Over-expression and lack of retinoblastoma protein are associated with tumor progression and metastasis in hepatocellular carcinoma

The Role and Clinical Implications of the Retinoblastoma (RB)-E2F Pathway in Gastric Cancer

Gastric cancer is the most common malignant tumor in the digestive tract, with very high morbidity and mortality in developing countries. The pathogenesis of gastric cancer is a complex biological process mediated by abnormal regulation of proto-oncogenes and tumor suppressor genes. Although there have been some in-depth studies on gastric cancer at the molecular level, the specific mechanism has not been fully elucidated. RB family proteins (including RB, p130, and p107) are involved in cell cycle regulation, a process that largely depends on members of the E2F gene family that encode transcriptional activators and repressors. In gastric cancer, inactivation of the RB-E2F pathway serves as a core transcriptional mechanism that drives cell cycle progression, and is regulated by cyclins, cyclin-dependent kinases, cyclin-dependent kinase inhibitors, p53, Helicobacter pylori and some other upstream molecules. The E2F proteins are encoded by eight genes (i.e. E2F1 to E2F8), each of which may play a specific role in gastric cancer. Interestingly, a single E2F such as E2F1 can activate or repress transcription, and enhance or inhibit cell proliferation, depending on the cell environment. Thus, the function of the E2F transcription factor family is very complex and needs further exploration. Importantly, the presence of H. pylori in stomach mucosa may affect the RB and p53 tumor suppressor systems, thereby promoting the occurrence of gastric cancer. This review aims to summarize recent research progress on important roles of the complex RB-E2F signaling network in the development and effective treatment of gastric cancer.

MicroRNA‑153‑3p suppresses retinoblastoma cell growth and invasion via targeting the IGF1R/Raf/MEK and IGF1R/PI3K/AKT signaling pathways

Mounting evidence has demonstrated that microRNAs (miRNAs or miRs) play significant roles in various types of human tumors, including retinoblastoma (RB). However, the biological role and regulatory mechanisms of miRNAs in RB remain to be fully elucidated. The present study was designed to identify the regulatory effects of miRNAs in RB and the underlying mechanisms. Differentially expressed miRNAs in RB tissue were screened out based on the Gene Expression Omnibus (GEO) dataset, GSE7072, which revealed that miR-153 in particular, displayed the highest fold change in expression. It was identified that miR-153 was significantly downregulated in RB tissues, and its downregulation was closely associated with a larger tumor base and differentiation. Functional analysis revealed that the overexpression of miR-153 inhibited RB cell proliferation, migration and invasion, and promoted the apoptosis of WERI-RB-1 and Y79 cells. In addition, insulin-like growth factor 1 receptor (IGF1R) was identified as a target of miR-153 in RB cells. More importantly, it was demonstrated that miR-153 upregulation inhibited the expression of its target gene, IGF1R, which inhibited the activation of the Raf/MEK and PI3K/AKT signaling pathways. Collectively, the present study demonstrates for the first time, to the best of our knowledge, that miR-153 functions as a tumor suppressor in RB by targeting the IGF1R/Raf/MEK and IGF1R/PI3K/AKT signaling pathways. Collectively, the findings presented herein demonstrate that miR-153 targets IGF1R and blocks the activation of the Raf/MEK and PI3K/AKT signaling pathway, thus preventing the progression of RB. Thus, this miRNA may serve as a novel prognostic biomarker and therapeutic target for RB.

MicroRNA-192 promotes the development of nasopharyngeal carcinoma through targeting RB1 and activating PI3K/AKT pathway

BACKGROUND

The dysregulation of microRNAs (miRNAs) has been found in diseases and cancers, including microRNA-192 (miR-192). This study was designed to investigate the role of miR-192 in nasopharyngeal carcinoma (NPC) progression.

METHODS

The expression levels of miR-192 and some genes were assessed by qRT-PCR and Western blot. The function of miR-192 was investigated through MTT, Transwell, and dual-luciferase reporter assays.

RESULTS

The expression of miR-192 was increased in NPC tissues, and high miR-192 expression predicted poor prognosis in NPC patients. Functionally, upregulation of miR-192 promoted NPC cell migration, invasion, and growth. Furthermore, miR-192 activated EMT and PI3K/AKT pathway to regulate NPC progression. In addition, miR-192 directly targeted RB1 and suppressed its expression in NPC. Moreover, overexpression of RB1 weakened the promoted effect of miR-192 in NPC.

CONCLUSION

miR-192 promoted cell viability and metastasis in NPC through suppressing RB1 expression and activating PI3K/AKT pathway.

Preclinical Activity of Ribociclib in Squamous Cell Carcinoma of the Head and Neck

Cell-cycle pathway impairments resulting in CDK4 and 6 activation are frequently observed in human papillomavirus (HPV)-negative squamous cell carcinoma of the head and neck (SCCHN). We investigated the activity of ribociclib, a CDK4/6 inhibitor, in SCCHN models with the aim of identifying predictive biomarkers of response. HPV-negative or HPV-positive SCCHN cell lines (n = 8) and patient-derived tumor xenograft (PDTX) models (n = 6) were used. The models were classified according to their sensitivity to ribociclib to investigate potential predictive biomarkers. Ribociclib had a cytostatic effect in some HPV-negative SCCHN models but had no effect in HPV-positive models. In SCCHN cell lines and PDTXs, the retinoblastoma (Rb) protein expression level correlated with ribociclib activity. Rb knockdown was, however, not sufficient to block G₀-G₁ arrest induced by ribociclib in Detroit-562 where p107, p130, and Forkhead BOX M1 (FOXM1) were also implicated in ribociclib activity. Cell lines harboring epithelial-to-mesenchymal transition (EMT) features were less sensitive to ribociclib than those with an epithelial phenotype. Rb downregulation induced EMT in our Rb-expressing SCCHN cell lines. However, ribociclib still had significant activity in one PDTX model with high Rb and vimentin expression, suggesting that the presence of vimentin alone is not enough to induce ribociclib resistance. These findings suggest that CDK4/6 inhibitors should be investigated in patients with HPV-negative SCCHN with high Rb expression and an epithelial phenotype. Although these biomarkers are not predictive in all cases, they may enrich the population that could benefit from CDK4/6 inhibitors.

