Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019204 (hepatocellular carcinoma)
 71,386 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We analyzed the p16INK4 status of 6 hepatocellular carcinoma (HCC) cell lines and 32 primary HCC tumors, including 9 early-stage tumors, to determine whether p16INK4 tumor-suppressor gene inactivation participates in hepatocarcinogenesis. p16INK4 was studied at its protein level through Western blotting, at its messenger RNA (mRNA) level through reverse-transcriptase polymerase chain reaction analysis (RT-PCR) and Northern blotting, and at its genomic level through Southern blotting and PCR-single-strand conformation polymorphism analysis. The p16 protein was absent from 3 of 6 cell lines (50%) and 11 of 32 primary tumors (34%), but present in noncancerous tissues, indicating that p16INK4 is involved in hepatocarcinogenesis. Furthermore, we suggest that the p16 protein loss may contribute to the following: (1) early-stage hepatocarcinogenesis, because it was observed in 22% of early stage tumors; and (2) tumor progression, because it occurred approximately twice as often in advanced rather than in early stage tumors (40%). It was striking that neither p16INK4 homozygous deletion and mutation nor loss of p16INK4 mRNA expression were observed in HCC cell lines and primary tumors, including those specimens from which the p16 protein was absent except the Li7HM cell line, in which p16INK4 mRNA was not detected. These results suggest that p16INK4 in HCC is inactivated predominantly by posttranscriptional regulation rather than by genomic aberrations and lack of transcription.
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PMID:Inactivation of p16INK4 in hepatocellular carcinoma. 878 27

The molecular mechanisms of hepatocarcinogenesis are poorly understood. Only very recently has there been a suggestion of familial hepatocellular carcinoma (HCC). We have analyzed the status of the p16INK4(MTS1) gene, a cyclin-dependent kinase inhibitor, in 26 patients with HCC of different etiologies. Four patients carried hemizygous germ-line point mutations of the p16INK4(MTS1) gene, suggesting the existence of familial HCC involving this gene. The wild-type allele was lost in the tumor in 2 of these 4 patients. Three of the patients carrying a germ-line mutation had non-cirrhosis-associated HCC. No somatic mutations of p16INK4(MTS1) were observed in the 26 cases of HCC. The most common somatic alteration of the p16INK4(MTS1) gene in HCC was de novo methylation, which was detected in 48% of the cases. Low levels (21%) of p16INK4(MTS1) gene allele loss were observed. Altogether, these results indicate that alteration of the p16INK4(MTS1) gene plays an important role in the genesis of HCC.
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PMID:Germ-line mutations of the p16INK4(MTS1) gene occur in a subset of patients with hepatocellular carcinoma. 918 56

In cycling cells, the retinoblastoma protein (pRb) is un- and/or hypo-phosphorylated in early G1 and becomes hyper-phosphorylated in late G1. The role of hypo-phosphorylation and identity of the relevant kinase(s) remains unknown. We show here that hypo-phosphorylated pRb associates with E2F in vivo and is therefore active. Increasing the intracellular concentration of the Cdk4/6 specific inhibitor p15(INK4b) by transforming growth factor beta treatment of keratinocytes results in G1 arrest and loss of hypo-phosphorylated pRb with an increase in unphosphorylated pRb. Conversely, p15(INK4b)-independent transforming growth factor beta-mediated G1 arrest of hepatocellular carcinoma cells results in loss of Cdk2 kinase activity with continued Cdk6 kinase activity and pRb remains only hypo-phosphorylated. Introduction of the Cdk4/6 inhibitor p16(INK4a) protein into cells by fusion to a protein transduction domain also prevents pRb hypo-phosphorylation with an increase in unphosphorylated pRb. We conclude that cyclin D:Cdk4/6 complexes hypo-phosphorylate pRb in early G1 allowing continued E2F binding.
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PMID:Hypo-phosphorylation of the retinoblastoma protein (pRb) by cyclin D:Cdk4/6 complexes results in active pRb. 938 Jun 98

