High expression of p21WAF1/CIP1 is correlated with human hepatocellular carcinoma in patients with hepatitis C virus-associated chronic liver diseases

Isorhamnetin exerts anti-tumor activity in DEN + CCl4-induced HCC mice

BACKGROUND

Hepatocellular carcinoma (HCC) is the most prevalent type of liver cancer and the main cause of cancer death globally. The use of medicinal herbs as chemotherapeutic agents in cancer treatment is receiving attention as they possess no or minimum side effects. Isorhamnetin (IRN), a flavonoid, has been under attention for its anti-inflammatory and anti-proliferative properties in a number of cancers, including colorectal, skin, and lung cancers. However, the in vivo mechanism of isorhamnetin to suppress liver cancer has yet to be explored.

METHODS AND RESULT

HCC was induced by N-diethylnitrosamine (DEN) and carbon tetrachloride (CCL₄) in Swiss albino mice. Isorhamnetin (100 mg/kg body weight) was given to examine its anti-tumor properties in HCC mice model. Histological analysis and liver function assays were performed to assess changes in liver anatomy. Probable molecular pathways were explored using immunoblot, qPCR, ELISA, and immunohistochemistry techniques. Isorhamnetin inhibited various pro-inflammatory cytokines to suppress cancer-inducing inflammation. Additionally, it regulated Akt and MAPKs to suppress Nrf2 signaling. Isorhamnetin activated PPAR-γ and autophagy while suppressing cell cycle progression in DEN + CCl₄-administered mice. Additionally, isorhamnetin regulated various signaling pathways to suppress cell proliferation, metabolism, and epithelial-mesenchymal transition in HCC.

CONCLUSION

Regulating diverse cellular signaling pathways makes isorhamnetin a better anti-cancer chemotherapeutic candidate in HCC. Importantly, the anti-TNF-α properties of isorhamnetin could prove it a valuable therapeutic agent in sorafenib-resistant HCC patients. Additionally, anti-TGF-β properties of isorhamnetin could be utilized to reduce the EMT-inducing side effects of doxorubicin.

SOCS1 Deficiency Promotes Hepatocellular Carcinoma via SOCS3-Dependent CDKN1A Induction and NRF2 Activation

SOCS1 deficiency, which increases susceptibility to hepatocellular carcinoma (HCC), promotes CDKN1A expression in the liver. High CDKN1A expression correlates with disease severity in many cancers. Here, we demonstrate a crucial pathogenic role of CDKN1A in diethyl nitrosamine (DEN)-induced HCC in SOCS1-deficient mice. Mechanistic studies on DEN-induced genotoxic response revealed that SOCS1-deficient hepatocytes upregulate SOCS3 expression, SOCS3 promotes p53 activation, and Cdkn1a induction that were abolished by deleting either Socs3 or Tp53. Previous reports implicate CDKN1A in promoting oxidative stress response mediated by NRF2, which is required for DEN-induced hepatocarcinogenesis. We show increased induction of NRF2 and its target genes in SOCS1-deficient livers following DEN treatment that was abrogated by the deletion of either Cdkn1a or Socs3. Loss of SOCS3 in SOCS1-deficient mice reduced the growth of DEN-induced HCC without affecting tumor incidence. In the TCGA-LIHC dataset, the SOCS1-low/SOCS3-high subgroup displayed increased CDKN1A expression, enrichment of NRF2 transcriptional signature, faster disease progression, and poor prognosis. Overall, our findings show that SOCS1 deficiency in hepatocytes promotes compensatory SOCS3 expression, p53 activation, CDKN1A induction, and NRF2 activation, which can facilitate cellular adaptation to oxidative stress and promote neoplastic growth. Thus, the NRF2 pathway represents a potential therapeutic target in SOCS1-low/SOCS3-high HCC cases.

Cellular senescence in cancer: clinical detection and prognostic implications

Cellular senescence is a state of stable cell-cycle arrest with secretory features in response to cellular stress. Historically, it has been considered as an endogenous evolutionary homeostatic mechanism to eliminate damaged cells, including damaged cells which are at risk of malignant transformation, thereby protecting against cancer. However, accumulation of senescent cells can cause long-term detrimental effects, mainly through the senescence-associated secretory phenotype, and paradoxically contribute to age-related diseases including cancer. Besides its role as tumor suppressor, cellular senescence is increasingly being recognized as an in vivo response in cancer patients to various anticancer therapies. Its role in cancer is ambiguous and even controversial, and senescence has recently been promoted as an emerging hallmark of cancer because of its hallmark-promoting capabilities. In addition, the prognostic implications of cellular senescence have been underappreciated due to the challenging detection and sparse in and ex vivo evidence of cellular senescence in cancer patients, which is only now catching up. In this review, we highlight the approaches and current challenges of in and ex vivo detection of cellular senescence in cancer patients, and we discuss the prognostic implications of cellular senescence based on in and ex vivo evidence in cancer patients.

