PTEN/MMAC1 mutations in hepatocellular carcinomas: somatic inactivation of both alleles in tumors

Targeting EGFR/PI3K/AKT/mTOR Signaling in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) poses a significant global health concern, with its incidence steadily increasing. The development of HCC is a multifaceted, multi-step process involving alterations in various signaling cascades. In recent years, significant progress has been made in understanding the molecular signaling pathways that play central roles in hepatocarcinogenesis. In particular, the EGFR/PI3K/AKT/mTOR signaling pathway in HCC has garnered renewed attention from both basic and clinical researchers. Preclinical studies in vitro and in vivo have shown the effectiveness of targeting the key components of this signaling pathway in human HCC cells. Thus, targeting these signaling pathways with small molecule inhibitors holds promise as a potential therapeutic option for patients with HCC. In this review, we explore recent advancements in understanding the role of the EGFR/PI3K/AKT/mTOR signaling pathway in HCC and assess the effectiveness of targeting this signaling cascade as a potential strategy for HCC therapy based on preclinical studies.

Gender Differences in a Mouse Model of Hepatocellular Carcinoma Revealed Using Multi-Modal Imaging

The worldwide incidence of hepatocellular carcinoma (HCC) continues to rise, in part due to poor diet, limited exercise, and alcohol abuse. Numerous studies have suggested that the loss or mutation of PTEN plays a critical role in HCC tumorigenesis through the activation of the PI3K/Akt signaling axis. The homozygous knockout of PTEN in the livers of mice results in the accumulation of fat (steatosis), inflammation, fibrosis, and eventually progression to HCC. This phenotype bears a striking similarity to non-alcoholic steatohepatitis (NASH) which is thought to occupy an intermediate stage between non-alcoholic fatty liver disease (NAFLD), fibrosis, and HCC. The molecular and physiological phenotypes that manifest during the transition to HCC suggest that molecular imaging could provide a non-invasive screening platform to identify the hallmarks of HCC initiation prior to the presentation of clinical disease. We have carried out longitudinal imaging studies on the liver-specific PTEN knockout mouse model using CT, MRI, and multi-tracer PET to interrogate liver size, steatosis, inflammation, and apoptosis. In male PTEN knockout mice, significant steatosis was observed as early as 3 months using both magnetic resonance spectroscopy (MRS) and computed tomography (CT). Enhanced uptake of the apoptosis tracer 18F-TBD was also observed in the livers of male PTEN homozygous knockout mice between 3 and 4 months of age relative to heterozygous knockout controls. Liver uptake of the inflammation tracer [18F]4FN remained relatively low and constant over 7 months in male PTEN homozygous knockout mice, suggesting the suppression of high-energy ROS/RNS with PTEN deletion relative to heterozygous males where the [18F]4FN liver uptake was elevated at early and late time points. All male PTEN homozygous mice developed HCC lesions by month 10. In contrast to the male cohort, only 20% (2 out of 10) of female PTEN homozygous knockout mice developed HCC lesions by month 10. Steatosis was significantly less pronounced in the female PTEN homozygous knockout mice relative to males and could not accurately predict the eventual occurrence of HCC. As with the males, the [18F]4FN uptake in female PTEN homozygous knockout mice was low and constant throughout the time course. The liver uptake of 18F-TBD at 3 and 4.5 months was higher in the two female PTEN knockout mice that would eventually develop HCC and was the most predictive imaging biomarker for HCC in the female cohort. These studies demonstrate the diagnostic and prognostic role of multi-modal imaging in HCC mouse models and provide compelling evidence that disease progression in the PTEN knockout model is highly dependent on gender.

Oncogenic Activity of Solute Carrier Family 45 Member 2 and Alpha-Methylacyl-Coenzyme A Racemase Gene Fusion Is Mediated by Mitogen-Activated Protein Kinase

Chromosome rearrangement is one of the hallmarks of human malignancies. Gene fusion is one of the consequences of chromosome rearrangements. In this report, we show that gene fusion between solute carrier family 45 member 2 (SLC45A2) and alpha-methylacyl-coenzyme A racemase (AMACR) occurs in eight different types of human malignancies, with frequencies ranging from 45% to 97%. The chimeric protein is translocated to the lysosomal membrane and activates the extracellular signal-regulated kinase signaling cascade. The fusion protein promotes cell growth, accelerates migration, resists serum starvation-induced cell death, and is essential for cancer growth in mouse xenograft cancer models. Introduction of SLC45A2-AMACR into the mouse liver using a sleeping beauty transposon system and somatic knockout of phosphatase and TENsin homolog (Pten) generated spontaneous liver cancers within a short period. Conclusion: The gene fusion between SLC45A2 and AMACR may be a driving event for human liver cancer development.

