Haploinsufficiency in the prometastasis Kiss1 receptor Gpr54 delays breast tumor initiation, progression, and lung metastasis

Guanine nucleotide exchange factors for Rho GTPases (RhoGEFs) as oncogenic effectors and strategic therapeutic targets in metastatic cancer

Metastatic cancer cells dynamically adjust their shape to adhere, invade, migrate, and expand to generate secondary tumors. Inherent to these processes is the constant assembly and disassembly of cytoskeletal supramolecular structures. The subcellular places where cytoskeletal polymers are built and reorganized are defined by the activation of Rho GTPases. These molecular switches directly respond to signaling cascades integrated by Rho guanine nucleotide exchange factors (RhoGEFs), which are sophisticated multidomain proteins that control morphological behavior of cancer and stromal cells in response to cell-cell interactions, tumor-secreted factors and actions of oncogenic proteins within the tumor microenvironment. Stromal cells, including fibroblasts, immune and endothelial cells, and even projections of neuronal cells, adjust their shapes and move into growing tumoral masses, building tumor-induced structures that eventually serve as metastatic routes. Here we review the role of RhoGEFs in metastatic cancer. They are highly diverse proteins with common catalytic modules that select among a variety of homologous Rho GTPases enabling them to load GTP, acquiring an active conformation that stimulates effectors controlling actin cytoskeleton remodeling. Therefore, due to their strategic position in oncogenic signaling cascades, and their structural diversity flanking common catalytic modules, RhoGEFs possess unique characteristics that make them conceptual targets of antimetastatic precision therapies. Preclinical proof of concept, demonstrating the antimetastatic effect of inhibiting either expression or activity of βPix (ARHGEF7), P-Rex1, Vav1, ARHGEF17, and Dock1, among others, is emerging.

YAP/TAZ activation predicts clinical outcomes in mesothelioma and is conserved in in vitro model of driver mutations

The Hippo signalling pathway is dysregulated across a wide range of cancer types and, although driver mutations that directly affect the core Hippo components are rare, a handful is found within pleural mesothelioma (PM). PM is a deadly disease of the lining of the lung caused by asbestos exposure. By pooling the largest-scale clinical datasets publicly available, we here interrogate associations between the most prevalent driver mutations within PM and Hippo pathway disruption in patients, while assessing correlations with a variety of clinical markers. This analysis reveals a consistent worse outcome in patients exhibiting transcriptional markers of YAP/TAZ activation, pointing to the potential of leveraging Hippo pathway transcriptional activation status as a metric by which patients may be meaningfully stratified. Preclinical models recapitulating disease are transformative in order to develop new therapeutic strategies. We here establish an isogenic cell-line model of PM, which represents the most frequently mutated genes and which faithfully recapitulates the molecular features of clinical PM. This preclinical model is developed to probe the molecular basis by which the Hippo pathway and key driver mutations affect cancer initiation and progression. Implementing this approach, we reveal the role of NF2 as a mechanosensory component of the Hippo pathway in mesothelial cells. Cellular NF2 loss upon physiological stiffnesses analogous to the tumour niche drive YAP/TAZ-dependent anchorage-independent growth. Consequently, the development and characterisation of this cellular model provide a unique resource to obtain molecular insights into the disease and progress new drug discovery programs together with future stratification of PM patients.

The role of KiSS1 gene on the growth and migration of prostate cancer and the underlying molecular mechanisms

Metastatic prostate cancers have a high mortality rate. KiSS1 was originally identified as a metastasis suppressor gene in metastatic melanoma and breast cancer, but its role in prostate cancer has been contradictory. This study was therefore undertaken to investigate the effects of KiSS1 overexpression on the growth and migration of human metastatic prostate cancer cells. We first tested the effect of KiSS1 overexpression on the growth and migration of DU145 human metastatic prostate cancer cells in vitro. DU145 cells were infected with the culture medium of 293T cells, which produce lentivirus particles containing KiSS1. A 2.5-fold increase in proliferation of KiSS1-overexpressing cancer cells was observed, and these cells formed tumor spheroids about 3 times larger than the vector control group. qPCR and immunoblotting revealed the association between increased cell growth and regulation of the PI3K/Akt and cell cycle genes, and also that increases in β-catenin and CD133 contribute to tumor aggregation. KiSS1 overexpression resulted in upregulation of the β-arrestin1/2 and Raf-MEK-ERK-NF-κB pathways via KiSS1R. Moreover, the migration and invasion of KiSS1-overexpressing cells were determined to be faster than the control group, along with 1.6-fold increased metastatic colonization of the KiSS1-overexpressing cancer cells. These were associated to the regulation of EMT gene expressions, such as E-cadherin and N-cadherin, and the upregulation of MMP9. In a xenograft mouse model inoculated with DU145 cells infected GFP or KiSS1 via a lentiviral vector, KiSS1 statistically significantly increased the tumor growth, with upregulation of PCNA and Ki-67 in the tumor tissues. In addition, KiSS1 increased the angiogenic capacity by upregulating VEGF-A and CD31, both in vitro and in vivo. Taken together, our results indicate that KiSS1 not only induces prostate cancer proliferation, but also promotes metastasis by increasing the migration, invasion, and angiogenesis of malignant cells.

