cell Lines Through the Regulation of GLI3 Processing by GSK3β

Several signaling pathways are aberrantly activated in head and neck squamous cell carcinoma (HNSCC), including the Hedgehog-Gli (HH-GLI), WNT, EGFR, and NOTCH pathways. The HH-GLI pathway has mostly been investigated in the context of canonical signal transduction and the inhibition of the membrane components of the pathway. In this work we investigated the role of downstream inhibitors GANT61 and lithium chloride (LiCl) on cell viability, wound closure, and colony forming ability of HNSCC cell lines. Five HNSCC cell lines were treated with HH-GLI pathway inhibitors affecting different levels of signal transduction. GANT61 and LiCl reduce the proliferation and colony formation capabilities of HNSCC cell lines, and LiCl has an additional effect on wound closure. The major effector of the HH-GLI signaling pathway in HNSCC is the GLI3 protein, which is expressed in its full-length form and is functionally regulated by GSK3β. LiCl treatment increases the inhibitory Ser9 phosphorylation of the GSK3β protein, leading to increased processing of GLI3 from full-length to repressor form, thus inhibiting HH-GLI pathway activity. Therefore, downstream inhibition of HH-GLI signaling may be a promising therapeutic strategy for HNSCC.

Pharmacophore-Based Virtual Screening for Identification of Negative Modulators of GLI1 as Potential Anticancer Agents

Starting from known GLI1 inhibitors, a pharmacophore-based virtual screening approach was applied to databases of commercially available compounds with the aim of identifying new GLI1 modulators. As a result, three different chemical scaffolds emerged that were characterized by a significant ability to reduce the transcriptional activity of the endogenous Hedgehog-GLI pathway and GLI1 protein level in murine NIH3T3 cells. They also showed a micromolar antiproliferative activity in human melanoma (A375) and medulloblastoma (DAOY) cell lines, without cytotoxicity in non-neoplastic mammary epithelial cells.

Cyclopamine functions as a suppressor of benign prostatic hyperplasia by inhibiting epithelial and stromal cell proliferation via suppression of the Hedgehog signaling pathway

Stromal-epithelial interaction serves a pivotal role in normal prostate growth, as well as the onset of benign prostatic hyperplasia (BPH). The present study aimed to explore the role of cyclopamine in the proliferation and apoptosis of epithelial and stromal cells in rats with BPH by blocking the Hedgehog signaling pathway. Cyclopamine (an inhibitor of the Hedgehog signaling pathway) was administered in a rat model of BPH, and the expression of Ki67 (proliferation factor) was determined by immunohistochemistry. In addition, epithelial and stromal cells were separated and cultured in order to investigate the role of cyclopamine in the progression of BPH. The expression of Hedgehog signaling pathway- and apoptosis-related genes, including basic fibroblastic growth factor (b-FGF) and transforming growth factor β (TGF-β), was evaluated using reverse transcription-quantitative polymerase chain reaction and western blot analysis. Cell proliferation, cell cycle and apoptosis were analyzed using an MTT assay and flow cytometry. We identified upregulated Ki67 expression and activated Hedgehog signaling pathway in rats with BPH. Cyclopamine inhibited the activation of the Hedgehog signaling pathway. In response to cyclopamine treatment, epithelial and stromal cell proliferation was inhibited; this was concomitant with decreased Ki67, TGF-β, and b-FGF expression. On the other hand, epithelial cell apoptosis was enhanced, which was associated with increased Bax and reduced Bcl-2 expression. Based on these findings, we proposed that cyclopamine may serve as a potential therapeutic agent in the treatment of BPH. Cyclopamine could inhibit epithelial and stromal cell proliferation, and induce epithelial cell apoptosis by suppressing the Hedgehog signaling pathway.

The FDA-Approved Anti-Asthma Medicine Ciclesonide Inhibits Lung Cancer Stem Cells through Hedgehog Signaling-Mediated SOX2 Regulation

Ciclesonide is an FDA-approved glucocorticoid (GC) used to treat asthma and allergic rhinitis. However, its effects on cancer and cancer stem cells (CSCs) are unknown. Our study focuses on investigating the inhibitory effect of ciclesonide on lung cancer and CSCs and its underlying mechanism. In this study, we showed that ciclesonide inhibits the proliferation of lung cancer cells and the growth of CSCs. Similar glucocorticoids, such as dexamethasone and prednisone, do not inhibit CSC formation. We show that ciclesonide is important for CSC formation through the Hedgehog signaling pathway. Ciclesonide reduces the protein levels of GL1, GL2, and Smoothened (SMO), and a small interfering RNA (siRNA) targeting SMO inhibits tumorsphere formation. Additionally, ciclesonide reduces the transcript and protein levels of SOX2, and an siRNA targeting SOX2 inhibits tumorsphere formation. To regulate breast CSC formation, ciclesonide regulates GL1, GL2, SMO, and SOX2. Our results unveil a novel mechanism involving Hedgehog signaling and SOX2 regulated by ciclesonide in lung CSCs, and also open up the possibility of targeting Hedgehog signaling and SOX2 to prevent lung CSC formation.

