The growth inhibitory effect of of anti growth hormone (G144K) on canine mammary carcinomas

Abstract

One out of four intact bitches will develop mammary gland tumours. Current therapy is surgical removal of the neoplasm but this is insufficient in most cases. It is suspected that growth hormone plays an important role in mammary gland tumourgenesis and could serve as a target for novel therapy strategies. Aim of this study is to prove effi-cacy of a canine anti growth hormone on inhibitory effects on GHR and its possible therapeutic application on canine mammary carcinomas. Canine pituitary growth hor-mone was collected from a healthy dog’s pituitary and sequenced. A point mutation was made on amino acid 144 to transform Glycin into Lysin, creating a growth hor-mone mutant (G144K). Inhibitory effects of G144K were tested in a pGH/G144K coïn-cubation experiment using a HEK 293 cell line containing a rabbit GHR (rGHR). The HEK293/rGHR cells were transfected with a Renilla construct and a Stat5 SpiLuc con-struct to determine respectively cell viability and STAT5 activity as a function of GHR activation. Stimulation of the rGHR was achieved by using 2,27 nmol/ml of pGH solu-tion and lead to a 7 fold increase of basal Stat5 activity. Coïncubation with 208 nmol/ml G144K disabled pGH from stimulating rGHR, thus Stat5 levels remaining at basal activity. Canine growth hormone mutant G144K is able to inhibit rGHR activa-tion with biological active pGH. The inhibitory properties of G144K could be of use in canine medicine and especially in canine mammary gland carcinomas, but more re-search is needed to further analyse and improve the inhibitory effects of G144K.