Role of transforming growth factor-beta1-smad signal transduction pathway in patients with hepatocellular carcinoma

Dual Roles of the Activin Signaling Pathway in Pancreatic Cancer

Activin, a member of the TGF-β superfamily, is involved in many physiological processes, such as embryonic development and follicle development, as well as in multiple human diseases including cancer. Genetic mutations in the activin signaling pathway have been reported in many cancer types, indicating that activin signaling plays a critical role in tumorigenesis. Recent evidence reveals that activin signaling may function as a tumor-suppressor in tumor initiation, and a promoter in the later progression and metastasis of tumors. This article reviews many aspects of activin, including the signaling cascade of activin, activin-related proteins, and its role in tumorigenesis, particularly in pancreatic cancer development. The mechanisms regulating its dual roles in tumorigenesis remain to be elucidated. Further understanding of the activin signaling pathway may identify potential therapeutic targets for human cancers and other diseases.

Transforming Growth Factor β1 Promotes Migration and Invasion of Human Hepatocellular Carcinoma Cells Via Up-Regulation of Connective Tissue Growth Factor

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors with a poor patient survival. Expression of TGF-β1 is up-regulated in HCC and is thought to play a crucial role in the occurrence and development of HCC. However, the mechanism of TGF-β1-mediated facilitation of malignant growth and invasion remains unclear, although some previous studies highlighted a potential involvement of the connective tissue growth factor (CTGF). Here we demonstrate that the in vitro migration of the HCC cell line SMMC-7721 is increased in the presence of recombinant TGF-β1, and that this effect is reversed by the specific inhibitor SB431542. Furthermore, TGF-β1 treatment up-regulated the expression of its own mRNA as well as the expression of CTGF mRNA. The TGF-β1-stimulated migration of SMMC-7721 cells was diminished by siRNA silencing of CTGF. These in vitro observations were validated in a murine xenograft model. In particular, silencing of CTFG diminished the TGF-β1-induced tumorigenesis in experimental animals. In conclusion, TGF-β1 plays a critical role in HCC migration and invasion, and this effect is dependent on CTGF.

Rosmarinic acid inhibits inflammation and angiogenesis of hepatocellular carcinoma by suppression of NF-κB signaling in H22 tumor-bearing mice

The aim of this study was to explore the anti-tumor effect and therapeutic potential of rosmarinic acid (RA) in the treatment of hepatocellular carcinoma (HCC). RA at 75, 150 and 300 mg/kg was given to H22 tumor-bearing mice by intragastric administration once daily for 10 consecutive days. Levels of inflammatory and angiogenic factors, including interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), vascular endothelial growth factor (VEGF), and transforming growth factor-β (TGF-β) were measured by enzyme linked immunosorbent assays (ELISA). Protein levels of phosphorylated NF-κB p65 and p65 were detected by western blot. mRNA level of NF-κB p65 was analyzed by qRT-PCR. The results showed that RA could effectively suppress tumor growth with fewer toxic effects by regulating the secretion of cytokines associated with inflammation and angiogenesis, and suppressing the expression of NF-κB p65 in the xenograft microenvironment. Our findings unveil the possible anti-tumor mechanisms of RA and support RA as a potential drug for the treatment of HCC.

HBx interacted with Smad4 to deprive activin a growth inhibition function in hepatocyte HL7702 on CRM1 manner

