Activation of Akt signaling in prostate induces a TGFβ-mediated restraint on cancer progression and metastasis

CASK promotes prostate cancer progression via kinase-dependent activation of AKT

Until now, the role of calcium/calmodulin-dependent serine protein kinase (CASK) in prostate cancer (PCa) progression remains unknown. In this study, we investigated the roles of CASK in PCa progression, cell migration, and invasion. We found that CASK is up-regulated in PCa tissues of patients. Lentivirus-based CASK silencing does not affect cell growth or serum-free-induced cell death in PC3 and LNCaP cells, regardless of the presence or absence of TGF-β. CASK silencing decreases cell migration and invasion, either in the absence or presence of TGF-β stimulation. Immunoblotting data indicate that CASK silencing does not alter TGF-β-induced Smad2/3 and ERK phosphorylation but reduces TGF-β-induced AKT phosphorylation. To understand the roles of AKT and CaMK-like activity of CASK in cellular responses in PCa cells, we treated cells with AKT inhibitor and specific kinase inhibitors of CASK (NR162) and CaMKII (KN-93). We found that these agents can inhibit cell invasion and migration. In addition, NR162 and KN-93 also reduce TGF-β-induced AKT phosphorylation. Moreover, the co-immunoprecipitation data indicate the association between CASK and AKT. In HEK293 cells overexpressing system, we further found that CASK can enhance AKT S473 phosphorylation. The tumorigenic effect of CASK is confirmed in the xenograft mouse system. In summary, CASK is a promoter of PCa progression and can enhance PCa cell migration and invasion via kinase-dependent AKT activation independent of TGF-β-induced Smad2/3 and ERK signaling.

YTHDF3 Regulates the Degradation and Stability of m6A-Enriched Transcripts to Facilitate the Progression of Castration-Resistant Prostate Cancer

RNA N6-methyladenosine (m6A) readers mediate cancer progression. However, the functional role and potential mechanisms of the m6A readers in prostate cancer tumorigenicity remain to be elucidated. In this study, we demonstrate that YTHDF3 expression is elevated in castration-resistant prostate cancer (CRPC) and positively correlated to high grade, bone metastasis and poor survival. YTHDF3 expression promoted CRPC cell proliferation, epithelial to mesenchymal transition (EMT) and tumour progression. Mechanistically, YTHDF3 promoted the RNA degradation of SPOP and NXK3.1 but stabilized RNA expressions of TWIST1 and SNAI2 dependent on m6A to facilitate cell proliferation and EMT. Additionally, YTHDF3 expression enhanced AKT activity via degrading SPOP in an m6A-dependent manner. Importantly, we found that melatonin can compete with m6A to occupy the m6A-binding cage of YTHDF3, leading to inhibition of YTHFD3 and its target expressions as well as CRPC tumour growth. Our findings uncover an essential role of YTHDF3 in the progression of CRPC and highlight the role of melatonin in anti-CRPC activity.

Network pharmacology and bioinformatics analysis identifies potential therapeutic targets of Naringenin against COVID-19/LUSC

Background

Coronavirus disease 2019 (COVID-19) is a highly contagious respiratory disease that has posed a serious threat to people's daily lives and caused an unprecedented challenge to public health and people's health worldwide. Lung squamous cell carcinoma (LUSC) is a common type of lung malignancy with a highly aggressive nature and poor prognosis. Patients with LUSC could be at risk for COVID-19, We conducted this study to examine the potential for naringenin to develop into an ideal medicine and investigate the underlying action mechanisms of naringenin in COVID-19 and LUSC due to the anti-viral, anti-tumor, and anti-inflammatory activities of naringenin.

Methods

LUSC related genes were obtained from TCGA, PharmGKB, TTD,GeneCards and NCBI, and then the transcriptome data for COVID-19 was downloaded from GEO, DisGeNET, CTD, DrugBank, PubChem, TTD, NCBI Gene, OMIM. The drug targets of Naringenin were revealed through CTD, BATMAN, TCMIP, SymMap, Chemical Association Networks, SwissTargetPrediction, PharmMapper, ECTM, and DGIdb. The genes related to susceptibility to COVID-19 in LUSC patients were obtained through differential analysis. The interaction of COVID-19/LUSC related genes was evaluated and demonstrated using STRING to develop a a COX risk regression model to screen and evaluate the association of genes with clinical characteristics. To investigate the related functional and pathway analysis of the common targets of COVID-19/LUSC and Naringenin, KEGG and GO enrichment analysis were employed to perform the functional analysis of the target genes. Finally, The Hub Gene was screened and visualized using Cytoscape, and molecular docking between the drug and the target was performed using Autodock.

Results

We discovered numerous COVID-19/LUSC target genes and examined their prognostic value in LUSC patients utilizing a variety of bioinformatics and network pharmacology methods. Furthermore, a risk score model with strong predictive performance was developed based on these target genes to assess the prognosis of LUSC patients with COVID-19. We intersected the therapeutic target genes of naringenin with the LUSC, COVID-19-related targets, and identified 354 common targets, which could be used as potential target genes for naringenin to treat COVID-19/LUSC. The treatment of COVID-19/LUSC with naringenin may involve oxidative stress, anti-inflammatory, antiviral, antiviral, apoptosis, immunological, and multiple pathways containing PI3K-Akt, HIF-1, and VEGF, according to the results of the GO and KEGG enrichment analysis of these 354 common targets. By constructing a PPI network, we ascertained AKT1, TP53, SRC, MAPK1, MAPK3, and HSP90AA1 as possible hub targets of naringenin for the treatment of COVID-19/LUSC. Last but not least, molecular docking investigations showed that naringenin has strong binding activity in COVID-19/LUSC.

