Overexpression of TGF alpha in transgenic mice: induction of epithelial hyperplasia, pancreatic metaplasia, and carcinoma of the breast

Deciphering cellular plasticity in pancreatic cancer for effective treatments

Cellular plasticity and therapy resistance are critical features of pancreatic cancer, a highly aggressive and fatal disease. The pancreas, a vital organ that produces digestive enzymes and hormones, is often affected by two main types of cancer: the pre-dominant ductal adenocarcinoma and the less common neuroendocrine tumors. These cancers are difficult to treat due to their complex biology characterized by cellular plasticity leading to therapy resistance. Cellular plasticity refers to the capability of cancer cells to change and adapt to different microenvironments within the body which includes acinar-ductal metaplasia, epithelial to mesenchymal/epigenetic/metabolic plasticity, as well as stemness. This plasticity allows heterogeneity of cancer cells, metastasis, and evasion of host's immune system and develops resistance to radiation, chemotherapy, and targeted therapy. To overcome this resistance, extensive research is ongoing exploring the intrinsic and extrinsic factors through cellular reprogramming, chemosensitization, targeting metabolic, key survival pathways, etc. In this review, we discussed the mechanisms of cellular plasticity involving cellular adaptation and tumor microenvironment and provided a comprehensive understanding of its role in therapy resistance and ways to overcome it.

ST6GAL1 sialyltransferase promotes acinar to ductal metaplasia and pancreatic cancer progression

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.

p53 inhibitor iASPP is an unexpected suppressor of KRAS and inflammation-driven pancreatic cancer

Oncogenic KRAS activation, inflammation and p53 mutation are key drivers of pancreatic cancer (PC) development. Here we report iASPP, an inhibitor of p53, as a paradoxical suppressor of inflammation and oncogenic KRAS^G12D-driven PC tumorigenesis. iASPP suppresses PC onset driven by KRAS^G12D alone or KRAS^G12D in combination with mutant p53^R172H. iASPP deletion limits acinar-to-ductal metaplasia (ADM) in vitro but accelerates inflammation and KRAS^G12D-induced ADM, pancreatitis and PC tumorigenesis in vivo. KRAS^G12D/iASPP^Δ8/Δ8 tumours are well-differentiated classical PCs and their derivative cell lines form subcutaneous tumours in syngeneic and nude mice. Transcriptomically, either iASPP deletion or p53 mutation in the KRAS^G12D background altered the expression of an extensively overlapping gene set, comprised primarily of NF-κB and AP1-regulated inflammatory genes. All these identify iASPP as a suppressor of inflammation and a p53-independent oncosuppressor of PC tumorigenesis.

Pancreatic cancer epigenetics: adaptive metabolism reprograms starving primary tumors for widespread metastatic outgrowth

Pancreatic cancer is a paradigm for adaptation to extreme stress. That is because genetic drivers are selected during tissue injury with epigenetic imprints encoding wound healing responses. Ironically, epigenetic memories of trauma that facilitate neoplasia can also recreate past stresses to restrain malignant progression through symbiotic tumor:stroma crosstalk. This is best exemplified by positive feedback between neoplastic chromatin outputs and fibroinflammatory stromal cues that encase malignant glands within a nutrient-deprived desmoplastic stroma. Because epigenetic imprints are chemically encoded by nutrient-derived metabolites bonded to chromatin, primary tumor metabolism adapts to preserve malignant epigenetic fidelity during starvation. Despite these adaptations, stromal stresses inevitably awaken primordial drives to seek more hospitable climates. The invasive migrations that ensue facilitate entry into the metastatic cascade. Metastatic routes present nutrient-replete reservoirs that accelerate malignant progression through adaptive metaboloepigenetics. This is best exemplified by positive feedback between biosynthetic enzymes and nutrient transporters that saturate malignant chromatin with pro-metastatic metabolite byproducts. Here we present a contemporary view of pancreatic cancer epigenetics: selection of neoplastic chromatin under fibroinflammatory pressures, preservation of malignant chromatin during starvation stresses, and saturation of metastatic chromatin by nutritional excesses that fuel lethal metastasis.

