Sprouty2, PTEN, and PP2A interact to regulate prostate cancer progression

Multiple endocrine defects in adult-onset Sprouty1/2/4 triple knockout mice

Genes of the Sprouty family (Spry1-4) are feedback inhibitors of receptor tyrosine kinases, especially of Ret and the FGF receptors. As such, they play distinct and overlapping roles in embryo morphogenesis and are considered to be tumor suppressors in adult life. Genetic experiments in mice have defined in great detail the role of these genes during embryonic development, however their function in adult mice is less clearly established. Here we generate adult-onset, whole body Spry1/2/4 triple knockout mice. Tumor incidence in triple mutant mice is comparable to that of wild type littermates of up to one year of age, indicating that Sprouty loss per se is not sufficient to initiate tumorigenesis. On the other hand, triple knockout mice do not gain weight as they age, show less visceral fat, and have lower plasma glucose levels than wild type littermates, despite showing similar food intake and slightly reduced motor function. They also show alopecia, eyelid inflammation, and mild hyperthyroidism. Finally, triple knockout mice present phosphaturia and hypophosphatemia, suggesting exacerbated signaling downstream of FGF23. In conclusion, triple knockout mice develop a series of endocrine abnormalities but do not show increased tumor incidence.

Knockdown of miR-1293 attenuates lung adenocarcinoma angiogenesis via Spry4 upregulation-mediated ERK1/2 signaling inhibition

Lung adenocarcinoma (LUAD) is the most common histologic subtype of lung cancer. Angiogenesis plays a pivotal role in LUAD progression via supplying oxygen and nutrients for cancer cells. Non-coding miR-1293, a significantly up-regulated miRNA in LUAD tissues, can be potentially used as a novel biomarker for predicting the prognosis of LUAD patients. However, little information is available about the function of miR-1293 in LUAD progression especially cancer-induced angiogenesis. Herein, we found that miR-1293 knockdown could obviously attenuate LUAD-induced angiogenesis in vitro and down-regulate two most important pro-angiogenic cytokines VEGF-A and bFGF expression and secretion. Indeed, miR-1293 abrogation inactivated the angiogenesis-promoting ERK1/2 signaling characterized by decreased ERK1/2 phosphorylation and translocation from nucleus to cytoplasm. Next we found that miR-1293 knockdown reactivated the endogenous ERK1/2 pathway inhibitor Spry4 expression and Spry4 perturbance with specific siRNA transfection abolished the inhibition of ERK1/2 pathway and LUAD-induced angiogenesis by miR-1293 knockdown. Finally, with in vivo assay, we found obvious Spry4 up-regulation and VEGF-A, bFGF, ERK1/2 phosphorylation, micro-vessel density marker CD31 expression down-regulation in vivo, respectively. Collectively, these results indicated that miR-1293 knockdown could significantly attenuate LUAD angiogenesis via Spry4-mediated ERK1/2 signaling inhibition, which might be helpful for uncovering more functions of miR-1293 in LUAD and providing experimental basis for possible LUAD therapeutic strategy targeting miR-1293.

Sprouty1 is a broad mediator of cellular senescence

Genes of the Sprouty family (Spry1-4) restrain signaling by certain receptor tyrosine kinases. Consequently, these genes participate in several developmental processes and function as tumor suppressors in adult life. Despite these important roles, the biology of this family of genes still remains obscure. Here we show that Sprouty proteins are general mediators of cellular senescence. Induction of cellular senescence by several triggers in vitro correlates with upregulation of Sprouty protein levels. More importantly, overexpression of Sprouty genes is sufficient to cause premature cellular senescence, via a conserved N-terminal tyrosine (Tyrosine 53 of Sprouty1). Accordingly, fibroblasts from knockin animals lacking that tyrosine escape replicative senescence. In vivo, heterozygous knockin mice display delayed induction of cellular senescence during cutaneous wound healing and upon chemotherapy-induced cellular senescence. Unlike other functions of this family of genes, induction of cellular senescence appears to be independent of activation of the ERK1/2 pathway. Instead, we show that Sprouty proteins induce cellular senescence upstream of the p38 pathway in these in vitro and in vivo paradigms.

Rapid evolution of genes with anti-cancer functions during the origins of large bodies and cancer resistance in elephants

Elephants have emerged as a model system to study the evolution of body size and cancer resistance because, despite their immense size, they have a very low prevalence of cancer. Previous studies have found that duplication of tumor suppressors at least partly contributes to the evolution of anti-cancer cellular phenotypes in elephants. Still, many other mechanisms must have contributed to their augmented cancer resistance. Here, we use a suite of codon-based maximum-likelihood methods and a dataset of 13,310 protein-coding gene alignments from 261 Eutherian mammals to identify positively selected and rapidly evolving elephant genes. We found 496 genes (3.73% of alignments tested) with statistically significant evidence for positive selection and 660 genes (4.96% of alignments tested) that likely evolved rapidly in elephants. Positively selected and rapidly evolving genes are statistically enriched in gene ontology terms and biological pathways related to regulated cell death mechanisms, DNA damage repair, cell cycle regulation, epidermal growth factor receptor (EGFR) signaling, and immune functions, particularly neutrophil granules and degranulation. All of these biological factors are plausibly related to the evolution of cancer resistance. Thus, these positively selected and rapidly evolving genes are promising candidates for genes contributing to elephant-specific traits, including the evolution of molecular and cellular characteristics that enhance cancer resistance.

Redox Regulation of PTEN by Reactive Oxygen Species: Its Role in Physiological Processes

Phosphatase and tensin homolog (PTEN) is a tumor suppressor due to its ability to regulate cell survival, growth, and proliferation by downregulating the PI3K/AKT signaling pathway. In addition, PTEN plays an essential role in other physiological events associated with cell growth demands, such as ischemia-reperfusion, nerve injury, and immune responsiveness. Therefore, recently, PTEN inhibition has emerged as a potential therapeutic intervention in these situations. Increasing evidence demonstrates that reactive oxygen species (ROS), especially hydrogen peroxide (H2O2), are produced and required for the signaling in many important cellular processes under such physiological conditions. ROS have been shown to oxidize PTEN at the cysteine residue of its active site, consequently inhibiting its function. Herein, we provide an overview of studies that highlight the role of the oxidative inhibition of PTEN in physiological processes.

TRAF7-targeted HOXA5 acts as a tumor suppressor in prostate cancer progression and stemness via transcriptionally activating SPRY2 and regulating MEK/ERK signaling

Homeobox A5 (HOXA5), a homeodomain transcription factor, is considered a tumor suppressor in cancer progression; however, its function in prostate cancer (PCa) remains unclear. This study focused on the relevance of HOXA5 in PCa progression. We identified the downregulation of HOXA5 in PCa tissues based on the TCGA database and further verified in 30-paired PCa and adjacent normal tissues. Functional studies revealed that HOXA5 upregulation impaired the stem-like characteristics and malignant behaviors of PCa cells in vitro and in vivo. Mechanistically, HOXA5 was found to be regulated by tumor necrosis factor receptor-associated factor 7 (TRAF7), a putative E3-ubiquitin ligase. We observed that TRAF7 was overexpressed in PCa and subsequently enhanced the degradation of HOXA5 protein via its ubiquitin ligase activity, contributing to the acquisition of an aggressive PCa phenotype. For its downstream mechanism, we demonstrated that sprouty RTK signaling antagonist 2 (SPRY2) served as a downstream target of HOXA5. HOXA5 could directly bind to the SPRY2 promoter, thereby regulating the SPRY2-mediated MEK/ERK signaling pathway. Silencing SPRY2 largely compromised the tumor-suppressive effect of HOXA5 in PCa progression and cancer stemness. Our findings highlight the previously-underappreciated signaling axis of TRAF7-HOXA5-SPRY2, which provides a novel prognostic and therapeutic target for PCa treatment.

