Alterations of the Fhit gene in hepatocellular carcinomas induced by N-nitrosodiethylamine in rats

HIV-TAT-fused FHIT protein functions as a potential pro-apoptotic molecule in hepatocellular carcinoma cells

Accumulating evidence has demonstrated that FHIT (fragile histidine triad) is a bona fide tumour suppressor gene in a large fraction of human tumours, including hepatocellular cancer. A virus-based delivery system has been developed to transfer the FHIT gene into many types of cancer cells to inhibit growth or even induce apoptosis. However, a protein-based replacement strategy for FHIT has not been performed in cancer cells. Here, we used HIV-TAT (transactivator of transcription)-derived peptide to transfer the purified FHIT protein into HCC (hepatocellular carcinoma) cells and determine the biological effect of this fusion protein in inducing apoptosis. Affinity chromatography was used to purify TAT peptide-fused human FHIT (TAT-FHIT) protein from BL21 Escherichia coli. Immunofluorescence staining and Western blot analysis were performed to identify the expression and internalization of TAT-FHIT in HCC cells compared with the purified FHIT protein. Our study showed that TAT-FHIT protein can translocate into cancer cells in 1 h after incubation at 37°C. Furthermore, the results of MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide] assay, Annexin-V staining and Western blotting demonstrated that TAT-FHIT can robustly inhibit growth and induce apoptosis of HCC cells in vitro. In addition, a mechanistic study showed that both exogenous and intrinsic apoptotic pathways were involved in TAT-FHIT-mediated apoptosis and this effect could be attenuated partially by a mitochondrial protector TAT-BH4, indicating that mitochondrion plays a critical role in TAT-FHIT-mediated pro-apoptotic effect in cancer cells. Taken together, our study suggests that TAT-FHIT is a potential pro-apoptotic molecule in HCC cells and strengthen the hypothesis of its therapeutic application against HCC.

Prognostic markers and putative therapeutic targets for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most frequent human cancer and a fatal disease. Therapies with pharmacological agents do not improve the prognosis of patients with unresectable HCC. This emphasizes the need to identify new targets for early diagnosis, chemoprevention, and treatment of the disease. Available evidence indicates that clinical outcome of HCC could reflect the genetic predisposition to cancer development and progression. Numerous loci controlling HCC progression have been identified in rodents. In this review, we describe results of recent studies on effector mechanisms of susceptibility/resistance genes, responsible for HCC progression, aimed at identifying new putative prognostic markers and therapeutic targets of this tumor. Highest c-myc amplification and overexpression, alterations of iNOS crosstalk with IKK/NF-kB and RAS/ERK signaling, ubiquitination of ERK and cell cycle inhibitors, and deregulation of FOXM1 and cell cycle key genes occur in rapidly progressing dysplastic nodules and HCC, induced in genetic susceptible rat strains, compared to the lesions of resistant rats. Notably, alterations of these mechanisms in human HCC subtypes with poorer or better prognosis, are similar to those present in genetically susceptible and resistant rats, respectively, and function as prognostic markers and therapeutic targets. Attempts to cure advanced HCC by molecular therapy directed against specific targets led to modest survival benefit. Thus, efforts are necessary to identify and test, in pre-clinical and clinical studies, new therapeutic targets for combined molecular treatments of HCC. They may take advantage from the comparative analysis of signal transduction in HCCs differently prone to progress, in rats and humans.

Fragile histidine triad protein: structure, function, and its association with tumorogenesis

BACKGROUND

The human fragile histidine triad (FHIT) gene is a putative tumor suppressor gene, which is located at chromosome region 3p14.2. It was suggested that the loss of heterozygosity (LOH), homozygous deletions, and abnormal expression of the FHIT gene were involved in several types of human malignancies.

MATERIALS AND METHODS

To determine the role of FHIT in various cancers, we have performed structural and functional analysis of FHIT in detail.

RESULTS AND DISCUSSION

The protein FHIT catalyzes the Mg(2+) dependent hydrolysis of P1-5 cent-O-adenosine-P3-5 cent-O-adenosine triphosphate, Ap3A, to AMP, and ADP. The reaction is thought to follow a two-step mechanism. Histidine triad proteins, named for a motif related to the sequence H-cent-H-cent-H-cent-cent- (cent, a hydrophobic amino acid), belong to superfamily of nucleotide hydrolases and transferases. This enzyme acts on the R-phosphate of ribonucleotides, and contain a approximately 30-kDa domain that is typically a homodimer of approximately 15 kDa polypeptides with catalytic site.