Autophagy-Related Gene Pairs Signature for the Prognosis of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) has been recognized as the third leading cause of cancer-related deaths worldwide. There is increasing evidence that the abnormal expression of autophagy-related genes plays an important role in the occurrence and development of HCC. Therefore, the study of autophagy-related genes can further elucidate the genetic drivers of cancer and provide valuable therapeutic targets for clinical treatment. In this study, we used 232 autophagy-related genes extracted from the Human Autophagy Database (HADb) and Molecular Signatures Database (MSigDB) to construct 1884 autophagy-related gene pairs. On this basis, we developed a prognostic model based on autophagy-related gene pairs using least absolute shrinkage and selection operator (LASSO) Cox regression to evaluate the prognosis of patients after liver cancer resection. We then used 845 liver cancer samples from three different databases to test the reliability of the risk signature through survival analysis, receiver operating characteristic (ROC) curve analysis, univariate and multivariate analysis. To further explore the underlying biological mechanisms, we conducted an enrichment analysis of autophagy-related genes. Finally, we combined the signature with independent prognostic factors to construct a nomogram. Based on the autophagy-related gene pair (ARGP) signature, we can divide patients into high- or low-risk groups. Survival analysis and ROC curve analysis verified the validity of the signature (AUC: 0.786—0.828). Multivariate Cox regression showed that the risk score can be used as an independent predictor of the clinical outcomes of liver cancer patients. Notably, this model has a more accurate predictive effect than most prognostic models for hepatocellular carcinoma. Moreover, our model is a powerful supplement to the HCC staging indicator, and a nomogram comprising both indicators can provide a better prognostic effect. Based on pairs of multiple autophagy-related genes, we proposed a prognostic model for predicting the overall survival rate of HCC patients after surgery, which is a promising prognostic indicator. This study confirms the importance of autophagy in the occurrence and development of HCC, and also provides potential biomarkers for targeted treatments.

An in vitro Study on the Role of Hepatitis B Virus X Protein C-Terminal Truncation in Liver Disease Development

Hepatitis B virus X protein C-terminal 127 amino acid truncation is often found expressed in hepatocellular carcinoma (HCC) tissue samples. The present in vitro study tried to determine the role of this truncation mutant in the hepatitis B-related liver diseases such as fibrosis, cirrhosis, HCC, and metastasis. HBx gene and its 127 amino acid truncation mutant were cloned in mammalian expression vectors and transfected in human hepatoma cell line. Changes in cell growth/proliferation, cell cycle phase distribution, expression of cell cycle regulatory genes, mitochondrial depolarization, and intracellular reactive oxygen species (ROS) level were analyzed. Green fluorescent protein (GFP)-tagged version of HBx and the truncation mutant were also created and the effects of truncation on HBx intracellular expression pattern and localization were studied. Effect of time lapse on protein expression pattern was also analyzed. The truncation mutant of HBx is more efficient in inducing cell proliferation, and causes more ROS production and less mitochondrial depolarization as compared with wild type (wt) HBx. In addition, gene expression is altered in favor of carcinogenesis in the presence of the truncation mutant. Furthermore, mitochondrial perinuclear aggregation is achieved earlier in the presence of the truncation mutant. Therefore, HBx C-terminal 127 amino acid truncation might be playing important roles in the development of hepatitis B-related liver diseases by inducing cell proliferation, altering gene expression, altering mitochondrial potential, inducing mitochondrial clustering and oxidative stress, and changing HBx expression pattern.

Effects of apoptosis on liver aging

As an irreversible and perennial process, aging is accompanied by functional and morphological declines in organs. Generally, aging liver exhibits a decline in volume and hepatic blood flow. Even with a preeminent regenerative capacity to restore its functions after liver cell loss, its biosynthesis and metabolism abilities decline, and these are difficult to restore to previous standards. Apoptosis is a programmed death process via intrinsic and extrinsic pathways, in which Bcl-2 family proteins and apoptosis-related genes, such as p21 and p53, are involved. Apoptosis inflicts both favorable and adverse influences on liver aging. Apoptosis eliminates transformed abnormal cells but promotes age-related liver diseases, such as nonalcoholic fatty liver disease, liver fibrosis, cirrhosis, and liver cancer. We summarize the roles of apoptosis in liver aging and age-related liver diseases.

Oxidative stress, a trigger of hepatitis C and B virus-induced liver carcinogenesis

Virally induced liver cancer usually evolves over long periods of time in the context of a strongly oxidative microenvironment, characterized by chronic liver inflammation and regeneration processes. They ultimately lead to oncogenic mutations in many cellular signaling cascades that drive cell growth and proliferation. Oxidative stress, induced by hepatitis viruses, therefore is one of the factors that drives the neoplastic transformation process in the liver. This review summarizes current knowledge on oxidative stress and oxidative stress responses induced by human hepatitis B and C viruses. It focuses on the molecular mechanisms by which these viruses activate cellular enzymes/systems that generate or scavenge reactive oxygen species (ROS) and control cellular redox homeostasis. The impact of an altered cellular redox homeostasis on the initiation and establishment of chronic viral infection, as well as on the course and outcome of liver fibrosis and hepatocarcinogenesis will be discussed The review neither discusses reactive nitrogen species, although their metabolism is interferes with that of ROS, nor antioxidants as potential therapeutic remedies against viral infections, both subjects meriting an independent review.

Liver damage and senescence increases in patients developing hepatocellular carcinoma

BACKGROUND AND AIM

Most patients with a hepatocellular carcinoma (HCC) have an underlying chronic liver inflammation, which causes a continuous damage leading to liver cirrhosis and eventually HCC. However, only a minority of cirrhotic patients develop HCC. To assess a possible differential impact of liver inflammation in patients developing HCC versus patients remaining tumor-free, we designed a longitudinal study and analysed liver tissue of the same patients (n = 33) at two points in time: once when no HCC was present and once several years later when an HCC was present. As a control group, we followed cirrhotic patients (n = 37) remaining tumor-free over a similar time frame.

METHODS

We analysed cell damage and senescence of hepatocytes by measuring γ-H2AX positivity, p16^INK4 and p21^WAF/Cip1 expression, nuclear size, and telomere length.

RESULTS

γ-H2AX positivity, p16^INK4 and p21^WAF/Cip1 expression, in the first liver biopsy was similar in patients developing HCC later on and cirrhotic patients remaining tumor free. In contrast, γ-H2AX positivity, p16^INK4 and p21^WAF/Cip1 expression, was significantly higher in the second non-tumoral liver biopsy of HCC patients than in the control patients. Consequently, the individual increase in γ-H2AX positivity, p16^INK4 and p21^WAF/Cip1 expression, from the first biopsy to the second biopsy was significantly higher in patients developing HCC than in patients remaining tumor free. In addition, changes in nuclear size and telomere length revealed a more pronounced cell aging in patients developing HCC than in patients remaining tumor free.