To clarify the relative role of hepatitis C virus (HCV) and hepatitis B virus (HBV) in hepatocarcinogenesis in hepatitis B surface antigen (HBsAg)-negative hepatocellular carcinoma (HCC) in Taiwan, polymerase chain reaction (PCR) was used to detect the HCV-RNA and HBV-DNA sequences in the serum and liver tissues from 31 HBsAg-negative HCC patients. Twenty-one were positive for antibody to HCV (group 1) and 10 were negative (group 2). Hepatitis C virus-RNA was detected by PCR in the serum of 16 group 1 patients and in the liver tissue of 17; while HBV-DNA was found in the liver tissue of only four, and no HBV-DNA was found in the serum. Hepatitis C virus RNA was detected in the serum of one group 2 patient and in the liver tissue of another. In contrast, HBV viral DNA was found in the serum of four group 2 patients and in the liver tissues of five patients. This indicates that HCV plays an important role in hepatocarcinogenesis in HBsAg-negative patients in Taiwan, especially in those with antibody to HCV. In those without antibody to HCV, HBV might still be associated with the development of HCC in a significant proportion of such patients. In order to study the role of the p53 mutation in hepatocarcinogenesis, we investigated the status of the p53 mutation in 61 HCC samples from Taiwan. The exon 5 to 8 of the p53 gene in the tumour tissue of 61 HCC were amplified and sequenced. A total of 20 cases (32.8%) were found to have mutations: 36.6% (15/41) from the HBsAg-positive group and 25.0% (5/20) from the HBsAg-negative group. The corresponding normal liver showed no mutation. The mutation is widely distributed throughout the exon 5 to 8. Only four cases (6.6%), all positive for HBsAg, had a specific hotspot mutation at codon 249 with G to T transversion. These results show that scattered point mutations in p53 are not uncommon in HCC samples from Taiwan and may be important in the development of this cancer. However, the aflatoxin-related specific mutation seems much less related to the genesis of HCC in Taiwan. To study the role of telomerase activity in hepatocarcinogenesis, a total of 39 HCC tissues and the corresponding non-tumour liver tissues were analysed. The results showed that telomerase activity was detected in all the 39 tumour tissues, while it could be detected in six of the 39 non-tumour liver tissues. The high positive rate of telomerase activity in HCC samples suggests that telomerase activity is closely related to the development or progression of HCC. To determine whether exon 1 and exon 2 of the p16 gene are altered in HCC, thirty-four tumours from 30 HCC patients were examined by DNA sequencing analysis of PCR-amplified genomic DNA. Homozygous deletions of MTS1/p16/CDKN2 exon 1 were identified in 1/34 primary tumours (3%), no mutations or rearrangements were found in these specimens. These data suggest that alterations of MTS1/p16/CDKN2 gene are rarely found in HCC, and might play little role in the development of this cancer. To study the clonality of HCC, 18 patients with multiple HCC, most of them small in size, were analysed by DNA fingerprinting. In patients positive for hepatitis B surface antigen, the integration pattern of hepatitis B viral DNA in liver tissue was also analysed. The results by both methods showed that 8/9 hepatitis B surface antigen-positive patients were different in clonality. In the remaining nine patients negative for hepatitis B surface antigen, four had different band patterns in their tumours by DNA fingerprinting. This study indicated that polyclonality of multiple HCC was rather frequent and it highlighted the importance of eliminating the underlying cause of liver injury to improve the survival of these patients. Microsatellite markers were used to study the genetic changes of HCC. Thirty cases of HCC, most of them small in size, were studied. A total of 242 microsatellite markers mapping to 1-22 and X chromosomes was used. The results showed that the range of loss of het
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PMID:Molecular mechanism of hepatocarcinogenesis. 940 51

