Protein kinase p-JNK is correlated with the activation of AP-1 and its associated Jun family proteins in hepatocellular carcinoma

Plant bioactive compounds alleviate photoinduced retinal damage and asthenopia: Mechanisms, synergies, and bioavailability

The retina, an important tissue of the eye, is essential in visual transmission and sustaining adequate eyesight. However, oxidative stress and inflammatory reactions can harm retinal structure and function. Recent studies have demonstrated that exposure to light can induce oxidative stress and inflammatory reactions in retinal cells, thereby facilitating the progression of retinal damage-related diseases and asthenopia. Plant bioactive compounds such as anthocyanin, curcumin, resveratrol, lutein, zeaxanthin, epigallocatechin gallate, and quercetin are effective in alleviating retinal damage and asthenopia. Their strong oxidation resistance and unique chemical structure can prevent the retina from producing reactive oxygen species and regulating eye muscle relaxation, thus alleviating retinal damage and asthenopia. Additionally, the combination of these active ingredients produces a stronger antioxidant effect. Consequently, understanding the mechanism of retinal damage caused by light and the regulation mechanism of bioactive compounds can better protect the retina and reduce asthenopia.

KCNN4-mediated Ca2+/MET/AKT axis is promising for targeted therapy of pancreatic ductal adenocarcinoma

As a member of the potassium calcium-activated channel subfamily, increasing evidence suggests that KCNN4 was associated with malignancies. However, the roles and regulatory mechanisms of KCNN4 in PDAC have been little explored. In this work, we demonstrated that the level of KCNN4 in PDAC was abnormally elevated, and the overexpression of KCNN4 was induced by transcription factor AP-1. KCNN4 was closely correlated with unfavorable clinicopathologic characteristics and poor survival. Functionally, we found that overexpression of KCNN4 promoted PDAC cell proliferation, migration and invasion. Conversely, the knockdown of KCNN4 attenuated the growth and motility of PDAC cells. In addition to these, knockdown of KCNN4 promoted PDAC cell apoptosis and led to cell cycle arrest in the S phase. In mechanistic investigations, RNA-sequence revealed that the MET-mediated AKT axis was essential for KCNN4, encouraging PDAC cell proliferation and migration. Collectively, these findings reveal a function of KCNN4 in PDAC and suggest it's an attractive therapeutic target and tumor marker. Our studies underscore a better understanding of the biological mechanism of KCNN4 in PDAC and suggest novel strategies for cancer therapy.

A saturated fatty acid-rich diet enhances hepatic lipogenesis and tumorigenesis in HCV core gene transgenic mice

Previous studies suggested that high consumption of saturated fatty acid (SFA) is a risk factor for liver cancer. However, it remains unclear how dietary SFA affects liver tumorigenesis. This study aimed to investigate the impact of a SFA-rich diet on hepatic tumorigenesis using hepatitis C virus core gene transgenic (HCVcpTg) mice that spontaneously developed hepatic steatosis and tumors with aging. Male HCVcpTg mice were treated for 15 months with a purified control diet or SFA-rich diet prepared by replacing soybean oil in the control diet with hydrogenated coconut oil, and phenotypic changes were assessed. In this special diet, almost all dietary fatty acids were SFA. Long-term feeding of SFA-rich diet to HCVcpTg mice increased hepatic steatosis, liver dysfunction, and the prevalence of liver tumors, likely due to stimulation of de novo lipogenesis, activation of the pro-inflammatory and pro-oncogenic transcription factor nuclear factor-kappa B (NF-κB), enhanced c-Jun N-terminal kinase/activator protein 1 (JNK/AP-1) signaling and induction of the oncogenes cyclin D1 and p62/sequestosome 1. The SFA-rich diet did not affect liver fibrosis or autophagy. Collectively, long-term SFA-rich diet consumption promoted hepatic tumorigenesis mainly through activation of lipogenesis, NF-κB, and JNK/AP-1 signaling. We therefore propose that HCV-infected patients should avoid excessive intake of SFA-rich foods to prevent liver cancer.

Systematic Elucidation of the Potential Mechanisms of Core Chinese Materia Medicas in Treating Liver Cancer Based on Network Pharmacology

Objective

In this study, the data mining method was used to screen the core Chinese materia medicas (CCMMs) against primary liver cancer (PLC), and the potential mechanisms of CCMMs in treating PLC were analyzed based on network pharmacology.

Methods

Traditional Chinese medicine (TCM) prescriptions for treating PLC were obtained from a famous TCM doctor in Shenzhen, China. According to the data mining technique, the TCM Inheritance Support System (TCMISS) was applied to excavate the CCMMs in the prescriptions. Then, bioactive ingredients and corresponding targets of CCMMs were collected using three different TCM online databases, and target genes of PLC were obtained from GeneCards and OMIM. Afterwards, common targets of CCMMs and PLC were screened. Furthermore, a network of CCMMs bioactive ingredients and common target gene was constructed by Cytoscape 3.7.1, and gene ontology (GO) and signaling pathways analyses were performed to explain the mechanism of CCMMs in treating PLC. Besides, protein-protein interaction (PPI) analysis was used to identify key target genes of CCMMs, and the prognostic value of key target genes was verified using survival analysis.