Hepatitis B virus (HBV) is implicated in the pathogenesis of hepatocellular carcinoma, which has been found to be associated with TGF-beta signaling. Activin A is a TGF-β family cytokine that exhibits cell proliferation inhibition on normal hepatocyte. How HBV-encoded X oncoprotein play in activin's activity on hepatocyte has not been developed. In this study, a nontumor hepatic cell line HL7702 with HBX ectogenic expression has been established. MTT and BrdU assays showed that HBx promoted growth of HL7702 cells in vitro and downregulated activin signaling. Deregulated activin signaling pathway by HBX failed to activate target gene p21/waf1 and p15 transcription. In addition, mammalian two-hybrid and coimmunoprecipitation assays revealed that HBX could directly interact with activin signaling transduction protein Smad4, making activated Smad2/3/4 nucleus translocation suppressed. Furthermore, we detected that leptomycin B, the inhibitor of CRM1 protein, could recover nuclear translocation of endogenous Smads complex in HL7702 with HBX expression, indicating that HBX antagonized Smads nucleus translocation, at least partially, on CRM1-dependent manner. Leptomycin B was found to have antigrowth activity on HBX-expressed HL7702, according to its antitumor function in previous study. Above all, HBX antagonized activin signaling in normal human liver cells by interacting with Smad4 might one of the considerable causes of HBX-induced hepatocyte transformation, which deprived activin's cell growth inhibition function at an early stage of tumorigenesis.

Decreased expression of the type III TGF-β receptor enhances metastasis and invasion in hepatocellullar carcinoma progression

The transforming growth factor β (TGF-β) superfamily of cytokines is multifunctional and involved in the regulation of cell growth and differentiation. TGF-β can induce an epithelial-mesenchymal transition (EMT) of both epithelial and endothelial cells. This has consequences for cancer progression in regards to both migration and invasion abilities. The type III TGF-β receptor (TβRIII) is a ubiquitously expressed TGF-β co-receptor which regulates TGF-β signaling and the progression of various types of cancer. Previous studies have shown that TβRIII exhibits abnormal expression and plays an essential role in regulating cancer invasion and metastasis, while little is known in regards to its role in hepatocellular carcinoma (HCC) progression. In the present study, we designed the present research to study the role of TβRIII in the invasion and metastasis of HCC and the possible mechanisms involved. The results demonstrated decreased expression of TβRIII in HCC patient tissues and human HCC cell lines. TGF-β1 stimulation led to the increased migratory ability and reduced expression of TβRIII in HCC cells. In addition, knockdown of TβRIII by small interfering RNA (siRNA) promoted the migration and invasion of HCC cells and induced activation of the Smad2 and Akt pathways. All the results suggest that TβRIII is a novel suppressor of HCC progression.

Transforming growth factor-β signaling in hepatocytes promotes hepatic fibrosis and carcinogenesis in mice with hepatocyte-specific deletion of TAK1

BACKGROUND & AIMS

Transforming growth factor (TGF)-β-activated kinase 1 (TAK1) is activated in different cytokine signaling pathways. Deletion of Tak1 from hepatocytes results in spontaneous development of hepatocellular carcinoma (HCC), liver inflammation, and fibrosis. TGF-β activates TAK1 and Smad signaling, which regulate cell death, proliferation, and carcinogenesis. However, it is not clear whether TGF-β signaling in hepatocytes, via TGF-β receptor-2 (Tgfbr2), promotes HCC and liver fibrosis.

METHODS

We generated mice with hepatocyte-specific deletion of Tak1 (Tak1ΔHep), as well as Tak1/Tgfbr2DHep and Tak1/Smad4ΔHep mice. Tak1flox/flox, Tgfbr2ΔHep, and Smad4ΔHep mice were used as controls, respectively. We assessed development of liver injury, inflammation, fibrosis, and HCC. Primary hepatocytes isolated from these mice were used to assess TGF-β-mediated signaling.

RESULTS

Levels of TGF-β, TGF-βR2, and phospho-Smad2/3 were increased in HCCs from Tak1ΔHep mice, which developed liver fibrosis and inflammation by 1 month and HCC by 9 months. However, Tak1/Tgfbr2ΔHep mice did not have this phenotype, and their hepatocytes did not undergo spontaneous cell death or compensatory proliferation. Hepatocytes from Tak1ΔHep mice incubated with TGF-β did not activate p38, c-Jun N-terminal kinase, or nuclear factor-κB; conversely, TGF-β-mediated cell death and phosphorylation of Smad2/3 were increased, compared with control hepatocytes. Blocking the Smad pathway inhibited TGF-β-mediated death of Tak1-/- hepatocytes. Accordingly, disruption of Smad4 reduced the spontaneous liver injury, inflammation, fibrosis, and HCC that develops in Tak1ΔHep mice. Levels of the anti-apoptotic protein Bcl-xL, β-catenin, connective tissue growth factor, and vascular endothelial growth factor were increased in HCC from Tak1ΔHep mice, but not in HCCs from Tak1/Tgfbr2ΔHep mice. Injection of N-nitrosodiethylamine induced HCC formation in wild-type mice, but less in Tgfbr2ΔHep mice.

