Reconstitution of human PDAC using primary cells reveals oncogenic transcriptomic features at tumor onset.

Animal studies have demonstrated the ability of pancreatic acinar cells to transform into pancreatic ductal adenocarcinoma (PDAC). However, the tumorigenic potential of human pancreatic acinar cells remains under debate. To address this gap in knowledge, we expand sorted human acinar cells as 3D organoids and genetically modify them through introduction of common PDAC mutations. The acinar organoids undergo dramatic transcriptional alterations but maintain a recognizable DNA methylation signature. The transcriptomes of acinar organoids are similar to those of disease-specific cell populations. Oncogenic KRAS alone do not transform acinar organoids. However, acinar organoids can form PDAC in vivo after acquiring the four most common driver mutations of this disease. Similarly, sorted ductal cells carrying these genetic mutations can also form PDAC, thus experimentally proving that PDACs can originate from both human acinar and ductal cells. RNA-seq analysis reveal the transcriptional shift from normal acinar cells towards PDACs with enhanced proliferation, metabolic rewiring, down-regulation of MHC molecules, and alterations in the coagulation and complement cascade. By comparing PDAC-like cells with normal pancreas and PDAC samples, we identify a group of genes with elevated expression during early transformation which represent potential early diagnostic biomarkers.

TGFß and Hippo Signaling Pathways Coordinate to Promote Acinar to Ductal Metaplasia in Human Pancreas.

BACKGROUND & AIMS: Acinar-to-ductal metaplasia (ADM) serves as a precursor event in the development of pancreatic ductal adenocarcinoma (PDAC) upon constitutive environmental and genetical stress. While the role of ADM in PDAC progression has been established, the molecular mechanisms underlying human ADM remain elusive. We previously demonstrated the induction of ADM in human acinar cells through the transforming growth factor beta (TGFß) signaling pathway. We aim to investigate the interaction between TGFß and Hippo pathways in mediating ADM. METHODS: RNA-sequencing was conducted on sorted normal primary human acinar, ductal, and AD (acinar cells that have undergone ADM) cells. ATAC-seq analysis was utilized to reveal the chromatin accessibility in these three cell types. ChIP-Seq of YAP1, SMAD4, and H3K27ac was performed to identify the gene targets of YAP1 and SMAD4. The role of YAP1/TAZ in ADM-driven cell proliferation, as well as in oncogenic KRAS driven proliferation, was assessed using sphere formation assay. RESULTS: AD cells have a unique transcription profile, with upregulated genes in open chromatin states in acinar cells. YAP1 and SMAD4 co-occupy the loci of ADM-related genes, including PROM1, HES1, and MMP7, co-regulating biological functions such as cell adhesion, cell migration, and inflammation. Overexpression of YAP1/TAZ promoted acinar cell proliferation but still required the TGFß pathway. YAP1/TAZ were also crucial for TGFß-induced sphere formation and were necessary for KRAS-induced proliferation. CONCLUSIONS: Our study reveals the intricate transition between acinar and AD states in human pancreatic tissues. It unveils the complex interaction between the Hippo and TGF-ß pathways during ADM, highlighting the pivotal role of YAP1/TAZ and SMAD4 in PDAC initiation.

Hippo Signaling Pathway in Pancreas Development.

The Hippo signaling pathway is a vital regulator of pancreatic development and homeostasis, directing cell fate decisions, morphogenesis, and adult pancreatic cellular plasticity. Through loss-of-function research, Hippo signaling has been found to play key roles in maintaining the proper balance between progenitor cell renewal, proliferation, and differentiation in pancreatic organogenesis. Other studies suggest that overactivation of YAP, a downstream effector of the pathway, promotes ductal cell development and suppresses endocrine cell fate specification via repression of Ngn3. After birth, disruptions in Hippo signaling have been found to lead to de-differentiation of acinar cells and pancreatitis-like phenotype. Further, Hippo signaling directs pancreatic morphogenesis by ensuring proper cell polarization and branching. Despite these findings, the mechanisms through which Hippo governs cell differentiation and pancreatic architecture are yet to be fully understood. Here, we review recent studies of Hippo functions in pancreatic development, including its crosstalk with NOTCH, WNT/ß-catenin, and PI3K/Akt/mTOR signaling pathways.

