Decreased efficiency of adenovirus-mediated gene transfer in aging cardiomyocytes.

BACKGROUND: Aging is an independent risk factor for the development of cardiovascular disease. Clinical application of myocardial gene transfer may be best suited in the elderly. In vivo gene transfer by adenovirus is less efficient in aging myocardium. METHODS AND RESULTS: When infected with adenovirus containing beta-galactosidase (beta-gal) and green fluorescent protein (GFP) driven by cytomegalovirus promoters in vitro, aging rat cardiac myocytes exhibit significantly lower infectivity and delayed transgene expression compared with adult controls. Abnormalities of viral internalization may be one mechanism accounting for this difference. To investigate this, we studied expression levels of the coxsackievirus and adenovirus receptor (CAR) as well as other potential integrins involved in the internalization of adenoviruses. CAR expression tended to be upregulated whereas among potential integrins, alpha(3)beta(1) was downregulated in aging cardiac myocytes. Blocking the beta(1) component of alpha(3)beta(1) further decreased infectivity, suggesting that the interaction between the penton base of the adenovirus and beta(1) maybe a crucial component of the viral entry mechanism. CONCLUSIONS: These results suggest that it is integrin-stimulated internalization rather than the adenovirus-CAR interaction that plays a vital role in adenoviral entry. The downregulation of integrins observed in senescent cells may be a key mechanism accounting for the decrease in viral infectivity seen in these cells. These findings have implications for the gene therapy treatment of myocardial failure in the elderly.

Eukaryotic Translation Initiation Factor 4E Is a Feed-Forward Translational Coactivator of Transforming Growth Factor ß Early Protransforming Events in Breast Epithelial Cells.

Eukaryotic translation initiation factor 4E (eIF4E) is overexpressed early in breast cancers in association with disease progression and reduced survival. Much remains to be understood regarding the role of eIF4E in human cancer. We determined, using immortalized human breast epithelial cells, that elevated expression of eIF4E translationally activates the transforming growth factor ß (TGF-ß) pathway, promoting cell invasion, a loss of cell polarity, increased cell survival, and other hallmarks of early neoplasia. Overexpression of eIF4E is shown to facilitate the selective translation of integrin ß1 mRNA, which drives the translationally controlled assembly of a TGF-ß receptor signaling complex containing α3ß1 integrins, ß-catenin, TGF-ß receptor I, E-cadherin, and phosphorylated Smad2/3. This receptor complex acutely sensitizes nonmalignant breast epithelial cells to activation by typically substimulatory levels of activated TGF-ß. TGF-ß can promote cellular differentiation or invasion and transformation. As a translational coactivator of TGF-ß, eIF4E confers selective mRNA translation, reprogramming nonmalignant cells to an invasive phenotype by reducing the set point for stimulation by activated TGF-ß. Overexpression of eIF4E may be a proinvasive facilitator of TGF-ß activity.