Endocrine Abstracts

Leptin is known to be produced by human pituitary adenomas, and inhibits the proliferation of HP75 cells in vitro. The HP75 cell line is derived from gonadotroph tumour cells from a clinically non-functioning human pituitary adenoma transfected with SV40. The aim of this study was to examine the effects of interleukins (IL) IL1-alpha and IL-6 on growth of HP75 cells and their effects on the growth inhibitory actions of leptin.

HP75 cells were plated in 24 well plates at a density of 30,000/well. IL-1alpha, IL-6 and leptin were added in varying concentrations after 24 hours. Incubation times were three and six days. Cell growth was assessed using Alamar Blue.

Leptin, IL-1alpha and IL-6 all significantly inhibited growth at 6 days. Results as mean% (sem)%. Maximal inhibitory effects for leptin were at 5x10(super)-7(/super)mol/L, 42% (2.8)% (p<0.01); IL-1alpha 100U/ml 24% (4.4)% (p<0.01); IL-6 100U/ml 39% (3.6) (p<0.01). No growth inhibitory effect was observed by leptin or IL-6 at 3 days. IL-1alpha inhibited growth by 54% after 3 days. The inhibitory effect of leptin on growth was unaffected by co-incubation with either IL-1alpha or IL-6.

In conclusion, we have demonstrated that these cytokines have delayed inhibitory effects on growth in HP75 pituitary tumour cells. IL-1alpha, IL-6 and leptin are known to be secreted from these cells as well as by human pituitary adenoma cells in culture. Whether or not the inhibitory effects of these cytokines are part of a cellular alarm response to try and retard growth has yet to be established.