CONCLUSIONS

Hepatocytes from patients developing HCC go through more pronounced cell damage and senescence in contrast to cirrhotic patients remaining tumor free.

EGFR and SYNE2 are associated with p21 expression and SYNE2 variants predict post-operative clinical outcomes in HBV-related hepatocellular carcinoma

This study was to explore the association between gene variants and p21 expression and investigate the TP53-independent p21 regulation in hepatitis B virus (HBV) related hepatocellular carcinoma (HCC) patients from Guangxi by genome-wide association study. 426 HBV-related HCC patients were enrolled. Results showed that, after quality control, a total of 21,643 SNPs were identified in 107 p21 positive and 298 p21 negative patients. The variants of epidermal growth factor receptor (EGFR; rs2227983 and rs6950826) and spectrin repeat containing, nuclear envelope 2 (SYNE2; rs8010699, rs4027405 and rs1890908) were associated with p21 expression. Moreover the haplotype block (rs2227983 and rs6950826, r² = 0.378) in EGFR and the haplotype block in SYNE2 (rs8010699 was in strong LD with rs4027405 and rs1890908 (r² = 0.91 and 0.70, respectively)) were identified, and the haplotype A-G of EGFR and haplotype G-A-A of SYNE2 were significantly associated with p21 expression (P < 0.01). rs4027405 and rs1890908 were significantly associated with overall survival, and patients with AG/GG genotypes of SYNE2 gene had a worse overall survival (P = 0.001, P = 0.002). Our findings indicate that variants of EGFR and SYNE2 play an important role in p21 regulation and are associated with the clinical outcome of HBV-related HCC in a TP53-indenpdent manner.

p21 ablation in liver enhances DNA damage, cholestasis, and carcinogenesis

Genetic mouse studies suggest that the NF-κB pathway regulator NEMO (also known as IKKγ) controls chronic inflammation and carcinogenesis in the liver. However, the molecular mechanisms explaining the function of NEMO are not well defined. Here, we report that overexpression of the cell-cycle regulator p21 is a critical feature of liver inflammation and carcinogenesis caused by the loss of NEMO. NEMO(Δhepa) mice develop chronic hepatitis characterized by increased hepatocyte apoptosis and proliferation that causes the development of fibrosis and hepatocellular carcinoma (HCC), similar to the situation in human liver disease. Having identified p21 overexpression in this model, we evaluated its role in disease progression and LPS-mediated liver injury in double mutant NEMO(Δhepa)/p21(-/-) mice. Eight-week-old NEMO(Δhepa)/p21(-/-) animals displayed accelerated liver damage that was not associated with alterations in cell-cycle progression or the inflammatory response. However, livers from NEMO(Δhepa)/p21(-/-) mice displayed more severe DNA damage that was further characterized by LPS administration correlating with higher lethality of the animals. This phenotype was attenuated by genetic ablation of the TNF receptor TNF-R1 in NEMO(Δhepa)/p21(-/-) mice, demonstrating that DNA damage is induced via TNF. One-year-old NEMO(Δhepa)/p21(-/-) mice displayed greater numbers of HCC and severe cholestasis compared with NEMO(Δhepa) animals. Therefore, p21 overexpression in NEMO(Δhepa) animals protects against DNA damage, acceleration of hepatocarcinogenesis, and cholestasis. Taken together, our findings illustrate how loss of NEMO promotes chronic liver inflammation and carcinogenesis, and they identify a novel protective role for p21 against the generation of DNA damage.

p21 promotes sustained liver regeneration and hepatocarcinogenesis in chronic cholestatic liver injury

BACKGROUND AND AIMS

The cyclin-dependent kinase inhibitor p21 has been implicated as a tumour suppressor. Moreover, recent genetic studies suggest that p21 might be a potential therapeutic target to improve regeneration in chronic diseases. The aim of this study was to delineate the role of p21 in chronic liver injury and to specify its role in hepatocarcinogenesis in a mouse model of chronic cholestatic liver injury.

METHODS

The degree of liver injury, regeneration and tumour formation was assessed in Mdr2(-/-) mice and compared with Mdr2/ p21(-/-) mice. Moreover, the role of p21 was evaluated in hepatoma cells in vitro and in human hepatocellular carcinoma (HCC).

RESULTS

Mdr2(-/-) mice developed HCCs as a consequence of chronic inflammatory liver injury. In contrast, tumour development was profoundly delayed in Mdr2/ p21(-/-) mice. Delayed tumour development was accompanied by markedly impaired liver regeneration in Mdr2/ p21(-/-) mice. Moreover, the regenerative capacity of the Mdr2/ p21(-/-) livers in response to partial hepatectomy declined with age in these mice. Hepatocyte transplantation experiments revealed that impaired liver regeneration was due to intrinsic factors within the cells and changes in the Mdr2/ p21(-/-) microenvironment. In human HCCs, a subset of tumours expressed p21, which was associated with a significant shorter patient survival.

CONCLUSIONS

We provide experimental evidence that p21 is required for sustained liver regeneration and tumour development in chronic liver injury indicating that p21 needs to be tightly regulated in order to balance liver regeneration and cancer risk. Moreover, we identify p21 as a negative prognostic marker in human HCC.

