PRK1/PKN1 controls migration and metastasis of androgen-independent prostate cancer cells

Lipid-Binding Regions within PKC-Related Serine/Threonine Protein Kinase N1 (PKN1) Required for Its Regulation

PKC-related serine/threonine protein kinase N1 (PKN1) is a protease/lipid-activated protein kinase that acts downstream of the RhoA and Rac1 pathways. PKN1 comprises unique regulatory, hinge region, and PKC homologous catalytic domains. The regulatory domain harbors two homologous regions, i.e., HR1 and C2-like. HR1 consists of three heptad repeats (HR1a, HR1b, and HR1c), with PKN1-(HR1a) hosting an amphipathic high-affinity cardiolipin-binding site for phospholipid interactions. Cardiolipin and C18:1 oleic acid are the most potent lipid activators of PKN1. PKN1-(C2) contains a pseudosubstrate sequence overlapping that of C20:4 arachidonic acid. However, the cardiolipin-binding site(s) within PKN1-(C2) and the respective binding properties remain unclear. Herein, we reveal (i) that the primary PKN1-(C2) sequence contains conserved amphipathic cardiolipin-binding motif(s); (ii) that trimeric PKN1-(C2) predominantly adopts a β-stranded conformation; (iii) that two distinct types of cardiolipin (or phosphatidic acid) binding occur, with the hydrophobic component playing a key role at higher salt levels; (iv) the multiplicity of C18 fatty acid binding to PKN1-(C2); and (v) the relevance of our lipid-binding parameters for PKN1-(C2) in terms of kinetic parameters previously determined for the full-length PKN1 enzyme. Thus, our discoveries create opportunities to design specific mammalian cell inhibitors that disrupt the localization of membrane-associated PKN1 signaling molecules.

Upregulation of PKN1 as a Prognosis Biomarker for Endometrial Cancer

BACKGROUND

Several markers of survival among endometrial cancer (EC) patients have been proposed, namely, the oncoprotein stathmin, RAF kinase inhibitor (RKIP), Cyclin A, GATA-binding protein 3 (GATA3), and growth and differentiation factor-15 (GDF-15). Their elevated expression correlated significantly with a high stage, serous papillary/clear cell subtypes, and aneuploidy. In a previous study, we reported the elevated expression of the serine/threonine protein kinase N1 (PKN1) in cancerous cells. In the present paper, we studied PKN1 expression in EC tissues from a large cohort of patients, to determine whether PKN1 can serve as a marker for the aggressiveness and prognosis of EC, and/or as a marker of survival among EC patients.

METHODS

Tissue samples from EC patients were examined retrospectively for tumor type, tumor size, FIGO stage and grade, depth of invasion in the myometrium, and presence of lymph node metastasis. The PKN1 protein expression in EC cells was assessed by immunohistochemistry. PKN1 mRNA levels were analyzed in publicly available databases, using bioinformatic tools.

RESULTS

We found that expression of PKN1 at the mRNA and proteins levels tended to increase in high-grade EC samples (P = .0001 and P = .06, respectively). In addition, patients with metastatic disease had higher PKN1 mRNA levels (P = .02). Moreover, patients with high PKN1 expression could be characterized by poorer survival.

CONCLUSIONS

We have shown a trend of the higher PKN1 expression levels in EC patients with poor prognosis. Therefore, PKN1 might be considered as a candidate prognostic marker for EC.

Genomic and phenotypic analysis of SspH1 identifies a new Salmonella effector, SspH3

Salmonella is a major foodborne pathogen and is responsible for a range of diseases. Not all Salmonella contribute to severe health outcomes as there is a large degree of genetic heterogeneity among the 2600 serovars within the genus. This variability across Salmonella serovars is linked to numerous genetic elements that dictate virulence. While several genetic elements encode virulence factors with well documented contributions to pathogenesis, many genetic elements implicated in Salmonella virulence remain uncharacterized. Many pathogens encode a family of E3 ubiquitin ligases that are delivered into the cells that they infect using a Type 3 Secretion System (T3SS). These effectors, known as NEL-domain E3s, were first characterized in Salmonella. Most Salmonella encode the NEL-effectors sspH2 and slrP, whereas only a subset of Salmonella encode sspH1. SspH1 has been shown to ubiquitinate the mammalian protein kinase PKN1, which has been reported to negatively regulate the pro-survival program Akt. We discovered that SspH1 mediates the degradation of PKN1 during infection of a macrophage cell line but that this degradation does not impact Akt signaling. Genomic analysis of a large collection of Salmonella genomes identified a putative new gene, sspH3, with homology to sspH1. SspH3 is a novel NEL-domain effector.

