Effects of GHR Silencing on GH and PRL Actions in Human T47D Breast Cancer Cells

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SAT 88-108-GHRH, GH & IGF Biology & Signaling
Saturday, June 15, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SAT-94
Dongmei Sun*, Jing Jiang and Stuart Jonathan Frank
University of Alabama at Birmingham, Birmingham, AL
Growth hormone receptor (GHR) and prolactin receptor (PRLR) are structurally similar members of the cytokine receptor superfamily. GH exerts metabolic and somatogenic effects, while PRL is responsible for lactation and has roles in breast development and function. In humans, GH can interact with both GHR and PRLR and PRL interacts only with PRLR. Both GHR and PRLR have been implicated as players in breast cancer. We previously demonstrated in human T47D breast cancer cells that both GHR and PRLR are expressed and associate with each other in a fashion that is enhanced by GH treatment (1). ShRNA-mediated knockdown of PRLR in these cells results in augmented GHR abundance with increased GHR protein half-life, enhanced acute GH-induced GHR tyrosine phosphorylation and STAT5 activation, and greater sensitivity to GHR-specific antagonists of GH signaling (2). We now explore the consequences of shRNA-mediated GHR silencing in T47D cells. Pools of cells stably transfected with each of four separate shRNAs targeting different regions of the GHR mRNA were selected. Each exhibited reduction of GHR protein by immunoblotting relative to T47D-SCR, a control transfectant in which a scrambled shRNA was expressed. Correspondingly, each of the four isolates exhibited increased immunoblottable long-form PRLR relative to T47D-SCR cells. One isolate, named T47D-ShGHR was chosen for further analysis. In concentration-dependence and time-course analyses, T47D-ShGHR cells exhibited robust GH- and PRL-induced STAT5 tyrosine phosphorylation, despite a marked reduction in mature GHR protein levels. Interestingly, GH-induced PRLR tyrosine phosphorylation was also enhanced in T47D-ShGHR cells and both GH- and PRL-induced STAT5 phosphorylation were inhibited by the PRLR-specific antagonist, G129R. Intriguingly, initial functional studies suggest that T47D-ShGHR cells also exhibit enhanced wound healing in a scratch assay. Further biochemical and functional characterization of GHR-deficient T47D cells are underway. Collectively, our data suggest that GHR and PRLR may physically and functionally interact in meaningful ways in breast cancer cells and may inform translationally-relevant investigation concerning GHR and PRLR antagonists and breast cancer.

(1) Xu, J., et al., Mol Endocrinol 2011; 25:597 (2) Xu, J., et al., Mol Endocrinol 2012, in press

Nothing to Disclose: DS, JJ, SJF

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: NIH R01 DK58259 (to SJF)