Alcohol induced hepatic degeneration in a hepatitis C virus core protein transgenic mouse model

Hepatitis C virus (HCV) has become a major public health issue. It is prevalent in most countries. HCV infection frequently begins without clinical symptoms, before progressing to persistent viremia, chronic hepatitis, cirrhosis and hepatocellular carcinoma (HCC) in the majority of patients (70% to 80%). Alcohol is an independent cofactor that accelerates the development of HCC in chronic hepatitis C patients. The purpose of the current study was to evaluate ethanol-induced hepatic changes in HCV core-Tg mice and mutant core Tg mice. Wild type (NTG), core wild-Tg mice (TG-K), mutant core 116-Tg mice (TG-116) and mutant core 99-Tg mice (TG-99) were used in this investigation. All groups were given drinking water with 10% ethanol and 5% sucrose for 13 weeks. To observe liver morphological changes, we performed histopathological and immunohistochemical examinations. Histopathologically, NTG, TG-K and TG-116 mice showed moderate centrilobular necrosis, while severe centrilobular necrosis and hepatocyte dissociation were observed in TG-99 mice with increasing lymphocyte infiltration and piecemeal necrosis. In all groups, a small amount of collagen fiber was found, principally in portal areas. None of the mice were found to have myofibroblasts based on immunohistochemical staining specific for α-SMA. CYP2E1-positive cells were clearly detected in the centrilobular area in all groups. In the TG-99 mice, we also observed cells positive for CK8/18, TGF-β1 and phosphorylated (p)-Smad2/3 and p21 around the necrotic hepatocytes in the centrilobular area (p < 0.01). Based on our data, alcohol intake induced piecemeal necrosis and hepatocyte dissociation in the TG-99 mice. These phenomena involved activation of the TGF-β1/p-Smad2/3/p21 signaling pathway in hepatocytes. Data from this study will be useful for elucidating the association between alcohol intake and HCV infection.

HCMV activates the IL-6-JAK-STAT3 axis in HepG2 cells and primary human hepatocytes

Objectives

There has been increased interest in the possible role of human cytomegalovirus (HCMV) in carcinogenesis during the last decade. HCMV seroprevalence was enhanced in patients with hepatocellular carcinoma (HCC) but a possible relationship between HCC and HCMV infection remained to be assessed. The aim of this work was to investigate the pro-tumor influence of HCMV on primary human hepatocytes (PHH) and HepG2 cells.

Methods

Following infection of PHH and HepG2 cells by two different strains of HCMV, we measured the production of IL-6 in culture supernatants by ELISA and the protein levels of STAT3, pSTAT3, JAK, cyclin D1, survivin, p53, p21, and Mdm2 by western Blotting in infected and uninfected cells. Cell proliferation and transformation were investigated using Ki67Ag expression measurement and soft-agar colony formation assay respectively.

Results

Infection of HepG2 cells and PHH by HCMV resulted in the production of IL-6 and the subsequent activation of the IL-6R-JAK-STAT3 pathway. HCMV increased the expression of cyclin D1 and survivin. Cell proliferation was enhanced in HepG2 and PHH infected with HCMV, despite a paradoxical overexpression of p53 and p21. More importantly, we observed the formation of colonies in soft agar seeded with PHH infected with HCMV and when we challenged the HepG2 cultures to form tumorspheres, we found that the HCMV-infected cultures formed 2.5-fold more tumorspheres than uninfected cultures.

Conclusion

HCMV activated the IL-6-JAK-STAT3 pathway in PHH and HepG2 cells, favored cellular proliferation, induced PHH transformation and enhanced HepG2 tumorsphere formation. Our observations raise the possibility that HCMV infection might be involved in the genesis of hepatocellular carcinoma.

TRIM39 regulates cell cycle progression and DNA damage responses via stabilizing p21

The biological function of Tripartite Motif 39 (TRIM39) remains largely unknown. In this study, we report that TRIM39 regulates the steady-state levels of p21 and is a pivotal determinant of cell fate. Ablation of TRIM39 leads to destabilization of p21 and increased G1/S transition in unperturbed cells. Furthermore, DNA damage-induced p21 accumulation is completely abolished in cells with depleted TRIM39. As a result, silencing of TRIM39 abrogates the G2 checkpoint induced by genotoxic stress, leading to increased mitotic entry and, ultimately, apoptosis. Importantly, we show p21 is a crucial downstream effector of TRIM39 mediating G1/S transition and DNA damage-induced G2 arrest. Mechanistically, TRIM39 interacts with p21, which subsequently prevents Cdt2 from binding to p21, therefore blocking ubiquitylation and proteasomal degradation of p21 mediated by CRL4(Cdt2) E3 ligase. Strikingly, we found a significant correlation between p21 abundance and TRIM39 expression levels in human hepatocellular carcinoma samples. Our findings identify a causal role for TRIM39 in regulating cell cycle progression and the balance between cytostasis and apoptosis after DNA damage via stabilizing p21.

p21(WAF1/Cip1/Sdi1) knockout mice respond to doxorubicin with reduced cardiotoxicity

Doxorubicin (Dox) is an antineoplastic agent that can cause cardiomyopathy in humans and experimental animals. As an inducer of reactive oxygen species and a DNA damaging agent, Dox causes elevated expression of p21(WAF1/Cip1/Sdi1) (p21) gene. Elevated levels of p21 mRNA and p21 protein have been detected in the myocardium of mice following Dox treatment. With chronic treatment of Dox, wild type (WT) animals develop cardiomyopathy evidenced by elongated nuclei, mitochondrial swelling, myofilamental disarray, reduced cardiac output, reduced ejection fraction, reduced left ventricular contractility, and elevated expression of ANF gene. In contrast, p21 knockout (p21KO) mice did not show significant changes in the same parameters in response to Dox treatment. In an effort to understand the mechanism of the resistance against Dox induced cardiomyopathy, we measured levels of antioxidant enzymes and found that p21KO mice did not contain elevated basal or inducible levels of glutathione peroxidase and catalase. Measurements of 6 circulating cytokines indicated elevation of IL-6, IL-12, IFNγ and TNFα in Dox treated WT mice but not p21KO mice. Dox induced elevation of IL-6 mRNA was detected in the myocardium of WT mice but not p21KO mice. While the mechanism of the resistance against Dox induced cardiomyopathy remains unclear, lack of inflammatory response may contribute to the observed cardiac protection in p21KO mice.