NRBE3 promotes metastasis of breast cancer by down-regulating E-cadherin expression

NRBE3 acts as an E3 ligase of RB to promote RB's polyubiquitination and degradation. In addition, NRBE3 is up-regulated in human breast cancer (BC) tissues. However, how NRBE3 functions in BC is unknown. Here, we show that up-regulation of NRBE3 is correlated with lymphatic metastasis in human BC tissues. Ectopic expression of NRBE3 promotes migration and invasion in BC cells. Accordingly, knockdown of NRBE3 inhibits migration and invasion in BC cells. Depletion of NRBE3 inhibits lung metastasis of BC cells in vivo. Knock-down of NRBE3 causes increase of E-cadherin protein levels. Interestingly, Flag-NRBE3 decreases E-cadherin level in RB-expressing and RB-null BC cells, demonstrating that there exist RB-independent mechanisms for NRBE3-mediated E-cadherin expression regulation. However, the E3 ligase deficient deletion mutant Flag-NRBE3 (ΔU-box) modestly decreases E-cadherin level in RB-expressing cells, indicating that NRBE3 controls E-cadherin expression mainly through RB-dependent pathways in RB-expressing cells. We further demonstrate that NRBE3 inhibits the transcription of E-cadherin in BC cells. Significantly, NRBE3 expression is negatively correlated with E-cadherin expression in human BC tissues and cell lines. Collectively, we demonstrate that NRBE3 promotes metastasis of BC and possesses the potential as a therapeutic target in BC.

MiR-661 promotes tumor invasion and metastasis by directly inhibiting RB1 in non small cell lung cancer

BACKGROUND

Aberrant microRNA expression has been implicated in metastasis of cancers. MiR-661 accelerates proliferation and invasion of breast cancer and ovarian cancer, while impedes that of glioma. Its role in non small cell lung cancer (NSCLC) and underlying mechanism are worthy elucidation.

METHODS

Expression of miR-661 was measured with real-time PCR in both NSCLC tissues and cell lines. The effects of miR-661 on migration, invasion and metastasis capacity of NSCLC were evaluated using wound healing, transwell assay and animal models. Dual reporter luciferase assay and complementary experiments were performed to validate RB1 as a direct target of miR-661 for participation in the progression of NSCLC.

RESULTS

MiR-661 was upregulated in NSCLC tissues as compared to paired adjacent tissues and associated with shorter overall survival. Furthermore, miR-661 promoted proliferation, migration and metastasis of NSCLC. Then, we identified RB1 as a direct target of miR-661 through which miR-661 affected EMT process and metastasis of NSCLC. RB1 interacted with E2F1 and both could mediate EMT process in NSCLC.

CONCLUSION

MiR-661 promotes metastasis of NSCLC through RB/E2F1 signaling and EMT events, thus may serves as a negative prognostic factor and possible target for treatment of NSCLC patient.

RB Loss Promotes Prostate Cancer Metastasis

RB loss occurs commonly in neoplasia but its contributions to advanced cancer have not been assessed directly. Here we show that RB loss in multiple murine models of cancer produces a prometastatic phenotype. Gene expression analyses showed that regulation of the cell motility receptor RHAMM by the RB/E2F pathway was critical for epithelial-mesenchymal transition, motility, and invasion by cancer cells. Genetic modulation or pharmacologic inhibition of RHAMM activity was sufficient and necessary for metastatic phenotypes induced by RB loss in prostate cancer. Mechanistic studies in this setting established that RHAMM stabilized F-actin polymerization by controlling ROCK signaling. Collectively, our findings show how RB loss drives metastatic capacity and highlight RHAMM as a candidate therapeutic target for treating advanced prostate cancer. Cancer Res; 77(4); 982-95. ©2016 AACR.

CAS (CSE1L) signaling pathway in tumor progression and its potential as a biomarker and target for targeted therapy

CSE1L (chromosome segregation 1-like protein), also named as CAS (cellular apoptosis susceptibility protein), is highly expressed in most cancer types. CSE1L/CAS is a multiple functional protein that plays roles in apoptosis, cell survival, chromosome assembly, nucleocytoplasmic transport, microvesicle formation, and cancer metastasis; some of the functions are explicitly correlated. CSE1L is also a cancer serum biomarker. The phosphorylation of CAS is regulated by the extracellular signal-regulated kinase (ERK). The RAS/RAF/MAPK/ERK signaling pathways are the essential targets of most targeted cancer drugs, thus serum phosphorylated CSE1L may be a potential biomarker for monitoring drug resistance in targeted therapy. CSE1L can regulate Ras-induced ERK phosphorylation. CSE1L also regulates the expression and phosphorylation of CREB (cAMP response element binding protein) and MITF (microphthalmia-associated transcription factor) and is thus involved in the melanogenesis and progression of melanoma. CAS is an exosome/microvesicle membrane protein. Tumor cells consistently secrete microvesicles and tumor-derived microvesicles may be accumulated around tumors. Therefore, microvesicle membrane CSE1L may be a potential target for the development of high-efficacy antibody-drug conjugates (ADCs) for cancer therapy. This review will focus on CSE1L expression in cancers, its relationship to Ras/ERK and cAMP/PKA signaling pathways in melanoma development, its potential for the development of ADCs and tumor imaging reagents, and secretory phosphorylated CSE1L for monitoring the emergence of drug resistance in targeted cancer therapy.

The Rb-E2F transcriptional regulatory pathway in tumor angiogenesis and metastasis

The retinoblastoma tumor suppressor protein Rb plays a major role in regulating G1/S transition and is a critical regulator of cell proliferation. Rb protein exerts its growth regulatory properties mainly by physically interacting with the transcriptionally active members of the E2F transcription factor family, especially E2Fs 1, 2, and 3. Given its critical role in regulating cell proliferation, it is not surprising that Rb is inactivated in almost all tumors, either through the mutation of Rb gene itself or through the mutations of its upstream regulators including K-Ras and INK4. Recent studies have revealed a significant role for Rb and its downstream effectors, especially E2Fs, in regulating various aspects of tumor progression, angiogenesis, and metastasis. Thus, components of the Rb-E2F pathway have been shown to regulate the expression of genes involved in angiogenesis, including VEGF and VEGFR, genes involved in epithelial-mesenchymal transition including E-cadherin and ZEB proteins, and genes involved in invasion and migration like matrix metalloproteinases. Rb has also been shown to play a major role in the functioning of normal and cancer stem cells; further, Rb and E2F appear to play a regulatory role in the energy metabolism of cancer cells. These findings raise the possibility that mutational events that initiate tumorigenesis by inducing uncontrolled cell proliferation might also contribute to the progression and metastasis of cancers through the mediation of the Rb-E2F transcriptional regulatory pathway. This review highlights these recent studies on tumor promoting functions of the Rb-E2F pathway.