MicroRNA-129-5p promotes proliferation and metastasis of hepatocellular carcinoma by regulating the BMP2 gene

Hepatocellular carcinoma (HCC) is a malignant tumor that poses a serious threat to human health. Due to its occult onset and rapid development, HCC is a challenge to diagnose early and effectively treat, and thus patients with HCC often have an unfavorable prognosis. MicroRNA (miR)-129 and its target gene play an important role in the regulation of various diseases. Therefore, the aim of the present study was to investigate the role and mechanism of action for miR-129-5p in the development of HCC. Quantitative results of clinical samples analyzed using reverse transcription-quantitative PCR suggested that miR-129-5p had a significantly lower expression level in tumoral tissues compared with corresponding peritumoral tissues. Overexpression of miR-129-5p in HCC cells was performed using a transfection technique, followed by MTT, Transwell, invasion and wound healing assays to detect the effect of miR-129-5p on the cell cytotoxicity and metastasis of liver cancer in vitro. The downstream target gene of miR-129-5p, bone morphogenetic protein 2 (BMP2), was determined using a luciferase reporter assay. Overexpression of miR-129-5p played a vital role in decreasing cytotoxicity and promoting metastasis of HCC, which may be attributed to its inhibitory effect on the expression of its target gene, BMP2. In clinical samples, miR-129-5p expression levels were found to be negatively correlated with BMP2 and closely associated with HCC metastasis and infiltration. Collectively, the results suggested that miR-129-5p may contribute to proliferation and metastasis of HCC through its target gene, BMP2, and thus may be a potential novel therapeutic target for the treatment of HCC.

Circulating tumor DNA/circulating tumor cells and the applicability in different causes induced hepatocellular carcinoma

In 2015, liquid biopsy was rated one of the top 10 breakthrough technologies of the year by MIT Technology Review. Liquid biopsy is a type of in vitro diagnostic method involving a noninvasive blood test. It is also a breakthrough technology used to detect tumors and cancers and assist in therapeutic strategies. The most widely used markers are circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA). Primary carcinoma of the liver is a malignancy of hepatocytes or intrahepatic biliary epithelial cells. The most common type of liver cancer is hepatocellular carcinoma (HCC), the causes of which mainly include infection with hepatitis B virus (HBV) and/or hepatitis C virus (HCV), alcohol abuse, aflatoxicosis, and nonalcoholic fatty liver disease/ nonalcoholic steatohepatitis. As there are few typical clinical characteristics during the early stage of the disease, early diagnosis of HCC is very challenging. However, CTCs and ctDNA carry tumor-specific information. Therefore, the detection and analysis of CTCs and ctDNA can provide evidence for the early diagnosis of HCC and guide treatment. Furthermore, several studies have indicated that different inducers of HCC cause different DNA mutations, and accordingly, detection of specific mutations in ctDNA will facilitate the determination of the HCC type and help physicians provide distinctive therapies.

PTEN Tumor-Suppressor: The Dam of Stemness in Cancer

PTEN is one of the most frequently inactivated tumor suppressor genes in cancer. Loss or variation in PTEN gene/protein levels is commonly observed in a broad spectrum of human cancers, while germline PTEN mutations cause inherited syndromes that lead to increased risk of tumors. PTEN restrains tumorigenesis through different mechanisms ranging from phosphatase-dependent and independent activities, subcellular localization and protein interaction, modulating a broad array of cellular functions including growth, proliferation, survival, DNA repair, and cell motility. The main target of PTEN phosphatase activity is one of the most significant cell growth and pro-survival signaling pathway in cancer: PI3K/AKT/mTOR. Several shreds of evidence shed light on the critical role of PTEN in normal and cancer stem cells (CSCs) homeostasis, with its loss fostering the CSC compartment in both solid and hematologic malignancies. CSCs are responsible for tumor propagation, metastatic spread, resistance to therapy, and relapse. Thus, understanding how alterations of PTEN levels affect CSC hallmarks could be crucial for the development of successful therapeutic approaches. Here, we discuss the most significant findings on PTEN-mediated control of CSC state. We aim to unravel the role of PTEN in the regulation of key mechanisms specific for CSCs, such as self-renewal, quiescence/cell cycle, Epithelial-to-Mesenchymal-Transition (EMT), with a particular focus on PTEN-based therapy resistance mechanisms and their exploitation for novel therapeutic approaches in cancer treatment.