RNA interference-mediated knockdown of p21 promotes cell proliferation in human hepatocellular carcinoma cell line SMMC-7721

AIM: To investigate the effect of RNA interference (RNAi)-mediated knockdown of p21 on cell proliferation in human hepatocellular carcinoma cell line SMMC-7721.

METHODS: p21 knockdown was achieved in SMMC-7721 cells by lentivirus-mediated tranfection of small interfering RNA (siRNA) targeting the p21 gene. The expression of p21 mRNA and protein was detected by RT-PCR and Western blot, respectively. Cell cycle of 7721-p21 RNAi group (those transfected with p21 siRNA), 7721-NC group (those transfected with empty vecter) and 7721 group (those non-transfected) was determined by flow cytometry (FCM). Cell proliferation was measured by MTT assay and colony formation assay.

RESULTS: The expression of p21 mRNA and protein was obviously reduced in cells transfected with siRNA targeting the p21 gene. The percentage of cells in G₀/G₁ phase was significantly lower in 7721-p21 RNAi group than in 7721-NC group and 7721 group (32.82% ± 3.27% vs 61.25% ± 0.76%, 57.77% ± 4.08%, both P < 0.05). The growth of cells in 7721-p21 RNAi group was faster than that in 7721-NC group and 7721 group. The number of cell colonies formed in 7721-p21 RNAi group was significantly higher than those in 7721-NC group and 7721 group (81.24 ± 1.5 vs 51.67 ± 2.08, 52.73 ± 1.53, both P < 0.05).

CONCLUSION: p21 can inhibit the proliferation of SMMC-7721 cells.

Oncogenic potential of hepatitis C virus proteins

Chronic hepatitis C virus (HCV) infection is a major risk factor for liver disease progression, and may lead to cirrhosis and hepatocellular carcinoma (HCC). The HCV genome contains a single-stranded positive sense RNA with a cytoplasmic lifecycle. HCV proteins interact with many host-cell factors and are involved in a wide range of activities, including cell cycle regulation, transcriptional regulation, cell proliferation, apoptosis, lipid metabolism, and cell growth promotion. Increasing experimental evidences suggest that HCV contributes to HCC by modulating pathways that may promote malignant transformation of hepatocytes. At least four of the 10 HCV gene products, namely core, NS3, NS5A and NS5B play roles in several potentially oncogenic pathways. Induction of both endoplasmic reticulum (ER) stress and oxidative stress by HCV proteins may also contribute to hepatocyte growth promotion. The current review identifies important functions of the viral proteins connecting HCV infections and potential for development of HCC. However, most of the putative transforming potentials of the HCV proteins have been defined in artificial cellular systems, and need to be established relevant to infection and disease models. The new insight into the mechanisms for HCV mediated disease progression may offer novel therapeutic targets for one of the most devastating human malignancies in the world today.

p21/Wafl/Cipl cellular expression in chronic long-lasting hepatitis C: correlation with HCV proteins (C, NS3, NS5A), other cell-cycle related proteins and selected clinical data

Studies indicate that proteins of hepatitis C virus (HCV) disturb expression of cell-cycle-related proteins. A disturbed cell-cycle control is a hepatocellular carcinoma (HCC) risk factor in patients with HCV-related liver damage. The present study aimed to analyse the cellular expression of p21/Wafl/Cipl (p21) in long-lasting chronic hepatitis C (CH-C), its correlation with the key oncogenic HCV proteins (C, NS3, NS5A), other cell-cycle-related proteins (PCNA, Ki-67, cyclin D1, p53) and selected clinical data. Archival liver biopsies, obtained from patients with CH-C, normal livers, and hepatocellular carcinoma (HCC) specimens were analysed by immunocytochemistry and ImmunoMax technique. In CH-C overexpression of p21 protein was demonstrated. Positive correlations of p21 protein expression in CH-C involved age of the patients, grading, and liver steatosis. Moreover, expression of p21 correlated significantly with expression of p53 protein, of D1 cyclin and Ki-67. Although Ki-67 antigen was related to p21 expression, only Ki-67 expression proved to be directly related to liver staging. Expression of the NS3 protein, which prevailed in CH-C patients, manifested correlation with p21 expression, and that of cyclin D1. In presence of preserved potential for regeneration, overexpression of p21 indicates inhibition of cell cycle in hepatocytes, which probably plays a protective role for the chronically damaged cells. Out of the three HCV proteins only NS3 seems to affect control of p21 protein expression in in vivo infection. Nevertheless, the studies indicate that neither expression of p21 protein nor that of viral NS3 protein can serve as a marker of progression of CH-C to HCC in vivo.

Differential expression of cell cycle regulators in HCV-infection and related hepatocellular carcinoma

AIM

To investigate cell cycle proteins in chronic hepatitis C virus infection in order to analyze their role in the process of hepatocyte transformation and to characterize their prognostic properties.

METHODS

Subjects of the current study included 50 cases of chronic hepatitis C (CHC) without cirrhosis, 30 cases of CHC with liver cirrhosis (LC), and 30 cases of hepatitis C-related hepatocellular carcinoma (HCC) admitted to the Department of Hepato-Gastroenterology, Theodor Bilharz Research Institute (TBRI), Giza, Egypt. Fifteen wedge liver biopsies, taken during laparoscopic cholecystectomy, were also included as normal controls. Laboratory investigations including urine and stool analysis, liver function tests and prothrombin concentration; serologic markers for viral hepatitis and ultrasonography were done for all cases of the study together with immunohistochemical analysis using primary antibodies against Cyclin D1, Cyclin E, p21, p27 and Rb/p105 proteins.