Mesenchymal Cells Support the Oncogenicity and Therapeutic Response of the Hedgehog Pathway in Triple-Negative Breast Cancer

The paracrine interaction between tumor cells and adjacent stroma has been associated with the oncogenic activity of the Hedgehog (Hh) pathway in triple-negative breast tumors. The present study developed a model of paracrine Hh signaling and examined the impact of mesenchymal cell sources and culture modalities in the oncogenicity of the Hh pathway in breast tumor cells. Studies consisted of tumor cell monocultures and co-cultures with cancer-associated and normal fibroblasts, tumor cells that undergo epithelial–mesenchymal transition (EMT), or adipose-derived mesenchymal stem cells (ADMSCs). Hh ligand and pathway inhibitors, GANT61 and NVP-LDE225 (NVP), were evaluated in both cell cultures and a mouse xenograft model. Results in monocultures show that tumor cell viability and Hh transcriptional activity were not affected by Hh inhibitors. In co-cultures, down-regulation of GLI1, SMO, and PTCH1 in the stroma correlated with reduced tumor growth rates in xenografted tumors and cell cultures, confirming a paracrine interaction. Fibroblasts and EMT cells supported Hh transcriptional activity and enhanced tumor cell growth. Mixed and adjacent culture modalities indicate that tumor growth is supported via fibroblast-secreted soluble factors, whereas enriched tumor stemness requires close proximity between tumor and fibroblasts. Overall this study provides a tumor–mesenchymal model of Hh signaling and highlights the therapeutic value of mesenchymal cells in the oncogenic activity of the Hh pathway.

Therapeutic value of steroidal alkaloids in cancer: Current trends and future perspectives

Discovery and development of new potentially selective anticancer agents are necessary to prevent a global cancer health crisis. Currently, alternative medicinal agents derived from plants have been extensively investigated to develop anticancer drugs with fewer adverse effects. Among them, steroidal alkaloids are conventional secondary metabolites that comprise an important class of natural products found in plants, marine organisms and invertebrates, and constitute a judicious choice as potential anti-cancer leads. Traditional medicine and modern science have shown that representatives from this compound group possess potential antimicrobial, analgesic, anticancer and anti-inflammatory effects. Therefore, systematic and recapitulated information about the bioactivity of these compounds, with special emphasis on the molecular or cellular mechanisms, is of high interest. In this review, we methodically discuss the in vitro and in vivo potential of the anticancer activity of natural steroidal alkaloids and their synthetic and semi-synthetic derivatives. This review focuses on cumulative and comprehensive molecular mechanisms, which will help researchers understand the molecular pathways involving steroid alkaloids to generate a selective and safe new lead compound with improved therapeutic applications for cancer prevention and therapy. In vitro and in vivo studies provide evidence about the promising therapeutic potential of steroidal alkaloids in various cancer cell lines, but advanced pharmacokinetic and clinical experiments are required to develop more selective and safe drugs for cancer treatment.

Role of Hedgehog Signaling in Breast Cancer: Pathogenesis and Therapeutics

Breast cancer (BC) is the leading cause of cancer-related mortality in women, only followed by lung cancer. Given the importance of BC in public health, it is essential to identify biomarkers to predict prognosis, predetermine drug resistance and provide treatment guidelines that include personalized targeted therapies. The Hedgehog (Hh) signaling pathway plays an essential role in embryonic development, tissue regeneration, and stem cell renewal. Several lines of evidence endorse the important role of canonical and non-canonical Hh signaling in BC. In this comprehensive review we discuss the role of Hh signaling in breast development and homeostasis and its contribution to tumorigenesis and progression of different subtypes of BC. We also examine the efficacy of agents targeting different components of the Hh pathway both in preclinical models and in clinical trials. The contribution of the Hh pathway in BC tumorigenesis and progression, its prognostic role, and its value as a therapeutic target vary according to the molecular, clinical, and histopathological characteristics of the BC patients. The evidence presented here highlights the relevance of the Hh signaling in BC, and suggest that this pathway is key for BC progression and metastasis.

Breast cancer stem cells and the challenges of eradication: a review of novel therapies

Breast cancer is a heterogeneous disease that accounts for 30% of all cancers diagnosed in women and over half a million deaths per year. Cancer stem cells (CSCs) make up a small subpopulation of cells within a tumor, are capable of self-renewal and, are responsible for tumor initiation, formation, and recurrence. Breast CSCs (BCSCs) have been the subject of concentrated research as potential targets for breast cancer therapies. Cell surface markers CD44+/CD24- have been established as minimum biomarkers for BCSCs and the upregulation of CD44 expression has been linked to tumor formation in numerous cancers. Additionally, the deregulation of Notch, Wnt/Frizzled/β-catenin, Hippo, and Hedgehog signaling pathways is believed to be responsible for the formation of CSCs and lead to tumor formation. Tumor heterogeneity is a key feature of therapy resistance and a major challenge. CSCs are predominantly senescent and inherently immune to chemotherapy drugs which rely on an overactive cell cycle. Current therapeutic strategies include targeting CSC signaling pathways that play critical roles in self-renewal and defense. Anti-CD44 antibodies have been shown to induce terminal differentiation in CSCs resulting in a significant decrease in tumor metastasis. Additionally, targeting the tumor microenvironment has been shown to increase the effectiveness of chemotherapy drugs. In this review, we attempt to provide an overview of breast cancer, the stem of its cause, and novel therapies currently being explored.

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.