The biology of Hepatocellular carcinoma: implications for genomic and immune therapies

Hepatocellular carcinoma (HCC), the most common type of primary liver cancer, is a leading cause of cancer-related death worldwide. It is highly refractory to most systemic therapies. Recently, significant progress has been made in uncovering genomic alterations in HCC, including potentially targetable aberrations. The most common molecular anomalies in this malignancy are mutations in the TERT promoter, TP53, CTNNB1, AXIN1, ARID1A, CDKN2A and CCND1 genes. PTEN loss at the protein level is also frequent. Genomic portfolios stratify by risk factors as follows: (i) CTNNB1 with alcoholic cirrhosis; and (ii) TP53 with hepatitis B virus-induced cirrhosis. Activating mutations in CTNNB1 and inactivating mutations in AXIN1 both activate WNT signaling. Alterations in this pathway, as well as in TP53 and the cell cycle machinery, and in the PI3K/Akt/mTor axis (the latter activated in the presence of PTEN loss), as well as aberrant angiogenesis and epigenetic anomalies, appear to be major events in HCC. Many of these abnormalities may be pharmacologically tractable. Immunotherapy with checkpoint inhibitors is also emerging as an important treatment option. Indeed, 82% of patients express PD-L1 (immunohistochemistry) and response rates to anti-PD-1 treatment are about 19%, and include about 5% complete remissions as well as durable benefit in some patients. Biomarker-matched trials are still limited in this disease, and many of the genomic alterations in HCC remain challenging to target. Future studies may require combination regimens that include both immunotherapies and molecularly matched targeted treatments.

Mutations and deregulation of Ras/Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR cascades which alter therapy response

The Ras/Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR cascades are often activated by genetic alterations in upstream signaling molecules such as receptor tyrosine kinases (RTK). Certain components of these pathways, RAS, NF1, BRAF, MEK1, DUSP5, PP2A, PIK3CA, PIK3R1, PIK3R4, PIK3R5, IRS4, AKT, NFKB1, MTOR, PTEN, TSC1, and TSC2 may also be activated/inactivated by mutations or epigenetic silencing. Upstream mutations in one signaling pathway or even in downstream components of the same pathway can alter the sensitivity of the cells to certain small molecule inhibitors. These pathways have profound effects on proliferative, apoptotic and differentiation pathways. Dysregulation of components of these cascades can contribute to: resistance to other pathway inhibitors, chemotherapeutic drug resistance, premature aging as well as other diseases. This review will first describe these pathways and discuss how genetic mutations and epigenetic alterations can result in resistance to various inhibitors.

Targeted therapy for hepatocellular carcinoma: novel agents on the horizon

Hepatocellular carcinoma (HCC) is the most common liver cancer, accounting for 90% of primary liver cancers. In the last decade it has become one of the most frequently occurring tumors worldwide and is also considered to be the most lethal of the cancer systems, accounting for approximately one third of all malignancies. Although the clinical diagnosis and management of early-stage HCC has improved significantly, HCC prognosis is still extremely poor. Furthermore, advanced HCC is a highly aggressive tumor with a poor or no response to common therapies. Therefore, new effective and well-tolerated therapy strategies are urgently needed. Targeted therapies have entered the field of anti-neoplastic treatment and are being used on their own or in combination with conventional chemotherapy drugs. Molecular-targeted therapy holds great promise in the treatment of HCC. A new therapeutic opportunity for advanced HCC is the use of sorafenib (Nexavar). On the basis of the recent large randomized phase III study, the Sorafenib HCC Assessment Randomized Protocol (SHARP), sorafenib has been approved by the FDA for the treatment of advanced HCC. Sorafenib showed to be able to significantly increase survival in patients with advanced HCC, establishing a new standard of care. Despite this promising breakthrough, patients with HCC still have a dismal prognosis, as it is currently the major cause of death in cirrhotic patients. Nevertheless, the successful results of the SHARP trial underscore the need for a comprehensive understanding of the molecular pathogenesis of this devastating disease. In this review we summarize the most important studies on the signaling pathways implicated in the pathogenesis of HCC, as well as the newest emerging drugs and their potential use in HCC management.