Comparison with gastric cancer-associated genes reveals the role of ferroptosis-related genes in eosinophils of asthma patients: A bioinformatic study

Ferroptosis-inducing agents (FIAs) induced lipid-peroxidation-independent ferroptosis in eosinophils, thus ameliorating airway inflammation in asthmatic mice. Differences in ferroptosis-related genes (FerrGs) between eosinophils and cells in which FIAs induce canonical ferroptosis are supposed to contribute to this noncanonical ferroptosis but remain unclear. This study aims to explore these differences. This study used gastric cancer cells (GCCs) in stomach adenocarcinoma as the representative of cells in which FIAs induce canonical ferroptosis. FerrGs in Ferroptosis Database V2 respectively intersected with differentially expressed genes (DEGs) of eosinophils (E-MTAB-4660 dataset) and GCCs (GEPIA2 Stomach adenocarcinoma dataset) to obtain original ferroptosis DEGs (FerrDEGs). Then, they were subjected to Venn analysis to identify FerrDEGs shared by them and FerrDEGs exclusively expressed in eosinophils or GCCs. Identified genes were subjected to functional enrichment analysis, protein-protein interactions analysis, Hub genes analysis, and construction of the LncRNA-mediated ceRNA network. Sixty-six original FerrDEGs in eosinophils and 110 original FerrDEGs in GCCs were obtained. Venn analysis identified that eosinophils and GCCs shared 19 FerrDEGs that presented opposite expression directions and were involved in the ferroptosis pathway. Four upregulated and 20 downregulated FerrDEGs were exclusively expressed in eosinophils and GCCs, respectively. The former were enriched only in glycerolipid metabolism, while the latter were not enriched in pathways. Forty downregulated and 68 upregulated FerrDEGs were solely expressed in eosinophils and GCCs, respectively. The former was associated with the FoxO signaling pathway; the latter was related to glutathione metabolism and they were all implicated in autophagy. PPI analysis shows that the top 10 Hub genes of 66 original FerrDEGs and 44 exclusive FerrDEGs in eosinophils shared 9 genes (STAT3, NFE2L2, MAPK8, PTEN, MAPK3, TLR4, SIRT1, BECN1, and PTGS2) and they were also involved in the FoxO signaling pathway and autophagy pathway. Among them, PTEN is involved in forming a ceRNA network containing 3 LncRNAs, 3 miRNAs and 3 mRNAs. In contrast to FerrGs in cells in which FIAs induce canonical ferroptosis, the FerrGs in eosinophils differ in expression and in the regulation of ferroptosis, FoxO signaling pathway, and autophagy. It lays the groundwork for targeted induction of eosinophils lipid-peroxidation-independent ferroptosis in asthma.

Sprouty 4 suppresses glioblastoma invasion by inhibiting ERK phosphorylation and ETS-1-induced matrix metalloproteinase-9

BACKGROUND

Glioblastoma multiforme (GBM) is the most malignant glioma with highly aggressive behavior and the worst prognosis. Many efforts have been made to develop new drugs and improve the patient's survival, but the effects are not satisfactory. Here we aimed to evaluate the clinical significance and tumor-repressive function of Sprouty4 (SPRY4) in GBM.

METHODS

In our study, we detected the expression of SPRY4 in 109 GBM patients and 12 pairs of GBM tissues and the corresponding adjacent tissues. χ² test was applied to analyze the association between SPRY4 expression and the clinicopathological factors. The prognostic significances were evaluated with univariate and multivariate analyses, which were carried out by the Kaplan-Meier method and the Cox-regression proportional hazards model, respectively. With in-vitro experiments, we investigated the tumor-suppressing function of SPRY4 in GBM invasion and investigated the underlying mechanism.

RESULTS

SPRY4 mRNAs in GBMs were significantly lower than those in adjacent brain tissues. We demonstrated that SPRY4 expression could predict the favorable prognosis of GBM, and SPRY4 was an independent favorable prognostic factor of GBM. SPRY4 repressed GBM invasion via inhibiting ERK phosphorylation; therefore, suppressing ETS-1-induced MMP9 expression.

CONCLUSIONS

SPRY4 was an independent favorable prognostic factor of GBM, and it could suppress GBM invasion by ERK-ETS-MMP9 axis. Our results indicated that SPRY4 may be a promising drug target of GBM and SPRY4 detection could stratify patients with low SPRY4 expression who may benefit from anti-FGFR therapy.

Cyclocreatine Suppresses Creatine Metabolism and Impairs Prostate Cancer Progression

Prostate cancer is the second most common cause of cancer mortality in men worldwide. Applying a novel genetically engineered mouse model (GEMM) of aggressive prostate cancer driven by deficiency of the tumor suppressors PTEN and Sprouty2 (SPRY2), we identified enhanced creatine metabolism as a central component of progressive disease. Creatine treatment was associated with enhanced cellular basal respiration in vitro and increased tumor cell proliferation in vivo. Stable isotope tracing revealed that intracellular levels of creatine in prostate cancer cells are predominantly dictated by exogenous availability rather than by de novo synthesis from arginine. Genetic silencing of creatine transporter SLC6A8 depleted intracellular creatine levels and reduced the colony-forming capacity of human prostate cancer cells. Accordingly, in vitro treatment of prostate cancer cells with cyclocreatine, a creatine analog, dramatically reduced intracellular levels of creatine and its derivatives phosphocreatine and creatinine and suppressed proliferation. Supplementation with cyclocreatine impaired cancer progression in the PTEN- and SPRY2-deficient prostate cancer GEMMs and in a xenograft liver metastasis model. Collectively, these results identify a metabolic vulnerability in prostate cancer and demonstrate a rational therapeutic strategy to exploit this vulnerability to impede tumor progression.

SIGNIFICANCE

Enhanced creatine uptake drives prostate cancer progression and confers a metabolic vulnerability to treatment with the creatine analog cyclocreatine.

Signal Transduction Regulators in Axonal Regeneration

Intracellular signal transduction in response to growth factor receptor activation is a fundamental process during the regeneration of the nervous system. In this context, intracellular inhibitors of neuronal growth factor signaling have become of great interest in the recent years. Among them are the prominent signal transduction regulators Sprouty (SPRY) and phosphatase and tensin homolog deleted on chromosome 10 (PTEN), which interfere with major signaling pathways such as extracellular signal-regulated kinase (ERK) or phosphoinositide 3-kinase (PI3K)/Akt in neurons and glial cells. Furthermore, SPRY and PTEN are themselves tightly regulated by ubiquitin ligases such as c-casitas b-lineage lymphoma (c-CBL) or neural precursor cell expressed developmentally down-regulated protein 4 (NEDD4) and by different microRNAs (miRs) including miR-21 and miR-222. SPRY, PTEN and their intracellular regulators play an important role in the developing and the lesioned adult central and peripheral nervous system. This review will focus on the effects of SPRY and PTEN as well as their regulators in various experimental models of axonal regeneration in vitro and in vivo. Targeting these signal transduction regulators in the nervous system holds great promise for the treatment of neurological injuries in the future.

CircIL4R activates the PI3K/AKT signaling pathway via the miR-761/TRIM29/PHLPP1 axis and promotes proliferation and metastasis in colorectal cancer

BACKGROUND

Accumulating studies have revealed that aberrant expression of circular RNAs (circRNAs) is widely involved in the tumorigenesis and progression of malignant cancers, including colorectal cancer (CRC). Nevertheless, the clinical significance, levels, features, biological function, and molecular mechanisms of novel circRNAs in CRC remain largely unexplored.

METHODS

CRC-related circRNAs were identified through bioinformatics analysis and verified in clinical specimens by qRT-PCR and in situ hybridization (ISH). Then, in vitro and in vivo experiments were performed to determine the clinical significance of, functional roles of, and clinical characteristics associated with circIL4R in CRC specimens and cells. Mechanistically, RNA pull-down, fluorescence in situ hybridization (FISH), luciferase reporter, and ubiquitination assays were performed to confirm the underlying mechanism of circIL4R.

RESULTS

CircIL4R was upregulated in CRC cell lines and in sera and tissues from CRC patients and was positively correlated with advanced clinicopathological features and poor prognosis. Functional experiments demonstrated that circIL4R promotes CRC cell proliferation, migration, and invasion via the PI3K/AKT signaling pathway. Mechanistically, circIL4R was regulated by TFAP2C and competitively interacted with miR-761 to enhance the expression of TRIM29, thereby targeting PHLPP1 for ubiquitin-mediated degradation to activate the PI3K/AKT signaling pathway and consequently facilitate CRC progression.

CONCLUSIONS

Our findings demonstrate that upregulation of circIL4R plays an oncogenic role in CRC progression and may serve as a promising diagnostic and prognostic biomarker for CRC detection and as a potential therapeutic target for CRC treatment.

Crosstalk between miRNA and PI3K/AKT/mTOR signaling pathway in cancer

Phosphoinositide-3 kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway is one of the most important proliferative signaling pathways with critical undeniable function in various aspects of cancer initiation/progression, including proliferation, apoptosis, metastasis, angiogenesis, and drug resistance. On the other hand, numerous genetic alterations in the key genes involved in the PI3K/AKT/mTOR signaling pathway have been identified in multiple solid and hematological tumors. In addition, accumulating recent evidences have demonstrated a reciprocal interaction between this signaling pathway and microRNAs, a large group of small non-coding RNAs. Therefore, in this review, it was attempted to discuss about the interaction between key components of PI3K/AKT/mTOR signaling pathway with various miRNAs and their importance in cancer biology.

Silencing miRNA-1297 suppresses the invasion and migration of prostate cancer cells via targeting modulation of PTEN and blocking of the AKT/ERK pathway

Phosphatase and tensin homolog (PTEN) loss is a major contributing factor of prostate cancer (PC). miRNA-1297 was reported to serve role in various cancer types; however, the potential roles of miRNA-1297 in PC had not been investigated. In the present study, tumor and adjacent tissues were collected from patients with PC. The gene expression level of miRNA-1297 was measured via polymerase chain reaction. Results indicated that the miRNA-1297 was overexpressed in tumor tissues from PC patients and in PC cell lines. miRNA-1297 also contributed toward the progression of PC. PTEN was confirmed as the direct target of miRNA-1297 and bound with miRNA-1297 via four binding sites. The miRNA-1297 level was negatively associated with the PTEN level. Silencing miRNA-1297 or overexpression of PTEN significantly inhibited the cell migration and invasion. In addition, the AKT/ERK pathway was also inhibited following silencing of miRNA-1297 or overexpression of PTEN. Taken together, the results indicated that silencing miRNA-1297 exerted inhibitory effects on the invasion and migration of PC cells via modulating PTEN and blocking of the AKT/ERK pathway. The results of the present study provided a novel strategy for treatment of prostate cancer cells.