Acinar cells and the development of pancreatic fibrosis

Pancreatic fibrosis is caused by excessive deposition of extracellular matrixes of collagen and fibronectin in the pancreatic tissue as a result of repeated injury often seen in patients with chronic pancreatic diseases. The most common causative conditions include inborn errors of metabolism, chemical toxicity and autoimmune disorders. Its pathophysiology is highly complex, including acinar cell injury, acinar stress response, duct dysfunction, pancreatic stellate cell activation, and persistent inflammatory response. However, the specific mechanism remains to be fully clarified. Although the current therapeutic strategies targeting pancreatic stellate cells show good efficacy in cell culture and animal models, they are not satisfactory in the clinic. Without effective intervention, pancreatic fibrosis can promote the transformation from pancreatitis to pancreatic cancer, one of the most lethal malignancies. In the normal pancreas, the acinar component accounts for 82% of the exocrine tissue. Abnormal acinar cells may activate pancreatic stellate cells directly as cellular source of fibrosis or indirectly via releasing various substances and initiate pancreatic fibrosis. A comprehensive understanding of the role of acinar cells in pancreatic fibrosis is critical for designing effective intervention strategies. In this review, we focus on the role of and mechanisms underlying pancreatic acinar injury in pancreatic fibrosis and their potential clinical significance.

Muc4 loss mitigates epidermal growth factor receptor activity essential for PDAC tumorigenesis

Mucin4 (MUC4) appears early during pancreatic intraepithelial neoplasia-1 (PanIN1), coinciding with the expression of epidermal growth factor receptor-1 (EGFR). The EGFR signaling is required for the onset of Kras-driven pancreatic ductal adenocarcinoma (PDAC); however, the players and mechanisms involved in sustained EGFR signaling in early PanIN lesions remain elusive. We generated a unique Esai-CRISPR-based Muc4 conditional knockout murine model to evaluate its effect on PDAC pathology. The Muc4 depletion in the autochthonous murine model carrying K-ras and p53 mutations (K-rasG12D; TP53R172H; Pdx-1cre, KPC) to generate the KPCM4-/- murine model showed a significant delay in the PanIN lesion formation with a significant reduction (p < 0.01) in EGFR (Y1068) and ERK1/2 (T202/Y204) phosphorylation. Further, a significant decrease (p < 0.01) in Sox9 expression in PanIN lesions of KPCM4-/- mice suggested the impairment of acinar-to-ductal metaplasia in Muc4-depleted cells. The biochemical analyses demonstrated that MUC4, through its juxtamembrane EGF-like domains, interacts with the EGFR ectodomain, and its cytoplasmic tail prevents EGFR ubiquitination and subsequent proteasomal degradation upon ligand stimulation, leading to sustained downstream oncogenic signaling. Targeting the MUC4 and EGFR interacting interface provides a promising strategy to improve the efficacy of EGFR-targeted therapies in PDAC and other MUC4-expressing malignancies.

NFATc1 Is a Central Mediator of EGFR-Induced ARID1A Chromatin Dissociation During Acinar Cell Reprogramming

BACKGROUND & AIMS

Loss of AT-rich interactive domain-containing protein 1A (ARID1A) fosters acinar-to-ductal metaplasia (ADM) and pancreatic carcinogenesis by down-regulating transcription programs controlling acinar cell identity. However, how ARID1A reacts to metaplasia-triggering environmental cues remains elusive. Here, we aimed to elucidate the role of ARID1A in controlling ductal pancreatic gene signatures and deciphering hierarchical signaling cues determining ARID1A-dependent chromatin regulation during acinar cell reprogramming.

METHODS

Acinar cell explants with differential ARID1A status were subjected to genome-wide expression analyses. The impact of epidermal growth factor receptor (EGFR) signaling, NFATc1 activity, and ARID1A status on acinar reprogramming processes were characterized by ex vivo ADM assays and transgenic mouse models. EGFR-dependent ARID1A chromatin binding was studied by chromatin immunoprecipitation sequencing analysis and cellular fractionation.

RESULTS

EGFR signaling interferes with ARID1A-dependent transcription by inducing genome-wide ARID1A displacement, thereby phenocopying ARID1A loss-of-function mutations and inducing a shift toward ADM permissive ductal transcription programs. Moreover, we show that EGFR signaling is required to push ARID1A-deficient acinar cells toward a metaplastic phenotype. Mechanistically, we identified the transcription factor nuclear factor of activated T cells 1 (NFATc1) as the central regulatory hub mediating both EGFR signaling-induced genomic ARID1A displacement and the induction of ADM-promoting gene signatures in the absence of ARID1A. Consequently, pharmacologic inhibition of NFATc1 or its depletion in transgenic mice not only preserves genome-wide ARID1A occupancy, but also attenuates acinar metaplasia led by ARID1A loss.