Ductal vs. acinar? Recent insights into identifying cell lineage of pancreatic ductal adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is a deadly disease with a 5-year survival rate of less than 8%. To date, there are no early detection methods or effective treatments available. Many questions remain to be answered in regards to the pathogenesis of PDAC, among which, the controversy over the cell lineage of PDAC demands more attention. Ductal cells were originally thought to be the cell of origin for PDAC due to the ductal morphology of most cases of PDAC. However, recent studies have demonstrated that acinar cells are more sensitive to KRAS mutation and tend to develop to PanIN and PDAC effectively, very likely by undergoing acinar to ductal metaplasia into a transient state that contributes to PDAC initiation. There is also evidence that both ductal and acinar cells can potentially develop to PDAC when exposed to certain genetic settings and stimuli, suggesting that more scrutiny is required for the identification of the true cell lineage of individual cases of PDAC. In this work, we summarize recent findings in the identification of the cellular origin of PDAC, with the goal of advancing our knowledge on the initiation and progression of the disease. We also discuss various models and techniques for investigating early events of PDAC. Better understanding of these cellular events is crucial to identify new methods for the early diagnosis and treatment of PDAC.

Activation of the intrinsic fibroinflammatory program in adult pancreatic acinar cells triggered by Hippo signaling disruption.

Damaged acinar cells play a passive role in activating pancreatic stellate cells (PSCs) via recruitment of immune cells that subsequently activate PSCs. However, whether acinar cells directly contribute to PSC activation is unknown. Here, we report that the Hippo pathway, a well-known regulator of proliferation, is essential for suppression of expression of inflammation and fibrosis-associated genes in adult pancreatic acinar cells. Hippo inactivation in acinar cells induced yes-associated protein 1 (YAP1)/transcriptional coactivator with PDZ binding motif (TAZ)-dependent, irreversible fibrosis and inflammation, which was initiated by Hippo-mediated acinar-stromal communications and ameliorated by blocking YAP1/TAZ target connective tissue growth factor (CTGF). Hippo disruption promotes acinar cells to secrete fibroinflammatory factors and induce stromal activation, which precedes acinar proliferation and metaplasia. We found that Hippo disruption did not induce cell-autonomous proliferation but primed acinar cells to exogenous pro-proliferative stimuli, implying a well-orchestrated scenario in which Hippo signaling acts as an intrinsic link to coordinate fibroinflammatory response and proliferation for maintenance of the tissue integrity. Our findings suggest that the fibroinflammatory program in pancreatic acinar cells is suppressed under normal physiological conditions. While transient activation of inflammatory gene expression during tissue injury may contribute to the control of damage and tissue repair, its persistent activation may result in tissue fibrosis and failure of regeneration.

SIRT6-mediated transcriptional suppression of Txnip is critical for pancreatic beta cell function and survival in mice.

AIMS/HYPOTHESIS: Better understanding of how genetic and epigenetic components control beta cell differentiation and function is key to the discovery of novel therapeutic approaches to prevent beta cell dysfunction and failure in the progression of type 2 diabetes. Our goal was to elucidate the role of histone deacetylase sirtuin 6 (SIRT6) in beta cell development and homeostasis. METHODS: Sirt6 endocrine progenitor cell conditional knockout and beta cell-specific knockout mice were generated using the Cre-loxP system. Mice were assayed for islet morphology, glucose tolerance, glucose-stimulated insulin secretion and susceptibility to streptozotocin. Transcriptional regulatory functions of SIRT6 in primary islets were evaluated by RNA-Seq analysis. Reverse transcription-quantitative (RT-q)PCR and immunoblot were used to verify and investigate the gene expression changes. Chromatin occupancies of SIRT6, H3K9Ac, H3K56Ac and active RNA polymerase II were evaluated by chromatin immunoprecipitation. RESULTS: Deletion of Sirt6 in pancreatic endocrine progenitor cells did not affect endocrine morphology, beta cell mass or insulin production but did result in glucose intolerance and defective glucose-stimulated insulin secretion in mice. Conditional deletion of Sirt6 in adult beta cells reproduced the insulin secretion defect. Loss of Sirt6 resulted in aberrant upregulation of thioredoxin-interacting protein (TXNIP) in beta cells. SIRT6 deficiency led to increased acetylation of histone H3 lysine residue at 9 (H3K9Ac), acetylation of histone H3 lysine residue at 56 (H3K56Ac) and active RNA polymerase II at the promoter region of Txnip. SIRT6-deficient beta cells exhibited a time-dependent increase in H3K9Ac, H3K56Ac and TXNIP levels. Finally, beta cell-specific SIRT6-deficient mice showed increased sensitivity to streptozotocin. CONCLUSIONS/INTERPRETATION: Our results reveal that SIRT6 suppresses Txnip expression in beta cells via deacetylation of histone H3 and plays a critical role in maintaining beta cell function and viability. DATA AVAILABILITY: Sequence data have been deposited in the National Institutes of Health (NIH) Gene Expression Omnibus (GEO) with the accession code GSE104161.

