Identification of the gene for a novel liver-related putative tumor suppressor at a high-frequency loss of heterozygosity region of chromosome 8p23 in human hepatocellular carcinoma

Cloning and characterization of the promoter region of human LPTS/PinX1 gene

The gene for LPTS/PinX1 encodes a potent telomerase inhibitor and suppresses tumor cell growth. In order to investigate the transcriptional regulation of this gene, we isolated its 5'-flanking region from the human genomic BAC clone and identified a major transcriptional initiation site. The sequence of the 5'-flanking region is GC-rich, lacks canonical TATA box, but contains potential binding sites for a variety of transcription factors. The deletion analysis indicated that the proximal 100 bp (from nt -66 to +34) is essential for minimal promoter activity and the regions of promoter from nt -1272 to -573 and nt -330 to -66 are required for maximal expression of the LPTS/PinX1 gene. Four DNase I hypersensitive sites (DHS1-4) mapping to the regions of transcription initiation and promoter in LPTS/Pinx1 gene were also revealed.

Breast cancer in young women (?35 years): Genomic aberrations detected by comparative genomic hybridization

Sporadic breast cancer in young women is different from the one in older patients regarding pathological features and aggressiveness of the tumors, but the spectrum of genetic alterations are largely unknown. We used comparative genomic hybridization (CGH) to analyze DNA copy number changes in 88 tumor samples from women </=35 years of age. Findings were compared to histopathological data including tumor type, grading, lymph nodes and metastasis. Genomic gains clustered to chromosome arms 1q (64.8%), 8q (61.4%), 17q (50.0%), 20q (33.0%), 3q (20.5%), 1p (17.0%), 5p (17.0%) and 15q (17%). Losses were commonly located on 8p (19.3 %), 11q (11.4%), 16q (11.4%), 17p (11.4%) and 18q (10.2%). A comparison with published CGH data from breast carcinomas of similar type and grade showed the following differences: (1) gains were much more frequent than losses, and (2) losses on 8p22-p23 were more prevalent in patients with positive lymph node metastasis (p = 0.02), and Grade III tumors were associated with gains on the long arm of chromosome 8 (p = 0.01). Therefore, alterations in these genomic regions may be responsible for the reduced survival of patients with early onset breast cancer.

Analysis of the transcription regulator, CNOT7, as a candidate chromosome 8 tumor suppressor gene in colorectal cancer

Loss of heterozygosity (LOH) on the short arm of chromosome 8 occurs at high frequencies in many tumor types, including colorectal carcinoma. We have previously used microcell-mediated chromosome transfer (MMCT) to map an approximately 7.7 Mb colorectal cancer suppressor region (CRCSR) at 8p22-23.1. We have now taken a candidate gene approach to identify the putative tumor suppressor gene located within the CRCSR. CNOT7 encodes a subunit of the CCR4-Not transcription complex and is located at 8p22. We showed that CNOT7 is expressed in normal colonic mucosa and in colonic crypt cells, as well as in colorectal cell lines and primary tumors. We assembled a panel of 88 primary colorectal tumors comprising 20 MSI-high (high microsatellite instability), 19 MSI-low and 49 MSS (microsatellite stable) tumors for mutation analysis of the CNOT7 gene. Denaturing high-performance liquid chromatography (DHPLC) analysis of the entire coding region of the CNOT7 gene revealed only one somatic missense mutation in an MSS tumor. The rarity of somatic mutations in CNOT7, and its expression in primary colorectal tumors and cell lines, suggests that CNOT7 is not the target tumor suppressor gene in the 8p22-23.1 CRCSR.

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.

The abnormalities of chromosome 8 in two hepatocellular carcinoma cell clones with the same genetic background and different metastatic potential

PURPOSE

Two hepatocellular carcinoma (HCC) cell clones named MHCC97-H and MHCC97-L with different metastatic potential have recently been established from the same parent cell line MHCC97 in our institute. The cytogenetic alterations of these two clones were investigated in this study to explore the possible clues to the mechanism involved in HCC metastasis.

METHODS

Their chromosomal aberrations were analyzed with comparative genomic hybridization (CGH), chromosome-specific painting, and two-color fluorescence in situ hybridization (FISH).

