A-kinase Anchor Protein 12 Expression Research Articles

AKAP12 inhibits the proliferation of ovarian cancer by activating the Hippo pathway

Abstract Background Ovarian cancer is a prominent cause of mortality among women worldwide. A kinase anchor protein 12 (AKAP12) has been investigated, but its contribution to ovarian cancer is unclear. Objectives This study comprehensively investigates the role of AKAP12 in ovarian cancer proliferation by elucidating its underlying mechanisms and functions. Methods We compared the expression levels of AKAP12 in ovarian cancer and adjacent tissues. We subsequently established A2780 and HO8910 cell lines that have undergone AKAP12 overexpression or knockdown to verify the function of AKAP12 in ovarian cancer. To determine the effect of AKAP12 on tumorigenicity, migration, and invasion, we performed CCK-8, colony-formation, xenograft models, transwell, and wound healing assays. Furthermore, we used pathway enrichment analysis to identify Hippo signaling related to AKAP12 overexpression. Then we characterized the relevance of Hippo signaling in AKAP12-regulated tumor suppressive effects in ovarian cancer through western blot. Results Our study revealed a significant decrease in AKAP12 expression in ovarian cancer samples. Moreover, functional assays demonstrated the tumor suppressive effects of AKAP12 overexpression, inhibiting cancer cell proliferation, migration, and invasion. Consistent with these findings, mice inoculated with AKAP12-overexpressing cells exhibited slower tumor growth in our mouse xenograft model. We also observed a positive relationship between AKAP12 overexpression and Hippo pathway-related proteins. Conclusions AKAP12 plays a crucial role in the suppression of ovarian cancer through activation of the Hippo signaling pathway. Furthermore, it could be a potential target for developing new therapeutic strategies for ovarian cancer treatment.

Circ_0001777 Affects Triple-negative Breast Cancer Progression Through the miR-95-3p/AKAP12 Axis

BackgroundTriple Negative Breast Cancer (TNBC) is 1 of the most serious cancer. Circular RNA_0001777 (circ_0001777) expression was decreased in TNBC tissues. However, the molecular mechanism of circ_0001777 remains unknown. MethodsThe expression of circ_0001777, microRNA-95-3p (miR-95-3p) and A-kinase anchor protein 12 (AKAP12) were detected by quantitative real-time fluorescence polymerase chain reaction (qRT-PCR). A series of in vitro experiments were designed to explore the function of circ_0001777 in TNBC cells and the regulatory mechanism between circ_0001777 and miR-95-3p and AKAP12 in TNBC cells. Western blot examined the relative protein levels in TNBC cells. Bioinformatics prediction site predicted the relationship between miR-95-3p and circ_0001777 or AKAP12 and was verified by Dual-luciferase reporter assays. The xenotransplantation model was established to study the role of circ_0001777 in vivo. ResultsThe expression of circ_0001777 and AKAP12 was decreased in TNBC tissues, while the expression of miR-95-3p was increased. Circ_0001777 can sponge miR-95-3p, and AKAP12 is the target of miR-95-3p. In vitro complement experiments, overexpression of circ_0001777 significantly decreased the malignant behavior of TNBC, while co-transfection of miR-95-3p partially up-regulated this change. In addition, AKAP12 knockdown increased the proliferation, migration, and invasion of TNBC cells inhibited by overexpression of circ_0001777. Mechanically, circ_0001777 regulates AKAP12 expression in TNBC cells by sponge miR-95-3p. In addition, in vivo studies have shown that overexpression of circ_0001777 inhibits tumor growth. ConclusionOverexpression of circ_0001777 decreased proliferation, migration, and invasion of TNBC cells by regulating the miR-95-3p/AKAP12 axis, suggesting that circ_0001777/miR-95-3p/AKAP12 axis may be a potential regulatory mechanism for the treatment of TNBC.

Comprehensive Analysis of the Immune Implication of AKAP12 in Stomach Adenocarcinoma.

