Glycogen synthase kinase 3 beta: can it be a target for oral cancer

Moguntinones--new selective inhibitors for the treatment of human colorectal cancer

3-Indolyl and 3-azaindolyl-4-aryl maleimide derivatives, called moguntinones (MOG), have been selected for their ability to inhibit protein kinases associated with angiogenesis and induce apoptosis. Here, we characterize their mode of action and their potential clinical value in human colorectal cancer in vitro and in vivo. MOG-19 and MOG-13 were characterized in vitro using kinase, viability, and apoptosis assays in different human colon cancer (HT-29, HCT-116, Caco-2, and SW480) and normal colon cell lines (CCD-18Co, FHC, and HCoEpiC) alone or in combination with topoisomerase I inhibitors. Intracellular signaling pathways were analyzed by Western blotting. To determine their potential to inhibit tumor growth in vivo, the human HT-29 tumor xenograft model was used. Moguntinones prominently inhibit several protein kinases associated with tumor growth and metastasis. Specific signaling pathways such as GSK3β and mTOR downstream targets were inhibited with IC(50) values in the nanomolar range. GSK3β signaling inhibition was independent of KRAS, BRAF, and PI3KCA mutation status. While moguntinones alone induced apoptosis only in concentrations >10 μmol/L, MOG-19 in combination with topoisomerase I inhibitors induced apoptosis synergistically at lower concentrations. Consistent with in vitro data, MOG-19 significantly reduced tumor volume and weight in combination with a topoisomerase I inhibitor in vivo. Our in vitro and in vivo data present significant proapoptotic, antiangiogenic, and antiproliferative effects of MOG-19 in different human colon cancer cells. Combination with clinically relevant topoisomerase I inhibitors in vitro and xenograft mouse model demonstrate a high potency of moguntinones to complement and improve standard chemotherapy options in human colorectal cancer.

Maintaining glycogen synthase kinase-3 activity is critical for mTOR kinase inhibitors to inhibit cancer cell growth

mTOR kinase inhibitors that target both mTORC1 and mTORC2 are being evaluated in cancer clinical trials. Here, we report that glycogen synthase kinase-3 (GSK3) is a critical determinant for the therapeutic response to this class of experimental drugs. Pharmacologic inhibition of GSK3 antagonized their suppressive effects on the growth of cancer cells similarly to genetic attenuation of GSK3. Conversely, expression of a constitutively activated form of GSK3β sensitized cancer cells to mTOR inhibition. Consistent with these findings, higher basal levels of GSK3 activity in a panel of human lung cancer cell lines correlated with more efficacious responses. Mechanistic investigations showed that mTOR kinase inhibitors reduced cyclin D1 levels in a GSK3β-dependent manner, independent of their effects on suppressing mTORC1 signaling and cap binding. Notably, selective inhibition of mTORC2 triggered proteasome-mediated cyclin D1 degradation, suggesting that mTORC2 blockade is responsible for GSK3-dependent reduction of cyclin D1. Silencing expression of the ubiquitin E3 ligase FBX4 rescued this reduction, implicating FBX4 in mediating this effect of mTOR inhibition. Together, our findings define a novel mechanism by which mTORC2 promotes cell growth, with potential implications for understanding the clinical action of mTOR kinase inhibitors.

GSK3β overexpression indicates poor prognosis and its inhibition reduces cell proliferation and survival of non-small cell lung cancer cells

BACKGROUND

Glycogen synthase kinase 3 beta (GSK3β) is centrally involved in diverse cellular processes, including proliferation and apoptosis. This study aimed to investigate the influence of GSK3β expression on the prognosis of human non-small cell lung cancer (NSCLC) and the effects of GSK3β inhibition in NSCLC cell lines.

METHODS

Immunohistochemical and western blot assays were used to evaluate the GSK3β expression level in human NSCLC tissues. Lentiviral RNA interference was performed to inhibit the expression of GSK3β in the A549, H292, H1299 and SK-MES-1 cell lines. Cell survival, apoptosis and motility were evaluated in vivo and in vitro.

RESULTS

The levels of GSK3β were greater in NSCLC tissues (n = 211) than in control tissues (n = 194) (P<0.001). The 5-year follow-up analysis showed that positive GSK3β expression was indicative of poor prognosis (P = 0.006). Furthermore, knockdown of GSK3β in NSCLC cell lines suppressed cell proliferation, arrested tumor cells in G0/G1 phase, induced apoptosis and reduced cell motility. A xenograft model showed that the deregulation of GSK3β attenuated tumorigenesis, as confirmed by reduced cell proliferation based on Ki-67 and significantly increased apoptotic cell death. The inhibition of GSK3β had inconsistent effects on the expression of β-catenin, depending on the cell type examined.

CONCLUSION

Aberrant expression of GSK3β serves as an independent marker of poor prognosis for NSCLC. The inhibition of GSK3β suppressed tumorigenesis by attenuating cell proliferation, increasing apoptosis and restraining cell motility. These results identify GSK3β as a tumor promoter and a potential therapeutic target in NSCLC.

Resveratrol plays dual roles in pancreatic cancer cells

PURPOSE

Although the potential anticancer effect of resveratrol (RSV) on pancreatic cancer has been reported, its mechanism was not fully understood. The role of vascular endothelial growth factor B (VEGF-B) in cancer remains controversial. Herein, we aimed to examine whether the anticancer effect of RSV was related to the VEGF-B.

METHODS

The effect of RSV on pancreatic cancer cell line (capan-2 cells) was evaluated by CCK-8 assay, Hoechst 33342 staining, and flow cytometry. The mRNA level of VEGF-B was measured by real-time PCR. VEGF-B expression was knockdown by small interfering RNA (siRNA).The protein levels of VEGF-B, glycogen synthase kinase-3 beta (GSK-3β), and Bax were measured by Western blot.

RESULTS

Resveratrol treatment inhibited tumor growth, induced apoptosis, and up-regulated Bax expression in capan-2 cells. The mRNA and protein levels of VEGF-B were up-regulated after RSV treatment. However, VEGF-B siRNA treatment increased the apoptotic rate, and inhibited tumor activator GSK-3β, while Bax expression was not affected. The combination of RSV and VEGF-B siRNA showed significantly higher apoptotic rate in comparison with RSV or VEGF-B siRNA mono-treatment group.

CONCLUSIONS

Resveratrol plays dual roles in pancreatic cancer: as a tumor suppressor via the up-regulation of Bax; as a tumor activator via the up-regulation of VEGF-B; and the anticancer effect of RSV is much stronger than the cancer promotion effect. The combination of RSV with pharmacological inhibitor of VEGF-B might, therefore, be a promising modality for clinical pancreatic cancer therapy.

Cytomodulin-1, a synthetic peptide abrogates oncogenic signaling pathways to impede invasion and angiogenesis in the hamster cheek pouch carcinogenesis model

Constitutive activation of the various oncogenic signaling pathways plays a pivotal role in promoting malignant transformation. The aim of this study was to investigate the therapeutic potential of a synthetic bioactive heptapeptide cytomodulin-1 (CM-1) against hamster cheek pouch carcinomas based on its influence on the predominant carcinogenic signaling pathways - NF-κB, TGFβ, and Wnt/β-catenin and their downstream target events invasion and angiogenesis. Topical application of CM-1 to DMBA-painted hamsters significantly inhibited activation of the canonical NF-κB pathway by blocking kinase activity of IKKβ and increasing the cytosolic accumulation of the inhibitor IκB-α. In addition, CM-1 inactivated IKKβ by disrupting IKKβ/Nemo interactions. CM-1 also hampered the activation of TGFβ and Wnt/β-catenin signaling by averting the phosphorylation of the key upstream ser/thr kinases TGFβ RI and GSK-3β respectively. Attenuation of these oncogenic signaling pathways by CM-1 also mitigated invasion and angiogenesis by suppressing the expression of pro-invasive matrix metalloproteinases, pro-angiogenic VEGF and HIF-1α and upregulating the anti-angiogenic TIMP-2. Synthetic peptides such as CM-1 that target multiple key molecules in oncogenic signaling pathways and their downstream events are ideal candidate agents for cancer chemotherapy.