Functional analysis of the emerging roles for the KISS1/KISS1R signaling pathway in cancer metastasis

Cancer metastasis, a process that primary tumor cells disseminate to secondary organs, is the most lethal and least effectively treated characteristic of human cancers. Kisspeptins are proteins encoded by the KISS1 gene that was originally described as a melanoma metastasis suppressor gene. Then, Kisspeptins were discovered as the natural ligands of the G-protein-coupled receptor 54 (GPR54) that is also called KISS1R. The KISS1/KISS1R signaling is essential to control GnRH secretion during puberty and to establish mammalian reproductive function through the hypothalamic-pituitary-gonadal (HPG) axis. Although KISS1 primarily plays a suppressive role in the metastasis progression in several cancer types, emerging evidence indicates that the physiological effect of KISS1/KISS1R in cancer metastasis is tissue context-dependent and still controversial. Here, we will discuss the epigenetic mechanism regulation of KISS1 gene expression, the context-dependent role of KISS1/KISS1R, pro-/anti-metastasis signaling pathways of KISS1/KISS1R, and the perspective anti-cancer therapeutics via targeting KISS1/KISS1R.

Investigation of the content differences of arachidonic acid metabolites in a mouse model of breast cancer by using LC-MS/MS

Arachidonic acid (AA) is closely associated with breast cancer. In addition to the two metabolic pathways regulated by cyclooxygenase and lipoxygenase, AA has a third metabolic pathway through which cytochrome P450 (CYP) enzymes produce hydroxyeicosatetraenoic acids (HETEs) and epoxyeicosatrienoic acids (EETs). The targeted CYP-mediated pathway of AA can not only kill cancer cells but also inhibit the interstitial microenvironment around a tumor. Therefore, it makes sense to identify potential biomarkers from the AA metabolome for the diagnosis and treatment of breast cancer. This study established a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the analysis of AA and its main metabolites, EETs and HETEs, in MMTV-PyMT mice, a spontaneous breast cancer mouse model. The results showed that there were significant differences in the concentrations of AA, 12-HETE, 19-HETE and 8,9-EET in plasma and tumor tissues between normal and MMTV-PyMT mice. Therefore, the eicosanoids mentioned above may be used as new biomarkers for breast cancer diagnosis. This study provides a new perspective for the recognition and diagnosis of breast cancer.

KISS1 in metastatic cancer research and treatment: potential and paradoxes

The significance of KISS1 goes beyond its original discovery as a metastasis suppressor. Its function as a neuropeptide involved in diverse physiologic processes is more well studied. Enthusiasm regarding KISS1 has cumulated in clinical trials in multiple fields related to reproduction and metabolism. But its cancer therapeutic space is unsettled. This review focuses on collating data from cancer and non-cancer fields in order to understand shared and disparate signaling that might inform clinical development in the cancer therapeutic and biomarker space. Research has focused on amino acid residues 68-121 (kisspeptin 54), binding to the KISS1 receptor and cellular responses. Evidence and counterevidence regarding this canonical pathway require closer look at the covariates so that the incredible potential of KISS1 can be realized.

Role of the tumor microenvironment in regulating the anti-metastatic effect of KISS1

KISS1, a metastasis suppressor gene, has been shown to block metastasis without affecting primary tumor formation. Loss of KISS1 leads to invasion and metastasis in multiple cancers, which is the leading cause of cancer morbidity and mortality. The discovery of KISS1 has provided a ray of hope for early clinical diagnosis and for designing effective treatments targeting metastatic cancer. However, this goal requires greater holistic understanding of its mechanism of action. In this review, we go back into history and highlight some key developments, from the discovery of KISS1 to its role in regulating multiple physiological processes including cancer. We discuss key emerging roles for KISS1, specifically interactions with tissue microenvironment to promote dormancy and regulation of tumor cell metabolism, acknowledged as some of the key players in tumor progression and metastasis. We finally discuss strategies whereby KISS1 might be exploited clinically to treat metastasis.

G protein-coupled kisspeptin receptor induces metabolic reprograming and tumorigenesis in estrogen receptor-negative breast cancer

Triple-negative breast cancer (TNBC) is a highly metastatic and deadly disease. TNBC tumors lack estrogen receptor (ERα), progesterone receptor (PR), and HER2 (ErbB2) and exhibit increased glutamine metabolism, a requirement for tumor growth. The G protein-coupled kisspeptin receptor (KISS1R) is highly expressed in patient TNBC tumors and promotes malignant transformation of breast epithelial cells. This study found that TNBC patients displayed elevated plasma kisspeptin levels compared with healthy subjects. It also provides the first evidence that in addition to promoting tumor growth and metastasis in vivo, KISS1R-induced glutamine dependence of tumors. In addition, tracer-based metabolomics analyses revealed that KISS1R promoted glutaminolysis and nucleotide biosynthesis by increasing c-Myc and glutaminase levels, key regulators of glutamine metabolism. Overall, this study establishes KISS1R as a novel regulator of TNBC metabolism and metastasis, suggesting that targeting KISS1R could have therapeutic potential in the treatment of TNBC.