Roles of the Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR pathways in controlling growth and sensitivity to therapy-implications for cancer and aging

Dysregulated signaling through the Ras/Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR pathways is often the result of genetic alterations in critical components in these pathways or upstream activators. Unrestricted cellular proliferation and decreased sensitivity to apoptotic-inducing agents are typically associated with activation of these pro-survival pathways. This review discusses the functions these pathways have in normal and neoplastic tissue growth and how they contribute to resistance to apoptotic stimuli. Crosstalk and commonly identified mutations that occur within these pathways that contribute to abnormal activation and cancer growth will also be addressed. Finally the recently described roles of these pathways in cancer stem cells, cellular senescence and aging will be evaluated. Controlling the expression of these pathways could ameliorate human health.

Expansion of hepatic tumor progenitor cells in Pten-null mice requires liver injury and is reversed by loss of AKT2

BACKGROUND & AIMS

The tumor suppressor PTEN inhibits AKT2 signaling; both are aberrantly expressed in liver tumors. We investigated how PTEN and AKT2 regulate liver carcinogenesis. Loss of PTEN leads to spontaneous development of liver tumors from progenitor cells. We investigated how the loss of PTEN activates liver progenitor cells and induces tumorigenesis.

METHODS

We studied mice with liver-specific disruptions in Pten and the combination of Pten and Akt2 to investigate mechanisms of liver carcinogenesis.

RESULTS

PTEN loss leads to hepatic injury and establishes selective pressure for tumor-initiating cells (TICs), which proliferate to form mixed-lineage tumors. The Pten-null mice had increasing levels of hepatic injury before proliferation of hepatic progenitors. Attenuation of hepatic injury by deletion of Akt2 reduced progenitor cell proliferation and delayed tumor development. In Pten/Akt2-null mice given 3,5-diethoxycarbonyl-1,4 dihydrocollidine (DDC), we found that the primary effect of AKT2 loss was attenuation of hepatic injury and not inhibition of progenitor-cell proliferation in response to injury.

CONCLUSIONS

Liver carcinogenesis in Pten-null mice requires not only the transformation of TICs but selection pressure from hepatic injury and cell death, which activates TICs. Further research is required to elucidate the mechanism for hepatic injury and its relationship with TIC activation.

Molecular classification of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most frequent tumour derived from the malignant transformation of hepatocytes. It is well established that cancer is a disease of the genome and, as in other types of solid tumours, a large number of genetic and epigenetic alterations are accumulated during the hepatocarcinogenesis process. Recent developments using comprehensive genomic tools have enabled the identification of the molecular diversity in human HCC. Consequently, several molecular classifications have been described using different approaches and important progress has been made particularly with the transcriptomic, genetic, chromosomal, miRNA and methylation profiling. On the whole, all these molecular classifications are related and one of the major determinants of the identified subgroups of tumours are gene mutations found in oncogenes and tumour suppressors. However, the full understanding of the HCC molecular classification requires additional comprehensive studies using both genomic and pathway analyses. Finally, a refinement of the molecular classification of HCC, taking into account the geographical and genetic diversity of the patients, will be essential for an efficient design of the forthcoming personalized clinical treatments.

Loss of heterozygosity on 10q23 is involved in metastatic recurrence of hepatocellular carcinoma

We performed loss of heterozygosity (LOH) analysis on five chromosomal arms (1p, 3p, 9p, 10q, 17p) in hepatocellular carcinoma (HCC). Univariate analyses of 80 patients who underwent liver transplantation demonstrated significant correlations between cancer recurrence and the following variables: LOH on 3p26, LOH on 10q23, LOH on 17p13, tumor diameter > or = 5 cm, number of tumors > or = 4, histologic Grade 3, alpha-fetoprotein (AFP) > or = 400 ng/mL, American Joint Committee on Cancer (AJCC) pT classification, and portal invasion. Patients with LOH on 10q23 exhibited a significantly higher 3-year recurrence rate (38.9%vs 11.9%, P = 0.0009). Multivariate analysis identified LOH on 10q23, histologic Grade 3, tumor nodules > or = 4, and AFP > or = 400 ng/mL as the risk factors of advanced HCC recurrence. These results suggest that LOH on 10q23 is associated with metastatic recurrence of HCC.

