Our findings identify miR-421 as a potent regulator of DPC4/Smad4, which may provide a novel therapeutic strategy for treatment of DPC4/Smad4-driven pancreatic cancer.
The most consistently mutated genes are <i>KRAS, CDKN2A, TP53</i>, and <i>SMAD4/DPC4</i> Study of familial PDAC has led to the recognition that a variety of defects in DNA repair genes can be associated with the emergence of pancreatic cancer.
We further investigated the function of Smad4 in human pancreatic cancer, in which loss-of-function mutations affecting Smad4 occur with a 50% frequency.
We investigated how maintenance of pancreatic cancer-initiating cells is influenced by Smad4, which is frequently deleted or mutated in pancreatic cancers cells.
Mechanisms of resistance to TGF-beta caused by modulation of cell cycle regulators and/or inactivation of components of the TGF-beta signaling transduction pathway such as C-myc and Smad4 have been demonstrated in human pancreatic cancer and squamous cell carcinoma cell lines.
Thus, oncogenic K-RAS/ERK in pancreatic adenocarcinoma facilitates TGFbeta-induced transcriptional down-regulation of the tumor suppressor PTEN in a SMAD4-independent manner and could constitute a signaling switch mechanism from growth suppression to growth promotion in pancreatic cancers.
Thus, adenovirus-mediated introduction of SMAD4 does not suppress in vitro growth in cells with completely inactivated SMAD4, and frequent loss of 18q at the SMAD4 locus is observed in pancreatic cancers but no abnormalities of the normal SMAD4 homolog have been detected.
These observations indicate that Smad4/Pten-mutant mice mimic the tumor progression of human pancreatic cancers that are driven by activation of the AKT-mTOR pathway, and uncovered a synergistic action of Smad4 and Pten in repressing pancreatic tumorigenesis.
Immunohistochemical studies for Madh4 protein in nine archival cancers (six pancreatic cancers, two duodenal cancers, and one biliary cancer) with known missense mutations indicated that all mutations within the MH1 or MH2 domain COOH-terminal to the MCR (seven of nine cases) had negative or weak labeling, whereas two cancers with mutations within the MCR had strong positive nuclear labeling for Madh4 protein.
Smad4 is an essential signal transducer of the transforming growth factor beta (TGF-beta) signalling pathway and has been identified as a tumour suppressor, being mutated in approx.50% of pancreatic cancers and approx.15% of colorectal cancers.
Our findings identify miR-483-3p as a potent regulator of DPC4/Smad4, which may provide a novel therapeutic strategy for the treatment of DPC4/Smad4-driven pancreatic cancer.
Utility of Assessing the Number of Mutated KRAS, CDKN2A, TP53, and SMAD4 Genes Using a Targeted Deep Sequencing Assay as a Prognostic Biomarker for Pancreatic Cancer.
Positive immunolabeling for p53 was observed in 57% of the familial pancreatic cancers and loss of SMAD4 labeling was observed in 61% of the familial pancreatic cancers, rates similar to those observed in sporadic pancreatic cancers.