rAAV9-Mediated MEK1 Gene Expression Restores Post-conditioning Protection Against Ischemia Injury in Hypertrophic Myocardium.

PURPOSE: We investigated whether increased expression of activated mitogen-activated protein kinase (MAPK) kinases 1 (MEK1) restores ischemic post-conditioning (IPostC) protection in hypertrophic myocardium following ischemia/reperfusion (I/R) injury. METHODS: C57Bl/6 mice received recombinant adeno-associated virus type 9 (rAAV9)-mediated activated MEK1 gene delivery systemically, then following the induction of cardiac hypertrophy via transverse aortic constriction for 4 weeks. In a Langendorff model, hypertrophic hearts were subjected to 40 min/60 min I/R or with IPostC intervention consisting of 6 cycles of 10 s reperfusion and 10 s no-flow before a 60-min reperfusion. Hemodynamics, infarct size (IS), myocyte apoptosis and changes in expression of reperfusion injury salvage kinase (RISK) pathway were examined. RESULTS: rAAV9-MEK1 gene delivery led to a 4.3-fold and 2.7-fold increase in MEK1 mRNA and protein expression in the heart versus their control values. I/R resulted in a larger IS in hypertrophic than in non-hypertrophic hearts (52.3 ± 4.7% vs. 40.0 ± 2.5%, P < 0.05). IPostC mediated IS reduction in non-hypertrophic hearts (27.6 ± 2.6%, P < 0.05), while it had no significant effect in hypertrophic hearts (46.5 ± 3.1%, P=NS) compared with the IS in non-hypertrophic or hypertrophic hearts subjected to I/R injury only, respectively. Hemodynamic decline induced by I/R was preserved by IPostC in non-hypertrophic hearts but not in hypertrophic hearts. rAAV9-MEK1 gene delivery restored IPostC protection in hypertrophic hearts evidenced by reduced IS (32.0 ± 2.8% vs. 46.5 ± 3.1%) and cardiac cell apoptosis and largely preserved hemodynamic parameters. These protective effects were associated with significantly increased phosphorylation of ERK1/2 and ribosomal protein S6 kinases (p70S6K), but it had no influence on Akt and glycogen synthase kinase-3ß. CONCLUSION: These results demonstrated that rAAV9-mediated activated MEK1 expression restores IPostC protection in the hypertrophic heart against I/R injury through the activation of ERK pathway.

Short-term culture of tumour slices reveals the heterogeneous sensitivity of human head and neck squamous cell carcinoma to targeted therapies.

BACKGROUND: Despite recent progress, investigating the impact of targeted therapies on Head and Neck Squamous Cell Carcinoma (HNSCC) remains a challenge. We investigated whether short-term culture of tumour fragments would permit the evaluation of tumour sensitivity to targeted therapies at the individual level. METHODS: We cultivated tumour slices prepared from 18 HNSCC tumour samples obtained during surgical resection. The samples were treated for 48 h with a panel of 8 targeted therapies directed against selected oncogenic transduction pathways. We analysed the cell proliferation index (CPI) of tumour cells using Ki67 labelling and the activation status of the RAF-MEK-ERK cascade through ERK phosphorylation analysis. RESULTS: Fourteen tumours were successfully analysed after short-term culture of tumour samples, revealing a striking individual heterogeneity of HNSCC in terms of tumour cell sensitivity to targeted therapies. Using 50% inhibition of CPI as threshold, sorafenib was shown to be active in 5/14 tumours. Cetuximab, the only approved targeted drug against HNSCC, was active in only 2/14 tumours. A more than 50% inhibition was observed with at least one drug out of the eight tested in 10/14 tumours. Cluster analysis was carried out in order to examine the effect of the drugs on cell proliferation and the RAF-MEK-ERK cascade. CONCLUSIONS: In vitro culture of tumour fragments allows for the evaluation of the effects of targeted therapies on freshly resected human tumours, and might be of value as a possible guide for the design of clinical trials and for the personalization of the medical treatment of HNSCC.

Sorafenib/regorafenib and lapatinib interact to kill CNS tumor cells.