GSK3β negatively regulates HIF1α mRNA stability via nucleolin in the MG63 osteosarcoma cell line

Hypoxia-inducible factor 1α (HIF1α) is a transcription factor involved in the growth, invasion and metastasis of malignant tumors. Glycogen synthase kinase 3 beta (GSK3β) is a protein kinase involved in a variety of signaling pathways, such as the Wnt and NF-κB pathways; this kinase can affect tumor progress through the regulation of transcription factor expression and apoptosis. Recent studies showed that GSK3β was involved in the expression of HIF1α. However, the effect of GSK3β on HIF1α expression in osteosarcoma cells remains unknown. To understand the relationship between GSK3β and HIF1α comprehensively, small RNA interference techniques, Western blot analyses, quantitative real-time PCR analyses and luciferase assays were used in our study. Experimental data revealed that inhibition of GSK3β could increase HIF1α protein levels and expression of its target genes by increasing the stability of the HIF1α mRNA, not by affecting the HIF1α protein stability, and that this process could be mediated by nucleolin.

Concerted suppression of STAT3 and GSK3β is involved in growth inhibition of non-small cell lung cancer by Xanthatin

Xanthatin, a sesquiterpene lactone purified from Xanthium strumarium L., possesses prominent anticancer activity. We found that disruption of GSK3β activity was essential for xanthatin to exert its anticancer properties in non-small cell lung cancer (NSCLC), concurrent with preferable suppression of constitutive activation of STAT3. Interestingly, inactivation of the two signals are two mutually exclusive events in xanthatin-induced cell death. Moreover, we surprisingly found that exposure of xanthatin failed to trigger the presumable side effect of canonical Wnt/β-Catenin followed by GSK3β inactivation. We further observed that the downregulation of STAT3 was required for xanthatin to fine-tune the risk. Thus, the discovery of xanthatin, which has ability to simultaneously orchestrate two independent signaling cascades, may have important implications for screening promising drugs in cancer therapies.

Monosaccharide digitoxin derivative sensitize human non-small cell lung cancer cells to anoikis through Mcl-1 proteasomal degradation

Advanced stage cancers acquire anoikis resistance which provides metastatic potential to invade and form tumors at distant sites. Suppression of anoikis resistance by novel molecular therapies would greatly benefit treatment strategies for metastatic cancers. Recently, digitoxin and several of its novel synthetic derivatives, such as α-l-rhamnose monosaccharide derivative (D6-MA), have been synthesized and studied for their profound anticancer activity in various cancer cell lines. In this study, we investigated the anoikis sensitizing effect of D6-MA compared with digitoxin to identify their anti-metastatic mechanism of action. D6-MA sensitized NSCLC H460 cells to detachment-induced apoptosis with significantly greater cytotoxicity (IC50=11.9 nM) than digitoxin (IC50=90.7 nM) by activating caspase-9. Screening of the Bcl-2 protein family revealed that degradation of anti-apoptotic Mcl-1 protein is a favorable target. Mcl-1 over-expression and knockdown studies in D6-MA and digitoxin exposed cells resulted in rescue and enhancement, respectively, indicating a facilitative role for decreased Mcl-1 expression in NSCLC anoikis. Transfection with mutant Mcl-1S159 attenuated detachment-induced cell death and correlated with a remaining of Mcl-1 level. Furthermore, D6-MA suppressed Mcl-1 expression via ubiquitin proteasomal degradation that is dependent on activation of glycogen synthase kinase (GSK)-3β signaling. In addition, D6-MA also targeted Mcl-1 degradation causing an increased anoikis in A549 lung cancer cells. Anoikis sensitizing effect on normal small airway epithelial cells was not observed indicating the specificity of D6-MA and digitoxin for NSCLC. These results identify a novel cardiac glycoside (CG) sensitizing anoikis mechanism and provide a promising anti-metastatic target for lung cancer therapy.

AEG-1 is a target of perifosine and is over-expressed in gastric dysplasia and cancers

BACKGROUND

Perifosine, an alkylphospholipid, is an Akt inhibitor which inhibits the growth of diverse cancer cells. We have reported its inhibitory effects on the growth of gastric cancer cells recently, but its molecular mechanisms are still largely unknown.

AIMS

The purpose of this study was to investigate the effect and regulatory mechanism of perifosine in gastric cancer.

METHODS

Cell viability was determined by sulforhodamine B assay after transiently transfected with AEG-1 specific siRNAs. qRT-PCR and western blot assay were used to determine the mRNA expression and proteins levels of cell signaling molecules examined. Immunohistochemistry was used to detect the AEG-1 expression in 87 gastric carcinomas, 60 dysplasia, and 47 normal gastric mucosa.

RESULTS

Perifosine decreased AEG-1 gene expression along with inhibition of Akt/GSK3β/C-MYC signaling pathway. Knockdown of AEG-1 using siRNA led to significant down-regulation of cyclin D1 expression at both mRNA level and protein level, and inhibited the growth of gastric cancer cells. AEG-1 expression was elevated in gastric dysplasia and cancer tissues compared to normal gastric mucosa (P < 0.01). AEG-1 over-expression correlated with diffuse type of gastric cancer and advanced tumor stages.

CONCLUSIONS

Perifosine inhibits the growth of gastric cancer cells possibly through inhibition of the Akt/GSK3β/C-MYC signaling pathway-mediated down-regulation of AEG-1 that subsequently down-regulated cyclin D1. AEG-1 may play an important role in the carcinogenesis and progression of gastric cancer and could be a therapeutic target of perifosine.

Ligand-activated peroxisome proliferator-activated receptor β/δ modulates human endometrial cancer cell survival

Endometrial cancer is the fourth most common malignancy among women and is a major cause of morbidity contributing to approximately 8,200 annual deaths in the USA. Despite advances to the understanding of endometrial cancer, novel interventions for the disease are necessary given that many tumors become refractory to therapy. As a strategy to identify novel therapies for endometrial carcinoma, in this study, we examined the contribution of the peroxisome proliferator-activated receptor β/δ (PPARβ/δ) to endometrial cancer cell proliferation and apoptosis. We found that when activated with the highly selective PPARβ/δ agonists, GW0742 and GW501516, PPARβ/δ inhibited the proliferation and markedly induced the apoptosis of three endometrial cancer cell lines. The specificity of the PPARβ/δ-induced effects on cell proliferation and apoptosis was demonstrated using PPARβ/δ-selective antagonists and PPARβ/δ small interfering RNA in combination with PPARβ/δ-selective agonists. Furthermore, we showed that PPARβ/δ activation increased phosphatase and tensin homolog expression, which led to protein kinase B (AKT) and glycogen synthase kinase-3β (GSK3β) dephosphorylation, and increased β-catenin phosphorylation associated with its degradation. Overall, our data suggest that the antitumorigenic effect of PPARβ/δ activation in endometrial cancer is mediated through the negative regulation of the AKT/GSK3β/β-catenin pathway. These findings warrant further investigation of PPARβ/δ as a therapeutic target in endometrial cancer.