Long noncoding RNA TC0101441 induces epithelial-mesenchymal transition in epithelial ovarian cancer metastasis by downregulating KiSS1

Peritoneal metastasis is a critical feature and clinical challenge in epithelial ovarian cancer (EOC). We previously identified a novel long noncoding RNA (lncRNA, TC0101441) in epithelial ovarian cancer (EOC) using microarrays. However, the impact of TC0101441 on EOC metastasis and prognosis remains unclear. TC0101441 expression in EOC tissues and its correlation with clinicopathological factors and prognosis were examined. A series of in vitro and in vivo assays were performed to elucidate the roles and mechanism of TC0101441 in EOC metastasis. We found that TC0101441 levels were elevated in EOC tissues compared with those in normal controls and significantly correlated with an advanced clinical stage and lymph node metastasis. TC0101441 was determined to be an independent prognostic predictor of overall survival (OS) and disease-free survival (DFS). Furthermore, loss-of-function assays showed that TC0101441 promoted the invasive and metastatic capacities of EOC cells both in vitro and in vivo. Mechanistically, the prometastatic effects of TC0101441 were linked to the induction of epithelial-mesenchymal transition (EMT). Importantly, KiSS1 was identified as a downstream target gene of TC0101441 and was downregulated by TC0101441 in EOC cells. After TC0101441 was silenced, the corresponding phenotypes of EOC cell invasion and EMT were reversed by the overexpression of KiSS1. Taken together, our data suggest that TC0101441 functions as a potential promigratory/invasive oncogene by promoting EMT and metastasis in EOC through downregulation of KiSS1, which may represent a novel prognostic marker and therapeutic target in EOC.

Epigenetically upregulated GEFT-derived invasion and metastasis of rhabdomyosarcoma via epithelial mesenchymal transition promoted by the Rac1/Cdc42-PAK signalling pathway

Background

Metastasis of rhabdomyosarcoma (RMS) is the primary cause of tumour-related deaths. Previous studies have shown that overexpression of the guanine nucleotide exchange factor T (GEFT) is correlated with a poorer RMS prognosis, but the mechanism remains largely unexplored.

Methods

We focused on determining the influence of the GEFT-Rho-GTPase signalling pathway and the epithelial–mesenchymal transition (EMT) or mesenchymal–epithelial transition (MET) on RMS progression and metastasis by using RMS cell lines, BALB/c nude mice and cells and molecular biology techniques.

Findings

GEFT promotes RMS cell viability, migration, and invasion; GEFT also inhibits the apoptosis of RMS cells and accelerates the growth and lung metastasis of RMS by activating the Rac1/Cdc42 pathways. Interestingly, GEFT upregulates the expression levels of N-cadherin, Snail, Slug, Twist, Zeb1, and Zeb2 and reduces expression level of E-cadherin. Thus, GEFT influences the expression of markers for EMT and MET in RMS cells via the Rac1/Cdc42-PAK1 pathways. We also found that the level of GEFT gene promoter methylation in RMS is lower than that in normal striated muscle tissue. Significant differences were observed in the level of GEFT gene methylation in different histological subtypes of RMS.

Interpretation

These findings suggest that GEFT accelerates the tumourigenicity and metastasis of RMS by activating Rac1/Cdc42-PAK signalling pathway-induced EMT; thus, it may serve as a novel therapeutic target.

Fund

This work was supported by grants from the National Natural Science Foundation of China (81660441, 81460404, and 81160322) and Shihezi University Initiative Research Projects for Senior Fellows (RCZX201447). Funders had no role in the design of the study, data collection, data analysis, interpretation, or the writing of this report.

The role of kisspeptin system in cancer biology

Kisspeptins are a family of neuropeptides that are known to be critical in puberty initiation and ovulation. Apart from that kisspeptin derived peptides (KPs) are also known for their antimetastatic activities in several malignancies. Herein we report recent evidence of the role of kisspeptins in cancer biology and we examine the prospective of targeting the kisspeptin pathways leading to a better prognosis in patients with malignant diseases.

Autocrine production of reproductive axis neuropeptides affects proliferation of canine osteosarcoma in vitro

Background

Osteosarcoma strikes hundreds of people each year, of both advanced and younger ages, and is often terminal. Like many tumor types, these bone tumors will frequently undergo a neuroendocrine transition, utilizing autocrine and/or paracrine hormones as growth factors and/or promoters of angiogenesis to facilitate progression and metastasis. While many of these factors and their actions on tumor growth are characterized, some tumor-derived neuropeptides remain unexplored.

Methods

Using validated canine osteosarcoma cell lines in vitro, as well as cells derived from spontaneous tumors in dogs, we explored the autocrine production of two neuropeptides typically found in the hypothalamus, and most closely associated with reproduction: gonadotropin-releasing hormone (GnRH) and kisspeptin (Kiss-1). We evaluated gene expression and protein secretion of these hormones using quantitative RT-PCR and a sensitive radioimmunoassay, and explored changes in cell proliferation determined by MTS cell viability assays.

Results

Our current studies reveal that several canine osteosarcoma cell lines (COS, POS, HMPOS, D17, C4) synthesize and secrete GnRH and express the GnRH receptor, while COS and POS also express kiss1 and its cognate receptor. We have further found that GnRH and kisspeptin, exogenously applied to these tumor cells, exert significant effects on both gene expression and proliferation. Of particular interest, kisspeptin exposure stimulated GnRH secretion from COS, similarly to the functional relationship observed within the neuroendocrine reproductive axis. Additionally, GnRH and kisspeptin treatment both increased COS proliferation, which additionally manifested in increased expression of the bone remodeling ligand rankl within these cells. These effects were blocked by treatment with a specific GnRH receptor inhibitor. Both neuropeptides were found to increase expression of the specific serotonin (5HT) receptor htr2a, the activation of which has previously been associated with cellular proliferation, suggesting that production of these factors by osteosarcoma cells may act to sensitize tumors to circulating 5HT of local and/or enteric origin.

Conclusions

Here we report that kisspeptin and GnRH act as autocrine growth factors in canine osteosarcoma cells in vitro, modulating RANKL and serotonin receptor expression in a manner consistent with pro-proliferative effects. Pharmacological targeting of these hormones may represent new avenues of osteosarcoma treatment.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5363-4) contains supplementary material, which is available to authorized users.

