An important problem in the development of gene therapy approaches in oncology is the necessity of using promoters that provide specific and high levels of gene expression in tumor cells. To solve this problem, we used an inducible system of gene expression regulation (Tat-TAR system), which is used by the human immunodeficiency virus (HIV). tat and tk-HSV genes, as well as a fragment of LTR HIV-1, were cloned into the retrovirus vector. The tk-HSV gene was under the control of the LTR HIV-1 fragment. The potential capacity of these constructions for transactivating tk-HSV gene transcription was studied. Basal expression level of this gene was defined in the transient transfection of HEK293 cells. It was shown that the specific transactivation of tk-HSV gene was controlled by the LTR HIV-1 fragment in lung carcinoma cells Calu-1 permanently transfected with the tat gene construction. The effect of the transactivation of tk-HSV transcription in the Tat-TAR system was demonstrated in Calu-1 cells that express tge tat gene under the control of a tumor-specific BIRC5 promoter. © 2009 Allerton Press, Inc.