Akt as a therapeutic target in cancer

BACKGROUND

The phosphatidylinositol 3-kinase (PI3K)/phosphatase and tensin homolog (PTEN)/v-akt murine thymoma viral oncogene homolog (Akt)/mammalian target of rapamycin (mTOR) pathway is central in the transmission of growth regulatory signals originating from cell surface receptors.

OBJECTIVE

This review discusses how mutations occur that result in elevated expression the PI3K/PTEN/Akt/mTOR pathway and lead to malignant transformation, and how effective targeting of this pathway may result in suppression of abnormal growth of cancer cells.

METHODS

We searched the literature for articles which dealt with altered expression of this pathway in various cancers including: hematopoietic, melanoma, non-small cell lung, pancreatic, endometrial and ovarian, breast, prostate and hepatocellular.

RESULTS/CONCLUSIONS

The PI3K/PTEN/Akt/mTOR pathway is frequently aberrantly regulated in various cancers and targeting this pathway with small molecule inhibitors and may result in novel, more effective anticancer therapies.

Expression of phosphatase and tensin homolog deleted on chromosome ten in liver of athymic mice with hepatocellular carcinoma and the effect of Fuzheng Jiedu Decoction

AIM: To explore the expression of phosphatase and tensin homolog deleted on chromosome ten (PTEN) in liver of athymic mice with hepatocellular carcinoma (HCC) and the effect of Fuzheng Jiedu Decoction (FJD).

METHODS: Forty eight male BALB/c athymic mice models were built by Bel-7402 with an indirect method. After 24 h of postoperation, the 48 athymic mice were distributed randomly into 4 groups: A, B, C, D, each group had 12 athymic mice. Group A were treated by intragastric administration with FT207 (Tegafur) for 4 wk. Group B, C and D were treated by intragastric administration with FJD (complex prescription of Chinese crude drug) that had been delegated into 3 kinds of density as the low, middle, and high for 4 wk. At last, athymic mice were put to death, live time, volume of tumors, exponent of tumors and the tumor metastasis in livers were observed; and PTEN was detected in hepatic tissue, latero-cancer tissue and cancer tissue by immunohistochemistry.

RESULTS: Four weeks later, the total survival rate in treatment group (A + B + C) was 50% and higher than the control group (0%) treated by FT207, (P < 0.01). The survival rate in group A, B, C was higher than in group D, and except group A with D, there was significant differentces (Fisher’s Exact Test P = 0.05 or 0.01). And no differences were observed between the treatment groups and the control group in volume of tumors and exponent of tumors (P > 0.05). Tumor metastasis in livers of the treatment group was less than the controls (Fisher’s Exact Test, P = 0.021). The result of immunohistochemistry showed that the intensity of PTEN in latero-cancer tissue was the highest, and then the hepatic tissue, the lowest was cancer tissue (Kruskal-Wallis test, χ² = 60.67, P = 0.000). It also showed that the intensity of PTEN in treatment groups (A, B, C) was higher than the control group (D) (F = 5.90, P = 0.002 in hepatic tissue and F = 15.99, P = 0.000 in latero-cancer tissue and χ² = 26.08, P = 0.000 in cancer tissue), and group B is the highest in the treatment groups (P < 0.05, r = 0.01. respectively). However, there was no significant statistic difference between group A and group C (P > 0.05).

CONCLUSION: FJD can prolong the survival time and decrease tumor metastasis in livers of these experimental mice. Mechanisms of FJD healing HCC may partially be explained by enhancing the expression of PTEN in liver.

Epigenetic and genetic alterations of PTEN in hepatocellular carcinoma

AIM

To investigate the roles of epigenetic and genetic alterations of the phosphatase and tensin homologue on chromosome 10 gene (PTEN) in carcinogenesis and the development of hepatocellular carcinomas (HCC).

METHODS

A total of 56 cases of HCC tissues and six liver cell lines were studied for the expression of PTEN by immunohistochemistry and Western blot analysis. The PTEN gene mutations in exon5 and exon8 were detected by a combination of single-strand conformation polymorphism (SSCP) analysis and DNA sequencing. Methylation-specific PCR (MSP) was used to identify PTEN promoter methylation.

RESULTS

Of the 56 cases of HCC, 24 (42.9%) expressed the PTEN protein. All surrounding liver tissues of the hepatoma (32 cases) were positive for PTEN. Of the six cell lines, three liver cancer cell lines showed a low expression of PTEN. Five mutations of 56 HCC samples were detected. All of them were located at intron4. No mutation was found in exon5 and exon8. After MSP analysis, we found nine cases of PTEN promoter methylation in 56 specimens (16.1%). However, no CpG island of PTEN was found to be methylated in all six liver cell lines.