The matrix protein Fibulin-3 promotes KISS1R induced triple negative breast cancer cell invasion

Breast cancer is a leading cause of cancer mortality. In particular, triple negative breast cancer (TNBC) comprise a heterogeneous group of basal-like tumors lacking estrogen receptor (ERα), progesterone receptor (PR) and HER2 (ErbB2). TNBC represents 15-20% of all breast cancers and occurs frequently in women under 50 years of age. Unfortunately, these patients lack targeted therapy, are typically high grade and metastatic at time of diagnosis. The mechanisms regulating metastasis remain poorly understood. We have previously shown that the kisspeptin receptor, KISS1R stimulates invasiveness of TNBC cells. In this report, we demonstrate that KISS1R signals via the secreted extracellular matrix protein, fibulin-3, to regulate TNBC invasion. We found that the fibulin-3 gene is amplified in TNBC primary tumors and that plasma fibulin-3 levels are elevated in TNBC patients compared to healthy subjects. In this study, we show that KISS1R activation increases fibulin-3 expression and secretion. We show that fibulin-3 regulates TNBC metastasis in a mouse experimental metastasis xenograft model and signals downstream of KISS1R to stimulate TNBC invasion, by activating matrix metalloproteinase 9 (MMP-9) and the MAPK pathway. These results identify fibulin-3 as a new downstream mediator of KISS1R signaling and as a potential biomarker for TNBC progression and metastasis, thus revealing KISS1R and fibulin-3 as novel drug targets in TNBC.

The retinoblastoma protein regulates hypoxia-inducible genetic programs, tumor cell invasiveness and neuroendocrine differentiation in prostate cancer cells

Loss of tumor suppressor proteins, such as the retinoblastoma protein (Rb), results in tumor progression and metastasis. Metastasis is facilitated by low oxygen availability within the tumor that is detected by hypoxia inducible factors (HIFs). The HIF1 complex, HIF1α and dimerization partner the aryl hydrocarbon receptor nuclear translocator (ARNT), is the master regulator of the hypoxic response. Previously, we demonstrated that Rb represses the transcriptional response to hypoxia by virtue of its association with HIF1. In this report, we further characterized the role Rb plays in mediating hypoxia-regulated genetic programs by stably ablating Rb expression with retrovirally-introduced short hairpin RNA in LNCaP and 22Rv1 human prostate cancer cells. DNA microarray analysis revealed that loss of Rb in conjunction with hypoxia leads to aberrant expression of hypoxia-regulated genetic programs that increase cell invasion and promote neuroendocrine differentiation. For the first time, we have established a direct link between hypoxic tumor environments, Rb inactivation and progression to late stage metastatic neuroendocrine prostate cancer. Understanding the molecular pathways responsible for progression of benign prostate tumors to metastasized and lethal forms will aid in the development of more effective prostate cancer therapies.

KISS1/KISS1R in Cancer: Friend or Foe?

The KISS1 gene encodes KISS1, a protein that is rapidly processed in serum into smaller but biologically active peptides called kisspeptins (KPs). KISS1 and the KPs signal via the G-protein coupled receptor KISS1R. While KISS1 and KPs are recognized as potent positive regulators of the reproductive neuroendocrine axis in mammals, the first reported role for KISS1 was that of metastasis suppression in melanoma. Since then, it has become apparent that KISS1, KPs, and KISS1R regulate the development and progression of several cancers but interestingly, while these molecules act as suppressors of tumorigenesis and metastasis in many cancers, in breast and liver cancer they function as promoters. Thus, they join a small but growing number of molecules that exhibit dual roles in cancer highlighting the importance of studying cancer in context. Given their roles, KISS1, KPs and KISS1R represent important molecules in the development of novel therapies and/or as prognostic markers in treating cancer. However, getting to that point requires a detailed understanding of the relationship between these molecules and different cancers. The purpose of this review is therefore to highlight and discuss the clinical studies that have begun describing this relationship in varying cancer types including breast, liver, pancreatic, colorectal, bladder, and ovarian. An emerging theme from the reviewed studies is that the relationship between these molecules and a given cancer is complex and affected by many factors such as the micro-environment and steroid receptor status of the cancer cell. Our review and discussion of these important clinical studies should serve as a valuable resource in the successful development of future clinical studies.

Controversial Role of Kisspeptins/KiSS-1R Signaling System in Tumor Development

KiSS-1 was first described as a metastasis suppressor gene in malignant melanoma. KiSS-1 encodes a 145 amino-acid residue peptide that is further processed, producing the 54 amino acid metastin and shorter peptides collectively named kisspeptins (KPs). KPs bind and activate KiSS-1R (GPR54). Although the KPs system has been extensively studied for its role in endocrinology of reproductive axis in mammals, its role in cancer is still controversial. Experimental evidences show that KP system exerts an anti-metastatic effect by the regulation of cellular migration and invasion in several cancer types. However, the role of KPs/KiSS-1R is very complex. Genomic studies suggest that KiSS-1/KiSS-1R expression might be different in the various stages of tumor development. Furthermore, overexpression of KiSS-1R has been reported to elicit drug resistance in triple negative breast cancer. In this review, we focused on multiple functions exerted by the KPs/KiSS-1R system in regulating tumor progression.