Conclusion

We revealed for the first time the pharmacological targets and potential molecular processes of naringenin for the treatment of COVID-19/LUSC. However, these results need to be confirmed by additional research and validation in real LUSC patients with COVID-19.

Establishment and characterization of prostate organoids from treatment-naïve patients with prostate cancer

Three-dimensional (3D) organoid culture systems are emerging as potential reliable tools to investigate basic developmental processes of human disease, especially cancer. The present study used established and modified culture conditions to report successful generation and characterization of patient-derived organoids from fresh primary tissue specimens of patients with treatment-naïve prostate cancer (PCa). Fresh tissue specimens were collected, digested enzymatically and the resulting cell suspensions were plated in a 3D environment using Matrigel as an extracellular matrix. Previously established 12-factor medium for organoid culturing was modified to create a minimal 5-factor medium. Organoids and corresponding tissue specimens were characterized using transcriptomic analysis, immunofluorescent analysis, and immunohistochemistry. Furthermore, patient-derived organoids were used to assess the drug response. Treatment-naïve patient-derived PCa organoids were obtained from fresh radical prostatectomy specimens. These PCa organoids mimicked the heterogeneity of corresponding parental tumor tissue. Histopathological analysis demonstrated similar tissue architecture and cellular morphology, as well as consistent immunohistochemical marker expression. Also, the results confirmed the potential of organoids as an in vitro model to assess potential personalized treatment responses as there was a differential drug response between different patient samples. In conclusion, the present study investigated patient-derived organoids from a cohort of treatment-naïve patients. Derived organoids mimicked the histological features and prostate lineage profiles of their corresponding parental tissue and may present a potential model to predict patient-specific treatment response in a pre-clinical setting.

Anti-androgen therapy induces transcriptomic reprogramming in metastatic castration-resistant prostate cancer in a murine model

Despite recent development of next-generation androgen receptor (AR) antagonists, metastatic castration-resistant prostate cancer (CRPC) remains incurable and requires deeper understanding through studies in suitable animal models. Prostate-specific deletion of Pten and Smad4 in mice recapitulated the disease progression of human prostate adenocarcinoma, including metastasis to lymph nodes and lung. Moreover, Pten/Smad4 tumors fostered an immunosuppressive microenvironment dominated by myeloid-derived suppressor cells (MDSCs). However, the response of Pten/Smad4 tumors to androgen deprivation and anti-androgen therapies has not been described. Here, we report that the combination of surgical castration and enzalutamide treatment in Pten/Smad4 mice slowed down the tumor growth and prolonged the median survival of the mice for 8 weeks. Treatment-naïve and castration-resistant primary tumors exhibited comparable levels of immune infiltrations with the exception of reduced monocytic MDSCs in CRPC. RNA profiling of treatment-naïve and castration-resistant primary tumors revealed largely preserved transcriptome with modest expressional alterations of collagen-related and immune-related genes, among which CC chemokine receptor type 2 (Ccr2) downregulation and predicted negative activation in CRPC was consistent with reduced monocytic MDSC infiltration. Importantly, significant transcriptomic reprograming was observed in lung metastatic CRPC compared with primary CRPC and enriched for immune-related and coagulation-related pathways. At the individual gene level, we validated the expression changes of some of the most upregulated (Cd36, Bmp5, Bmp6, Etv5, Prex2, Ptprb, Egfl6, Itga8 and Cxcl12) and downregulated genes (Cxcl9 and Adamts5). Together, this study uncovers the inherent activity of Pten/Smad4 tumors to progress to CRPC and highlights potentially targetable transcriptomic signatures associated with CRPC metastasis.

HF, Wotton D, Paschal BM. Post-Transcriptional Regulation of PARP7 Protein Stability Is Controlled by Androgen Signaling

Poly-ADP-ribose polymerases (PARPs) are enzymes that catalyze ADP-ribosylation and play critical roles in normal and disease settings. The PARP family member, PARP7, is a mono-ADP-ribosyltransferase that has been suggested to play a tumor suppressive role in breast, ovarian, and colorectal cancer. Here, we have investigated how androgen signaling regulates PARP7 homeostasis in prostate cancer cells, where PARP7 is a direct target gene of AR. We found that the PARP7 protein is extremely short-lived, with a half-life of 4.5 min. We show that in addition to its transcriptional regulation by AR, PARP7 is subject to androgen-dependent post-transcriptional regulation that increases its half-life to 25.6 min. This contrasts with PARP1, PARP2, PARP9, and PARP14, which do not display rapid turnover and are not regulated by androgen signaling. Androgen- and AR-dependent stabilization of PARP7 leads to accumulation in the nucleus, which we suggest is a major site of action. Mutations in the catalytic domain, the Cys3His1 zinc finger, and WWE (tryptophan-tryptophan-glutamate) domains in PARP7 each reduce the degradation rate of PARP7, suggesting the overall structure of the protein is tuned for its rapid turnover. Our finding that PARP7 is regulated by AR signaling both transcriptionally and post-transcriptionally in prostate cancer cells suggests the dosage of PARP7 protein is subject to tight regulation.