CONCLUSION

Here we have gathered information is known about biological activities of FHIT, the structural and biochemical bases for their functions. Our approach may provide a comparative framework for further investigation of FHIT.

Recurrent and nonrandom DNA copy number and chromosome alterations in Myc transgenic mouse model for hepatocellular carcinogenesis: implications for human disease

Mouse models for hepatocellular carcinoma (HCC) provide an experimental ground for dissecting the genetic and biological complexities of human liver cancer and contribute to our ability to gain insights into the relevance of candidate cancer genes. We examined, using spectral karyotyping (SKY) and array-based CGH (aCGH), seven cell lines derived from HCC spontaneously developed in transgenic Myc mice (Myc), and four cell lines established from tumors induced in nude mice by inoculation with the original Myc cells (nuMyc). All the cell lines exhibited gain of material from chromosomes 5, 6, 8, 10, 11, 15, and 19 and DNA copy-number loss from chromosomes 2, 4, 7, 9, 12, 14, and X. In addition, several recurrent chromosome reorganizations were found, including del(3), t(3;8), del(4), t(4;11), t(6;5), del(7), del(8), del(9), t(10;14), del(11), and del(16). Chromosome breakpoints underlying rearrangements clustered in the regions previously identified as important for the early stages of Myc-induced hepatocarcinogenesis. The results strongly suggest the importance of recurrent breakage and loss of chromosomes 4, 9, and 14 and gain of chromosomes 15 and 19 in mouse liver neoplasia. Genomic changes observed in Myc HCC cell lines are also recurrent in HCC developed in other transgenic mouse models, in mouse spontaneous HCC and derivative cell lines, and in preneoplastic liver lesions induced with chemical carcinogens. Overall, the present results document selective, nonrandom genomic changes involving chromosomal regions homologous to those implicated in human HCC.

Effect of fragile histidine triad gene transduction on proliferation and apoptosis of human hepatocellular carcinoma cells

AIM: To evaluate the inhibitory effects of human fragile histidine triad (FHIT) gene on cell proliferation and apoptosis in human hepatocellular carcinoma line Hep3B in vitro.

METHODS: A recombinant pcDNA3.1 (+)/FHIT including the functional region of FHIT gene was constructed and transferred into human hepatocellular carcinoma cells in vitro. mRNA and protein expression of the FHIT gene in the transfected cells was detected by RT-PCR and Western blot, respectively. The effect of FHIT on proliferation was detected by MTT assay. Changes in cell cycle and apoptosis were assayed by flow cytometry. Five mice received subcutaneous transplantation of Hep3B-FHIT; 5 mice received subcutaneous transplantation of normal Hep3B and Hep3B-C as controls. The body weight of nude mice and tumor growth were measured.

RESULTS: RT-PCR and Western blot analysis showed that the expression level of FHIT-mRNA and FHIT protein was higher in Hep3B cells after infection with pcDNA3.1 (+)/FHIT. The growth of Hep3B cells treated with pcDNA3.1 (+)/FHIT was significantly inhibited. The pcDNA3.1 (+)/FHIT-transfected Hep3B cells showed a significantly higher cell rate at G₀-G₁ phase and increased apoptosis in comparison with controls (P < 0.05). The growth of transplanted tumor was inhibited markedly by FHIT. Tumors arising from the Hep3B-FHIT cells occurred much later than those arising from the Hep3B and Hep3B-C cells. The growth of Hep3B-FHIT cells was slow and the tumor volume was low.

CONCLUSION: Transduction of FHIT gene inhibits the growth of human hepatocellular carcinoma cells and induces cell apoptosis in vivo and in vitro.