PIMT prevents the apoptosis of endothelial cells in response to glycated low density lipoproteins and protective effects of grape seed procyanidin B2

Background

The development of diabetic angiopathy is associated with profound vascular endothelial cells (VEC) dysfunction and apoptosis. Glycated low density lipoproteins (gly-LDL) continuously produced in the setting of diabetic patients play an important role in causing VEC dysfunction and apoptosis. However, the underlying molecular mechanism remains largely elusive. Protein L-isoaspartyl methyltransferase (PIMT) is a widely expressed protein repair enzyme by multiple cell types of arterial wall including VEC. Our previous proteomic studies showed that the expression of PIMT was significantly decreased in the aorta of diabetic rats as compared with control rats and treatment with grape seed procyanidin extracts significantly increased the PIMT expression in diabetic rats. We hypothesized that PIMT plays a critical role in gly-LDL induced VEC apoptosis; grape seed procyanidin B2 (GSPB2) protect against gly-LDL induced VEC apoptosis through PIMT regulation.

Methods and Results

HUVEC transfected negative control and PIMT siRNA were treated with or without GSPB2 (10 µmol/L) for 48 h. Moreover, HUVEC of PIMT overexpression were stimulated by gly-LDL (50 µg/ml) in the presence or absence of GSPB2 (10 µmol/L) for 48 h. Our results showed that gly-LDL downregulated PIMT expression and PIMT overexpression or GSPB2 significantly attenuated gly-LDL induced VEC apoptosis. PIMT siRNA increased VEC apoptosis with up-regulation of p53, cytochrome c release, caspase-9 and caspase-3 activation. Mechanistically, overexpression of PIMT or GSPB2 increased the phosphorylation of ERK1/2 and GSK3β in the gly-LDL induced VEC.

Conclusion

In summary, our study identified PIMT as a key player responsible for gly-LDL induced VEC apoptosis and GSPB2 protect against gly-LDL induced VEC apoptosis by PIMT up-regulation. Targeting PIMT including use of GSPB2 could be turned into clinical application in the fighting against diabetic vascular complications.

Role of fucosyltransferase IV in epithelial-mesenchymal transition in breast cancer cells

Epithelial–mesenchymal transition (EMT) is a crucial step in tumor progression and has an important role during cancer invasion and metastasis. Although fucosyltransferase IV (FUT4) has been implicated in the modulation of cell migration, invasion and cancer metastasis, its role during EMT is unclear. This study explores the molecular mechanisms of the involvement of FUT4 in EMT in breast cancer cells. Breast cancer cell lines display increased expression of FUT4, which is accompanied by enhanced appearance of the mesenchymal phenotype and which can be reversed by knockdown of endogenous FUT4. Moreover, FUT4 induced activation of phosphatidylinositol 3-kinase (PI3K)/Akt, and inactivation of GSK3β and nuclear translocation of NF-κB, resulting in increased Snail and MMP-9 expression and greater cell motility. Taken together, these findings indicate that FUT4 has a role in EMT through activation of the PI3K/Akt and NF-κB signaling systems, which induce the key mediators Snail and MMP-9 and facilitate the acquisition of a mesenchymal phenotype. Our findings support the possibility that FUT4 is a novel regulator of EMT in breast cancer cells and a promising target for cancer therapy.

GSK3β controls epithelial-mesenchymal transition and tumor metastasis by CHIP-mediated degradation of Slug

Glycogen synthase kinase 3 beta (GSK3β) is highly inactivated in epithelial cancers and is known to inhibit tumor migration and invasion. The zinc-finger-containing transcriptional repressor, Slug, represses E-cadherin transcription and enhances epithelial-mesenchymal transition (EMT). In this study, we find that the GSK3β-pSer9 level is associated with the expression of Slug in non-small cell lung cancer. GSK3β-mediated phosphorylation of Slug facilitates Slug protein turnover. Proteomic analysis reveals that the carboxyl terminus of Hsc70-interacting protein (CHIP) interacts with wild-type Slug (wtSlug). Knockdown of CHIP stabilizes the wtSlug protein and reduces Slug ubiquitylation and degradation. In contrast, nonphosphorylatable Slug-4SA is not degraded by CHIP. The accumulation of nondegradable Slug may further lead to the repression of E-cadherin expression and promote cancer cell migration, invasion and metastasis. Our findings provide evidence of a de novo GSK3β-CHIP-Slug pathway that may be involved in the progression of metastasis in lung cancer.

Yerba mate tea and mate saponins prevented azoxymethane-induced inflammation of rat colon through suppression of NF-κB p65ser(311) signaling via IκB-α and GSK-3β reduced phosphorylation

Yerba mate tea (YMT) has a chemopreventive role in a variety of inflammatory diseases. The objective was to determine the capability of YMT and mate saponins to prevent azoxymethane (AOM)-induced colonic inflammation in rats. YMT (2% dry leaves, w/v, as a source of drinking fluid) (n = 15) and mate saponins (0.01% in the diet, at a concentration present in one cup of YMT) (n = 15) were given ad libitum to rats 2 weeks prior to AOM-injection until the end of the study; while control rats (n = 15) received a basal diet and drinking water. After 8-weeks of study, total colonic mucosa was scraped (n = 3 rats/group) and the remaining colons (n =12 rats/group) were cut into three equal sections and aberrant crypt foci (ACF) were analyzed. YMT reduced ACF formation from 113 (control group) to 89 (P < 0.05). YMT and mate saponins reduced the expression of proinflammatory molecules COX-2 and iNOS with concomitant reduction in p-p65 (P < 0.05). Immunohistochemical analysis of the formalin-fixed middle colons showed that YMT and mate saponins reduced the expression of p-p65(ser311) by 45.7% and 43.1%, respectively, in comparison to the control (P < 0.05). In addition, the expression of molecules upstream of NF-κB such as p-IκB-α and p-GSK-3β(Y216) was downregulated by YMT 24.7% and 24.4%, respectively (P < 0.05). Results suggest the mechanism involved in the chemopreventive effect of YMT and mate saponin consumption in AOM induced-colonic inflammation in rats is through inhibition of NF-κB.

Amyloid beta-induced glycogen synthase kinase 3β phosphorylated VDAC1 in Alzheimer's disease: implications for synaptic dysfunction and neuronal damage

Glycogen synthase kinase 3 (GSK3) is a serine/threonine protein kinase that is involved in the multiple signaling processes of a cell. Increasing evidence suggests that GSK3β plays a key role in multiple cellular processes in the progression of diabetes, obesity, Alzheimer's disease (AD), Parkinson's disease (PD), inflammatory diseases, schizophrenia, bipolar and several mood disorders, and mitochondrial diseases. Recent research has found that increased GSK3β activity is linked to the pathogenesis of AD through amyloid beta (Aβ), phosphorylated tau and mitochondrial dysfunction. Recent research has also revealed that GSK3β is elevated in AD-affected tissues and is critically involved in dissociating the voltage-dependent anion channel 1 (VDAC1) protein from hexokinases, and causing disrupted glucose metabolism, mitochondrial dysfunction and activating apoptotic cell death. The purpose of this article is to review recent research that is elucidating the role of GSK3β in AD pathogenesis. We discuss the involvement of GSK3β in the phosphorylation of VDAC1 and dissociation of VADC1 with hexokinases in AD neurons.