Opposing roles and potential antagonistic mechanism between TGF-β and BMP pathways: Implications for cancer progression

The transforming growth factor β (TGF-β) superfamily participates in tumour proliferation, apoptosis, differentiation, migration, invasion, immune evasion and extracellular matrix remodelling. Genetic deficiency in distinct components of TGF-β and BMP-induced signalling pathways or their excessive activation has been reported to regulate the development and progression of some cancers. As more in-depth studies about this superfamily have been conducted, more evidence suggests that the TGF-β and BMP pathways play an opposing role. The cross-talk of these 2 pathways has been widely studied in kidney disease and bone formation, and the opposing effects have also been observed in some cancers. However, the antagonistic mechanisms are still insufficiently investigated in cancer. In this review, we aim to display more evidences and possible mechanisms accounting for the antagonism between these 2 pathways, which might provide some clues for further study in cancer.

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Describe the basics of TGF-β and BMP signalling

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Summarize the potential mechanisms accounting for the antagonism between TGF-β and BMP pathways

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Provide some evidence about the antagonistic effects between pathways observed in some cancers

Tgfbr2 inactivation facilitates cellular plasticity and development of Pten-null prostate cancer

Mutations in tumors can create a state of increased cellular plasticity that promotes resistance to treatment. Thus, there is an urgent need to develop novel strategies for identifying key factors that regulate cellular plasticity in order to combat resistance to chemotherapy and radiation treatment. Here we report that prostate epithelial cell reprogramming could be exploited to identify key factors required for promoting prostate cancer tumorigenesis and cellular plasticity. Deletion of phosphatase and tensin homolog (Pten) and transforming growth factor-beta receptor type 2 (Tgfbr2) may increase prostate epithelial cell reprogramming efficiency in vitro and cause rapid tumor development and early mortality in vivo. Tgfbr2 ablation abolished TGF-β signaling but increased the bone morphogenetic protein (BMP) signaling pathway through the negative regulator Tmeff1. Furthermore, increased BMP signaling promotes expression of the tumor marker genes ID1, Oct4, Nanog, and Sox2; ID1/STAT3/NANOG expression was inversely correlated with patient survival. Thus, our findings provide information about the molecular mechanisms by which BMP signaling pathways render stemness capacity to prostate tumor cells.

Deregulation of Negative Controls on TGF-β1 Signaling in Tumor Progression

The multi-functional cytokine transforming growth factor-β1 (TGF-β1) has growth inhibitory and anti-inflammatory roles during homeostasis and the early stages of cancer. Aberrant TGF-β activation in the late-stages of tumorigenesis, however, promotes development of aggressive growth characteristics and metastatic spread. Given the critical importance of this growth factor in fibrotic and neoplastic disorders, the TGF-β1 network is subject to extensive, multi-level negative controls that impact receptor function, mothers against decapentaplegic homolog 2/3 (SMAD2/3) activation, intracellular signal bifurcation into canonical and non-canonical pathways and target gene promotor engagement. Such negative regulators include phosphatase and tensin homologue (PTEN), protein phosphatase magnesium 1A (PPM1A), Klotho, bone morphogenic protein 7 (BMP7), SMAD7, Sloan-Kettering Institute proto-oncogene/ Ski related novel gene (Ski/SnoN), and bone morphogenetic protein and activin membrane-bound Inhibitor (BAMBI). The progression of certain cancers is accompanied by loss of expression, overexpression, mislocalization, mutation or deletion of several endogenous repressors of the TGF-β1 cascade, further modulating signal duration/intensity and phenotypic reprogramming. This review addresses how their aberrant regulation contributes to cellular plasticity, tumor progression/metastasis and reversal of cell cycle arrest and discusses the unexplored therapeutic value of restoring the expression and/or function of these factors as a novel approach to cancer treatment.

TGFβ signaling limits lineage plasticity in prostate cancer

Although treatment options for localized prostate cancer (CaP) are initially effective, the five-year survival for metastatic CaP is below 30%. Mutation or deletion of the PTEN tumor suppressor is a frequent event in metastatic CaP, and inactivation of the transforming growth factor (TGF) ß signaling pathway is associated with more advanced disease. We previously demonstrated that mouse models of CaP based on inactivation of Pten and the TGFß type II receptor (Tgfbr2) rapidly become invasive and metastatic. Here we show that mouse prostate tumors lacking Pten and Tgfbr2 have higher expression of stem cell markers and genes indicative of basal epithelial cells, and that basal cell proliferation is increased compared to Pten mutants. To better model the primarily luminal phenotype of human CaP we mutated Pten and Tgfbr2 specifically in luminal cells, and found that these tumors also progress to invasive and metastatic cancer. Accompanying the transition to invasive cancer we observed de-differentiation of luminal tumor cells to an intermediate cell type with both basal and luminal markers, as well as differentiation to basal cells. Proliferation rates in these de-differentiated cells were lower than in either basal or luminal cells. However, de-differentiated cells account for the majority of cells in micro-metastases consistent with a preferential contribution to metastasis. We suggest that active TGFß signaling limits lineage plasticity in prostate luminal cells, and that de-differentiation of luminal tumor cells can drive progression to metastatic disease.