Human Schlafen 5 Inhibits Proliferation and Promotes Apoptosis in Lung Adenocarcinoma via the PTEN/PI3K/AKT/mTOR Pathway

BACKGROUND

Human Schlafen 5 (SLFN5) is reported to inhibit or promote the proliferation of several specific types of cancer cells by our lab and other researchers. We are curious about its implications in lung adenocarcinoma (LUAC), a malignant tumor with a high incidence rate and high mortality.

METHOD

Lentiviral stable transfections of SLFN5-specific shRNA for knockdown and SLFN5 full-length coding sequence for overexpression were performed in LUAC cell for proliferation analysis in vitro and in vivo in nude mice. Clinical LUAC samples were collected for immunohistochemical analysis of SLFN5 protein levels.

RESULTS

We found that knockdown of endogenous SLFN5 upregulates cancer cell proliferation while inhibiting apoptosis. Besides, SLFN5 inhibition on proliferation was also observed in a nude mouse xenograft model. In contrast, overexpression of exogenous SLFN5 inhibited cell proliferation in vitro and in vivo and promoted apoptosis. As to the signaling pathway, we found phosphatase and tensin homolog on chromosome 10 (PTEN) was positively regulated by SLFN5, while its downstream signaling pathway AKT/mammalian target of rapamycin (mTOR) was inhibited. Moreover, compared with adjacent normal tissues, SLFN5 protein levels were markedly decreased in lung adenocarcinoma tissues. In conclusion, these suggest that human SLFN5 plays inhibitory roles in LUAC progression through the PTEN/PI3K/AKT/mTOR pathway, providing a potential target for developing drugs for lung cancer therapy in the future.

Chronic exposure to microcystin-LR increases the risk of prostate cancer and induces malignant transformation of human prostate epithelial cells

Microcystins-LR (MC-LR) acts as a possible carcinogen for humans and causes a serious risk to public environmental health. The current study aimed to evaluate the interaction between MC-LR exposure and prostate cancer development and elucidate the underlying mechanism. In this study, mice were exposed to MC-LR at various doses for 180 days. MC-LR was able to induce the progression of prostatic intraepithelial neoplasia (PIN) and microinvasion. Furthermore, MC-LR notably increased angiogenesis and susceptibility to prostate cancer in vivo. In vitro, over 25 weeks of MC-LR exposure, normal human prostate epithelial (RWPE-1) cells increased secretion of matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9), and colony formation, features typical for cancer cells. These MC-LR-transformed prostate epithelial cells displayed increased expression of forkhead box M1 (FOXM1) and cyclooxygenase-2 (COX-2); abrogation of FOXM1 or COX-2 activity by specific inhibitors could abolish the invasion and migration of MC-LR-treated cells. In conclusion, we have provided compelling evidence demonstrating the induction of a malignant phenotype in human prostate epithelial cells and the in vivo development of prostate cancer by exposure to MC-LR, which might be a potential tumor promoter in the progression of prostate cancer.

In vivo CRISPR/Cas9 knockout screen: TCEAL1 silencing enhances docetaxel efficacy in prostate cancer

Docetaxel chemotherapy in metastatic prostate cancer offers only a modest survival benefit because of emerging resistance. To identify candidate therapeutic gene targets, we applied a murine prostate cancer orthograft model that recapitulates clinical invasive prostate cancer in a genome-wide CRISPR/Cas9 screen under docetaxel treatment pressure. We identified 17 candidate genes whose suppression may enhance the efficacy of docetaxel, with transcription elongation factor A-like 1 (Tceal1) as the top candidate. TCEAL1 function is not fully characterised; it may modulate transcription in a promoter dependent fashion. Suppressed TCEAL1 expression in multiple human prostate cancer cell lines enhanced therapeutic response to docetaxel. Based on gene set enrichment analysis from transcriptomic data and flow cytometry, we confirmed that loss of TCEAL1 in combination with docetaxel leads to an altered cell cycle profile compared with docetaxel alone, with increased subG1 cell death and increased polyploidy. Here, we report the first in vivo genome-wide treatment sensitisation CRISPR screen in prostate cancer, and present proof of concept data on TCEAL1 as a candidate for a combinational strategy with the use of docetaxel.

18F-Fluciclovine PET metabolic imaging reveals prostate cancer tumour heterogeneity associated with disease resistance to androgen deprivation therapy

BACKGROUND

Prostate cancer is highly prevalent worldwide. Androgen deprivation therapy (ADT) remains the treatment of choice for incurable prostate cancer, but majority of patients develop disease recurrence following ADT. There is therefore an urgent need for early detection of treatment resistance.

METHODS

Isogenic androgen-responsive (CWR22Res) and castration-resistant (22Rv1) human prostate cancer cells were implanted into the anterior lobes of the prostate in CD-1 Nu mice to generate prostate orthografts. Castrated mice bearing CWR22Res and 22Rv1 orthografts mimic clinical prostate cancer following acute and chronic ADT, respectively. 18F-Fluciclovine (1-amino-3-fluorocyclobutane-1-carboxylic acid) with a radiochemical purity of > 99% was produced on a FASTlab synthesiser. Ki67 staining in endpoint orthografts was studied. Western blot, quantitative RT-PCR and next-generation sequencing transcriptomic analyses were performed to assess the expression levels of amino acid transporters (including LAT1 and ASCT2, which have been implicated for Fluciclovine uptake). Longitudinal metabolic imaging with 18F-Fluciclovine-based positron emission tomography (PET) was performed to study tumour response following acute and chronic ADT.

RESULTS

Both immunohistochemistry analysis of endpoint prostate tumours and longitudinal 18F-Fluciclovine imaging revealed tumour heterogeneity, particularly following ADT, with in vivo 18F-Fluciclovine uptake correlating to viable cancer cells in both androgen-proficient and castrated environment. Highlighting tumour subpopulation following ADT, both SUVpeak and coefficient of variation (CoV) values of 18F-Fluciclovine uptake are consistent with tumour heterogeneity revealed by immunohistochemistry. We studied the expression of amino acid transporters (AATs) for 18F-Fluciclovine, namely LAT1 (SLC7A5 and SLC3A2) and ASCT2 (SLC1A5). SLC7A5 and SLC3A2 were expressed at relatively high levels in 22Rv1 castration-resistant orthografts following chronic ADT (modelling clinical castration-resistant disease), while SLC1A5 was preferentially expression in CWR22Res tumours following acute ADT. Additional AATs such as SLC43A2 (LAT4) were shown to be upregulated following chronic ADT by transcriptomic analysis; their role in Fluciclovine uptake warrants investigation.

CONCLUSION

We studied in vivo 18F-Fluciclovine uptake in human prostate cancer orthograft models following acute and chronic ADT. 18F-Fluciclovine uptakes highlight tumour heterogeneity that may explain castration resistance and can be exploited as a clinical biomarker.

GRB10 sustains AR activity by interacting with PP2A in prostate cancer cells

Prostate cancer (PCa) progression is driven by androgen receptor (AR) signaling. Unfortunately, androgen-deprivation therapy and the use of even more potent AR pathway inhibitors (ARPIs) cannot bring about a cure. ARPI resistance (ie, castration-resistant PCa, CRPC) will inevitably develop. Previously, we demonstrated that GRB10 is an AR transcriptionally repressed gene that functionally contributes to CRPC development and ARPI resistance. GRB10 expression is elevated prior to CRPC development in our patient-derived xenograft models and is significantly upregulated in clinical CRPC samples. Here, we analyzed transcriptomic data from GRB10 knockdown in PCa cells and found that AR signaling is downregulated. While the mRNA expression of AR target genes decreased upon GRB10 knockdown, AR expression was not affected at the mRNA or protein level. We further found that phosphorylation of AR serine 81 (S81), which is critical for AR transcriptional activity, is decreased by GRB10 knockdown and increased by its overexpression. Luciferase assay using GRB10-knockdown cells also indicate reduced AR activity. Immunoprecipitation coupled with mass spectrometry revealed an interaction between GRB10 and the PP2A complex, which is a known phosphatase of AR. Further validations and analyses showed that GRB10 binds to the PP2Ac catalytic subunit with its PH domain. Mechanistically, GRB10 knockdown increased PP2Ac protein stability, which in turn decreased AR S81 phosphorylation and reduced AR activity. Our findings indicate a reciprocal feedback between GRB10 and AR signaling, implying the importance of GRB10 in PCa progression.