Invasion-Related Factors as Potential Diagnostic and Therapeutic Targets in Oral Squamous Cell Carcinoma-A Review

It is well recognized that the presence of cervical lymph node metastasis is the most important prognostic factor in oral squamous cell carcinoma (OSCC). In solid epithelial cancer, the first step during the process of metastasis is the invasion of cancer cells into the underlying stroma, breaching the basement membrane (BM)—the natural barrier between epithelium and the underlying extracellular matrix (ECM). The ability to invade and metastasize is a key hallmark of cancer progression, and the most complicated and least understood. These topics continue to be very active fields of cancer research. A number of processes, factors, and signaling pathways are involved in regulating invasion and metastasis. However, appropriate clinical trials for anti-cancer drugs targeting the invasion of OSCC are incomplete. In this review, we summarize the recent progress on invasion-related factors and emerging molecular determinants which can be used as potential for diagnostic and therapeutic targets in OSCC.

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.

Characterization of MCF-12A cell phenotype, response to estrogens, and growth in 3D

Background

Three-dimensional cultures of mammary epithelial cells allow for biologically-relevant studies of the development of the mammary gland in rodents and humans under normal and pathological conditions, like carcinogenesis. Under these conditions, mammotropic hormones play significant roles in tissue morphogenesis. Therefore, a system that recreates the normal, hormonally responsive epithelium would be a valuable tool to study the normal state and its transition to carcinogenesis. MCF-12A cells have been claimed to be non-tumorigenic mammary epithelial cells with reported sensitivity to estrogens. In this study, we aimed at characterizing MCF-12A cells for use in a hormone-responsive 3D culture system to determine their usefulness as a tool to identify normal and abnormal microenvironmental cues.

Methods

MCF-12A cells were single-cell cloned in order to investigate their heterogeneous makeup. The parental cells were then treated with estradiol to investigate proliferative and transcriptional responses through the estrogen receptor alpha. Finally, parental cells and epithelial-like cell-derived clones were seeded in rat-tail collagen I to profile the morphogenesis of multicellular 3D structures. The resultant structures were then analyzed using unsupervised morphometric analysis.

Results

MCF-12A cells consist of epithelial-like colonies which shed elongated, freely growing cells on the colony's edges. The cells express E-cadherin as well as mesenchymal vimentin but do not express markers associated with myoepithelial cells or fibroblasts. Treatment with estradiol does not affect either the proliferation rate or the induction of gene expression in MCF-12A cells. Parental MCF-12A cells form acini, solid spheres and elongated branching ducts when grown in rat-tail collagen type I matrix, the geometries and distribution of which are altered following the removal of fibroblast-like cells.

Conclusions

MCF-12A cells are a heterogeneous pseudo-epithelial cell line capable of forming a variety of multicellular structures in 3D culture. We found no indication that the cells display estrogen-responsive characteristics, thus refuting previous studies which reported estrogen responsiveness. We report that MCF-12A cells are not suited for use in studies in which differential behaviors of "normal" and "cancerous" estrogen-responsive cells are to be compared.

Antimitotic activity of DY131 and the estrogen-related receptor beta 2 (ERRβ2) splice variant in breast cancer

Breast cancer remains a leading cause of cancer-related death in women, and triple negative breast cancer (TNBC) lacks clinically actionable therapeutic targets. Death in mitosis is a tumor suppressive mechanism that occurs in cancer cells experiencing a defective M phase. The orphan estrogen-related receptor beta (ERRβ) is a key reprogramming factor in murine embryonic and induced pluripotent stem cells. In primates, ERRβ is alternatively spliced to produce several receptor isoforms. In cellular models of glioblastoma, short form (ERRβsf) and beta2 (ERRβ2) splice variants differentially regulate cell cycle progression in response to the synthetic agonist DY131, with ERRβ2 driving arrest in G2/M.The goals of the present study are to determine the cellular function(s) of ligand-activated ERRβ splice variants in breast cancer and evaluate the potential of DY131 to serve as an antimitotic agent, particularly in TNBC. DY131 inhibits growth in a diverse panel of breast cancer cell lines, causing cell death that involves the p38 stress kinase pathway and a bimodal cell cycle arrest. ERRβ2 facilitates the block in G2/M, and DY131 delays progression from prophase to anaphase. Finally, ERRβ2 localizes to centrosomes and DY131 causes mitotic spindle defects. Targeting ERRβ2 may therefore be a promising therapeutic strategy in breast cancer.

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.

Pharmacological targeting of GLI1 inhibits proliferation, tumor emboli formation and in vivo tumor growth of inflammatory breast cancer cells

Activation of the Hedgehog (Hh) pathway effector GLI1 is linked to tumorigenesis and invasiveness in a number of cancers, with targeting of GLI1 by small molecule antagonists shown to be effective. We profiled a collection of GLI antagonists possessing distinct mechanisms of action for efficacy in phenotypic models of inflammatory and non-inflammatory breast cancer (IBC and non-IBC) that we showed expressed varying levels of Hh pathway mediators. Compounds GANT61, HPI-1, and JK184 decreased cell proliferation, inhibited GLI1 mRNA expression and decreased the number of colonies formed in TN-IBC (SUM149) and TNBC (MDA-MB-231 and SUM159) cell lines. In addition, GANT61 and JK184 significantly down-regulated GLI1 targets that regulate cell cycle (cyclin D and E) and apoptosis (Bcl2). GANT61 reduced SUM149 spheroid growth and emboli formation, and in orthotopic SUM149 tumor models significantly decreased tumor growth. We successfully utilized phenotypic profiling to identify a subset of GLI1 antagonists that were prioritized for testing in in vivo models. Our results indicated that GLI1 activation in TN-IBC as in TNBC, plays a vital role in promoting cell proliferation, motility, tumor growth, and formation of tumor emboli.