LGR4 modulates breast cancer initiation, metastasis, and cancer stem cells

The fourth member of the leucine-rich repeat-containing GPCR family (LGR4, frequently referred to as GPR48) and its cognate ligands, R-spondins (RSPOs) play crucial roles in the development of multiple organs as well as the survival of adult stem cells by activation of canonical Wnt signaling. Wnt/β-catenin signaling acts to regulate breast cancer; however, the molecular mechanisms determining its spatiotemporal regulation are largely unknown. In this study, we identified LGR4 as a master controller of Wnt/β-catenin signaling-mediated breast cancer tumorigenesis, metastasis, and cancer stem cell (CSC) maintenance. LGR4 expression in breast tumors correlated with poor prognosis. Either Lgr4 haploinsufficiency or mammary-specific deletion inhibited mouse mammary tumor virus (MMTV)- PyMT- and MMTV- Wnt1-driven mammary tumorigenesis and metastasis. Moreover, LGR4 down-regulation decreased in vitro migration and in vivo xenograft tumor growth and lung metastasis. Furthermore, Lgr4 deletion in MMTV- Wnt1 tumor cells or knockdown in human breast cancer cells decreased the number of functional CSCs by ∼90%. Canonical Wnt signaling was impaired in LGR4-deficient breast cancer cells, and LGR4 knockdown resulted in increased E-cadherin and decreased expression of N-cadherin and snail transcription factor -2 ( SNAI2) (also called SLUG), implicating LGR4 in regulation of epithelial-mesenchymal transition. Our findings support a crucial role of the Wnt signaling component LGR4 in breast cancer initiation, metastasis, and breast CSCs.-Yue, Z., Yuan, Z., Zeng, L., Wang, Y., Lai, L., Li, J., Sun, P., Xue, X., Qi, J., Yang, Z., Zheng, Y., Fang, Y., Li, D., Siwko, S., Li, Y., Luo, J., Liu, M. LGR4 modulates breast cancer initiation, metastasis, and cancer stem cells.

KiSS1 gene as a novel mediator of TGFβ-mediated cell invasion in triple negative breast cancer

The invasive and metastatic phenotypes of breast cancer correlate with high recurrence rates and poor survival outcomes. Transforming growth factor-β (TGFβ) promotes tumor progression and metastasis in aggressive breast cancer. Here, we identified the kisspeptin KiSS1 as a downstream target of canonical TGFβ/Smad2 pathway in triple negative breast cancer cells. We also found KiSS1 expression to be required for TGFβ-induced cancer cell invasion. Indeed, knockdown expression of KiSS1 blocked TGFβ-mediated cancer cell invasion as well as metalloproteinase (MMP9) expression and activity. Interestingly, Kisspeptin-10 (KP-10), the smallest active form of kisspeptin also stimulates cancer cell invasive behavior through activation of MAPK/Erk pathway. We described a positive feedback loop between KiSS1 and p21 downstream of TGFβ, further contributing to TGFβ-induced cancer cell invasion. Lastly, we explored both the clinical utility of KiSS1 as a lymph node involvement predictive tool and its potential as a therapeutic target. We found KiSS1 high expression to correlate with lymph node positive status. Furthermore, blocking KiSS1 using a specific small peptide antagonist (p234) impaired TGFβ-mediated cell invasion and MMP9 induction. Together, our results define an essential role of KiSS1 in regulating TGFβ pro-invasive effects and define KiSS1 as a therapeutic new target for triple negative breast cancer.

Kisspeptin inhibits cancer growth and metastasis via activation of EIF2AK2

Kisspeptin is a protein encoded by the KISS1 gene, which has been reported to suppress the metastatic capabilities of various types of cancer cells, through the activation of its G‑protein coupled receptor GPR54. However, the molecular mechanisms underlying the involvement of kisspeptin‑mediated signaling in the inhibition of cancer cell migration and invasion have yet to be elucidated. The present in vitro cell proliferation, migration and invasion assays and in vivo experimental metastasis studies demonstrated that kisspeptin‑induced eukaryotic translation initiation factor 2α kinase 2 (EIF2AK2) activation suppressed the metastatic capabilities of several types of cancer cells. Kisspeptin was revealed to inhibit the migratory and invasive abilities of highly metastatic breast SK‑BR‑3, prostatic PC‑3 and colorectal adenocarcinoma LoVo human cancer cell lines, whereas its inhibitory effects were abolished following the silencing of EIF2AK2 expression using RNA interference. Similarly, kisspeptin failed to inhibit the migration and invasion of mouse embryonic fibroblasts following the deletion of the EIF2AK2 gene. Furthermore, kisspeptin was demonstrated to activate Ras homolog gene family member A (RhoA)‑dependent signaling, and to phosphorylate EIF2AK2 via RhoA‑mediated pathways in various cancer cells. In addition, results obtained from nude mice bearing LoVo‑derived xenograft tumors revealed that kisspeptin inhibited tumor growth through an EIF2AK2‑dependent mechanism, and an in vivo metastasis assay identified kisspeptin‑activated EIF2AK2 signaling as critical for the suppression of distant metastasis. The present study concluded that kisspeptin represses cancer metastasis via EIF2AK2 signaling, thus clarifying the role of kisspeptin signaling in complicated cancer metastasis signaling network. Therefore, kisspeptin treatment may be a choice for blocking metastases.