Sprouty2 Inhibits Migration and Invasion of Fibroblast-Like Synoviocytes in Rheumatoid Arthritis by Down-regulating ATF2 Expression and Phosphorylation

Activating transcription factor 2(ATF2), a transcription factor belonging to the AP-1 family, plays an important role in inflammation. However, its biological functions and underlying molecular mechanisms in rheumatoid arthritis (RA) remain unclear. Western blot and immunohistochemistry were used to identify the expression of ATF2 and Sprouty2(SPRY2) in RA synovial tissues. SW982 cells were stimulated by TNF-α to establish an in vitro RA fibroblast-like synoviocyte (RA-FLS) model. Transwell and monolayer wound-healing were used to detect cell migration and invasion. RNA interference (si-ATF2) and adenovirus vector (Ad-SPRY2) methods were employed to manipulate ATF2 or SPRY2 expression in SW982 cells. The protein expression and phosphorylation levels in SW982 cells were evaluated by western blot. ATF2 expression and phosphorylation were upregulated in the RA synovial tissues. In RA-FLS model, ATF2 expression and phosphorylation were increased in a time-dependent manner. ATF2 knockdown inhibited the migration and invasion of RA-FLS model, reducing the inflammatory factors, which was consistent with the influence on cell behaviors caused by SPRY2 overexpression. Moreover, SPRY2 overexpression inhibited the TNF-α-induced phosphorylation of ERK and ATF2 in SW982 cells. The high expression and phosphorylation of ATF2 promoted migration and invasion of RA-FLSs. SPRY2 might inhibited the inflammatory responses of RA-FLSs via suppressing ERK-ATF2 pathway.

Loss of Spry1 reduces growth of BRAFV600-mutant cutaneous melanoma and improves response to targeted therapy

Mitogen-activated protein kinase (MAPK) pathway activation is a central step in BRAF^V600-mutant cutaneous melanoma (CM) pathogenesis. In the last years, Spry1 has been frequently described as an upstream regulator of MAPK signaling pathway. However, its specific role in BRAF^V600-mutant CM is still poorly defined. Here, we report that Spry1 knockdown (Spry1^KO) in three BRAF^V600-mutant CM cell lines markedly induced cell cycle arrest and apoptosis, repressed cell proliferation in vitro, and impaired tumor growth in vivo. Furthermore, our findings indicated that Spry1^KO reduced the expression of several markers of epithelial–mesenchymal transition, such as MMP-2 both in vitro and in vivo. These effects were associated with a sustained and deleterious phosphorylation of ERK1/2. In addition, p38 activation along with an increase in basal ROS levels were found in Spry1^KO clones compared to parental CM cell lines, suggesting that BRAF^V600-mutant CM may restrain the activity of Spry1 to avoid oncogenic stress and to enable tumor growth. Consistent with this hypothesis, treatment with the BRAF inhibitor (BRAFi) vemurafenib down-regulated Spry1 levels in parental CM cell lines, indicating that Spry1 expression is sustained by the MAPK/ERK signaling pathway in a positive feedback loop that safeguards cells from the potentially toxic effects of ERK1/2 hyperactivation. Disruption of this feedback loop rendered Spry1^KO cells more susceptible to apoptosis and markedly improved response to BRAFi both in vitro and in vivo, as a consequence of the detrimental effect of ERK1/2 hyperactivation observed upon Spry1 abrogation. Therefore, targeting Spry1 might offer a treatment strategy for BRAF^V600-mutant CM by inducing the toxic effects of ERK-mediated signaling.

Activation of β-Catenin Cooperates with Loss of Pten to Drive AR-Independent Castration-Resistant Prostate Cancer

Inhibition of the androgen receptor (AR) is the main strategy to treat advanced prostate cancers. AR-independent treatment-resistant prostate cancer is a major unresolved clinical problem. Patients with prostate cancer with alterations in canonical WNT pathway genes, which lead to β-catenin activation, are refractory to AR-targeted therapies. Here, using clinically relevant murine prostate cancer models, we investigated the significance of β-catenin activation in prostate cancer progression and treatment resistance. β-Catenin activation, independent of the cell of origin, cooperated with Pten loss to drive AR-independent castration-resistant prostate cancer. Prostate tumors with β-catenin activation relied on the noncanonical WNT ligand WNT5a for sustained growth. WNT5a repressed AR expression and maintained the expression of c-Myc, an oncogenic effector of β-catenin activation, by mediating nuclear localization of NFκBp65 and β-catenin. Overall, WNT/β-catenin and AR signaling are reciprocally inhibited. Therefore, inhibiting WNT/β-catenin signaling by limiting WNT secretion in concert with AR inhibition may be useful for treating prostate cancers with alterations in WNT pathway genes. SIGNIFICANCE: Targeting of both AR and WNT/β-catenin signaling may be required to treat prostate cancers that exhibit alterations of the WNT pathway.

Repurposing screen identifies mebendazole as a clinical candidate to synergise with docetaxel for prostate cancer treatment

BACKGROUND

Docetaxel chemotherapy in prostate cancer has a modest impact on survival. To date, efforts to develop combination therapies have not translated into new treatments. We sought to develop a novel therapeutic strategy to tackle chemoresistant prostate cancer by enhancing the efficacy of docetaxel.

METHODS

We performed a drug-repurposing screen by using murine-derived prostate cancer cell lines driven by clinically relevant genotypes. Cells were treated with docetaxel alone, or in combination with drugs (n = 857) from repurposing libraries, with cytotoxicity quantified using High Content Imaging Analysis.

RESULTS

Mebendazole (an anthelmintic drug that inhibits microtubule assembly) was selected as the lead drug and shown to potently synergise docetaxel-mediated cell killing in vitro and in vivo. Dual targeting of the microtubule structure was associated with increased G2/M mitotic block and enhanced cell death. Strikingly, following combined docetaxel and mebendazole treatment, no cells divided correctly, forming multipolar spindles that resulted in aneuploid daughter cells. Liposomes entrapping docetaxel and mebendazole suppressed in vivo prostate tumour growth and extended progression-free survival.

CONCLUSIONS

Docetaxel and mebendazole target distinct aspects of the microtubule dynamics, leading to increased apoptosis and reduced tumour growth. Our data support a new concept of combined mebendazole/docetaxel treatment that warrants further clinical evaluation.

Simultaneous Knockdown of Sprouty2 and PTEN Promotes Axon Elongation of Adult Sensory Neurons

Sprouty2 (Spry2) and phosphatase and tensin homolog deleted on chromosome 10 (PTEN) are both well-established regulators of receptor tyrosine kinase (RTK) signaling, and knockdown of Spry2 or PTEN enhances axon regeneration of dorsal root ganglia (DRG) neurons. The major role of Spry2 is the inhibition of the rat sarcoma RAS/extracellular signal-regulated kinase (ERK) pathway, whereas PTEN acts mainly as an inhibitor of the phosphoinositide 3-kinase (PI3K)/Akt pathway. In non-neuronal cells, Spry2 increases the expression and activity of PTEN, and PTEN enhances the amount of Spry2 by the inhibition of the microRNA-21 (miR-21) that downregulates Spry2. Applying dissociated DRG neuron cultures from wild-type (WT) or Spry2 deficient mice, we demonstrate that PTEN protein was reduced after 72 h during rapid axonal outgrowth on the laminin substrate. Furthermore, PTEN protein was decreased in DRG cultures obtained from homozygous Spry2−/− knockout mice. Vice versa, Spry2 protein was reduced by PTEN siRNA in WT and heterozygous Spry2+/− neurons. Knockdown of PTEN in DRG cultures obtained from homozygous Spry2−/− knockout mice promoted axon elongation without increasing axonal branching. Activation of Akt, but not ERK, was stronger in response to PTEN knockdown in homozygous Spry2−/− DRG neurons than in WT neurons. Together, our study confirms the important role of the signaling modulators Spry2 and PTEN in axon growth of adult DRG neurons. Both function as endogenous inhibitors of neuronal growth factor signaling and their simultaneous knockdown promotes axon elongation more efficiently than the single knockdown of each inhibitor. Furthermore, Spry2 and PTEN are reciprocally downregulated in adult DRG neuron cultures. Axon growth is influenced by multiple factors and our results demonstrate that the endogenous inhibitors of axon growth, Spry2 and PTEN, are co-regulated in adult DRG neuron cultures. Together, our data demonstrate that combined approaches may be more useful to improve nerve regeneration than targeting one single inhibitor of axon growth.

Sprouty4 correlates with favorable prognosis in perihilar cholangiocarcinoma by blocking the FGFR-ERK signaling pathway and arresting the cell cycle

Background

Perihilar cholangiocarcinoma (PHCC) is the most common subtype of cholangiocarcinoma(CCA). We previously investigated the expression pattern of Sprouty(SPRY) in intrahepatic cholangiocarcinoma(ICC), but the expression and clinical significance of SPRY family members in PHCC are still unknown.

Methods

The expression of SPRY family members(SPRY1-4) was detected in different subtypes of CCA and corresponding adjacent tissues. SPRY4 expression in 142 cases of PHCC was detected by immunohistochemistry, and its clinical significance was evaluated using univariate and multivariate analyses. The functions of SPRY4 in the FGFR-induced proliferation and migration of PHCC cells were investigated through in vitro and in vivo experiments. We further investigated the effects and mechanisms of SPRY4 on FGFR-induced ERK phosphorylation and cell cycle distribution in the presence of FGFR and ERK inhibitors.