Results

A total of 15 high-frequency Chinese materia medica combinations were found, and CCMMs (including Paeoniae Radix Alba, Radix Bupleuri, Macrocephalae Rhizoma, Coicis Semen, Poria, and Curcumae Radix) were identified by TCMISS. A total of 40 bioactive ingredients (e.g., quercetin, kaempferol, and naringenin) of CCMMs were obtained, and 202 common target genes of CCMMs and PLC were screened. GO analysis indicated that biological processes of CCMMs were mainly involved in response to drug, response to ethanol, etc. Pathway analysis demonstrated that CCMMs exerted its antitumor effects by acting on multiple signaling pathways, including PI3K-Akt, TNF, and MAPK pathways. Also, some key target genes of CCMMs were determined by PPI analysis, and four genes (MAPK3, VEGFA, EGF, and EGFR) were found to be correlated with survival in PLC patients.

Conclusion

Based on data mining and network pharmacology methods, our results showed that the therapeutic effect of CCMMs on PLC may be realized by acting on multitargets and multipathways related to the occurrence and development of PLC.

Upregulation of SMYD3 and SMYD3 VNTR 3/3 polymorphism increase the risk of hepatocellular carcinoma

SMYD3 (SET and MYND domain-containing protein 3) is involved in histone modification, which initiates oncogenesis by activating transcription of multiple downstream genes. To investigate associations of variable numbers of tandem repeats (VNTR) variants in the SMYD3 gene promoter, SMYD3 serum levels and SMYD3 mRNA expression in hepatitis B virus (HBV) infection and clinical progression of related liver disease. SMYD3 VNTRs were genotyped in 756 HBV patients and 297 healthy controls. SMYD3 serum levels were measured in 293 patients and SMYD3 mRNA expression was quantified in 48 pairs of hepatocellular tumor and adjacent non-tumor liver tissues. Genotype SYMD3 VNTR 3/3 was more frequent among HCC patients than in controls (P_adjusted = 0.037). SMYD3 serum levels increased according to clinical progression of liver diseases (P = 0.01); HCC patients had higher levels than non-HCC patients (P = 0.04). Among patients with SMYD3 VNTR 3/3, HCC patients had higher SMYD3 levels than others (P < 0.05). SMYD3 mRNA expression was up-regulated in HCC tumor tissues compared to other tissues (P = 0.008). In conclusion, upregulation of SMYD3 correlates with the occurrence of HCC and SMYD3 VNTR 3/3 appears to increase the risk of HCC through increasing SMYD3 levels. SMYD3 may be an indicator for HCC development in HBV patients.

Activator protein‑1 is a novel regulator of mesencephalic astrocyte‑derived neurotrophic factor transcription

Mesencephalic astrocyte‑derived neurotrophic factor (MANF) is an endoplasmic reticulum stress‑inducible protein, which has been suggested to be upregulated in inflammatory diseases; however, how inflammation regulates its transcription remains unclear. Activator protein‑1 (AP‑1), which is a transcription factor complex composed of c‑Fos and c‑Jun, is activated during the inflammatory process. The present study aimed to investigate whether the AP‑1 complex regulates MANF transcription. The results of a luciferase reporter assay revealed that one of three putative AP‑1 binding sites in the MANF promoter region is essential for enhancement of MANF transcription. Mechanistically, AP‑1 was revealed to directly bind to the promoter region of the MANF gene by chromatin immunoprecipitation assay. Furthermore, MANF was strongly expressed in the liver tissues of patients with hepatitis B virus (HBV) infection, compared with in normal liver tissues from patients with hepatic hemangioma. Furthermore, c‑Fos and c‑Jun were also upregulated in the nuclei of hepatocytes from patients with HBV infection. In mice treated with carbon tetrachloride, the expression patterns of MANF, c‑Fos and c‑Jun were similar to those in patients with HBV. These results suggested that the AP‑1 complex may be a novel regulator of MANF transcription, which may be involved in liver inflammation and fibrosis.

