CRISPRpas: programmable regulation of alternative polyadenylation by dCas9

Most human protein-coding genes produce alternative polyadenylation (APA) isoforms that differ in 3' UTR size or, when coupled with splicing, have variable coding sequences. APA is an important layer of gene expression program critical for defining cell identity. Here, by using a catalytically dead Cas9 and coupling its target site with polyadenylation site (PAS), we develop a method, named CRISPRpas, to alter APA isoform abundance. CRISPRpas functions by enhancing proximal PAS usage, whose efficiency is influenced by several factors, including targeting strand of DNA, distance between PAS and target sequence and strength of the PAS. For intronic polyadenylation (IPA), splicing features, such as strengths of 5' splice site and 3' splice site, also affect CRISPRpas efficiency. We show modulation of APA of multiple endogenous genes, including IPA of PCF11, a master regulator of APA and gene expression. In sum, CRISPRpas offers a programmable tool for APA regulation that impacts gene expression.

Proteomic analysis of mitochondrial biogenesis in cardiomyocytes differentiated from human induced pluripotent stem cells

Mitochondria play key roles in the differentiation and maturation of human cardiomyocytes (CMs). As human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) hold potential in the treatment of heart diseases, we sought to identify key mitochondrial pathways and regulators, which may provide targets for improving cardiac differentiation and maturation. Proteomic analysis was performed on enriched mitochondrial protein extracts isolated from hiPSC-CMs differentiated from dermal fibroblasts (dFCM) and cardiac fibroblasts (cFCM) at time points between 12 and 115 days of differentiation, and from adult and neonatal mouse hearts. Mitochondrial proteins with a twofold change at time points up to 120 days relative to 12 days were subjected to ingenuity pathway analysis (IPA). The highest upregulation was in metabolic pathways for fatty acid oxidation (FAO), the tricarboxylic acid (TCA) cycle, oxidative phosphorylation (OXPHOS), and branched chain amino acid (BCAA) degradation. The top upstream regulators predicted to be activated were peroxisome proliferator-activated receptor γ coactivator 1 α (PGC1-α), the insulin receptor (IR), and the retinoblastoma protein (Rb1) transcriptional repressor. IPA and immunoblotting showed upregulation of the mitochondrial LonP1 protease-a regulator of mitochondrial proteostasis, energetics, and metabolism. LonP1 knockdown increased FAO in neonatal rat ventricular cardiomyocytes (nRVMs). Our results support the notion that LonP1 upregulation negatively regulates FAO in cardiomyocytes to calibrate the flux between glucose and fatty acid oxidation. We discuss potential mechanisms by which IR, Rb1, and LonP1 regulate the metabolic shift from glycolysis to OXPHOS and FAO. These newly identified factors and pathways may help in optimizing the maturation of iPSC-CMs.

Widespread transcript shortening through alternative polyadenylation in secretory cell differentiation

Most eukaryotic genes produce alternative polyadenylation (APA) isoforms. Here we report that, unlike previously characterized cell lineages, differentiation of syncytiotrophoblast (SCT), a cell type critical for hormone production and secretion during pregnancy, elicits widespread transcript shortening through APA in 3'UTRs and in introns. This global APA change is observed in multiple in vitro trophoblast differentiation models, and in single cells from placentas at different stages of pregnancy. Strikingly, the transcript shortening is unrelated to cell proliferation, a feature previously associated with APA control, but instead accompanies increased secretory functions. We show that 3'UTR shortening leads to transcripts with higher mRNA stability, which augments transcriptional activation, especially for genes involved in secretion. Moreover, this mechanism, named secretion-coupled APA (SCAP), is also executed in B cell differentiation to plasma cells. Together, our data indicate that SCAP tailors the transcriptome during formation of secretory cells, boosting their protein production and secretion capacity.

Abstract 886: Mitochondrial Stress Response by Lonp1 in Cardiac Function and Protection