The PKN1- TRAF1 signaling axis as a potential new target for chronic lymphocytic leukemia

TRAF1 is a pro-survival adaptor molecule in TNFR superfamily (TNFRSF) signaling. TRAF1 is overexpressed in many B cell cancers including refractory chronic lymphocytic leukemia (CLL). Little has been done to assess the role of TRAF1 in human cancer. Here we show that the protein kinase C related kinase Protein Kinase N1 (PKN1) is required to protect TRAF1 from cIAP-mediated degradation during constitutive CD40 signaling in lymphoma. We show that the active phospho-Thr774 form of PKN1 is constitutively expressed in CLL but minimally detected in unstimulated healthy donor B cells. Through a screen of 700 kinase inhibitors, we identified two inhibitors, OTSSP167, and XL-228, that inhibited PKN1 in the nanomolar range and induced dose-dependent loss of TRAF1 in RAJI cells. OTSSP167 or XL-228 treatment of primary patient CLL samples led to a reduction in TRAF1, pNF-κB p65, pS6, pERK, Mcl-1 and Bcl-2 proteins, and induction of activated caspase-3. OTSSP167 synergized with venetoclax in inducing CLL death, correlating with loss of TRAF1, Mcl-1, and Bcl-2. Although correlative, these findings suggest the PKN1-TRAF1 signaling axis as a potential new target for CLL. These findings also suggest the use of the orally available inhibitor OTSSP167 in combination treatment with venetoclax for TRAF1 overexpressing CLL.

Protein kinase N1 promotes proliferation and invasion of liver cancer

Protein kinase (PK) N1, also called PKC-related protein 1, participates in the proliferation, invasion and metastasis of various malignant tumors. However, the role of PKN1 in liver cancer remains to be elucidated. The present study investigated the expression of PKN1 using immunohistochemistry in surgical specimens from 36 patients and analyzed the correlation with VEGF, microvascular density (MVD), cell proliferation index (Ki67) and clinicopathological parameters. PKN1 was highly expressed in hepatocellular carcinoma (HCC) and was positively correlated with histological grading of HCC, Ki67 expression and MVD. PKN1 expression in moderately and poorly differentiated HCC was significantly higher compared with highly differentiated HCC. Expression of PKN1 was positively correlated with Ki67 and MVD, and Ki67 expression was positively correlated with MVD. The effects of PKN1 on proliferation, invasion and apoptosis of liver cancer cells were detected in vitro. Cell viability, migration and invasion were reduced and the apoptosis rate was significantly improved when PKN1 expression was silenced in liver cancer cells. Thus, PKN1 serves an important role in the development and progression of liver cancer. Inhibition of PKN1 activity may provide a promising therapeutic target for liver cancer.

The structure and function of protein kinase C-related kinases (PRKs)

The protein kinase C-related kinase (PRK) family of serine/threonine kinases, PRK1, PRK2 and PRK3, are effectors for the Rho family small G proteins. An array of studies have linked these kinases to multiple signalling pathways and physiological roles, but while PRK1 is relatively well-characterized, the entire PRK family remains understudied. Here, we provide a holistic overview of the structure and function of PRKs and describe the molecular events that govern activation and autoregulation of catalytic activity, including phosphorylation, protein interactions and lipid binding. We begin with a structural description of the regulatory and catalytic domains, which facilitates the understanding of their regulation in molecular detail. We then examine their diverse physiological roles in cytoskeletal reorganization, cell adhesion, chromatin remodelling, androgen receptor signalling, cell cycle regulation, the immune response, glucose metabolism and development, highlighting isoform redundancy but also isoform specificity. Finally, we consider the involvement of PRKs in pathologies, including cancer, heart disease and bacterial infections. The abundance of PRK-driven pathologies suggests that these enzymes will be good therapeutic targets and we briefly report some of the progress to date.

Cyclin-dependent kinase 1-mediated phosphorylation of protein kinase N1 promotes anchorage-independent growth and migration

Protein kinase N1 (PKN1) is a member of the protein kinase C superfamily. Aberrations of PKN1 kinase activity are involved in several human pathological processes, including cancer. We found that PKN family proteins (PKN1/2/3) are phosphorylated in response to antitubulin drug-induced mitotic arrest. We identified cyclin-dependent kinase 1 (CDK1) as the corresponding kinase for PKN protein phosphorylation. CDK1 phosphorylates PKN1 at S533, S537, S562, and S916 in vitro and in cells during drug-induced mitotic arrest. Immunofluorescence staining further confirmed that PKN1 phosphorylation occurs during normal mitosis in a CDK1-dependent manner. Knockdown of PKN1 significantly inhibited anchorage-independent growth and migration without affecting proliferation in multiple cancer cell lines. We further showed that mitotic phosphorylation is essential for PKN1's oncogenic function, as the non-phosphorylatable mutant PKN1-4A failed to rescue anchorage-independent growth and migration in PKN1-knockdown cells. Thus, our findings reveal a novel regulatory mechanism for PKN1 in mitosis and its role in tumorigenesis.

