Figure 8.

Autocrine growth inhibition by transforming growth factor β (TGFβ) in neuroendocrine tumour (NET) cells. (A) BON and LCC-18 cells (1.5×10⁴) were seeded and attached overnight. Cells were then incubated with 10 ng/ml TGFβ-1, a neutralising anti-TGFβ antibody (TGFβ-ab) or irrelevant control antibody (data not shown) at a final concentration of 20 μg/ml for three days. Cell number was then determined and expressed as a per cent of untreated controls. For determination of DNA synthesis, BON cells were incubated with TGFβ-1 or a neutralising anti-TGFβ antibody for 72 hours. For the last six hours, BrdU was added and DNA synthesis was then quantified by ELISA. Data represent mean (SEM) from three separate experiments, each conducted in triplicate (*p<0.05). (B) BON cells were stably transfected with a dn-TGFβR II-GFP expression construct or mock transfected with the GFP vector alone. Expression of the dn-TGFβR II-GFP fusion protein was verified by membrane localisation. (C) Transfected cell lines were analysed for growth as indicated under (A) to confirm the autoinhibitory action of endogenous TGFβ in BON cells. Shown are the mean (SEM) of three independent experiments, each performed in triplicate (*p<0.05).