The present studies were to determine whether the multi-kinase inhibitor sorafenib or its derivative regorafenib interacted with the ERBB1/ERBB2 inhibitor lapatinib to kill CNS tumor cells. In multiple CNS tumor cell types sorafenib and lapatinib interacted in a greater than additive fashion to cause tumor cell death. Tumor cells lacking PTEN, and anoikis or lapatinib resistant cells were as sensitive to the drug combination as cells expressing PTEN or parental cells, respectively. Similar data were obtained using regorafenib. Treatment of brain cancer cells with [sorafenib + lapatinib] enhanced radiation toxicity. The drug combination increased the numbers of LC3-GFP vesicles; this correlated with a reduction in endogenous LC3II, and p62 and LAMP2 degradation. Knock down of Beclin1 or ATG5 significantly suppressed drug combination lethality. Expression of c-FLIP-s, BCL-XL, or dominant negative caspase 9 reduced drug combination toxicity; knock down of FADD or CD95 was protective. Expression of both activated AKT and activated MEK1 or activated mTOR was required to strongly suppress drug combination lethality. As both lapatinib and sorafenib are FDA approved agents, our data argue for further determination as to whether lapatinib and sorafenib is a useful glioblastoma therapy.

MEK1/2 overactivation can promote growth arrest by mediating ERK1/2-dependent phosphorylation of p70S6K.

The extracellular signal-regulated kinase (ERK)1/2 mitogen-activated protein (MAP) kinase pathway has been involved in the positive and negative regulation of cell proliferation. Upon mitogen stimulation, ERK1/ERK2 activation is necessary for G1- to S-phase progression whereas when hyperactived, this pathway could elicit cell cycle arrest. The mechanisms involved are not fully elucidated but a kinase-independent function of ERK1/2 has been evidenced in the MAPK-induced growth arrest. Here, we show that p70S6K, a central regulator of protein biosynthesis, is essential for the cell cycle arrest induced by overactivation of ERK1/2. Indeed, whereas MEK1 silencing inhibits cell cycle progression, we demonstrate that active mutant form of MEK1 or MEK2 triggers a G1 phase arrest by stimulating an activation of p70S6K by ERK1/2 kinases. Silencing of ERK1/2 activity by shRNA efficiently suppresses p70S6K phosphorylation on Thr421/Ser424 and S6 phosphorylation on Ser240/244 as well as p21 expression, but these effects can be partially reversed by the expression of kinase-dead mutant form of ERK1 or ERK2. In addition, we demonstrate that the kinase p70S6K modulates neither the p21 gene transcription nor the stability of the protein but enhances the translation of the p21 mRNA. In conclusion, our data emphasizes the importance of the translational regulation of p21 by the MEK1/2-ERK1/2-p70S6K pathway to negatively control the cell cycle progression.

Effects of egg yolk-derived peptide on osteogenic gene expression and MAPK activation.

The present study investigated the effects of egg yolk-derived peptide (YPEP) on osteogenic activities and MAPK-regulation of osteogenic gene expressions. The effects of YPEP on cell proliferation, alkaline phosphatase activity, collagen synthesis, and mineralization were measured in human osteoblastic MG-63 cells. Activation of MAPKs and downstream transcription factors such as extracellular-signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase 1/2 (JNK1/2), p38, ELK1, and cJUN were examined using western blot analysis. YPEP dose-dependently increased MG-63 cell proliferation, ALP activity, collagen synthesis, and calcium deposition. YPEP activated ERK1/2, p38, and ELK1 phosphorylation whereas JNK and cJUN were not affected by YPEP. The COL1A1 (collagen, type I, alpha 1), ALPL (alkaline phosphatase), and SPP1 (secreted phosphoprotein 1, osteopontin) gene expressions were increased while BGLAP (osteocalcin) was not affected by YPEP. The ERK1/2 inhibitor (PD98509) blocked the YPEP-induced COL1A1 and ALPL gene expressions as well as ELK1 phosphorylation. The p38 inhibitor (SB203580) blocked YPEP-induced COL1A1 and ALPL gene expressions. SPP1 gene expression was not affected by these MAPK inhibitors. In conclusion, YPEP treatment stimulates the osteogenic differentiation via the MAPK/ELK1 signaling pathway. These results could provide a mechanistic explanation for the bone-strengthening effects of YPEP.

MicroRNA-1826 directly targets beta-catenin (CTNNB1) and MEK1 (MAP2K1) in VHL-inactivated renal cancer.