Multifaceted roles of GSK-3 and Wnt/β-catenin in hematopoiesis and leukemogenesis: opportunities for therapeutic intervention

Glycogen synthase kinase-3 (GSK-3) is well documented to participate in a complex array of critical cellular processes. It was initially identified in rat skeletal muscle as a serine/threonine kinase that phosphorylated and inactivated glycogen synthase. This versatile protein is involved in numerous signaling pathways that influence metabolism, embryogenesis, differentiation, migration, cell cycle progression and survival. Recently, GSK-3 has been implicated in leukemia stem cell pathophysiology and may be an appropriate target for its eradication. In this review, we will discuss the roles that GSK-3 plays in hematopoiesis and leukemogenesis as how this pivotal kinase can interact with multiple signaling pathways such as: Wnt/β-catenin, phosphoinositide 3-kinase (PI3K)/phosphatase and tensin homolog (PTEN)/Akt/mammalian target of rapamycin (mTOR), Ras/Raf/MEK/extracellular signal-regulated kinase (ERK), Notch and others. Moreover, we will discuss how targeting GSK-3 and these other pathways can improve leukemia therapy and may overcome therapeutic resistance. In summary, GSK-3 is a crucial regulatory kinase interacting with multiple pathways to control various physiological processes, as well as leukemia stem cells, leukemia progression and therapeutic resistance. GSK-3 and Wnt are clearly intriguing therapeutic targets.

Astaxanthin inhibits NF-κB and Wnt/β-catenin signaling pathways via inactivation of Erk/MAPK and PI3K/Akt to induce intrinsic apoptosis in a hamster model of oral cancer

BACKGROUND

The oncogenic transcription factors NF-κB and β-catenin, constitutively activated by upstream serine/threonine kinases control several cellular processes implicated in malignant transformation including apoptosis evasion. The aim of this study was to investigate the chemopreventive effects of astaxanthin, an antioxidant carotenoid, in the hamster buccal pouch (HBP) carcinogenesis model based on its ability to modulate NF-κB and Wnt signaling pathways and induce apoptosis.

METHODS

We determined the effect of dietary supplementation of astaxanthin on the oncogenic signaling pathways - NF-κB and Wnt/β-catenin, their upstream activator kinases - Erk/MAPK and PI-3K/Akt, and the downstream event - apoptosis evasion by real-time quantitative RT-PCR, western blot, and immunohistochemical analyses.

RESULTS

We found that astaxanthin inhibits NF-κB and Wnt signaling by downregulating the key regulatory enzymes IKKβ and GSK-3β. Analysis of gene expression and docking interactions revealed that inhibition of these pathways may be mediated via inactivation of the upstream signaling kinases Erk/Akt by astaxanthin. Astaxanthin also induced caspase-mediated mitochondrial apoptosis by downregulating the expression of antiapoptotic Bcl-2, p-Bad, and survivin and upregulating proapoptotic Bax and Bad, accompanied by efflux of Smac/Diablo and cytochrome-c into the cytosol, and induced cleavage of poly (ADP-ribose) polymerase (PARP).

CONCLUSIONS

The results provide compelling evidence that astaxanthin exerts chemopreventive effects by concurrently inhibiting phosphorylation of transcription factors and signaling kinases and inducing intrinsic apoptosis.

GENERAL SIGNIFICANCE

Astaxanthin targets key molecules in oncogenic signaling pathways and induces apoptosis and is a promising candidate agent for cancer prevention and therapy.

The importance of oncogenic transcription factors for oral cancer pathogenesis and treatment

Oral squamous cell carcinoma is a major cause of morbidity and mortality worldwide. Current experimental evidence shows that most important risk factors for oral cancer include tobacco use and excessive alcohol consumption and less well-defined risks include viral infection and a diet deficient in antioxidants. The positive correlation between various risk/etiologic factors of oral cancer and the activation of various transcription factors (TFs) has been reported in the literature. Although initially, TFs were considered to be very difficult targets for use in clinical treatment, recent technological advances have provided the ability to control these factors of cancer progression. This review focuses on the role of oncogenic transcription factors in oral cancer, their modes of activation through various biological pathways, the promises and pitfalls in viewing them as potent oncotargets, the way they can be controlled based on the current understanding, and the future research to be done in this area.

Cell cycle-regulatory cyclins and their deregulation in oral cancer

Oral cancer is a growth-related disorder, and cyclins are the prime regulators of cell division. Cyclins are associated with the pathogenesis of oral cancer and are considered valuable biomarkers for diagnosis and prognosis. These important molecules are regulated in many ways to achieve a gain in function and are involved in promoting neoplastic growth. While the causes of most cyclin overexpression are varied, these cyclins may be induced by buccal mucosal insult mainly with carcinogens that alter various pathways propelling oral cancer. Substantial experimental evidences support a link between oncogenic signaling pathways and the deregulation of cyclins in oral cancer. This review focuses on the mechanisms by which cyclins are regulated and promote oral oncogenesis.

Glycogen Synthase Kinase 3β Inhibitor (2'Z,3'E)-6-Bromo-indirubin- 3'-Oxime Enhances Drug Resistance to 5-Fluorouracil Chemotherapy in Colon Cancer Cells

OBJECTIVE

To explore the effects and mechanism of glycogen synthase kinase 3β (GSK-3β) inhibitor (2'Z,3'E)-6-bromo-indirubin-3'-oxime (BIO) on drug resistance in colon cancer cells.

METHODS

The colon cancer SW480 and SW620 cells were treated with BIO, 5-fluorouracil (5-FU) and BIO/5-FU, separately. Cell cycle distribution, apoptosis level and efflux ability of rhodamine 123 (Rh123) were detected by flow cytometry. The protein expressions of P-glycoprotein (P-gp), multidrug resistance protein 2 (MRP2), thymidylate synthase (TS), β-catenin, E2F-1 and Bcl-2 were detected by Western blot. β-catenin and P-gp were stained with double immunofluorescence and observed under a confocal microscope.

RESULTS

BIO up-regulated β-catenin, P-gp, MRP2 and TS, enhanced the efflux ability of Rh123, decreased Bcl-2 protein and gave the opposite effect to E2F-1 protein in SW480 and SW620 cells. Furthermore, BIO significantly inhibited cell apoptosis, increased S and G(2)/M phase cells, and reduced the cell apoptosis induced by 5-FU in SW480 cells, whereas the effects were slight or not obvious in SW620 cells.

CONCLUSION

GSK-3β was involved in drug resistance regulation, and activation of β-catenin and inhibition of E2F-1 may be the most responsible for the enhancement of 5-FU chemotherapy resistance induced by GSK-3β inhibitor BIO in colon cancer.

Circulating tumour cells and cancer stem cells: a role for proteomics in defining the interrelationships between function, phenotype and differentiation with potential clinical applications

Research on the discovery and implementation of valid cancer biomarkers is one of the most challenging fields in oncology and oncoproteomics in particular. Moreover, it is generally accepted that an evaluation of cancer biomarkers from the blood could significantly enable biomarker assessments by providing a relatively non-invasive source of representative tumour material. In this regard, circulating tumour cells (CTCs) isolated from the blood of metastatic cancer patients have significant promise. It has been demonstrated that localised and metastatic cancers may give rise to CTCs, which are detectable in the bloodstream. Despite technical difficulties, recent studies have highlighted the prognostic significance of the presence and number of CTCs in the blood. Future studies are necessary not only to detect CTCs but also to characterise them. Furthermore, another pathogenically significant type of cancer cells, known as cancer stem cells (CSCs) or more recently termed circulating tumour stem cells (CTSCs), appears to have a significant role as a subpopulation of CTCs. This review discusses the potential application of proteomic methodologies to improve the isolation and characterisation of CTCs and to distinguish between CTCs with a poor clinical significance and those with important biological and clinical implications.