To elucidate the alterations of CDKN2 in hepatocarcinogenesis, we performed a loss of heterozygosity (LOH) study using eight polymorphic markers surrounding the CDKN2 gene and analyzed the homozygous deletions and mutations of the CDKN2 gene in 41 primary hepatocellular carcinomas (HCCs). Frequent LOH (27.8-44%) was found in the eight loci on chromosome 9p, however, no intragenic mutations of CDKN2 were observed by PCR-SSCP analysis. Homozygous deletions were detected in 25 of 41 HCCs (61%) by a comparative multiplex PCR. No expression of the CDKN2 protein was noted in five out of nine available HCCs by Western blot analysis. These results suggest that inactivation of the CDKN2 gene in HCC is a frequent event in which homozygous deletions are the most common mechanism of CDKN2 inactivation.
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PMID:Homozygous deletions of the CDKN2 gene and loss of heterozygosity of 9p in primary hepatocellular carcinoma. 946 11

G1 phase progression of mammalian cells is mainly controlled by the cyclin-cyclin-dependent kinase (CDK)-CDK inhibitor-retinoblastoma protein (pRb) regulatory pathway. Cell cycle regulators controlling G1 phase progression are frequently involved in the carcinogenesis of many human cancer types. In hepatocellular carcinoma (HCC) the CDK inhibitor p16INK4 is predominantly inactivated by post-transcriptional regulation and p16INK4 inactivation participates in the early-stage of hepatocarcinogenesis and in disease progression. Reduced p21(WAF1/CIP1) expression, which is associated mainly with p53 gene mutation in HCCs, contributes to hepatocarcinogenesis. Reduced p27Kip1 expression is also frequently involved in HCC. The CDK inhibitors p16INK4, p21(WAF1/CIP1) and p27Kip1 are independently affected and a change in the expression of one or more of these inhibitors contributes to carcinogenesis of the majority (nearly 90%) of HCCs. Cyclin D1 amplification and overexpression play a role in the carcinogenesis of a subset (11-13%) of HCCs. Disruption of the regulatory system controlling G1 phase progression is a common event in human hepatocarcinogenesis. Further studies systematically analyzing the major regulators controlling G1 phase progression in a large cohort of HCCs will strengthen our understanding of the molecular mechanism underlying human hepatocarcinogenesis. Correcting alterations that have occurred in the G1 phase regulatory machinery may provide a novel weapon to treat and prevent HCC.
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PMID:Cell cycle regulators and human hepatocarcinogenesis. 984 Jan 20

The tumor suppressor gene p16 (CDKN2/MTS-1/INK4A) is an important component of the cell cycle and inactivation of the gene has been found in a variety of human cancers. In order to investigate the role of p16 gene in the tumorigenesis of hepatocellular carcinoma (HCC), 48 cases of HCC were analysed for p16 alterations by: methylation-specific PCR (MSP) to determine the methylation status of the p16 promoter region; comparative multiplex PCR to detect homozygous deletion; PCR-SSCP and DNA sequencing analysis to identify mutation of the p16 gene. We found high frequency of hypermethylation of the 5' CpG island of the p16 gene in 30 of 48 cases (62.5%) of HCC tumors. Moreover, homozygous deletion at p16 region were present in five of 48 cases (10.4%); and missense mutation were detected in three of 48 cases (6.3%). The overall frequency of p16 alterations, including homozygous deletion, mutation and hypermethylation, in HCC tumors was 70.8% (34 of 48 cases). These findings suggest that: (a) the inactivation of the p16 is a frequent event in HCC; (b) the p16 gene is inactivated by multiple mechanisms including homozygous deletion, promoter hypermethylation and point mutation; (c) the most common somatic alteration of the p16 gene in HCC is de novo hypermethylation of the 5' CpG island; and (d) in contrast to other studies, high frequency of genomic alterations are not uncommon in the 9p21 of the p16 gene. Our results strongly suggest that the p16 gene plays an important role in the pathogenesis of HCC.
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PMID:High frequency of p16INK4A gene alterations in hepatocellular carcinoma. 998 30