LonP1 is a mitochondrial protease that is crucial for maintaining cardiac mitochondrial homeostasis. We recently showed that LonP1 mediates cardioprotection during cardiac ischemia-reperfusion (I/R) by reducing oxidative stress and infarct size. We hypothesize that LonP1 promotes mitochondrial biogenesis during cardiac differentiation and development and protects the heart from oxidative injury by recalibrating bioenergetics. Here, we employ human induced pluripotent stem cells differentiated into cardiomyocytes (iPSC-CMs), rat neonatal ventricular myocytes (rNVMs), and mouse models with cardiac-specific LonP1 overexpression (LonTg) and heterozygous LonP1 knockout ( LONP1 +/- ). In iPSC-CMs, LonP1 is induced 4.8-fold at 39 vs. 12 days after differentiation. During the maturation of murine hearts, LonP1 is increased 4.6-fold at 3 months vs. during 1 day. Upregulation was also observed in rNVMs in which LonP1 is induced 5- fold after 5 days culturing, compared to 0 days. LonP1 induction in rNVMs is accompanied by substantial 2-fold upregulation of mitochondrial transcripts, MT-CYB and MT-COI. However, the levels of another mitochondrial matrix protease ClpP was not altered, suggesting that LonP1 specifically may play an important role during mitochondrial biogenesis and proteostasis in the heart. In vivo, LonTg protected the myocardium against ischemia-reperfusion (I/R) injury by preventing oxidative damage. In LonTg hearts, basal complex I activity was significantly (p<0.05) reduced (Ntg-0.01 ± 0.001 vs. LonTg-0.0078 ± 0.001 mOD/min), as well as during I/R (Ntg-0.0139 ± 0.0005 vs LonTg-0.0102 ± 0.001 mOD/min) (n=3 each). However, no difference was observed in the complex I activity in LONP1 +/+ (0.0118 ± 0.0 mOD/min) and LONP1 +/- (0.0121 ± 0.0 mOD/min) mice (n=3 each). In addition, our preliminary native gel data of LonTg hearts shows a 40% reduction (n=1) in the levels of mitochondrial supercomplexes, compared to NTg hearts (n=4). Further studies are underway to explore the role of LonP1 during differentiation, and in response to mitochondrial cardiac stress. Together, our findings show a novel role of LonP1 in regulating cardiac function during mitochondrial biogenesis and in mitigating cardiac stress-induced injury.

An alternative mitophagy pathway mediated by Rab9 protects the heart against ischemia

Energy stress, such as ischemia, induces mitochondrial damage and death in the heart. Degradation of damaged mitochondria by mitophagy is essential for the maintenance of healthy mitochondria and survival. Here, we show that mitophagy during myocardial ischemia was mediated predominantly through autophagy characterized by Rab9-associated autophagosomes, rather than the well-characterized form of autophagy that is dependent on the autophagy-related 7 (Atg) conjugation system and LC3. This form of mitophagy played an essential role in protecting the heart against ischemia and was mediated by a protein complex consisting of unc-51 like kinase 1 (Ulk1), Rab9, receptor-interacting serine/thronine protein kinase 1 (Rip1), and dynamin-related protein 1 (Drp1). This complex allowed the recruitment of trans-Golgi membranes associated with Rab9 to damaged mitochondria through S179 phosphorylation of Rab9 by Ulk1 and S616 phosphorylation of Drp1 by Rip1. Knockin of Rab9 (S179A) abolished mitophagy and exacerbated the injury in response to myocardial ischemia, without affecting conventional autophagy. Mitophagy mediated through the Ulk1/Rab9/Rip1/Drp1 pathway protected the heart against ischemia by maintaining healthy mitochondria.

Effect of densely ionizing radiation on cardiomyocyte differentiation from human-induced pluripotent stem cells

The process of human cardiac development can be faithfully recapitulated in a culture dish with human pluripotent stem cells, where the impact of environmental stressors can be evaluated. The consequences of ionizing radiation exposure on human cardiac differentiation are largely unknown. In this study, human-induced pluripotent stem cell cultures (hiPSCs) were subjected to an external beam of 3.7 MeV α-particles at low mean absorbed doses of 0.5, 3, and 10 cGy. Subsequently, the hiPSCs were differentiated into beating cardiac myocytes (hiPSC-CMs). Pluripotent and cardiac markers and morphology did not reveal differences between the irradiated and nonirradiated groups. While cell number was not affected during CM differentiation, cell number of differentiated CMs was severely reduced by ionizing radiation in a dose-responsive manner. β-adrenergic stimulation causes calcium (Ca²⁺) overload and oxidative stress. Although no significant increase in Ca²⁺ transient amplitude was observed in any group after treatment with 1 μmol/L isoproterenol, the incidence of spontaneous Ca²⁺ waves/releases was more frequent in hiPSC-CMs of the irradiated groups, indicating arrhythmogenic activities at the single cell level. Increased transcript expression of mitochondrial biomarkers (LONP1, TFAM) and mtDNA-encoded genes (MT-CYB, MT-RNR1) was detected upon differentiation of hiPSC-CMs suggesting increased organelle biogenesis. Exposure of hiPSC-CM cultures to 10 cGy significantly upregulated MT-CYB and MT-RNR1 expression, which may reflect an adaptive response to ionizing radiation. Our results indicate that important aspects of differentiation of hiPSCs into cardiac myocytes may be affected by low fluences of densely ionizing radiations such as α-particles.