PANC-1 cells proliferative response to ionizing radiation is related to GSK-3β phosphorylation

Radiotherapy may be used to treat pancreatic cancer and relieve pain. We have previously reported that histamine modulates pancreatic adenocarcinoma PANC-1 cell proliferation. This work was aimed to evaluate whether histamine improves radiosensitivity of PANC-1 cells in relation to phosphorylation/inhibition of glycogen synthase kinase-3β (GSK-3β). Immediately after γ irradiation, intracellular hydrogen peroxide was markedly decreased together with a rapid increase in catalase activity. Although histamine diminished catalase activity in nonirradiated cells, it only partially hindered the increase observed in irradiated cells and could not modify radiosensitivity. In control cells, a high expression of total and a very low expression of phosphorylated/inactive GSK-3β were found. An increment in reactive oxygen species levels produced an augmentation in GSK-3β phosphorylation and suppressed cell proliferation. In both control and histamine-treated irradiated cells, the rise in catalase activity lowered reactive oxygen species levels and only a small increase in phosphorylated GSK-3β was detected. Alternatively, 3-aminotriazole, an irreversible inhibitor of catalase, reduced the survival fraction in irradiated control cells along with an increment in phosphorylated GSK-3β. These results suggest that upon irradiation, early catalase activation may be responsible for keeping GSK-3β active conceding cells a survival advantage toward cytotoxic effects of ionizing radiation.

Dietary phytochemicals and cancer prevention: Nrf2 signaling, epigenetics, and cell death mechanisms in blocking cancer initiation and progression

Reactive metabolites from carcinogens and oxidative stress can drive genetic mutations, genomic instability, neoplastic transformation, and ultimately carcinogenesis. Numerous dietary phytochemicals in vegetables/fruits have been shown to possess cancer chemopreventive effects in both preclinical animal models and human epidemiological studies. These phytochemicals could prevent the initiation of carcinogenesis via either direct scavenging of reactive oxygen species/reactive nitrogen species (ROS/RNS) or, more importantly, the induction of cellular defense detoxifying/antioxidant enzymes. These defense enzymes mediated by Nrf2-antioxidative stress and anti-inflammatory signaling pathways can contribute to cellular protection against ROS/RNS and reactive metabolites of carcinogens. In addition, these compounds would kill initiated/transformed cancer cells in vitro and in in vivo xenografts via diverse anti-cancer mechanisms. These mechanisms include the activation of signaling kinases (e.g., JNK), caspases and the mitochondria damage/cytochrome c pathways. Phytochemicals may also have anti-cancer effects by inhibiting the IKK/NF-κB pathway, inhibiting STAT3, and causing cell cycle arrest. In addition, other mechanisms may include epigenetic alterations (e.g., inhibition of HDACs, miRNAs, and the modification of the CpG methylation of cancer-related genes). In this review, we will discuss: the current advances in the study of Nrf2 signaling; Nrf2-deficient tumor mouse models; the epigenetic control of Nrf2 in tumorigenesis and chemoprevention; Nrf2-mediated cancer chemoprevention by naturally occurring dietary phytochemicals; and the mutation or hyper-expression of the Nrf2-Keap1 signaling pathway in advanced tumor cells. The future development of dietary phytochemicals for chemoprevention must integrate in vitro signaling mechanisms, relevant biomarkers of human diseases, and combinations of different phytochemicals and/or non-toxic therapeutic drugs, including NSAIDs.

GSK3β and CREB3 gene expression profiling in benign and malignant salivary gland tumors

BACKGROUND

Salivary gland tumors (SGT) are rare lesions with uncertain histopathology. One of the major signaling pathways that participate in the development of several tumors is protein kinase A. In this pathway, glycogen synthase kinase β (GSK3β) and cAMP responsive element binding protein (CREB3) are two genes which are supposed to be down regulated in most human tumors. The expression level of the genes was evaluated in SGT to scrutinize their possible under expression in these tumors.

METHODS

Forty eight fresh tissue samples were obtained from patients with benign and malignant SGT, including pleomorphic adenoma, warthin's tumor, mucoepidermoid carcinoma (MEC), salivary duct carcinoma and carcinoma ex pleomorphic adenoma. Eight normal samples were used as controls. Quantitative real-time PCR was used to analyze the expression level of interest genes.

RESULTS

Data was analyzed by statistical methods. GSK3β was downregulate in all samples and all results were statistically significant (P<0.05). CREB3 did not show a significant decrease or increase in its mRNA expression, but the results were significant in MEC and salivary duct carcinoma.

CONCLUSION

GSK3β down regulation has been reported in many human tumors. This gene stimulates CREB3, inducing cell proliferation and oncogenesis. Our findings showed GSK β down regulation; however, CREB3 expression level was close to normal group. No association between CREB3 expression and inactivated GSK3β could be postulated in SGT.

The nuclear localization of glycogen synthase kinase 3β is required its putative PY-nuclear localization sequences

Glycogen synthase kinase-3β(GSK-3β), which is a member of the serine/threonine kinase family, has been shown to be crucial for cellular survival, differentiation, and metabolism. Here, we present evidence that GSK-3β is associated with the karyopherin β2 (Kap β2) (102-kDa), which functions as a substrate for transportation into the nucleus. A potential PY-NLS motif ((109)IVRLRYFFY(117)) was observed, which is similar with the consensus PY NLS motif (R/K/H)X(2-5)PY in the GSK-3β catalytic domain. Using a pull down approach, we observed that GSK-3β physically interacts with Kap β2 both in vivo and in vitro. Secondly, GSK-3β and Kap β2 were shown to be co-localized by confocal microscopy. The localization of GSK-3β to the nuclear region was disrupted by putative Kap β2 binding site mutation. Furthermore, in transient transfection assays, the Kap β2 binding site mutant induced a substantial reduction in the in vivo serine/threonine phosphorylation of GSK-3β, where- as the GSK-3β wild type did not. Thus, our observations indicated that Kap β2 imports GSK-3β through its putative PY NLS motif from the cytoplasm to the nucleus and increases its kinase activity.

R280T mutation of p53 gene promotes proliferation of human glioma cells through GSK-3β/PTEN pathway

p53 mutation is associated with "gain-of-function" capabilities of human cancers. We aim to identify p53 mutations in human glioma cells and to explore the potential mechanism for mutant p53-promoted cellular growth. Whole genomic DNA was isolated from SWO-38, a human glioma cell line and amplified for the region of exons 5, 6, and 8 in p53 gene using polymerase chain reaction (PCR). By means of direct sequencing of PCR products and alignment analysis using BLAST database, a mutation of G to C transition at codon 280 of p53 exon 8 (AGA→ACA), i.e. R280T was detected in SWO-38 cells. Knockdown of R280T mutant p53 by RNA interference inhibited the GSK-3β/PTEN associated cell proliferation, and PI3K/Akt but not Wnt/β-catenin signaling pathway was involved in this process. Furthermore, depletion or overexpression of PTEN alone did not affect cell proliferation and cell cycle, implicating the impairment of PTEN function in SWO-38 cells. However, knockdown of both PTEN and p53 mutation could significantly rescue the p53 depletion-mediated growth inhibition, suggesting that the R280T mutation in glioma may promote the proliferation through an underlying mechanism related to PTEN. Our observations indicate that the R280T mutation of p53 regulates the proliferation of human glioma cells related to the GSK-3β/PTEN pathway. These findings provide valuable insights for better understanding the molecular mechanism of uncontrolled growth of glioma cells.