RESULTS

Normal wedge liver biopsies didn't express Cyclin E or Rb/p105 immunostaining but show positive staining for Cyclin D1, p21 and p27. Cyclin D1 expressed nuclear staining that was sequentially increased from CHC to LC (P < 0.01) to HCC (P < 0.001) cases; meanwhile, Cyclin E revealed nuclear positivity only in the case of HCCs patients that was directly correlated to Rb/p105 immuno-reactivity. The expression of p21 and p27 was significantly increased in CHC and LC cases compared to normal controls and HCCs with no significant difference between well- and poorly-differentiated tumors. p21 showed only a nuclear pattern of staining, while, p27 presented with either cytoplasmic and/or nuclear reactivity in all studied cases. Correlation analysis revealed a direct relation between Cyclin D1 and p21 in CHC cases (P < 0.001), between Cyclin D1 and Cyclin E in HCCs (P < 0.01); however, an inverse relationship was detected between Cyclin D1 and p21 or p27 (P < 0.001) and between p21 and Rb/p105 (P < 0.05) in HCCs.

CONCLUSION

Upregulation of Cyclin D1 in CHC plays a vital role in the development and differentiation of HCC; while, Cyclin E may be a useful marker formonitoring tumor behavior. p21 and p27 can be used as predictive markers for HCC. Furthermore, higher expression of Rb/p105 as well as inverse relation with p21 and histologic grades suggests its important role in hepatic carcinogenesis.

Correlation between expression of p53, p21/WAF1, and MDM2 proteins and their prognostic significance in primary hepatocellular carcinoma

Background

Tumor Protein p53 (p53), cyclin-dependent kinase inhibitor 1A (p21/WAF1), and murine double minute 2 (MDM2) participate in the regulation of cell growth. Altered expression of these gene products has been found in malignant tumors and has been associated with poor prognosis. Our aim was to investigate the expression of the 3 proteins in hepatocellular carcinoma (HCC) and their prognostic significance.

Methods

We examined p53, p21/WAF1, and MDM2 expression in 181 pairs of HCC tissues and the adjacent hepatic tissues by performing immunohistochemistry and examined the expression of the 3 proteins in 7 pairs of HCC tissues and the adjacent hepatic tissues by using western blot analysis.

Results

The expression of p53, p21/WAF1, and MDM2 in the HCC tissues was significantly higher than those in the adjacent hepatic tissues (P < 0.05). A statistical correlation was observed between p53 and p21/WAF1 expression in HCC tissues (R = 0.195, P = 0.008). A statistical correlation was observed between expression of p53 and p21/WAF1 (R = 0.380, P = 0.000), p53 and MDM2 (R = 0.299, P = 0.000), p21/WAF1 and MDM2 (R = 0.285, P = 0.000) in 181 liver tissues adjacent to the tumor. Patients with a low pathologic grade HCC (I+II) had a higher tendency to express p53 on tumor cells than the patients with high pathologic grade HCC (III+IV) (P = 0.007). Survival analysis showed that positive p21/WAF1 expression or/and negative MDM2 expression in HCC was a predictor of better survival of patients after tumor resection (P < 0.05).

Conclusions

The proteins p53, p21/WAF1, and MDM2 were overexpressed in all the HCC cases in this study, and p53 and p21/WAF1 overexpression were positively correlated. The expression of p21/WAF1 and MDM2 can be considered as 2 useful indicators for predicting the prognosis of HCC.

p21 in cancer: intricate networks and multiple activities

One of the main engines that drives cellular transformation is the loss of proper control of the mammalian cell cycle. The cyclin-dependent kinase inhibitor p21 (also known as p21WAF1/Cip1) promotes cell cycle arrest in response to many stimuli. It is well positioned to function as both a sensor and an effector of multiple anti-proliferative signals. This Review focuses on recent advances in our understanding of the regulation of p21 and its biological functions with emphasis on its p53-independent tumour suppressor activities and paradoxical tumour-promoting activities, and their implications in cancer.

Tumor suppressor and hepatocellular carcinoma

A few signaling pathways are driving the growth of hepatocellular carcinoma. Each of these pathways possesses negative regulators. These enzymes, which normally suppress unchecked cell proliferation, are circumvented in the oncogenic process, either the over-activity of oncogenes is sufficient to annihilate the activity of tumor suppressors or tumor suppressors have been rendered ineffective. The loss of several key tumor suppressors has been described in hepatocellular carcinoma. Here, we systematically review the evidence implicating tumor suppressors in the development of hepatocellular carcinoma.

Failure of Lamivudine to Reverse Hepatitis B Virus-Associated Changes in ERK, Akt and Cell Cycle Regulatory Proteins

Background

Chronic infection with hepatitis B virus (HBV) is a major factor associated with the development of hepatocellular carcinoma, but the mechanism by which this occurs is unknown. Treatment of chronic hepatitis B with lamivudine results in virological suppression and histological improvement; however, the role of lamivudine in preventing the development of hepatocellular carcinoma is less well defined. We recently reported that replication of HBV in a cell-culture system was associated with the upregulation of pERK, pAkt, pc-Myc, nuclear cyclin B1, p21cip1 and p53 together with G2 cell cycle arrest.

Methods

In order to determine whether lamivudine is able to reverse the HBV-induced changes on signal transduction and cell cycle, we infected Huh7 cells with a recombinant adeno-HBV virus in the presence of 0–50 μM of lamivudine. Signal transduction and cell cycle regulatory proteins were analysed by western immunoblot.