A kinase anchor protein 12 (AKAP12) as a tumor suppressor in various cancers has been extensively studied and confirmed. However, its immune implication in stomach adenocarcinoma (STAD) remains uncertain. Here, using The Cancer Genome Atlas (TCGA), Human Protein Atlas (HPA), Tumor Immune Estimation Resource (TIMER), Cancer Cell Line Encyclopedia (CCLE), integrated repository portal for tumor-immune system interactions (TISIDB), and Search Tool for the Retrieval of Interaction Gene/Proteins (STRING) database, we systematically analyzed the immune correlation of AKAP12 from three aspects including immune infiltration cells, immune-related pathways, and immunomodulators and developed a AKAP12-related 4-gene signature for prognosis prediction. Our results showed that AKAP12 mRNA and protein levels were downregulated in STAD patients, and its expression was positively related to CD4+ T cells and macrophages. In addition, the immune cell infiltration levels were associated with AKAP12 gene copy number deletion in STAD. Based on CCLE database, we found that AKAP12 coexpressed genes were enriched in several immune- and cancer-related pathways, which was further validated by Gene Set Enrichment Analysis (GSEA). Moreover, we identified 46 immunomodulators that were significantly related to AKAP12 expression using TISIDB database, and these immunomodulators were involved in immune-related pathways including Th17 cell differentiation and natural killer cell-mediated cytotoxicity. Additionally, based on the 46 AKAP12-related immunomodulators, a 4-gene risk prediction signature was developed using the Cox regression model. The risk signature was identified as an independent prognostic factor, which can accurately predict the prognosis of patients with STAD, showing good predictive performance. Furthermore, we constructed a prognostic nomogram and calibration to predict and assess patient survival probabilities by integrating the risk score and other clinical factors. In conclusion, our study provides strong evidence that AKAP12 is closely related to tumor immunity in STAD from three aspects: immune infiltration cells, immune pathways, and immunomodulators. More importantly, the AKAP12-related prognostic signature may have a good application prospect for clinical practice.

Pan-cancer analysis of the prognosis and immunological role of AKAP12: A potential biomarker for resistance to anti-VEGF inhibitors.

The primary or acquired resistance to anti-VEGF inhibitors remains a common problem in cancer treatment. Therefore, identifying potential biomarkers enables a better understanding of the precise mechanism. Through the GEO database, three profiles associated with bevacizumab (BV) resistance to ovarian cancer, glioma, and non-small-cell lung carcinoma, respectively, were collected for the screening process, and two genes were found. A-kinase anchor protein 12 (AKAP12), one of these two genes, correlates with tumorigenesis of some cancers. However, the role of AKAP12 in pan-cancer remains poorly defined. The present study first systematically analyzed the association of AKAP12 with anti-VEGF inhibitors’ sensitivity, clinical prognosis, DNA methylation, protein phosphorylation, and immune cell infiltration across various cancers via bioinformatic tools. We found that AKAP12 was upregulated in anti-VEGF therapy-resistant cancers, including ovarian cancer (OV), glioblastoma (GBM), lung cancer, and colorectal cancer (CRC). A high AKAP12 expression revealed dismal prognoses in OV, GBM, and CRC patients receiving anti-VEGF inhibitors. Moreover, AKAP12 expression was negatively correlated with cancer sensitivity towards anti-VEGF therapy. Clinical prognosis analysis showed that AKAP12 expression predicted worse prognoses of various cancer types encompassing colon adenocarcinoma (COAD), OV, GBM, and lung squamous cell carcinoma (LUSC). Gene mutation status may be a critical cause for the involvement of AKAP12 in resistance. Furthermore, lower expression of AKAP12 was detected in nearly all cancer types, and hypermethylation may explain its decreased expression. A decreased phosphorylation of T1760 was observed in breast cancer, clear-cell renal cell carcinoma, and lung adenocarcinoma. For the immunologic significance, AKAP12 was positively related to the abundance of pro-tumor cancer-associated fibroblasts (CAFs) in various types of cancer. The results of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis suggested that “cell junction organization” and “MAPK pathway” participated in the effect of AKAP12. Importantly, we discovered that AKAP12 expression was greatly associated with metastasis of lung adenocarcinoma as well as differential and angiogenesis of retinoblastoma through investigating the single-cell sequencing data. Our study showed that the dual role of AKAP12 in various cancers and AKAP12 could serve as a biomarker of anti-VEGF resistance in OV, GBM, LUSC, and COAD.

