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Novel approaches to cancer gene therapy currently exploit tumour hypoxia to achieve transcriptional targeting using oxygen-regulated enhancer elements called hypoxia response elements. The activity of such elements in hypoxic cells is directly dependent on upregulation of the hypoxia-inducible transcription factor-1 However tumours also contain areas of anoxia, which may be considered a more tumour-selective transcriptional stimulus than hypoxia for targeting gene therapy to tumours. Another element, from the rat virus-like retrotransposon, VL30 (termed the "secondary anoxia response element") has been reported to be more highly inducible in rat fibroblasts under anoxia than hypoxia. To investigate anoxia as a potential transcriptional target in human tumours, we have examined secondary anoxia response element inducibility in two human breast cancer cell lines, MCF-7 and T47D, under anoxia, hypoxia and normoxia. In both cell types, the trimerised secondary anoxia response element showed greater inducibility in anoxia than hypoxia (1% and 0.5% O(2)). The anoxic response of the secondary anoxia response element was shown to be dependent on hypoxia-inducible transcription factor-1 and the presence of a hypoxia-inducible transcription binding site consensus (5'-ACGTG-3'). Mutational analysis demonstrated that the base immediately 5' to this modulates the anoxic/hypoxic induction of the secondary anoxia response element, such that TACGTG>GACGTG>CACGTG. A similar correlation was found for erythropoietin, phosphoglycerate kinase 1, and aldolase hypoxia response elements, which contain these respective 5' flanking bases.

Original publication




Journal article


Br J Cancer

Publication Date





1173 - 1181


Animals, Breast Neoplasms, CHO Cells, Cell Hypoxia, Cricetinae, DNA-Binding Proteins, Erythropoietin, Female, Genetic Therapy, Humans, Hypoxia-Inducible Factor 1, Hypoxia-Inducible Factor 1, alpha Subunit, Nuclear Proteins, Oxygen, Rats, Response Elements, Retroelements, Transcription Factors, Tumor Cells, Cultured