Although NPC is a rare malignancy in most parts of the world, it is endemic in a few well-defined populations such as the natives in southeast Asia , and the incidence of NPC reported in southeast Asia is nearly 20-60 times higher than that reported in the Western countries [4, 5]. Development of NPCs are not well understood, the distinctive racial/ethnic and geographic distribution of NPC worldwide suggest that both genetic traits and environmental selleck products factors contribute to its development. Investigation of the molecular mechanisms could help illuminate the causes
and ultimately the prevention of this remarkable disease. There have been scanty but emerging reports on the importance of cytokines and growth factors in NPC, where most of these investigations have attempted to understand the roles played by cytokines and growth factors during development and chemoprevention in NPC. Of particular interest are the observations that NPC patients showed a lower level of transforming growth factor-β1 (TGF-β1) in plasma, but a high level in tumor tissues and surrounding stroma compared to the healthy controls [6–9]. The TGF-β signaling pathway may play an important role in the carcinogenesis of NPC. TGF-β belongs to a superfamily of structurally- and functionally-related
cytokines, where the members of this family regulate a wide spectrum ACY-241 chemical structure of CB-5083 concentration cellular responses, including cell proliferation, differentiation, adhesion, migration and apoptosis . It is now known that TGF-β is a cytokine that is a very potent inhibitor of cellular proliferation in normal cells. Evidence indicates that loss of the anti-proliferative
responsiveness to TGF-β is a characteristic of many tumor cells [11–13], suggesting potential roles of TGF-β and substantial components of the TGF-β signal transduction pathway as tumor suppressors . The Smad proteins are the Farnesyltransferase principal intracellular components of the TGF-β signaling pathway, and it has been demonstrated that Smad proteins represent the most direct mediators for the transmission of signal from the cell surface in the nucleus . Studies have shown that the expression of Smads is frequently altered in human cancers, for example, Smad4 has been found frequently inactivated in pancreatic [16, 17], biliary, and colorectal tumors . Increased expression of Smad6 and Smad7 has also been described in human pancreatic and prostate carcinomas [20, 21], respectively. The pathogenesis and the progression of numerous cancers have been attributed to the disruption of normal TGF-β signaling. However, the role of TGF-β signaling in the carcinogenesis of NPC is largely unknown, and it is not clear how NPC cells regulate TGF-β signaling in response to growth. Understanding the molecular mechanism underlying the TGF-β/Smad signaling pathway may provide a novel target for anticancer therapy.