Heat-induced gene expression as a novel targeted cancer gene therapy strategy

One of the main advantages of gene therapy over traditional therapy is the potential to target the expression of therapeutic genes in desired cells or tissues. To achieve targeted gene expression, we experimented with a new a pproach based on the long-established phenomenon of the heat shock response , ny using the green fluorescence protein as a reporter gene, it was demons trated that expression of a heterologous gene with a heat shock protein 70 promoter could be elevated to 500-1000-fold over background by moderate hyp erthermia (39 degrees C to 43 degrees C) in tissue cultured cells. The heat -induced green fluorescence protein expression was first detectable at 3 h after heating and reached a maximum at 18-24 h. The expression dropped back to baseline within 72 h, In addition, when cells were infected with adenov irus vectors containing the heat-inducible interleukin 12 or tumor necrosis factor alpha genes and then heated (42 degrees C, 30 min), expression was at least 13,600- or 6.8 x 10(5)-fold over background, respectively. Intrale sion injection of the interleukin-12-carrying adenovirus vector in a mouse melanoma tumor model caused significant tumor growth delay only with hypert hermia treatment. Our results therefore support heat-induced gene expressio n as a feasible approach for targeted cancer gene therapy.