Phospho-Rb (Ser780) as a biomarker in patients with cervical lymph node metastases from an unknown primary tumour: a retrospective cohort study

OBJECTIVES

Cervical lymph node metastases from an unknown primary tumour are a heterogeneous disease entity with various clinical features. There are many controversies regarding treatment methods and treatment response predictions. Therefore, we examined the prognostic significance of biomarkers in patients with cervical metastasis of unknown primary tumour.

DESIGN

A molecular study of retrospective cohorts.

SETTING

University teaching hospital.

MAIN OUTCOME MEASURES

Metastatic cervical lymph nodes of 36 patients with cervical unknown primary metastasis of squamous cell carcinoma were assessed by in situ hybridisation for human papillomavirus and immunohistochemistry for p16, retinoblastoma protein (phospho-Ser780), hypoxia-inducible factor-1α, glucose transporter 1 and carbonic anhydrase 9 expression. Clinicopathological factors and biomarkers were analysed for their associations with disease-free survival and overall survival.

RESULTS

Univariate analysis showed that nodal extracapsular spread was associated with poor overall survival (P = 0.049), nodal-positive retinoblastoma protein staining were significantly associated with poor outcomes of both disease-free survival (P = 0.035) and overall survival (P = 0.019), Multivariate analysis revealed that nodal positivity of retinoblastoma protein and nodal extracapsular spread were the significant predictors of overall survival (P = 0.049, hazard ratio = 6.21, 95% confidence interval = 1.01-38.35 and P = 0.037, hazard ratio = 4.34, 95% confidence interval = 1.09-17.21, respectively).

CONCLUSION

The retinoblastoma protein expression of metastatic lymph nodes represents an independent prognostic indicator in patients with cervical metastasis of unknown primary tumour.

The Complex Relationship between Liver Cancer and the Cell Cycle: A Story of Multiple Regulations

The liver acts as a hub for metabolic reactions to keep a homeostatic balance during development and growth. The process of liver cancer development, although poorly understood, is related to different etiologic factors like toxins, alcohol, or viral infection. At the molecular level, liver cancer is characterized by a disruption of cell cycle regulation through many molecular mechanisms. In this review, we focus on the mechanisms underlying the lack of regulation of the cell cycle during liver cancer, focusing mainly on hepatocellular carcinoma (HCC). We also provide a brief summary of novel therapies connected to cell cycle regulation.

Retinoblastoma 94 enhances radiation treatment of esophageal squamous cell carcinoma in vitro and in vivo

We performed the study to investigate whether adenovirus-mediated retinoblastoma 94 (RB94) gene transfer could enhance radiation treatment of esophageal squamous cell carcinoma (ESCC) in vitro and in vivo. ESCC cells (Kyse150 cell line) were cultivated in vitro and tumors originated from the cell line were propagated as xenografts in nude mice. Treatment with Ad-RB94 and/or ionizing radiation (IR) was carried out both in vitro and in vivo with Ad-LacZ control vector and blank control. Cell viability, cell cycle distribution, cell apoptosis, tumor growth and transfected gene expression were evaluated and tumor degeneration was analyzed. The data of quantification real-time PCR assays and immunohistochemistry staining using RB antibody indicated that RB94 was efficiently transfected into Kyse150 cells. In vitro, data of cell growth assay indicated that treatment with Ad-RB94 improved radiation treatment of Kyse150 cells. Tumor xenograft studies, pathological analysis of H.E. staining and Ki67 staining suggested transfecting RB94 enhanced tumor regression induced by radiation treatment in vivo. In addition, data of Annexin V, TUNEL and cell cycle distribution assays proposed combination treatment effectively induced cell apoptosis and cell cycle arresting in G2/M phase. In conclusion, transferring RB94 gene by the adenoviral vector enhances radiation treatment of ESCC.

Cellular mechanisms of tumour suppression by the retinoblastoma gene

The retinoblastoma (RB) tumour suppressor gene is functionally inactivated in a broad range of paediatric and adult cancers, and a plethora of cellular functions and partners have been identified for the RB protein. Data from human tumours and studies from mouse models indicate that loss of RB function contributes to both cancer initiation and progression. However, we still do not know the identity of the cell types in which RB normally prevents cancer initiation in vivo, and the specific functions of RB that suppress distinct aspects of the tumorigenic process are poorly understood.

Rb depletion results in deregulation of E-cadherin and induction of cellular phenotypic changes that are characteristic of the epithelial-to-mesenchymal transition

The retinoblastoma tumor suppressor protein (Rb) is mutated or expressed at very low levels in several tumor types, including retinoblastoma and osteosarcoma, as well as small cell lung, colon, prostate, bladder, and breast carcinomas. Loss or reduction of Rb expression is seen most commonly in high-grade breast adenocarcinomas, suggesting that a relationship may exist between loss of Rb function and a less-differentiated state, increased proliferation, and high metastatic potential. In this study, we found that knockdown of Rb by small interfering RNA in MCF7 breast cancer cells disrupts cell-cell adhesion and induces a mesenchymal-like phenotype. The epithelial-to-mesenchymal transition (EMT), a key event in embryonic morphogenesis, is implicated in the metastasis of primary tumors. Additionally, Rb is decreased during growth factor- and cytokine-induced EMT and overexpression of Rb inhibits the EMT in MCF10A human mammary epithelial cells. Ectopic expression and knockdown of Rb resulted in increased or reduced expression of E-cadherin, which is specifically involved in epithelial cell-cell adhesion. Other EMT-related transcriptional factors, including Slug and Zeb-1, are also induced by Rb depletion. Furthermore, we confirmed that Rb binds to an E-cadherin promoter sequence in association with the transcription factor activator protein-2alpha. Finally, in breast cancer specimens, we observed a concurrent down-regulation of Rb and E-cadherin expression in mesenchymal-like invasive cancers. These findings suggest that Rb inactivation contributes to tumor progression due to not only loss of cell proliferation control but also conversion to an invasive phenotype and that the inhibition of EMT is a novel tumor suppressor function of Rb.

Expression of altered retinoblastoma protein inversely correlates with tumor invasion in gastric carcinoma

AIM: To investigate the clinical and pathological significance of altered retinoblastoma (Rb) encoding protein (pRb) in gastric carcinoma.

METHODS: Expression of altered pRb was analyzed in 91 patients with gastric adenocarcinoma by immunohistochemistry.