Interferon regulatory factor 5 (IRF5) suppresses hepatitis C virus (HCV) replication and HCV-associated hepatocellular carcinoma

Hepatitis C virus (HCV) infection is a major risk factor for the development of chronic liver disease. The disease typically progresses from chronic HCV to fibrosis, cirrhosis, hepatocellular carcinoma (HCC), and death. Chronic inflammation associated with HCV infection is implicated in cirrhosis and HCC, but the molecular players and signaling pathways contributing to these processes remain largely unknown. Interferon regulatory factor 5 (IRF5) is a molecule of interest in HCV-associated HCC because it has critical roles in virus-, Toll-like receptor (TLR)-, and IFN-induced signaling pathways. IRF5 is also a tumor suppressor, and its expression is dysregulated in several human cancers. Here, we present first evidence that IRF5 expression and signaling are modulated during HCV infection. Using HCV infection of human hepatocytes and cells with autonomously replicating HCV RNA, we found that levels of IRF5 mRNA and protein expression were down-regulated. Of note, reporter assays indicated that IRF5 re-expression inhibited HCV protein translation and RNA replication. Gene expression analysis revealed significant differences in the expression of cancer pathway mediators and autophagy proteins rather than in cytokines between IRF5- and empty vector-transfected HCV replicon cells. IRF5 re-expression induced apoptosis via loss in mitochondrial membrane potential, down-regulated autophagy, and inhibited hepatocyte cell migration/invasion. Analysis of clinical HCC specimens supports a pathologic role for IRF5 in HCV-induced HCC, as IRF5 expression was down-regulated in livers from HCV-positive versus HCV-negative HCC patients or healthy donor livers. These results identify IRF5 as an important suppressor of HCV replication and HCC pathogenesis.

Transient receptor potential cation 3 channel regulates melanoma proliferation and migration

Melanoma has an extremely poor prognosis due to its rapidly progressive and highly metastatic nature. Several therapeutic drugs have recently become available, but are effective only against melanoma with specific BRAF gene mutation. Thus, there is a need to identify other target molecules. We show here that Transient receptor potential, canonical 3 (TRPC3) is widely expressed in human melanoma. We found that pharmacological inhibition of TRPC3 with a pyrazole compound, Pyr3, decreased melanoma cell proliferation and migration. Similar inhibition was observed when the TRPC3 gene was silenced with short-hairpin RNA (shRNA). Pyr3 induced dephosphorylation of signal transducer and activator of transcription (STAT) 5 and Akt. Administration of Pyr3 (0.05 mg/kg) to mice implanted with human melanoma cells (C8161) significantly inhibited tumor growth. Our findings indicate that TRPC3 plays an important role in melanoma growth, and may be a novel target for treating melanoma in patients.

Epac1 increases migration of endothelial cells and melanoma cells via FGF2-mediated paracrine signaling

Fibroblast growth factor (FGF2) regulates endothelial and melanoma cell migration. The binding of FGF2 to its receptor requires N-sulfated heparan sulfate (HS) glycosamine. We have previously reported that Epac1, an exchange protein activated by cAMP, increases N-sulfation of HS in melanoma. Therefore, we examined whether Epac1 regulates FGF2-mediated cell–cell communication. Conditioned medium (CM) of melanoma cells with abundant expression of Epac1 increased migration of human umbilical endothelial cells (HUVEC) and melanoma cells with poor expression of Epac1. CM-induced increase in migration was inhibited by antagonizing FGF2, by the removal of HS and by the knockdown of Epac1. In addition, knockdown of Epac1 suppressed the binding of FGF2 to FGF receptor in HUVEC, and in vivo angiogenesis in melanoma. Furthermore, knockdown of Epac1 reduced N-sulfation of HS chains attached to perlecan, a major secreted type of HS proteoglycan that mediates the binding of FGF2 to FGF receptor. These data suggested that Epac1 in melanoma cells regulates melanoma progression via the HS–FGF2-mediated cell–cell communication.

Store-operated Ca2+ entry (SOCE) regulates melanoma proliferation and cell migration

Store-operated Ca²⁺ entry (SOCE) is a major mechanism of Ca²⁺ import from extracellular to intracellular space, involving detection of Ca²⁺ store depletion in endoplasmic reticulum (ER) by stromal interaction molecule (STIM) proteins, which then translocate to plasma membrane and activate Orai Ca²⁺ channels there. We found that STIM1 and Orai1 isoforms were abundantly expressed in human melanoma tissues and multiple melanoma/melanocyte cell lines. We confirmed that these cell lines exhibited SOCE, which was inhibited by knockdown of STIM1 or Orai1, or by a pharmacological SOCE inhibitor. Inhibition of SOCE suppressed melanoma cell proliferation and migration/metastasis. Induction of SOCE was associated with activation of extracellular-signal-regulated kinase (ERK), and was inhibited by inhibitors of calmodulin kinase II (CaMKII) or Raf-1, suggesting that SOCE-mediated cellular functions are controlled via the CaMKII/Raf-1/ERK signaling pathway. Our findings indicate that SOCE contributes to melanoma progression, and therefore may be a new potential target for treatment of melanoma, irrespective of whether or not Braf mutation is present.