Dithiolethiones: a privileged pharmacophore for anticancer therapy and chemoprevention

Dithiolethiones are five-membered sulfur-containing cyclic scaffolds that exhibit antioxidative, anti-inflammatory, antithrombic and chemotherapeutic activities. Dithiolethiones display the chemopreventive and cytoprotective effects by activating the antioxidant response element and mounting the transcription of cytoprotective phase II enzymatic machinery. In addition, several classes of dithiolethiones efficiently modulate the activities of proteins that play crucial roles in normal and cancer cells, including glutathione S-transferase, cyclooxygenases and master regulator NF-κB. The present paper summarizes synthetic aspects, pharmacological potentials and biological attributes of dithiolethiones and its derivatives. Additionally, this review concludes with a discussion on how the current state-of-the-art technologies may help in defining a structure–activity relationship of dithiolethiones, thereby facilitating the design and synthesis of potent drug candidates.

Contextual determinants of TGFβ action in development, immunity and cancer

Few cell signals match the impact of the transforming growth factor-β (TGFβ) family in metazoan biology. TGFβ cytokines regulate cell fate decisions during development, tissue homeostasis and regeneration, and are major players in tumorigenesis, fibrotic disorders, immune malfunctions and various congenital diseases. The effects of the TGFβ family are mediated by a combinatorial set of ligands and receptors and by a common set of receptor-activated mothers against decapentaplegic homologue (SMAD) transcription factors, yet the effects can differ dramatically depending on the cell type and the conditions. Recent progress has illuminated a model of TGFβ action in which SMADs bind genome-wide in partnership with lineage-determining transcription factors and additionally integrate inputs from other pathways and the chromatin to trigger specific cellular responses. These new insights clarify the operating logic of the TGFβ pathway in physiology and disease.

A microRNA/Runx1/Runx2 network regulates prostate tumor progression from onset to adenocarcinoma in TRAMP mice

While decades of research have identified molecular pathways inducing and promoting stages of prostate cancer malignancy, studies addressing dynamic changes of cancer-related regulatory factors in a prostate tumor progression model are limited. Using the TRAMP mouse model of human prostate cancer, we address mechanisms of deregulation for the cancer-associated transcription factors, Runx1 and Runx2 by identifying microRNAs with reciprocal expression changes at six time points during 33 weeks of tumorigenesis. We molecularly define transition stages from PIN lesions to hyperplasia/neoplasia and progression to adenocarcinoma by temporal changes in expression of human prostate cancer markers, including the androgen receptor and tumor suppressors, Nkx3.1 and PTEN. Concomitant activation of PTEN, AR, and Runx factors occurs at early stages. At late stages, PTEN and AR are downregulated, while Runx1 and Runx2 remain elevated. Loss of Runx-targeting microRNAs, miR-23b-5p, miR-139-5p, miR-205-5p, miR-221-3p, miR-375-3p, miR-382-5p, and miR-384-5p, contribute to aberrant Runx expression in prostate tumors. Our studies reveal a Runx/miRNA interaction axis centered on PTEN-PI3K-AKT signaling. This regulatory network translates to mechanistic understanding of prostate tumorigenesis that can be developed for diagnosis and directed therapy.

A novel highly potent trivalent TGF-β receptor trap inhibits early-stage tumorigenesis and tumor cell invasion in murine Pten-deficient prostate glands

The effects of transforming growth factor beta (TGF-β) signaling on prostate tumorigenesis has been shown to be strongly dependent on the stage of development, with TGF-β functioning as a tumor suppressor in early stages of disease and as a promoter in later stages. To study in further detail the paradoxical tumor-suppressive and tumor-promoting roles of the TGF-β pathway, we investigated the effect of systemic treatment with a TGF-β inhibitor on early stages of prostate tumorigenesis. To ensure effective inhibition, we developed and employed a novel trivalent TGF-β receptor trap, RER, comprised of domains derived from the TGF-β type II and type III receptors. This trap was shown to completely block TβRII binding, to antagonize TGF-β1 and TGF-β3 signaling in cultured epithelial cells at low picomolar concentrations, and it showed equal or better anti-TGF-β activities than a pan TGF-β neutralizing antibody and a TGF-β receptor I kinase inhibitor in various prostate cancer cell lines. Systemic administration of RER inhibited prostate tumor cell proliferation as indicated by reduced Ki67 positive cells and invasion potential of tumor cells in high grade prostatic intraepithelial neoplasia (PIN) lesions in the prostate glands of Pten conditional null mice. These results provide evidence that TGF-β acts as a promoter rather than a suppressor in the relatively early stages of this spontaneous prostate tumorigenesis model. Thus, inhibition of TGF-β signaling in early stages of prostate cancer may be a novel therapeutic strategy to inhibit the progression as well as the metastatic potential in patients with prostate cancer.

Opposing roles of TGFβ and BMP signaling in prostate cancer development

SMAD4 constrains progression of Pten-null prostate cancer and serves as a common downstream node of transforming growth factor β (TGFβ) and bone morphogenetic protein (BMP) pathways. Here, we dissected the roles of TGFβ receptor II (TGFBR2) and BMP receptor II (BMPR2) using a Pten-null prostate cancer model. These studies demonstrated that the molecular actions of TGFBR2 result in both SMAD4-dependent constraint of proliferation and SMAD4-independent activation of apoptosis. In contrast, BMPR2 deletion extended survival relative to Pten deletion alone, establishing its promoting role in BMP6-driven prostate cancer progression. These analyses reveal the complexity of TGFβ-BMP signaling and illuminate potential therapeutic targets for prostate cancer.

