Loss of FHIT expression in transitional cell carcinoma of the urinary bladder.
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Cytogenetic and loss of heterozygosity (LOH) studies demonstrated chromosome 3p deletions in transitional cell carcinoma (TCC). We recently cloned the tumor suppressor gene FHIT (fragile histidine triad) at 3p14.2, one of the most frequently deleted chromosomal regions in TCC of the bladder, and showed that it is the target of environmental carcinogens. Abnormalities at the FHIT locus have been found in tumors of the lung, breast, cervix, head and neck, stomach, pancreas, and clear cell carcinoma of the kidney. We examined six TCC derived cell lines (SW780, T24, Hs228T, CRL7930, CRL7833, and HTB9) and 30 primary TCC of the bladder for the integrity of the FHIT transcript, using reverse transcriptase-polymerase chain reaction (RT-PCR) to investigate a potential role of the FHIT gene in TCC of the bladder. In addition, we tested expression of the Fhit protein in the six TCC-derived cell lines by Western blot analysis and in 85 specimens of primary TCCs by immunohistochemistry. Three of the six cell lines (50%) did not show the wild-type FHIT transcript, and Fhit protein was not detected in four of the six cell lines (67%) tested. Fhit expression also was correlated with pathological and clinical status. A significant correlation was observed between reduced Fhit expression and advanced stage of the tumors. Overall, 26 of 30 (87%) primary TCCs showed abnormal transcripts. Fhit protein was absent or greatly reduced in 61% of the TCCs analyzed by immunohistochemistry. These results suggested that loss of Fhit expression may be as important in the development of bladder cancer as it is for other neoplasms caused by environmental carcinogens. (+info)
Fhit-nucleotide specificity probed with novel fluorescent and fluorogenic substrates.
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Fhit, a member of the histidine triad superfamily of nucleotide-binding proteins, binds and cleaves diadenosine polyphosphates and functions as a tumor suppressor in human epithelial cancers. Function of Fhit in tumor suppression does not require diadenosine polyphosphate cleavage but correlates with the ability to form substrate complexes. As diadenosine polyphosphates are at lower cellular concentrations than mononucleotides, we sought to quantify interactions between Fhit and competitive inhibitors with the use of diadenosine polyphosphate analogs containing fluorophores in place of one nucleoside. Appp-S-(7-diethylamino-4-methyl-3-(4-succinimidylphenyl)) coumarin (ApppAMC), Appp-S-(4-4-difluoro-5,7-dimethyl-4-bora-3a, 4a-diaza-s-indacine-3-yl) methylaminoacetyl (ApppBODIPY), and GpppBODIPY, synthesized in high yield, are effective Fhit substrates, producing AMP or GMP plus fluorophore diphosphates. GpppBODIPY cleavage is accompanied by a 5.4-fold increase in fluorescence because BODIPY fluorescence is quenched by stacking with guanine. Titration of unlabeled diadenosine polyphosphates, inorganic pyrophosphate, mononucleotides, and inorganic phosphate into fluorescent assays provided values of K(m) and K(I) as competitive inhibitors. The data indicate that Fhit discriminates between good substrates via k(cat) and against cellular competitors in equilibrium binding terms. Surprisingly, pyrophosphate competes better than purine mononucleotides. (+info)
Restored expression of fragile histidine triad protein and tumorigenicity of cervical carcinoma cells.
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BACKGROUND: Allelic losses in the short arm of chromosome 3 are common in cervical carcinomas. The fragile histidine triad (FHIT) gene at chromosome region 3p14.2 is a candidate tumor suppressor gene that may play a role in cervical tumorigenesis. We and others have identified aberrant FHIT transcripts and frequent loss of Fhit protein expression in primary cervical cancers and high-grade noninvasive lesions but not in normal cervical tissues. The altered expression of FHIT may be due to somatic mutations or integration of human papillomavirus DNA at the FHIT locus. The purpose of this study was to determine whether ectopic expression of Fhit can suppress the tumorigenic properties of cervical cancer cells. METHODS: We employed infection with recombinant retroviruses as well as transfection of plasmid DNA to restore Fhit protein expression in cervical cancer cell lines lacking full-length FHIT transcripts and endogenous Fhit protein. The effects of Fhit expression on tumor cell morphology, anchorage-independent growth, and tumorigenicity in nude mice were examined. RESULTS: Stable overexpression of Fhit had no discernible effect on the tumorigenic properties of two cervical carcinoma cell lines or on a lung carcinoma cell line previously reported by others to be suppressed for tumorigenicity by Fhit. CONCLUSIONS: Restoration of Fhit expression does not suppress anchorage-independent growth or tumorigenicity of cervical carcinoma cell lines. However, it remains possible that FHIT inactivation may be important early in cervical tumor progression or that FHIT may suppress tumorigenesis in ways distinct from those measured by the assays employed in this study. (+info)
Alterations of the FHIT gene in human hepatocellular carcinoma.