Depleting IFIT2 mediates atypical PKC signaling to enhance the migration and metastatic activity of oral squamous cell carcinoma cells

Interferon-induced protein with tetratricopeptide repeats 2 (IFIT2) is one of the most highly responsive interferon-stimulated genes, but its biological functions are poorly understood. In this study, we aimed to explore the underlying mechanisms by which depleting IFIT2 induces the migration of oral squamous cell carcinoma (OSCC) cells. Stable IFIT2-depleted cells underwent epithelial-mesenchymal transition (EMT) and exhibited enhanced cell motility and invasiveness compared with control cells. Furthermore, our results indicated that atypical protein kinase C (aPKC) was activated in IFIT2-depleted cells. Inhibition of aPKC using a specific myristoylated PKCζ pseudosubstrate or aPKC-targeting small interfering RNA (siRNA) abolished IFIT2 depletion-induced EMT, migration and invasion, indicating that the activation of aPKC has an essential role in regulating the cellular responses induced by IFIT2 depletion. Following tail-vein injection, IFIT2-depleted OSCC cells colonized not only the lungs but also the heart, head and neck, retroperitoneal, and peritoneal cavities; whereas control cells predominantly localized in the lungs. IFIT2 mRNA and protein expression was positively associated with E-cadherin expression in OSCC patient specimens. The loss of E-cadherin and IFIT2 expression was observed at the invasive front of OSCC tumors, suggesting that the loss of IFIT2 may induce EMT and lead to the metastasis of OSCCs. OSCC patients possessing reduced IFIT2-expression levels (IFIT2 <50%) exhibited greater rates of distant metastasis and poor prognoses compared with OSCC patients who expressed greater levels of IFIT2 (IFIT2 ≥50%). These results demonstrate that IFIT2 depletion activates the aPKC pathway and consequently induces EMT, cell migration and invasion. Most importantly, depleting IFIT2 may participate in OSCC tumor progression, particularly during metastasis. Taken together, our study demonstrates that IFIT2, a protein responsible for interferon stimulation, may prevent OSCC metastasis and serve as a valuable prognostic marker.

Chlorophyllin abrogates canonical Wnt/β-catenin signaling and angiogenesis to inhibit the development of DMBA-induced hamster cheek pouch carcinomas

BACKGROUND

Chlorophyllin, a water soluble semi-synthetic food-grade derivative is reported to exhibit a wide range of beneficial health effects. We investigated the effect of chlorophyllin supplementation on Wnt/β-catenin and vascular endothelial growth factor (VEGF) signaling in the 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis model.

METHODS AND RESULTS

Hamsters were divided into 4 groups. The right buccal pouches of group 1 and 2 hamsters were painted with 0.5 % DMBA for 14 weeks. Group 2 animals received in addition chlorophyllin (4 mg/kg bw) in the diet. Group 3 animals received chlorophyllin alone and group 4 animals served as control. mRNA and protein expression of components of Wnt, VEGF, and PI3K/Akt signaling pathways were analyzed by RT-PCR and Western blot analysis. Dietary chlorophyllin administration suppressed the development of HBP carcinomas by altering the expression of several components of the Wnt/β-catenin signaling pathway. This was associated with inhibition of angiogenesis as evidenced by decreased expression of the proangiogenic factors HIF-1α, VEGF, and VEGFR2. Chlorophyllin administration also downregulated the expression of histone deacetylases involved in epigenetic regulation of tumor angiogenesis.

CONCLUSION

Dietary chlorophyllin that abrogates Wnt/β-catenin and VEGF signaling by targeting a multitude of key signaling molecules is an attractive candidate for preventing tumor progression.

Perifosine enhances mTORC1-targeted cancer therapy by activation of GSK3β in NSCLC cells

mTORC1 inhibitors, including rapamycin and its analogs, have been actively studied both pre-clinically and clinically. However, the single treatment of mTORC1 inhibitors has been modest in most cancer types. We have previously demonstrated that the activation of PI3K/Akt and MEK/ERK signaling pathways attenuates the anticancer efficacy of mTORC1 inhibitors. In this study, we report that mTORC1 inhibition also phosphorylates and inactivates GSK3β, which is a tumor suppressor in lung cancer. Moreover, we show that perifosine, as an Akt inhibitor, decreases rapamycin-induced phosphorylation of GSK3β and elevated p-GSK3β levels in rapamycin-resistant cell lines. Combination of perifosine with mTORC1 inhibitors showed enhanced anticancer efficacy both in cell cultures and in a xenograft mouse model. In addition, perifosine inhibits the growth of both rapamycin sensitive and resistant A549 cells. However, inhibition of GSK3β by a selective inhibitor- LiCl, or downregulation of GSK3β expression by siRNA, reverses the growth inhibitory effects of perifosine on rapamycin resistant cells, suggesting the important role of GSK3β activation in enhancing mTORC1 inhibitors efficacy by perifosine. Thus, our results provide a potential therapeutic strategy to enhance mTORC1-targeted cancer therapy by using perifosine or targeting GSK3β.

The inactive form of glycogen synthase kinase-3β is associated with the development of carcinomas in galectin-3 wild-type mice, but not in galectin-3-deficient mice

Galectin-3 has been implicated in the tumor development via its mediation of the Wnt signaling pathway. Likewise, glycogen synthase kinase-3beta (GSK3β) also plays a role in the Wnt signaling pathway by controlling the levels of cytoplasmic beta-catenin. Altered GSK3β expression has been described in various tumors, but to date, there are no studies evaluating its expression in models of oral carcinogenesis. Additionally, it is unknown whether the absence of galectin-3 regulates the expression of GSK3β. To this end, Gal3-deficient (Gal3(-/-)) and wild-type (Gal3(+/+)) male mice were treated with 4NQO for 16 weeks and sacrificed at week 16 and 32. The tongues were removed, processed, and stained with H&E to detect dysplasias and carcinomas. An immunohistochemical assay was performed to determine the level of P-GSK3β-Ser9 expression in both groups. Carcinomas were more prevalent in Gal3(+/+) than Gal3(-/-) mice (55.5% vs. 28.5%), but no statistical difference was reached. In the dysplasias, the proportion of cells positive for P-GSK3β-Ser9 was slightly higher in Gal3(+/+) than Gal3(-/-) mice (63% vs. 61%). In the carcinomas, a significant difference between Gal3(+/+) and Gal3(-/-) mice was found (74% vs. 59%; p=0.02). P-GSK3β-Ser9-positive cells slightly decreased from the progression of dysplasias to carcinomas in Gal3(-/-) mice (61% vs. 59%; p>0.05). However, a significant increase in P-GSK3β-Ser9 expression was observed from dysplasias to carcinomas in Gal3(+/+) mice (63% vs. 74%; p=0.01). In conclusion, these findings suggest that fully malignant transformation of the tongue epithelium is associated with increased P-GSK3β-Ser9 expression in Gal3(+/+) mice, but not in Gal3(-/-) mice.

