Cloning and analysis of human UroplakinII promoter and its application for gene therapy in bladder cancer

Abstract

The differential expression of the desired gene product in the target tissue is central for gene therapy. One approach is to use a tissue-specific promoter to drive therapeutic gene expression. UroplakinII (UPII) is a urothelium-specific membrane protein. To investigate the feasibility of targeting gene therapy for bladder cancer, a DNA fragment of 2542-bp upstream of the UPII gene was amplified by PCR and linked to a promoterless firefly luciferase reporter gene. The transient transfection showed that the DNA fragment resulted in preferential expression in bladder carcinoma cells, with negligible expression in nonurothelium cells. Furthermore, the DNA segment located between -2545 and -1608 decided the tissue-specificity of the UPII promoter, the segment located between -328 and -4 being the core promoter of UPII. We generated two recombinant adenoviruses under the control of the UPII promoter: Ad-hUPII-GFP, carrying green fluorescence protein (GFP), and Ad-hUPII-TNF, carrying the tumor necrosis factor alpha (TNFalpha). ELISA revealed that the secretion of TNFalpha by Ad-hUPII-TNF-infected bladder cancer cells was significantly higher than Ad-hUPII-TNF-infected nonurothelium cells. The conditioned medium from Ad-hUPII-TNF-infected bladder cancer cells apparently inhibited the proliferation of L929 cells, a TNFalpha-sensitive cell line, comparing to Ad-hUPII-TNF-infected nonurothelium cells. Intravesical inoculation with Ad-hUPII-TNF inhibited tumor growth in the orthotopic human bladder cancer model. The sustained high level of TNFalpha in urine was identified with ELISA. Taken together, these data suggest that most of the cis elements that confer the bladder-specificity and differentiation-dependent expression of the human UPII gene reside in the 2542-bp sequence, and TNFalpha driven by the human UPII (hUPII) promoter is effective in the specific inhibition of bladder cancer growth both in vivo and in vitro. These results may yield a new therapeutic approach for bladder cancer and provide information on the molecular regulation of urothelial growth, differentiation, and disease.