AKAP12/Gravin is over-expressed in patients with ulcerative colitis

The gene of A-kinase anchor protein 12 (AKAP12) regulates cell cycle progression, cell motility, and morphology through its multiple scaffolding domains. However, the role of AKAP12 expression in ulcerative colitis (UC) patients has not been yet described. The aim of the study was to describe the gene and protein of AKAP12 expression in patients with UC and its association regarding the disease severity. We included a total of 40 patients with confirmed diagnosis of UC and 25 controls without endoscopic evidence of colitis or neoplasia. The relative quantification of the gene expression was performed by real-time PCR for AKAP12. Kruskal-Wallis was used to test differences among groups, and Spearman correlation to assess the relationship between AKAP12 gene and clinical outcomes. The extent of disease was evaluated using total colonoscopy, and biopsies were taken from rectum segments. The AKAP12 gene expression was increased in colonic mucosa from patients with active UC when compared with UC remission and control group. The overexpression of AKAP12 in patients with UC was associated with the presence of extensive colitis (p = 0.04, RM = 12, IC = 1.29-186.37). AKAP12/CD16 double positive cells were higher in submucosa (p = 0.04), muscular (p < 0.001), and cells from serosa (p < 0.001) in patients affected by UC in comparison to controls. The overexpression of AKAP12 was associated with the extent of disease. This is the first report about the role of AKAP12 in patients with UC suggesting that this gene and its protein could be involved in the modulation of the disease.

AKAP12 Supports Blood-Brain Barrier Integrity against Ischemic Stroke.

A-kinase anchor protein 12 (AKAP12) is a scaffolding protein that associates with intracellular molecules to regulate multiple signal transductions. Although the roles of AKAP12 in the central nervous system are still relatively understudied, it was previously shown that AKAP12 regulates blood-retinal barrier formation. In this study, we asked whether AKAP12 also supports the function and integrity of the blood-brain barrier (BBB). In a mouse model of focal ischemia, the expression level of AKAP12 in cerebral endothelial cells was upregulated during the acute phase of stroke. Also, in cultured cerebral endothelial cells, oxygen-glucose deprivation induced the upregulation of AKAP12. When AKAP12 expression was suppressed by an siRNA approach in cultured endothelial cells, endothelial permeability was increased along with the dysregulation of ZO-1/Claudin 5 expression. In addition, the loss of AKAP12 expression caused an upregulation/activation of the Rho kinase pathway, and treatment of Rho kinase inhibitor Y-27632 mitigated the increase of endothelial permeability in AKAP12-deficient endothelial cell cultures. These in vitro findings were confirmed by our in vivo experiments using Akap12 knockout mice. Compared to wild-type mice, Akap12 knockout mice showed a larger extent of BBB damage after stroke. However, the inhibition of rho kinase by Y-27632 tightened the BBB in Akap12 knockout mice. These data may suggest that endogenous AKAP12 works to alleviate the damage and dysfunction of the BBB caused by ischemic stress. Therefore, the AKAP12-rho-kinase signaling pathway represents a novel therapeutic target for stroke.