Expression and DNA methylation patterns of Tslc1 and Dal-1 genes in hepatocellular carcinomas induced by N-nitrosodiethylamine in rats

To assess the involvement of the TSLC cascade in hepatocarcinogenesis, we investigated the expression and DNA methylation patterns of the genes Tslc1 and Dal-1 in hepatocellular carcinomas (HCC) induced using N-nitrosodiethylamine (DEN) in rats. Six-week-old male F344 rats received a single intraperitoneal injection of DEN at a dose of 10 mg/kg body weight, followed by combined treatment with partial hepatectomy and colchicine to induce cell-cycle disturbance and a selection procedure consisting of 2-acetylaminofluorene and carbon tetrachloride. Total RNA was extracted from 10 HCC, and the expression levels of Tslc1 and Dal-1 were measured using semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis. Three of 10 HCC showed reduced expression of Tslc1, compared with normal liver tissues, but no changes in the expression level of Dal-1 were found. For DNA methylation analysis, bisulfite sequencing was performed. The 5' upstream region of Tslc1 was methylated in the three HCC in which its expression was reduced, but was unmethylated in normal liver tissue. Western blot analysis also revealed reduced expression of Tslc1 protein in the three HCC. These results suggest that alterations to the TSLC cascade might have a role in hepatocarcinogenesis using DEN in rats.

Aberrant transcription of FHIT gene in intrahepatic cholangiocellular carcinomas induced by N-nitrosobis(2-oxopropyl)amine in hamsters

Aberrant transcription of the fragile histidine triad (FHIT) gene was investigated in intrahepatic cholangiocellular carcinomas (ICCs) induced by N-nitrosobis(2-oxopropyl)amine (BOP) in female Syrian golden hamsters. The animals received 70 mg/kg of BOP followed by repeated exposure to an augmentation pressure regimen consisting of a choline-deficient diet combined with DL-ethionine and then L-methionine and administration of 20 mg/kg BOP. A total of 14 ICCs were obtained 10 weeks after the beginning of the experiment and total RNAs were extracted from each for assessment of aberrant transcription of the FHIT gene by reverse transcription-polymerase chain reaction analysis. Aberrant transcripts were detected in four out of 14 ICCs (28.6%), as absence in the regions of nucleotides (nt) -75 to 279, nt -75 to 348 and nt -75 to 447. These results suggest that alteration of the FHIT gene may play a role in a small fraction of ICCs induced by BOP in the hamster.

Fhit gene alterations in hepatocarcinogenesis induced by a choline-deficient L-amino acid-defined diet in rats

Alterations of the fragile histidine triad (Fhit) gene were investigated in rat hepatocarcinogenesis induced by a choline-deficient L-amino acid-defined (CDAA) diet. Males of the F344 strain, 6 wk of age, were fed a CDAA diet, and subgroups were killed at 2, 4, 12, 20, and 75 wk after the beginning of the experiment. Fifteen hepatocellular carcinomas (HCCs) were noted in rats by the last time point; they were dissected free from the surrounding tissue. Normal control liver specimens were obtained from 6-wk-old rats. Total RNAs were extracted from whole livers of animals fed the CDAA diet for 2, 4, 12, and 20 wk and from HCCs, for assessment of aberrant transcription of the Fhit gene by reverse transcription-polymerase chain reaction. Aberrant transcripts were detected in livers of rats fed the CDAA diet for 4, 12, and 20 wk, but not 2 wk, as well as in 11 of 15 HCCs (73.3%). Southern blot analysis showed a genomic DNA abnormality in one of seven informative HCCs (14.3%), while Western blot analysis showed reduction of Fhit protein expression in seven of nine HCCs (77.8%). No abnormal expression was evident in the livers after exposure to the CDAA diet for 2-20 wk. These results suggest that Fhit alterations may play important roles in hepatocarcinogenesis due to choline deficiency in rats.

Alterations in the Fhit gene in pancreatic duct adenocarcinomas induced by N-nitrosobis(2-oxopropyl)amine in hamsters

Alteration of the Fhit gene was investigated in pancreatic duct adenocarcinomas induced by N-nitrosobis(2-oxopropyl)amine (BOP) in Syrian golden hamsters. The animals received 70 mg/kg BOP, followed by repeated exposure to an augmentation pressure regimen consisting of a choline-deficient diet combined with DL-ethionine and then L-methionine and administration of 20 mg/kg BOP. A total of 15 pancreatic duct adenocarcinomas were obtained 10 wk after the beginning of the experiment, and total RNAs were extracted from each for assessment of aberrant transcription of the Fhit gene by reverse transcription-polymerase chain reaction analysis. Aberrant transcripts lacking nucleotides in the regions of nt -75 to 348, nt -15 to 348, or nt -75 to 178 were detected in 11 adenocarcinomas (73.3%). Southern blot analysis of eight tumors did not show any evidence of gross rearrangement or deletion. These results indicated that changes in the Fhit gene occurred frequently and thus may have played a role in the development of pancreatic duct adenocarcinomas induced by BOP in hamsters.