Role of C-Jun N-terminal Kinase in Hepatocellular Carcinoma Development

Hepatocellular carcinoma (HCC) is among the most frequently occurring cancers and the leading causes of cancer mortality worldwide. Identification of the signaling pathways regulating liver carcinogenesis is critical for developing novel chemoprevention and targeted therapies. C-Jun N-terminal kinase (JNK) is a member of a larger group of serine/threonine (Ser/Thr) protein kinases known as the mitogen-activated protein kinase (MAPK) family. JNK is an important signaling component that converts external stimuli into a wide range of cellular responses, including cell proliferation, differentiation, survival, migration, invasion, and apoptosis, as well as the development of inflammation, fibrosis, cancer growth, and metabolic diseases. Because of the essential roles of JNK in these cellular functions, deregulated JNK is often found to contribute to the development of HCC. Recently, the functions and molecular mechanisms of JNK in HCC development have been addressed using mouse models and human HCC cell lines. Furthermore, recent studies demonstrate that the activation of JNK by oncogenes can promote the development of cancers by regulating the transforming growth factor (TGF)-β/Smad pathway, which makes the oncogenes/JNK/Smad signaling pathway an attractive target for cancer therapy. Additionally, JNK-targeted therapy has a broad potential for clinical applications. In summary, we are convinced that promising new avenues for the treatment of HCC by targeting JNK are on the horizon, which will undoubtedly lead to better, more effective, and faster therapies in the years to come.

Overexpression of c-Jun contributes to sorafenib resistance in human hepatoma cell lines

Background

Despite recent advances in treatment strategies, it is still difficult to cure patients with hepatocellular carcinoma (HCC). Sorafenib is the only approved multiple kinase inhibitor for systemic chemotherapy in patients with advanced HCC. The majority of advanced HCC patients are resistant to sorafenib. The mechanisms of sorafenib resistance are still unknown.

Methods

The expression of molecules involved in the mitogen-activated protein kinase (MAPK) signaling pathway in human hepatoma cell lines was examined in the presence or absence of sorafenib. Apoptosis of human hepatoma cells treated with sorafenib was investigated, and the expression of Jun proto-oncogene (c-Jun) was measured.

Results

The expression and phosphorylation of c-Jun were enhanced in human hepatoma cell lines after treatment with sorafenib. Inhibiting c-Jun enhanced sorafenib-induced apoptosis. The overexpression of c-Jun impaired sorafenib-induced apoptosis. The expression of osteopontin, one of the established AP-1 target genes, was enhanced after treatment with sorafenib in human hepatoma cell lines.

Conclusions

The protein c-Jun plays a role in sorafenib resistance in human hepatoma cell lines. The modulation and phosphorylation of c-Jun could be a new therapeutic option for enhancing responsiveness to sorafenib. Modulating c-Jun may be useful for certain HCC patients with sorafenib resistance.

Interaction of the hepatitis B virus X protein with the lysine methyltransferase SET and MYND domain-containing 3 induces activator protein 1 activation

Hepatitis B virus (HBV) is a widespread human pathogen that often causes chronic hepatitis, liver cirrhosis and hepatocellular carcinoma. The detailed mechanisms underlying HBV pathogenesis remain poorly understood. The HBV X protein (HBx) is a multifunctional regulator that modulates viral replication and host cell functions, such as cell cycle progression, apoptosis and protein degradation through interaction with a variety of host factors. Recently, the nonstructural protein 5A (NS5A) of hepatitis C virus has been reported to interact with methyltransferase SET and MYND domain-containing 3 (SMYD3), which is implicated in chromatin modification and development of cancer. Because HBx shares fundamental regulatory functions concerning viral replication and pathogenesis with NS5A, it was decided to examine whether HBx interacts with SMYD3. In the present study, it was demonstrated by co-immunoprecipitation analysis that HBx interacts with both ectopically and endogenously expressed SMYD3 in Huh-7.5 cells. Deletion mutation analysis revealed that the C-terminal region of HBx (amino acids [aa] 131-154) and an internal region of SMYD3 (aa 269-288) are responsible for their interaction. Immunofluorescence and proximity ligation assays showed that HBx and SMYD3 co-localize predominantly in the cytoplasm. Luciferase reporter assay demonstrated that the interaction between HBx and SMYD3 activates activator protein 1 (AP-1) signaling, but not that of nuclear factor-kappa B (NF-κB). On the other hand, neither overexpression nor knockdown of SMYD3 altered production of HBV transcripts and HBV surface antigen (HBsAg). In conclusion, a novel HBx-interacting protein, SMYD3, was identified, leading to proposal of a novel mechanism of AP-1 activation in HBV-infected cells.

Systematic Analysis of Quantitative Logic Model Ensembles Predicts Drug Combination Effects on Cell Signaling Networks

A major challenge in developing anticancer therapies is determining the efficacies of drugs and their combinations in physiologically relevant microenvironments. We describe here our application of "constrained fuzzy logic" (CFL) ensemble modeling of the intracellular signaling network for predicting inhibitor treatments that reduce the phospho-levels of key transcription factors downstream of growth factors and inflammatory cytokines representative of hepatocellular carcinoma (HCC) microenvironments. We observed that the CFL models successfully predicted the effects of several kinase inhibitor combinations. Furthermore, the ensemble predictions revealed ambiguous predictions that could be traced to a specific structural feature of these models, which we resolved with dedicated experiments, finding that IL-1α activates downstream signals through TAK1 and not MEKK1 in HepG2 cells. We conclude that CFL-Q2LM (Querying Quantitative Logic Models) is a promising approach for predicting effective anticancer drug combinations in cancer-relevant microenvironments.