A network analysis to identify mediators of germline-driven differences in breast cancer prognosis

Identifying the underlying genetic drivers of the heritability of breast cancer prognosis remains elusive. We adapt a network-based approach to handle underpowered complex datasets to provide new insights into the potential function of germline variants in breast cancer prognosis. This network-based analysis studies ~7.3 million variants in 84,457 breast cancer patients in relation to breast cancer survival and confirms the results on 12,381 independent patients. Aggregating the prognostic effects of genetic variants across multiple genes, we identify four gene modules associated with survival in estrogen receptor (ER)-negative and one in ER-positive disease. The modules show biological enrichment for cancer-related processes such as G-alpha signaling, circadian clock, angiogenesis, and Rho-GTPases in apoptosis.

PKN1 controls the aggregation, spheroid formation, and viability of mouse embryonic fibroblasts in suspension culture

The role of protein kinase N1 (PKN1) in cell aggregation and spheroid formation was investigated using mouse embryonic fibroblasts (MEFs) deficient in kinase activity caused by a point mutation (T778A) in the activation loop. Wild type (WT) MEFs formed cell aggregates within a few hours in suspension cultures placed in poly-2-hydroxyethylmethacrylate (poly-HEMA) coated flat-bottom dishes. By contrast, PKN1[T778A] (PKN1 T778A/T778A homozygous knock-in) MEFs showed significantly delayed aggregate formation and higher susceptibility to cell death. Video analysis of suspension cultures revealed decreased cell motility and lesser frequency of cell-cell contact in PKN1[T778A] MEFs compared to that in WT MEFs. Aggregate formation of PKN1[T778A] MEFs was compensated by shaking the cell suspension. When cultured in U-shaped ultra-low attachment well plates, initially larger-sized and loosely packed aggregates of WT MEFs underwent compaction resulting in a single round spheroid. On the other hand, image-based quantitative analysis of PKN1[T778A] MEFs revealed irregular compaction with decreased roundness, solidity, and sphericity within 24 h. Flow cytometry of PKN1[T778A] MEFs revealed decreased surface-expression of N-cadherin and integrins α5 and αV. These results suggest that kinase activity of PKN1 controls cell aggregation and spheroid compaction in MEF suspension culture, possibly by regulating the cell migration and cell-surface expression of N-cadherin and integrins.

PKN1 kinase-negative knock-in mice develop splenomegaly and leukopenia at advanced age without obvious autoimmune-like phenotypes

Protein kinase N1 (PKN1) knockout (KO) mice spontaneously form germinal centers (GCs) and develop an autoimmune-like disease with age. Here, we investigated the function of PKN1 kinase activity in vivo using aged mice deficient in kinase activity resulting from the introduction of a point mutation (T778A) in the activation loop of the enzyme. PKN1[T778A] mice reached adulthood without external abnormalities; however, the average spleen size and weight of aged PKN1[T778A] mice increased significantly compared to aged wild type (WT) mice. Histologic examination and Southern blot analyses of spleens showed extramedullary hematopoiesis and/or lymphomagenesis in some cases, although without significantly different incidences between PKN1[T778A] and WT mice. Additionally, flow cytometry revealed increased numbers in B220⁺, CD3⁺, Gr1⁺ and CD193⁺ leukocytes in the spleen of aged PKN1[T778A] mice, whereas the number of lymphocytes, neutrophils, eosinophils, and monocytes was reduced in the peripheral blood, suggesting an advanced impairment of leukocyte trafficking with age. Moreover, aged PKN1[T778A] mice showed no obvious GC formation nor autoimmune-like phenotypes, such as glomerulonephritis or increased anti-dsDNA antibody titer, in peripheral blood. Our results showing phenotypic differences between aged Pkn1-KO and PKN1[T778A] mice may provide insight into the importance of PKN1-specific kinase-independent functions in vivo.

In vitro study to assess the efficacy of CDK4/6 inhibitor Palbociclib (PD-0332991) for treating canine mammary tumours

Therapy of canine mammary tumours (CMTs) with classical antitumour drugs is problematic, so better therapeutic options are needed. Palbociclib (PD-0332991) is an innovative and effective anticancer drug for the treatment of breast cancer in women. Palbociclib is an inhibitor of cyclin-dependent kinase 4 (CDK4) and CDK6, which are key regulators of the cell cycle machinery and thus cell proliferation. In the present in vitro study, we investigated whether Palbociclib also represents a candidate drug to combat CMT. For this purpose, the effect of Palbociclib was analysed in P114 and CF41 cells, two CMT cell lines with an endogenous CDK4/6 co-expression. Incubation of P114 and CF41 cells with Palbociclib resulted in a dose- and time-dependent loss of phosphorylated retinoblastoma protein (pRb), a classical CDK4/6 substrate within the cell cycle machinery. Moreover, treatment of CMT cells with Palbociclib-induced cell cycle arrest affected cell viability, prevented colony formation and impaired cell migration activity. Palbociclib also inhibited the growth of P114 and CF41 cell spheroids. Immunohistochemical analysis of canine patient samples revealed a consistent expression of CDK6 in different canine mammary carcinoma types, but an individual and tumour-specific expression pattern of phosphorylated pRb independent of the tumour grade. Together, our findings let us suggest that Palbociclib has antitumour effects on CMT cells and that canine patients may represent potential candidates for treatment with this CDK4/6 inhibitor.