The aim of this project is to identify new therapeutic microRNAs (miRNAs) for von Hippel-Lindau (VHL)-inactivated renal cancer cells. We initially identified several potential miRNAs targeting CTNNB1 and MEK1 using several targets scan algorithms. Only miR-1826 was found to target CTNNB1 and MEK1. Therefore, we focused on miRNA-1826 and performed 3' untranslated region (UTR) luciferase assay, functional analyses and association study between miR-1826 expression and renal cancer patient outcomes. miR-1826 expression was significantly lower in renal cancer tissues compared with non-neoplastic areas and lower expression was significantly associated with overall shorter survival and earlier recurrence after radical nephrectomy. Following miR-1826 transfection, 3' UTR luciferase activity and protein expression of beta-catenin and MEK1 were significantly downregulated in renal cancer cells. Introduction of miR-1826 also inhibited renal cancer cell proliferation, invasion and migration. Additionally, miR-1826 promoted apoptosis and G(1) arrest in VHL-inactivated renal cancer cells. Knockdowns of CTNNB1 and MEK1 by small interfering RNAs reproduced the tumor-suppressive effect of miR-1826. Our data suggest that the miR-1826 plays an important role as a tumor suppressor by downregulating beta-catenin and MEK1 in VHL-inactivated renal cancers.

IL-2 and IL-4 stimulate MEK1 expression and contribute to T cell resistance against suppression by TGF-beta and IL-10 in asthma.

The T cell-driven airway inflammation in chronic asthma is uninhibited and sustained. We examined the resistance of T cells from asthmatic patients against suppression by TGF-ß, IL-10 and glucocorticoids and explored its signaling mechanism. CD4(+)CD25(-) T cells from allergic asthmatic subjects demonstrated increased TCR-stimulated proliferation as compared with healthy and chronic obstructive pulmonary disease controls. This proliferation was resistant to inhibition by TGF-ß, IL-10, and dexamethasone and to anergy induction. CD4 T cells from asthmatic patients, but not chronic obstructive pulmonary disease, allergic rhinitis, and healthy subjects, showed increased expression of MEK1, heightened phosphorylation of ERK1/2, and increased levels of c-Fos. IL-2 and IL-4 stimulated the expression of MEK1 and c-Fos and induced T cell resistance. The inhibition of MEK1 reversed, whereas induced expression of c-Fos and JunB promoted T cell resistance against TGF-ß- and IL-10-mediated suppression. We have uncovered an IL-2- and IL-4-driven MEK1 induction mechanism that results in heightened ERK1/2 activation in asthmatic T cells and make them resistant to certain inhibitory mechanisms.

Oligonol, an oligomerized lychee fruit-derived polyphenol, activates the Ras/Raf-1/MEK1/2 cascade independent of the IL-6 signaling pathway in rat primary adipocytes.

Oligonol is a lychee fruit-derived low-molecular form of polyphenol. In this study, the effect of Oligonol on the mitogen activated-protein kinase (MAPK) signaling pathway in primary adipocytes was investigated to examine the mechanism underlying the enhanced levels of phosphorylated extracellular-signaling regulatory kinase1/2 (ERK1/2) that accompany an in vitro increase in lipolysis. Oligonol significantly elevated the levels of activated Ras and the phosphorylation of Raf-1 and MAPK/ERK kinase1/2 (MEK1/2) with no increase in pan-Raf-1 and -MEK1/2 proteins. The increase in phosphorylation of Raf-1 and MEK1/2 with Oligonol was inhibited completely by pretreatment with GW5074, a selective Raf-1 inhibitor, or PD98059, a selective MEK1/2 inhibitor. IL-6 also activated the MAPK signaling pathway in adipocytes through the association with its receptor. IL-6-induced phosphorylation of Raf-1 and MEK1/2 was significantly inhibited by pretreatment with the IL-6 receptor antibody. Under such a condition, however, the levels of phosphorylated Raf-1 and MEK1/2 with Oligonol still remained significantly higher, and there was a significant decrease in secretion of IL-6 from adipocytes, compared with untreated control cells. These results suggest that Oligonol activates the Ras/Raf-1/MEK1/2 signaling pathway, independent of the IL-6 signaling pathway, leading to activation of ERK1/2 proteins in primary adipocytes.

miRNA-183∼96∼182 regulates melanogenesis, cell proliferation and migration in B16 cells.