'Reduced malignancy as a mechanism for longevity in mice with adenylyl cyclase type 5 disruption'

Disruption of adenylyl cyclase type 5 (AC5) knockout (KO) is a novel model for longevity. Because malignancy is a major cause of death and reduced lifespan in mice, the goal of this investigation was to examine the role of AC5KO in protecting against cancer. There have been numerous discoveries in genetically engineered mice over the past several decades, but few have been translated to the bedside. One major reason is that it is difficult to alter a gene in patients, but rather a pharmacological approach is more appropriate. The current investigation employs a parallel construction to examine the extent to which inhibiting AC5, either in a genetic knockout (KO) or by a specific pharmacological inhibitor protects against cancer. This study is unique, not only because a combined genetic and pharmacological approach is rare, but also there are no prior studies on the extent to which AC5 affects cancer. We found that AC5KO delayed age-related tumor incidence significantly, as well as protecting against mammary tumor development in AC5KO × MMTV-HER-2 neu mice, and B16F10 melanoma tumor growth, which can explain why AC5KO is a model of longevity. In addition, a Food and Drug Administration approved antiviral agent, adenine 9-β-D-arabinofuranoside (Vidarabine or AraAde), which specifically inhibits AC5, reduces LP07 lung and B16F10 melanoma tumor growth in syngeneic mice. Thus, inhibition of AC5 is a previously unreported mechanism for prevention of cancers associated with aging and that can be targeted by an available pharmacologic inhibitor, with potential consequent extension of lifespan.

Abstract 1864: Role of store-operated Ca2+ entry in proliferation and cell cycle in melanoma

Background: Melanoma has a poor prognosis due to its rapid progression and a high metastatic ability. Ca2+ homeostasis plays a pivotal role in proliferation in cancer cells, but little is known about the role of Ca2+ in melanoma. Store-operated calcium entry (SOCE) is defined as Ca2+ entry from extracellular space triggered when Ca2+ store in the endoplasmic reticulum (ER) is depleted. SOCE is regulated by coordination between Orai (ORAI calcium release-activated calcium modulator) in the plasma membrane, and STIM1 (stromal interaction molecule 1) in the ER. We examined the role of Ca2+ in melanoma cells especially focusing on SOCE. Method: Intracellular Ca2+ level was measured by using Fluo4-AM, a Ca2+-sensing fluorescent dye. Cell proliferation was measured by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Cells were stained with propidium iodide and cell cycle was assessed using flow cytometer. Protein phosphorylation microarray was performed by using a commercially available kit (Cancer Signaling Phospho-Antibody Array). Results: SOCE, as demonstrated by enhancement of Ca2+ entry from extracellular space after Ca2+ depletion in the ER, was observed in SK-MEL-2, C8161, SK-MEL-24, UACC257 (human) and B16 (mouse) melanoma cell lines, suggesting that the existence of SOCE is universal among melanoma cells. SOCE was attenuated by Pyr3, a pyrazole compound which is known to inhibit SOCE, as well as by EGTA that chelates extracellular Ca2+. Pyr3 inhibits cellular proliferation in SK-MEL-2 cells (IC50: 5.1uM) and C8161 cells (IC50: 2.1uM). Cell cycle was analyzed in C8161 cells, and the cell number in the G2 phase was increased by both Pyr3 and EGTA, indicating that SOCE plays a role in the transition of G2/S phase. Protein microarray data showed that Pyr3 reduces phosphorylation of signal transducers and activators of transcription 5 (STAT5) by 93%, suggesting that the JAK/STAT pathway may be involved in SOCE-induced alteration of cell cycle. Conclusion: Our results showed that inhibition of SOCE suppresses proliferation in melanoma, thus it could be a new strategy for melanoma therapy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1864. doi:1538-7445.AM2012-1864

Prevention of heart failure in mice by an antiviral agent that inhibits type 5 cardiac adenylyl cyclase