RESULTS

The aberrations were found in a total of 17 chromosomes, and six kinds of the aberrations including gains of 1q, 7q, 8q, 20, and the losses of 8p23, 21q were found both in the two cell clones and their parent cell line MHCC97. Using modified CGH, with the DNA of MHCC97-L as control to test the MHCC97-H clone, the loss of 8p23 and the gain of 1q31-32, 8q21.3-22, 13q22, 17q22 were highlighted, and the most significant finding was on chromosome 8. Dual color FISH combining a pericentromeric probe and a BAC probe mapping at 8q23.1 was then performed to verify this result, and the signal ratios of the BAC to centromere were 1.43 in MHCC97-H and 1.45 in MHCC97-L, confirming the over-representations at 8q in both cells. Another interesting finding in the dual-color metaphase FISH was the intrachromosomal translocation of 8q to 8p (looked like an isochromosome 8) and non-reciprocal translocation of part of 8q to 4q, which was further clarified and proved by the FISH with whole chromosome 8 painting probe.

CONCLUSIONS

The high copies amplification on 8q, the formation of isochromosome 8, non-reciprocal translocation of partial 8q to 4q, and loss of 8p occurred at the same time and are the characteristic chromosomal aberrations of the two cell clones. The chromosome 8p, especially 8p23, might harbor some novel genes related to the HCC metastasis.

Allelic imbalance regions on chromosomes 8p, 17p and 19p related to metastasis of hepatocellular carcinoma: comparison between matched primary and metastatic lesions in 22 patients by genome-wide microsatellite analysis

To understand the molecular mechanisms of metastasis in hepatocellular carcinoma (HCC), it is necessary to identify the accumulating genetic alterations during its progression as well as those responsible for the acquisition of metastatic potential in cancer cells. In our previous study, using comparative genomic hybridization (CGH), we found that loss on chromosome 8p is more frequent in metastatic lesions than in matched primary tumors of HCC. Thus, 8p deletion might contribute to HCC metastasis. To narrow the location of metastasis-related alteration regions, we analyzed 22 primary and matched metastatic lesions of HCC by genome-wide microsatellite analysis. Common regions with high levels of allelic imbalance (AI) were identified on 17p, 8p11-cen, 8p21-23, 4q32-qter, 4q13-23, 16q, and 1p33. Regions with increased AI in metastatic lesions were 8p23.3, 8p11.2, 17p11.2-13.3, 4q21-22, 4q32-qter, 8q24.1, 9p11, 9q31, 11q23.1, 13q14.1-31, 13q32-qter, 16p13.3, 16q13, 16q22, and 19p13.1, and these were considered to be related to the metastasis phenotype. Among them, loss on 8p was again proved to be related to progression and metastasis of HCC, and 8p23.3 and 8p11.2 were two likely regions harboring metastasis-related genes. It was also shown for the first time in HCC that AI of 19p13.1 might also be related to metastatic potential. These results provide some candidate regions for further study to identify putative genes suppressing metastasis of HCC.

Beta-arrestin 2 functions as a G-protein-coupled receptor-activated regulator of oncoprotein Mdm2

Oncoprotein Mdm2 is a master negative regulator of the tumor suppressor p53 and has been recently shown to regulate the ubiquitination of beta-arrestin 2, an important adapter and scaffold in signaling of G-protein-coupled receptors (GPCRs). However, whether beta-arrestin 2 has any effect on the function of Mdm2 is still unclear. Our current results demonstrated that the binding of Mdm2 to beta-arrestin 2 was significantly enhanced by stimulation of GPCRs. Activation of GPCRs led to formation of a ternary complex of Mdm2, beta-arrestin 2, and GPCRs and thus recruited Mdm2 to GPCRs at plasma membrane. Moreover, the binding of beta-arrestin 2 to Mdm2 suppressed the self-ubiquitination of Mdm2 and consequently reduced the Mdm2-mediated p53 degradation and ubiquitination. Further experiments revealed that overexpression of beta-arrestin 2 enhanced the p53-mediated apoptosis while suppression of endogenous beta-arrestin 2 expression by RNA interference technology considerably attenuated the p53-mediated apoptosis. Our study thus suggests that beta-arrestin 2 may serve as a cross-talk linker between GPCR and p53 signaling pathways.

