Abstract
BackgroundSMAD4 is frequently inactivated and associated with a poor prognosis in pancreatic ductal adenocarcinoma (PDAC). Abnormal SMAD4 expression also plays an important role in the malignant progression of PDAC.MethodsWe investigated SMAD4 status in PDAC by immunohistochemical methods to explore the relationships between SMAD4 expression and clinicopathological features and then detected SMAD4 mutations by Sanger sequencing in 95 patients with PDAC to identify new mutation sites in PDAC. We further evaluated the effects of a missense mutation, Y353C, in the SMAD4 MH2 domain, on cell proliferation and migration in vitro.ResultsImmunohistochemistry showed that the expression of SMAD4 in PDAC carcinoma tissue was significantly lower than that in normal pancreatic tissue, and negative SMAD4 expression was closely related to tumour diameter, staging, lymph node metastasis and differentiation. Sanger sequencing analysis showed that the rate of SMAD4 mutation was 11.8% in 85 PDAC cases, and the novel SMAD4 Y353C missense mutation identified in this study promoted cell migration and invasion without affecting cell proliferation in vitro. Furthermore, SMAD4 Y353C resulted in reduced expression of E-cadherin and increased expression of Vimentin compared with wild-type SMAD4 overexpression.ConclusionThis study supports the key role of SMAD4 as a tumour suppressor gene in PDAC and shows that SMAD4 Y353C is associated with poor progression of PDAC.
Highlights
SMAD4 is frequently inactivated and associated with a poor prognosis in pancreatic ductal adenocarcinoma (PDAC)
Our experiment showed that SMAD4 Y353C inhibited the expression of the Ecadherin protein but increased the expression of Vimentin compared with the SMAD4 wild-type cell lines
This study indicated that SMAD4 overexpression inhibits migration and invasion and that this inhibitory effect is weakened in SMAD4 Y353C cells
Summary
SMAD4 is frequently inactivated and associated with a poor prognosis in pancreatic ductal adenocarcinoma (PDAC). It has been reported that pancreatic carcinoma involves an average of 63 genetic alterations mainly related to 12 cellular signalling pathways [8] and that the genetic lesions arise through activating mutations of KRAS and inactivation of the INK4A, p53-ARF and SMAD4 pathways [9,10,11]. The tumour suppressor gene SMAD4, originally detected on human chromosome 18q21.1, is commonly referred to as pancreatic cancer deletion gene (DPC4) because deficiency in its expression was first found in pancreatic cancer [12]. In 1996, Hanh et al [13, 14] found that SMAD4 deletion or mutation caused a loss of expression in 50% of pancreatic cancers.
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