A-kinase anchor protein 12 (AKAP12) inhibits cell migration in breast cancer

A-kinase anchor protein 12 (AKAP12) also known as Gravin and SSeCKS, is a novel potent scaffold protein for many key signaling factors, such as protein kinase C (PKC), PKA, cyclins as well as F-actin. AKAP12 expression is known to be suppressed in several human malignancies including breast, prostate, gastric and colon cancers. In this study, we evaluated the role of AKAP12 in the migration of breast cancer cells, an important cellular process in cancer progression. AKAP12 gene expression was analyzed in human breast cancer tissues using the Gene expression-based Outcome for Breast cancer Online (GOBO) database and TissueScan array, followed by relapse free survival (RFS) analysis with the Kaplan-Meier Plotter. AKAP12 protein was then analyzed in normal MCF10A breast cell line and six different breast cancer cell lines (AU565, Hs578T, MCF7, MDA-MB-231, T47D and ZR751). After which, siRNA-mediated knockdown of AKAP12 was carried out in MCF10A, MDA-MB-231 and Hs578T cells, followed by phenotypic assays. AKAP12 was observed to be reduced in breast cancer tissues as analyzed by GOBO and TissueScan array. Kaplan Meier survival analysis revealed that patients with AKAP12 gene expression had a higher RFS survival. There was also decreased AKAP12 protein expression in breast cancer cell lines compared to MCF10A normal epithelial breast cell line. Knockdown of AKAP12 in both MCF10A cells and Hs578T cells induced cell migration but did not alter cell proliferation. Moreover, siAKAP12 in aggressive MDA-MB-231 breast cancer cells led to an increase in cell migration. Immunofluorescence analysis of AKAP12 depleted MCF10A cells also revealed formation of thick stress fibers which could affect cell migration. Hence, the findings in this study suggest that AKAP12 is a potential metastasis suppressor in breast cancer.

Altered AKAP12 expression in portal fibroblasts and liver sinusoids mediates transition from hepatic fibrogenesis to fibrosis resolution

Liver fibrosis can be reversed by removing its causative injuries; however, the molecular mechanisms mediating the resolution of liver fibrogenesis are poorly understood. We investigate the role of a scaffold protein, A-Kinase Anchoring Protein 12 (AKAP12), during liver fibrosis onset, and resolution. Biliary fibrogenesis and fibrosis resolution was induced in wild-type (WT) or AKAP12-deficient C57BL/6 mice through different feeding regimens with 0.1% 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-containing chow. AKAP12 expression in portal fibroblasts (PFs) and liver sinusoidal endothelial cells (LSECs) gradually decreased as fibrosis progressed but was restored after cessation of the fibrotic challenge. Histological analysis of human liver specimens with varying degrees of fibrosis of different etiologies revealed that AKAP12 expression diminishes in hepatic fibrosis from its early stages onward. AKAP12 KO mice displayed reduced fibrosis resolution in a DDC-induced biliary fibrosis model, which was accompanied by impaired normalization of myofibroblasts and capillarized sinusoids. RNA sequencing of the liver transcriptome revealed that genes related to ECM accumulation and vascular remodeling were mostly elevated in AKAP12 KO samples. Gene ontology (GO) and bioinformatic pathway analyses identified that the differentially expressed genes were significantly enriched in GO categories and pathways, such as the adenosine 3′,5′-cyclic monophosphate (cAMP) pathway. Knockdown of the AKAP12 gene in cultured primary PFs revealed that AKAP12 inhibited PF activation in association with the adenosine 3′,5′-cyclic monophosphate (cAMP) pathway. Moreover, AKAP12 knockdown in LSECs led to enhanced angiogenesis, endothelin-1 expression and alterations in laminin composition. Collectively, this study demonstrates that AKAP12-mediated regulation of PFs and LSECs has a central role in resolving hepatic fibrosis.

A‐Kinase Anchoring Protein Phosphorylation as a Therapeutic Target for Alcohol Liver Injury