Metformin and AICAR regulate NANOG expression via the JNK pathway in HepG2 cells independently of AMPK

NANOG, a marker of stemness, impacts tumor progression and therapeutic resistance in cancer cells. In human hepatocellular carcinoma (HCC), upregulation of NANOG is associated with metastasis and a low survival rate, while its downregulation results in a lower colony formation rate and enhanced chemosensitivity. Metformin, an agent widely used for diabetes treatment, and AICAR, another AMP-activated protein kinase (AMPK) activator, have been reported to inhibit the growth of several types of cancer. Although inhibitory effects of metformin on NANOG in pancreatic cancer cells and of AICAR in mouse embryonic stem cells have been described, the underlying molecular mechanisms remain uncertain in HCC. In this study, we used the HepG2 cell line and found that metformin/AICAR downregulated NANOG expression with decreased cell viability and enhanced chemosensitivity to 5-fluorouracil (5-FU). Moreover, metformin/AICAR inhibited c-Jun N-terminal kinase (JNK) activity, and blockade of either the JNK MAPK pathway or knockdown of JNK1 gene expression reduced NANOG levels. The upregulation of NANOG and phospho-JNK by basic fibroblast growth factor (bFGF) was abrogated by metformin/AICAR. Additionally, although transient upregulation of NANOG within 2 h of treatment with metformin/AICAR was concordant with both JNK and AMPK activation, increased NANOG expression with activation of JNK was also observed following AMPK inhibition with compound C. Taken together, our data suggest that metformin/AICAR regulate NANOG expression via the JNK MAPK pathway in HepG2 cells independently of AMPK, and that this JNK/NANOG signaling pathway may offer new therapeutic strategies for the treatment of HCC.

The transcription factor c-JUN/AP-1 promotes HBV-related liver tumorigenesis in mice

Hepatocellular carcinoma (HCC) develops as a consequence of chronic inflammatory liver diseases such as chronic hepatitis B virus (HBV) infection. The transcription factor c-Jun/activator protein 1 (AP-1) is strongly expressed in response to inflammatory stimuli, promotes hepatocyte survival during acute hepatitis and acts as an oncogene during chemically induced liver carcinogenesis in mice. Here, we therefore aimed to characterize the functions of c-Jun during HBV-related liver tumorigenesis. To this end, transgenic mice expressing all HBV envelope proteins (HBV(+)), an established model of HBV-related HCC, were crossed with knockout mice lacking c-Jun specifically in hepatocytes and tumorigenesis was analyzed. Hepatic expression of c-Jun was strongly induced at several time points during tumorigenesis in HBV(+) mice, whereas expression of other AP-1 components remained unchanged. Importantly, formation of premalignant foci and tumors was strongly reduced in HBV(+) mice lacking c-Jun. This phenotype correlated with impaired hepatocyte proliferation and increased expression of the cell cycle inhibitor p21, whereas hepatocyte survival was not affected. Progression and prognosis of HBV-related HCC correlates with the expression of the cytokine osteopontin (Opn), an established AP-1 target gene. Opn expression was strongly reduced in HBV(+) livers and primary mouse hepatocytes lacking c-Jun, demonstrating that c-Jun regulates hepatic Opn expression in a cell-autonomous manner. These findings indicate that c-Jun has important functions during HBV-associated tumorigenesis by promoting hepatocyte proliferation as well as progression of dysplasia. Therefore, targeting c-Jun may be a useful strategy to prevent hepatitis-associated tumorigenesis.

Metformin inhibits the invasion of human hepatocellular carcinoma cells and enhances the chemosensitivity to sorafenib through a downregulation of the ERK/JNK-mediated NF-κB-dependent pathway that reduces uPA and MMP-9 expression

