The FoxO/Bcl-6/cyclin D2 pathway mediates metabolic and growth factor stimulation of proliferation in Min6 pancreatic β-cells

Lack of nutrients and growth factors activates FoxO transcription factors in pancreatic β-cells, whereas PI3K/Akt-dependent inactivation of FoxO favors proliferation. To address the link between FoxO and cell cycle control, we deprived Min6 cells of serum and glucose which activated FoxO and inhibited proliferation. Concomitantly, expression of the transcriptional repressor Bcl-6 was stimulated, whereas cyclin D2 was lowered. Gain of function approaches indicated that FoxO activation was sufficient to activate bcl-6 transcription, while Bcl-6 repressed cyclin D2 transcription and proliferation. Thus, in pancreatic β-cells, the FoxO/Bcl6/cyclin D2 pathway connects nutrient and growth factor status to cell cycle control, and may therefore be considered for its therapeutic potential in diabetes.