Beta defensin-1, parvalbumin, and vimentin: a panel of diagnostic immunohistochemical markers for renal tumors derived from gene expression profiling studies using cDNA microarrays

The common histopathologic subtypes of renal epithelial neoplasms include conventional, or clear cell, renal cell carcinoma (RCC), papillary RCC, chromophobe RCC, and renal oncocytoma. These subtypes differ clinically and pathologically, making accurate classification important. However, this differential diagnosis can be challenging because of overlapping morphology, suggesting a potential utility for ancillary immunohistochemical markers. We used cDNA microarrays to identify candidate markers for distinguishing renal tumor subtypes. In this report we validated differential expression of three candidate markers, beta defensin-1, parvalbumin, and vimentin, and evaluated the use of this immunohistochemical panel as a potential diagnostic tool. Consistent with our cDNA microarray data, chromophobe RCCs and oncocytomas exhibited similar expression profiles: 8 of 8 examples of each subtype were immunohistochemically positive for beta defensin-1 and parvalbumin and negative for vimentin (sensitivity 100%, specificity 100%); 4 of 7 papillary RCCs were positive for beta defensin-1, parvalbumin, and vimentin (sensitivity 57%, specificity 97%); and 22 of 23 conventional RCCs were negative for beta defensin-1, parvalbumin, or both markers (sensitivity 96%, specificity 96%) as well as positive for vimentin (sensitivity 83%). The immunohistochemical panel distinguished renal tumor subtypes with greater specificity than any marker used alone. This work demonstrates that a useful panel of immunohistochemical markers can be derived from differential gene expression profiles determined using cDNA microarrays.

Mutation analysis of novel human liver-related putative tumor suppressor gene in hepatocellular carcinoma

AIM: To find the point mutations meaningful for inactivation of liver-related putative tumor suppressor gene (LPTS) gene, a human novel liver-related putative tumor suppressor gene and telomerase inhibitor in hepatocellular carcinoma.

METHODS: The entire coding sequence of LPTS gene was examined for mutations by single strand conformation polymorphism (SSCP) assay and PCR products direct sequencing in 56 liver cancer cell lines, 7 ovarian cancer and 7 head & neck tumor cell lines and 70 pairs of HCC tissues samples. The cDNA fragment coding for the most frequent mutant protein was subcloned into GST fusion expression vector. The product was expressed in E. coli and purified by glutathione-agarose column. Telomeric repeat amplification protocol (TRAP) assays were performed to study the effect of point mutation to telomerase inhibitory activity.

RESULTS: SSCP gels showed the abnormal shifting bands and DNA sequencing found that there were 5 different mutations and/or polymorphisms in 12 tumor cell lines located at exon2, exon5 and exon7. The main alterations were A(778)A/G and A(880)T in exon7. The change in site of 778 could not be found in HCC tissue samples, while the mutation in position 880 was seen in 7 (10%) cases. The mutation in the site of 880 had no effect on telomerase inhibitory activity.

CONCLUSION: Alterations identified in this study are polymorphisms of LPTS gene. LPTS mutations occur in HCC but are infrequent and of little effect on the telomerase inhibitory function of the protein. Epigenetics, such as methylation, acetylation, may play the key role in inactivation of LPTS.

Over-expression of LPTS-L in hepatocellular carcinoma cell line SMMC-7721 induces crisis

AIM: To evaluate the function of the longer transcripts LPTS-L in hepatocellular carcinoma cell line SMMC-7721.

METHODS: SMMC-7721 cells were transfected with LPTS-L expression construct and stably transfected cells were selected by G418. Multiple single clones formed and were checked for their phenotype. In the study of the effect on telomerase activity of LPTS-L in vitro, GST-LPTS-L fusion protein was expressed in E.coli and purified by glutathione-agarose column. Telomeric repeat amplification protocol (TRAP) assays were performed to study the influence of telomerase activity in SMMC-7721 cells.

RESULTS: Over-expression of LPTS-L induced SMMC-7721 cells into crisis. LPTS-L could inhibit the telomerase activity in SMMC-7721 cells in vitro.

CONCLUSION: LPTS-L is a potent telomerase inhibitor. Over-expression of LPTS-L can induce hepatoma cells into crisis due to the reduction of telomerase activity.