Hepatic stellate cells (HSC) activation associated with up‐regulation of type I collagen is a distinct molecular response in alcoholic liver diease (ALD). A‐kinase anchoring protein 12 (AKAP12) is a scaffold protein for protein kinases A/C (PKA/PKC) and cyclin‐D1 that suppresses oncogenic proliferation, chemotaxis and cellular senescence. The scaffolding activity of AKAP12 is altered by site‐specific phosphorylation that leads to loss of its interaction with PKC and cyclin‐D1 allowing release of cyclin‐D1 for cell cycle progression. AKAP12 tyrosine phosphorylation alters its binding to actin favoring cell motility. AKAP12 expression is induced during HSC activation but its scaffolding functions in liver function are undescribed so far. We identified increased levels of AKAP12 phosphorylation in ethanol‐treated HSCs and hence hypothesized that this may be associated with altered scaffolding functions in alcohol‐mediated HSC activation and liver injury. AKAP12 expression/interaction/phosphorylation was assayed in in vitro and in vivo ethanol models/human subjects by real‐time PCR, co‐immunoprecipitation‐immunoblotting, phospho‐proteomics/phosTag™/proximity ligation assays. Ethanol induced AKAP12 phosphorylation primarily in HSCs of mouse liver, but not hepatocytes. AKAP12 phosphorylation was also observed in alcoholic hepatitis/cirrhosis patient livers. AKAP12's scaffolding activity for PKC‐α/cyclin‐D1 was inhibited in ethanol‐treated HSCs but not hepatocytes. AKAP12 acted as an anti‐fibrogenic protein inhibiting HSC activation, however, ethanol reversed this anti‐fibrogenic property through induction of AKAP12 phosphorylation. One mechanism of AKAP12's ability to control HSC activation was by its interaction with heat shock protein 47 (HSP47) that chaperones collagen and induces its secretion. Ethanol inhibited AKAP12‐HSP47 and induced HSP47‐collagen interaction. Ethanol‐induced, phospho‐AKAP12 adducts were unable to bind to HSP47 compared to its unphosphorylated counterpart, thereby proving that ethanol‐mediated phosphorylation of AKAP12 inhibited the HSP47‐AKAP12 scaffold. Silencing AKAP12 facilitated the chaperoning of collagen by HSP47. Hence, AKAP12 scaffolds HSP47 and regulates collagen‐HSP47 interaction and this ability is quenched by ethanol through phosphorylation. The findings implicate important functions of AKAP12 in controlling HSP47/collagen maturation that is deregulated by its phosphorylation. By phosphopeptide mapping, we identified novel ethanol‐responsive AKAP12 phospho‐sites in human HSCs that may be further explored as therapeutic targets in ALD.Support or Funding InformationKomal Ramani: (Applied Cell Biology and Physiology (ACB&amp;P) division seed funding, Biomedical Sciences Department, Cedars‐Sinai Medical Center, active)Komal Ramani (5R00AA017774‐05, NIH, complete)Maria Lauda Tomasi: (K01AA022372, NIH, active)Nirmala Mavila (Applied Cell Biology and Physiology (ACB&amp;P) division seed funding, Biomedical Sciences Department, Cedars‐Sinai Medical Center)Zhaoli Sun (R24AA025017, NIAAA supported Clinical Resource for Alcoholic Hepatitis Investigations, Johns Hopkins University, active).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Blockage of AKAP12 accelerates angiotensin II (Ang II)-induced cardiac injury in mice by regulating the transforming growth factor β1 (TGF-β1) pathway

Hypertension is a multifactorial chronic inflammatory disease that leads to cardiac remodeling. A-kinase anchor protein 12 (AKAP12) is a scaffolding protein that has multiple functions in various biological events, including the regulation of vessel integrity and differentiation of neural barriers in blood. However, the role of AKAP12 in angiotensin II (Ang II)-induced cardiac injury remains unclear. In the present study, Ang II infusion reduced AKAP12 expressions in the hearts of wild-type (WT) mice, and AKAP12 knockout (KO) enhanced the infiltration of inflammatory cells. In addition, AKAP12 deletion accelerated Ang II-induced cardiac histologic alterations and dysfunction. Further, AKAP12−/− aggravated heart failure by promoting the inflammation, oxidative stress, cellular apoptosis, and autophagy induced by Ang II. Furthermore, AKAP12 KO elevated Ang II-induced cardiac fibrosis, as indicated by the following: (1) Masson trichrome staining showed that Ang II infusion markedly increased fibrotic areas of the WT mouse heart, which was greatly accelerated in AKAP12−/− mice; (2) immunohistochemistry analysis showed increased expression of transforming growth factor β1 (TGF-β1) and α-smooth muscle actin (α-SMA) in the AKAP12−/− mouse heart; (3) reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR) analysis showed increased expression of fibrosis-related molecules in the AKAP12-deficient mouse heart; and (4) Western blot analysis indicated significantly higher upregulation of p-SMAD2/3 in the AKAP12−/− mouse heart. In vitro, AKAP12 knockdown in HL-1 cells was responsible for TGF-β1-induced inflammation, the generation of reactive oxygen species (ROS), apoptosis, autophagy, and fibrosis. Furthermore, overexpression of AKAP12 reduced fibrosis triggered by TGF-β1 in cells. Overall, our study suggests that fibrosis induced by Ang II may be alleviated by AKAP12 expression through inactivation of the TGF-β1 pathway.