Shh promotes direct interactions between epidermal cells and osteoblast progenitors to shape regenerated zebrafish bone

Zebrafish innately regenerate amputated fins by mechanisms that expand and precisely position injury-induced progenitor cells to re-form tissue of the original size and pattern. For example, cell signaling networks direct osteoblast progenitors (pObs) to rebuild thin cylindrical bony rays with a stereotypical branched morphology. Hedgehog/Smoothened (Hh/Smo) signaling has been variably proposed to stimulate overall fin regenerative outgrowth or promote ray branching. Using a photoconvertible patched2 reporter, we resolve active Hh/Smo output to a narrow distal regenerate zone comprising pObs and adjacent motile basal epidermal cells. This Hh/Smo activity is driven by epidermal Sonic hedgehog a (Shha) rather than Ob-derived Indian hedgehog a (Ihha), which nevertheless functions atypically to support bone maturation. Using BMS-833923, a uniquely effective Smo inhibitor, and high-resolution imaging, we show that Shha/Smo is functionally dedicated to ray branching during fin regeneration. Hh/Smo activation enables transiently divided clusters of Shha-expressing epidermis to escort pObs into similarly split groups. This co-movement likely depends on epidermal cellular protrusions that directly contact pObs only where an otherwise occluding basement membrane remains incompletely assembled. Progressively separated pObs pools then continue regenerating independently to collectively re-form a now branched skeletal structure.

Hedgehog Signaling: From Basic Biology to Cancer Therapy

The Hedgehog (HH) signaling pathway was discovered originally as a key pathway in embryonic patterning and development. Since its discovery, it has become increasingly clear that the HH pathway also plays important roles in a multitude of cancers. Therefore, HH signaling has emerged as a therapeutic target of interest for cancer therapy. In this review, we provide a brief overview of HH signaling and the key molecular players involved and offer an up-to-date summary of our current knowledge of endogenous and exogenous small molecules that modulate HH signaling. We discuss experiences and lessons learned from the decades-long efforts toward the development of cancer therapies targeting the HH pathway. Challenges to develop next-generation cancer therapies are highlighted.

Hedgehog pathway activation in T-cell acute lymphoblastic leukemia predicts response to SMO and GLI1 inhibitors

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive childhood leukemia that is caused by the accumulation of multiple genomic lesions resulting in transcriptional deregulation and increased cell proliferation and survival. Through analysis of gene expression data, we provide evidence that the hedgehog pathway is activated in 20% of T-ALL samples. Hedgehog pathway activation is associated with ectopic expression of the hedgehog ligands Sonic hedgehog (SHH) or Indian hedgehog (IHH), and with upregulation of the transcription factor GLI1 Ectopic expression of SHH or IHH in mouse T cells in vivo caused hedgehog pathway activation in both lymphoid and epithelial cells in the thymus and resulted in increased expression of important T-cell stimulatory ligands (Dll4, Il7, and Vegf) by thymic epithelial cells. In T-ALL cell lines, pharmacological inhibition or short interfering RNA-mediated knockdown of SMO or GLI1 led to decreased cell proliferation. Moreover, primary T-ALL cases with high GLI1 messenger RNA levels, but not those with low or undetectable GLI1 expression, were sensitive to hedgehog pathway inhibition by GANT61 or GDC-0449 (vismodegib) using ex vivo cultures and in vivo xenograft models. We identify the hedgehog pathway as a novel therapeutic target in T-ALL and demonstrate that hedgehog inhibitors approved by the US Food and Drug Administration could be used for the treatment of this rare leukemia.

Targeting cancer stem cells and signaling pathways by phytochemicals: Novel approach for breast cancer therapy

Breast cancer is the most common form of cancer diagnosed in women worldwide and the second leading cause of cancer-related deaths in the USA. Despite the development of newer diagnostic methods, selective as well as targeted chemotherapies and their combinations, surgery, hormonal therapy, radiotherapy, breast cancer recurrence, metastasis and drug resistance are still the major problems for breast cancer. Emerging evidence suggest the existence of cancer stem cells (CSCs), a population of cells with the capacity to self-renew, differentiate and be capable of initiating and sustaining tumor growth. In addition, CSCs are believed to be responsible for cancer recurrence, anticancer drug resistance, and metastasis. Hence, compounds targeting breast CSCs may be better therapeutic agents for treating breast cancer and control recurrence and metastasis. Naturally occurring compounds, mainly phytochemicals have gained immense attention in recent times because of their wide safety profile, ability to target heterogeneous populations of cancer cells as well as CSCs, and their key signaling pathways. Therefore, in the present review article, we summarize our current understanding of breast CSCs and their signaling pathways, and the phytochemicals that affect these cells including curcumin, resveratrol, tea polyphenols (epigallocatechin-3-gallate, epigallocatechin), sulforaphane, genistein, indole-3-carbinol, 3, 3'-di-indolylmethane, vitamin E, retinoic acid, quercetin, parthenolide, triptolide, 6-shogaol, pterostilbene, isoliquiritigenin, celastrol, and koenimbin. These phytochemicals may serve as novel therapeutic agents for breast cancer treatment and future leads for drug development.