Metformin has been shown to exert anti-cancer activities in several cancer cells and animal models. However, the molecular mechanisms of its anti-metastatic activities remain poorly understood and warrant further investigation. The aims of this study were to evaluate the ability of metformin to inhibit the migration and invasion of hepatocellular carcinoma (HCC) cells and identify its effects on signaling pathways. Our data indicate that metformin inhibits the migration and invasion of human HCC cells. Metformin was also found to significantly inhibit the expression and secretion of MMP-9 and uPA in HCC cells, and suppress the phosphorylation of ERK1/2 and JNK1/2. Treatment with an ERK1/2 inhibitor (PD98059) or JNK1/2 inhibitor (SP600125) enhanced the inhibitory effects of metformin on the migration and invasion of HCC cells. Moreover, metformin-induced inhibition of MMP-9 and uPA promoter activity also blocked the nuclear translocation of NF-κB and its binding to the MMP-9 and uPA promoters, and these suppressive effects were further enhanced by PD98059 or SP600125. Moreover, metformin markedly enhanced the anti-metastatic effects of sorafenib. In conclusion, metformin inhibits the migration and invasion of HCC cells by suppressing the ERK/JNK-mediated NF-κB-dependent pathway, and thereby reducing uPA and MMP-9 expression. Additionally, combination treatment with metformin and sorafenib yielded synergistic inhibitory effects in suppressing cell migration and invasion of HCC cells. These findings provide insight into the molecular mechanisms involved in the anti-metastatic effects of metformin, as well as its ability to enhance the chemosensitivity of HCC cells to sorafenib.

Beta-like importins mediate the nuclear translocation of mitogen-activated protein kinases

The rapid nuclear translocation of signaling proteins upon stimulation is important for the regulation of de novo gene expression. We have studied the stimulated nuclear shuttling of c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinases (MAPKs) and found that they translocate into the nucleus in a Ran-dependent, but NLS- or NTS-independent, manner, unrelated to their catalytic activity. We show that this translocation involves three β-like importins, importins 3, 7, and 9 (Imp3/7/9). Knockdown of these importins inhibits the nuclear translocation of the MAPKs and, thereby, activation of their transcription factor targets. We further demonstrate that the translocation requires the stimulated formation of heterotrimers composed of Imp3/Imp7/MAPK or Imp3/Imp9/MAPK. JNK1/2 and p38α/β bind to either Imp7 or Imp9 upon stimulated posttranslational modification of the two Imps, while Imp3 joins the complex after its stimulation-induced phosphorylation. Once formed, these heterotrimers move to the nuclear envelope, where importin 3 remains, while importins 7 and 9 escort the MAPKs into the nucleus. These results suggest that β-like importins are central mediators of stimulated nuclear translocation of signaling proteins and therefore add a central level of regulation to stimulated transcription.

S100A9 promotes the proliferation and invasion of HepG2 hepatocellular carcinoma cells via the activation of the MAPK signaling pathway

The S100A9 protein, a member of the S100 protein family, is often upregulated in various types of cancer, including hepatocellular carcinoma (HCC). S100A9 acts as a danger signal when secreted to the extracellular space and is thought to play an important role during tumorigenesis. Despite this fact, little is known about the effects of S100A9 in the tumor microenvironment on HCC. Therefore, in this study, we investigated the effects of exogenous S100A9 on the proliferation and invasion of HepG2 HCC cells, as well as the molecular mechanisms underlying these effects. Our results demonstrated that exogenous S100A9 promoted the proliferation, clone formation and invasion of HepG2 cells in vitro, as shown by 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltrazolium bromide (MTT), clone formation and transwell invasion assays, respectively, and also promoted tumor growth in vivo by tumorigenicity assays in nude mice. Furthermore, S100A9 increased the phosphorylation of p38 and ERK1/2 mitogen-activated protein kinases (MAPKs) in HepG2 cells. When the phosphorylation of p38 was inhibited by SB203580 (a p38 inhibitor), the S100A9-induced cell invasion was reversed; when the phosphorylation of ERK1/2 was inhibited by PD98059 (an ERK1/2 inhibitor), the S100A9-induced cell proliferation was reversed. These data suggest that the S100A9-induced proliferation and invasion of HepG2 cells are partly mediated by the activation of the MAPK signaling pathway.

C-terminal truncated hepatitis B virus x protein is associated with metastasis and enhances invasiveness by C-Jun/matrix metalloproteinase protein 10 activation in hepatocellular carcinoma

Random integration of hepatitis B virus (HBV) DNA into the host genome is frequent in human hepatocellular carcinoma (HCC) and this leads to truncation of the HBV DNA, particularly at the C-terminal end of the HBV X protein (HBx). In this study, we investigated the frequency of this natural C-terminal truncation of HBx in human HCCs and its functional significance. In 50 HBV-positive patients with HCC, full-length HBx was detected in all nontumorous livers. However, full-length HBx was found in only 27 (54%) of the HCC tumors, whereas natural carboxylic acid (COOH)-truncated HBx was found in the remaining 23 (46%) tumors. Upon clinicopathological analysis, the presence of natural COOH-truncated HBx significantly correlated with the presence of venous invasion, a hallmark of metastasis (P = 0.005). Inducible stable expression of the COOH-truncated HBx protein (with 24 amino acids truncated at the C-terminal end) enhanced the cell-invasive ability of HepG2 cells, as compared to full-length HBx, using the Matrigel cell-invasion assay. It also resulted in increased C-Jun transcriptional activity and enhanced transcription of matrix metalloproteinase 10 (MMP10), whereas activation of the MMP10 promoter by COOH-truncated HBx was abolished when the activator protein 1-binding sites on the MMP10 promoter were mutated. Furthermore, silencing of MMP10 by short interfering RNA in HBxΔC1-expressing HepG2 cells resulted in significant reduction of cell invasiveness.