Despite numerous discoveries from genetically engineered mice, relatively few have been translated to the bedside, mainly because it is difficult to translate from genes to drugs. This investigation examines an antiviral drug, which also has an action to selectively inhibit type 5 adenylyl cyclase (AC5), a pharmaceutical correlate of the AC5 knockout (KO) model, which exhibits longevity and stress resistance. Our objective was to examine the extent to which pretreatment with this drug, adenine 9-β-d-arabinofuranoside (Ara-A), favorably ameliorates the development of heart failure (HF). Ara-A exhibited selective inhibition for AC5 compared with the other major cardiac AC isoform, AC6, i.e., it reduced AC activity significantly in AC5 transgenic (Tg) mice, but not in AC5KO mice and had little effect in either wild-type or AC6Tg mice. Permanent coronary artery occlusion for 3 wk in C57Bl/6 mice increased mortality and induced HF in survivors, as reflected by reduced cardiac function, while increasing cardiac fibrosis. The AC5 inhibitor Ara-A significantly improved all of these end points and also ameliorated chronic isoproterenol-induced cardiomyopathy. As with the AC5KO mice, Ara-A increased mitogen/extracellular signal-regulated kinase (MEK)/extracellular signal-regulated kinase (ERK) phosphorylation. A MEK inhibitor abolished the beneficial effects of the AC5 inhibitor in the HF model, indicating the involvement of the downstream MEK-ERK pathway of AC5. Our data suggest that pharmacological AC5 inhibition may serve as a new therapeutic approach for HF.

Caloric restriction reduces growth of mammary tumors and metastases

We investigated the effects of caloric restriction (CR) on growth of tumors and metastases in the 4T1 mammary tumor model and found that CR, compared with normal diet, reduced the growth of mammary tumors and metastases and the total number of metastases that originated both spontaneously from the primary tumor and also experimentally from i.v. injection of the tumor cells. CR also decreased proliferation and angiogenesis and increased apoptosis in tumors. CR reduced levels of insulin, leptin, insulin-like growth factor 1, insulin-like growth factor binding protein 3 and increased adiponectin in tumors. We also demonstrated that tumors from CR mice possessed lower levels of transforming growth factor-β, lower intratumor deposition of collagen IV and reduced invasiveness due to a decrease in tumor secretion of active matrix metalloproteinase 9. Our results suggest that CR-induced metabolic and signaling changes affect the stroma and the tumor cells resulting in a microenvironment that prevents proliferation of breast tumors and their metastases.

Abstract 4553: Gβγ subunits inhibit Epac-induced melanoma cell migration

Background: Recently we reported that activation of Epac1, an Exchange protein activated by cAMP, increases melanoma cell migration via Ca 2+ release from the endoplasmic reticulum (ER). G-protein subunits (Gβγ) are known to act as an independent signaling molecule upon activation of G-protein coupled receptor. However, the role of Gβγ in Ca2+ signaling and migration in melanoma has not been well studied. Here we report that there is crosstalk of Ca2+ signaling between Gβγ and Epac1 in melanoma, which results in inhibition of Epac-induced cell migration.

Methods: Human metastatic melanoma cell lines, SK-Mel-2, SK-Mel-24, SK-Mel-187, c8161, WM1552C, and WM1361A, were used in this study. Intracellular Ca2+ level was measured with Fura-2AM and/or Fluo-4AM fluorescent dyes. Cell migration was examined with the Boyden chambers. Gβ1 and Gγ2 subunits were overexpressed with plasmid harboring each subunit. C-terminus of β adrenergic receptor kinase (βARK-CT), which inhibits Gβγ, was overexpressed with adenovirus.

Results: A Gβγ -activating peptide, mSIRK, increased cytosolic Ca2+, in all melanoma cell lines. mSIRK induced Ca2+ entry was inhibited by depletion of extracellular Ca2+, suggesting that Gβγ activates Ca2+ influx from extracellular space. When cells were pretreated with mSIRK, but not with mSIRK (L9A), a non-functional mSIRK analogue, 8-(4-Methoxyphenylthio)-2′-O-methyladenosine- 3′,5′-cyclic monophosphate (8-pMeOPT), an Epac-specific agonist, failed to increase cytosolic Ca2+. In addition, co-overexpression of β1 and βγ2, which is a major combination of Gβγ, also inhibited 8-pMeOPT-induced Ca2+ elevation. Inhibition of Gβγ with βARK-CT, an inhibiting-peptide for Gβγ, or guanosine 5′-O-(2-thiodiphosphate) (GDPβS), a GDP analogue that inactivates Gβγ, recovered 8-pMeOPT-induced Ca2+ elevation. These data suggested that Gβγ inhibits Epac-induced Ca2+ release. We then examined the effect of Gβγ on Epac-induced cell migration. Epac-induced cell migration was decreased by mSIRK. Gp(CH)2pp (Guanosine 5′, α-β-methylene triphosphate), a constitutively active GTP analogue, also inhibited Epac-induced cell migration. Further, co-overexpression of Gβ1 and Gγ2 subunits inhibited Epac1-induced cell migration. By contrast, when βARK-CT was overexpressed, mSIRK's inhibitory effect on cell migration was negated. These data suggested that Gβγ has an inhibitory effect on Epac-induced melanoma cell migration. Finally, W-5, an inhibitor for calmodulin, negated mSIRK's inhibitory effects on Epac-induced Ca2+ elevation, and cell migration, suggesting involvement of calmodulin in the crosstalk of Ca2+ signaling between Gβγ and Epac.