For hepatocellular carcinoma, only scarce and controversial data on CDKN2 alterations are available. A high rate of mutations in a Chinese study contrasts with a low rate found in Japanese tumors and a CDKN2 germline mutation in 4/26 Swiss tumors examined. We analyzed 23 hepatocellular carcinomas from German patients for homozygous deletions of CDKN2 by coamplification with the human tyrosine hydroxylase (TH) gene and for CDKN2 mutations by PCR-single strand conformation polymorphism analysis and direct DNA sequencing. Our results indicate the lack of homozygous deletions. In one tumor, DNA sequencing showed a GCG-ACG (alanine-threonine) substitution at codon 148, a polymorphism in exon 2 of CDKN2. We conclude that the alteration of CDKN2 by deletion or mutation appears not to be a frequent event in hepatocarcinogenesis in German patients.
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PMID:CDKN2 mutation is infrequent in german hepatocellular carcinoma. 1057 17

Saikosaponin a, a purified ingredient of Chinese herb with known antitumor activity, can inhibit cell growth and DNA synthesis of hepatoma cell line HepG2. Both mRNA and protein of the CDK inhibitor p-16(INK4a) and p-15(INK4b) in HepG2 were greatly induced by saikosaponin a while that of p-21(CIP), p-27(KIP) and other cell cycle related genes were not. In addition, reduced phosphorylation of RB protein is observed in saikosaponin a-treated HepG2. Staurosporin, one of the PKC inhibitors, significantly prevented the saikosaponin a induced growth inhibition suggesting PKC pathway be involved. On the other hand, the phorbol ester tumor promoter TPA (12-O-Tetredecanolyphorbol 13-acetate) also inhibited HepG2 growth and specifically induced p-16(INK4a) and p-15(INK4b) mRNA expression. The results suggest that both saikosaponin a and TPA-induced HepG2 growth inhibition are associated with p-15(INK4a) and p-16(INK4b) gene expression and might be mediated by PKC signaling pathway.
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PMID:Involvement of p-15(INK4b) and p-16(INK4a) gene expression in saikosaponin a and TPA-induced growth inhibition of HepG2 cells. 1144 23

Previously, we have linked prolonged intense mitogen-activated protein kinase (MAP kinase; MAPK) signaling in hepatocytes to increased expression of p21(Cip-1/WAF1/MDA6) (p21) and p16(INK4a) (p16), that leads to a p21-dependent growth arrest. In this study, we investigated the impact of hepatitis B virus X protein (pX) expression on MAPK-modulated cell cycle progression in primary mouse hepatocytes. In hepatocytes, expression of pX enhanced protein levels of p21 and p27, but not of p16. The elevated levels of p21 and p27 correlated with reduced DNA synthesis in wild-type (+/+) hepatocytes and with a weak stimulation of DNA synthesis in p21 null (-/-) cells. Antisense p27 messenger RNA (mRNA) (p27as) increased DNA synthesis in +/+ and p21 -/- cells, and pX blunted this effect in +/+ cells. In p21 -/- cells, however, p27as permitted pX to further stimulate DNA synthesis. These data argue that a reduced ability to enhance expression of both p21 and p27 is required to fully reveal the growth-potentiating properties of pX. This finding also implies that depending on the functional status of the p21 and p27 genes, expression of pX can have 2 very different effects on hepatocyte proliferation. Prolonged intense MAPK signaling reduced DNA synthesis in +/+ cells and enhanced DNA synthesis in p21 -/- cells. The enhancement of DNA synthesis in p21 -/- cells was blocked by pX, and the effect of pX was abrogated by p27as. Furthermore in p21 -/- cells, overexpression of p16 blocked MAPK-stimulated DNA synthesis, and this effect was partially reversed by p27as. These data argue that p27 can also cooperatively interact with p16 to inhibit DNA synthesis in hepatocytes. Collectively, our findings show that reduced expression of p16, p21, and p27, which can occur during hepatocellular carcinoma, enhances the ability of MAPK signaling and pX to cause proliferation in hepatocytes. Thus loss of cyclin kinase inhibitor function may play an important role in the process of tumor progression after chronic hepatitis B virus infection.
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PMID:Hepatitis B virus X protein increases expression of p21(Cip-1/WAF1/MDA6) and p27(Kip-1) in primary mouse hepatocytes, leading to reduced cell cycle progression. 1167 61


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