CONCLUSIONS

TGF-β promotes development of HCC in Tak1ΔHep mice by inducing hepatocyte apoptosis and compensatory proliferation during early phases of tumorigenesis, and inducing expression of anti-apoptotic, pro-oncogenic, and angiogenic factors during tumor progression.

Smad4 expression in hepatocellular carcinoma differs by hepatitis status

AIMS

Primary hepatocellular carcinoma (HCC) is a common malignancy often related to hepatitis viral infection. Smad4 is known to mediate the TGF-β pathway to suppress tumorigenesis. However, the function of Smad4 in HCC is still controversial. In this study we compared levels of Smad4 in HCC tissues with or without hepatitis virus infection and adjacent normal-appearing liver.

METHODS

Samples from HCC patients were analyzed for Smad4 protein and mRNA expression by immunohistochemistry (IHC), RT-PCR and Western blotting.

RESULTS

We found that tumor tissues expressed less Smad4 mRNA and protein than the adjacent tissues. Most HCC tumor tissues were negative for Smad4 in IHC staining, while the majority of adjacent tissues were positively stained. Interestingly, protein levels were higher in HCC tissues with viral hepatitis than those without virus infection. Suppression of expression appeared closely related to HCC, so that Smad4 appears to function as a tumor suppressor gene (TSG).

CONCLUSION

Patients with hepatitis viral infection, at higher risk for HCC, exhibited increased Smad4 protein expression suggesting hepatitis virus may modulate Smad4 expression, which is functionally distinct from its putative role as a TSG. Smad4 expression may thus be an applicable marker for diagnosis and/or a target to develop therapeutic agents for HCC.

Increased serum activin-A differentiates alcoholic from cirrhosis of other aetiologies

BACKGROUND

Activin-A is a molecule of the TGF superfamily, implicated in liver fibrosis, regeneration and stem cell differentiation. However, data on activins in liver diseases are few. We therefore studied serum levels of activin-A in chronic liver diseases. To identify the origin of activin-A, levels in the hepatic vein were also estimated.

MATERIALS AND METHODS

Nineteen controls and 162 patients participated in the study: 39 with hepatocellular carcinoma (HCC: 19 viral associated and 20 alcohol associated), 18 with chronic hepatitis C (CHC), 47 with primary biliary cirrhosis (26 PBC stage I-II and 21 stage IV), 22 with alcoholic cirrhosis (AC, hepatic vein blood available in 16), 20 with HCV cirrhosis (hepatic vein blood available in 18) and 16 patients with alcoholic fatty liver with mild to moderate fibrosis but no cirrhosis.

RESULTS

Activin-A levels were significantly increased (P < 0·001) in serum of patients with AC (median 673 pg/mL, range 449-3279), compared with either controls (149 pg/mL, 91-193) or patients with viral cirrhosis (189 pg/mL, 81-480), CHC (142 pg/mL, 65-559) PBC stage I-II (100 pg/mL, 59-597) and PBC stage IV (104 pg/mL, 81-579). Only patients with AC-associated HCC had significantly increased levels of activin-A (2403 pg/mL, 1561-7220 pg/mL). Activin-A serum levels could accurately discriminate AC from cirrhosis of other aetiologies and noncirrhotic alcoholic fatty liver with fibrosis.

CONCLUSIONS

Increased serum levels of activin-A only in patients with alcohol-related cirrhosis or HCC suggest a possible role of this molecule in the pathophysiology of AC. Further research is warranted to elucidate its role during the profibrotic process and its possible clinical applications.

