The Role of SMAD4 Inactivation in Epithelial-Mesenchymal Plasticity of Pancreatic Ductal Adenocarcinoma: The Missing Link?

Pancreatic ductal adenocarcinoma (PDAC) presents a five-year survival rate of 10% and its incidence increases over the years. It is, therefore, essential to improve our understanding of the molecular mechanisms that promote metastasis and chemoresistance in PDAC, which are the main causes of death in these patients. SMAD4 is inactivated in 50% of PDACs and its loss has been associated with worse overall survival and metastasis, although some controversy still exists. SMAD4 is the central signal transducer of the transforming growth factor-beta (TGF-beta) pathway, which is notably known to play a role in epithelial-mesenchymal transition (EMT). EMT is a biological process where epithelial cells lose their characteristics to acquire a spindle-cell phenotype and increased motility. EMT has been increasingly studied due to its potential implication in metastasis and therapy resistance. Recently, it has been suggested that cells undergo EMT transition through intermediary states, which is referred to as epithelial-mesenchymal plasticity (EMP). The intermediary states are characterized by enhanced aggressiveness and more efficient metastasis. Therefore, this review aims to summarize and analyze the current knowledge on SMAD4 loss in patients with PDAC and to investigate its potential role in EMP in order to better understand its function in PDAC carcinogenesis.

Automated summary

Pancreatic ductal adenocarcinoma (PDAC) has a low survival rate and its incidence is increasing over time. Understanding the molecular mechanisms behind metastasis and chemoresistance in PDAC is crucial, as these are the main causes of death in patients. SMAD4 is deactivated in half of PDAC cases and its loss is associated with worse overall survival and metastasis. SMAD4 is a key transducer in the TGF-beta pathway, which plays a role in epithelial-mesenchymal transition (EMT). EMT is a biological process where epithelial cells lose their characteristics and acquire a more mesenchymal phenotype, leading to increased motility. Recent studies suggest that cells may undergo intermediate states during EMT, known as epithelial-mesenchymal plasticity (EMP), which exhibit enhanced aggressiveness and more efficient metastasis. This review aims to summarize and analyze current knowledge on SMAD4 loss in PDAC patients and investigate its potential role in EMP, in order to better understand its function in PDAC carcinogenesis.