Evaluation of a new dual-specificity promoter for selective induction of apoptosis in breast cancer cells

Abstract

The conditional expression of lethal genes in tumor cells is a promising gene therapy approach for the treatment of cancer. The identification of promoters that are preferentially active in cancer cells is the starting point for this strategy. The combination of tissue -specific and tumor -specific elements offers the possibility to artificially develop such promoters. We describe the construction and characterization of a hybrid promoter for transcriptional targeting of breast cancer. In many cases, breast cancer cells retain the expression of estrogen receptors, and most solid tumors suffer from hypoxia as a consequence of their aberrant vascularization. Estrogen response elements and hypoxia -responsive elements were combined to activate transcription in cells that present at least one of these characteristics. When a promoter containing these elements is used to control the expression of the pro -apoptotic gene harakiri, the induction of cell death can be activated by estrogens and hypoxia, and inhibited by antiestrogens such as tamoxifen. Finally, we show evidence that these properties are maintained in the context of an adenoviral vector ( AdEHhrk ). Therefore, infection with this virus preferentially kills estrogen receptor ± positive breast cancer cells, or cells growing under hypoxic conditions. We propose the use of this promoter for transcriptional targeting of breast cancer. Cancer Gene Therapy ( 2001 ) 8, 298 ± 307

Antitumor Activity of an Oncolytic Adenoviral-CD40 Ligand (CD154) Transgene Construct in Human Breast Cancer Cells

“…1A). Validation studies by us and others (18,19) indicated that HIF-1a was markedly more effective in modulating AdEH viral gene expression than estrogen (data not shown). AdEHNull, a similar construct without the CD40L transgene, was created as a reference control for delineating CD40L transgene activity.…”

“…The premise that human breast cancer cells commonly express the estrogen receptor and HIF-1a (18,19) and are expected to provide a permissive environment for AdEH-based constructs were validated with multiple human breast cancer cell lines. We have examined the in vitro applicability of AdEHCD40L in terms of conditional CD40L expression and concomitant enhancement of antitumor activity in CD40…”

Transcriptional targeting modalities in breast cancer gene therapy using adenovirus vectors controlled by α-lactalbumin promoter

“…The most exciting results come from the study of TRRA that allows virus to propagate from a limited number of infected cells to the whole tumor mass, overcoming the problem of inadequate in vivo infectivity or biodistribution of adenovirus. TRRA has been explored to treat breast cancers in animal models (44,45) by using estrogen and hypoxia-responsive elements to limit the adenoviral replication in ER-positive cancer cells and in a hypoxic condition. Because the majority of ER-positive breast cancers can be effectively treated by hormonal therapy, the application of this strategy is limited for breast cancer treatment.…”

Novel chimeric gene promoters responsive to hypoxia and ionizing radiation

“…19 They are also characterized by flexibility, because several elements of different origin can be arranged in various orders, numbers and relative orientations, in order to optimize gene regulation. Dual-specificity promoters have been described containing HREs in combination with estrogen responsive promoters, 20 cytokine-inducible enhancers 21 and hepatoma-associated enhancers. 22 The results presented here indicate that combinations of HREs and CArG elements (also known as serum response elements or SREs) can act as gene enhancers, responding to hypoxic and radiation stimuli, at a level at least equivalent to that seen for the separate components (Figures 2-4).…”