RESULTS: Sixty-five percent (59/91) of the tumors were positively stained and the staining in tumor nuclei of gastric carcinoma ranged 0%-90%. Moreover, strong expression of altered pRb was found in 35% (6/17), 24% (5/21), 17% (8/46) and 0% (0/7) of T1, T2, T3 and T4 gastric carcinomas, respectively. Altered pRb expression was inversely correlated with the depth of tumor invasion (P = 0.047). Degree of immunoreactivity had no significant correlation with tumor grade, node metastasis and distant metastasis. In terms of prognostic significance, univariate analysis showed that poor differentiation [41 (66.1%) vs 34 (42.5%) P = 0.051], advanced tumor stage (P < 0.001) and weakly altered pRb expression [17 (80.5%) vs 58 (49.6%) P = 0.044] were associated with worse prognosis in these patients. However, multivariate analysis revealed that advanced tumor stage was the only independent poor prognostic factor (P < 0.001).

CONCLUSION: The mutation of Rb gene is frequent in gastric carcinoma. The expression of altered pRb inversely correlates with tumor invasion and is not an independent prognostic marker in gastric adenocarcinoma.

RB family members as predictive and prognostic factors in human cancer

The retinoblastoma family members--pRb, pRb2/p130 and p107--are tumor suppressor genes involved in controlling four major cellular processes: growth arrest, apoptosis, differentiation and angiogenesis. Molecular genetic studies have identified abnormalities of these tumor suppressor genes in a large proportion of human cancers. These genetic alterations have emerged as significant factors in the pathogenesis and progression of many types of tumors and are therefore likely to provide relevant information to assess risk in cancer patients. There is a pressing clinical need to identify prognostic and predictive factors for patients with cancer, because there is an undeniable importance in being able to determine which patients will have a favorable outcome without further therapy (prognostic factor) and which will need some additional treatment (predictive factor). This review examines the predictive and/or prognostic role of each retinoblastoma family member in human cancer.

Tumorigenic study on hepatocytes coexpressing SV40 with Ras

A model of neoplastic transformation by the combination of SV40 large T antigen (LT), SV40 small T antigen (ST), oncogenic Ras, and human telomerase reverse trasncriptase subunit (hTERT) has become established and replicated in primary human fibroblasts, however, there is no report on human hepatocytes. Here we use cell transplantation model, and show that transplantation of human hepatocytes of HL-7702 and HL-7703 expressing Ha-RasV12 and SV40 LT into subrenal capsule of immunodeficient mice results in fully malignant tumors, in contrast to conventional subcutaneous injections where tumors fail to develop. In GM-847 cell study, we have found that hTERT is not required for tumorigenic growth in subrenal capsule transplantation, however, it is required in subcutaneous injection assay. These results demonstrate that Human hepatocytes can be transformed under kidney capsule by coexpressing SV40 LT and Ha-RasV12, neither hTERT nor protein phosphatase 2A (PP2A) inhibition are required for malignant transformation, a gene which increases cell survival in the subcutaneous injection model is not required for tumorigenic growth in subrenal capsule.

Papillary microcarcinomas of the thyroid with preoperatively detectable lymph node metastasis show significantly higher aggressive characteristics on immunohistochemical examination

OBJECTIVES

We recently demonstrated that papillary microcarcinomas with preoperatively detectable node metastasis in the lateral compartment on ultrasonography (clinically apparent metastasis) show worse postoperative relapse-free survival than those with no metastasis or metastasis that could not be detected preoperatively, but was confirmed by pathological examination after surgery (occult metastasis). In this study, we investigated difference in the aggressive characteristics of microcarcinoma of this type from various perspectives.

MATERIALS AND METHODS

We immunohistochemically examined the expression of cell proliferating markers, Ki-67, cyclin D1, p27, and retinoblastoma gene product (pRb), apoptotic markers, single-strand DNA (ssDNA), and metastatic suppressor, kangai-1 (KAI-1) for 19 microcarcinoma patients with clinically apparent metastasis, 14 patents with occult metastasis, and 22 patients without metastasis.

RESULTS

Cases of clinically apparent metastasis showed increased cyclin D1 expression together with decreased p27 expression and higher levels of pRb and Ki-67 expression. Furthermore, ssDNA expression was higher and bcl-2 expression was lower in these cases, while KAI-1 expression was significantly reduced. There was no significant difference in the expression of these proteins between cases demonstrating no and occult metastases.

CONCLUSION

These findings suggest that cases of clinically apparent metastasis show significantly higher growth based on cell proliferating activity, apoptosis, and expression of metastatic suppressor than those demonstrating no or occult metastases.

Tissue microarray for high-throughput analysis of gene expression profiles in hepatocellular carcinoma

AIM: To study the expression profiles of HBsAg, HBcAg, p21^WAF1/CIP1 (p21), Rb genes in hepatocellular carcinoma (HCC) and to investigate their roles in the hepatocar-cinogenesis.

METHODS: HCC tissue microarray containing 120-min tissues of 40 HCC cases was constructed. HBsAg, HBcAg, p21 and Rb proteins were immunohistochemically stained by streptavidin-peroxidase conjugated method (S-P). The expression loss of these genes in cancerous, para-cancerous tissues and adjacent normal liver tissues of 40 HCCs were comparatively examined.

RESULTS: The positive rate of HBsAg expression in cancerous tissues of 40 HCCs was 7.5%, which was lower than that in para-cancerous and adjacent normal liver tissues (χ² =12.774, P<0.01; χ² = 18.442, P<0.01). The positive rate of HBcAg expression in cancerous tissues of 40 HCCs was 20.0%, which was also lower than that in para-cancerous and adjacent normal liver tissues (χ² = 9.482, P<0.01; χ² = 14.645, P<0.01). p21 protein deletion rate in cancerous tissues of 40 HCCs was 27.5%, which was higher than that in para-cancerous and adjacent normal liver tissues (χ² = 7.439, P<0.01; χ² = 11.174, P<0.01). p21 protein deletion correlated remarkably with the pathological grade of HCC (χ² = 0.072, P<0.05). Rb protein deletion rate in cancerous tissues of 40 HCCs was 42.5%, which was also higher than that in para-cancerous and adjacent normal liver tissues (χ² = 10.551, P<0.01; χ² = 18.353, P<0.01). Rb protein deletion rate did not correlate remarkably with tumor size or pathological grade of HCC (χ² = 0.014, P>0.05; χ² = 0.017, P>0.05).

CONCLUSION: Expression deletion of HBsAg, HBcAg, p21 and Rb proteins in HCCs may play important roles in the carcinogenesis of HCC. Tissue microarray is an effective high-throughput technique platform for cancer research.

Immunohistochemical assessment of angiogenesis in hepatocellular carcinoma and surrounding cirrhotic liver tissues

AIM: To investigate whether vascular endothelial growth factor (VEGF) was over-expressed in hepatocellular carcinoma (HCC) or in surrounding cirrhotic liver tissues.

