ST6Gal1 sialyltransferase promotes pancreatic ductal adenocarcinoma by facilitating acinar to ductal metaplasia
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ABSTRACT: RNA-Seq analyses of pancreata from mice with expression of the following genes: (1) "KC" mice with KRasG12D; (2) "KSC" mice with dual expression of KRasG12D and ST6Gal1 (3) "SC" mice with expression of ST6Gal1; and (4) "WT" mice representing littermate controls lacking Cre expression.
Project description:This study describes a novel function for the ST6GAL1 sialyltransferase in promoting acinar to ductal metaplasia (ADM). ST6GAL1 activity facilitates ADM by reprogramming acinar cells into a more progenitor-like state.
Project description:The role of aberrant glycosylation in pancreatic ductal adenocarcinoma (PDAC) remains an under-investigated area of research. In this study, we determined that ST6 β-galactoside α2,6 sialyltransferase 1 (ST6GAL1), which adds α2,6-linked sialic acids to N-glycosylated proteins, was upregulated in patients with early-stage PDAC and was further increased in advanced disease. A tumor-promoting function for ST6GAL1 was elucidated using tumor xenograft experiments with human PDAC cells. Additionally, we developed a genetically engineered mouse (GEM) model with transgenic expression of ST6GAL1 in the pancreas and found that mice with dual expression of ST6GAL1 and oncogenic KRASG12D had greatly accelerated PDAC progression compared with mice expressing KRASG12D alone. As ST6GAL1 imparts progenitor-like characteristics, we interrogated ST6GAL1's role in acinar to ductal metaplasia (ADM), a process that fosters neoplasia by reprogramming acinar cells into ductal, progenitor-like cells. We verified ST6GAL1 promotes ADM using multiple models including the 266-6 cell line, GEM-derived organoids and tissues, and an in vivo model of inflammation-induced ADM. EGFR is a key driver of ADM and is known to be activated by ST6GAL1-mediated sialylation. Importantly, EGFR activation was dramatically increased in acinar cells and organoids from mice with transgenic ST6GAL1 expression. These collective results highlight a glycosylation-dependent mechanism involved in early stages of pancreatic neoplasia.
Project description:Aberrant acinar to ductal metaplasia (ADM), one of the earliest events involved in exocrine pancreatic cancer development, is typically studied using pancreata from transgenic mouse models. We used primary, human pancreatic acinar cells to evaluate the transcriptional profile during the course of ADM.
Project description:Pancreatic ductal adenocarcinoma (PDAC) is a deadly disease when diagnosed at a late stage, however patient survivorship significantly increases when the disease is detect prior to metastasis. To study the earliest events leading to PDAC initiation, we developed a genetically engineered mouse model of PDAC utilizing a tamoxifen-inducible Cre Recombinase knocked into the transcription factor Ptf1a locus to induce expression of oncogenic KrasG12D and Trp53R270H alleles in adult pancreatic acinar cells. Mice of the genotype KrasLSL-G12D/+; Trp53LSL-R270H/+; Ptf1aCreERTM/+ (KPT) developed PDAC following tamoxifen injection while control Cre recombinase negative KrasLSL-G12D/+; Trp53LSL-R270H/+; (KP) mice injected with tamoxifen did not develop PDAC. Acinar cells comprising the pancreata of tamoxifen treated KPT mice we observed to undergo acinar to ductal metaplasia (ADM), and formed precancerous lesions. We used laser capture microdissection (LCM) and RNA sequencing to generate, to our knowledge, the first transcriptional profile of an enriched population of metaplastic acinar cells in situ. Comparing the transcriptional profile of metaplastic acinar cells with the transcriptional profile of healthy pancreatic tissue identified differentially expressed genes associated with ADM. Ingenuity pathway analysis revealed transcriptional regulators and canonical signaling pathways involved in ADM. LCM was used to generate a transactional profile of cancer cells isolated from pancreatic tumors, and differential gene expression analysis revealed a subset of genes which are overexpressed in both ADM and PDAC relative to healthy pancreas. Further analysis of genes expressed in both pancreatic cancer precursor ADM lesions and invasive PDAC may lead to the identification of novel biomarkers of PDAC.