Conclusion: Gβγ evokes Ca2+ entry from extracellular space, which results in suppression of Epac-induced cytosolic Ca2+ elevation and cell migration in melanoma.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4553. doi:10.1158/1538-7445.AM2011-4553

Abstract 3664: Epac1 activates migration of melanoma and angiogenesis of endothelial cells via FGF-2 intercellular signaling

Background: Fibroblast growth factor (FGF-2) regulates migration and angiogenesis in cancer. The binding of FGF-2 to its receptor requires N-sulfated glucosamine in heparan sulfate (HS), suggesting that a molecule that increases N-sulfation of glucosamine could enhance FGF-2 signaling. Recently, we demonstrated that Epac1, an exchange protein activated by cAMP, increases expression of N-deacetylase/N-sulfotransferase-1 (NDST-1) that increases N-sulfation of glucosamine. It is plausible that melanoma cells with abundant expression of Epac1 produce N-sulfation-rich glucosamine, which results in enhancement of intercellular FGF-2 signaling in melanoma microenvironment. The purpose of this study was to examine whether Epac1-rich melanoma cells can increase migration of surrounding Epac1-poor melanoma cells and endothelial cells.

Methods: Immunohistochemistry was performed on human melanoma tissue microarrays to examine expressions of Epac1, NDST-1 and N-sulfated glucosamine. For in vitro studies, we used 2 human melanoma cell lines, WM1552C (radial growth phase melanoma) and C8161 (metastatic melanoma), and human umbilical vein endothelial cells (HUVEC). Since Epac1 expression was much lower in WM1552C than C8161 cells, WM1552C were used as Epac1-poor, and C8161 as Epac1-rich melanoma cells. We evaluated the migratory responses in WM1552C and HUVEC cells to conditioned medium (CM) from C8161 cells with or without Epac1 ablation (C8161/Epac1(−)) or overexpression (C8161/Epac1OE). Endothelial tube formation assay was performed in HUVEC with conditioned media.

Results: The expression of Epac1 positively correlated with that of NDST-1, and N-sulfated glucosamine in human melanoma tissue microarray. Migration of WM1552C and HUVEC cells was increased by CM from C8161 cells, which was significantly enhanced by CM from C8161/Epac1OE, but reduced by CM from C8161/Epac1(−). The CM-induced migration was inhibited by a neutralizing antibody against FGF-2 (nFGF-2 ab) or heparitinase, a HS-degrading enzyme, suggesting involvement of FGF-2 and HS in the CM-induced migration. Binding of FGF-2 to FGF receptors in HUVEC cells was increased by CM from C8161 cells, which was significantly enhanced by CM from C8161/Epac1OE but reduced by CM from C8161/Epac1(−). Similar to migration, the CM-induced FGF-2 binding was inhibited by nFGF-2 ab or heparitinase. Since the expression of FGF-2 in C8161 cells was not changed by ablation of Epac1 or Epac1 overexpression, these data suggested that C8161 cells increase migration of WM1552C and HUVEC cells via modification of HS. Finally, tube formation of HUVEC was increased by CM from C8161 cells, but it was inhibited by Epac1 ablation on these cells.

Conclusion: Epac1-rich melanoma cells increase migration of Epac1-poor melanoma cell, and endothelial cells via intercellular FGF-2-signaling, suggesting the role of Epac1 in melanoma progression.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3664. doi:10.1158/1538-7445.AM2011-3664

Abstract 5259: Role of Orai1 and STIM1 in store-operated Ca2+ entry and cell migration in melanoma

Background: Melanoma has poor prognosis due to its strong metastatic ability that is mainly controlled by cell migration. Store operated Ca2+ entry (SOCE), which is defined as Ca2+ entry from extracellular space triggered with depletion of Ca2+ store in the endoplasmic reticulum (ER), largely regulates Ca2+ homeostasis in non-excitable cells. However, little is known about the role of SOCE in melanoma. Here we report that expressions of SOCE modulators, i.e., ORAI calcium release-activated calcium modulator (Orai), which is the plasma membrane Ca2+ channel, and stromal interaction molecule (STIM), an activator of Orai in the ER, in cultured melanoma cells and human melanoma tissues. We also examined the effect of these modulators on SOCE and cell migration in melanoma cells

Method: Western blot analysis in SK-Mel-2 cells, and immunohistochemistry in human tissue microarray, were performed to examine expressions of Orai1 or STIM1. Intracellular Ca2+ was measured with fluo-4 AM, Ca2+-sensing fluorescent dye, in human metastatic melanoma cell lines (SK-MEL-2, SK-MEL-24 and C8161 cells), a mouse melanoma cell line (B16 cells), a human melanocyte cell line, (HEMA-LP), and a mouse melanocyte cell line (Melan-A). Cell migration was examined with the Boyden chambers. In order to ablate Orai1 or STIM1, shRNA for each protein was induced in SK-Mel-2 cells with lentiviral infection.