Regulation of Neuronal Protein Trafficking and Translocation by SUMOylation

Post-translational modifications of proteins are essential for cell function. Covalent modification by SUMO (small ubiquitin-like modifier) plays a role in multiple cell processes, including transcriptional regulation, DNA damage repair, protein localization and trafficking. Factors affecting protein localization and trafficking are particularly crucial in neurons because of their polarization, morphological complexity and functional specialization. SUMOylation has emerged as a major mediator of intranuclear and nucleo-cytoplasmic translocations of proteins involved in critical pathways such as circadian rhythm, apoptosis and protein degradation. In addition, SUMO-regulated re-localization of extranuclear proteins is required to sustain neuronal excitability and synaptic transmission. Thus, SUMOylation is a key arbiter of neuronal viability and function. Here, we provide an overview of recent advances in our understanding of regulation of neuronal protein localization and translocation by SUMO and highlight exciting areas of ongoing research.

Glycogen synthase kinase-3β, NF-κB signaling, and tumorigenesis of human osteosarcoma

Background

Glycogen synthase kinase-3β (GSK-3β), a serine/threonine protein kinase, may function as a tumor suppressor or an oncogene, depending on the tumor type. We sought to determine the biological function of GSK-3β in osteosarcoma, a rare pediatric cancer for which the identification of new therapeutic targets is urgent.

Methods

We used cell viability assays, colony formation assays, and apoptosis assays to analyze the effects of altered GSK-3β expression in U2OS, MG63, SAOS2, U2OS/MTX300, and ZOS osteosarcoma cell lines. Nude mice (n = 5–8 mice per group) were injected with U2OS/MTX300, and ZOS cells to assess the role of GSK-3β in osteosarcoma growth in vivo and to evaluate the effects of inhibitors and/or anticancer drugs on tumor growth. We used an antibody array, polymerase chain reaction, western blotting, and a luciferase reporter assay to establish the effect of GSK-3β inhibition on the nuclear factor-κB (NF-κB) pathway. Immunochemistry was performed on primary tumor specimens from osteosarcoma patients (n = 74) to determine the relationship of GSK-3β activity with overall survival.

Results

Osteosarcoma cells with low levels of inactive p-Ser9-GSK-3β formed colonies in vitro and tumors in vivo more readily than cells with higher levels and cells in which GSK-3β had been silenced formed fewer colonies and smaller tumors than parental cells. Silencing or pharmacological inhibition of GSK-3β resulted in apoptosis of osteosarcoma cells. Inhibition of GSK-3β resulted in inhibition of the NF-κB pathway and reduction of NF-κB-mediated transcription. Combination treatments with GSK-3β inhibitors, NF-κB inhibitors, and chemotherapy drugs increased the effectiveness of chemotherapy drugs in vitro and in vivo. Patients whose osteosarcoma specimens had hyperactive GSK-3β, and nuclear NF-κB had a shorter median overall survival time (49.2 months) compared with patients whose tumors had inactive GSK-3β and NF-κB (109.2 months).

Conclusion

GSK-3β activity may promote osteosarcoma tumor growth, and therapeutic targeting of the GSK-3β and/or NF-κB pathways may be an effective way to enhance the therapeutic activity of anticancer drugs against osteosarcoma.

Mechanism of β-catenin-mediated transcriptional regulation of epidermal growth factor receptor expression in glycogen synthase kinase 3 β-inactivated prostate cancer cells

Wnt/β-catenin and EGFR pathways are important in cancer development and often aberrantly activated in human cancer. However, it is very important to understand the mechanism responsible for this activation and the relation between them. Here, we report the mechanism of EGFR expression by transcriptionally active β-catenin in GSK3β-inactivated prostate cancer cells that eventually leads to its enhanced proliferation and survival. Expressions of β-catenin and EGFR are elevated in various cancers specifically in prostate cancer cells, DU145. When GSK3β is inactivated in these cells, β-catenin gets stabilized, phosphorylated at Ser-552 by protein kinase A, accumulates in the nucleus, and regulates the expression of its target genes that include EGFR. Chromatin immunoprecipitation (ChIP) and promoter analysis revealed that the EGFR promoter gets occupied by transcriptionally active β-catenin when elevated in GSK3β-inactivated cells. This phenomenon not only leads to increased expression of EGFR but also initiates the activation of its downstream molecules such as ERK1/2 and Stat3, ultimately resulting in up-regulation of multiple genes involved in cell proliferation and survival.

Regulation of glycogen synthase kinase-3 by thymosin beta-4 is associated with gastric cancer cell migration

Thymosin beta-4 (Tβ4), actin-sequestering protein, plays important roles in many cellular functions including cancer cell migrations. Glycogen synthase kinase (GSK) in Wnt signaling pathway is a key molecule to control intercellular interaction. Here, we investigated whether GSK-3 activity is regulated by Tβ4 and it is associated with Tβ4-mediated migration in gastric cancer cells. Various expression level of Tβ4 was observed in human gastric tumor tissues. Migration in gastric cancer cells, SNU638 and SNU668, was dependent on a relative expression level of Tβ4. Cell migration was higher in SNU668 with a higher expression level of Tβ4 than that in SNU638 with a lower Tβ4. Although the level of phosphorylated(p)-GSK-3α (inactive), β-catenin, E-cadherin and E-cadherin:β-catenin complex was relatively higher, p-GSK-3β (inactive) was lower in SNU638 compared to those in SNU668 cells. LiCl, GSK-3α/β inhibitor, reduced lung metastasis of B16F10 mouse melanoma cells and SNU668 cell migration. Small interference (si)RNA of GSK-3α increased SNU638 cell migration in accordance with the reduction of E-cadherin:β-catenin complex formation through a decrease in β-catenin and E-cadherin. Expression level of GSK-3α/β, β-catenin and E-cadherin in SNU668 and SNU638 was reversed by Tβ4-siRNA and by the treatment with acetylated-serine-aspartic acid-lysine-proline (SDKP) tetrapeptide of Tβ4, respectively. E-cadherin expression in SNU638 cells was decreased by β-catenin-siRNA. PD98059, MEK inhibitor, or U0126, ERK inhibitor, reduced SNU668 cell migration accompanying an increase in p-GSK-3α, β-catenin and E-cadherin. Taken together, data indicated that the expression of GSK-3α, β-catenin and E-cadherin could be negatively regulated by Tβ4-induced ERK phosphorylation. It suggests that Tβ4 could be a novel regulator to control Wnt signaling pathways.

Biomarkers of oral premalignant epithelial lesions for clinical application

Oral cancer is the sixth most common form of cancer worldwide, and the majority of cases occur in India and Southeast Asia. Its major risk factors in the western world include smoking and drinking alcohol, whereas in Asia, it is primarily caused by tobacco/areca nut/betel leaf chewing and/or human papillomavirus (HPV) infections. Little is known about this type of cancer despite recent advances in cancer biology. The generally asymptomatic nature of the early oral lesions causes them to remain undetected in many cases. Thus, the disease progresses substantially before the patients seek treatment and is a major contributing factor to the severity of this disease. Therefore, there is a great need to create awareness for its prevention and early diagnosis. The application of advanced molecular biological and biochemical methodologies to elucidate its biomarkers may aid in early detection; however, much more work must be done for this information to be effectively applied in the clinical setting. This review focuses on the need for systematic diagnoses in the early detection of oral cancer using molecular and biochemical approaches, thereby reducing the number of advanced cases in the chewing tobacco-dominated oral cancer population.