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FHIT (fragile histidine triad), a candidate tumor suppressor gene, encompasses FRA3B, a region with the highest fragility in the human genome, and is altered in a large number of human cancers, particularly those of epithelial cell origin and associated with known carcinogenic agents. Human hepatocellular carcinoma (HCC), a major cancer worldwide, is closely related to carcinogenic agents such as hepatitis B and C virus infections, dietary aflatoxin, alcohol consumption, and exposure to chemical carcinogens. To assess the extent and the nature of the FHIT gene alterations and their implications in the development of HCC, several cell lines and primary tumors were cytologically and molecularly examined. The FHIT gene is expressed in normal hepatic cells and is not expressed or is abnormally expressed in cultured tumor cells derived from HCC. Down-regulation of the FHIT gene was detected by Northern blot analysis in 9 of 14 cell lines However, neither abnormal FHIT transcripts nor point mutations in DNA sequences of reverse transcription-PCR products (exons 2-9) were identified. Expression of FHIT protein was not detected by immunostaining in 5 of 10 primary tumors. Four cell lines showing mRNA down-regulation did not express FHIT protein as demonstrated by Western blot analysis. Allelic loss of intron 5 of the FHIT gene was detected in 10 of 34 informative samples from primary tumors. Structural alterations of chromosome 3p were identified in 8 of 13 HCC cell lines. Deletions or translocations involving region 3p14.2 were identified by fluorescence in situ hybridization with a YAC850A6 probe spanning the FHIT locus on chromosomes derived from cell lines with an abnormal FHIT gene expression. These combined results indicate that the FHIT gene is a frequent target and may be implicated in a subset of liver cancers. (+info)
Sequence-related protein export NTPases encoded by the conjugative transfer region of RP4 and by the cag pathogenicity island of Helicobacter pylori share similar hexameric ring structures.
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RP4 TrbB, an essential component of the conjugative transfer apparatus of the broad-host-range plasmid RP4, is a member of the PulE protein superfamily involved in multicomponent machineries transporting macromolecules across the bacterial envelope. PulE-like proteins share several well conserved motifs, most notable a nucleoside triphosphate binding motif (P-loop). Helicobacter pylori HP0525 also belongs to the PulE superfamily and is encoded by the pathogenicity island cag, involved in the inflammatory response of infected gastric epithelial cells in mammals. The native molecular masses of TrbB and HP0525 as determined by gel filtration and glycerol gradient centrifugation suggested a homohexameric structure in the presence of ATP and Mg(2+). In the absence of nucleotides and bivalent cations, TrbB behaved as a tetramer whereas the hexameric state of HP0525 remained unaffected. Electron microscopy and image processing demonstrated that TrbB and HP0525 form ring-shaped complexes (diameter: 12 nm) with a central region (diameter: 3 nm) of low electron density when incubated in the presence of ATP and Mg(2+). However, the TrbB average image appeared to be more elliptical with strong twofold rotational symmetry whereas HP0525 complexes are regular hexagons. Six well defined triangle-shaped areas of high electron density were distinguishable in both cases. Covalent crosslinking of TrbB suggests that the hexameric ring is composed from a trimer of dimers, because only dimeric, tetrameric, and hexameric species were detectable. The toroidal structure of TrbB and HP0525 suggests that both proteins catalyze a repetitive process, most probably translocating a cognate substrate across the inner membrane. (+info)
Altered expression of Fhit in carcinoma and precarcinomatous lesions of the esophagus.