Retinoblastoma protein (Rb) links hypoxia to altered mechanical properties in cancer cells as measured by an optical tweezer

Hypoxia modulates actin organization via multiple pathways. Analyzing the effect of hypoxia on the biophysical properties of cancer cells is beneficial for studying modulatory signalling pathways by quantifying cytoskeleton rearrangements. We have characterized the biophysical properties of human LNCaP prostate cancer cells that occur in response to loss of the retinoblastoma protein (Rb) under hypoxic stress using an oscillating optical tweezer. Hypoxia and Rb-loss increased cell stiffness in a fashion that was dependent on activation of the extracellular signal-regulated kinase (ERK) and the protein kinase B (AKT)- mammalian target of rapamycin (MTOR) pathways. Pharmacological inhibition of MEK1/2, AKT or MTOR impeded hypoxia-inducible changes in the actin cytoskeleton and inhibited cell migration in Rb-deficient cells conditioned with hypoxia. These results suggest that loss of Rb in transformed hypoxic cancer cells affects MEK1/2-ERK/AKT-MTOR signalling and promotes motility. Thus, the mechanical characterization of cancer cells using an optical tweezer provides an additional technique for cancer diagnosis/prognosis and evaluating therapeutic performance.

G protein-coupled KISS1 receptor is overexpressed in triple negative breast cancer and promotes drug resistance

Triple-negative breast cancer (TNBC) lacks the expression of estrogen receptor α, progesterone receptor and human epidermal growth factor receptor 2 (HER2). TNBC patients lack targeted therapies, as they fail to respond to endocrine and anti-HER2 therapy. Prognosis for this aggressive cancer subtype is poor and survival is limited due to the development of resistance to available chemotherapies and resultant metastases. The mechanisms regulating tumor resistance are poorly understood. Here we demonstrate that the G protein-coupled kisspeptin receptor (KISS1R) promotes drug resistance in TNBC cells. KISS1R binds kisspeptins, peptide products of the KISS1 gene and in numerous cancers, this signaling pathway plays anti-metastatic roles. However, in TNBC, KISS1R promotes tumor invasion. We show that KISS1 and KISS1R mRNA and KISS1R protein are upregulated in TNBC tumors, compared to normal breast tissue. KISS1R signaling promotes drug resistance by increasing the expression of efflux drug transporter, breast cancer resistance protein (BCRP) and by inducing the activity and transcription of the receptor tyrosine kinase, AXL. BCRP and AXL transcripts are elevated in TNBC tumors, compared to normal breast, and TNBC tumors expressing KISS1R also express AXL and BCRP. Thus, KISS1R represents a potentially novel therapeutic target to restore drug sensitivity in TNBC patients.

For robust big data analyses: a collection of 150 important pro-metastatic genes

Metastasis is the greatest contributor to cancer-related death. In the era of precision medicine, it is essential to predict and to prevent the spread of cancer cells to significantly improve patient survival. Thanks to the application of a variety of high-throughput technologies, accumulating big data enables researchers and clinicians to identify aggressive tumors as well as patients with a high risk of cancer metastasis. However, there have been few large-scale gene collection studies to enable metastasis-related analyses. In the last several years, emerging efforts have identified pro-metastatic genes in a variety of cancers, providing us the ability to generate a pro-metastatic gene cluster for big data analyses. We carefully selected 285 genes with in vivo evidence of promoting metastasis reported in the literature. These genes have been investigated in different tumor types. We used two datasets downloaded from The Cancer Genome Atlas database, specifically, datasets of clear cell renal cell carcinoma and hepatocellular carcinoma, for validation tests, and excluded any genes for which elevated expression level correlated with longer overall survival in any of the datasets. Ultimately, 150 pro-metastatic genes remained in our analyses. We believe this collection of pro-metastatic genes will be helpful for big data analyses, and eventually will accelerate anti-metastasis research and clinical intervention.

KISS1R signaling promotes invadopodia formation in human breast cancer cell via β-arrestin2/ERK

Kisspeptins (KPs), peptide products of the KISS1 gene are endogenous ligands for the kisspeptin receptor (KISS1R), a G protein-coupled receptor. In numerous cancers, KISS1R signaling plays anti-metastatic roles. However, we have previously shown that in breast cancer cells lacking the estrogen receptor (ERα), kisspeptin-10 stimulates cell migration and invasion by cross-talking with the epidermal growth factor receptor (EGFR), via a β-arrestin-2-dependent mechanism. To further define the mechanisms by which KISS1R stimulates invasion, we determined the effect of down-regulating KISS1R expression in triple negative breast cancer cells. We found that depletion of KISS1R reduced their mesenchymal phenotype and invasiveness. We show for the first time that KISS1R signaling induces invadopodia formation and activation of key invadopodia proteins, cortactin, cofilin and membrane type I matrix metalloproteases (MT1-MMP). Moreover, KISS1R stimulated invadopodia formation occurs via a new pathway involving a β-arrestin2 and ERK1/2-dependent mechanism, independent of Src. Taken together, our findings suggest that targeting the KISS1R signaling axis might be a promising strategy to inhibit invasiveness and metastasis.

The effects of kisspeptin-10 on migration and proliferation of endothelial cell

BACKGROUND

Migration, expansion and survival of endothelial cells that are an important cellular component of blood vessels plays an important role in the induction of tumor growth. Kisspeptins (kp), peptides that bind to coupled-G protein receptor (GPR54), inhibit each step of metastatic cascade include invasion, migration and homing, angiogenesis, survival and proliferation. In this study we investigated effects of kisspeptin-10, the most potent member of kisspeptin family, on Migration and proliferation of endothelial cells that are necessary for angiogenesis and tumor metastasis.