CONCLUSION

The level of PTEN protein was altered in part of the HCC. The downregulation of PTEN expression may not be mainly associated with the PTEN mutations, but partly due to PTEN promoter methylation and other epigenetic regulation.

Hepatitis B virus integration, fragile sites, and hepatocarcinogenesis

Chronic liver disease associated with long term hepatitis B virus (HBV) infection contributes importantly to the development of hepatocellular carcinoma (HCC). A salient feature of these chronic infections is the integration of subgenomic HBV DNA fragments into many different locations within the host DNA, suggesting that integration is random. Although this may promote genetic instability during liver regeneration which accompanies a bout of chronic liver disease, the actual role of integrated HBV DNA in hepatocarcinogenesis is uncertain. Importantly, most integration events retain the HBV open reading frame encoding the HBx antigen (HBxAg), which is the virus contribution to HCC. In addition, many integration events reported in the literature occur near or within fragile sites or other cancer associated regions of the human genome that are prone to instability in tumor development and progression. Genetic instability associated with integration potentially alters the expression of oncogenes, tumor suppressor genes, and microRNAs (miRNAs) that may contribute importantly to tumorigenesis. If so, then selected integration events may alter pathways that are rate limiting in hepatocarcinogenesis, thereby providing targets with diagnostic/prognostic potential and for therapeutic intervention.

Correlation between loss of PTEN expression and PKB/AKT phosphorylation in hepatocellular carcinoma

The clinical significance of phosphatase and tensin homolog deleted on chromosome ten (PTEN) protein expression and the correlation between the expression of PTEN and phosphorylation of protein kinase B (PKB/AKT) in human hepatocellular carcinoma (HCC) were investigated. The expression of PTEN and phospho-AKT was detected by SP immunohistochemical technique and Western blotting in 35 cases of HCC, 15 cases of liver cirrhosis and 8 cases of normal tissues. The correlation between the expression of PTEN and PKB/AKT in HCC was analyzed. The results showed that the positive expression of PTEN in HCC (62.9%, 0.085 +/- 0.021) was significantly lower than that in liver cirrhosis and normal tissues (P < 0. 01). The expression level of PTEN was related to the differentiation degree of HCC and the status of metastasis (P < 0.05). Western blotting revealed a significant inverse correlation between PTEN and phospho-AKT (r = -0.818, P < 0.01). These results demonstrated that down-regulation or loss of PTEN, which may not be able to effectively inhibit the hyper-phosphorylation of PKB/AKT, might play an important role in tumorigenesis and progression of HCC.

An evaluation of the role of insulin-like growth factors (IGF) and of type-I IGF receptor signalling in hepatocarcinogenesis and in the resistance of hepatocarcinoma cells against drug-induced apoptosis

Strong evidence emphasizes the role of the insulin-like growth factor (IGF) system and of type-I IGF receptor (IGF-IR) signalling in tumourigenesis. In this connection: (i) changes in the expression pattern of components of the IGF system (autocrine/paracrine expression of IGF-I and -II, overexpression of IGF-IR, decreased expression of IGF-binding proteins (IGFBPs) and of type-II IGF receptor/cation-independent mannose-6-phosphate receptor (IGF-II/M6PR) and (ii) increased serum concentrations of proteases that cleave the IGFBPs (e.g., cathepsin D) were observed in patients with hepatocellular carcinomas (HCC), in human hepatoma cell lines and in their conditioned culture medium, as well as in rodent models of hepatocarcinogenesis. Accordingly, studies carried out with animal models do suggest that the IGF system and IGF-IR signalling may play a role in hepatocarcinogenesis and in deregulated proliferation and apoptosis of HCC cells. Finally the instrumental role of Raf/MEK/ERK, one of the signalling cascades stimulated by IGF-IR, in anthracycline-induced apoptosis of HepG2 and Huh-7 human hepatoma cell lines emphasizes that care must be taken when designing combinations of antitumoural molecules for antineoplastic treatment. This review addresses the putative roles of the IGF system in primary HCC, with a special focus on the underlying molecular mechanisms. In a second part it emphasizes the putative interference of IGF-IR signalling with chemotherapeutic drug-induced apoptosis in human hepatoma cells.