Kinome and phosphoproteome of high-grade meningiomas reveal AKAP12 as a central regulator of aggressiveness and its possible role in progression

There is a need to better understand meningioma oncogenesis for biomarker discovery and development of targeted therapies. Histological or genetic criteria do not accurately predict aggressiveness. Post-translational studies in meningioma progression are lacking. In the present work, we introduce a combination of mass spectrometry-based phosphoproteomics and peptide array kinomics to profile atypical and anaplastic (high-grade) meningiomas. In the discovery set of fresh-frozen tissue specimens (14), the A-kinase anchor protein 12 (AKAP12) protein was found downregulated across the grades. AKAP12 knockdown in benign meningioma cells SF4433 increases proliferation, cell cycle, migration, invasion, and confers an anaplastic profile. Differentially regulated pathways were characteristic of high-grade meningiomas. Low AKAP12 expression in a larger cohort of patients (75) characterized tumor invasiveness, recurrence, and progression, indicating its potential as a prognostic biomarker. These results demonstrate AKAP12 as a central regulator of meningioma aggressiveness with a possible role in progression.

Role of A-Kinase Anchoring Protein Phosphorylation in Alcohol-Induced Liver Injury and Hepatic Stellate Cell Activation

Alcoholic liver injury is associated with hepatic stellate cell (HSC) activation. A-kinase anchoring protein 12 (AKAP12) scaffolds protein kinase C and cyclin-D1, which is regulated by its phosphorylation, and spatiotemporally controls cell proliferation, invasiveness, and chemotaxis. HSC activation induces AKAP12 expression, but the role of AKAP12's scaffolding activity in liver function is unknown. Because AKAP12 phosphorylation is enhanced in ethanol-treated HSCs, we examined AKAP12's scaffolding functions in alcohol-mediated HSC activation and liver injury. AKAP12 expression, interaction, and phosphorylation were assayed in invitro and invivo ethanol models and human subjects by real-time PCR, coimmunoprecipitation, immunoblotting, and phosphorylated proteomics/Phos-tag. Ethanol induced AKAP12 phosphorylation in the liver and in primary HSCs, but not in hepatocytes. AKAP12's scaffolding activity for protein kinase C/cyclin-D1 decreased in ethanol-treated HSCs but not hepatocytes. AKAP12 negatively regulated HSC activation, which was reversed by ethanol-mediated AKAP12 phosphorylation. AKAP12 interacted with heat shock protein 47 (HSP47), which chaperones collagen and induces its secretion. Ethanol inhibited AKAP12-HSP47 and induced HSP47-collagen interaction. Ethanol-induced phosphorylated AKAP12 was unable to bind to HSP47 compared with its unphosphorylated counterpart, thereby proving that ethanol-mediated phosphorylation of AKAP12 inhibited the HSP47-AKAP12 scaffold. Silencing AKAP12 facilitated the chaperoning of collagen by HSP47. Hence, AKAP12 scaffolds HSP47 and regulates collagen-HSP47 interaction. Ethanol quenches AKAP12's scaffolding activity through phosphorylation and facilitates HSC activation.

Differential Expression of the Tumor Suppressor A-Kinase Anchor Protein 12 in Human Diffuse and Pilocytic Astrocytomas Is Regulated by Promoter Methylation