Protein Kinase N1 control of androgen-responsive serum response factor action provides rationale for novel prostate cancer treatment strategy

Sustained reliance on androgen receptor (AR) after failure of AR-targeting androgen deprivation therapy (ADT) prevents effective treatment of castration-recurrent (CR) prostate cancer (CaP). Interfering with the molecular machinery by which AR drives CaP progression may be an alternative therapeutic strategy but its feasibility remains to be tested. Here, we explore targeting the mechanism by which AR, via RhoA, conveys androgen-responsiveness to serum response factor (SRF), which controls aggressive CaP behavior and is maintained in CR-CaP. Following a siRNA screen and candidate gene approach, RNA-Seq studies confirmed that the RhoA effector Protein Kinase N1 (PKN1) transduces androgen-responsiveness to SRF. Androgen treatment induced SRF-PKN1 interaction, and PKN1 knockdown or overexpression severely impaired or stimulated, respectively, androgen regulation of SRF target genes. PKN1 overexpression occurred during clinical CR-CaP progression, and hastened CaP growth and shortened CR-CaP survival in orthotopic CaP xenografts. PKN1's effects on SRF relied on its kinase domain. The multikinase inhibitor lestaurtinib inhibited PKN1 action and preferentially affected androgen regulation of SRF over direct AR target genes. In a CR-CaP patient-derived xenograft, expression of SRF target genes was maintained while AR target gene expression declined and proliferative gene expression increased. PKN1 inhibition decreased viability of CaP cells before and after ADT. In patient-derived CaP explants, lestaurtinib increased AR target gene expression but did not significantly alter SRF target gene or proliferative gene expression. These results provide proof-of-principle for selective forms of ADT that preferentially target different fractions of AR's transcriptional output to inhibit CaP growth.

SPAG9 regulates HEF1 expression and drives EMT in bladder transitional cell carcinoma via rac1 signaling pathway

Recently SPAG9 has been reported to show aberrant expressions in numerous human malignancies and act as a crucial role in tumor's proliferation and invasion. Human enhancer of filamentation 1 (HEF1, also known as CasL and NEDD9) is a non-catalytic scaffolding protein belonging to CAS (Crk-associated substrate) protein family that interacts with multiple signaling cascades. Due to the diversified function of HEF1, abnormal expression of HEF1 frequently combines with malignant phenotypes and poor prognosis. However, little is known between the relationship of SPAG9 and HEF1 in bladder tumorigenesis. In this study, expression of SPAG9 in vivo and in vitro has been detected by quantitative real-time PCR and Western blot analysis after transfected with SPAG9 overexpression/inhibitor vector. We also found that HEF1 expression shows consistency and is regulated by SPAG9. Overexpression of SPAG9 promotes bladder cancer cells migration through HEF1 upregulation and emerges protein level of activated Rac1. Silencing SPAG9 inhibits cell migration through HEF1 downregulation and reduces protein level of activated Rac1. Also, we found that expression of EMT marker such as E-cadherin, Vimentin is regulated by SPAG9. Considering EMT plays a crucial role in tumor cells spreading and invasion, SPAG9 and HEF1 may potentially set a new therapeutic approach to bladder cancer treatment.

Inflammation and NF-κB Signaling in Prostate Cancer: Mechanisms and Clinical Implications

Prostate cancer is a highly prevalent form of cancer that is usually slow-developing and benign. Due to its high prevalence, it is, however, still the second most common cause of death by cancer in men in the West. The higher prevalence of prostate cancer in the West might be due to elevated inflammation from metabolic syndrome or associated comorbidities. NF-κB activation and many other signals associated with inflammation are known to contribute to prostate cancer malignancy. Inflammatory signals have also been associated with the development of castration resistance and resistance against other androgen depletion strategies, which is a major therapeutic challenge. Here, we review the role of inflammation and its link with androgen signaling in prostate cancer. We further describe the role of NF-κB in prostate cancer cell survival and proliferation, major NF-κB signaling pathways in prostate cancer, and the crosstalk between NF-κB and androgen receptor signaling. Several NF-κB-induced risk factors in prostate cancer and their potential for therapeutic targeting in the clinic are described. A better understanding of the inflammatory mechanisms that control the development of prostate cancer and resistance to androgen-deprivation therapy will eventually lead to novel treatment options for patients.

3D-cultivation of NSCLC cell lines induce gene expression alterations of key cancer-associated pathways and mimic in-vivo conditions

This work evaluated gene expression differences between a hanging-drop 3D NSCLC model and 2D cell cultures and their in-vivo relevance by comparison to patient-derived data from The Cancer Genome Atlas.