Role of Smad4 in cancer invasion and metastasis

Transforming growth factor beta (TGF-β) is a ubiquitous and essential regulator of cellular and physiologic processes including proliferation, differentiation, migration, cell survival, angiogenesis and immunosurveillance. The tumor suppressor gene Smad4 (DPC4) is the central intracellular mediator of transforming growth factor-β-Smad(TGF-β-Smad) signaling, which is a key pathway in cancer invasion and metastasis. This review focuses on the mechanisms whereby the Smads are modified and regulated, and summarizes current views on the role of Smad4 in tumorigenesis, with emphasis on cancer invasion and metastasis.

Activins and activin antagonists in hepatocellular carcinoma

In many parts of the world hepatocellular carcinoma (HCC) is among the leading causes of cancer-related mortality but the underlying molecular pathology is still insufficiently understood. There is increasing evidence that activins, which are members of the transforming growth factor β (TGFβ) superfamily of growth and differentiation factors, could play important roles in liver carcinogenesis. Activins are disulphide-linked homo- or heterodimers formed from four different β subunits termed βA, βB, βC, and βE, respectively. Activin A, the dimer of two βA subunits, is critically involved in the regulation of cell growth, apoptosis, and tissue architecture in the liver, while the hepatic function of other activins is largely unexplored so far. Negative regulators of activin signals include antagonists in the extracellular space like the binding proteins follistatin and FLRG, and at the cell membrane antagonistic co-receptors like Cripto or BAMBI. Additionally, in the intracellular space inhibitory Smads can modulate and control activin activity. Accumulating data suggest that deregulation of activin signals contributes to pathologic conditions such as chronic inflammation, fibrosis and development of cancer. The current article reviews the alterations in components of the activin signaling pathway that have been observed in HCC and discusses their potential significance for liver tumorigenesis.

Expression of transforming growth factor β1 and its type I receptor in gastric cancer

AIM: To evaluate the significance of transforming growth factor-β1 (TGF-β1) and its β I type receptor (TGF-β R1) in the pathogenesis of gastric carcinoma.

METHODS: TGF-β1 and TGF-β R1 were detected by immunohistochemistry in and real-time PCR (RT-PCR) 50 cases of gastric carcinoma, 19 cases of atrophic gastritis and 18 cases of normal gastric mucosa.

RESULTS: Immunohistochemistry demonstrated that the positive expression rates of TGF-β1 and TGF-β R1 were significantly higher in gastric carcinoma (80.0% and 75.0%) than in normal gastric mucosa (33.3% and 27.8%) and atrophic gastritis (36.8% and 36.8%) (P < 0.01). The lower the differentiation of gastric carcinoma was, the higher the expression of TGF-β1 and TGF-β R1 was (r = 35.58, P < 0.01). Furthermore, the expression of TGF-β1 and TGF-β R1 mRNA was significantly higher in gastric carcinoma than in normal gastric mucosa and atrophic gastritis (TGF-β1: 4.20 ± 0.51 vs 9.15 ± 2.12, 8.22 ± 1.81; TGF-β R1: 1.28 ± 0.48 vs 5.55 ± 1.48, 4.19 ± 0.95).

CONCLUSION: High expression of TGF-β1 and TGF-β R1 is correlated with the development, biologic behavior and prognosis of gastric carcinoma.

Loss of p12CDK2-AP1 expression in human oral squamous cell carcinoma with disrupted transforming growth factor-beta-Smad signaling pathway