Findings

SPRY4 was the only SPRY family member associated with PHCC prognosis, and it was identified as an independent factor predicting favorable prognosis. In PHCC, SPRY4 expression was extensively associated with FGFR2, and its expression can be induced by ectopic FGFR2 activation. Through in vitro and in vivo experiments, we demonstrated that SPRY4 suppressed FGFR-induced proliferation and migration by inhibiting ERK phosphorylation. Moreover, SPRY4 knockdown was shown to decrease the percentage of cells in the G1 phase and promote the percentage of cells in the S and G2/M phases by increasing cyclin D1 expression, which also required FGFR-induced ERK phosphorylation.

Interpretation

High expression of SPRY4 was an independent biomarker of favorable prognosis in PHCC. SPRY4 expression can be induced by ectopic FGFR2 activation in PHCC. SPRY4 arrested the cell cycle at G1 phase and suppressed FGFR-induced proliferation and migration by inhibiting ERK phosphorylation, indicating that SPRY4 may be a potential therapeutic target in PHCC.

Activation of PTEN by inhibition of TRPV4 suppresses colon cancer development

Transient receptor potential vanilloid type 4 (TRPV4) is a Ca²⁺-permeable cation channel that is known to be an osmosensor and thermosensor. Currently, limited evidence shows that TRPV4 plays opposite roles in either promoting or inhibiting cancer development in different cancer types. Furthermore, the precise biological functions and the underlying mechanisms of TRPV4 in carcinogenesis are still poorly understood. In this study, we demonstrated that TRPV4 is upregulated in colon cancer and associated with poor prognosis. Contrary to the reported cell death-promoting activity of TRPV4 in certain cancer cells, TRPV4 positively regulates cell survival in human colon cancer in vitro and in vivo. Inhibition of TRPV4 affects the cell cycle progression from the G1 to S phase through modulating the protein expression of D-type cyclins. Apoptosis and autophagy induced by TRPV4 silencing attenuate cell survival and potentiate the anticancer efficacy of chemotherapeutics against colon cancer cells. In addition, PTEN is activated by inhibition of TRPV4 as indicated by the dephosphorylation and increased nuclear localization. Knockdown of PTEN significantly abrogates TRPV4 silencing induced growth inhibition and recovers the capability of clonogenicity, as well as reduced apoptosis in colon cancer cells. Thus, PTEN regulates the antigrowth effects induced by TRPV4 inhibition through both phosphatase-dependent and independent mechanisms. In conclusion, inhibition of TRPV4 suppresses colon cancer development via activation of PTEN pathway. This finding suggests that downregulation of TPRV4 expression or activity would conceivably constitute a novel approach for the treatment of human colon cancer.

The Sprouty/Spred family as tumor suppressors: Coming of age

The Ras/Raf/ERK pathway is one of the most frequently dysregulated signaling pathways in various cancers. In some such cancers, Ras and Raf are hotspots for mutations, which cause continuous activation of this pathway. However, in some other cancers, it is known that negative regulators of the Ras/Raf/ERK pathway are responsible for uncontrolled activation. The Sprouty/Spred family is broadly recognized as important negative regulators of the Ras/Raf/ERK pathway, and its expression is downregulated in many malignancies, leading to hyperactivation of the Ras/Raf/ERK pathway. After the discovery of this family, intensive research investigated the mechanism by which it suppresses the Ras/Raf/ERK pathway and its roles in developmental and pathophysiological processes. In this review, we discuss the complicated roles of the Sprouty/Spred family in tumor initiation, promotion, and progression and its future therapeutic potential.

Targeting mitosis exit: A brake for cancer cell proliferation

The transition from mitosis to interphase, referred to as mitotic exit, is a critical mitotic process which involves activation and inactivation of multiple mitotic kinases and counteracting protein phosphatases. Loss of mitotic exit checkpoints is a common feature of cancer cells, leading to mitotic dysregulation and confers cancer cells with oncogenic characteristics, such as aberrant proliferation and microtubule-targeting agent (MTA) resistance. Since MTA resistance results from cancer cells prematurely exiting mitosis (mitotic slippage), blocking mitotic exit is believed to be a promising anticancer strategy. Moreover, based on this theory, simultaneous inhibition of mitotic exit and additional cell cycle phases would likely achieve synergistic antitumor effects. In this review, we divide the molecular regulators of mitotic exit into four categories based on their different regulatory functions: 1) the anaphase-promoting complex/cyclosome (APC/C, a ubiquitin ligase), 2) cyclin B, 3) mitotic kinases and phosphatases, 4) kinesins and microtubule-binding proteins. We also review the regulators of mitotic exit and propose prospective anticancer strategies targeting mitotic exit, including their strengths and possible challenges to their use.

Dyrk1A promotes the proliferation, migration and invasion of fibroblast-like synoviocytes in rheumatoid arthritis via down-regulating Spry2 and activating the ERK MAPK pathway

Fibroblast-like synoviocytes (FLSs) play an essential role in rheumatoid arthritis (RA) by promoting synovitis, pannus growth and cartilage/bone destruction. Increased proliferation, migration and invasion of FLSs greatly contribute to RA initiation and progression. Dual-specificity tyrosine-regulated kinase 1A (Dyrk1A), a serine/threonine kinase, regulates MAPK pathway activation, and governs the proliferation and differentiation of neuronal progenitor cells and cancer cells. Till now, the expression and possible function of Dyrk1A in RA FLSs have not been explored. In this study, we detected an increased expression of Dyrk1A both in the synovial tissues of RA patients and in a TNF-α-induced FLSs activation model. CCK-8 and Edu assays revealed that Dyrk1A knockdown inhibited TNF-α-induced FLSs proliferation. Moreover, inhibiting Dyrk1A expression apparently prevented the migration and invasion capability of FLSs accompanied by a decreased MMP-3 and -9 expression. To investigate the molecular mechanism through which Dyrk1A modulates FLSs activities, we evaluated the effects of Dyrk1A on Spry2, a negativity modulator of ERK MAPK pathway. Western blot assay demonstrated that Dyrk1A silencing significantly increased Spry2 expression and suppressed the phosphorylation of ERK in TNF-α-treated FLSs. Taken together, our results indicated that Dyrk1A might promote FLSs proliferation, migration and invasion by suppressing Spry2 expression and activating the ERK MAPK signaling pathway in RA.

A potential clinical significance of DAB2IP and SPRY2 transcript variants in prostate cancer

Deregulation of key signaling pathways is one of the primary phenomena in carcinogenesis. DAB2IP and SPRY2 are regulatory elements, which act as feedback inhibitors of receptor tyrosine kinases signaling in mitogen-activated protein kinase pathway. These elements have also been implicated in the pathophysiology of cancer. Therefore, this study is aimed to investigate the expression of all known splice variants of DAB2IP and SPRY2 in prostate tissue. Fresh Prostate tissue samples (50 prostate cancer/ matched normal tissue and 30 BPH) were collected and total RNA was extracted followed by cDNA synthesis. The expression of DAB2IP and SPRY2 transcript variants were evaluated using RT-PCR and quantitative Real-time PCR. The results indicated significant down-regulation of DAB2IP transcript variant 1 in cancerous tissues compared to paired normal tissues (P = 0.001) as well as SPRY2 transcript variant 2 in cancerous tissues in comparison with the normal counterparts and BPH (P = 0.008 and P = 0.025, respectively). In addition, there was a significant negative correlation between DAB2IP.1 and SPRY2.2 expression with PSA levels in prostate cancer (P = 0.039 ρ =-0.24 and P = 0.045 ρ =-0.3, respectively). Interestingly, the down-regulation of DAB2IP.1 mRNA and SPRY2.2 mRNA was positively correlated in tumor samples (P = 0.002 ρ = 0.434). For the first time, this experiment highlights the deregulation of DAB2IP and SPRY2 transcript variants in human prostate cancer. The present study confirms and extends the previous reports through indicating transcript-specific down-regulation and significant association of DAB2IP and SPRY2 in prostate tumorigenesis.

Synergistic Interaction of HOXB13 and CIP2A Predisposes to Aggressive Prostate Cancer

PURPOSE

Distinguishing aggressive prostate cancer from indolent disease improves personalized treatment. Although only few genetic variants are known to predispose to aggressive prostate cancer, synergistic interactions of HOXB13 G84E high-risk prostate cancer susceptibility mutation with other genetic loci remain unknown. The purpose of this study was to examine the interplay of HOXB13 rs138213197 (G84E) and CIP2A rs2278911 (R229Q) germline variants on prostate cancer risk.

EXPERIMENTAL DESIGN

Genotyping was done in Finnish discovery cohort (n = 2,738) and validated in Swedish (n = 3,132) and independent Finnish (n = 1,155) prostate cancer cohorts. Expression pattern analysis was followed by functional studies in prostate cancer cell models.