Melanoma is a highly invasive malignant skin tumor having high metastatic rate and poor prognosis. The biology of melanoma is controled by miRNAs. The miRNA-183 cluster, which is composed of miRNA-183∼96∼182 genes, plays an important roles in tumor development. In order to investigate the role and action of miRNA-183 cluster in B16 cells, we overexpressed and knocked down miRNA-183 cluster in B16 cells. Using bioinformatics analysis, we predicted that the key framscript factor of melangenic genes. Microphthalmia-associated transcription factor (MITF) is one of the targets of miRNA-183 cluster. The results of Luciferase activity assays confirmed that MITF was targeted by miRNA-183 cluster. Overexpression and knockdown of miRNA-183 cluster in B16 cells resulted in down and up regulation of MITF expression, respectively at both mRNA and protein levels. Furthmore, overexpression and knockdown of the miRNA-183 cluster in B16 cells decreased and increased the expression of mRNA and protein of melangenic genes tyrosinase (TYR), and tyrosinase-related protein 1 (TYRP1), dopachrome-tautomerase (DCT), as well as the production of melanins and eumelanin production, respectively. On the proliferation and migration pathway, overexpression and knockdown of miRNA-183 cluster increased and decreased, respectively the expression of mRNA and protein of mitogen-activated protein kinase 1 (MEK1), extracellular regulated protein kinases1/2 (ERK1/2) and cAMP-responsive-element binding protein (CREB). These results indicated that miRNA-183 cluster regulated melanogenesis in B16 cells as well as cell proliferation and migration by directly targeting MITF through migration pathway.

Raf-independent, PP2A-dependent MEK activation in response to ERK silencing.

Biological roles of ERK and MEK in signal transduction have been controversial. The aim of the current study was to determine the role of ERK1/2 in signaling through the ERK-MAPK cascade by using RNAi methodology. Transient transfection of erk1 or erk2 siRNA decreased the respective protein level to 3-8% in human lung fibroblasts. Interestingly, individual ERK isoform silencing resulted in a 2-fold reciprocal increase in phosphorylation of the alternate ERK isoform, with no change in respective total protein expression. Moreover, MEK was hyperphosphorylated as a result of combined ERK1 and ERK2 silencing, but was unaffected in individual ERK1 or ERK2 silenced cells. This hyperactivation of MEK was not due to activation of Raf family members, but rather was associated with PP2A downregulation. These data highlight the existence of a feedback loop in normal cells whereby ERK silencing is associated with decreased PP2A activity and consequent MEK activation.

Aberrant extracellular signal-regulated kinase (ERK)1/2 signalling in suicide brain: role of ERK kinase 1 (MEK1).

Extracellular signal-regulated kinase (ERK)1/2 signalling plays a critical role in synaptic and structural plasticity. Recent preclinical and human brain studies suggest that depression and suicidal behaviour are associated with aberrant ERK1/2 signalling. MEK, is a dual-specificity kinase, which is the immediate upstream regulator of ERK1/2. Two isoforms of MEK (MEK1 and MEK2) exist. By phosphorylating at Ser and Thr residues, MEK activates ERK1/2, which then phosphorylates cytoplasmic and nuclear substrates. On the other hand, MEK itself is regulated through phosphorylation by upstream Raf kinases. Recently, we demonstrated that activation of ERK1/2 and B-Raf was attenuated in the brains of suicide subjects. To further investigate the regulation of ERK1/2 signalling, we examined the expression and activation of MEKs, the interaction of MEK with ERKs, MEK-mediated activation of ERK1/2, and ERK1/2-mediated activation of nuclear substrate Elk-1 in the prefrontal cortex and hippocampus of suicide subjects. In addition, in order to investigate whether MEK is regulated by B-Raf, we examined the B-Raf and MEK interaction. No significant changes were observed in expression levels of MEK1 or MEK2; however, the catalytic activity of only MEK1 (not MEK2) was decreased in both the prefrontal cortex and hippocampus of suicide subjects. The interaction of MEK1 with ERK1 and ERK2 was increased along with decreased phosphorylation and catalytic activity of ERK1/2. In addition, we found decreased phosphorylation of MEK1 and less interaction of B-Raf with MEK1. Our results demonstrate abnormalities in MEK1 at multiple levels and suggest that these abnormalities in MEK1 are crucial for aberrant ERK1/2 signalling in suicide brain.

Involvement of Rad51 in cytotoxicity induced by epidermal growth factor receptor inhibitor (gefitinib, IressaR) and chemotherapeutic agents in human lung cancer cells.