Gene expression of 2D and 3D cultures for Colo699 and A549 were assessed using Affymetrix HuGene 1.0 ST gene chips. Biostatistical analyses tested for reproducibility, comparability and significant differences in gene expression profiles between cell lines, experiments and culture methods.

The analyses revealed a high interassay correlation within specific culture systems proving a high validity. 979 genes were altered in A549 and 1106 in Colo699 cells due to 3D cultivation. The overlap of changed genes between the cell lines was small (149), but the involved pathways in the reactome and GO- analyses showed a high overlap with DNA methylation, cell cycle, SIRT1, PKN1 pathway, DNA repair and oxidative stress as well known cancer-associated representatives. Additional specific GSEA-analyses revealed changes in immunologic and endothelial cell proliferation pathways, whereas hypoxic, EMT and angiogenic pathways were downregulated.

Gene enrichment analyses showed 3D-induced gene up-regulations in the cell lines 38 to be represented in in-vivo samples of NSCLC patients using data of The Cancer Genome Atlas.

Thus, our 3D NSCLC model might provide a tool for early drug development and investigation of microenvironment-associated mechanisms. However, this work also highlights the need for further individualization and model adaption to address remaining challenges.

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.

Impaired lymphocyte trafficking in mice deficient in the kinase activity of PKN1

Knock-in mice lacking PKN1 kinase activity were generated by introducing a T778A point mutation in the catalytic domain. PKN1[T778A] mutant mice developed to adulthood without apparent external abnormalities, but exhibited lower T and B lymphocyte counts in the peripheral blood than those of wild-type (WT) mice. T and B cell development proceeded in an apparently normal fashion in bone marrow and thymus of PKN1[T778A] mice, however, the number of T and B cell counts were significantly higher in the lymph nodes and spleen of mutant mice in those of WT mice. After transfusion into WT recipients, EGFP-labelled PKN1[T778A] donor lymphocytes were significantly less abundant in the peripheral circulation and more abundant in the spleen and lymph nodes of recipient mice compared with EGFP-labelled WT donor lymphocytes, likely reflecting lymphocyte sequestration in the spleen and lymph nodes in a cell-autonomous fashion. PKN1[T778A] lymphocytes showed significantly lower chemotaxis towards chemokines and sphingosine 1-phosphate (S1P) than WT cells in vitro. The biggest migration defect was observed in response to S1P, which is essential for lymphocyte egress from secondary lymphoid organs. These results reveal a novel role of PKN1 in lymphocyte migration and localization.

PKN2 is essential for mouse embryonic development and proliferation of mouse fibroblasts

PKN2, a member of the protein kinase N (PKN) family, has been suggested by in vitro culture cell experiments to bind to Rho/Rac GTPases and contributes to cell-cell contact and cell migration. To unravel the in vivo physiological function of PKN2, we targeted the PKN2 gene. Constitutive disruption of the mouse PKN2 gene resulted in growth retardation and lethality before embryonic day (E) 10.5. PKN2^-/- embryo did not undergo axial turning and showed insufficient closure of the neural tube. Mouse embryonic fibroblasts (MEFs) derived from PKN2^-/- embryos at E9.5 failed to grow. Cre-mediated ablation of PKN2 in PKN2^flox/flox MEFs obtained from E14.5 embryos showed impaired cell proliferation, and cell cycle analysis of these MEFs showed a decrease in S-phase population. Our results show that PKN2 is essential for mouse embryonic development and cell-autonomous proliferation of primary MEFs in culture. Comparison of the PKN2^-/- phenotype with the phenotypes of PKN1 and PKN3 knockout strains suggests that PKN2 has distinct nonredundant functions in vivo, despite the structural similarity and evolutionary relationship among the three isoforms.

LncRNA GAS5 inhibits proliferation and progression of prostate cancer by targeting miR-103 through AKT/mTOR signaling pathway

In prior research, evidence has been found for a relation between low exposure of long non-coding RNAs (lncRNAs) and prostate tumor genesis. This study aims to clarify the underlying mechanisms of lncRNA GAS5 in prostate cancer (PCa). In total, 118 pairs of PCa tissues and matched adjacent non-tumor tissues were collected. Additionally, lncRNA GAS5 exposure levels were determined using RT-PCR and in situ hybridization. In addition, dual-luciferase report assay was performed to verify the target effect of lncRNA GAS5 on miR-103. The exposure levels of the proteins related to the protein kinase B (AKT)/mammalian target of rapamycin (mTOR) axis, including AKT, mTOR, and S6K1, were measured by western blot PC3 cells infected with lncRNA GAS5 mimic; lncRNA GAS5 siRNA; or a combination of lncRNA and miR-103. The proliferation, invasion, and migration ability of PC3 cells after being infected were tested by MTT assay, wound healing assay, and transwell assays. Finally, nude mouse xenograft models were used to measure lncRNA GAS5 effects on prostate tumor growth in vivo. The lncRNA GAS5 levels were reduced significantly in the PCa tissues and cell lines (P < 0.05). A low exposure of lncRNA GAS5 caused AKT/mTOR signaling pathway activation in PC3 cells (P < 0.05). In addition, over-exposure of lncRNA GAS5 was proven to significantly decelerate PCa cell progression in vitro and tumor growth in vivo through inactivating the AKT/mTOR signaling pathway (P < 0.05). This study proves that lncRNA GAS5 plays a significant role in the decelerating PCa development via mediating the AKT/mTOR signaling pathway through targeting miR-103.