Results: Expressions of Orai1 and STIM1 were observed in melanoma cells by western blot, and in human melanoma tissues by immunohistochemistry. SOCE, as demonstrated by enhancement of Ca2+ enhancement after Ca2+ depletion with thapsigargin, was clearly observed in melanoma cell lines, but not in melanocytes, suggesting that SOCE is enhanced in melanoma cells compared to melanocytes. When Orai1 was ablated in SK-MEL-2 cells, the peak Ca2+ signal within SOCE was reduced by 75 % compared to control (2.78±0.44 (control shRNA) vs. 1.44±0.18 (Orai1 shRNA) F/F0 ratio normalized to baseline, p&lt;0.05, n=5). Similarly, ablation of STIM1 reduces the peak Ca2+ signal within SOCE by 37 % compared to control (2.78±0.44 (control shRNA) vs. 2.12±0.63 (STIM1 shRNA) F/F0 ratio normalized to baseline, F/F0, normalized to baseline, p&lt;0.05, n=10). These data suggest that Orai1 and STIM1 are involved in SOCE in melanoma cells. We next examined the role of Orai1 and STIM1 in melanoma cell migration. Ablation of Orai1 reduced cell migration by 46 % (48±4.6 (control shRNA) vs. 26±3.2 (Orai1 shRNA) cells/field, p&lt;0.05, n=4). Similarly, ablation of STIM1 decreased cell migration by 40 % (48±4.6 (control shRNA) vs. 29±4.8 (STIM1 shRNA) cells/field, p&lt;0.05, n=4). These data suggest that Orai1 and/or STIM1 are involved in basal cell migration in melanoma.

Conclusion: SOCE, which is regulated by Orai1 and STIM1 in melanoma cells, plays a major role in Ca2+ homeostasis, and cell migration in melanoma, and thus potentially metastasis.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5259. doi:10.1158/1538-7445.AM2011-5259

Exchange protein directly activated by cyclic AMP increases melanoma cell migration by a Ca2+-dependent mechanism

Melanoma has a poor prognosis due to its strong metastatic ability. Although Ca(2+) plays a major role in cell migration, little is known about the role of Ca(2+) in melanoma cell migration. We recently found that the exchange protein directly activated by cyclic AMP (Epac) increases melanoma cell migration via a heparan sulfate-related mechanism. In addition to this mechanism, we also found that Epac regulates melanoma cell migration by a Ca(2+)-dependent mechanism. An Epac agonist increased Ca(2+) in several different melanoma cell lines but not in melanocytes. Ablation of Epac1 with short hairpin RNA inhibited the Epac agonist-induced Ca(2+) elevation, suggesting the critical role of Epac1 in Ca(2+) homeostasis in melanoma cells. Epac-induced Ca(2+) elevation was negated by the inhibition of phospholipase C (PLC) and inositol triphosphate (IP(3)) receptor. Furthermore, Epac-induced cell migration was reduced by the inhibition of PLC or IP(3) receptor. These data suggest that Epac activates Ca(2+) release from the endoplasmic reticulum via the PLC/IP(3) receptor pathway, and this Ca(2+) elevation is involved in Epac-induced cell migration. Actin assembly was increased by Epac-induced Ca(2+), suggesting the involvement of actin in Epac-induced cell migration. In human melanoma specimens, mRNA expression of Epac1 was higher in metastatic melanoma than in primary melanoma, suggesting a role for Epac1 in melanoma metastasis. In conclusion, our findings reveal that Epac is a potential target for the suppression of melanoma cell migration, and, thus, the development of metastasis.

Abstract 5280: Exchange protein activated by cAMP (Epac) accelerates melanoma cell migration through Ca 2+-dependent actin assembly

Background: We previously reported that Epac, a guanine nucleotide exchange factor directly activated by cAMP, increases melanoma cell migration through Ca2+ elevation. Both Epac-induced cell migration and Ca2+ elevation were reduced by pharmacological inhibition of phospholipase C (PLC) and inositol triphosphate (IP3) receptor. Accordingly, we studied the involvement of PLC/IP3 receptor in Epac-induced Ca2+ elevation by knockdown of these molecules. However, the mechanism how Epac-induced Ca2+ elevation mediates melanoma cell migration is unknown. Here, we investigate the effect of Epac induced-Ca2+ elevation on actin assembly, which plays a major role in cell migration.