The protein kinase C super-family member PKN is regulated by mTOR and influences differentiation during prostate cancer progression

BACKGROUND

Phosphoinositide-3 (PI-3) kinase signaling has a pervasive role in cancer. One of the key effectors of PI-3 kinase signaling is AKT, a kinase that promotes growth and survival in a variety of cancers. Genetically engineered mouse models of prostate cancer have shown that AKT signaling is sufficient to induce prostatic epithelial neoplasia (PIN), but insufficient for progression to adenocarcinoma. This contrasts with the phenotype of mice with prostate-specific deletion of Pten, where excessive PI-3 kinase signaling induces both PIN and locally invasive carcinoma. We reasoned that additional PI-3 kinase effector kinases promote prostate cancer progression via activities that provide biological complementarity to AKT. We focused on the PKN kinase family members, which undergo activation in response to PI-3 kinase signaling, show expression changes in prostate cancer, and contribute to cell motility pathways in cancer cells.

METHODS

PKN kinase activity was measured by incorporation of ³² P into protein substrates. Phosphorylation of the turn-motif (TM) in PKN proteins by mTOR was analyzed using the TORC2-specific inhibitor torin and a PKN1 phospho-TM-specific antibody. Amino acid substitutions in the TM of PKN were engineered and assayed for effects on kinase activity. Cell motility-related functions and PKN localization was analyzed by depletion approaches and immunofluorescence microscopy, respectively. The contribution of PKN proteins to prostate tumorigenesis was characterized in several mouse models that express PKN transgenes. The requirement for PKN activity in prostate cancer initiated by loss of phosphatase and tensin homolog deleted on chromosome 10 (Pten), and the potential redundancy between PKN isoforms, was analyzed by prostate-specific deletion of Pkn1, Pkn2, and Pten.

RESULTS AND CONCLUSIONS

PKN1 and PKN2 contribute to motility pathways in human prostate cancer cells. PKN1 and PKN2 kinase activity is regulated by TORC2-dependent phosphorylation of the TM, which together with published data indicates that PKN proteins receive multiple PI-3 kinase-dependent inputs. Transgenic expression of active AKT and PKN1 is not sufficient for progression beyond PIN. Moreover, Pkn1 is not required for tumorigenesis initiated by loss of Pten. Triple knockout of Pten, Pkn1, and Pkn2 in mouse prostate results in squamous cell carcinoma, an uncommon but therapy-resistant form of prostate cancer.

Genetic and Molecular Analyses indicate independent effects of TGIFs on Nodal and Gli3 in neural tube patterning

Holoprosencephaly (HPE) is a prevalent craniofacial developmental disorder that has both genetic and environmental causes. The gene encoding TG-interacting factor 1 (TGIF1) is among those that are routinely screened in HPE patients. However, the mechanisms by which TGIF1 variants cause HPE are not fully understood. TGIF1 is a transcriptional repressor that limits the output of the Transforming Growth Factor ß (TGFß)/Nodal signaling pathway, and HPE in patients with TGIF1 variants has been suggested to be due to increased Nodal signaling. Mice lacking both Tgif1 and its paralog, Tgif2, have HPE, and embryos lacking Tgif function do not survive past mid-gestation. Here, we show that in the presence of a Nodal heterozygous mutation, proliferation defects are rescued and a proportion of embryos lacking all Tgif function survive to late gestation. However, these embryos have a classic HPE phenotype, suggesting that this is a Nodal-independent effect of Tgif loss of function. Further, we show that the Gli3 gene is a direct target for repression by Tgifs, independent of TGFß/Nodal signaling, consistent with Tgif mutations causing HPE via Nodal-independent effects on the Sonic Hedgehog (Shh) pathway. Based on this work, we propose a model for distinct functions of Tgifs in the Nodal and Shh/Gli3 pathways during forebrain development.

Down-regulation of β-arrestin2 promotes tumour invasion and indicates poor prognosis of hepatocellular carcinoma

β-arrestins, including β-arrestin1 and β-arrestin2, are multifunctional adaptor proteins. β-arrestins have recently been found to play new roles in regulating intracellular signalling networks associated with malignant cell functions. Altered β-arrestin expression has been reported in many cancers, but its role in hepatocellular carcinoma (HCC) is not clear. We therefore examined the roles of β-arrestins in HCC using an animal model of progressive HCC, HCC patient samples and HCC cell lines with stepwise metastatic potential. We demonstrated that β-arrestin2 level, but not β-arrestin1 level, decreased in conjunction with liver tumourigenesis in a mouse diethylnitrosamine-induced liver tumour model. Furthermore, β-arrestin2 expression was reduced in HCC tissues compared with noncancerous tissues in HCC patients. β-arrestin2 down-regulation in HCC was significantly associated with poor patient prognoses and aggressive pathologic features. In addition, our in vitro study showed that β-arrestin2 overexpression significantly reduced cell migration and invasion in cultured HCC cells. Furthermore, β-arrestin2 overexpression up-regulated E-cadherin expression and inhibited vimentin expression and Akt activation. These results suggest that β-arrestin2 down-regulation increases HCC cell migration and invasion ability. Low β-arrestin2 expression may be indicative of a poor prognosis or early cancer recurrence in patients who have undergone surgery for HCC.

