Figure 4.

S1H inhibits hGH-mediated STAT5 phosphorylation in cultured cells. For these experiments, cells were treated with S1H peptide (0–200 nM) in the presence of 2.5 nM hGH for 20 min. Total protein was then extracted from the cells, and intracellular concentrations of pSTAT5 were evaluated by Western blot. Representative Western blot images (n = 3) are presented for cell lines expressing high levels of GHR. A, SK-MEL-28 cells; B MALME-3M cells; C, IM9 cells; and D, L (mouse fibroblast) cells. Size marker (kD) is shown to the right of the images. E, relative ratio of pSTAT5 to total STAT5 quantified from densitometry analysis of western blots shown in panels A–D. Error bars are standard deviation; ∗p < 0.05. AU, absorbance units; hGH, human growth hormone; GHR, growth hormone receptor.