Breast conserving therapy with accelerated partial breast versus external beam whole breast irradiation: comparison of imaging sequela and complications in a matched population.

Our purpose was to evaluate and compare the imaging sequela and complications of accelerated partial breast irradiation (APBI) with those occurring in patients treated with standard external beam therapy. Patient selection included those who met the criteria for possible ABPI: age 45 or older; cancer stage T1N0M0 or ductal carcinoma in situ 3 cm or less, and negative surgical margins. One hundred and ninety seven had complete records and films available for review. Ninety-seven (49%) were treated with APBI (MammoSite) and 100(51%) were treated with external beam. Image findings for APBI versus external beam were: distortion 90(93%) versus 83(83%), seroma 67(69%) versus 7(7%), skin edema 52(54%) versus 47(47%), increased stroma 75(77%) versus 66(66%), calcifications 10(10%) versus 6(6%), and fat necrosis 12(12%) versus 6(6%). For APBI, skin and stromal edema was more commonly focal. At imaging, the seroma rate was statistically and significantly different between the two treatment modes (p < 0.0001). For patients treated with APBI, seroma formation was not related to balloon size and only weakly related to lumpectomy cavity size. The complication rate was significantly higher for those treated with APBI (36 versus 20%) and the types and treatment of complications differed. There were three recurrences among the APBI group and none among those treated with external beam radiation.

Are you ready?--lessons learned from the Fort Hood shooting in Texas.

On November 5, 2009, a US Army psychiatrist allegedly opened fire with one or more handguns, killing 12 military personnel and one civilian at Fort Hood in Killeen, Texas. The most severely wounded casualties were transported to Scott and White Memorial Hospital, a Level I trauma center and tertiary care teaching hospital in Temple, Texas associated with the Texas A&M University College of Medicine. Ten victims arrived in a 1-h period with another two arriving in the second hour, necessitating an emergency response to a mass casualty event. Our radiology department's response was largely unplanned and was therefore the result of many spontaneous actions and ideas. We share our experiences and from them formulate guidelines for a general radiology surge model for mass casualty events. It is our hope to raise awareness and help other radiology departments to prepare for such an unexpected event.

Is the chest x-ray an appropriate screening exam for ER patients with AMS?

Emergency department patients with altered mental status (AMS) regularly undergo a routine chest radiograph at our institution. While there are many causes of chest pathology seen on the chest radiograph that may cause an altered mental status, it is not clear that a routine chest radiograph for these patients affects management. The goal of this study is to determine if a chest radiograph is an appropriate screening examination for AMS. This is a retrospective review of 100 consecutive patients who underwent head computed tomography for altered mental status in the emergency department and had a chest radiograph during the same visit. Of 100 patients undergoing a routine chest radiograph for AMS, 17 had findings which altered patient care, 15 of those had signs/symptoms which clearly indicated that a chest radiograph was needed, and the other two had leukocytosis. The routine performance of a chest radiograph in the setting of a patient presenting to the emergency department with altered mental status affected medical management in 17%, a modest benefit. The positive predictive value of a chest x-ray in these patients may be improved if certain symptomatologies are present.