The Potential Role of Hedgehog Signaling in the Luminal/Basal Phenotype of Breast Epithelia and in Breast Cancer Invasion and Metastasis

The epithelium of the lactiferous ducts in the breast is comprised of luminal epithelial cells and underlying basal myoepithelial cells. The regulation of cell fate and transit of cells between these two cell types remains poorly understood. This relationship becomes of greater importance when studying the subtypes of epithelial breast carcinoma, which are categorized according to their expression of luminal or basal markers. The epithelial mesenchymal transition (EMT) is a pivotal event in tumor invasion. It is important to understand mechanisms that regulate this process, which bears relation to the normal dynamic of epithelial/basal phenotype regulation in the mammary gland. Understanding this process could provide answers for the regulation of EMT in breast cancer, and thereby identify potential targets for therapy. Evidence points towards a role for hedgehog signaling in breast tissue homeostasis and also in mammary neoplasia. This review examines our current understanding of role of the hedgehog-signaling (Hh) pathway in breast epithelial cells both during breast development and homeostasis and to assess the potential misappropriation of Hh signals in breast neoplasia, cancer stem cells and tumor metastasis via EMT.

Isocyclopamine, a novel synthetic derivative of cyclopamine, reverts doxorubicin resistance in MCF-7/ADR cells by increasing intracellular doxorubicin accumulation and downregulating breast cancer stem-like cells

Cyclopamine (CPM) showed promise as a human cancer chemotherapy agent. However, limitations such as stomach acid instability and low solubility impair its clinical application. In this study, we synthesized a novel CPM analogue, isocyclopamine (ICPM), which had comparative bioactivity with CPM and improved stability and solubility. ICPM reversed doxorubicin resistance and had potent synergy with doxorubicin in MCF-7/ADR cells. We further demonstrated that the synergistic mechanism was related to the increased intracellular accumulation of doxorubicin in the cells and the downregulation of the cancer stem-like cells via modulation on both ABCB1 and ABCG2 transporters with independence of Smoothened. The present study identified ICPM as a novel derivative of CPM with better stability and solubility, which provided a useful tool for the biological and medicinal studies, as well as a novel agent for the development of new cancer chemotherapy with improved efficacy.

A new role for the PI3K/Akt signaling pathway in the epithelial-mesenchymal transition

Tumor metastasis is not only a sign of disease severity but also a major factor causing treatment failure and cancer-related death. Therefore, studies on the molecular mechanisms of tumor metastasis are critical for the development of treatments and for the improvement of survival. The epithelial-mesenchymal transition (EMT) is an orderly, polygenic biological process that plays an important role in tumor cell invasion, metastasis and chemoresistance. The complex, multi-step process of EMT involves multiple regulatory mechanisms. Specifically, the PI3K/Akt signaling pathway can affect the EMT in a variety of ways to influence tumor aggressiveness. A better understanding of the regulatory mechanisms related to the EMT can provide a theoretical basis for the early prediction of tumor progression as well as targeted therapy.

Effect of Rab23 on the proliferation and apoptosis in breast cancer

Rab23, as a negative regulatory molecule of the Hedgehog (Hh) signaling pathway, may be a new target for treating carcinoma. In the present study, we aimed to determine whether Rab23 is expressed in breast cancer cells and whether Rab23 affects the viability and proliferation of breast cancer cells. We evaluated Rab23 expression in several breast cancer cell lines including MDA-MB-231, Bcap37 and MCF-7 by reverse transcription-PCR (RT-PCR), western blotting and immunofluorescence in vitro. We assessed cell growth and proliferation by 3-(4,5-dimethylthiazol‑2-y1)‑3,5-diphenyltetrazolium bromide (MTT), colony formation and bromodeoxyuridine (BrdU) incorporation assays. The distribution of the cell cycle and the rate of apoptosis were assessed using flow cytometry (FCM). In addition, we determined the mechanisms by which Rab23 regulates the Hh pathway by detecting the level of Gli molecules by RT-PCR. We found that Rab23 mRNA and protein levels were expressed in breast cancer cells, and the expression of Rab23 in MDA-MB-231 cells was higher than that in the MCF-7 cells. Rab23 protein was primarily expressed and localized in the cytoplasm surrounding the nucleus. The MTT assay showed that the absorbance value at A(490 nm) of the Rab23‑transfected group was reduced in comparison with the control group. The number of colonies formed in the breast cancer cells was significantly reduced and BrdU labeling was weakened in the group transfected with Rab23. The results of FCM showed that overexpression of Rab23 protein caused cell cycle arrest in the G1 phase and a decrease in the S phase population as well as induction of apoptosis. Furthermore, Rab23 decreased Gli1 and Gli2 mRNA levels when compared with the control group. Our results indicate that Rab23 is expressed in breast cancer cells, and ectopic expression of Rab23 inhibits the growth and proliferation as well as induces cell apoptosis in breast cancer cells. These effects may be due to the inhibition by Rab23 of Gli1 and Gli2 mRNA expression. These results suggest that Rab23 is a potential target for the treatment of breast cancer.