RESULTS

Interplay of HOXB13 (G84E) and CIP2A (R229Q) variants results in highest observed inherited prostate cancer risk (OR, 21.1; P = 0.000024). In addition, this synergism indicates a significant association of HOXB13 T and CIP2A T dual carriers with elevated risk for high Gleason score (OR, 2.3; P = 0.025) and worse prostate cancer-specific life expectancy (HR, 3.9; P = 0.048), and it is linked with high PSA at diagnosis (OR, 3.30; P = 0.028). Furthermore, combined high expression of HOXB13-CIP2A correlates with earlier biochemical recurrence. Finally, functional experiments showed that ectopic expression of variants stimulates prostate cancer cell growth and migration. In addition, we observed strong chromatin binding of HOXB13 at CIP2A locus and revealed that HOXB13 functionally promotes CIP2A transcription. The study is limited to retrospective Nordic cohorts.

CONCLUSIONS

Simultaneous presence of HOXB13 T and CIP2A T alleles confers for high prostate cancer risk and aggressiveness of disease, earlier biochemical relapse, and lower disease-specific life expectancy. HOXB13 protein binds to CIP2A gene and functionally promotes CIP2A transcription.

Sprouty2 suppresses progression and correlates to favourable prognosis of intrahepatic cholangiocarcinoma via antagonizing FGFR2 signalling

Fibroblast growth factor receptor 2 (FGFR2) was demonstrated to correlate to the progression and prognosis of intrahepatic cholangiocarcinoma (ICC) by numerous evidences. However, as a well‐recognized suppressor of FGFR2 signalling, the clinical significance of Sprouty (SPRY) family of ICC has not been investigated. In our study, the expressions of SPRY1‐4 in 20 pairs of fresh tumour tissues were detected with qPCR, and in 108 cases of paraffin‐embedded tissues with immunohistochemistry. The prognostic value of SPRY family in ICC was estimated with univariate analysis and multivariate analysis. As a result, SPRY2 was identified as an independent prognostic biomarker predicting favourable prognosis of ICC. High SPRY2 expression was correlated with good differentiation of ICC. With silencing SPRY2 expression, we demonstrated that SPRY2 could suppress FGFR2‐induced ERK phosphorylation, migration, invasion and epithelial‐mesenchymal transition (EMT) under FGF1 stimulation. By overexpressing SPRY2‐wide type or SPRY2‐Y55F, the tyrosine‐55 of SPRY2 was demonstrated to be essential in suppressing ERK phosphorylation, tumour invasion and EMT of ICC cells. In conclusion, SPRY2 was correlated with favourable prognosis of ICC via suppressing FGFR2‐induced ERK phosphorylation, invasion and EMT. The phosphorylation of SPRY2‐Y55 was required in this tumour‐suppressing function of SPRY2.

Individual Comparison of Cholesterol Metabolism in Normal and Tumour Areas in Radical Prostatectomy Specimens from Patients with Prostate Cancer: Results of the CHOMECAP Study

BACKGROUND

Deregulation of cholesterol metabolism represents a hallmark of prostate cancer (PCa) and promotes its development.

OBJECTIVE

To compare cholesterol metabolism on individual paired normal and tumour prostate tissues obtained from patients with PCa.

DESIGN, SETTING, AND PARTICIPANTS

Between 2008 and 2012, normal and tumour paired tissue samples were collected from radical prostatectomy specimens from a cohort of 69 patients treated for localised PCa.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Tumour and normal tissues were subjected to gene analysis, sterol measurement, and immunohistochemistry. The Wilcoxon paired test and Spearman test were applied for comparison and correlation analyses, respectively. Principal component analysis was also carried out to investigate relationships between quantitative variables.

RESULTS AND LIMITATIONS

Overall, cholesterol concentrations were not significantly different between tissue pairs. However, tumour samples were significantly associated with downregulated de novo cholesterol synthesis, but exhibited 54.7% overexpression of SCARB1 that could increase high-density lipoprotein uptake in PCa. Tumour tissues showed different trafficking of available cholesterol, with significantly lower ACAT1, and an altered efflux via APOE. Furthermore, cholesterol metabolism in tumour tissues was characterised by higher accumulation of 7α-hydroxycholesterol (OHC), 7βOHC, and 7-ketosterol, and a lower level of 27OHC.

CONCLUSIONS

Focusing on individually paired prostate tissues, our results highlighted several differences between normal and tumour samples linked to a metabolic shift in cholesterol flux. PCa samples exhibited a specific tissue signature characterised by higher SCARB1 expression, higher accumulation of OHC species, and clear downregulation of de novo cholesterol synthesis.

PATIENT SUMMARY

Comparing normal and tumour tissues from the same prostates, our study identified a set of alterations in prostate cancer samples in terms of their use of cholesterol. These included higher cholesterol uptake, accumulation of oxidised cholesterol derivatives, and autonomous cellular production of cholesterol. Together, these data provide promising clinical targets to fight prostate cancer.

miR-27a in serum acts as biomarker for prostate cancer detection and promotes cell proliferation by targeting Sprouty2

Prostate cancer (PCa) exhibits a high incidence among men, but there is no effective and non-invasive biomarker for the diagnosis of PCa, and the pathogenesis of PCa remains unclear. The present study identified that miR-27a was significantly overexpressed in the tumor tissues and sera of patients with PCa. In addition, high serum levels of miR-27a were correlated with poor survival in patients with PCa. Receiver-operating characteristic curves analysis demonstrated that the serum levels of miR-27a exhibited a high area under the curve value. Furthermore, miR-27a mimics or inhibitors significantly promoted or repressed the proliferation of PCa cells, respectively. In addition, it was identified that the expression of Sprouty2 (SPRY2) was inversely correlated with the expression of miR-27a in PCa tissues. The knockdown or overexpression of SPRY2 promoted or suppressed the proliferation of PCa cells, respectively, and the overexpression of SPRY2 inhibited the increased proliferation and cell cycle distribution of PCa cells mediated by miR-27a mimics. Taken together, these data indicated that the serum levels of miR-27a may be a novel and non-invasive biomarker for the diagnosis and prognosis of patients with PCa, and miR-27a/SPRY2 may be a therapeutic target for the treatment of PCa.

Review of recent efforts to discover biomarkers for early detection, monitoring, prognosis, and prediction of treatment responses of patients with gastric cancer

Gastric cancer (GC) is the leading cause of cancer-related death worldwide. Despite recent advances in diagnosis and therapy, the prognosis of patients with GC is poor. Many patients have inoperable disease upon diagnosis or experience recurrent disease after curative gastrectomy. Unfortunately, tumor markers for GC, such as serum carcinoembryonic antigen and carbohydrate antigen 19-9, lack sufficient sensitivity and specificity. Therefore, effective biomarkers are required to detect early GC and to predict tumor recurrence and chemosensitivity. Areas covered: Here we aimed to review recent developments in techniques that improve the detection of aberrant expression of GC-associated molecules, including protein coding genes, microRNAs, long noncoding RNAs, and methylated promoter DNAs. Expert commentary: Detection of genetic and epigenetic alterations in gastric tissue or in the circulation will likely improve the diagnosis and management of GC to achieve significantly improved outcomes.

Sprouty2 loss-induced IL6 drives castration-resistant prostate cancer through scavenger receptor B1

Metastatic castration-resistant prostate cancer (mCRPC) is a lethal form of treatment-resistant prostate cancer and poses significant therapeutic challenges. Deregulated receptor tyrosine kinase (RTK) signalling mediated by loss of tumour suppressor Sprouty2 (SPRY2) is associated with treatment resistance. Using pre-clinical human and murine mCRPC models, we show that SPRY2 deficiency leads to an androgen self-sufficient form of CRPC Mechanistically, HER2-IL6 signalling axis enhances the expression of androgen biosynthetic enzyme HSD3B1 and increases SRB1-mediated cholesterol uptake in SPRY2-deficient tumours. Systemically, IL6 elevated the levels of circulating cholesterol by inducing host adipose lipolysis and hepatic cholesterol biosynthesis. SPRY2-deficient CRPC is dependent on cholesterol bioavailability and SRB1-mediated tumoral cholesterol uptake for androgen biosynthesis. Importantly, treatment with ITX5061, a clinically safe SRB1 antagonist, decreased treatment resistance. Our results indicate that cholesterol transport blockade may be effective against SPRY2-deficient CRPC.

Inhibition of CREB binding protein-beta-catenin signaling down regulates CD133 expression and activates PP2A-PTEN signaling in tumor initiating liver cancer cells

Background

The WNT-beta-catenin pathway is known to regulate cellular homeostasis during development and tissue regeneration. Activation of WNT signaling increases the stability of cytoplasmic beta-catenin and enhances its nuclear translocation. Nuclear beta-catenin function is regulated by transcriptional co-factors such as CREB binding protein (CBP) and p300. Hyper-activated WNT-beta-catenin signaling is associated with many cancers. However, its role in inducing stemness to liver cancer cells, its autoregulation and how it regulates tumor suppressor pathways are not well understood. Here we have investigated the role of CBP-beta-catenin signaling on the expression of CD133, a known stem cell antigen and PP2A-PTEN pathway in tumor initiating liver cancer cells.