Project description:Oncogenic KrasG12D, a driver mutation of pancreatic ductal adenocarcinoma (PDAC), induces neoplastic transformation of acinar cells through acinar-to-ductal metaplasia (ADM). Here, we show that both functional complexes of mTOR (mechanistic target of rapamycin kinase, mTORC1 and mTORC2) are specifically activated in ADM. Murine models uncover that mTORC1 and mTORC2 cooperate to promote KrasG12D-driven ADM development. Proteomic analyses identify Arp2/3 complex, an actin nucleator, as the common downstream effector: mTORC1 is responsible for the protein synthesis of Rac1 and Arp3 while mTORC2 promotes the Arp2/3 complex activity via Akt/Rac1 signalling. Genetic ablation of Arp2/3 complex completely arrests KrasG12D-driven ADM development. The Arp2/3 complex-mediated y-branching of actin network promotes the basolateral spread of filamentous actin, which is indispensable for acinar cells-initiated carcinogenesis. Induced by oncogenic KrasG12D, ADM is a metaplastic phenotype of acinar cells that requires extensive actin rearrangements. mTORC1 and mTORC2, downstream targets of KrasG12D, have well-established oncogenic functions in PDAC development. The actin-related protein 2/3 (Arp2/3) complex is the first identified actin nucleator. Regarded as textbook knowledge, it is activated by EGFR/Rac1 signalling to promote the polymerisation of branched actin filaments from pre-existing filaments in numerous biological contexts. Hereby, we identify that mTORC1 and mTORC2 attain a dual, yet non-redundant, regulatory role in promoting Arp2/3 complex function, which is responsible for generating basolateral filamentous actin in ADM. Thus, the role of Arp2/3 complex fills up the missing gap between putative oncogenic signals and actin dynamics underlying PDAC initiation.
Project description:Acinar cells have been proposed as a cell-of-origin for pancreatic intraepithelial neoplasia (PanIN) after undergoing a highly regulated acinar to ductal metaplasia (ADM) process. ADM can be triggered by pancreatitis causing acinar cells de-differentiate to a ductal-like state. We identify Fra1 (gene name Fosl1) as the most enriched transcription factor during KrasG12D acute pancreatitis mediated injury. We have elucidated the functional role of Fra1 by generating an acinar-specific Fosl1 knockout mouse expressing KrasG12D (Ptf1aCreERT;KrasG12D;Fosl1fl/fl;YFP) . Using single nuclei ATAC-seq and bulk-RNA seq, we used pseudotime analysis and developed a gene-regulatory network governing de-differentiation to demonstrate that Fosl1 knockout mice are delayed in the onset of ADM and accompanying recovery. Fosl1 depletion prevents the pro-inflammatory effects of G-CSF, an ADM-promoting cytokine, suggesting that the G-CSF/Fra1 signaling axis can modulate ADM. Overall, our studies mark the first time a discrete transcriptional factor has been linked to the temporal regulation of ADM.
Project description:Background and aimsAberrant acinar to ductal metaplasia (ADM), one of the earliest events involved in exocrine pancreatic cancer development, is typically studied using pancreata from genetically engineered mouse models.MethodsWe used primary, human pancreatic acinar cells from organ donors to evaluate the transcriptional and pathway profiles during the course of ADM.ResultsFollowing 6 days of three-dimensional culture on Matrigel, acinar cells underwent morphological and molecular changes indicative of ADM. mRNA from 14 donors' paired cells (day 0, acinar phenotype and day 6, ductal phenotype) was subjected to whole transcriptome sequencing. Acinar cell specific genes were significantly downregulated in the samples from the day 6 cultures while ductal cell-specific genes were upregulated. Several regulons of ADM were identified including transcription factors with reduced activity (PTF1A, RBPJL, and BHLHA15) and those ductal and progenitor transcription factors with increased activity (HNF1B, SOX11, and SOX4). Cells with the ductal phenotype contained higher expression of genes increased in pancreatic cancer while cells with an acinar phenotype had lower expression of cancer-associated genes.ConclusionOur findings support the relevancy of human in vitro models to study pancreas cancer pathogenesis and exocrine cell plasticity.
Project description:Animal studies suggest that pancreatitis-induced acinar-to-ductal metaplasia (ADM) is a key event for pancreatic ductal adenocarcinoma (PDAC) initiation. However, there has not been an adequate system to explore the mechanisms of human ADM induction. We have developed a flow cytometry-based, high resolution lineage tracing method and 3D culture system to analyse ADM in human cells. In this system, well-known mouse ADM inducers did not promote ADM in human cells. In contrast, TGF-β1 efficiently converted human acinar cells to duct-like cells (AD) in a SMAD-dependent manner, highlighting fundamental differences between the species. Functionally, AD cells gained transient proliferative capacity. Furthermore, oncogenic KRAS did not induce acinar cell proliferation, but did sustain the proliferation of AD cells, suggesting that oncogenic KRAS requires ADM-associated-changes to promote PDAC initiation. This ADM model provides a novel platform to explore the mechanisms involved in the development of human pancreatic diseases.