The presence of primary cilia in cancer cells does not predict responsiveness to modulation of smoothened activity

Primary cilia are microtubule-based organelles that regulate smoothened-dependent activation of the GLI transcription factors in canonical hedgehog signaling. In many cancers, primary cilia are markedly decreased or absent. The lack of primary cilia may inhibit or alter canonical hedgehog signaling and, thereby, interfere in the cellular responsiveness to modulators of smoothened activity. Clinical trials of smoothened antagonists for cancer treatment have shown the best response in basal cell carcinomas, with limited response in other solid tumors. To determine whether the presence or absence of primary cilia in cancer cells will predict their responsiveness to modulation of smoothened activity, we compared the ability of an agonist and/or inhibitor of smoothened (SAG and SANT1, respectively) to modulate GLI-mediated transcription, as measured by GLI1 mRNA level or GLI-luciferase reporter activity, in non-cancer cells with primary cilia (ovarian surface epithelial cells and breast fibroblasts), in cancer cells that cannot assemble primary cilia (MCF7, MDA-MB-231 cell lines), and in cancer cells with primary cilia (SKOV3, PANC1 cell lines). As expected, SAG and SANT1 resulted in appropriate modulation of GLI transcriptional activity in ciliated non-cancer cells, and failed to modulate GLI transcriptional activity in cancer cells without primary cilia. However, there was also no modulation of GLI transcriptional activity in either ciliated cancer cell line. SAG treatment of SKOV3 induced localization of smoothened to primary cilia, as assessed by immunofluorescence, even though there was no increase in GLI transcriptional activity, suggesting a defect in activation of SMO in the primary cilia or in steps later in the hedgehog pathway. In contrast to SKOV3, SAG treatment of PANC1 did not cause the localization of smoothened to primary cilia. Our data demonstrate that the presence of primary cilia in the cancer epithelial cells lines tested does not indicate their responsiveness to smoothened activation or inhibition.

Hedgehog Acyltransferase as a target in estrogen receptor positive, HER2 amplified, and tamoxifen resistant breast cancer cells

Background

Hedgehog acyltransferase (Hhat) catalyzes the transfer of the fatty acid palmitate onto Sonic Hedgehog (Shh), a modification that is essential for Shh signaling activity. The Shh signaling pathway has been implicated in the progression of breast cancer.

Methods

To determine the functional significance of Hhat expression in breast cancer, we used a panel of breast cancer cell lines that included estrogen receptor (ER) positive, HER2 amplified, triple negative, and tamoxifen resistant cells. We monitored both anchorage dependent and independent proliferation of these cells following depletion of Hhat with lentiviral shRNA and inhibition of Hhat activity with RU-SKI 43, a small molecule inhibitor of Hhat.

Results

Depletion of Hhat decreased anchorage-dependent and anchorage-independent proliferation of ER positive, but not triple negative, breast cancer cells. Treatment with RU-SKI 43 also reduced ER positive cell proliferation, whereas a structurally related, inactive compound had no effect. Overexpression of Hhat in ER positive cells not only rescued the growth defect in the presence of RU-SKI 43 but also resulted in increased cell proliferation in the absence of drug. Furthermore, depletion or inhibition of Hhat reduced proliferation of HER2 amplified as well as tamoxifen resistant cells. Inhibition of Smoothened had no effect on proliferation, indicating that canonical Shh signaling was not operative. Moreover, Hhat regulated the proliferation of both Shh responsive and non-responsive ER positive cells, suggesting a Shh independent function for Hhat.

Conclusions

These data suggest that Hhat plays a critical role in ER positive, HER2 amplified, and hormone resistant breast cancer proliferation and highlights the potential promise of Hhat inhibitors for therapeutic benefit in breast cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0345-x) contains supplementary material, which is available to authorized users.

Therapeutic Potential of Steroidal Alkaloids in Cancer and Other Diseases

Steroidal alkaloids are a class of secondary metabolites isolated from plants, amphibians, and marine invertebrates. Evidence accumulated in the recent two decades demonstrates that steroidal alkaloids have a wide range of bioactivities including anticancer, antimicrobial, anti-inflammatory, antinociceptive, etc., suggesting their great potential for application. It is therefore necessary to comprehensively summarize the bioactivities, especially anticancer activities and mechanisms of steroidal alkaloids. Here we systematically highlight the anticancer profiles both in vitro and in vivo of steroidal alkaloids such as dendrogenin, solanidine, solasodine, tomatidine, cyclopamine, and their derivatives. Furthermore, other bioactivities of steroidal alkaloids are also discussed. The integrated molecular mechanisms in this review can increase our understanding on the utilization of steroidal alkaloids and contribute to the development of new drug candidates. Although the therapeutic potentials of steroidal alkaloids look promising in the preclinical and clinical studies, further pharmacokinetic and clinical studies are mandated to define their efficacy and safety in cancer and other diseases.

Combination of cyclopamine and tamoxifen promotes survival and migration of mcf-7 breast cancer cells--interaction of hedgehog-gli and estrogen receptor signaling pathways

Hedgehog-Gli (Hh-Gli) signaling pathway is one of the new molecular targets found upregulated in breast tumors. Estrogen receptor alpha (ERα) signaling has a key role in the development of hormone-dependent breast cancer. We aimed to investigate the effects of inhibiting both pathways simultaneously on breast cancer cell survival and the potential interactions between these two signaling pathways. ER-positive MCF-7 cells show decreased viability after treatment with cyclopamine, a Hh-Gli pathway inhibitor, as well as after tamoxifen (an ERα inhibitor) treatment. Simultaneous treatment with cyclopamine and tamoxifen on the other hand, causes short-term survival of cells, and increased migration. We found upregulated Hh-Gli signaling under these conditions and protein profiling revealed increased expression of proteins involved in cell proliferation and migration. Therefore, even though Hh-Gli signaling seems to be a good potential target for breast cancer therapy, caution must be advised, especially when combining therapies. In addition, we also show a potential direct interaction between the Shh protein and ERα in MCF-7 cells. Our data suggest that the Shh protein is able to activate ERα independently of the canonical Hh-Gli signaling pathway. Therefore, this may present an additional boost for ER-positive cells that express Shh, even in the absence of estrogen.

