6 - Signal Transduction

Abstract

This chapter discusses about different signaling molecules and pathways involved in pituitary tumorigenesis. Therapeutic approaches aiming signaling molecules as possible therapeutic targets are also highlighted. The most-studied and investigated cell signaling pathways involved in tumorigenesis are MAPKs, AKT, Ras, and Wnt intracellular cascades. Both AKT and MAPK pathways are enhanced in many pituitary tumors, leading to downregulation of physiological inhibitors of the cell cycle. These pathways interconnect at the level of intracellular signaling starting from TRKs and growth factor receptors and may constitute an early event in tumorigenesis. Disturbances have been reported in pituitary cell transformation at each level that links receptors to intracellular pathways and finally to development of a certain cellular function. In intracellular signaling pathways, a major molecule involved in pituitary tumorigenesis is PTTG, which is linked in an intricate network with hormones and growth factors. Increasing evidence supports a multifunctional role of PTTG1 in cell physiology and tumorigenesis. Tumorigenic mechanisms for PTTG1 action involve cell transformation, aneuploidy, apoptosis, angiogenesis, and tumorigenic microenvironment feedback.