CONCLUSIONS

Our data describe an intimate relationship between environmental signaling and chromatin remodeling in orchestrating cell fate decisions in the pancreas, and illustrate how ARID1A loss influences transcriptional regulation in acinar cell reprogramming.

Generation of Hydrogen Peroxide and Downstream Protein Kinase D1 Signaling Is a Common Feature of Inducers of Pancreatic Acinar-to-Ductal Metaplasia

Pancreatic acinar-to-ductal metaplasia (ADM) is a reversible process that occurs after pancreatic injury, but becomes permanent and leads to pancreatic lesions in the presence of an oncogenic mutation in KRAS,. While inflammatory macrophage-secreted chemokines, growth factors that activate epidermal growth factor receptor (EGFR) and oncogenic KRAS have been implicated in the induction of ADM, it is currently unclear whether a common underlying signaling mechanism exists that drives this process. In this study, we show that different inducers of ADM increase levels of hydrogen peroxide, most likely generated at the mitochondria, and upregulate the expression of Protein Kinase D1 (PKD1), a kinase that can be activated by hydrogen peroxide. PKD1 expression in acinar cells affects their survival and mediates ADM, which is in part due to the PKD1 target NF-κB. Overall, our data implicate ROS-PKD1 signaling as a common feature of different inducers of pancreatic ADM.

Acinar to ductal cell trans-differentiation: A prelude to dysplasia and pancreatic ductal adenocarcinoma

Pancreatic cancer (PC) is the deadliest neoplastic epithelial malignancies and is projected to be the second leading cause of cancer-related mortality by 2024. Five years overall survival being ~10%, mortality and incidence rates are disturbing. Acinar to ductal cell metaplasia (ADM) encompasses cellular reprogramming and phenotypic switch-over, making it a cardinal event in tumor initiation. Differential cues and varied regulatory factors drive synchronous functions of metaplastic cell populations leading to multiple cell fates and physiological outcomes. ADM is a precursor for developing early pre-neoplastic lesions further progressing into PC due to oncogenic signaling. Hence delineating molecular events guiding tumor initiation may provide cues for regenerative medicine and precision onco-medicine. Therefore, understanding PC pathogenesis and early diagnosis are crucial. We hereby provide a timely overview of the current progress in this direction and future perspectives we foresee unfolding in the best interest of patient well-being and better clinical management of PC.

ADAM17, A Key Player of Cardiac Inflammation and Fibrosis in Heart Failure Development During Chronic Catecholamine Stress

Heart failure development is characterized by persistent inflammation and progressive fibrosis owing to chronic catecholamine stress. In a chronic stress state, elevated catecholamines result in the overstimulation of beta-adrenergic receptors (βARs), specifically β2-AR coupling with Gαi protein. Gαi signaling increases the activation of receptor-stimulated p38 mitogen-activated-protein-kinases (p38 MAPKs) and extracellular signal-regulated kinases (ERKs). Phosphorylation by these kinases is a common way to positively regulate the catalytic activity of A Disintegrin and Metalloprotease 17 (ADAM17), a metalloprotease that has grown much attention in recent years and has emerged as a chief regulatory hub in inflammation, fibrosis, and immunity due to its vital proteolytic activity. ADAM17 cleaves and activates proinflammatory cytokines and fibrotic factors that enhance cardiac dysfunction via inflammation and fibrosis. However, there is limited information on the cardiovascular aspect of ADAM17, especially in heart failure. Hence, this concise review provides a comprehensive insight into the structure of ADAM17, how it is activated and regulated during chronic catecholamine stress in heart failure development. This review highlights the inflammatory and fibrotic roles of ADAM17’s substrates; Tumor Necrosis Factor α (TNFα), soluble interleukin-6 receptor (sIL-6R), and amphiregulin (AREG). Finally, how ADAM17-induced chronic inflammation and progressive fibrosis aggravate cardiac dysfunction is discussed.