METHODS: Immunohistochemistry was performed to investigate the expression of VEGF proteins in HCC tissues from 105 consecutive patients undergoing curative resection for HCC. The immunostaining results and related clinicopathologic materials were analyzed with statistical methods. Kaplan–Meier method was used to calculate survival curves, and Log-rank test was performed to compare differences in survival rates of the patients with positive HCC staining and negative VEGF.

RESULTS: VEGF-positive expression was found in 72 of 105 HCC patients (68.6%). Capsular infiltration (P = 0.005), vascular invasion (P = 0.035) and intrahepatic metastasis (P = 0.008) were observed more frequently in patients with VEGF-positive expression than in those with VEGF-negative expression. Kaplan–Meier curves showed that VEGF-positive expression was associated with a shorter overall survival (P = 0.014). VEGF-positive expression was found in 47 of tissues 68 HCC (69.1%), and VEGF-positive expression was found in 54 of 68 surrounding cirrhotic liver tissues (79.4%). VEGF-positive expression was significantly higher in surrounding cirrhotic liver tissues than in HCC (P = 0.017).

CONCLUSION: VEGF may play an important role in the angiogenesis and prognosis of HCC, as well as in the angiogenesis of liver cirrhosis.

Retinoblastoma susceptibility gene product pRB activates hypoxia-inducible factor-1 (HIF-1)

Hypoxia-inducible factor-1 alpha (HIF-1alpha) constitutes a regulatory subunit of HIF-1, a major transcriptional activator of genes that coordinate physiological and pathological responses towards hypoxia. In order to identify novel interaction partners of HIF-1alpha we have applied T7 phage display system and identified a domain inherent in the retinoblastoma protein (pRB). The interaction between pRB and HIF-1alpha was confirmed by in vitro experiments and in transfected cells. Thereby, an HIF-1alpha domain spanning amino acids 530-694 was mapped to be required for pRB binding. Overexpression of pRB provoked transcriptional activation of HIF-1alpha under normoxia. Furthermore, the domain of pRB identified to bind HIF-1alpha in vitro is sufficient to cause HIF-1alpha transcriptional activation with the further notion that phosphorylation deficient pRB shows stronger HIF-1alpha transactivation. Using ChIP analysis, we show that HIF-1alpha responsive elements (HREs) are precipitated using alpha-pRB antibodies. Additionally, a functional interaction between pRB and HIF-1alpha is confirmed by showing that HIF-1alpha reverses the transcription repressor function of pRB.

pRb2/p130, vascular endothelial growth factor, p27(KIP1), and proliferating cell nuclear antigen expression in hepatocellular carcinoma: their clinical significance

Hepatocarcinoma (HCC) is the fifth most common cancer, with more than one million fatalities occurring annually worldwide. Multiple risk factors are associated with HCC disease etiology, the highest incidence being in patients with chronic hepatitis B virus and hepatitis C virus, although other factors such as genetic makeup and environmental exposure are involved. Multiple genetic alterations including the activation of oncogenes and inactivation of tumor suppressor genes are required for malignancy in human cancers and are correlated with increased stages of carcinogenesis and further tumor progression. In this study of 21 HCC patients, we analyzed pRb2/p130, vascular endothelial growth factor (VEGF), p27((KIP1)), and proliferating cell nuclear antigen as potential HCC molecular biomarkers. In our sample set, we found that p27((KIP1)) was absent. Univariate survival analysis showed that proliferating cell nuclear antigen expression (diffuse staining >50% of positive cells in tumor) was confirmed as a significant HCC prognostic biomarker for determining patient survival agreeing with previous studies (P = 0.0126, log-rank test). Lower pRb2/p130 expression was associated to a borderline P value of inverse correlation with tumor malignancy and to a positive correlation with respect to the time from HCC diagnosis (Spearman coefficient = 0.568; P < 0.05). Conversely, higher VEGF expression was associated with a poor survival (P = 0.0257, log-rank test). We demonstrate for the first time that pRb2/p130 is inversely correlated with VEGF expression and tumor aggressiveness (P < 0.05) in p27((KIP1))-negative HCC patients. pRb2/p130 and VEGF expression are independent from tumor staging, suggesting their possible role as independent prognostic molecular biomarkers in HCC. Furthermore, we have evidence that VEGF together with pRb2/p130 may act as new HCC biomarkers in a p27((KIP1))-independent manner. Additional studies with larger numbers of patient data would allow the use of multivariable techniques and would be able to further identify patients with poorer survival.

Expression profiling in hepatocellular carcinoma with intrahepatic metastasis: identification of high-mobility group I(Y) protein as a molecular marker of hepatocellular carcinoma metastasis

Hepatocellular carcinoma (HCC) is one of the most common and aggressive human malignancies. Its high mortality rate is mainly a result of intra-hepatic metastases. To investigate the detailed genetic mechanisms in cancer metastasis, we compared the expression profiles of 20 HCCs with intrahepatic metastasis and 10 HCCs without intrahepatic metastasis using an oligonucleotide array. Of the approximately 12,600 genes that were analyzed, we identified 34 genes whose expression levels were significantly correlated with intrahepatic metastasis (P<0:05). Of these genes, we further investigated the expression of high-mobility group I(Y) [HMG-I(Y)] protein. Real-time quantitative reverse transcription polymerase chain reaction (RT-PCR) confirmed that HMG-I(Y) was upregulated in HCC with intrahepatic metastasis, compared to its level in HCC without intrahepatic metastasis. Further immunohistochemical examination of HMG-I(Y) revealed a significant overexpression in HCC with intrahepatic metastasis, compared with that in HCC without intrahepatic metastasis (P<0:05). These results indicate that the molecular signatures of HCC with intrahepatic metastasis and of HCC without intrahepatic metastasis are clearly different. HMG-I(Y) expression was associated with intrahepatic metastasis and may be a predictive marker of HCC intrahepatic metastasis.