CONCLUSIONS

Our data suggest that COOH truncation of HBx, particularly with 24 amino acids truncated at the C-terminal end, plays a role in enhancing cell invasiveness and metastasis in HCC by activating MMP10 through C-Jun.

c-Jun N-terminal kinase activation by oxidative stress suppresses retinoid signaling through proteasomal degradation of retinoic acid receptor α protein in hepatic cells

We previously reported that impaired retinoid signaling causes hepatocellular carcinoma (HCC) through oxidative stress. However, the interaction between oxidative stress and retinoid signaling has not been fully understood. To address this issue, the effects of hydrogen peroxide on the transcriptional activity of RAR/RXR heterodimers, RARα and RXRα proteins and intracellular signaling pathways were examined. The transcriptional activity of RAR/RXR examined by the DR5-tk-Luc reporter assay was significantly suppressed. The RARα protein level began to decrease at 6 h after treatment and declined thereafter. However, RARα mRNA were not changed. Activation of extracellular regulated kinases (ERK), p38, c-Jun N-terminal kinase (JNK) and Akt was observed after treatment of hydrogen peroxide. SP600125, an inhibitor of JNK, reversed the RARα protein level reduced by hydrogen peroxide. Anisomycin, an activator of JNK, reduced RARα protein. Transfection of wild-type JNK-constitutive actively expressing plasmid, but not kinase-negative JNK-expressing plasmid caused reduction of RARα protein. Proteasomal degradation of RARα was observed after anisomycin treatment; however, the mutant RARα, of which phosphorylation sites are replaced with alanines, was not degradated. In hepatitis C virus (HCV)-related human liver tissues, phospho-JNK and RARα reciprocally expressed with the progression of liver disease. Finally, the staining of 8-OHdG and thioredoxin was increased with the disease progression. These data indicate that JNK activation by oxidative stress suppresses retinoid signaling through proteasomal degradation of RARα, suggesting that a vicious cycle between aberrant retinoid signaling and oxidative stress accelerates hepatocarcinogenesis.

Defective anchoring of JNK1 in the cytoplasm by MKK7 in Jurkat cells is associated with resistance to Fas-mediated apoptosis

The c-Jun N-terminal protein kinase (JNK) plays a context-dependent role in tumorigenesis. Stress-induced redistribution of JNK from the cytoplasm to the nucleus has been demonstrated as essential for stress-induced cell death. However, accumulation of basal JNK activity in the nucleus has frequently been seen in tumor cells. Our previous report revealed aberrant nuclear entry of JNK protein in Jurkat human leukemic T-cells even without JNK hyperactivation. Because inhibition of JNK activity, especially JNK1 activity, in Jurkat cells results in augmented Fas-mediated apoptosis, it is possible that aberrant subcellular localization of JNK, especially the JNK1 isoform, contributes to the resistance to Fas-mediated apoptosis. Here we report that MKK7 works as a cytoplasmic anchoring protein for JNK1 in various types of cells, including human peripheral blood mononuclear cell (PBMC) T-cells, but exhibits aberrant nuclear entry in Jurkat cells. Ectopic expression of a JNK1 mutant defective of nuclear entry or a nuclear JNK inhibitor leads to impaired UV-induced apoptosis in both PBMC T- and Jurkat cells. The same treatment shows no effect on Fas-mediated apoptosis of PBMC T-cells but sensitizes Jurkat cells to Fas-mediated apoptosis. Taken together, our work suggests that aberrant subcellular organization of the JNK pathway might render certain tumor cells resistant to Fas-mediated apoptosis.

Inhibition of JNK1 expression decreases migration and invasion of mouse hepatocellular carcinoma cell line in vitro

c-Jun N-terminal kinase (JNK) is located in focal adhesion plaque (FAP). JNK is necessary to growth, morphogenesis, and differentiation of cells; especially JNK1 has a close relation with tumors. In this study, we silenced JNK1 by using short hairpin RNA (shRNA) and examined the effect on migration and invasion of mouse hepatocellular carcinoma (HCC) cell line Hca-F in vitro. Three shRNA expression vectors (JNK1shRNA-1, JNK1shRNA-2, and JNK1shRNA-3) were constructed and transfected to Hca-F cells stably. The most effective shRNA was selected by detecting the expression levels of mRNA and protein. Transwell assay was performed to detect the ability of migration and invasion of cells. A negative control sequence (JNK1shRNA control) and non-transfected normal Hca-F cells were treated as control groups. The "Results" showed that the expression vectors of pSilencer-JNK1shRNA were constructed and transfected to Hca-F cells successfully. The most effective shRNA was JNK1shRNA-2. The expressions of mRNA and protein of JNK1 in Hca-F cells after transfection of JNK1shRNA-2 were decreased significantly compared with the other groups (all, P<0.01; all, P<0.05). The ability of migration and invasion was decreased after down-regulation of JNK1 expression (all, P<0.05). These results suggest that the inhibition of JNK1 expression can decrease ability of migration and invasion of mouse hepatocellular carcinoma cell line in vitro. JNK1 plays an important role in lymphatic metastasis of HCC. It may be a new target for gene therapy of lymphatic metastasis of HCC.