Statin derivatives as therapeutic agents for castration-resistant prostate cancer

Despite recent advances in modern medicine, castration-resistant prostate cancer remains an incurable disease. Subpopulations of prostate cancer cells develop castration-resistance by obtaining the complete steroidogenic ability to synthesize androgens from cholesterol. Statin derivatives, such as simvastatin, inhibit cholesterol biosynthesis and may reduce prostate cancer incidence as well as progression to advanced, metastatic phenotype. In this study, we demonstrate novel simvastatin-related molecules SVA, AM1, and AM2 suppress the tumorigenicity of prostate cancer cell lines including androgen receptor-positive LNCaP C-81 and VCaP as well as androgen receptor-negative PC-3 and DU145. This is achieved through inhibition of cell proliferation, colony formation, and migration as well as induction of S-phase cell-cycle arrest and apoptosis. While the compounds effectively block androgen receptor signaling, their mechanism of inhibition also includes suppression of the AKT pathway, in part, through disruption of the plasma membrane. SVA also possess an added effect on cell growth inhibition when combined with docetaxel. In summary, of the compounds studied, SVA is the most potent inhibitor of prostate cancer cell tumorigenicity, demonstrating its potential as a promising therapeutic agent for castration-resistant prostate cancer.

Tofacitinib and analogs as inhibitors of the histone kinase PRK1 (PKN1)

AIM

The histone kinase PRK1 has been identified as a potential target to combat prostate cancer but selective PRK1 inhibitors are lacking. The US FDA -approved JAK1-3 inhibitor tofacitinib also potently inhibits PRK1 in vitro.

RESULTS

We show that tofacitinib also inhibits PRK1 in a cellular setting. Using tofacitinib as a starting point for structure-activity relationship studies, we identified a more potent and another more selective PRK1 inhibitor compared with tofacitinib. Furthermore, we found two potential PRK1/JAK3-selectivity hotspots.

CONCLUSION

The identified inhibitors and the selectivity hotspots lay the basis for the development of selective PRK1 inhibitors. The identification of PRK1, but also of other cellular tofacitinib targets, has implications on its clinical use and on future development of tofacitinib-like JAK inhibitors. [Formula: see text].

Cellular and Molecular Mechanisms of MT1-MMP-Dependent Cancer Cell Invasion

Metastasis is responsible for most cancer-associated deaths. Accumulating evidence based on 3D migration models has revealed a diversity of invasive migratory schemes reflecting the plasticity of tumor cells to switch between proteolytic and nonproteolytic modes of invasion. Yet, initial stages of localized regional tumor dissemination require proteolytic remodeling of the extracellular matrix to overcome tissue barriers. Recent data indicate that surface-exposed membrane type 1-matrix metalloproteinase (MT1-MMP), belonging to a group of membrane-anchored MMPs, plays a central role in pericellular matrix degradation during basement membrane and interstitial tissue transmigration programs. In addition, a large body of work indicates that MT1-MMP is targeted to specialized actin-rich cell protrusions termed invadopodia, which are responsible for matrix degradation. This review describes the multistep assembly of actin-based invadopodia in molecular details. Mechanisms underlying MT1-MMP traffic to invadopodia through endocytosis/recycling cycles, which are key to the invasive program of carcinoma cells, are discussed.

Identification of Highly Potent Protein Kinase C-Related Kinase 1 Inhibitors by Virtual Screening, Binding Free Energy Rescoring, and in vitro Testing

Despite the considerable interest in protein kinase C-related kinase 1 (PRK1) as a target in cancer research, there is still a lack of PRK1 inhibitors with suitable selectivity profiles and physicochemical properties. To identify new PRK1 inhibitors we applied a virtual screening approach, which combines ensemble docking, minimization of the protein-ligand complex, binding free energy calculations, and application of quantitative structure-activity relationship (QSAR) models for predicting in vitro activity. The developed approach was then applied in a prospective manner to screen available libraries of kinase inhibitors from Selleck and GlaxoSmithKline (GSK). Compounds that showed favorable prediction were then tested in vitro for PRK1 inhibition. Some of the hits were found to inhibit PRK1 in the low-nanomolar range. Three in vitro hits were additionally tested in a mass-spectrometry-based cellular kinase profiling assay to examine selectivity. Our findings show that nanomolar and drug-like inhibitors can be identified by the virtual screening approach presented herein. The identified inhibitors are valuable tools for gaining a better understanding of PRK1 inhibition, and the identified hits can serve as starting points for further chemical optimization.

