p27 deficiency desensitizes Rb-/- cells to signals that trigger apoptosis during pituitary tumor development.

Low p27 expression in many human cancers is a prognostic indicator for poor outcome. While analysing the mechanism by which p27 deficiency contributed to tumor development in the Rb+/- mouse model, we identified a role for p27 as a proapoptotic tumor suppressor. We examined the cell cycle and apoptotic response of these pituitary tumor cells to the dopamine analog bromocriptine as well as the expression of Arf and other cell cycle and apoptotic regulators in these tumors.