Basal c-Jun NH2-terminal protein kinase activity is essential for survival and proliferation of T-cell acute lymphoblastic leukemia cells

Hyperactivation of c-Jun NH2-terminal protein kinase (JNK) has been found in various malignant lymphocytes and inhibition of JNK activity leads to cell cycle arrest and apoptosis. However, the role of JNK activity in the oncogenic growth of T-cell acute lymphoblastic leukemia (T-ALL) cells remains largely unknown. Here, we report that treatment of T-ALL cells with JNK inhibitors led to cell cycle arrest and apoptosis and increased sensitivity to Fas-mediated apoptosis, whereas weak ectopic expression of MKK7-JNK1 fusion protein, which shows constitutive JNK activity, in T-ALL cells resulted in accelerated cell cycle progression and resistance to Fas-mediated apoptosis. The protein levels of c-Myc and Bcl-2 were reduced in the presence of JNK inhibitors but were enhanced with MKK7-JNK1. Small interfering RNA against JNK1, but not JNK2, exhibited similar effects to JNK inhibitors. These findings suggest that targeting JNK, especially JNK1 isoform, may have some important therapeutic implications in the treatment of T-ALL. Further exploration revealed that JNK protein and basal JNK activity in T-ALL cells showed aberrant subcellular localization, but no hyperactivation of JNK was observed. Thus, our work suggests that there might be novel mechanism(s) other than hyperactivation underlying the protumorigenic role of JNK activity.

JNK1, a potential therapeutic target for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the third leading cause of cancer death worldwide. Despite tremendous efforts to diagnose and institute new treatment regimens, the prognosis is still extremely poor. Therefore, knowledge of the molecular mechanisms governing the initiation, maintenance and progression of HCC is urgently needed. Recently, several groups have attributed an important role for c-Jun N-terminal kinase 1 (JNK1) in the pathogenesis of human HCC and its close association with the expression of HCC signature genes. In this review the various associations between JNK1 and HCC are discussed with the hope that targeting this pivotal kinase may lead to novel therapeutic approaches for this fatal disease.

Common dysregulation of Wnt/Frizzled receptor elements in human hepatocellular carcinoma

Dysregulation of growth factors and their receptors is central to human hepatocellular carcinoma (HCC). We previously demonstrated that the Frizzled-7 membrane receptor mediating the Wnt signalling can activate the beta-catenin pathway and promotes malignancy in human hepatitis B virus-related HCCs. Expression patterns of all the 10 Frizzled receptors, and their extracellular soluble autoparacrine regulators (19 Wnt activators and 4 sFRP inhibitors) were assessed by real-time RT-PCR in 62 human HCC of different etiologies and their matched peritumorous areas. Immunostaining was performed to localise Frizzled on cell types in liver tissues. Regulation of three known Frizzled-dependent pathways (beta-catenin, protein kinase C, and C-Jun NH(2)-terminal kinase) was measured in tissues by western blot. We found that eight Frizzled-potentially activating events were pleiotropically dysregulated in 95% HCC and 68% peritumours as compared to normal livers (upregulations of Frizzled-3/6/7 and Wnt3/4/5a, or downregulation of sFRP1/5), accumulating gradually with severity of fibrosis in peritumours and loss of differentiation status in tumours. The hepatocytes supported the Wnt/Frizzled signalling since specifically overexpressing Frizzled receptors in liver tissues. Dysregulation of the eight Frizzled-potentially activating events was associated with differential activation of the three known Frizzled-dependent pathways. This study provides an extensive analysis of the Wnt/Frizzled receptor elements and reveals that the dysregulation may be one of the most common and earliest events described thus far during hepatocarcinogenesis.

A phase I/II trial of TAC-101, an oral synthetic retinoid, in patients with advanced hepatocellular carcinoma

PURPOSE

Preclinical models showed TAC-101 (4-[3,5-bis(trimethylsilyl) benzamide] benzoic acid), an oral synthetic retinoid, has anti-tumor activity in hepatocellular carcinoma (HCC). A phase I/II study was performed in advanced HCC patients (pts).

PATIENTS AND METHODS

Thirty-three patients were enrolled. During Phase I, pts received 40 mg daily for 14 days q3 weeks; 2 of 5 patients developed DLT so dose was reduced to 20 mg/day. Twenty-eight patients received 20 mg/day.