NSAIDs activate PTEN and other phosphatases in human colon cancer cells: novel mechanism for chemopreventive action of NSAIDs

Studies on chemoprevention of colorectal cancer have generated increasing interest. The mechanisms involved in NSAIDs chemopreventive action are not fully elucidated. In this study, we examined in human colon cancer cells the effect of indomethacin and NS-398 (a pre-clinical selective COX-2 inhibitor) on expression of 96 genes of the EGF/PDGF signaling pathways essential for cell proliferation, migration, and survival. We found that indomethacin and NS-398 treatment significantly upregulated expression of the tumor suppressor gene, PTEN, the MAP kinase phosphatase-3, MKP-3, and the protein tyrosine phosphatase, SHP2. Additionally, NS-398 treatment increased expression of apoptotic genes such as BAD, STAT1, and CASP3. These results suggest that as a consequence of increased expression of phosphatases such as PTEN and the resulting dephosphorylation of kinases, NSAIDs can negatively regulate the EGF/PDGF pathways in colon cancer cells-a novel mechanism for NSAIDs' chemopreventive actions.

The relationship between metallothionein-1F (MT1F) gene and hepatocellular carcinoma

To investigate the expression of MT1F gene in hepatocellular carcinoma tissue and the growth suppression effect of exogenous introduction of MT1F gene on liver cell line HepG2 and to explore the potential application of MT1F gene in gene therapy of tumor. Eukaryotic expression vector of pCMV-MT1F plasmid was introduced into HepG2 line which expressed no MT1F protein originally with lipofectamine transfection method. The cell growth curve, soft agar colony formation rate and tumorigenicity in SCID mice were examined to demonstrate the growth suppression effect of exogenous MT1F gene on HepG2 cell line. The MT1F mRNA and MT1F protein were also detected in 60 pairs of surgical specimens of hepatocellular carcinoma by in situ hybridization and immunohistochemistry. The transfected HepG2 cell line grew more slowly than control HepG2 as shown by cell growth curves, the soft agar colony formation rate (3.8 percent vs. 7.4 percent, p <.01) and the average growth rate of tumor in SCID mice (30.9 +/- 6.9 vs. 70.3 +/- 5.6, p <.01). The expression level of MT1F mRNA and protein significantly increased in paracancerous tissue, normal tissue than in cancer tissues (75 percent, 70 percent vs. 16.7 percent by ISH and 66.7 percent, 60 percent vs. 10 percent by IHC, p <.01). Exogenous MT1F gene shows the strong effect of growth inhibition on HepG2 cell line. In the liver cancer tissue, MT1F shows down-regulated expression that supports the inhibited function of MT1F in cancer growth and suggests MT1F may have an important role in gene therapy of hepatocellular carcinoma.

FOXO proteins regulate tumor necrosis factor-related apoptosis inducing ligand expression. Implications for PTEN mutation in prostate cancer

Mutations in PTEN occur in 60-80% of prostate cancers and lead to a constitutive activation of the phosphatidylinositol 3-kinase pathway and a resultant loss of activity of the FOXO family of forkhead transcription factors FKHRL1 and FKHR. To provide insight into the role of PTEN mutations in prostate cancer, we used microarrays to identify genes regulated by FKHRL1 and FKHR in LAPC4 prostate carcinoma cells. These studies revealed that adenoviral overexpression of FKHRL1 and FKHR in the LAPC4 prostate cancer cell line resulted in apoptosis and induced the expression of many genes that affect cellular proliferation or survival. The expression of one of these FOXO-regulated genes, TRAIL, a pro-apoptotic member of the tumor necrosis factor family, was decreased in human metastatic prostate tumors. The altered expression of TRAIL in these tumors correlated directly with decreased PTEN expression and the resultant loss of FKHRL1 and FKHR activity. Analysis of the effects of FOXO proteins on the TRAIL promoter localized the FKHRL1 responsive element of the TRAIL promoter to nucleotides -138 to -121 and demonstrated that TRAIL is a direct target of FKHRL1. These findings suggest that the decreased activity of FKHRL1 and FKHR in prostate cancers resulting from loss of PTEN leads to a decrease in TRAIL expression that may contribute to increased survival of the tumor cells.