Gefitinib (Iressa(R), ZD1839) is a selective epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor that blocks growth factor-mediated cell proliferation and extracellular signal-regulated kinases 1/2 (ERK1/2) signaling activation. Rad51 is an essential component of the homologous recombination repair pathway. High level of Rad51 expression has been reported in chemo- or radioresistant carcinomas. We hypothesized that gefitinib may enhance the effects of the alkylating agent cisplatin- or the antitumor antibiotic mitomycin C (MMC)-mediated cytotoxicity by decreasing ERK1/2 activation and Rad51 expression. Exposure of human non-small lung cancer cells to gefitinib decreased cisplatin- or MMC-elicited ERK1/2 activation and Rad51 protein induction. Neither cisplatin nor MMC treatment affected Rad51 messenger RNA (mRNA). However, gefitinib cotreatment with cisplatin or MMC significantly decreased Rad51 mRNA levels. In addition, gefitinib decreased cisplatin- or MMC-elicited Rad51 protein levels by increasing Rad51 protein instability. Enhancement of ERK1/2 signaling by constitutively active mitogen-activated protein kinase kinase 1/2 (MKK1/2-CA) increased Rad51 protein levels and protein stability in gefitinib and cisplatin or MMC cotreated cells. Moreover, the synergistic cytotoxic effects induced by gefitinib cotreatment with cisplatin or MMC were remarkably decreased by MKK1-CA-mediated enhancement of ERK1/2 activation. Depletion of endogenous Rad51 expression by si-Rad51 RNA transfection significantly enhanced lung cancer cell death upon treatment with cisplatin or MMC. We conclude that Rad51 protein protects lung cancer cells from synergistic cytotoxic effects induced by gefitinib and chemotherapeutic agents. Suppression of Rad51 expression may be a novel lung cancer therapeutic modality to overcome drug resistance to EGFR inhibitors and chemotherapeutic agents.

Changes in the transcriptional profile of cardiac myocytes following green fluorescent protein expression.

Green fluorescent protein (GFP) and its multiple forms, such as enhanced GFP (EGFP), have been widely used as marker proteins and for tracking purposes in many biological systems, including the heart and cardiac cell systems. Despite some concerns on its toxicity under certain circumstances, GFP remains amongst the most reliable and easy-to-use markers available. Using rat full genome DNA microarrays, we have investigated the broader consequences of adenoviral-driven GFP expression in cardiac myocytes. In our transcriptional profiling analysis, we set a threshold of a twofold change. We removed possible changes resulting from adenoviral infection by comparison with transcriptional profiles of cardiac myocytes with adenoviral-driven expression of an unrelated protein, the kinase MEK. Our analysis revealed changes in the expression of 212 genes. Of these genes, 174 were upregulated and 38 were downregulated following GFP expression. Many of these genes remain unannotated, but an evaluation of those with described functions for their resulting proteins indicated that many were involved in processes, including responses to stimuli/stress and signal transduction. Our analysis thus indicates the broader consequences of GFP expression in altering gene expression profiles in cardiac cells. Care should therefore be taken when using GFP expression as a control in gene expression studies.

Induction of ornithine decarboxylase activity is a necessary step for mitogen-activated protein kinase kinase-induced skin tumorigenesis.

A transgenic mouse line overexpressing a constitutively active mutant of MEK1, a downstream effector of Ras, driven by the keratin 14 (K14) promoter, has been used to test the hypothesis that ornithine decarboxylase (ODC) induction during tumor promotion following a single initiating event [i.e., the activation of the Raf/mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (Raf/MEK/ERK) pathway], is a necessary step in skin carcinogenesis. K14-MEK mice exhibit moderate hyperplasia, with spontaneous skin tumor development within 5 weeks of birth. Analysis of epidermis and dermis showed induction of MEK protein and ERK1/ERK2 phosphorylation, but no change in Akt-1, suggesting that the PI 3-kinase pathway, another pathway downstream of ras, is not activated. Examination of tumors revealed high levels of ODC protein and activity, indicating that activation of signaling cascades dependent on MEK activity is a sufficient stimulus for ODC induction. When K14-MEK mice were given alpha-difluoromethylornithine (DFMO), a suicide inactivator of ODC, in the drinking water from birth, there was a dramatic delay in the onset of tumor growth ( approximately 6 weeks), and only 25% of DFMO-treated mice developed tumors by 15 weeks of age. All untreated K14-MEK mice developed tumors by 6 weeks of age. Treatment of tumor-bearing mice with DFMO reduced both tumor size and tumor number within several weeks. Tumor regression was the result of both inhibition of proliferation and increased apoptosis in tumors. The results establish ODC activation as an important component of the Raf/MEK/ERK pathway, and identify K14-MEK mice as a valuable model with which to study the regulation of ODC in ras carcinogenesis.