Methods

Human hepatoblastoma cell line HepG2 and clonally expanded CD133 expressing tumor initiating liver cells (TICs) from premalignant murine liver were used in this study. CBP-beta-catenin inhibitor ICG001 was used to target CBP-beta catenin signaling in liver cancer cells in vitro. Western blotting and real time PCR (qPCR) were used to quantify protein expression/phosphorylation and mRNA levels, respectively. CBP and CD133 gene silencing was performed by siRNA transfection. Fluorescence Activated Cell Sorting (FACS) was performed to quantify CD133 positive cells. Protein Phosphatase (PP2A) activity was measured after PP2AC immunoprecipitation.

Results

CBP inhibitor ICG001 and CBP silencing significantly reduced CD133 expression and anchorage independent growth in HepG2 and murine TICs. CD133 silencing in TICs decreased cell proliferation and expression levels of cell cycle regulatory genes, CyclinD1 and CyclinA2. ICG001 treatment and CBP silencing reduced the levels of phospho^{Ser380/Tyr382/383}PTEN, phospho^Ser473-AKT, Phospho-^Ser552beta-catenin in TICs. ICG001 mediated de-phosphorylation of PTEN in TICs was PP2A dependent and partly prevented by co-treatment with PP2A inhibitor okadaic acid.

Conclusions

CBP-beta-catenin signaling promotes stemness via CD133 induction and cell proliferation in TICs. We found a novel functional link between CBP-beta-catenin and PP2A-PTEN-AKT pathway in liver TICs. Therefore, CBP-beta-catenin-PP2A-PTEN-AKT signaling axis could be a novel therapeutic target to prevent liver tumor initiation and cancer recurrence.

Electronic supplementary material

The online version of this article (10.1186/s12964-018-0222-5) contains supplementary material, which is available to authorized users.

Small-Molecule Activators of Protein Phosphatase 2A for the Treatment of Castration-Resistant Prostate Cancer

Primary prostate cancer is generally treatable by androgen deprivation therapy, however, later recurrences of castrate-resistant prostate cancer (CRPC) that are more difficult to treat nearly always occur due to aberrant reactivation of the androgen receptor (AR). In this study, we report that CRPC cells are particularly sensitive to the growth-inhibitory effects of reengineered tricyclic sulfonamides, a class of molecules that activate the protein phosphatase PP2A, which inhibits multiple oncogenic signaling pathways. Treatment of CRPC cells with small-molecule activators of PP2A (SMAP) in vitro decreased cellular viability and clonogenicity and induced apoptosis. SMAP treatment also induced an array of significant changes in the phosphoproteome, including most notably dephosphorylation of full-length and truncated isoforms of the AR and downregulation of its regulatory kinases in a dose-dependent and time-dependent manner. In murine xenograft models of human CRPC, the potent compound SMAP-2 exhibited efficacy comparable with enzalutamide in inhibiting tumor formation. Overall, our results provide a preclinical proof of concept for the efficacy of SMAP in AR degradation and CRPC treatment.Significance: A novel class of small-molecule activators of the tumor suppressor PP2A, a serine/threonine phosphatase that inhibits many oncogenic signaling pathways, is shown to deregulate the phosphoproteome and to destabilize the androgen receptor in advanced prostate cancer. Cancer Res; 78(8); 2065-80. ©2018 AACR.

ARF1 promotes prostate tumorigenesis via targeting oncogenic MAPK signaling

ADP-ribosylation factor 1 (ARF1) is a crucial regulator in vesicle-mediated membrane trafficking and involved in the activation of signaling molecules. However, virtually nothing is known about its function in prostate cancer. Here we have demonstrated that ARF1 expression is significantly elevated in prostate cancer cells and human tissues and that the expression levels of ARF1 correlate with the activation of mitogen-activated protein kinases (MAPK) ERK1/2. Furthermore, we have shown that overexpression and knockdown of ARF1 produce opposing effects on prostate cancer cell proliferation, anchorage-independent growth and tumor growth in mouse xenograft models and that ARF1-mediated cell proliferation can be abolished by the Raf1 inhibitor GW5074 and the MEK inhibitors U0126 and PD98059. Moreover, inhibition of ARF1 activation achieved by mutating Thr48 abolishes ARF1's abilities to activate the ERK1/2 and to promote cell proliferation. These data demonstrate that the aberrant MAPK signaling in prostate cancer is, at least in part, under the control of ARF1 and that, similar to Ras, ARF1 is a critical regulator in prostate cancer progression. These data also suggest that ARF1 may represent a key molecular target for prostate cancer therapeutics and diagnosis.

Overexpression of sprouty2 in human oral squamous cell carcinogenesis

OBJECTIVE

This study investigated SPRY2 expression in human oral potentially malignant disorders (OPMDs) and oral squamous cell carcinomas (OSCCs).

METHODS

75 OSCCs, 23 OPMDs with malignant transformation (MT), 17 OPMDs without MT, and eight normal oral mucosa (NOM) tissues were used for immunohistochemical staining; three OSCC tissues with normal tissue counterparts were used for western blotting. Three human oral cancer cell lines (OCCLs), an oral precancer cell line (DOK), and a NOM primary culture (NOMPC) were used for western blotting; OCCLs and NOMPC were employed for real-time quantitative reverse transcription-polymerase chain reaction. OCCLs were evaluated in terms of proliferation, migration, invasion and BRAF V600E point mutation assays.

RESULTS

Significantly increased SPRY2 protein expression was observed in OSCCs as compared with NOM, and SPRY2 expression also differed between OSCC patients with and without lymph-node metastasis. SPRY2 protein and mRNA expressions were significantly enhanced as compared with NOMPC. Increased phospho-ERK expression was observed in OCCLs as compared with NOMPC. Significant decreases in the proliferation rate, degrees of migration and invasion were noted in OCCLs with SPRY2 siRNA transfection as compared with those without SPRY2 siRNA transfection. No BRAF V600E point mutation was observed for OCCLs as compared with NOMPC. A significantly increased SPRY2 protein level was noted in OPMDs with MT as compared to those without MT, and was also found in OPMDs with MT in comparison with NOM, as well as in DOK in comparison with NOMPC.

CONCLUSIONS

Our results indicated that SPRY2 overexpression is associated with human oral squamous-cell carcinogenesis.

PTEN loss and activation of K-RAS and β-catenin cooperate to accelerate prostate tumourigenesis

Aberrant phosphoinositide 3-kinase (PI3K), mitogen-activated protein kinase (MAPK) and WNT signalling are emerging as key events in the multistep nature of prostate tumourigenesis and progression. Here, we report a compound prostate cancer murine model in which these signalling pathways cooperate to produce a more aggressive prostate cancer phenotype. Using Cre-LoxP technology and the probasin promoter, we combined the loss of Pten (Ptenfl/fl ), to activate the PI3K signalling pathway, with either dominant stabilized β-catenin [Catnb+/lox(ex3) ] or activated K-RAS (K-Ras+/V12 ) to aberrantly activate WNT and MAPK signalling, respectively. Synchronous activation of all three pathways (triple mutants) significantly reduced survival (median 96 days) as compared with double mutants [median: 140 days for Catnb+/lox(ex3) Ptenfl/fl ; 182 days for Catnb+/lox(ex3) K-Ras+/V12 ; 238 days for Ptenfl/fl K-Ras+/V12 ], and single mutants [median: 383 days for Catnb+/lox(ex3) ; 407 days for Ptenfl/fl ], reflecting the accelerated tumourigenesis. Tumours followed a stepwise progression from mouse prostate intraepithelial neoplasia to invasive adenocarcinoma, similar to that seen in human disease. There was significantly elevated cellular proliferation, tumour growth and percentage of invasive adenocarcinoma in triple mutants as compared with double mutants and single mutants. Triple mutants showed not only activated AKT, extracellular-signal regulated kinase 1/2, and nuclear β-catenin, but also significantly elevated signalling through mechanistic target of rapamycin complex 1 (mTORC1). In summary, we show that combined deregulation of the PI3K, MAPK and WNT signalling pathways drives rapid progression of prostate tumourigenesis, and that deregulation of all three pathways results in tumours showing aberrant mTORC1 signalling. As mTORC1 signalling is emerging as a key driver of androgen deprivation therapy resistance, our findings are important for understanding the biology of therapy-resistant prostate cancer and identifying potential approaches to overcome this. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Feedback regulation of RTK signaling in development

Precise regulation of the amplitude and duration of receptor tyrosine kinase (RTK) signaling is critical for the execution of cellular programs and behaviors. Understanding these control mechanisms has important implications for the field of developmental biology, and in recent years, the question of how augmentation or attenuation of RTK signaling via feedback loops modulates development has become of increasing interest. RTK feedback regulation is also important for human disease research; for example, germline mutations in genes that encode RTK signaling pathway components cause numerous human congenital syndromes, and somatic alterations contribute to the pathogenesis of diseases such as cancers. In this review, we survey regulators of RTK signaling that tune receptor activity and intracellular transduction cascades, with a focus on the roles of these genes in the developing embryo. We detail the diverse inhibitory mechanisms utilized by negative feedback regulators that, when lost or perturbed, lead to aberrant increases in RTK signaling. We also discuss recent biochemical and genetic insights into positive regulators of RTK signaling and how these proteins function in tandem with negative regulators to guide embryonic development.

