The invention provides nonhuman transgenic animals with a disrupted FHIT gene. The invention further provides transgenic mice in which one or both Fhit alleles have been inactivated. Preferably, the Fhit-deficient mice develop multiple tumors of both visceral and sebaceous origin, similar to those of Muir-Torre familial cancer syndrome. The present invention further relates to the generation of these transgenic mice and their use as model systems to study the effects of carcinogenic agents in promoting clonal expansion of neoplastic cells in cancers, preferably gastrointestinal cancers of which Muir-Torre syndrome is a subset. The invention further relates to testing therapeutic agents for their efficacy in the prevention and treatment of cancer, preferably gastrointestinal cancer.

MUIR-TORRE-LIKE SYNDROME IN Fhit DEFICIENT MICE

Inactivation of FHIT, a tumor suppressor gene, is found in a large fraction of cells that are either premalignant or malignant. The present invention relates to gene therapy wherein the FHIT gene is administered, either in vivo or ex vivo, to a patient to inhibit tumor development. The gene therapy methods of the present invention will be used in the treatment of disorders involving an overproliferation of cells. Further, the gene therapy methods of the present invention are useful in protecting a patient that is predisposed to developing a cancer.

/pdf/fhit-gene-therapy-prevents-tumor-development-in-fhit-3x76ln8eqh.pdf

Fhit gene therapy prevents tumor development in fhit-deficient mice

In this matched case-control study nested within the prospective Physicians' Health Study, we evaluated whether DNA damage in blood samples collected at enrollment significantly predicted risk, consistent with our hypothesis that cases have greater biological susceptibility to polycyclic aromatic hydrocarbons and other aromatic tobacco carcinogens. The subjects were 89 cases of primary lung cancer and 173 controls, all males, matched on smoking, age, and duration of follow-up. Aromatic-DNA adducts were measured in WBCs by the nuclease P1-enhanced (32)P-postlabeling method that primarily detects smoking-related adducts. Among current smokers, but not former or nonsmokers, there was a significant increase in mean adduct levels of cases compared with controls (11.04 versus 5.63; P = 0.03). "Healthy" current smokers who had elevated levels of aromatic DNA adducts in WBCs were approximately three times more likely to be diagnosed with lung cancer 1-13 years later than current smokers with lower adduct concentrations (odds ratio, 2.98; 95% confidence interval, 1.05-8.42; P = 0.04). We were not able to discern case-control differences in former smokers and nonsmokers. The findings are of interest because they suggest that individuals who become cases have greater biological susceptibility to tobacco carcinogens, a biological difference, which manifests most clearly while exposure is ongoing.

/pdf/association-between-carcinogen-dna-adducts-in-white-blood-3lex24p8s2.pdf

Association between Carcinogen-DNA Adducts in White Blood Cells and Lung Cancer Risk in the Physicians Health Study

The field of molecular epidemiology is very promising, as sophisticated techniques are being developed to address etiology, genetic susceptibility and mechanisms for induction of disease. The use of biomarkers plays a key role in these investigations because the information can be used to predict the development of disease and to implement disease prevention programs. However, as emphasized by Frederica P. Perera, the field is strewn with studies either that failed to use validated biomarkers or whose designs did not adequately consider the biology of the endpoints, and the availability of validated biomarkers of health risk is still limited. In this review, we have briefly described the usefulness of certain biomarkers for the documentation of exposure and early biological effects, with special concern for the prediction of cancer. An emphasis is placed on understanding the biological and health significance of biomarkers. By building reliable biomarker databases, a promising future is the integration of information from the genome programs to expand the scientific frontiers on etiology, health risk prediction and prevention of environmental disease.

Biomarkers in molecular epidemiology studies for health risk prediction.

In 1979, the first chromosome alteration associated with familial cancer was reported. Five years later, a fragile site was observed in the same chromosome region. The product of the fragile histidine triad (FHIT) gene, which encompasses this fragile site, is partially or entirely lost in most human cancers, indicating that it has a tumour-suppressor function. Inactivation of only one FHIT allele compromises this suppressor function, indicating that a 'one-hit' mechanism of tumorigenesis is operative. Are genes disrupted at other fragile sites? And, are these genes also tumour suppressors?

FRA3B and other common fragile sites: the weakest links.

A full-length cDNA for a novel isoform of the human receptor tyrosine phosphatase gamma gene (PTPRG) was overexpressed in Sf9 insect cells, and the gene product, PTP gamma, was purified and characterized. The protein was expressed as a M(r) approximately 185,000 protein accompanied by a M(r) approximately 120,000 putative cleavage product on SDS-PAGE analysis. The protein undergoes N-linked glycosylation and constitutive phosphorylation of serine residues. When assayed for tyrosine-specific phosphatase activity, PTP gamma dephosphorylated myelin basic protein at a pH optimum of 7.5 and a Km of 12.6 microM; reduced carboxyamidomethylated and maleylated lysozyme (RCM-lysozyme) at a pH optimum of 6.0 and a Km of 12 microM; and p-nitrophenylphosphate with a pH optimum of 5.5 and a Km of 3.5 mM. Phosphatase activity was inhibited by ZnCl2 and sodium orthovanadate; Mg2+, Mn2+, and Ca2+ ions were ineffective. The partially purified form of the enzyme was allosterically activated by triphosphorylated nucleosides, with a preference for purines. This activation was prevented by Mg2+ addition and did not occur when a purified form of the enzyme was utilized, suggesting that its activation depends on specific activating factors or conformational constraints. Interestingly, PTP gamma protein was specifically bound by an ATP-agarose matrix through its intracellular domain, suggesting a link between binding of nucleotides and activation of the phosphatase.

https://cancerres.aacrjournals.org/content/canres/55/21/4855.full.pdf

Characterization of the receptor protein tyrosine phosphatase gene product PTP gamma: binding and activation by triphosphorylated nucleosides.

The murine Fhit locus maps near the centromere v proximal Ptprg locus on mouse chromosome 14. The cDNA sequence and structure are similar to those of the human gene, with exons 5–9 encoding the protein. The predominant mRNA in the tissues and cell lines tested was an alternatively spliced form missing exon 3. Most murine cell lines tested, including lines established from normal mouse embryos and tumors, expressed very low or undetectable levels of Fhit mRNA. Most normal mouse tissues expressed wild-type Fhit mRNA, whereas ∼40% of murine lung carcinomas expressed wild-type and aberrant Fhit RT-PCR products that lacked various exons. Several tumorigenic mouse cell lines exhibited homozygous deletions of Fhit exons. We conclude that the murine Fhit gene, like its human counterpart, is a target of alterations involved in murine carcinogenesis.

/pdf/the-murine-fhit-locus-isolation-characterization-and-4wdye8ouo7.pdf

Jeannine Mendrola

Papers

Characterization of the receptor protein tyrosine phosphatase gene product PTP gamma: binding and activation by triphosphorylated nucleosides.

The Murine Fhit Locus: Isolation, Characterization, and Expression in Normal and Tumor Cells

Receptor Protein Tyrosine Phosphatase Gamma, Ptpγ, Regulates Hematopoietic Differentiation