Gene expression changes and signaling events associated with the direct antimelanoma effect of IFN-gamma.

IFN-gamma plays a role in the response to melanoma indirectly through its effect on the immune system and directly through its antiproliferative and proapoptotic effects on melanoma cells. To understand the molecular basis for the direct antimelanoma effect of IFN-gamma, we studied IFN-induced changes in gene expression and signaling among three human melanoma cell lines (DM6, DM93, and 501mel). These were resistant to the antimelanoma effect of IFN-alpha, and only DM6 cells exhibited growth inhibition and apoptosis with IFN-gamma. Through DNA microarray analysis, we found that the antimelanoma effect of IFN-gamma in DM6 was associated with the down-regulation of multiple genes involved in G-protein signaling and phospholipase C activation (including Rap2B and calpain 3) as well as the down-regulation of genes involved in melanocyte/melanoma survival (MITF and SLUG), apoptosis inhibition (Bcl2A1 and galectin-3), and cell cycling (CDK2). The antimelanoma effect of IFN-gamma was also associated with the up-regulation of the proapoptotic dependence receptor UNC5H2 and the Wnt inhibitor Dkk-1. Whereas both IFNs were able to activate Stat1 in all cell lines, the delayed activation of the extracellular signal-regulated kinase, p38, and c-Jun NH2-terminal kinase mitogen-activated protein kinases occurred only in DM6 with IFN-gamma, and the effect of IFN-gamma on cell growth and survival as well as gene expression in DM6 was dependent on the coordinate activation of MEK1 and p38. These findings provide new insights into the signaling events and gene expression changes associated with growth inhibition and apoptosis in melanoma and may thereby assist in identifying new targets for the treatment of melanoma.

A Screen for Key Genes and Pathways Involved in High-Quality Brush Hair in the Yangtze River Delta White Goat.

The Yangtze River Delta White Goat is the only goat breed that produces high-quality brush hair, or type III hair, which is specialized for use in top-grade writing brushes. There has been little research, especially molecular research, on the traits that result in high-quality brush hair in the Yangtze River Delta White Goat. To explore the molecular mechanisms of the formation of high-quality brush hair, High-throughput RNA-Seq technology was used to compare skin samples from Yangtze River Delta White Goats that produce high-quality hair and non high-quality hair for identification of the important genes and related pathways that might influence the hair quality traits. The results showed that 295 genes were expressed differentially between the goats with higher and lower hair quality, respectively. Of those genes, 132 were up-regulated, 62 were down-regulated, and 101 were expressed exclusively in the goats with high-quality brush hair. Gene Ontology and Metabolic Pathway Significant Enrichment analyses of the differentially expressed genes indicated that the MAP3K1, DUSP1, DUSP6 and the MAPK signaling pathway might play important roles in the traits important for high-quality brush hair.

p90RSK Blockade Inhibits Dual BRAF and MEK Inhibitor-Resistant Melanoma by Targeting Protein Synthesis.

Despite improvements in survival in metastatic melanoma with combined BRAF and mitogen-activated protein kinase/extracellular signal-regulated kinase inhibitor treatment, the overwhelming majority of patients eventually acquire resistance to both agents. Consequently, new targets for therapy in resistant tumors are currently being evaluated. Previous studies have identified p90 subfamily of ribosomal S6 kinase (p90RSK) family kinases as key factors for growth and proliferation, as well as protein synthesis via assembly of the 7-methyl-guanosine triphosphate cap-dependent translation complex. We sought to evaluate inhibitors of p90RSK family members: BI-D1870 and BRD7389, for their ability to inhibit both proliferation and protein synthesis in patient-derived melanoma cell lines with acquired resistance to combined treatment with the BRAF inhibitor vemurafenib and the mitogen-activated protein kinase/extracellular signal-regulated kinase inhibitor selumetinib. We found that the RSK inhibitors blocked cell proliferation and protein synthesis in multiple dual-resistant melanoma lines. In addition, single agent RSK inhibitor treatment was effective in drug-naïve lines, two of which are innately vemurafenib resistant. We also used Reverse Phase Protein Array screening to identify differential protein expression that correlates with BI-D1870 sensitivity, and identified prognostic biomarkers for survival in human melanoma patients. These findings establish p90RSK inhibition as a therapeutic strategy in treatment-resistant melanoma and provide insight into the mechanism of action.