Analysis of Nkx3.1:Cre-driven Erk5 deletion reveals a profound spinal deformity which is linked to increased osteoclast activity

Extracellular signal-regulated protein kinase 5 (ERK5) has been implicated during development and carcinogenesis. Nkx3.1-mediated Cre expression is a useful strategy to genetically manipulate the mouse prostate. While grossly normal at birth, we observed an unexpected phenotype of spinal protrusion in Nkx3.1:Cre;Erk5 fl/fl (Erk5 fl/fl) mice by ~6-8 weeks of age. X-ray, histological and micro CT (µCT) analyses showed that 100% of male and female Erk5 fl/fl mice had a severely deformed curved thoracic spine, with an associated loss of trabecular bone volume. Although sex-specific differences were observed, histomorphometry measurements revealed that both bone resorption and bone formation parameters were increased in male Erk5 fl/fl mice compared to wild type (WT) littermates. Osteopenia occurs where the rate of bone resorption exceeds that of bone formation, so we investigated the role of the osteoclast compartment. We found that treatment of RANKL-stimulated primary bone marrow-derived macrophage (BMDM) cultures with small molecule ERK5 pathway inhibitors increased osteoclast numbers. Furthermore, osteoclast numbers and expression of osteoclast marker genes were increased in parallel with reduced Erk5 expression in cultures generated from Erk5 fl/fl mice compared to WT mice. Collectively, these results reveal a novel role for Erk5 during bone maturation and homeostasis in vivo.

Increased T-cell Infiltration Elicited by Erk5 Deletion in a Pten-Deficient Mouse Model of Prostate Carcinogenesis

Prostate cancer does not appear to respond to immune checkpoint therapies where T-cell infiltration may be a key limiting factor. Here, we report evidence that ablating the growth regulatory kinase Erk5 can increase T-cell infiltration in an established Pten-deficient mouse model of human prostate cancer. Mice that were doubly mutant in prostate tissue for Pten and Erk5 (prostate DKO) exhibited a markedly increased median survival with reduced tumor size and proliferation compared with control Pten-mutant mice, the latter of which exhibited increased Erk5 mRNA expression. A comparative transcriptomic analysis revealed upregulation in prostate DKO mice of the chemokines Ccl5 and Cxcl10, two potent chemoattractants for T lymphocytes. Consistent with this effect, we observed a relative increase in a predominantly CD4+ T-cell infiltrate in the prostate epithelial and stroma of tumors from DKO mice. Collectively, our results offer a preclinical proof of concept for ERK5 as a target to enhance T-cell infiltrates in prostate cancer, with possible implications for leveraging immune therapy in this disease. Cancer Res; 77(12); 3158-68. ©2017 AACR.

Cell Cycle Control by PTEN

Continuous and error-free chromosome inheritance through the cell cycle is essential for genomic stability and tumor suppression. However, accumulation of aberrant genetic materials often causes the cell cycle to go awry, leading to malignant transformation. In response to genotoxic stress, cells employ diverse adaptive mechanisms to halt or exit the cell cycle temporarily or permanently. The intrinsic machinery of cycling, resting, and exiting shapes the cellular response to extrinsic stimuli, whereas prevalent disruption of the cell cycle machinery in tumor cells often confers resistance to anticancer therapy. Phosphatase and tensin homolog (PTEN) is a tumor suppressor and a guardian of the genome that is frequently mutated or deleted in human cancer. Moreover, it is increasingly evident that PTEN deficiency disrupts the fundamental processes of genetic transmission. Cells lacking PTEN exhibit cell cycle deregulation and cell fate reprogramming. Here, we review the role of PTEN in regulating the key processes in and out of cell cycle to optimize genomic integrity.

MiR-106b and miR-93 regulate cell progression by suppression of PTEN via PI3K/Akt pathway in breast cancer

Accumulating evidences have revealed that dysregulated microRNAs (miRNAs) involve in the tumorigenesis, progression and even lead to poor prognosis of various carcinomas, including breast cancer. MiRNA-106b-5p (miR-106b) and miRNA-93-5p (miR-93) levels were confirmed to be significantly upregulated in breast cancer clinical samples (n=36) and metastatic cell line (MDA-MB-231) compared with those in the paired adjacent tissues and normal breast epithelial cell line (MCF-10A). Moreover, further research stated that the capability of migration, invasion and proliferation changed along with the altered expression of miR-106b and miR-93 in breast cancer. PTEN, the tumor-suppressor gene, was discovered to be reduced in breast cancer tissues or MDA-MB-231 cells with high levels of miR-106b and miR-93, which were inversely expressed in PTEN overexpression tissues or cells. Based on the investigation, miR-106b and miR-93 induced the migration, invasion and proliferation and simultaneously enhanced the activity of phosphatidylinositol-3 kinase (PI3K)/Akt pathway of MCF-7 cells, which could be blocked by upregulation of PTEN. Furthermore, suppression of PTEN reversed the function induced by anti-miR-106b and anti-miR-93 in MDA-MB-231 cells, indicating that PTEN was directly targeted by these miRNAs and acted as the potential therapeutic target for breast cancer therapy. In short, reductive PTEN mediated by miR-106b and miR-93 promoted cell progression through PI3K/Akt pathway in breast cancer.

Redox Regulation of the Tumor Suppressor PTEN by Hydrogen Peroxide and Tert-Butyl Hydroperoxide

Organic peroxides and hydroperoxides are skin tumor promoters. Free radical derivatives from these compounds are presumed to be the prominent mediators of tumor promotion. However, the molecular targets of these species are unknown. Phosphatase and tensin homologs deleted on chromosome 10 (PTEN) are tumor suppressors that play important roles in cell growth, proliferation, and cell survival by negative regulation of phosphoinositol-3-kinase/protein kinase B signaling. PTEN is reversibly oxidized in various cells by exogenous and endogenous hydrogen peroxide. Oxidized PTEN is converted back to the reduced form by cellular reducing agents, predominantly by the thioredoxin (Trx) system. Here, the role of tert-butyl hydroperoxide (t-BHP) in redox regulation of PTEN was analyzed by using cell-based and in vitro assays. Exposure to t-BHP led to oxidation of recombinant PTEN. In contrast to H₂O₂, PTEN oxidation by t-BHP was irreversible in HeLa cells. However, oxidized PTEN was reduced by exogenous Trx system. Taken together, these results indicate that t-BHP induces PTEN oxidation and inhibits Trx system, which results in irreversible PTEN oxidation in HeLa cells. Collectively, these results suggest a novel mechanism of t-BHP in the promotion of tumorigenesis.

A single-copy Sleeping Beauty transposon mutagenesis screen identifies new PTEN-cooperating tumor suppressor genes

The overwhelming number of genetic alterations identified through cancer genome sequencing requires complementary approaches to interpret their significance and interactions. Here we developed a novel whole-body insertional mutagenesis screen in mice, which was designed for the discovery of Pten-cooperating tumor suppressors. Toward this aim, we coupled mobilization of a single-copy inactivating Sleeping Beauty transposon to Pten disruption within the same genome. The analysis of 278 transposition-induced prostate, breast and skin tumors detected tissue-specific and shared data sets of known and candidate genes involved in cancer. We validated ZBTB20, CELF2, PARD3, AKAP13 and WAC, which were identified by our screens in multiple cancer types, as new tumor suppressor genes in prostate cancer. We demonstrated their synergy with PTEN in preventing invasion in vitro and confirmed their clinical relevance. Further characterization of Wac in vivo showed obligate haploinsufficiency for this gene (which encodes an autophagy-regulating factor) in a Pten-deficient context. Our study identified complex PTEN-cooperating tumor suppressor networks in different cancer types, with potential clinical implications.

Sprouty2 correlates with favorable prognosis of gastric adenocarcinoma via suppressing FGFR2-induced ERK phosphorylation and cancer progression

Fibroblast growth factor receptor 2 (FGFR2) has been identified as a predictive biomarker for unfavorable prognosis of gastric adenocarcinoma. As a well-defined antagonist in FGFR2-induced RAS/ERK activation, ectopic expression of sprouty (SPRY) family was reported in several kinds of cancers except gastric cancer. To explore the clinical significance of SPRY family and its correlation with FGFR2, we detected the expression of FGFR2 and SPRY family in 104 cases of gastric adenocarcinoma and subsequently analyzed their correlations with clinicopathological factors and overall survival rates by univariate and multivariate analysis. As the result, we demonstrated that both FGFR2 high-expression and SPRY2 low-expression indicated poorer prognosis of gastric adenocarcinoma. SPRY2 low-expression was significantly associated with FGFR2 high-expression, positive lymphatic invasion and metastasis. We further proved that SPRY2 could suppress FGFR2-induced ERK phosphorylation, cell proliferation and invasion with experiments in vitro and in vivo. In conclusion, we demonstrated that SPRY2 low-expression is a biomarker for unfavorable prognosis in gastric adenocarcinoma. SPRY2 can antagonize FGFR2-induced proliferation and invasion via suppressing ERK phosphorylation in gastric cancer cells, indicating SPRY2 as a potential therapeutic target for gastric adenocarcinoma treatment.