MATERIALS AND METHODS

We compared migration of Human Umbilical Vein Endothelial Cells (HUVECs) were treated with 10-100 or 500 nM kp-10 for 24 hours and no treated cells using an in vitro trans membrane migration assay and HUVEC proliferation of treated endothelial cells with 10-100 or 500 nM kp-10 for 48 hours and no treated cells was measured by MTT Cell Proliferation Assay Kit. Analysis of data was performed using the Kruskal-Wallis test followed by the Mann-Whitney test.

RESULTS

Migration and proliferation of endothelial cells were increased at lower concentration of kp-10 specially at 100 nM while higher concentration reduced both migration and proliferation.

CONCLUSION

Our data showed that different concentrations of kp-10 have distinct effects on migration and proliferation of endothelial cells.

The effect of Kisspeptin-10 on mesenchymal stem cells migration in vitro and in vivo

BACKGROUND

Kisspeptins (kp) activate a receptor coupled to a Gαq subunit (GPR54 or KiSS-1R) receptor to perform a variety of functions, including inhibition of cell motility, chemotaxis, and metastasis. In this study we have investigated whether kp-10, the most potent member of the kisspeptin family, can modulate CXCR4 (C-X-C chemokine receptor type 4) expression and mesenchymal stem cells (MSCs) migration that may influence the development of tumors.

MATERIALS AND METHODS

We compared the directional migration of MSCs treated with 10-100 or 500 nM kp-10 for 24 hours and no treated cells using an in vitro transmembrane migration assay. In addition, Chloromethylbenzamido Dialkylacarbocyanine (CM-Dil) labeled adipose-derived mesenchymal stem cells treated with 10-100 or 500 nM kp-10 and no treated cells were transfused via the tail vein to the melanoma tumor bearing C57BL/6 mice. After 24 hours, the mice were scarified, the tumors were dissected, and the tumor cell suspensions were analyzed by flow cytometry for detection of CM-Dil(+) MSCs.

RESULTS

We have found that kp-10 increased the MSCs migration at 100 nM, while it decreased the MSCs migration at 500 nM, both in vitro and in vivo, with a significant increase of CXCR4 expression at 100 nM kp-10 compared to the no treated cells, but it had no significant difference between the various concentrations of kp-10.

CONCLUSION

Thus, our data showed that kp-10 can differently affect MSCs migration in various concentrations, probably through different effects on CXCR4 expression in various concentrations.

Lgr4 regulates mammary gland development and stem cell activity through the pluripotency transcription factor Sox2

The key signaling networks regulating mammary stem cells are poorly defined. The leucine-rich repeat containing G protein-coupled receptor (Lgr) family has been implicated in intestinal, gastric, and epidermal stem cell functions. We investigated whether Lgr4 functions in mammary gland development and mammary stem cells. We found that Lgr4(-/-) mice had delayed ductal development, fewer terminal end buds, and decreased side-branching. Crucially, the mammary stem cell repopulation capacity was severely impaired. Mammospheres from Lgr4(-/-) mice showed decreased Wnt signaling. Wnt3a treatment prevented the adverse effects of Lgr4 loss on organoid formation. Chromatin immunoprecipitation analysis indicated that Sox2 expression was controlled by the Lgr4/Wnt/β-catenin/Lef1 pathway. Importantly, Sox2 overexpression restored the in vivo mammary regeneration potential of Lgr4(-/-) mammary stem cells. Therefore, Lgr4 activates Sox2 to regulate mammary development and stem cell functions via Wnt/β-catenin/Lef1.

Herbal Prescription, DSGOST, Prevents Cold-Induced RhoA Activation and Endothelin-1 Production in Endothelial Cells

Herbal prescription, Danggui-Sayuk-Ga-Osuyu-Saenggang-tang (DSGOST), has long been used to treat Raynaud's phenomenon (RP) in traditional Chinese medicine (TCM). However, a biological mechanism by which DSGOST ameliorates RP is yet deciphered. In this study, we demonstrate that DSGOST inhibits cold-induced activation of RhoA, in both vascular smooth muscle cells (VSMC) and endothelial cells (EC), and blocks endothelin-1-mediated paracrine path for cold response on vessels. While cold induced RhoA activity in both cell types, DSGOST pretreatment prevented cold-induced RhoA activation. DSGOST inhibition of cold-induced RhoA activation further blocked α2c-adrenoreceptor translocation to the plasma membrane in VSMC. In addition, DSGOST inhibited endothelin-1-mediated RhoA activation and α2c-adrenoreceptor translocation in VSMC. Meanwhile, DSGOST inhibited cold-induced or RhoA-dependent phosphorylation of FAK, SRC, and ERK. Consistently, DSGOST inhibited cold-induced endothelin-1 expression in EC. Therefore, DSGOST prevents cold-induced RhoA in EC and blocks endothelin-1-mediated paracrine path between EC and VSMC. In conclusion, our data suggest that DSGOST is beneficial for treating RP-like syndrome.

