Activation of protein kinase Cδ leads to increased pancreatic acinar cell dedifferentiation in the absence of MIST1

Abstract

Pancreatic ductal adenocarcinoma (PDAC) has a 5 year survival rate post-diagnosis of < 5%. Individuals with chronic pancreatitis (CP) are 20-fold more likely to develop PDAC, making it a significant risk factor for PDAC. While the relationship for the increased susceptibility to PDAC is unknown, loss of the acinar cell phenotype is common to both pathologies. Pancreatic acinar cells can dedifferentiate or trans-differentiate into a number of cell types including duct cells, β cells, hepatocytes and adipocytes. Knowledge of the molecular pathways that regulate this plasticity should provide insight into PDAC and CP. MIST1 (encoded by Bhlha15 in mice) is a transcription factor required for complete acinar cell maturation. The goal of this study was to examine the plasticity of acinar cells that do not express MIST1 (Mist1(-/-) ). The fate of acinar cells from C57Bl6 or congenic Mist1(-/-) mice expressing an acinar specific, tamoxifen-inducible Cre recombinase mated to Rosa26 reporter LacZ mice (Mist1(CreERT/-) R26r) was determined following culture in a three-dimensional collagen matrix. Mist1(CreERT/-) R26r acini showed increased acinar dedifferentiation, formation of ductal cysts and transient increases in PDX1 expression compared to wild-type acinar cells. Other progenitor cell markers, including Foxa1, Sox9, Sca1 and Hes1, were elevated only in Mist1(-/-) cultures. Analysis of protein kinase C (PKC) isoforms by western blot and immunofluorescence identified increased PKCε accumulation and nuclear localization of PKCδ that correlated with increased duct formation. Treatment with rottlerin, a PKCδ-specific inhibitor, but not the PKCε-specific antagonist εV1-2, reduced acinar dedifferentiation, progenitor gene expression and ductal cyst formation. Immunocytochemistry on CP or PDAC tissue samples showed reduced MIST1 expression combined with increased nuclear PKCδ accumulation. These results suggest that the loss of MIST1 is a common event during PDAC and CP and events that affect MIST1 function and expression may increase susceptibility to these pathologies.

Ribonucleoprotein HNRNPA2B1 Interacts With and Regulates Oncogenic KRAS in Pancreatic Ductal Adenocarcinoma Cells

“…Although further investigation about the requirement of KRAS phosphorylation in gastrointestinal malignancies needs to be performed, it is worth mentioning that the putative kinase PKCδ is elevated in PDAC 8,68 and several studies highlight PKC inhibition as an effective therapy in PDAC cell lines. 69,70 Our data support a role for the new KRAS interactor HNRNPA2B1 as a regulator of KRASdependent tumorigenesis through the critical PDAC signaling pathway PI3K/AKT.…”

“…[3][4][5] Mutational activation of KRAS in these tissues is sufficient to initiate neoplasia in mice. [6][7][8] The most prevalent oncogenic mutation in KRAS is at codon 12 (66% KRAS mutations) 4 and preserve the GTPbound active state by inhibiting intrinsic GTPase activity or interfering with the action of GAPs.…”

Silencing of the Fibroblast growth factor 21 gene is an underlying cause of acinar cell injury in mice lacking MIST1

“…Pancreata were dissected and acini isolated as described previously (22). In some instances, isolated acini were processed for RNA or protein within an hour of isolation.…”

“…Fgf21: 6774352) or 18S rRNA. Realtime qRT-PCR was performed on cDNA samples prepared as described (22). Using mitochondrial ribosomal protein L1 (Mrpl1) as a normalization control, ViiA 7 RUO software (Applied Biosystems) was used to calculate the amount of RNA relative to untreated or saline treatment for the equivalent time points.…”

“…Mist1 Ϫ/Ϫ acinar cells also exhibit increased proliferation rates (20,42) and are significantly more likely to undergo acinar-to-duct cell metaplasia (22), providing a potential link to pancreatic ductal adenocarcinoma (PDAC). We have recently shown loss of MIST1 accumulation in human samples from chronic pancreatitis and PDAC (22). These observations indicate that loss of MIST1 is a key event in progressing from healthy to diseased pancreatic tissue.…”