MicroRNA-365a-3p promotes tumor growth and metastasis in laryngeal squamous cell carcinoma

MicroRNAs (miRNAs) are increasingly recognized as oncogenes or tumor suppressors in laryngeal squamous cell carcinoma (LSCC). In this study, we analyzed the roles of miR-365a-3p, miR-143-5p, and miR-494-3p in LSCC using Annexin V/propidium iodide double staining and flow cyto-metry, along with a Transwell migration and invasion assay. The results showed that miR-365a-3p inhibitor significantly facilitated cell apoptosis and suppressed cell cycle progression, migration, and invasion in Hep-2 cells. However, miR-143-5p and miR-494-3p had no such influences. We then investigated the role of miR-365a-3p in LSCC in vivo and found that miR-365a-3p inhibitor suppressed LSCC xenograft tumor growth and metastasis in xenograft mouse models. Moreover, miR-365a-3p inhibitor significantly decreased the expression of p-AKT (Ser473), which indicated that miR-365a-3p can mediate PI3K/AKT signaling pathway transduction via p-AKT (Ser473) in LSCC. The data suggest that miR-365a-3p may act as an oncomiR and may promote growth and metastasis in LSCC via the PI3K/AKT signaling pathway, and thus miR‑365a-3p may be a potential therapeutic target for treatment of LSCC.

MicroRNA Library-Based Functional Screening Identified Androgen-Sensitive miR-216a as a Player in Bicalutamide Resistance in Prostate Cancer

Prostate cancer is a major hormone-dependent tumor affecting men, and is often treated by hormone therapy at the primary stages. Despite its initial efficiency, the disease eventually acquires resistance, resulting in the recurrence of castration-resistant prostate cancer. Recent studies suggest that dysregulation of microRNA (miRNA) function is one of the mechanisms underlying hormone therapy resistance. Identification of critical miRNAs involved in endocrine resistance will therefore be important for developing therapeutic targets for prostate cancer. In the present study, we performed an miRNA library screening to identify anti-androgen bicalutamide resistance-related miRNAs in prostate cancer LNCaP cells. Cells were infected with a lentiviral miRNA library and subsequently maintained in media containing either bicalutamide or vehicle for a month. Microarray analysis determined the amounts of individual miRNA precursors and identified 2 retained miRNAs after one-month bicalutamide treatment. Of these, we further characterized miR-216a, because its function in prostate cancer remains unknown. miR-216a could be induced by dihydrotestosterone in LNCaP cells and ectopic expression of miR-216a inhibited bicalutamide-mediated growth suppression of LNCaP cells. Furthermore, a microarray dataset revealed that the expression levels of miR-216a were significantly higher in clinical prostate cancer than in benign samples. These results suggest that functional screening using an miRNA expression library could be useful for identifying novel miRNAs that contribute to bicalutamide resistance in prostate cancer.

Targeting PI3K/Akt/mTOR signaling pathway in the treatment of prostate cancer radioresistance

The phosphatidylinositol-3-kinase/Akt and the mammalian target of rapamycin (PI3K/Akt/mTOR) pathway is one of the most frequently activated signaling pathways in prostate cancer (CaP) and other cancers, and responsible for the survival, metastasis and therapeutic resistance. Recent advances in radiation therapy indicate that activation of this pathway is closely associated with cancer radioresistance, which is a major challenge for the current CaP radiation treatment. Therefore, targeting this pathway by inhibitors to enhance radiosensitivity has great potential for clinical benefits of CaP patients. In this review, we summarize the recent findings in the PI3K/Akt/mTOR pathway in CaP radiotherapy research and discuss the potential use of the PI3K/Akt/mTOR pathway inhibitors as radiosensitizers in the treatment of CaP radioresistance in preclinical studies to explore novel approaches for future clinical trials.

Additive Effect of Zfhx3/Atbf1 and Pten Deletion on Mouse Prostatic Tumorigenesis

The phosphatase and tensin homolog (PTEN) and the zinc finger homeobox 3 (ZFHX3)/AT-motif binding factor 1 (ATBF1) genes have been established as tumor suppressor genes in prostate cancer by their frequent deletions and mutations in human prostate cancer and by the formation of mouse prostatic intraepithelial neoplasia (mPIN) or tumor by their deletions in mouse prostates. However, whether ZFHX3/ATBF1 deletion together with PTEN deletion facilitates prostatic tumorigenesis is unknown. In this study, we simultaneously deleted both genes in mouse prostatic epithelia and performed histological and molecular analyses. While deletion of one Pten allele alone caused low-grade (LG) mPIN as previously reported, concurrent deletion of Zfhx3/Atbf1 promoted the progression to high-grade (HG) mPIN or early carcinoma. Zfhx3/Atbf1 and Pten deletions together increased cell proliferation, disrupted the smooth muscle layer between epithelium and stroma, and increased the number of apoptotic cells. Deletion of both genes also accelerated the activation of Akt and Erk1/2 oncoproteins. These results suggest an additive effect of ZFHX3/ATBF1 and PTEN deletions on the development and progression of prostate neoplasia.