EGF receptor-related protein (ERRP) inhibits invasion of colon cancer cells and tubule formation by endothelial cells in vitro.

Activation of the epidermal growth factor receptor (EGFR) and/or its family member(s) stimulates many processes of carcinogenesis, including cell invasion and the formation of new blood vessels, events that are critically involved in angiogenesis. Interference with the activation of EGFRs, therefore, represents a promising strategy for the development of novel and selective anticancer therapies. Previously, we reported that EGFR-related protein (ERRP), which we have isolated and characterized as a pan-erbB inhibitor, is a potential therapeutic agent for colorectal and other epithelial cancers. The present investigation was undertaken to determine whether ERRP would affect the invasion of colon cancer cells and formation of tubules, and the regulation of these processes. ERRP inhibited tubule formation by aortic endothelial cells and invasion of HCT-116 colon cancer cells through matrigel. These changes were associated with marked reductions in the synthesis and secretion of bFGF, VEGF and TGF-alpha by HCT-116 cells. Secretion of bFGF and VEGF by aortic endothelial cells was also inhibited by ERRP. Microarray analysis of ERRP-treated HCT-116 cells showed reduced levels of several growth regulatory proteins such as p21Rac1, Stratifin (14-3-3 Sigma), focal adhesion kinase (FAK) and mediators of the Ras-Raf-ERK pathway. ERRP treatments resulted in reduced expression of p21Rac1 and inhibited the constitutive activation of FAK and MEK2 in HCT-116 cells. Transfection of constitutively activate p21Rac1 or MEK2 into HCT-116 cells abrogated ERRP-induced inhibition of growth. In summary, it was demonstrated that ERRP not only inhibits cell growth, but also the processes of cell invasion and blood vessel formation that are critical for the development and progression of carcinogenesis.

Identification of intracellular pathways through which TGF-ß1 upregulates URG-4/URGCP gene expression in hepatoma cells.

AIMS: Up-regulated gene 4 (URG-4/URGCP) was strongly expressed in Hepatitis B infected liver and correlated with HBxAG (Hepatitis B x Antigen) protein and found to promote hepatocellular cancer. Transforming growth factor (TGF-ß1) is a multifunctional protein that effects cell proliferation, growth inhibition, differentiation and other functions. However, the mechanism of URG-4/URGCP regulation by TGF-ß1 and its significance in cancer progression remains largely unknown. MAIN METHODS: The effect of TGF-ß1 on URG-4/URGCP gene was determined using REAL TIME PCR at mRNA level and Western blotting/immunofluorescence at protein level. Transient transfection assays were carried out to find out which site of promoter is upregulated by TGF-ß1. KEY FINDINGS: We report the upregulation of URG-4/URGCP gene expression by TGF-ß1 in hepatoma cells along with prostate cancer cells, PC3. Transient transfection assays showed that the -109 to +63 promoter region contained the minimal TGF-ß1 response elements. TGF-ß1 markedly stimulated the URG-4/URGCP mRNA and protein that was blocked by MEK1 [MAPK (Mitogen-Activated Protein Kinase)/ERK (extracellular signal-regulated kinase) kinase 1] inhibitor, PD98059 and PI3K inhibitor, wortmannin. SIGNIFICANCE: These studies show for the first time that TGF-ß1 upregulates the expression of URG-4/URGCP in human hepatocytes and identifies the signaling pathways underlying this response.

Effects of active MEK1 expression in vivo.

Cell transformation is often a result of constitutive activation of genes in signaling pathways that regulate cell proliferation and differentiation. Indeed, the Ras/Raf/MEK/ERK mitogen-activated protein kinase (MAPK) signaling pathway is constitutively activated in a large number of cancers. The extent to which a single-gene mutation can alter cell fate, however, remains questionable. In vitro studies have addressed this issue, but organs are comprised of multiple cell types, and in vitro models often poorly approximate these interactions. In response to these limitations, cell-type specific mouse models have been generated as a means to examine the effect of altering a single element of the MAPK pathway in vivo. This review summarizes data from transgenic murine and human tissue models expressing constitutive active forms of MEK1.