Pyrrolizidine alkaloid clivorine inhibits human normal liver L-02 cells growth and activates p38 mitogen-activated protein kinase in L-02 cells

Clivorine, a pyrrolizidine alkaloid extracted from Chinese medicinal plant Ligularia hodgsonii Hook significantly inhibited human normal liver L-02 cells proliferation and decreased L-02 cells viability. The results of western blot showed that clivorine strongly evoked phosphorylation of p38 mitogen-activated protein (MAP) Kinase in L-02 cells, but had no effect on extracellular signal-related kinases MAP Kinase phosphorylation. Moreover, another pyrrolizidine alkaloid monocrotaline had no effect on phosphorylation of p38 MAP Kinase in L-02 cells. These studies document the effects of pyrrolizidine alkaloid clivorine on the MAPK cascade and on the growth of human normal liver L-02 cells for the first time, which may be a possible reason for the toxic effects observed in those plants containing pyrrolizidine alkaloids.

A phylogenetic analysis identifies heterogeneity among hepatocellular carcinomas

Primary hepatocellular carcinoma (HCC) is a significant cause of cancer morbidity and mortality on the global scale. Although epidemiologic studies have identified major risk factors for HCC, the sequence of oncogenic events at the molecular level remains poorly understood. While genetic allele loss appears to be a common event, the significance of the loss is not clear. In order to determine whether allele loss appears to be a random event among HCCs or whether patterns of loss cluster in groups of tumors, a phylogenetic approach was used to examine 32 tumors for genome-wide loss of heterozygosity employing 391 markers. Clusters identified by the phylogenetic analysis were then contrasted to compare candidate locus variation among individuals and to determine whether certain clusters exhibited higher loss rates than other clusters. The analysis found that 3 major and 1 minor cluster of loss could be identified and, further, these clusters were distinguished by variable rates of loss (cluster 1, 29%; cluster 2, 21%; cluster 3, 16%). The analyses also indicated that the allele loss rates in HCC were not insignificant and that the patterns of allele loss were complex. In addition, the results indicated that an individual's constitutional genotype at the EPHX1 locus may be a critical factor in determining the path of tumor evolution. In conclusion, it appears that in HCC, allele loss is not random, but clusters into definable groups that are characterized by distinctive rates of loss.

Transcriptional activation of interleukin-8 by beta-catenin-Tcf4

Nuclear translocation of beta-catenin and its association with Tcf/Lef factors are key steps in transduction of the Wnt signal, which is aberrantly activated in a variety of human cancers. In a search for new beta-catenin-Tcf target genes, we analyzed beta-catenin-induced alterations of gene expression in primary human hepatocytes, after transduction of either dominant stable beta-catenin or its truncated, transactivation-deficient counterpart by means of a lentiviral vector. cDNA microarray analysis revealed a limited set of up-regulated genes, including known Wnt targets such as matrilysin and keratin-1. In this screen, we identified the CXC chemokine interleukin 8 (IL-8) as a direct target of beta-catenin-Tcf4. IL-8 is constitutively expressed in various cancers, and it has been implicated in tumor progression through its mitogenic, motogenic, and angiogenic activities. The IL-8 promoter contains a unique consensus Tcf/Lef site that is critical for IL-8 activation by beta-catenin. We show here that the p300 coactivator was required for efficient transactivation of beta-catenin on this promoter. Ectopic expression of beta-catenin in hepatoma cells promoted IL-8 secretion, which stimulated endothelial cell migration. These data define IL-8 as a Wnt target and suggest that IL-8 induction by beta-catenin might be implicated in developmental and tumorigenic processes.