We examined correlations between TGF-beta1, TbetaR-I and TbetaR-II, p12(CDK2-AP1), p21(WAF1), p27(KIP1), Smad2, and p-Smad2 in 125 cases of human oral squamous cell carcinoma (OSCC) to test the hypothesis that resistance to TGF-beta1-induced growth suppression is due to the disruption of its signaling pathway as a consequence of reduced or lost p12(CDK2-AP1). Immunoreactivity for TbetaR-II decreased in OSCC with increasing disease aggressiveness; however, no differences were observed for TbetaR-I and TGF-beta1. The expression of TbetaR-II significantly correlated with p12(CDK2-AP1) and p27(KIP1) (P < .001 and P < .01, respectively). Furthermore, there was a significant relationship between TbetaR-II expression and p-Smad2 (P < .001). The in vivo correlation of the levels of TbetaR-II, p12(CDK2-AP1), and p27(KIP1) was confirmed in normal and OSCC cell lines. Additionally, in vitro analysis of TGF-beta1-treated cells showed that TGF-beta1 treatment of normal keratinocytes suppressed cell growth with upregulation of p-Smad2, p12(CDK2-AP1), and p21(WAF1) expression, whereas there was no effect on OSCC cell lines. These results provide evidence of a link between a disrupted TGF-beta-Smad signaling pathway and loss of induction of cell cycle-inhibitory proteins, especially p12(CDK2-AP1) in OSCC, which may lead to the resistance of TGF-beta1 growth-inhibitory effect on OSCC.

Dynamic expression and alteration characteristic of insulin-like growth factor-Ⅱ in the carcinogenesis of hepatocellular carcinoma

AIM: To investigate the dynamic expression and alteration of insulin-like growth factor-Ⅱ(IGF-Ⅱ) during in the pathogenesis and development of hepatocellular carcinoma.

METHODS: Hepatoma models were induced with 2-fluorenylacetamide (2-FAA) in male Sprague-Dawley (SD) rats. The morphological changes of rat livers were observed by HE staining. The dynamic changes of IGF-Ⅱ in rat livers and sera were quantitatively analyzed by enzyme linked immunosorbent assay (ELISA). Simultaneously, the expression and cellular distribution of IGF-Ⅱ were detected by immunohistochemistry.

RESULTS: Histological examination confirmed that the expression of IGF-Ⅱwas increased in gradient after granule-like degeneration, atypical hyperplasia and carcinoma appeared in hepatocytes, and it was significantly higher in carcinoma group than that in degeneration and control group (carcinoma vs degeneration, χ² = 9.55, P < 0.01; carcinoma vs control, χ² = 14.00, P < 0.01). IGF-Ⅱwas positively expressed inside the liver cancer cells, and there was positive correlation between tissue and serum IGF-Ⅱ expression (r = 0.97, P < 0.01).

CONCLUSION: IGF-Ⅱ is involved in the carcinogenesis of hepatocellular carcinoma, and its expression is up-regulated at the early stage of carcinoma, which can help to achieve early diagnosis and prognosis judgment.

Correlations of insulin-like growth factor-II expression with hepatitis B virus DNA replication and clinical pathological characteristics in human hepatocelullar carcinoma

AIM: To investigate the expression of insulin-like growth factor-II (IGF-II) in hepatocellular carcinoma (HCC) as well as its correlations with the pathogenesis, development and prognosis of HCC.

METHODS: IGF-II expression was detected by immunohistochemistry in 30 HCC and their corresponding non-cancerous tissues. Liver HBV DNA was detected by in situ molecular hybridization technique and the relationship was analyzed between IGF-II expression and HBV replication or the clinical pathological characteristics.

RESULTS: The stronger expression of IGF-II was found in liver cancer tissues. The positive rate of IGF-II expression was 83.3% in HCC, and 46.7% in non-cancerous liver tissues (P < 0.01), respectively. The expression of IGF-II was significantly higher in HCC with moderate or low differentiation than that with well differentiation (90.0%, 100% vs 42.9%, P < 0.05 or P < 0.01). IGF-II expression was markedly lower in HCC without serosa invasion than that with serosa invasion (95.0% vs 60.0%, P < 0.05). IGF-II expression was also correlated with tumor size (< 5 cm vs ≥ 5 cm: 58.3% vs 100%, P < 0.01), but with tumor number (P > 0.05). The level of IGF-II expression in HBV DNA-positive HCC was significantly higher than that in HBV DNA-negative ones (94.7% vs 63.6%, P < 0.05).

CONCLUSION: IGF-II is highly expressed in HCC, and the aberrant expression of IGF-II is correlated with the degree of differentiation, invasion and tumor size, and it may be used as a marker for development and prognosis of HCC.