Transcriptional targeting to anterior pituitary lactotrophic cells using recombinant adenovirus vectors in vitro and in vivo in normal and estrogen/sulpiride induced hyperplasic anterior pituitaries

SOUTHGATE, TD; WINDEATT, S; SMITH-ARICA, J; GERDES, CA; PERONE, MJ; MORRIS, I; DAVIS, JRE; KLATZMANN, D; LOWENSTEIN, PR; CASTRO, MG

ENDOCRINOLOGY

ENDOCRINE SOC

Año: 2000

0013-7227

The use of pituitary cell type-specific promoters is a powerful moleculartool to achieve pituitary cell type-specific transcriptional targetingof transgenes encoded by viral vectors. It has recently beenproposed that transcriptional targeting of therapeutic genes could beharnessed as a gene therapy strategy for the treatment of pituitarydisease. We describe the successful use of the human PRL promoter(hPrl) encoded within recombinant adenovirus vectors to target transgeneexpression of Herpes Simplex Virus Type 1-Thymidine Kinase(HSV1-TK) or b-galactosidase to lactotrophic cells in vitro and in vivo.Functionally, the restriction of expression of HSV1-TK to lactotrophictumor cells, using the hPrl promoter, resulted in the cell type-specificinduction of apoptosis in the lactotrophic GH3 tumor cell line, in thepresence of ganciclovir (GCV). In the corticotrophic AtT20 cell line, wedetected neither HSV1-TK expression, nor apoptosis in the presenceof GCV. The hPrl promoter encoded within a recombinant adenoviralvector also restricted transgene expression to lactotrophic cells inprimary anterior pituitary (AP) cultures, and importantly, within theanterior pituitary gland in vivo. When the HSV1-TK driven by hPrlpromoter was used in an in vivo model of estrogen/sulpiride lactotrophinduced hyperplasia within the AP in situ, the treatment was noteffective in either reducing the weight of the gland, the number oflactotrophic cells within the transduced area in vivo, or the circulatingPRL levels. This is in contrast to the human cytomegalovirus promoter(hCMV) driving expression of HSV1-TK in the same experimentalparadigm, which was effective in reducing pituitary weightand circulating PRL levels. Our results have important implicationsin the design of gene therapy strategies for pituitary tumors. Wedemonstrate that both the choice of the in vivo animal model, i.e.adenoma in the AP gland in situ, and the particular gene therapystrategy chosen, i.e. use of strong ubiquitous promoters vs. weaker butcell type-specific promoters, determine the experimental