Methods: SK-Mel-2, a cell line from human metastatic melanoma, was used in this study. Intracellular Ca2+ was measured with Fura-2AM fluorescent dye. Cell migration was examined with the Boyden chambers. IP3 production was examined by IP3 radioimmunoassay. Actin assembly was examined by immunocytochemistry. In some experiments, ablation of a target protein with lentivirus-based shRNA induction system was performed.

Results: 8-pMeOPT-2′-O-Me-cAMP (8-pMeOPT), an Epac-specific agonist, increased Ca2+ and cell migration in SK-Mel-2. Such Ca2+ elevation and cell migration was negated by ablation of PLCε or IP3 receptor 1. In addition, Epac-induced IP3 production was inhibited by U73122, a PLC inhibitor, and ablation of PLCε. These data suggest that Epac increases Ca2+, and thus cell migration, via the PLCε/IP3 receptor 1 signaling pathway. Cytochalasin D, an actin assembly inhibitor, reduced 8-pMeOPT-induced cell migration. In addition, immunocytochemistry showed that 8-pMeOPT increases actin assembly. When U73122 or Xestopongin C, an IP3 receptor inhibitor, was used, Epac-induced actin assembly was decreased. These data suggest that Epac-induced Ca2+ elevation mediates actin assembly. Further, immunoprecipitation showed that 8-pMeOPT increased physical interaction of myosin heavy chain IIA (MHCIIA), which enhances actin assembly, with S100A4, a Ca2+-binding protein which activates MHCIIA. These data suggest that Epac-induced Ca2+ elevation mediates actin assembly via the S100A4/MHCIIA signaling pathway.

Conclusion: Epac increases Ca2+ via the PLCε/IP3 receptor 1 pathway. Also, Epac-induced Ca2+ elevation mediates melanoma cell migration via actin assembly. These data suggested that Epac could be a target for treating patients with melanoma.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5280.

Epac increases melanoma cell migration by a heparan sulfate-related mechanism

Melanoma, the most malignant form of human skin cancer, has a poor prognosis due to its strong metastatic ability. It was recently demonstrated that Epac, an effector molecule of cAMP, is involved in regulating cell migration; however, the role of Epac in melanoma cell migration remains unclear. We thus examined whether Epac regulates cell migration and metastasis of melanoma. Epac activation, by either specific agonist or overexpression of Epac, increased melanoma cell migration. Deletion of endogenous Epac with small interfering RNA decreased basal melanoma cell migration. These data suggested a major role of Epac in melanoma cell migration. Epac-induced cell migration was mediated by translocation of syndecan-2, a cell-surface heparan sulfate proteoglycan, to lipid rafts. This syndecan-2 translocation was regulated by tubulin polymerization via the Epac/phosphoinositol-3 kinase pathway. Epac-induced cell migration was also regulated by the production of heparan sulfate, a major extracellular matrix. Epac-induced heparan sulfate production was attributable to the increased expression of N-deacetylase/N-sulfotransferase-1 (NDST-1) accompanied by an increased NDST-1 translation rate. Finally, Epac overexpression enhanced lung colonization of melanoma cells in mice. Taken together, these data indicate that Epac regulates melanoma cell migration/metastasis mostly via syndecan-2 translocation and heparan sulfate production.

Developmental changes in gene expression of Epac and its upregulation in myocardial hypertrophy

Although it has been shown that Epac1 mRNA is expressed ubiquitously and Epac2 mRNA predominantly in the brain and endocrine tissues, developmental and pathophysiological changes of these molecules have not been characterized. Developmental changes were analyzed in murine heart, brain, kidneys, and lungs by RT-PCR analysis, which revealed more drastic developmental changes of Epac2 mRNA than Epac1. Only the Epac2 mRNA in kidney showed a transient expression pattern with dramatic decline into adulthood. In addition to developmental changes, we found that Epac gene expression was upregulated in myocardial hypertrophy induced by chronic isoproterenol infusion or pressure overload by transverse aortic banding. Both Epac1 and Epac2 mRNA were upregulated in isoproterenol-induced left ventricular hypertrophy, whereas only Epac1 was increased in pressure overload-induced hypertrophy. Stimulation of H9c2, cardiac myoblast cells, with fetal calf serum, which can induce myocyte hypertrophy, upregulated Epac1 protein expression. We also demonstrated that Epac was the limiting moiety, relative to Rap, in the Epac-Rap signaling pathway in terms of stoichiometry and that Epac stimulation led to the activation of ERK1/2. Our data suggest the functional involvement of Epac in organogenesis and also in physiological as well as pathophysiological processes, such as cardiac hypertrophy. Furthermore, our results suggest the importance of the stoichiometry of Epac over that of Rap in cellular biological effects.