Identification of Epigenetic Biomarkers of Lung Adenocarcinoma through Multi-Omics Data Analysis

Epigenetic mechanisms such as DNA methylation or histone modifications are essential for the regulation of gene expression and development of tissues. Alteration of epigenetic modifications can be used as an epigenetic biomarker for diagnosis and as promising targets for epigenetic therapy. A recent study explored cancer-cell specific epigenetic biomarkers by examining different types of epigenetic modifications simultaneously. However, it was based on microarrays and reported biomarkers that were also present in normal cells at a low frequency. Here, we first analyzed multi-omics data (including ChIP-Seq data of six types of histone modifications: H3K27ac, H3K4me1, H3K9me3, H3K36me3, H3K27me3, and H3K4me3) obtained from 26 lung adenocarcinoma cell lines and a normal cell line. We identified six genes with both H3K27ac and H3K4me3 histone modifications in their promoter regions, which were not present in the normal cell line, but present in ≥85% (22 out of 26) and ≤96% (25 out of 26) of the lung adenocarcinoma cell lines. Of these genes, NUP210 (encoding a main component of the nuclear pore complex) was the only gene in which the two modifications were not detected in another normal cell line. RNA-Seq analysis revealed that NUP210 was aberrantly overexpressed among the 26 lung adenocarcinoma cell lines, although the frequency of NUP210 overexpression was lower (19.3%) in 57 lung adenocarcinoma tissue samples studied and stored in another database. This study provides a basis to discover epigenetic biomarkers highly specific to a certain cancer, based on multi-omics data at the cell population level.

SPAG9 is involved in hepatocarcinoma cell migration and invasion via modulation of ELK1 expression

Background

Sperm-associated antigen 9 (SPAG9) is upregulated in several malignancies and its overexpression is positively correlated with cancer cell malignancies. However, the specific biological roles of SPAG9 in hepatocellular carcinoma (HCC) are less understood.

Methods

We analyzed SPAG9 and ETS-like gene 1, tyrosine kinase (ELK1) expression in 50 paired HCC specimens and adjacent noncancerous liver specimens using immunohistochemistry. SPAG9 small interfering RNA (siRNA) was used to knockdown SPAG9 expression in HCCLM3 and HuH7 cell lines. We used plasmids to upregulate ELK1 expression and siRNA to downregulate ELK1 expression in HuH7 cells. Quantitative real-time polymerase chain reaction and Western blot were used to evaluate the expression of SPAG9 and ELK1 at the mRNA and protein level, respectively. Wound healing, matrigel migration, and invasion analyses were performed to determine the effect of SPAG9 and ELK1 on HCC metastasis.

Results

SPAG9 and ELK1 were overexpressed in HCC tissue specimens and their expressions were higher in HCCLM3 and HuH7 cells compared to the low-metastatic HepG2 cells. Overexpression of SPAG9 was positively associated with tumor-node-metastasis staging (P=0.032), metastasis parameters (P=0.018) of HCC patients, and ELK1 expression (r=0.422, P<0.001) in HCC tissue specimens. In addition, knockdown of SPAG9 in HCCLM3 and HuH7 cells using siRNA significantly suppressed cell migration and invasion. Furthermore, we observed inhibition of ELK1 expression and p38 signaling. However, ELK1 overexpression reversed the inhibitory effects of SPAG9 siRNA on HCC cell metastasis and ELK1 depletion inhibited HuH7 cell migration and invasion.

Conclusion

SPAG9 overexpression was positively correlated with HCC metastasis and SPAG9-induced migration and invasion were partially dependent on ELK1 expression in HCC cell lines. These results suggest that SPAG9 may be a potential anti-metastasis target effective in HCC therapy.

MicroRNA-200a-3p suppresses tumor proliferation and induces apoptosis by targeting SPAG9 in renal cell carcinoma

Sperm-associated antigen 9(SPAG9), as a well-recognized oncogene protein, has a critical effect on renal cell carcinoma (RCC) progression. Our study tried to explore the mediator of miR-200a-3p, a tumor suppressing miRNA on SPAG9 expression and renal cell proliferation and apoptosis. We found the expression of miR-200a-3p was significantly lower in RCC specimens. Based on in vitro assays, we found miR-200a-3p significantly inhibit cancer cell proliferation by inducing apoptosis. In addition, our study uncovered that miR-200a-3p directly regulates oncogenic SPAG9 in 786-O and ACHN cells. Silencing of SPAG9 resulted in significantly decreased in the growth and the cell cycle of the renal cancer cell lines. Understanding of oncogenic SPAG9 regulated by miR-200a-3p might be beneficial to reveal new therapeutic targets for RCC.