Genomic analysis reveals RhoC as a potential marker in hepatocellular carcinoma with poor prognosis

Hepatocellular carcinoma (HCC) is one of the most malignant human tumours because of its high incidence of metastasis. The mechanisms underlying the metastasis of HCC, however, remain poorly understood. In this study, we performed cDNA microarray analysis to profile gene expression patterns in two subtypes of HCC, solitary large HCC (SLHCC) and nodular HCC (NHCC), which differ significantly in the incidence of metastasis. Among 668 genes that were differentially expressed, we focused on RhoC, whose expression was significantly decreased in SLHCC compared to NHCC. The expression of RhoC in HCC and pericarcinomatous liver tissues (PCLT) was analysed at both the mRNA and protein levels by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting. In addition, immunohistochemistry was also performed on 94 cases of HCC with follow-up information. Collectively, our data indicate that the expression of RhoC significantly increased in HCC compared to PCLT; extrahepatic metastatic lesions expressed significantly higher levels of RhoC than the corresponding intrahepatic HCC tissues. There is a highly significant correlation of the RhoC expression levels with tumour vein invasion, number of tumour nodes and the status of differentiation. Significantly, the HCC patients with RhoC-positive expression had shorter survival than those with RhoC-negative expression. Together, our findings suggest a strong correlation between the expression of RhoC and HCC metastasis, implicating RhoC as a potential prognosis marker and therapeutic target for HCC.

A novel liver-specific zona pellucida domain containing protein that is expressed rarely in hepatocellular carcinoma

We currently identified a liver-specific gene that encodes a novel zona pellucida (ZP) domain-containing protein named liver-specific ZP domain-containing protein (LZP). The full-length complementary DNA (cDNA) of human LZP has 2,255 bp with a complete open reading frame (ORF) of 1,635 bp. The gene is localized on chromosome 10q21.3 and spans 40 kb with 9 encoding exons and 8 introns. The deduced protein sequence has 545 amino acid residues, with an N-terminal signal peptide followed by 3 epidermal growth factor (EGF)-like domains and a ZP domain in C-terminal section. Interestingly, human LZP is expressed specifically in liver out of 23 tissues examined, and its mouse counterpart was detected at very early stage during embryo development. Moreover, LZP can be secreted into blood, albeit the protein was localized mainly on the nuclear envelop of hepatocytes. Most importantly, LZP is down-regulated in hepatocellular carcinoma (HCC) and HCC cell lines; meanwhile, the decreased level of hLZP messenger RNA (mRNA) could, at least in some HCC samples, be related to the methylation status of the putative LZP promoter. However, overexpression of hLZP in HCC cell line SMMC-7721 and human liver cell line L02 by stable cell transfection did not inhibit cell growth, implying that the down-regulation of hLZP in HCC might be a consequence of the dedifferentiation involved in hepatocarcinogenesis. In conclusion, these data suggest that LZP is a liver-specific protein involved possibly in hepatocellular function and development, and the protein could be used as potential negative biomarker for HCC pathologic diagnosis.

Alterations of RB1, p53 and Wnt pathways in hepatocellular carcinomas associated with hepatitis C, hepatitis B and alcoholic liver cirrhosis

Major etiologic factors associated with human hepatocellular carcinomas (HCCs) include infection with hepatitis C (HCV) and hepatitis B virus (HBV), excess alcohol intake and aflatoxin B(1) exposure. While the G-->T p53 mutation at codon 249 has been identified as a genetic hallmark of HCC caused by aflatoxin B(1), the genetic profile associated with other etiologic factors appears to be less distinctive. In our study, we screened HCCs resulting from HCV infection (51 cases), HBV infection (26 cases) or excess alcohol intake (23 cases) for alterations in genes involved in the RB1 pathway (p16(INK4a), p15(INK4b), RB1, CDK4 and cyclin D1), the p53 pathway (p53, p14(ARF) and MDM2) and the Wnt pathway (beta-catenin, APC). Alterations of the RB1 pathway, mainly p16(INK4a) methylation, loss of RB1 expression and cyclin D1 amplification, were most common (69-100% of cases). There was a significant correlation between loss of RB1 expression and RB1 methylation. All 24 HCCs with RB1 promoter methylation lacked RB1 expression, while none of the 67 cases with RB1 expression exhibited RB1 methylation (p < 0.0001), suggesting that promoter methylation is a major mechanism of loss of RB1 expression in HCCs. Alterations of the p53 pathway consisted mostly of p53 mutations or p14(ARF) promoter methylation (20-48%). Mutations of the p53 gene were found at a similar frequency (13-15%) in all etiologic groups, without any consistent base change or hot spot. Mutations of beta-catenin were found in 13-31% of cases, while no APC mutations were detected in any of the HCCs analyzed. With the exception of only 3 of 39 cases (8%), cyclin D1 amplification and beta-catenin mutations were mutually exclusive, supporting the view that cyclin D1 is a target of the Wnt signaling pathway. Overall, the RB1, p53 and Wnt pathways were commonly affected in HCCs of different etiology, probably reflecting common pathogenetic mechanisms, i.e., chronic liver injury and cirrhosis, but tumors associated with alcoholism had more frequent alterations in the RB1 and p53 pathways than those caused by HCV infection.

Spectrum of molecular changes during hepatocarcinogenesis induced by DEN and other chemicals in Fisher 344 male rats [Mechanisms of Ageing and Development 123 (2002) 1665-1680]

Unlike other tissues such as breast, colon and renal cell carcinoma, it is not an easy task to single out any representative oncogene or tumor suppressor genes in the development of hepatocellular carcinoma (HCC), which play a pivotal role. To investigate putatively altered main pathways in HCC, F344 male rats were treated with a single injection of N-nitrosodiethylamine (DEN), followed by either twice/week injections of nodularin for 10 weeks or thioacetamide (TAA) in drinking water for 39 weeks. p53 expression was dramatic in both hepatocytes and mesenchymal cells after a single injection of DEN, however, PCR-SSCP assay could not detect any p53 mutation during the development of hepatocellular adenoma (HCA). The data indicate that wtp53 response was mostly for removal of damaged cells during the initiation of carcinogenesis. When treated with DEN-TAA, induction of gankyrin expression during hepatic fibrosis preceded the loss of pRB protein, accompanied with significant expressions of G1phase cyclins and CDKs. Moreover, p16(INK4A) exon 1 was hypermethylated during the development of poorly differentiated HCCs. These changes would result in complete inactivation of the pRB regulatory pathway during hepatocarcinogenesis. Induction of TGF-beta1 expression with loss of its receptor expression occurred rapidly in the altered hepatocytes by DEN-nodularin treatment.

CONCLUSION

Therefore, escape from TGF-beta1 induced apoptosis and severe degradation of pRB protein during the early stage of carcinogenesis can perform a symphony to proliferate and to transform the altered hepatocytes to tumor cells. Inactivation of p16(INK4A) and p53 genes at the later stage of carcinogenesis would endow HCC with malignancy, which is highly resistant to any therapeutic trials.