A genetic variant of MDM4 influences regulation by multiple microRNAs in prostate cancer

The oncogene MDM4, also known as MDMX or HDMX, contributes to cancer susceptibility and progression through its capacity to negatively regulate a range of genes with tumour-suppressive functions. As part of a recent genome-wide association study it was determined that the A-allele of the rs4245739 SNP (A>C), located in the 3'-UTR of MDM4, is associated with an increased risk of prostate cancer. Computational predictions revealed that the rs4245739 SNP is located within a predicted binding site for three microRNAs (miRNAs): miR-191-5p, miR-887 and miR-3669. Herein, we show using reporter gene assays and endogenous MDM4 expression analyses that miR-191-5p and miR-887 have a specific affinity for the rs4245739 SNP C-allele in prostate cancer. These miRNAs do not affect MDM4 mRNA levels, rather they inhibit its translation in C-allele-containing PC3 cells but not in LNCaP cells homozygous for the A-allele. By analysing gene expression datasets from patient cohorts, we found that MDM4 is associated with metastasis and prostate cancer progression and that targeting this gene with miR-191-5p or miR-887 decreases in PC3 cell viability. This study is the first, to our knowledge, to demonstrate regulation of the MDM4 rs4245739 SNP C-allele by two miRNAs in prostate cancer, and thereby to identify a mechanism by which the MDM4 rs4245739 SNP A-allele may be associated with an increased risk for prostate cancer.

Intensified antineoplastic effect by combining an HDAC-inhibitor, an mTOR-inhibitor and low dosed interferon alpha in prostate cancer cells

A significant proportion of men diagnosed with prostate cancer (PCa) eventually develop metastatic disease, which progresses to castration resistance, despite initial response to androgen deprivation. As anticancer therapy has become increasingly effective, acquired drug resistance has emerged, limiting efficacy. Combination treatment, utilizing different drug classes, exemplifies a possible strategy to foil resistance development. The effects of the triple application of the histone deacetylase (HDAC) inhibitor valproic acid (VPA), the mammalian target of rapamycin inhibitor everolimus and low dosed interferon alpha (IFNα) on PCa cell growth and dissemination capacity were investigated. For that purpose, the human PCa cell lines, PC-3, DU-145 and LNCaP were treated with the combined regimen or separate single agents. Cell growth was investigated by the MTT dye reduction assay. Flow cytometry served to analyse cell cycle progression. Adhesion to vascular endothelium or immobilized collagen, fibronectin and laminin was quantified. Migration and invasion characteristics were determined by the modified Boyden chamber assay. Integrin α and β subtypes were investigated by flow cytometry, western blotting and RT-PCR. Integrin related signalling, Epidermal Growth Factor Receptor (EGFr), Akt, p70S6kinase and extracellular signal-regulated kinases (ERK)1/2 activation were also assessed. The triple application of VPA, everolimus and low dosed IFNα blocked tumour cell growth and dissemination significantly better than any agent alone. Antitumour effects were associated with pronounced alteration in the cell cycle machinery, intracellular signalling and integrin expression profile. Combining VPA, everolimus and low dosed IFNα might be a promising option to counteract resistance development and improve outcome in PCa patients.

Developmental exposure to estrogen alters differentiation and epigenetic programming in a human fetal prostate xenograft model

Prostate cancer is the most frequent non-cutaneous malignancy in men. There is strong evidence in rodents that neonatal estrogen exposure plays a role in the development of this disease. However, there is little information regarding the effects of estrogen in human fetal prostate tissue. This study explored early life estrogen exposure, with and without a secondary estrogen and testosterone treatment in a human fetal prostate xenograft model. Histopathological lesions, proliferation, and serum hormone levels were evaluated at 7, 30, 90, and 200-day time-points after xenografting. The expression of 40 key genes involved in prostatic glandular and stromal growth, cell-cycle progression, apoptosis, hormone receptors and tumor suppressors was evaluated using a custom PCR array. Epigenome-wide analysis of DNA methylation was performed on whole tissue, and laser capture-microdissection (LCM) isolated epithelial and stromal compartments of 200-day prostate xenografts. Combined initial plus secondary estrogenic exposures had the most severe tissue changes as revealed by the presence of hyperplastic glands at day 200. Gene expression changes corresponded with the cellular events in the KEGG prostate cancer pathway, indicating that initial plus secondary exposure to estrogen altered the PI3K-Akt signaling pathway, ultimately resulting in apoptosis inhibition and an increase in cell cycle progression. DNA methylation revealed that differentially methylated CpG sites significantly predominate in the stromal compartment as a result of estrogen-treatment, thereby providing new targets for future investigation. By using human fetal prostate tissue and eliminating the need for species extrapolation, this study provides novel insights into the gene expression and epigenetic effects related to prostate carcinogenesis following early life estrogen exposure.

Tumor-suppressive activity of Lunatic Fringe in prostate through differential modulation of Notch receptor activation

Elevated Notch ligand and receptor expression has been associated with aggressive forms of prostate cancer, suggesting a role for Notch signaling in regulation of prostate tumor initiation and progression. Here, we report a critical role for Lunatic Fringe (Lfng), which encodes an O-fucosylpeptide 3-ß-N-acetylglucosaminyltransferase known to modify epidermal growth factor repeats of Notch receptor proteins, in regulation of prostate epithelial differentiation and proliferation, as well as in prostate tumor suppression. Deletion of Lfng in mice caused altered Notch activation in the prostate, associated with elevated accumulation of Notch1, Notch2, and Notch4 intracellular domains, decreased levels of the putative Notch3 intracellular fragment, as well as increased expression of Hes1, Hes5, and Hey2. Loss of Lfng resulted in expansion of the basal layer, increased proliferation of both luminal and basal cells, and ultimately, prostatic intraepithelial neoplasia. The Lfng-null prostate showed down-regulation of prostatic tumor suppressor gene NKX3.1 and increased androgen receptor expression. Interestingly, expression of LFNG and NKX3.1 were positively correlated in publically available human prostate cancer data sets. Knockdown of LFNG in DU-145 prostate cancer cells led to expansion of CD44(+)CD24(-) and CD49f(+)CD24(-) stem/progenitor-like cell population associated with enhanced prostatosphere-forming capacity. Taken together, these data revealed a tumor-suppressive role for Lfng in the prostate through differential regulation of Notch signaling.