Significance of glioma-associated oncogene homolog 1 (GLI1) expression in claudin-low breast cancer and crosstalk with the nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) pathway

Introduction

The recently identified claudin-low subtype of breast cancer is enriched for cells with stem-like and mesenchymal-like characteristics. This subtype is most often triple-negative (lacking the estrogen and progesterone receptors (ER, PR) as well as lacking epidermal growth factor 2 (HER2) amplification) and has a poor prognosis. There are few targeted treatment options available for patients with this highly aggressive type of cancer.

Methods

Using a high throughput inhibitor screen, we identified high expression of glioma-associated oncogene homolog 1 (GLI1), the effector molecule of the hedgehog (Hh) pathway, as a critical determinant of cell lines that have undergone an epithelial to mesenchymal transition (EMT).

Results

High GLI1 expression is a property of claudin-low cells and tumors and correlates with markers of EMT and breast cancer stem cells. Knockdown of GLI1 expression in claudin-low cell lines resulted in reduced cell viability, motility, clonogenicity, self-renewal, and reduced tumor growth of orthotopic xenografts. We observed non-canonical activation of GLI1 in claudin-low and EMT cell lines, and identified crosstalk with the NFκB pathway.

Conclusions

This work highlights the importance of GLI1 in the maintenance of characteristics of metastatic breast cancer stem cells. Remarkably, treatment with an inhibitor of the NFκB pathway reproducibly reduces GLI1 expression and protein levels. We further provide direct evidence for the binding of the NFκB subunit p65 to the GLI1 promoter in both EMT and claudin-low cell lines. Our results uncover crosstalk between NFκB and GLI1 signals and suggest that targeting these pathways may be effective against the claudin-low breast cancer subtype.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-014-0444-4) contains supplementary material, which is available to authorized users.

Smoothened gene alterations in keratocystic odontogenic tumors

Background

It has been widely demonstrated that the hedgehog pathway is strongly associated with basal cell carcinoma of the skin (NBCCS). To assess potential DNA alterations related to keratocystic odontogenic tumors (KCOTs), we sequenced smoothened (SMO) genes in 12 sporadic KCOTs.

Methods

Polymerase chain reaction (PCR), capillary electrophoresis and dideoxy chain-termination sequencing were used to examine potential DNA alterations in sporadic KCOTs.

Results

Five alterations in SMO genes were detected. Four of these mutations consisted of two synonymous and three missense mutations; two of which have not been reported to date (c.T776A, c.T1281G).

Conclusions

SMO genes may play an important role in the sonic hedgehog (SHH) pathway and could also be responsible for generating KCOTs and NBCCS. However, their influence on SHH signaling remains to be elucidated.

Medicinal history of North American Veratrum

Plants belonging to the genus Veratrum have been used throughout history for their medicinal properties. During the nineteenth and twentieth centuries, phytochemical investigations revealed a host of steroidal alkaloids in Veratrum species, some of which are potent bioactives. This review discusses Veratrum species that grow in North America with a focus on the medicinal history of these plants and the steroidal alkaloids they contain. While significant reviews have been devoted to singularly describing the plant species within the genus Veratrum (botany), the staggering breadth of alkaloids isolated from these and related plants (phytochemistry), and the intricacies of how the various alkaloids act on their biological targets (physiology and biochemistry), this review will straddle the margins of the aforementioned disciplines in an attempt to provide a unified, coherent picture of the Veratrum plants of North America and the medicinal uses of their bioactive steroidal alkaloids.

Oestrogen receptor-alpha regulates non-canonical Hedgehog-signalling in the mammary gland

Mesenchymal dysplasia (mes) mice harbour a truncation in the C-terminal region of the Hh-ligand receptor, Patched-1 (mPtch1). While the mes variant of mPtch1 binds to Hh-ligands with an affinity similar to that of wild type mPtch1 and appears to normally regulate canonical Hh-signalling via smoothened, the mes mutation causes, among other non-lethal defects, a block to mammary ductal elongation at puberty. We demonstrated previously Hh-signalling induces the activation of Erk1/2 and c-src independently of its control of smo activity. Furthermore, mammary epithelial cell-directed expression of an activated allele of c-src rescued the block to ductal elongation in mes mice, albeit with delayed kinetics. Given that this rescue was accompanied by an induction in estrogen receptor-alpha (ERα) expression and that complex regulatory interactions between ERα and c-src are required for normal mammary gland development, it was hypothesized that expression of ERα would also overcome the block to mammary ductal elongation at puberty in the mes mouse. We demonstrate here that conditional expression of ERα in luminal mammary epithelial cells on the mes background facilitates ductal morphogenesis with kinetics similar to that of the MMTV-c-src(Act) mice. We demonstrate further that Erk1/2 is activated in primary mammary epithelial cells by Shh-ligand and that this activation is blocked by the inhibitor of c-src, PP2, is partially blocked by the ERα inhibitor, ICI 182780 but is not blocked by the smo-inhibitor, SANT-1. These data reveal an apparent Hh-signalling cascade operating through c-src and ERα that is required for mammary gland morphogenesis at puberty.