The scaffold protein A-kinase anchor protein 12 (AKAP12) exerts tumor suppressor activity and is downregulated in several tumor entities. We characterized AKAP12 expression and regulation in astrocytomas, including pilocytic and diffusely infiltrating astrocytomas. We examined 194 human gliomas and 23 normal brain white matter samples by immunohistochemistry or immunoblotting for AKAP12 expression. We further performed quantitative methylation analysis of the AKAP12 promoter by MassARRAY® of normal brain, World Health Organization (WHO) grade I to IV astrocytomas, and glioma cell lines. Our results show that AKAP12 is expressed in a perivascular distribution in normal CNS, strongly upregulated in tumor cells in pilocytic astrocytomas, and weakly expressed in diffuse astrocytomas of WHO grade II to IV. Methylation analyses revealed specific hypermethylation of AKAP12α promoter in WHO grade II to IV astrocytomas. Restoration experiments using 5-aza-2'-deoxycytidine in primary glioblastoma cells decreased AKAP12α promoter methylation and markedly increased AKAP12α mRNA levels. In summary, we demonstrate that AKAP12 is differentially expressed in human astrocytomas showing high expression in pilocytic but low expression in diffuse astrocytomas of all WHO-grades. Our results further indicate that epigenetic mechanisms are involved in silencing AKAP12 in diffuse astrocytomas; however, a tumor suppressive role of AKAP12 in distinct astrocytoma subtypes remains to be determined.

Inhibition of endothelial cell migration through the down‑regulation of MMP-9 by A-kinase anchoring protein 12

Matrix metalloproteinases (MMPs) play an important role in the degradation of extracellular matrix (ECM) molecules. ECM degradation is associated with tumor metastasis and angiogenesis. Therefore, the regulation of MMPs is of potential benefit in the treatment of various diseases, including cancer. A-kinase anchoring protein 12 (AKAP12) has been identified as a potential tumor suppressor. However, the function of AKAP12 as a tumor suppressor is not well understood. Herein, to determine the relationship between AKAP12 and MMP-9 in cancer, we first investigated the expression of MMP-9 under normoxic and hypoxic conditions in human fibrosarcoma cells. The expression of MMP-9 was not detected under normoxic conditions.; however, it was markedly increased under hypoxia in HT1080 cells. The effect of AKAP12 on the expression of MMP-9 was subsequently investigated. Hypoxia-induced MMP-9 mRNA expression was significantly reduced by overexpression of AKAP12, as was MMP-9 protein expression. In addition, when the AKAP12 transfectant-conditioned media (CM) were transferred into human endothelial cells, cell migration was significantly inhibited compared to the control group. Notably, the inhibition of AKAP12 expression by siRNA targeting AKAP12 resulted in an increase in the expression of active MMP-2 under normoxia, as well as of MMP-9. Endothelial cell migration was also strongly increased by treatment with CM of siRNA against AKAP12, as compared to the control group. Taken together, the results indicate that AKAP12 is involved in the regulation of endothelial cell migration through the inhibitory regulation of MMP-9 expression in tumor cells.

Down-regulation of tumor suppressor a kinase anchor protein 12 in human hepatocarcinogenesis by epigenetic mechanisms

The A kinase anchor protein 12 (AKAP12) is a central mediator of protein kinase A and protein kinase C signaling. Although AKAP12 has been described to act as a tumor suppressor and its expression is frequently down-regulated in several human malignancies, the underlying molecular mechanisms responsible for the AKAP12 reduction are poorly understood. We therefore analyzed the expression of AKAP12 and its genetic and epigenetic regulatory mechanisms in human hepatocarcinogenesis. Based on tissue microarray analyses (n = 388) and western immunoblotting, we observed a significant reduction of AKAP12 in cirrhotic liver (CL), premalignant lesions (DN), and hepatocellular carcinomas (HCCs) compared to histologically normal liver specimens (NL). Analyses of array comparative genomic hybridization data (aCGH) from human HCCs revealed chromosomal losses of AKAP12 in 36% of cases but suggested additional mechanisms underlying the observed reduction of AKAP12 expression in hepatocarcinogenesis. Quantitative methylation analysis by MassARRAY of NL, CL, DN, and HCC tissues, as well as of various tumorigenic and nontumorigenic liver cell lines revealed specific hypermethylation of the AKAP12α promoter but not of the AKAP12β promoter in HCC specimens and in HCC cell lines. Consequently, restoration experiments performed with 5-aza-2'deoxycytidine drastically increased AKAP12α mRNA levels in a HCC cell line (AKN1) paralleled by AKAP12α promoter demethylation. As hypermethylation is not observed in CL and DN, we investigated microRNA-mediated posttranscriptional regulation as an additional mechanism to explain reduced AKAP12 expression. We found that miR-183 and miR-186 are up-regulated in CL and DN and are able to target AKAP12. In addition to genetic alterations, epigenetic mechanisms are responsible for the reduction of the tumor suppressor gene AKAP12 in human hepatocarcinogenesis.