Results

Although lamivudine was able to inhibit HBV replication, it failed to reverse the changes on ERK and Akt phosphorylation. Correspondingly, levels of phospho-GSK3β and p21cip1/waf1 were increased, as were cyclin D1, cyclin B1, p53 and pc-Myc.

Conclusions

Lamivudine was ineffective in reversing the HBV-induced changes in signal transduction pathways and cell cycle regulatory proteins, indicating that the HBV-infected cells remained primed for oncogenic transformation despite viral suppression.

P21/WAF1 is an independent survival prognostic factor for patients with hepatocellular carcinoma after resection

BACKGROUND/AIMS

The cyclin kinase inhibitor p21/WAF1 is regulated by p53-dependent or independent pathways and inhibits the action of proliferating cell nuclear antigen (PCNA). The prognostic role of p21/WAF1 in hepatocellular carcinoma (HCC) is ambiguous. To further clarify this, we examined the expression of three genes in HCC.

METHODS

A total of 122 resected HCC specimens were collected from 1987 to 1998. Expression of p21/WAF1, p53, and PCNA in HCC was analysed by immunohistochemistry.

RESULTS

Immunoreactivity was detectable for p21/WAF1 in 37%, and for p53 in 41.8% of HCCs. Positive expression of both genes does not relate to each other, but both are associated with a high PCNA labelling index (LI) (P<0.05) in tumour. p53 (+) is also associated with high serum alpha-foetoprotein (alphaFP) (P<0.001), tumour dedifferentiation (P=0.001) and advanced pathologic stages (P=0.017). However, p21/WAF1 (+) did not show clinicopathologic significance. Survival analysis indicated that poor prognostic factors were p21/WAF1 (-) (P=0.024), p53 (+) (P=0.008), high PCNA (P<0.001), tumour without capsule (P=0.001), poor tumour differentiation (P=0.004), advanced pathologic stage (P<0.001), and high serum alphaFP(P<0.001). Independent factors were p21/WAF1 expression, pathologic stage, and PCNA.

CONCLUSION

In HCC, increased proliferation index PCNA is significantly associated with positive p53 and p21/WAF1. But p21/WAF1 expression did not relate to p53 expression. P21/WAF1 (+) is a good event and serves as an independent survival prognostic factor for HCC, which is a novel finding apart from previous reports.

Telomere shortening and inactivation of cell cycle checkpoints characterize human hepatocarcinogenesis

Telomere shortening and inactivation of cell cycle checkpoints characterize carcinogenesis. Whether these molecular features coincide at specific stages of human hepatocarcinogenesis is unknown. The preneoplasia-carcinoma sequence of human HCC is not well defined. Small cell changes (SCC) and large cell changes (LCC) are potential precursor lesions. We analyzed hepatocellular telomere length, the prevalence of DNA damage, and the expression of p21 and p16 in biopsy specimens of patients with chronic liver disease (n = 27) that showed different precursor lesions and/or HCC: liver cirrhosis (n = 25), LCC (n = 26), SCC (n = 13), and HCC (n = 13). The study shows a decrease in telomere length in nondysplastic cirrhotic liver compared with normal liver and a further significant shortening of telomeres in LCC, SCC, and HCC. HCC had the shortest telomeres, followed by SCC and LCC. Hepatocytes showed an increased p21 labeling index (p21-LI) at the cirrhosis stage, which remained elevated in most LCC. In contrast, most SCC and HCC showed a strongly reduced p21-LI. Similarly, p16 was strongly expressed in LCC but reduced in SCC and not detectable in HCC. gammaH2AX-DNA-damage-foci were not detected in LCC but were present in SCC and more frequently in HCC. These data indicate that LCC and SCC represent clonal expansions of hepatocytes with shortened telomeres.

CONCLUSION

The inactivation of cell cycle checkpoints coincides with further telomere shortening and an accumulation of DNA damage in SCC and HCC, suggesting that SCC represent more advanced precursor lesions compared with LCC.

Overexpressed Id-1 is associated with a high risk of hepatocellular carcinoma development in patients with cirrhosis without transcriptional repression of p16

BACKGROUND

Inhibitor of differentiation/DNA binding protein 1 (Id-1) plays a pivotal role in the regulation of cell proliferation and carcinogenesis via inhibiting basic helix-loop-helix (HLH) transcription factors. Recently, Id-1 was found to repress p16 in tumorous tissue specimens including hepatocellular carcinoma (HCC), but its relevance in precancerous liver tissues is unknown.

METHODS

Id-1 expression in the liver tissue specimens of 112 patients with cirrhosis without HCC was studied by immunohistochemical analysis. Correlations were investigated between Id-1 expression and clinicopathologic features, the status of p16, and the risk of HCC occurrence.

RESULTS

A high expression of Id-1 was observed in 42 patients (38%). The level of Id-1 expression was not associated with clinical standard parameters or the status of p16 in cirrhotic tissue specimens. The cumulative incidence of HCC development was significantly higher in a group of patients with high Id-1 expression (P = 0.0008). Multivariate analysis revealed that increased Id-1 expression is an independent significant factor for the risk of HCC development in patients with cirrhosis (relative risk = 2.75, P = 0.003).

CONCLUSIONS

The results of the current study suggested that increased expression of Id-1 may play an important role in the early step of hepatocarcinogenesis, and might serve as a useful marker for determining patients with cirrhosis with a high risk of HCC occurrence.