Predicting hepatitis B virus-positive metastatic hepatocellular carcinomas using gene expression profiling and supervised machine learning

Hepatocellular carcinoma (HCC) is one of the most common and aggressive human malignancies. Its high mortality rate is mainly a result of intra-hepatic metastases. We analyzed the expression profiles of HCC samples without or with intra-hepatic metastases. Using a supervised machine-learning algorithm, we generated for the first time a molecular signature that can classify metastatic HCC patients and identified genes that were relevant to metastasis and patient survival. We found that the gene expression signature of primary HCCs with accompanying metastasis was very similar to that of their corresponding metastases, implying that genes favoring metastasis progression were initiated in the primary tumors. Osteopontin, which was identified as a lead gene in the signature, was over-expressed in metastatic HCC; an osteopontin-specific antibody effectively blocked HCC cell invasion in vitro and inhibited pulmonary metastasis of HCC cells in nude mice. Thus, osteopontin acts as both a diagnostic marker and a potential therapeutic target for metastatic HCC.

Spectrum of molecular changes during hepatocarcinogenesis induced by DEN and other chemicals in Fischer 344 male rats

Unlike other tissues such as breast, colon and renal cell carcinoma, it is not an easy task to single out any representative oncogene or tumor suppressor genes in the development of hepatocellular carcinoma (HCC), which play a pivotal role. To investigate putatively altered main pathways in HCC, F344 male rats were treated with a single injection of N-nitrosodiethylamine (DEN), followed by either twice/week injections of nodularin for 10 weeks or thioacetamide (TAA) in drinking water for 39 weeks. p53 expression was dramatic in both hepatocytes and mesenchymal cells after a single injection of DEN, however, PCR-SSCP assay could not detect any p53 mutation during the development of hepatocellular adenoma. The data indicate that wtp53 response was mostly for removal of damaged cells during the initiation of carcinogenesis. When treated with DEN-TAA, induction of gankyrin expression during hepatic fibrosis preceded the loss of pRB protein, accompanied with significant expressions of G1 phase cyclins and CDKs. Moreover, p16(INK4A) exon 1 was hypermethylated during the development of poorly differentiated HCCs. These changes would result in complete inactivation of the pRB regulatory pathway during hepatocarcinogenesis. Induction of TGF-beta1 expression with loss of its receptor expression occurred rapidly in the altered hepatocytes by DEN-nodularin treatment.

CONCLUSION

Therefore, escape from TGF-beta1 induced apoptosis and severe degradation of pRB protein during the early stage of carcinogenesis can perform a symphony to proliferate and to transform the altered hepatocytes to tumor cells. Inactivation of p16(INK4A) and p53 genes at the later stage of carcinogenesis would endow HCC with malignancy, which is highly resistant to any therapeutic trials.

High frequency of promoter hypermethylation of RASSF1A and p16 and its relationship to aflatoxin B1-DNA adduct levels in human hepatocellular carcinoma

Epigenetic changes in gene expression due to extensive CpG island methylation is now accepted as the main cause of inactivation of the p16 gene. More recently, it has been suggested that the human ras association domain family (RASSF) 1 gene, cloned from the lung tumor-suppressor locus 3p21.3, also may be inactivated by methylation. It consists of two major alternative transcripts, RASSF1A and RASSF1C. Epigenetic inactivation of isoform A was observed in several carcinomas and tumor cell lines. In this study, promoter hypermethylation of RASSF1A and p16 was investigated in 83 hepatocellular carcinoma (HCC) tissue samples from Taiwan and in two HCC cell lines (Hep3B and HepG2). High frequencies (85% and 47%, respectively) of methylation of the CpG island promoters of RASSF1A and p16 were found in the HCC tissues. The methylation of RASSF1A also was detected in Hep3B cells but not in HepG2 cells; p16 was not methylated in either cell line. Methylation status was determined in 12 normal control liver tissues and 10 adjacent nontumor tissues. No methylation was found in normal liver control tissues for both RASSF1A and p16; methylation was detected in one of 10 and seven of 10 adjacent nontumor tissue sampless for p16 and RASSF1A, respectively, in subjects with positive tumors. These data indicate that aberrant methylation of the CpG island promoters of both genes is a frequent occurrence in hepatocarcinogenesis. The high frequency of RASSF1A methylation in adjacent tissues suggests that this may be an early event. The relationship between methylation status and clinical parameters and tumor markers, including DNA damage resulting from aflatoxin B(1) (AFB(1)), an environmental carcinogen, and p53 status, also was analyzed. A statistically significant association was found between RASSF1A methylation status and the level of AFB(1)-DNA adducts in tumor tissues. No association was found between methylation status and p53 status. These results suggest the hypothesis that exposure to environmental carcinogens may be involved in altered methylation of genes involved in cancer development.

Proliferative marker Ki-67 in gallbladder carcinomas: high expression level predicts early recurrence after surgical resection

To evaluate the prognostic value of proliferative maker Ki-67, its expression was determined immunohistochemically in 37 gallbladder carcinomas (GBCs). A high Ki-67 index was significantly correlated with tumor lymphatic invasion (P=0.007) and vascular invasion (P=0.04). High Ki-67 index group and low Ki-67 index group showed different clinical courses. Five patients who experienced recurrences in high Ki-67 index group developed their recurrent diseases within one year after surgery and died soon after recurrence, while the recurrences (five cases) in low Ki-67 index group were distributed all stages after surgery. In conclusion, high Ki-67 index predicts early recurrence after surgery for GBCs.

Analysis of differentially expressed genes in hepatocellular carcinoma using cDNA arrays

Hepatocellular carcinoma (HCC) is characterized by multiple somatic mutations, including DNA rearrangements, that affect many cell-growth regulatory pathways. Many genes differentially expressed in HCC have been reported previously, but the patterns of expression varied significantly between patients who bore different risk factors for HCC. To identify genes whose differential expression could serve as a "signature" for diagnosis and prognosis of HCC, we performed analyses of differentially expressed genes in three cases of HCC with different risk factors using the Atlas Human Cancer cDNA Expression Arrays. Among all 597 genes present on the array, only three were found to be coordinately differentially expressed in all three HCC cases, in agreement with published data. These three genes, Cu/Zn superoxide dismutase, osteonectin/secreted protein acidic and rich in cysteine, and matrix metalloproteinase 14, could serve as candidates for the HCC "signature." Ten genes were found to be coordinately differentially expressed in only two of three tested HCC cases. On the other hand, many genes that had been reported previously as differentially expressed in HCC failed to show the described pattern of expression in this group. The results of this study confirm the great variability in gene-expression patterns in HCC and establish the utility of the array technology for identifying both the HCC signature genes and individual gene-expression patterns for purposes of patient-oriented therapy.