A genome-wide RNAi screen identifies FOXO4 as a metastasis-suppressor through counteracting PI3K/AKT signal pathway in prostate cancer

Activation of the PI3K/AKT signal pathway is a known driving force for the progression to castration-recurrent prostate cancer (CR-CaP), which constitutes the major lethal phenotype of CaP. Here, we identify using a genomic shRNA screen the PI3K/AKT-inactivating downstream target, FOXO4, as a potential CaP metastasis suppressor. FOXO4 protein levels inversely correlate with the invasive potential of a panel of human CaP cell lines, with decreased mRNA levels correlating with increased incidence of clinical metastasis. Knockdown (KD) of FOXO4 in human LNCaP cells causes increased invasion in vitro and lymph node (LN) metastasis in vivo without affecting indices of proliferation or apoptosis. Increased Matrigel invasiveness was found by KD of FOXO1 but not FOXO3. Comparison of differentially expressed genes affected by FOXO4-KD in LNCaP cells in culture, in primary tumors and in LN metastases identified a panel of upregulated genes, including PIP, CAMK2N1, PLA2G16 and PGC, which, if knocked down by siRNA, could decrease the increased invasiveness associated with FOXO4 deficiency. Although only some of these genes encode FOXO promoter binding sites, they are all RUNX2-inducible, and RUNX2 binding to the PIP promoter is increased in FOXO4-KD cells. Indeed, the forced expression of FOXO4 reversed the increased invasiveness of LNCaP/shFOXO4 cells; the forced expression of FOXO4 did not alter RUNX2 protein levels, yet it decreased RUNX2 binding to the PIP promoter, resulting in PIP downregulation. Finally, there was a correlation between FOXO4, but not FOXO1 or FOXO3, downregulation and decreased metastasis-free survival in human CaP patients. Our data strongly suggest that increased PI3K/AKT-mediated metastatic invasiveness in CaP is associated with FOXO4 loss, and that mechanisms to induce FOXO4 re-expression might suppress CaP metastatic aggressiveness.

The novel miR-9500 regulates the proliferation and migration of human lung cancer cells by targeting Akt1

MicroRNAs have crucial roles in lung cancer cell development. They regulate cell growth, proliferation and migration by mediating the expression of tumor suppressor genes and oncogenes. We identified and characterized the novel miR-9500 in human lung cancer cells. The miR-9500 forms a stem-loop structure and is conserved in other mammals. The expression levels of miR-9500 were reduced in lung cancer cells and lung cancer tissues compared with normal tissues, as verified by TaqMan miRNA assays. It was confirmed that the putative target gene, Akt1, was directly suppressed by miR-9500, as demonstrated by a luciferase reporter assay. The miR-9500 significantly repressed the protein expression levels of Akt1, as demonstrated via western blot, but did not affect the corresponding mRNA levels. Akt1 has an important role in lung carcinogenesis, and depletion of Akt1 has been shown to have antiproliferative and anti-migratory effects in previous studies. In the current study, the overexpression of miR-9500 inhibited cell proliferation and the expression of cell cycle-related proteins. Likewise, the overexpression of miR-9500 impeded cell migration in human lung cancer cells. In an in vivo assay, miR-9500 significantly suppressed Fluc expression compared with NC and ASO-miR-9500, suggesting that cell proliferation was inhibited in nude mice. Likewise, miR-9500 repressed tumorigenesis and metastasis by targeting Akt1. These data indicate that miR-9500 might be applicable for lung cancer therapy.

HF, Paschal BM, Wotton D. Prostate cancer induced by loss of Apc is restrained by TGFβ signaling

Recent work with mouse models of prostate cancer (CaP) has shown that inactivation of TGFβ signaling in prostate epithelium can cooperate with deletion of the Pten tumor suppressor to drive locally aggressive cancer and metastatic disease. Here, we show that inactivating the TGFβ pathway by deleting the gene encoding the TGFβ type II receptor (Tgfbr2) in combination with a deletion of the Apc tumor suppressor gene specifically in mouse prostate epithelium, results in the rapid onset of invasive CaP. Micro-metastases were observed in the lymph nodes and lungs of a proportion of the double mutant mice, whereas no metastases were observed in Apc single mutant mice. Prostate-specific Apc;Tgfbr2 mutants had a lower frequency of metastasis and survived significantly longer than Pten;Tgfbr2 double mutants. However, all Apc;Tgfbr2 mutants developed invasive cancer by 30 weeks of age, whereas invasive cancer was rarely observed in Apc single mutant animals, even by one year of age. Further comparison of the Pten and Apc models of CaP revealed additional differences, including adenosquamous carcinoma in the Apc;Tgfbr2 mutants that was not seen in the Pten model, and a lack of robust induction of the TGFβ pathway in Apc null prostate. In addition to causing high-grade prostate intra-epithelial neoplasia (HGPIN), deletion of either Pten or Apc induced senescence in affected prostate ducts, and this restraint was overcome by loss of Tgfbr2. In summary, this work demonstrates that TGFβ signaling restrains the progression of CaP induced by different tumor suppressor mutations, suggesting that TGFβ signaling exerts a general tumor suppressive effect in prostate.