Genetic mechanisms of hepatocarcinogenesis

The development of hepatocellular carcinoma (HCC) is a multistep process associated with changes in host gene expression, some of which correlate with the appearance and progression of tumor. Preneoplastic changes in gene expression result from altered DNA methylation, the actions of hepatitis B and C viruses, and point mutations or loss of heterozygosity (LOH) in selected cellular genes. Tumor progression is characterized by LOH involving tumor suppressor genes on many chromosomes and by gene amplification of selected oncogenes. The changes observed in different HCC nodules are often distinct, suggesting heterogeneity on the molecular level. These observations suggest that there are multiple, perhaps redundant negative growth regulatory pathways that protect cells against transformation. An understanding of the molecular pathogenesis of HCC may provide new markers for tumor staging, for assessment of the relative risk of tumor formation, and open new opportunities for therapeutic intervention.

Consistent chromosome 10 rearrangements in four newly established human hepatocellular carcinoma cell lines

Cancer cell lines represent an invaluable resource for isolation of novel genes relevant to tumor pathogenesis and as in vitro models. In this study, we report on the successful establishment of four cell lines from hepatocellular carcinoma tissue. These cell lines, designated HKCI-1, HKCI-2, HKCI-3, and HKCI-4, have been growing continuously for more than 24 months and have been passaged more than 50 times. A comprehensive cytogenetic characterization on the primary tumors and the derived cell lines was achieved by the combined approach of spectral karyotyping and comparative genomic hybridization. Chromosomal imbalances from the primary tumors were also maintained in the cell lines and included gains of 1q, 6p, 7, 10p, 17q, and 20 and loss of 4q. Recurring translocations included t(X;11), t(1;10), t(4;16), i(5)(p10), t(7;21), t(8;17), t(9;22), i(10)(p10), t(14;20), t(16;22), and t(17;19). It was noteworthy that consistent chromosome 10 aberrations, in particular t(1;10)(q10;p10), were detected in all four cell lines. Furthermore, microsatellite analysis on primary tumor and derived cell lines indicated a common deleted region of 10q23-q26. The functional importance of chromosome 10 aberrations in relation to the pathogenesis of HCC is unknown; however, the high frequency with which such aberrations were maintained in the cell lines suggests proliferative advantages of 10q loss or 10p gain in the multistep development of hepatic neoplasia.

Inactivation of SSI-1, a JAK/STAT inhibitor, in human hepatocellular carcinomas, as revealed by two-dimensional electrophoresis

BACKGROUND/AIMS

Hepatocellular carcinoma (HCC) is one of the most common human cancers, and many efforts have been paid to discover aberrant expression control in HCC, however the specific molecular mechanisms involved in hepatocarcinogenesis remain to be determined.

METHODS

To investigate genomic changes that occur in human primary hepatocellular carcinomas (HCC), we carried out restriction landmark genomic scanning. This two-dimensional electrophoretic system displays 2000-3000 NotI-landmark sites in a single gel.

RESULTS

We detected one landmark spot that showed diminished signal intensities in a majority of the HCCs we examined. Cloning revealed that this spot represented a NotI-cluster sequence that was enriched with CpG dinucleotides in the promoter region of a gene encoding Janus kinase (JAK)-binding protein, SSI-1 (also known as JAB1 or SOCS-1). Expression of the SSI-1 gene was markedly reduced in half of eight HCCs analyzed.

CONCLUSIONS

This protein regulates the Janus kinase signal transducers and activators of transcription signal transduction pathway, which transmits signals from cytokines to the intracellular apparatus. These data suggest that dysregulation of the pathway relate with progression of HCC.

Genetics of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the human cancers clearly linked to viral infections. Although the major viral and environmental risk factors for HCC development have been unravelled, the oncogenic pathways leading to malignant transformation of liver cells have long remained obscure. Recent outcomes have been provided by extensive allelotype studies which resulted in a comprehensive overview of the main genetic abnormalities in HCC, including DNA copy gains and losses. The differential involvement of the p53 tumor-suppressor gene in tumors associated with various risk factors has been largely clarified. Evidence for a crucial role of the reactivation of the Wnt/beta-catenin pathway, through mutations in the beta-catenin and axin genes in 30-40% of liver tumors, represents a major breakthrough. It has also been shown that the Rb pathway is frequently disrupted by methylation-dependent silencing of the p16INK4A gene and stimulation of Rb degradation by a proteosomal subunit. Presently, the identification of candidate oncogenes and tumor suppressors in the most frequently altered chromosomal regions is a major challenge. Great insights will come from integrating the signals from different pathways operating at preneoplastic and neoplastic stages. This search might, in time, permit an accurate evaluation of the major targets for therapeutic treatments.