Epithelial memory of inflammation limits tissue damage while promoting pancreatic tumorigenesis

Inflammation is a major risk factor for pancreatic ductal adenocarcinoma (PDAC). When occurring in the context of pancreatitis, KRAS mutations accelerate tumor development in mouse models. We report that long after its complete resolution, a transient inflammatory event primes pancreatic epithelial cells to subsequent transformation by oncogenic KRAS. Upon recovery from acute inflammation, pancreatic epithelial cells display an enduring adaptive response associated with sustained transcriptional and epigenetic reprogramming. Such adaptation enables the reactivation of acinar-to-ductal metaplasia (ADM) upon subsequent inflammatory events, thereby limiting tissue damage through a rapid decrease of zymogen production. We propose that because activating mutations of KRAS maintain an irreversible ADM, they may be beneficial and under strong positive selection in the context of recurrent pancreatitis.

Development of thymic tumor in [LSL:KrasG12D; Pdx1-CRE] mice, an adverse effect associated with accelerated pancreatic carcinogenesis

Pancreatic Ductal AdenoCarcinoma (PDAC) represents about 90% of pancreatic cancers. It is one of the most aggressive cancer, with a 5-year survival rate below 10% due to late diagnosis and poor therapeutic efficiency. This bad prognosis thus encourages intense research in order to better understand PDAC pathogenesis and molecular basis leading to the development of innovative therapeutic strategies. This research frequently involves the KC (LSL:KrasG12D;Pdx1-CRE) genetically engineered mouse model, which leads to pancreatic cancer predisposition. However, as frequently encountered in animal models, the KC mouse model also exhibits biases. Herein, we report a new adverse effect of KrasG12D mutation in KC mouse model. In our hands, 10% of KC mice developed clinical signs reaching pre-defined end-points between 100- and 150-days post-parturition, and associated with large thymic mass development. Histological and genetic analyses of this massive thymus enabled us (1) to characterize it as a highly proliferative thymic lymphoma and (2) to detect the unexpected recombination of the Lox-STOP-Lox cassette upstream KrasG12D allele and subsequent KRASG12D protein expression in all cells composing thymic masses. Finally, we highlighted that development of such thymic tumor was associated with accelerated pancreatic carcinogenesis, immune compartment disorganization, and in some cases, lung malignancies.

MicroRNA-374b inhibits breast cancer progression through regulating CCND1 and TGFA genes

Emerging evidence indicates that microRNAs (miRNAs) play a critical role in breast cancer development. We recently reported that a higher expression of miR-374b in tumor tissues was associated with a better disease-free survival of triple-negative breast cancer (TNBC). However, the functional significance and molecular mechanisms underlying the role of miR-374b in breast cancer are largely unknown. In this current study, we evaluated the biological functions and potential mechanisms of miR-374b in both TNBC and non-TNBC. We found that miR-374b was significantly downregulated in breast cancer tissues, compared to adjacent tissues. MiR-374b levels were also lower in breast cancer cell lines, as compared to breast epithelial cells. In vitro and in vivo studies demonstrated that miR-374b modulates the malignant behavior of breast cancer cells, such as cell proliferation in 2D and 3D, cell invasion ability, colony-forming ability and tumor growth in mice. By using bioinformatics tools, we predicted that miR-374b plays a role in breast cancer cells through negatively regulating cyclin D1 (CCND1) and transforming growth factor alpha (TGFA). We further confirmed that CCND1 and TGFA contribute to the malignant behavior of breast cancer cells in vitro and in vivo. Our rescue experiments showed that overexpressing CCND1 or TGFA reverses the phenotypes caused by miR-374b overexpression. Taken together, our studies suggest that miR-374b modulates malignant behavior of breast cancer cells by negatively regulating CCND1 and TGFA genes. The newly identified miR-374b-mediated CCND1 and TGFA gene silencing may facilitate a better understanding of the molecular mechanisms of breast cancer progression.

Circulating ADAMs are associated with renal and cardiovascular outcomes in chronic kidney disease patients

BACKGROUND

A disintegrin and metalloproteinase (ADAM) 17, also known as tumour necrosis factor α-converting enzyme (TACE), is a metalloproteinase that releases the ectodomains of most growth factors, cytokines, receptors and enzymes and has been associated with the presence of chronic kidney disease (CKD) and cardiovascular (CV) disease. The role of circulating ADAMs in the progression of renal function and CV events in CKD patients is unknown.