Chromosomal aberrations related to metastasis of human solid tumors

The central role of sequential accumulation of genetic alterations during the development of cancer has been firmly established since the pioneering cytogenetic studies successfully defined recurrent chromosome changes in specific types of tumor. In the course of carcinogenesis, cells experience several genetic alterations that are associated with the transition from a preneoplastic lesion to an invasive tumor and finally to the metastatic state. Tumor progression is characterized by stepwise accumulation of genetic alterations. So does the dominant metastatic clone. Modern molecular genetic analyses have clarified that genomic changes accumulate during the development and progression of cancers. In comparison with the corresponding primary tumor, additional events of chromosomal aberrations (including gains or allelic losses) are frequently found in metastases, and the incidence of combined chromosomal alterations in the primary tumor, plus the occurrence of additional aberrations in the distant metastases, correlated significantly with decreased postmetastatic survival. The deletions at 3p, 4p, 6q, 8p, 10q, 11p, 11q, 12p, 13q, 16q, 17p, 18q, 21q, and 22q, as well as the over-representations at 1q, 8q, 9q, 14q and 15q, have been found to associate preferentially with the metastatic phenotype of human cancers. Among of them, the deletions on chromosomes 8p, 17p, 11p and 13p seem to be more significant, and more detail fine regions of them, including 8p11, 8p21-12, 8p22, 8p23, 17p13.3, 11p15.5, and 13q12-13 have been suggested harboring metastasis-suppressor genes. During the past decade, several human chromosomes have been functionally tested through the use of microcell-mediated chromosome transfer (MMCT), and metastasis-suppressor activities have been reported on chromosomes 1, 6, 7, 8, 10, 11, 12, 16, and 17. However, it is not actually known at what stage of the metastatic cascade these alterations have occurred. There is still controversial with the association between the chromosomal aberrations and the metastatic phenotype of cancer. As the progression of human genome project and the establishment of more and more new techniques, it is hopeful to make clear the genetic mechanisms involved in the tumor metastasis in a not very long future, and provide new clues to predicting and controlling the metastasis.

Molecular cloning and characterization of a novel gene which is highly expressed in hepatocellular carcinoma

To gain new insight into the molecular mechanism underlying the pathogenesis of human primary hepatocellular carcinoma (HCC), we searched for HCC-specific molecules through screening genes that are differentially expressed between cancerous and noncancerous counterparts of liver and identified a novel HCC-associated gene, HCCA1 encoding a approximately 80 kDa cytoplasmic protein that contains several proline-rich motifs likely for SH3-binding. HCCA1 transcript, albeit present in some adult tissues, is up-regulated selectively in HCC but not in other tumor cells. High expression of HCCA1 occurs as a late event frequently (89.2%) in HCCs and correlated significantly with the degree of tumor progression. When treated with antisense oligonucleotides to HCCA1, HCCA1 expression in HCC cells (HuH-7) was effectively suppressed and cell growth was down-regulated in a time- and dose-dependent manner. Furthermore, HuH-7 cells harboring the HCCA1 antisense expression clone displayed a remarkably reduced efficiency in colony formation. Together, these data strongly suggest that HCCA1 is a positive effector in cell proliferation and contributes to HCC carcinogenesis and progression. We believe that this protein will serve as a novel useful marker for HCC and is a potential target for pharmaceutical intervention of this malignant disease.

High-density allelotyping of chromosome 8p in hepatocellular carcinoma and clinicopathologic correlation

BACKGROUND

Allelic deletions are frequent genetic alterations in patients with hepatocellular carcinoma (HCC).

METHODS

To evaluate the allelic losses on chromosome 8p in HCC patients and define their clinicopathologic significance, we performed high-density allelotyping on 8p in 60 patients with HCC and analyzed the clinicopathologic correlation.

RESULTS

Using 24 microsatellite markers, allelic losses on 8p were frequent. Loss of heterozygosity (LOH) at one or more loci was observed in 34 (57%) HCC patients. When the allelic losses were compared between groups categorized by clinicopathologic variables, significant correlation was found between tumors with interstitial losses and larger tumor size (> 5 cm; P = 0.026). In addition, allelic loss at D8S298 at 8p22 was associated closely with venous permeation, tumor microsatellite formation, and larger tumor size (P = 0.019, 0.024, and 0.007, respectively). LOH at locus D8S1721 at 8p23.1 was seen more frequently in nonencapsulated tumors (P = 0.007) and LOH at D8S1771 at 8p21.3 was associated with a larger tumor size and poorer cellular differentiation (P = 0.018 and 0.049, respectively).

CONCLUSIONS

Allelic losses on 8p are frequent in HCC patients. Association of allelic losses at specific loci on 8p with a more aggressive tumor behavior suggests that loss/inactivation of putative tumor suppressor gene(s) located at these regions may confer a tumor growth advantage and contribute to the progression of HCC.

