Israel Medical Association Journal

Background: The transfer of therapeutic genes into malignant brain tumors has been the subject of intense pre­clinical and clinical research in recent years. Most approaches have used direct intratumoral placement of a variety of vectors and genes, such as retroviruses or adenoviruses carrying drug-susceptibility genes, modified replication-competent herpes virus, and several vectors carrying tumor suppressor genes such as the p53 gene. However, clinical results have so far been disappointing, mainly due to the limited ability to effectively distribute the genetic material into the target cell population. Accordingly, alternative delivery approaches into the central nervous system, e.g., intravascular, are under investigation. Genetic vectors administered intravascularly are unlikely to penetrate the blood-brain barrier and transfer a gene into brain or tumor parenchyma. However, intravascular delivery of vectors may target endothelial cells lining the blood vessels of the brain. Since endothetial cells participate in a variety of physiological and pathological processes in the brain, their modulation by gene transfer may be used for a variety of therapeutic purposes. Angiogenically stimulated endothelial cells within tumors replicate rapidly and hence may become targets for retroviral-mediated gene transfer.

Objective: To assess the anti-tumor effect of transferring a drug-susceptibility gene into endothelial cells of the tumor vasculature.

Methods: As a model for this approach we delivered concentrated retroviral vectors carrying a drug-susceptibility gene via the internal carotid artery of rats with malignant brain tumors. The safety and efficacy of this approach, without and with subsequent treatment with a pro-drug (ganciclovir). was evaluated.

Results: No acute or long-term toxicity was observed after intraarterial infusion of the vector. Treatment with ganciclovir resulted in variable hemorrhagic necrosis of tumors, indicating preferential transduction of the angiogenically stimulated tumor vasculature. This was accompanied by severe toxicity caused by subarachnoid hemorrhage and intracerebral hemorrhage in vascular territories shared by the tumor and adjacent brain.

Conclusion: The data indicate that endothelial cells can be targeted by intraarterial delivery of retroviral vectors and can be used for devising new gene therapy strategies for the treatment of brain tumors.

Background: Data regarding the epidemiology of secondary pulmonary hypertension are scanty.

Objectives: To describe the spectrum and relative incidence of background diseases in patients with significant secondary PHT.

Methods: We identified 671 patients with systolic pulmonary artery pressure of 45 mm Hg or more from the database of the echocardiographic laboratory. Their background diseases were recorded and classified into three subgroups: cardiac, pulmonary and pulmonary vascular disease without pulmonary parenchymal disease. Age at the first echocardiographic study, gender and systolic PAP values were recorded. Data between the three subgroups were compared.

Results: The mean age of the patients was 6515 years, mean systolic PAP 6114 mm Hg and female:male ratio 1.21:1. At the time of diagnosis 85% of the patients were older than 50. PHT was secondary to cardiac disease in 579 patients (86.3%), to PVD without PPD in 54 patients (8%) and to PPD in only 38 patients (5.7%). Mean age and mean systolic PAP did not differ significantly among the three subgroups. There was a significantly higher female: male ratio in patients with PVD without PPD compared with cardiac or pulmonary diseases (1.7:1 vs. 1.2:1 and 1.7 vs. 0.8:1 respectively, P0.05).

Conclusions: The majority of patients with significant PHT are elderly with heart disease. PVD without PPD and chronic PPD are a relatively uncommon cause of significant PHT. Since the diagnosis of PHT is of clinical significance and sometimes merits different therapeutic interventions, we recommend screening by Doppler echocardiography for patients with high risk background diseases.