A-kinase anchoring protein 12 and tumors

A-kinase anchoring protein 12 (AKAP12) ,is a kind of cell scaffold proteins,and can organize the complex of protein kinase A(PKA) and PKC as well as other signal molecules such as cyclin D1,and it is an important regulator of the β2-adrenergic receptor complex,which demonstrates the participation of AKAP12 in diverse signal transduction pathways.AKAP12 contains deletions or downregulation in variours tumors,including prostate cancers,gastric carcinomas and esophagus cancer,suggesting that the inactivation of AKAP12 expression may be linked to oncogenesis.AKAP12 is also a potential suppressor gene in metastasis of cancers. Key words: Neoplasms; A kinase anchor proteins

AKAP12 Regulates Human Blood–Retinal Barrier Formation by Downregulation of Hypoxia-Inducible Factor-1α

Many diseases of the eye such as retinoblastoma, diabetic retinopathy, and retinopathy of prematurity are associated with blood-retinal barrier (BRB) dysfunction. Identifying the factors that contribute to BRB formation during human eye development and maintenance could provide insights into such diseases. Here we show that A-kinase anchor protein 12 (AKAP12) induces BRB formation by increasing angiopoietin-1 and decreasing vascular endothelial growth factor (VEGF) levels in astrocytes. We reveal that AKAP12 downregulates the level of hypoxia-inducible factor-1alpha (HIF-1alpha) protein by enhancing the interaction of HIF-1alpha with pVHL (von Hippel-Lindau tumor suppressor protein) and PHD2 (prolyl hydroxylase 2). Conditioned media from AKAP12-overexpressing astrocytes induced barriergenesis by upregulating the expression of tight junction proteins in human retina microvascular endothelial cells (HRMECs). Compared with the retina during BRB maturation, AKAP12 expression in retinoblastoma patient tissue was markedly reduced whereas that of VEGF was increased. These findings suggest that AKAP12 may induce BRB formation through antiangiogenesis and barriergenesis in the developing human eye and that defects in this mechanism can lead to a loss of tight junction proteins and contribute to the development of retinal pathologies such as retinoblastoma.

AKAP12α is AssoCiated with Promoter Methylation in Lung Cancer

Promoter methylation is an important mechanism for silencing tumor-suppressor genes in cancer and it is a promising tool for the development of molecular biomarkers. The purpose of the present study was to investigate whether inactivation of the A Kinase Anchoring Protein 12 (AKAP12) gene is assoCiated with promoter methylation in lung cancer. The AKAP12 expression was examined by reverse transcription-polymerase chain reaction (RT-PCR) in ten lung cancer cell lines. The methylation status of the AKAP12alpha promoter was analyzed by performing bisulfite sequencing analysis in ten lung cancer cell lines, twenty four lung tissues and matched normal tissues. The AKAP12alpha expression was reduced in 6 of 10 (60%) lung cancer cell lines, whereas the AKAP12beta expression was absent in 1 of 10 (10%) lung cancer cell lines. The AKAP12alpha expression was restored after treatment with the demethylating agent 5-aza-2'-deoxycytidine in three lung cancer cell lines. Methylation of CpG island 1 in the AKAP12alpha promoter was detected in 30% of the lung cancer cell lines, whereas methylation of CpG island 2 in the AKAP12alpha promoter was observed in the immortalized bronchial cell line and in all the lung cancer cell lines. In lung tumors, the CpG island 1 in the AKAP12alpha promoter was infrequently methylated. However, CpG island 2 in the AKAP12alpha promoter was highly methylated in lung tumors compared with the surrounding normal tissues, and this was statistically significant (p=0.0001). Our results suggest that inactivation of the AKAP12alpha expression is assoCiated with DNA methylation of the promoter region in lung cancer, and that AKAP12alpha may play an important role in lung cancer carcinogenesis.