Genetic analysis of the liver putative tumor suppressor (LPTS) gene in hepatocellular carcinomas

Recently, a novel liver-related putative tumor suppressor (LPTS), which has a growth inhibitory function in the hepatocellular carcinoma (HCC) cell line, has been identified at chromosome 8p23. To determine the relationship of the LPTS with the development or progression of HCC, we analyzed the genetic alterations and the expression pattern of the LPTS gene in a series of 80 HCCs, six dysplastic nodules, and eight large regenerating nodules, determining the genomic structures. We identified a total of seven exons, of which two were alternative, and three LPTS isoforms, short (LPTS-S), medium (LPTS-M), and long-sizes (LPTS-L). In the genetic alteration study of the LPTS gene, no mutation was detected in the large regenerating nodules, dysplastic nodules, and HCC, whereas ten (34.5%) of 29 informative cases at one or more intragenic polymorphic sites showed loss of heterozygosity (LOH). Interestingly, LOH was identified only in HCC samples with hepatitis B virus (HBV) infection and the frequency of LOH was not statistically related with histologic grade and clinical stage, suggesting that allelic loss of the LPTS gene may occur as an early event in the development of HCC, especially in the cases with HBV infection.

Molecular aspects of hepatic carcinogenesis

Exogenous agents correlated with hepatocellular carcinoma (HCC) have been identified and well characterized. These agents, including the different viruses that cause chronic hepatitis and cirrhosis, can lead to regenerative nodules and dysplastic nodules/adenomatous hyperplasia. These conditions associated with several molecular alterations of hepatocyte ultimately culminate in hepatocellular carcinoma. Recently, there has been a great progress in the identification of somatic and germinative mutations that may be correlated with the development of HCC, justifying a review on the subject. Hence, the factors involved in the process of hepatic carcinogenesis, such as infection by the hepatitis B and C viruses, with a special focus in the molecular alterations described in recent years are discussed herein, pointing out areas potentially relevant for clinical development.

The Pin2/TRF1-interacting protein PinX1 is a potent telomerase inhibitor

Telomerase activity is critical for normal and transformed human cells to escape from crisis and is implicated in oncogenesis. Here we describe a novel Pin2/TRF1 binding protein, PinX1 that inhibits telomerase activity and affects tumorigenicity. PinX1 and its small TID domain bind the telomerase catalytic subunit hTERT and potently inhibit its activity. Overexpression of PinX1 or its TID domain inhibits telomerase activity, shortens telomeres, and induces crisis, whereas depletion of endogenous PinX1 increases telomerase activity and elongates telomeres. Depletion of PinX1 also increases tumorigenicity in nude mice, consistent with its chromosome localization at 8p23, a region with frequent loss of heterozygosity in a number of human cancers. Thus, PinX1 is a potent telomerase inhibitor and a putative tumor suppressor.

Hepatocellular carcinoma

The number of papers published regarding hepatocellular carcinoma between 1999 and 2001 increased from previous years. This year a study confirmed the increase in incidence in the United States. Also, several studies established for the first time that tobacco smoking was a risk factor for the development of this tumor. Several studies established that the process of angiogenesis is critical for the development of hepatocellular carcinoma, and one paper indicated that inhibiting this process might lead to possible treatment of this tumor. Resection was compared with liver transplantation for the first time in two studies. It was shown that transplantation offered the overall best long-term option, but in a certain group of patients without portal hypertension and well-preserved liver function resection is the best option.

Organization of human ACAT-2 gene and its cell-type-specific promoter activity

Acyl-CoA:cholesterol acyltransferase (ACAT) plays important roles in cellular cholesterol homeostasis. Two ACAT genes exist in mammals. We report here the genomic organization of human ACAT-2 gene and analysis of its promoter activity in various cell lines. The human ACAT-2 gene spans over 18 kb and contains 15 exons. Three transcription start sites and one poly(A) site are identified by the 5'/3'-RACE. In addition, the human ACAT-2 gene is linked to the insulin-like growth factor binding protein 6 (IGFBP-6) gene in a head-to-tail manner with a small intergenic region of about 1.2 kb. The 5'-flanking region of human ACAT-2 gene contains many potential cis-acting elements for multiple transcriptional regulatory factors but lacks TATA and CCAAT boxes. Using promoter-luciferase reporter assays, we demonstrate the transcriptional activity of ACAT-2 gene promoter is high in Caco-2 cells, especially after these cells become postconfluent and behave as intestinal enterocytes.