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The FHIT gene, located at chromosome 3p14.2, is a tumor suppressor gene often involved in tumors resulting from exposure to environmental carcinogens. We studied 46 pairs of esophageal primary tumors and corresponding normal squamous mucosa specimens by molecular genetic and immunohistochemical methods to investigate the role of the FHIT gene in esophageal carcinoma. In addition, we studied several different types of lesions, such as carcinoma in situ or dysplasia by immunohistochemistry. Loss of heterozygosity at or around the FHIT gene was observed in 35 (76%) primary tumors. Immunohistochemical detection of Fhit protein in the primary tumors demonstrated that 14 (30%) were positive and 32 (70%) were negative. We observed concordance between loss of Fhit protein and loss of heterozygosity and between loss of Fhit protein and RNA abnormalities. Because the FHIT/FRA3B locus is susceptible to damage by environmental carcinogens, we investigated the correlation between Fhit expression and smoking or alcohol habits. In this relatively small study, the patients who were both heavy users of tobacco and alcohol showed a significantly higher frequency of loss of Fhit expression than those who were light users. Noncarcinomatous squamous epithelium showed positive Fhit reactivity in most cases; however, five showed negative Fhit reactivity. Interestingly, all of these five patients had habits of heavy use of tobacco and alcohol. Eight of 12 carcinomas in situ, 2 of 4 severe dysplasias, 4 of 8 moderate dysplasias, and 3 of 9 mild dysplastic lesions showed negative Fhit reactivity. These findings indicated that loss of Fhit expression may be an early event in the development of human esophageal carcinoma and may occur even in normal-appearing squamous epithelium in some patients heavily exposed to environmental carcinogens. (+info)
Abnormalities of the FHIT gene in human oral carcinogenesis.
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The abnormalities of the fragile histidine triad (FHIT) gene in tissue samples of oral squamous cell carcinomas (SCCs) along with several leukoplakias and an erythroplakia were examined to determine whether the FHIT gene is actually a frequent target in vivo for alteration during oral carcinogenesis. Abnormal transcripts of the FHIT gene were found in eight of 15 oral SCCs. Although these abnormal transcripts varied widely, deletion patterns incorporating a deletion of exon 5 were the most common. Loss of heterozygosity (LOH) analysis demonstrated that the abnormal FHIT transcripts found in cancer cells were attributable to abnormalities of the FHIT gene. Abnormal FHIT transcripts were also observed in two of seven premalignant lesions. Interestingly, in the case of one patient with a premalignant lesion showing an abnormal FHIT transcript, subsequent oral SCC developed during a 3-year follow-up period. On the other hand, in the two patients from whom both leukoplakia and SCC samples were taken simultaneously, abnormal FHIT transcripts were found only in the SCCs. Although the functional role of FHIT remains to be clarified, these results suggest that the FHIT alteration is actually involved in carcinogenesis of the oral epithelium. (+info)
Loss of Fhit expression in non-small-cell lung cancer: correlation with molecular genetic abnormalities and clinicopathological features.
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The FHIT gene is located at a chromosomal site (3p14.2) which is commonly affected by translocations and deletions in human neoplasia. Although FHIT alterations at the DNA and RNA level are frequent in many types of tumours, the biological and clinical significance of these changes is not clear. In this study we aimed at correlating loss of Fhit protein expression with a large number of molecular genetic and clinical parameters in a well-characterized cohort of non-small-cell lung cancers (NSCLCs). Paraffin sections of 99 non-small-cell carcinomas were reacted with an anti-Fhit polyclonal antibody in a standard immunohistochemical reaction. Abnormal cases were characterized by complete loss of cytoplasmic Fhit staining. The Fhit staining results were then correlated with previously obtained clinical and molecular data. Fifty-two of 99 tumours lacked cytoplasmic Fhit staining, with preserved reactivity in adjacent normal cells. Lack of Fhit staining correlated with: loss of heterozygosity (LOH) at the FHIT 3p14.2 locus, but not at other loci on 3p; squamous histology; LOH at 17p13 and 5q but not with LOH at multiple other suspected tumour suppressor gene loci; and was inversely correlated with codon 12 mutations in K-ras. Fhit expression was not correlated overall with a variety of clinical parameters including survival and was not associated with abnormalities of immunohistochemical expression of p53, RB, and p16. All of these findings are consistent with loss of Fhit protein expression being as frequent an abnormality in lung cancer pathogenesis as are p53 and p16 protein abnormalities and that such loss occurs independently of the commitment to the metastatic state and of most other molecular abnormalities. (+info)