Significant correlation of morphological remodeling in ulcerative colitis with disease duration and between elevated p53 and p21 expression in rectal mucosa and neoplastic development

Although a chronic inflammation-carcinoma sequence has been proposed in cases of longstanding ulcerative colitis (UC), the relationship of morphological alteration or remodeling of regenerated mucosa to carcinoma development is yet to be clarified. Therefore, mucosae of 49 resected rectae from individuals with UC were histologically and quantitatively analyzed, with regard to thickness and morphological parameters of crypts, in relation to the disease duration, clinical disease activity and neoplastic development. An immunohistochemical examination of Ki-67, p53, p21(WAF1) and ssDNA labeling was also included. Significant correlations of number, height, angle, fusion and Paneth cell metaplasia of crypts, as well as thickness of the muscularis mucosae, were revealed with disease duration, as confirmed by three-dimensional reconstructed image analysis. p53 and p21(WAF1)-positive cells increased with disease duration and were significantly more frequent in cases with neoplasia, suggesting more DNA damage. However, this was not the case for ssDNA labeling, assessed as an indicator of apoptosis. In general, histological changes and p53, p21(WAF1) and Ki-67 labeling were correlated. In conclusion, histological parameters for mucosal remodeling correlate well with UC duration, indicating accumulation of structural alterations. Accumulated damage to DNA, reflected by increased p53 and p21(WAF1) labeling indices, might be involved in cancer development, as well as longstanding inflammation.

Hepatocellular carcinoma--survival and clinical characteristics in relation to various histologic molecular markers in Western patients

BACKGROUND

Many genes participate in the regulation of cell proliferation and growth of tumor cells. Altered expression and loss of function of some of these gene products have been found in malignant tumors and correlated with progression and poor prognosis.

AIMS

Our aim was to correlate the expression of various molecular histologic markers with tumor characteristics and survival time of patients with hepatocellular carcinoma (HCC).

PATIENTS AND METHODS

Tumor tissues of 81 patients with HCC were investigated immunohistochemically for the expression of cellular proliferation markers Mib1 (Ki67) and c-erbB-2 (HER2/neu), cellcycle markers (p53, mdm2 and p21), CD81 (TAPA1), a marker shown to be associated with metastasis, and human leukocyte antigen (HLA)-DR expression, involved in immunological antigen presentation.

RESULTS

p21 was expressed in a higher percentage (83.3 vs. 50%, P=0.014) in undifferentiated histological tumor grades (Edmondson Steiner G3 vs. G1/G2). HCC in patients with enlarged lymph nodes expressed HLA-DR in a higher percentage (28.6%) than tumors without lymph node enlargement (5.7%, P=0.006). Patients with distant metastases were less likely to express CD 81 (11.1%) on tumor cells than patients without distant metastases (38.3%, P=0.0335). No other correlation with clinical or tumor characteristics or molecular histologic markers investigated was found. P53 accumulating patients showed a worse survival than patients with tumors p53 non-accumulating (median 4.1 months vs. median 9.3 months, P=0.01798). Neither the expression nor the non-expression of proliferation, cell cycle, immunologic or cell adhesion markers was associated with differences in survival. However, patients with a low expression of cell cycle marker mdm2 survived significantly longer (median 9.4 months) as compared with patients with high expression (median 3.9 months).

CONCLUSION

Our results suggest that p53 nuclear accumulation and mdm2 high expression are associated with poor survival in patients withHCC. Furthermore, patients with enlarged lymph nodes had HLA-DR-positive tumors more frequently and patients with distant metastases had tumors with CD81 expression less often.

Similarities and differences in hepatitis B and C virus induced hepatocarcinogenesis

Hepatocellular carcinoma (HCC), the major manifestation of primary liver cancer, is one of the most frequent and malignant diseases worldwide. Among other environmental factors, hepatitis viruses, as the hepatitis B (HBV) and hepatitis C (HCV) viruses, are to be listed in the etiology of HCC. Both of these viruses cause a wide spectrum of clinical manifestations, ranging from healthy carrier state to acute and chronic hepatitis, cirrhosis and HCC. HBV and HCV are different viruses in structure: HBV contains a DNA genome which replicates through an RNA intermediate and requires an active viral reverse transcriptase (RT) polymerase enzyme, while HCV is an RNA virus which has no RT activity and replicates on the cellular membrane by RNA replication. In this review we discuss how these two biologically diverse viruses use common pathways to induce hepatocarcinogenesis despite their significant structural and viral cycle differences. A summary is also given of several observable common and different features. Direct integration of HBV viral sequences into the host genome increases the genomic instability, which does not occur in HCV infection. However, viral proteins may directly play a significant role in the induction of carcinogenesis by both viruses.

The Cdk inhibitor p21 is required for necrosis, but it inhibits apoptosis following toxin-induced liver injury

Liver injury and repair were examined in wild type, p21Waf1/Cip1, and p27Kip1-deficient mice following carbon tetrachloride (CCl4) administration. In wild type liver, p21 expression is induced in a biphasic manner following injection of CCl4, with an early peak of p21 expression occurring in pericentral hepatocytes at 6 h, prior to evidence of injury, and a second peak succeeding regenerative proliferation. In contrast, p27 is present throughout the quiescent liver, but its expression decreases following CCl4 injection. Surprisingly, p21-deficient animals were resistant to CCl4-induced necrotic injury, indicating that rapid induction of p21 in pericentral hepatocytes following CCl4 injection contributes to subsequent necrosis. Expression of cytochrome P450 2E1, which plays an essential role in CCl4-induced necrotic injury, was not affected in p21-deficient mice. Although they had the least injury, p21-deficient mice had the highest levels of hepatic proliferation that correlated with increases in hyperphosphorylated retinoblastoma protein and Cyclin A gene expression. Increased replication in p21-deficient livers was counteracted by an increase in hepatocyte apoptosis as detected by caspase-3 activation. p21 plays distinct and opposing roles regulating hepatocyte survival during injury and subsequent repair, with early induction of p21 contributing to necrotic injury and later expression to cessation of proliferation and hepatocyte survival.