Distinct effects of the mesenchymal dysplasia gene variant of murine Patched-1 protein on canonical and non-canonical Hedgehog signaling pathways

Hedgehog (Hh) signaling requires regulation of the receptor Patched-1 (Ptch1), which, in turn, regulates Smoothened activity (canonical Hh signaling) as well as other non-canonical signaling pathways. The mutant Ptch1 allele mesenchymal dysplasia (mes), which truncates the Ptch1 C terminus, produces a limited spectrum of developmental defects in mice as well as deregulation of canonical Hh signaling in some, but not all, affected tissues. Paradoxically, mes suppresses canonical Hh signaling and binds to Hh ligands with an affinity similar to wild-type mouse Ptch1 (mPtch1). We characterized the distinct activities of the mes variant of mPtch1 mediating Hh signaling through both canonical and non-canonical pathways. We demonstrated that mPtch1 bound c-src in an Hh-regulated manner. Stimulation with Sonic Hedgehog (Shh) of primary mammary mesenchymal cells from wild-type and mes animals activated Erk1/2. Although Shh activated c-src in wild-type cells, c-src was constitutively activated in mes mesenchymal cells. Transient assays showed that wild-type mPtch1, mes, or mPtch1 lacking the C terminus repressed Hh signaling in Ptch1-deficient mouse embryo fibroblasts and that repression was reversed by Shh, revealing that the C terminus was dispensable for mPtch1-dependent regulation of canonical Hh signaling. In contrast to these transient assays, constitutively high levels of mGli1 but not mPtch1 were present in primary mammary mesenchymal cells from mes mice, whereas the expression of mPtch1 was similarly induced in both mes and wild-type cells. These data define a novel signal transduction pathway involving c-src that is activated by the Hh ligands and reveals the requirement for the C terminus of Ptch in regulation of canonical and non-canonical Hh signaling pathways.

Transcription of the SCL/TAL1 interrupting Locus (Stil) is required for cell proliferation in adult Zebrafish Retinas

The human oncogene SCL/TAL1 interrupting locus (Stil) is highly conserved in vertebrate species. Previously, we identified a homolog of the Stil gene in zebrafish mutant (night blindness b, nbb), which showed neural defects in the retina (e.g. dopaminergic cell degeneration and/or lack of regeneration). In this research, we examined the roles of Stil in cell proliferation after degeneration in adult zebrafish retinas. We demonstrated that knockdown of Stil gene expression or inhibition of Sonic hedgehog (Shh) signaling transduction decreases the rate of cell proliferation. In contrast, activation of Shh signal transduction promotes cell proliferation. In nbb(+/-) retinas, inhibition of SUFU (a repressor in the Shh pathway) rescues the defects in cell proliferation due to down-regulation of Stil gene expression. The latter data suggest that Stil play a role in cell proliferation through the Shh signal transduction pathway.

Wwox suppresses breast cancer cell growth through modulation of the hedgehog-GLI1 signaling pathway

Wwox is a tumor suppressor that is frequently deleted or altered in several cancer types, including breast cancer. Previous studies have shown that ectopic expression of Wwox inhibits proliferation of breast cancer cells. However, the underlying mechanism remains unclear. To better understand the molecular mechanisms of Wwox function, we investigated novel partners of this protein. Utilizing the coimmunoprecipitation assay, we observed a physical association between Wwox and the Gli1 zinc-finger transcription factor involved in the hedgehog pathway. Our results further demonstrated that Wwox expression triggered redistribution of nuclear Gli1 to the cytoplasm. Additionally, ectopic expression of Wwox reduced Gli1 expression in vitro. Furthermore, Gli1 Blocks Wwox-induced breast cancer cell growth inhibition. These findings suggest a functional crosstalk between Wwox and hedgehog-GLI1 signaling pathway in tumorigenesis.

High expression of Sonic Hedgehog signaling pathway genes indicates a risk of recurrence of breast carcinoma

BACKGROUND

Abnormal activation of the Sonic Hedgehog (SHH) signaling pathway contributing to carcinogenesis of some organs has been reported in the literature. We hypothesize that activation of the SHH pathway contributes to the recurrence of breast carcinoma.

METHODS

Fifty consecutive patients with invasive breast carcinoma following curative resection were enrolled in this prospective study. The ratios of messenger RNA (mRNA) expression for Sonic Hedgehog (SHH), patched homolog-1 (PTCH-1), glioma-associated oncogene-1 (GLI-1), and smoothened (SMOH) were measured between breast carcinoma tissue and paired noncancerous breast tissue. These ratios were compared with their clinicopathologic characteristics. These factors and the mRNA ratios were compared between patients with recurrence and those without recurrence.

RESULTS

The size of the invasive cancer correlated significantly with the ratio of SHH mRNA (P=0.001), that of PTCH-1 mRNA (P=0.005), and that of SMOH mRNA (P=0.021). Lymph node involvement correlated significantly with the ratio of SMOH mRNA (P=0.041). The correlation between Her-2 neu and the ratio of GLI-1 mRNA was statistically significant (P=0.012). Each ratio of mRNA of SHH, PTCH-1, GLI-1, and SMOH correlated significantly with cancer recurrence (P<0.001 for each).

CONCLUSION

We suggest that high expression of SHH mRNA, PTCH-1 mRNA, GLI-1 mRNA, and SMOH mRNA in breast cancer tissue correlates with invasiveness and is a potential biomarker to predict postoperative recurrence.