miR-195 Inhibits EMT by Targeting FGF2 in Prostate Cancer Cells

Prostate cancer (PCa) is one of the leading causes of deaths in America. The major cause of mortality can be attributed to metastasis. Cancer metastasis involves sequential and interrelated events. miRNAs and epithelial-mesenchymal transition (EMT) are implicated in this process. miR-195 is downregulated in many human cancers. However, the roles of miR-195 in PCa metastasis and EMT remain unclear. In this study, data from Memorial Sloan Kettering Cancer Center (MSKCC) prostate cancer database were re-analysed to detect miR-195 expression and its roles in PCa. miR-195 was then overexpressed in castration-resistant PCa cell lines, DU-145 and PC-3. The role of miR-195 in migration and invasion in vitro was also investigated, and common markers in EMT were evaluated through Western blot analysis. A luciferase reporter assay was conducted to confirm the target gene of miR-195; were validated in PCa cells. In MSKCC data re-analyses, miR-195 was poorly expressed in metastatic PCa; miR-195 could be used to diagnose metastatic PCa by measuring the corresponding expression. Area under the receiver operating characteristic curve (AUC-ROC) was 0.705 (P = 0.017). Low miR-195 expression was characterised with a shorter relapse-free survival (RFS) time. miR-195 overexpression suppressed cell migration, invasion and EMT. Fibroblast growth factor 2 (FGF2) was confirmed as a direct target of miR-195. FGF2 knockdown also suppressed migration, invasion and EMT; by contrast, increased FGF2 partially reversed the suppressive effect of miR-195. And data from ONCOMINE prostate cancer database showed that PCa patients with high FGF2 expression showed shorter RFS time (P = 0.046). Overall, this study demonstrated that miR-195 suppressed PCa cell metastasis by downregulating FGF2. miR-195 restoration may be considered as a new therapeutic method to treat metastatic PCa.

MicroRNA-195 suppresses tumor cell proliferation and metastasis by directly targeting BCOX1 in prostate carcinoma

Elucidation of the downstream targets regulated by the metastasis-suppressive miRNAs can shed light on the metastatic processes in prostate cancer (PCa). We conducted microarray analyses and found that miR-195 was significantly decreased in metastatic PCa. Low miR-195 expression is an independent prognostic factor for poor biochemical recurrence-free and overall survival. Forced expression of miR-195 in PCa cells drastically inhibits proliferation, migration and invasion in vitro and inhibits tumor growth and metastasis in vivo. BCOX1 is identified as a direct target of miR-195 in PCa, and is found to be drastically increased in metastatic PCa. BCOX1 knockdown phenotypically copies miR-195-induced phenotypes, whereas forced expression of BCOX1 reverses the effects of miR-195. Collectively, this is the first report unveils that loss of miR-195 expression and thus uncontrolled BCOX1 upregulation might drive PCa metastasis.

miR-503 suppresses tumor cell proliferation and metastasis by directly targeting RNF31 in prostate cancer

Microarray data analyses were performed to search for metastasis-associated oncogenes in prostate cancer (PCa). RNF31 mRNA expressions in tumor tissues and benign prostate tissues were evaluated. The RNF31 protein expression levels were also analyzed by western blot and immunohistochemistry. Luciferase reporter assays were used to identify miRNAs that can regulate RNF31. The effect of RNF31 on PCa progression was studied in vitro and in vivo. We found that RNF31 was significantly increased in PCa and its expression level was highly correlated with seminal vesicle invasion, clinical stage, prostate specific antigen (PSA) level, Gleason score, and BCR. Silence of RNF31 suppressed PCa cell proliferation and metastasis in vitro and in vivo. miR-503 can directly regulate RNF31. Enforced expression of miR-503 inhibited the expression of RNF31 significantly and the restoration of RNF31 expression reversed the inhibitory effects of miR-503 on PCa cell proliferation and metastasis. These findings collectively indicated an oncogene role of RNF31 in PCa progression which can be regulated by miR-503, suggesting that RNF31 could serve as a potential prognostic biomarker and therapeutic target for PCa.

Disabled homolog 2 is required for migration and invasion of prostate cancer cells

Disabled homolog 2 (DAB2) is frequently deleted or epigenetically silenced in many human cancer cells. Therefore, DAB2 has always been regarded as a tumor suppressor gene. However, the role of DAB2 in tumor progression and metastasis remains unclear. In this study, DAB2 expression was upregulated along with human prostate cancer (PCa) progression. DAB2 overexpression or knockdown effects in LNCaP and PC3 cell lines were verified to address the biological functions of DAB2 in PCa progression and metastasis. LNCaP and PC3 cell lines were generated from human PCa cells with low and high metastatic potentials, respectively. The results showed that DAB2 shRNA knockdown can inhibit the migratory and invasive abilities of PC3 cells, as well as the tumorigenicity, whereas DAB2 overexpression enhanced LNCaP cell migration and invasion. Further investigation showed that DAB2 regulated the cell migration associated genes in PC3 cells, and the differential DAB2 expression between LNCaP and PC3 cells was partly regulated by histone 4 acetylation. Therefore, DAB2 may play an important role in PCa progression and metastasis.