RESULTS

No pt had a CR or PR, but 12 of 21 (57%) had SD. Two pts (9.5%) had late PR after discontinuing TAC-101. Median survival (MS) for all 28 pts treated with 20 mg/day was 12.7 months (95% CI 8.8-22.7); MS for 21 evaluable pts was 19.2 months (95% CI 10.4-27.6).

CONCLUSIONS

20 mg of TAC- was well tolerated. Significant disease stabilization (12/21 pts, 57%), 2 late PRs, and prolonged MS (19.2 months) suggest that TAC-101 provides meaningful patient benefit.

Effect of Qi-protecting powder (Huqi San) on expression of c-jun, c-fos and c-myc in diethylnitrosamine-mediated hepatocarcinogenesis

AIM: To study the inhibitory effect of Huqi San (Qi-protecting powder) on rat prehepatocarcinoma induced by diethylinitrosamine (DEN) by analyzing the mutational activation of c-fos proto-oncogene and over-expression of c-jun and c-myc oncogenes.

METHODS: A Solt-Farber two-step test model of prehepatocarcinoma was induced in rats by DEN and 2-acetylaminofluorene (AAF) to investigate the modifying effects of Huqi San on the expression of c-jun, c-fos and c-myc in DEN-mediated hepatocarcinogenesis. Huqi San was made of eight medicinal herbs containing glycoprival granules, in which each milliliter contains 0.38 g crude drugs. γ-glutamy-transpeptidase-isoenzyme (γ-GTase) was determined with histochemical methods. Level of 8-hydroxydeoxyguanosine (OHdG) formed in liver and c-jun, c-fos and c-myc proto-oncogenes were detected by immunohistochemical methods.

RESULTS: The level of 8-OHdG, a mark of oxidative DNA damage, was significantly decreased in the liver of rats with prehepatocarcinoma induced by DEN who received 8 g/kg body weight or 4 g/kg body weight Huqi San before (1 wk) and after DEN exposure (4 wk). Huqi San-treated rats showed a significant decrease in number of γ-GT positive foci (P < 0.001, prevention group: 4.96 ± 0.72 vs 29.46 ± 2.17; large dose therapeutic group: 7.53 ± 0.88 vs 29.46 ± 2.17). On the other hand, significant changes in expression of c-jun, c-fos and c-myc were found in Huqi San-treated rats.

CONCLUSION: Activation of c-jun, c-fos and c-myc plays a crucial role in the pathogenesis of liver cancer. Huqi San can inhibit the over-expression of c-jun, c-fos and c-myc oncogenes and liver preneolastic lesions induced by DEN.

Activation of c-jun N-terminal kinase is associated with cell proliferation and shorter relapse-free period in superficial spreading malignant melanoma

Signaling pathways regulating cell proliferation and survival have become attractive targets for anticancer strategies. In the present study, we analyzed by immunohistochemistry, a panel of benign nevi, superficial spreading and nodular primary melanomas and metastases for expression of activated p38/mitogen-activated protein kinase (p-p38) and c-jun N-terminal kinase (JNK) (p-JNK) and correlated the findings with known prognostic variables. Twenty-five and 35% of the primaries and 9 and 25% of the metastases expressed variable levels of p-p38 and p-JNK, respectively. In benign nevi, 73.5% expressed p-JNK and 7% expressed p-p38. For patients with superficial spreading melanomas, high level of cytoplasmic p-JNK was associated with thicker tumors (P=0.017) and shorter disease-free survival (P=0.003) as well as with markers of cell proliferation (cyclin A (P=0.017) and p21 (P=0.021)). In nodular melanomas, nuclear p-p38 was associated with Ki-67 (P=0.012), but neither cytoplasmic nor nuclear localized p-p38 was associated with disease outcome. Of note, in superficial spreading melanomas, a positive correlation between cytoplasmic p-JNK and cytoplasmic p-extracellular signal-regulated kinase ERK(1/2) (P=0.005) and p-p38 (P=0.003) was observed. Likewise, p-p38 in cytoplasm was positively associated with cytoplasmic p-ERK1/2 (P<0.0005) and p-Akt (P=0.047). In contrast, except for a positive correlation between nuclear p-p38 and membranous p-TrkA (P=0.02), no correlation between the activation status of the different signaling pathways was observed in nodular melanomas. In conclusion, our results suggest that in benign nevi activated JNK may have a role in restricting uncontrolled cell proliferation or survival. However, during tumor progression, activation of JNK is associated with cell proliferation and shorter relapse-free period for patients with superficial spreading melanomas, suggesting that the JNK activation status could be a marker for clinical outcome in at least a subgroup of malignant melanoma. In contrast, activation of p38 seems to play a less important role in development and progression of malignant melanomas.