The FHIT gene product: tumor suppressor and genome “caretaker”

The FHIT gene at FRA3B is one of the earliest and most frequently altered genes in the majority of human cancers. It was recently discovered that the FHIT gene is not the most fragile locus in epithelial cells, the cell of origin for most Fhit-negative cancers, eroding support for past claims that deletions at this locus are simply passenger events that are carried along in expanding cancer clones, due to extreme vulnerability to DNA damage rather than to loss of FHIT function. Indeed, recent reports have reconfirmed FHIT as a tumor suppressor gene with roles in apoptosis and prevention of the epithelial–mesenchymal transition. Other recent works have identified a novel role for the FHIT gene product, Fhit, as a genome “caretaker.” Loss of this caretaker function leads to nucleotide imbalance, spontaneous replication stress, and DNA breaks. Because Fhit loss-induced DNA damage is “checkpoint blind,” cells accumulate further DNA damage during subsequent cell cycles, accruing global genome instability that could facilitate oncogenic mutation acquisition and expedite clonal expansion. Loss of Fhit activity therefore induces a mutator phenotype. Evidence for FHIT as a mutator gene is discussed in light of these recent investigations of Fhit loss and subsequent genome instability.     

Blood 5-hydroxytryptamine in rats with pulmonary hypertension produced by ingestion ofCrotalaria spectabilis seeds

Zusammenfassung Der pulmonare Blutdruck in Ratten kann durch Abfütterung vonCrotalaria spectabilis erhöht werden, ohne die Konzentration des plasmafreien und an die Thrombozyten gebundenen 5-Hydroxytryptamins zu verändern.     

Immunization of mice against transplantable tumor

Zusammenfassung Nach i.p. Injektionen von mit Tween 80 behandelten Ehrlich-Lettré Ascites Krebszellen immunisierten Mäusen ergab sich bei diesen eine Widerstandsfähigkeit gegenüber Transplantaten von lebensfähigen Tumorzellen, woraus geschlossen wird, dass diese Behandlung die spezifischen Antigene der Zelloberfläche freisetzt.

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The research was supported by a grant from the Medical Research Council of Canada. I wish to thank Mrs.I. Gower for valuable technical assistance.     

Ethical principles and guidelines for scientific experiments on animals

Ethical principles and guidelines for scientific experiments on animals     

Evidence for gene transfer and expression of factor IX in haemophilia B patients treated with an AAV vector

Pre-clinical studies in mice and haemophilic dogs have shown that introduction of an adeno-associated viral (AAV) vector encoding blood coagulation factor IX (FIX) into skeletal muscle results in sustained expression of F.IX at levels sufficient to correct the haemophilic phenotype. On the basis of these data and additional pre-clinical studies demonstrating an absence of vector-related toxicity, we initiated a clinical study of intramuscular injection of an AAV vector expressing human F.IX in adults with severe haemophilia B. The study has a dose-escalation design, and all patients have now been enrolled in the initial dose cohort (2 x 10(11) vg/kg). Assessment in the first three patients of safety and gene transfer and expression show no evidence of germline transmission of vector sequences or formation of inhibitory antibodies against F.IX. We found that the vector sequences are present in muscle by PCR and Southern-blot analyses of muscle biopsies and we demonstrated expression of F.IX by immunohistochemistry. We observed modest changes in clinical endpoints including circulating levels of F.IX and frequency of FIX protein infusion. The evidence of gene expression at low doses of vector suggests that dose calculations based on animal data may have overestimated the amount of vector required to achieve therapeutic levels in humans, and that the approach offers the possibility of converting severe haemophilia B to a milder form of the disease.     

In vivo rupture of the imidazole ring of histamine

Zusammenfassung Es wird gezeigt, dass Histamin auch durch das Aufreissen des Imidazolringes im Vormagen von Schafen katabolisiert werden kann. C¹⁴-markiertes Histamin wurde in den Pansen des Schafes oral eingeführt und annähernd 30% davon in der Atmungsluft (CO₂) aufgefangen.     

Somatic integration and long-term transgene expression in normal and haemophilic mice using a DNA transposon system

The development of non-viral gene-transfer technologies that can support stable chromosomal integration and persistent gene expression in vivo is desirable. Here we describe the successful use of transposon technology for the nonhomologous insertion of foreign genes into the genomes of adult mammals using naked DNA. We show that the Sleeping Beauty transposase can efficiently insert transposon DNA into the mouse genome in approximately 5-6% of transfected mouse liver cells. Chromosomal transposition resulted in long-term expression (>5 months) of human blood coagulation factor IX at levels that were therapeutic in a mouse model of haemophilia B. Our results establish DNA-mediated transposition as a new genetic tool for mammals, and provide new strategies to improve existing non-viral and viral vectors for human gene therapy applications.