Kisspeptin/KISS1R signaling potentiates extravillous trophoblast adhesion to type-I collagen in a PKC- and ERK1/2-dependent manner

During the first trimester of human pregnancy, cytotrophoblasts proliferate within the tips of the chorionic villi to form cell columns that anchor the placenta to the uterus. This migration coincides with a widespread change in the adhesion molecule repertoire of these trophoblasts. Kisspeptin and its receptor, KISS1R, are best known as potent triggers of gonadotropin-releasing hormone secretion. The kisspeptin/KISS1R signaling system is also highly expressed in the human placenta, where it was demonstrated to inhibit extra-villous trophoblast (EVT) migration and invasion in vitro. Here we show that kisspeptin, in a dose- and time-dependent manner, induces increased adhesion of human EVTs to type-I collagen, a major component of the human placenta. This increased adhesion was both rapid and transient, suggesting that it likely occurred through the activation of KISS1R secondary effectors such as PKC and ERK, which underwent rapid and transient kisspeptin-dependent activation in EVTs. We then showed that inhibition of both PKC and ERK1/2 attenuated the kisspeptin-dependent increase in EVT adhesion, suggesting that these molecules are key positive regulators of trophoblast adhesion. We therefore propose that kisspeptin/KISS1R signaling potentiates EVT adhesion to type-I collagen via "inside-out signaling." Furthermore, kisspeptin treatment increased mouse blastocyst adhesion to collagen I, suggesting that kisspeptin signaling is a key regulator of trophoblast function during implantation as well as early placentation.

Kisspeptin/KISS1R System in Breast Cancer

Kisspeptins (KP), peptide products of the kisspeptin-1 (KISS1) gene are the endogenous ligands for a G protein-coupled receptor (GPCR) - KP receptor (KISS1R). KISS1R couples to the Gα_q/11 signaling pathway. KISS1 is a metastasis suppressor gene and the KP/KISS1R signaling has anti-metastatic and tumor-suppressant effects in numerous human cancers. On the other hand, recent studies indicate that KP/KISS1R pathway plays detrimental roles in breast cancer. In this review, we summarize recent developments in the understanding of the mechanisms regulating KP/KISS1R signaling in breast cancer metastasis.

GPR116, an adhesion G-protein-coupled receptor, promotes breast cancer metastasis via the Gαq-p63RhoGEF-Rho GTPase pathway

Adhesion G-protein-coupled receptors (GPCR), which contain adhesion domains in their extracellular region, have been found to play important roles in cell adhesion, motility, embryonic development, and immune response. Because most adhesion molecules with adhesion domains have vital roles in cancer metastasis, we speculated that adhesion GPCRs are potentially involved in cancer metastasis. In this study, we identified GPR116 as a novel regulator of breast cancer metastasis through expression and functional screening of the adhesion GPCR family. We found that knockdown of GPR116 in highly metastatic (MDA-MB-231) breast cancer cells suppressed cell migration and invasion. Conversely, ectopic GPR116 expression in poorly metastatic (MCF-7 and Hs578T) cells promoted cell invasion. We further showed that knockdown of GPR116 inhibited breast cancer cell metastasis in two mammary tumor metastasis mouse models. Moreover, GPR116 modulated the formation of lamellipodia and actin stress fibers in cells in a RhoA- and Rac1-dependent manner. At a molecular level, GPR116 regulated cell motility and morphology through the Gαq-p63RhoGEF-RhoA/Rac1 pathway. The biologic significance of GPR116 in breast cancer is substantiated in human patient samples, where GPR116 expression is significantly correlated with breast tumor progression, recurrence, and poor prognosis. These findings show that GPR116 is crucial for the metastasis of breast cancer and support GPR116 as a potential prognostic marker and drug target against metastatic human breast cancer.

KiSS1 and its G-protein-coupled receptor GPR54 in cancer development and metastasis

KiSS1 and its cognate G-protein-coupled receptor, GPR54, have diverse functions. While KiSS1 and GPR54 have been intensively studied in physiology, their role in cancer is still unclear. In cancer, KiSS1 and GPR54 have been known to suppress metastasis by inhibiting cancer cell motility. However, recent studies suggest that KiSS1 and GPR54 have varied roles even in cancer development and metastasis. Here, we examine recent advances in understanding the roles of KiSS1 and GPR54 in cancer development and metastasis.

KISS1R induces invasiveness of estrogen receptor-negative human mammary epithelial and breast cancer cells

Kisspeptins (KPs), peptide products of the KISS1 metastasis-suppressor gene, are endogenous ligands for a G protein-coupled receptor (KISS1R). KISS1 acts as a metastasis suppressor in numerous human cancers. However, recent studies have demonstrated that an increase in KISS1 and KISS1R expression in patient breast tumors correlates with higher tumor grade and metastatic potential. We have shown that KP-10 stimulates invasion of estrogen receptor α (ERα)-negative MDA-MB-231 breast cancer cells via transactivation of the epidermal growth factor receptor (EGFR). Here, we report that either KP-10 treatment of ERα-negative nonmalignant mammary epithelial MCF10A cells or expression of KISS1R in MCF10A cells induced a mesenchymal phenotype and stimulated invasiveness. Similarly, exogenous expression of KISS1R in ERα-negative SKBR3 breast cancer cells was sufficient to trigger invasion and induced extravasation in vivo. In contrast, KP-10 failed to transactivate EGFR or stimulate invasiveness in the ERα-positive MCF7 and T47D breast cancer cells. This suggested that ERα negatively regulates KISS1R-dependent breast cancer cell migration, invasion, and EGFR transactivation. In support of this, we found that these KP-10-induced effects were ablated upon exogenous expression of ERα in the MDA-MB-231 cells, by down-regulating KISS1R expression. Lastly, we have identified IQGAP1, an actin cytoskeletal binding protein as a novel binding partner of KISS1R, and have shown that KISS1R regulates EGFR transactivation in breast cancer cells in an IQGAP1-dependent manner. Overall, our data strongly suggest that the ERα status of mammary cells dictates whether KISS1R may be a novel clinical target for treating breast cancer metastasis.