Inhibition of heart formation by lithium is an indirect result of the disruption of tissue organization within the embryo

Lithium is a commonly used drug for the treatment of bipolar disorder. At high doses, lithium becomes teratogenic, which is a property that has allowed this agent to serve as a useful tool for dissecting molecular pathways that regulate embryogenesis. This study was designed to examine the impact of lithium on heart formation in the developing frog for insights into the molecular regulation of cardiac specification. Embryos were exposed to lithium at the beginning of gastrulation, which produced severe malformations of the anterior end of the embryo. Although previous reports characterized this deformity as a posteriorized phenotype, histological analysis revealed that the defects were more comprehensive, with disfigurement and disorganization of all interior tissues along the anterior-posterior axis. Emerging tissues were poorly segregated and cavity formation was decreased within the embryo. Lithium exposure also completely ablated formation of the heart and prevented myocardial cell differentiation. Despite the complete absence of cardiac tissue in lithium treated embryos, exposure to lithium did not prevent myocardial differentiation of precardiac dorsal marginal zone explants. Moreover, precardiac tissue freed from the embryo subsequent to lithium treatment at gastrulation gave rise to cardiac tissue, as demonstrated by upregulation of cardiac gene expression, display of sarcomeric proteins, and formation of a contractile phenotype. Together these data indicate that lithium's effect on the developing heart was not due to direct regulation of cardiac differentiation, but an indirect consequence of disrupted tissue organization within the embryo.

The dietary phytochemical 3,3'-diindolylmethane induces G2/M arrest and apoptosis in oral squamous cell carcinoma by modulating Akt-NF-κB, MAPK, and p53 signaling

In light of the growing incidence of oral cancer in Taiwan, this study is aimed at investigating the antitumor activity of 3,3'-diindolylmethane (DIM), an active metabolite of the phytochemical indole-3-carbinol (I3C), in oral squamous cell carcinoma (OSCC). DIM exhibited substantially higher antiproliferative potency than I3C in three OSCC cell lines with IC(50) values in SCC2095, SCC9, and SCC15 cells, respectively, of 22 versus 168μM, 25 versus 176μM, and 29versus 300μM. Flow cytometric analysis and Comet assay indicated that DIM suppressed the viability of SCC2095 cells by inducing apoptosis and G2/M arrest. Western blot analysis of various signaling markers revealed the ability of DIM to target pathways mediated by Akt, mitogen-activated protein (MAP) kinases, nuclear factor (NF)-κB, and p53, of which the concerted action underlined its antitumor efficacy. The concomitant inactivation of Akt and MAP kinases in response to DIM facilitated the dephosphorylation of the proapoptotic protein Bad at Ser-136 and Ser-112, respectively. Through endoplasmic reticulum (ER) stress, DIM stimulated the activation of p53 via Ser-15 phosphorylation, leading to increased expression of the BH3-only proapoptotic Bcl-2 members Puma and Noxa. Together, these changes decreased the mitochondrial threshold for apoptosis. G2/M arrest might be attributable to the suppressive effect of DIM on the expression of cyclin B1 and cdc25c. As many downstream effectors of the Akt-NF-κB pathway, including glycogen synthase kinase 3β, IκB kinase α, and cyclooxygenase-2, have been shown to promote oral tumorigenesis, the ability of DIM to inhibit this signaling axis underscores its chemopreventive potential in oral cancer.

Emerging roles of glycogen synthase kinase 3 in the treatment of brain tumors

The constitutively active protein glycogen synthase kinase 3 (GSK3), a serine/threonine kinase, acts paradoxically as a tumor suppressor in some cancers while potentiates growth in others. Deciphering what governs its actions is vital for understanding many pathological conditions, including brain cancer. What are seemingly disparate roles of GSK3 stems from the complex regulation of many cellular functions by GSK3. This review focuses on the regulation of GSK3, its role in survival, apoptosis and DNA damage, and finally its potential therapeutic impact in brain cancer. A thorough understanding of this versatile protein is critical for improving the outcome of various diseases, especially cancer.

Enzymatic features of the glucose metabolism in tumor cells

Many tumor types exhibit an impaired Pasteur effect, i.e. despite the presence of oxygen, glucose is consumed at an extraordinarily high rate compared with the tissue from which they originate - the so-called 'Warburg effect'. Glucose has to serve as the source for a diverse array of cellular functions, including energy production, synthesis of nucleotides and lipids, membrane synthesis and generation of redox equivalents for antioxidative defense. Tumor cells acquire specific enzyme-regulatory mechanisms to direct the main flux of glucose carbons to those pathways most urgently required under challenging external conditions such as varying substrate availability, presence of anti-cancer drugs or different phases of the cell cycle. In this review we summarize the currently available information on tumor-specific expression, activity and kinetic properties of enzymes involved in the main pathways of glucose metabolism with due regard to the explanation of the regulatory basis and physiological significance of the Warburg effect. We conclude that, besides the expression level of the metabolic enzymes involved in the glucose metabolism of tumor cells, the unique tumor-specific pattern of isozymes and accompanying changes in the metabolic regulation below the translation level enable tumor cells to drain selfishly the blood glucose pool that non-transformed cells use as sparingly as possible.

Deconstructing GSK-3: The Fine Regulation of Its Activity

Glycogen synthase kinase-3 (GSK-3) unique position in modulating the function of a diverse series of proteins in combination with its association with a wide variety of human disorders has attracted significant attention to the protein both as a therapeutic target and as a means to understand the molecular basis of these disorders. GSK-3 is ubiquitously expressed and, unusually, constitutively active in resting, unstimulated cells. In mammals, GSK-3α and β are each expressed widely at both the RNA and protein levels although some tissues show preferential levels of some of the two proteins. Neither gene appears to be acutely regulated at the transcriptional level, whereas the proteins are controlled posttranslationally, largely through protein-protein interactions or by posttranslational regulation. Control of GSK-3 activity thus occurs by complex mechanisms that are each dependent upon specific signalling pathways. Furthermore, GSK-3 appears to be a cellular nexus, integrating several signalling systems, including several second messengers and a wide selection of cellular stimulants. This paper will focus on the different ways to control GSK-3 activity (phosphorylation, protein complex formation, truncation, subcellular localization, etc.), the main signalling pathways involved in its control, and its pathological deregulation.

Insights from studies with oral cleft genes suggest associations between WNT-pathway genes and risk of oral cancer

Oral squamous cell carcinoma (OSCC) accounts for more than 90% of the malignant neoplasms that arise in the mucosa of the upper aerodigestive tract. Recent studies of cleft lip/palate have shown the association of genes involved in cancer. WNT pathway genes have been associated with several types of cancer and recently with cleft lip/palate. To investigate if genes associated with cleft lip/palate were also associated with oral cancer, we genotyped 188 individuals with OSCC and 225 control individuals for markers in AXIN2, AXIN1, GSK3β, WNT3A, WNT5A, WNT8A, WNT11, WNT3, and WNT9B. Statistical analysis was performed with PLINK 1.06 software to test for differences in allele frequencies of each polymorphism between cases and controls. We found association of SNPs in GSK3B (p = 0.0008) and WNT11 (p = 0.03) with OSCC. We also found overtransmission of GSK3B haplotypes in OSCC cases. Expression analyses showed up-regulation of WNT3A, GSK3B, and AXIN1 and down-regulation of WNT11 in OSCC in comparison with control tissues (P < 0.001). Additional studies should focus on the identification of potentially functional variants in these genes as contributors to human clefting and oral cancer.