Reduced p21(WAF1/CIP1) expression is an early event in gallbladder carcinogenesis and is of prognostic significance for patients with carcinomas of the gallbladder

The molecular basis underlying the development and progression of gallbladder carcinoma (GBC) remains poorly understood. To evaluate the roles of p21(WAF1/CIP1) and p53 in gallbladder carcinogenesis and to assess their prognostic significance for patients with GBC, we used immunohistochemistry to examine the expression of p21(WAF1/CIP1) and p53 protein in a series of surgically resected specimens, including normal epithelia, precancerous lesions adenoma, and dysplasia, and carcinomas of the gallbladder. Reduced p21(WAF1/CIP1) expression was frequently observed in carcinomas (18 of 37 lesions; 49%), and even in precancerous lesions adenomas (3 of 7; 43%) and dysplasias (5 of 5; 100%). p53 overexpression was detected in 43% of the adenomas, 60% of the dysplasias and 57% of the carcinomas. There was an inverse relationship between p21(WAF1/CIP1) and p53 expression in GBCs (P =.01). Survival analysis indicated that reduced p21(WAF1/CIP1) expression was significantly associated with shortened disease-free and overall survival (P =.04 and.03, respectively) for patients with stages II to IV GBCs. These observations suggest that reduced p21(WAF1/CIP1) expression and p53 overexpression contribute to GBC from an early stage and that determination of p21(WAF1/CIP1) expression in surgically resected specimens would add prognostic information to conventional pathologic examinations for patients with advanced-stage GBC.

Hepatocellular carcinoma--cause, treatment and metastasis

In the recent decades, the incidence of hepatocellular carcinoma (HCC) has been found to be increasing in males in some countries. In China, HCC ranked second of cancer mortality since 1990s. Hepatitis B and C viruses (HBV and HCV) and dietary aflatoxin intake remain the major causative factors of HCC. Surgery plays a major role in the treatment of HCC, particularly for small HCC. Down-staging unresectable huge HCC to smaller HCC and followed by resection will probably be a new approach for further study. Liver transplantation is indicated for small HCC, however, some issues remain to be solved. Different modes of regional cancer therapy for HCC have been tried. Systemic chemotherapy has been disappointing in the past but the future can be promising. Biotherapy, such as cytokines, differentiation inducers, anti-angiogenic agents, gene therapy and tumor vaccine will probably play a role, particularly in the prevention of tumor recurrence. HCC invasiveness is currently the major target of study. Tremendous works have been done at the molecular level, which will provide clues for biomarker of HCC progression as well as targets for intervention.

Sequential changes in hepatocarcinogenesis induced by diethylnitrosamine plus thioacetamide in Fischer 344 rats: induction of gankyrin expression in liver fibrosis, pRB degradation in cirrhosis, and methylation of p16(INK4A) exon 1 in hepatocellular carcinoma

To clarify the sequential changes in pRB and p16 during different stages of hepatocarcinogenesis such as fibrosis, cirrhosis, hepatocellular adenoma (HCA), and hepatocellular carcinoma (HCC), male Fischer 344 rats were singly injected with diethylnitrosamine (DEN), immediately followed with phenobarbital for 1 wk and then thioacetamide (TAA) for 39 wk in drinking water. Rats were killed at 9, 20, 30, and 40 wk after DEN initiation and changes of pRB level, p16 gene hypermethylation, and in vivo gankyrin expression were examined. Histologic examination showed stepwise appearances of fibrosis, cirrhosis, HCA, and HCC at weeks 9, 20, 30, and 40, respectively. Hypermethylation of p16 exon 1 was not found until HCA but appeared in 50% of the rats with HCC accompanied by complete loss of its mRNA expression. The amount of glutathione S-transferase--gankyrin bound to pRB and pRB degradation in the liver depended on the concentration of gankyrin and incubation time. Gankyrin expression preceded pRB degradation in liver cirrhosis. In conclusion, gankyrin expression induced in liver fibrosis accelerated the degradation of pRB during liver cirrhosis, and inactivation of p16 exon 1 by DNA hypermethylation occurred during the progression of tumor cells to poorly differentiated HCC. Inactivation of pRB and/or p16 resulted in complete loss of regulation in the cell-division cycle during early and late stages, respectively, of hepatocarcinogenesis. Mol. Carcinog. 30:138--150, 2001.

Reduced p21(WAF1/CIP1) protein expression is predominantly related to altered p53 in hepatocellular carcinomas

To investigate the relationship between the expression of p21(WAF1/CIP1) protein and p53 status and the possible role of the two proteins in hepatocellular carcinomas (HCCs), we examined the expression of p21(WAF1/CIP1) and p53 immunohistochemically in 81 tumours from 65 patients with hepatocellular carcinoma. p21(WAF1/CIP1) protein was absent from 59 of 81 tumours (72.8%), and altered p53 expression was found in 43 (53.1%). p21(WAF1/CIP1) expression was significantly associated with p53 status (P = 0.0008); 38 of 59 tumours lacking p21(WAF1/CIP1) protein were accompanied by altered p53 expression. Further analyses showed that p21(WAF1/CIP1) expression was inversely correlated with p53 expression in hepatitis C virus (HCV)-related HCCs, but not in HBV-related hepatocellular carcinomas and hepatocellular carcinomas without viral infection. All 11 tumours with intrahepatic metastasis showed altered p21(WAF1/CIP1) or p53 expression. In contrast, no intrahepatic metastasis was found in any of the 17 tumours without abnormal expression of either of the two proteins. These results suggest that: (1) different modes of p21(WAF1/CIP1) regulation are involved in HCCs differing in their hepatitis viral infection status, and p21(WAF1/CIP1) expression appears to be predominantly related to altered p53 in HCV-related HCCs; (2) disruption of the p53-p21(WAF1/CIP1) cell-cycle-regulating pathway may contribute to malignant progression of HCC.

Loss of p16(INK4) protein, alone and together with loss of retinoblastoma protein, correlate with hepatocellular carcinoma progression

To investigate the role of p16(INK4) protein absence in hepatocellular carcinoma progression, we examined p16(INK4) expression immunohistochemically in 81 primary and 23 metastatic lesions of hepatocellular carcinoma, in which retinoblastoma protein status had been determined. p16(INK4) protein was absent from 44% of the total of 104 tumors. The rate of p16(INK4) absence was twice as high in metastatic lesions (74%) compared with primary lesions (36%) (P=0.001). Loss of p16(INK4) and/or retinoblastoma protein was significantly associated with decreased tumor differentiation, vascular invasion and metastasis. In conclusion, p16(INK4) protein absence, alone and together with loss of retinoblastoma protein, contributes to hepatocellular carcinoma progression.