METHODS

A total of 2570 subjects from an observational and multicentre study with CKD Stages 3-5, CKD Stage 5D and controls without any history of CV disease were studied. Circulating ADAM activity was assessed using a fluorometric technique. Progression of renal disease was defined as a 30% increase in serum creatinine or dialysis requirement after 24 months of follow-up. CV outcomes were assessed after 48 months of follow-up.

RESULTS

Patients with advanced CKD had higher ADAM activity as compared with patients with moderate CKD or controls. Male patients with progression of CKD had higher ADAM levels at baseline compared with patients with stable renal function {22.19 relative fluorescence units/μL/h [95% confidence interval (CI) 11.22-37.32] versus 12.15 (7.02-21.50)}. After multivariate adjustment, higher ADAM activity was identified as a risk factor for progression of CKD in male patients [30% increase in the creatinine odds ratio (OR) 2.72 (95% CI 1.58-4.68), P < 0.001; dialysis requirement OR 3.00 (95% CI 1.65-5.46), P < 0.001; dialysis requirement or 30% increase in the creatinine OR 3.15 (95% CI 2.06-4.81), P < 0.001]. ADAM activity was also identified as an independent risk factor for CV events [hazard ratio (HR) 1.68 (95% CI 1.20-2.36), P = 0.003].

CONCLUSIONS

High ADAMs activity levels are independently associated with CKD progression in males and with CV events in CKD patients.

κB-Ras and Ral GTPases regulate acinar to ductal metaplasia during pancreatic adenocarcinoma development and pancreatitis

Pancreatic ductal adenocarcinoma (PDAC) is associated with high mortality and therapy resistance. Here, we show that low expression of κB-Ras GTPases is frequently detected in PDAC and correlates with higher histologic grade. In a model of KRas^G12D-driven PDAC, loss of κB-Ras accelerates tumour development and shortens median survival. κB-Ras deficiency promotes acinar-to-ductal metaplasia (ADM) during tumour initiation as well as tumour progression through intrinsic effects on proliferation and invasion. κB-Ras proteins are also required for acinar regeneration after pancreatitis, demonstrating a general role in control of plasticity. Molecularly, upregulation of Ral GTPase activity and Sox9 expression underlies the observed phenotypes, identifying a previously unrecognized function of Ral signalling in ADM. Our results provide evidence for a tumour suppressive role of κB-Ras proteins and highlight low κB-Ras levels and consequent loss of Ral control as risk factors, thus emphasizing the necessity for therapeutic options that allow interference with Ral-driven signalling.

The molecular mechanisms of acinar-to-ductal metaplasia (ADM) in the course of pancreatitis and cancer development are unclear. Here, the authors show that loss of κB-Ras and consequent Ral activation promotes tumour initiation and progression through persistent ADM and enhanced cell proliferation

Excess Transforming Growth Factor-α Changed the Cell Properties of Corneal Epithelium and Stroma

Purpose

This study is to investigate the corneal anomaly caused by excess transforming growth factor-α (TGF-α) during mouse development.

Methods

Bitransgenic KeraRT/TGF-α mice, generated via cross-mating tetO-TGF-α and KeraRT mice, were induced to overexpress TGF-α by doxycycline commencing at embryonic day 0 or postnatal day 0 to different developmental stages. Bitransgenic mice with doxycycline induction were defined as TGF-αECK mice (TGF-α excess expression by corneal keratocytes). Mouse eyes were examined by hematoxylin and eosin staining, immunofluorescent staining and transmission electron microscopy. Protein and RNA from mouse cornea were subjected to western blotting and real-time quantitative polymerase chain reaction.

Results

In TGF-αECK mice, TGF-α overexpression resulted in corneal opacity. Excess TGF-α initially caused corneal epithelial hyperplasia and subsequent epithelium degeneration as the mouse developed, which was accompanied by gradually diminished K12 expression from the periphery of corneal epithelium and increased K13 expression toward the corneal center. Interestingly, K14 was detected in all layers of corneal epithelium of TGF-αECK mice, whereas it was limited at basal layer of controls. Transmission electron microscopy showed desmosome loss between corneal epithelial cells of TGF-αECK mice. In TGF-αECK mice, keratocan expression was abolished; α-SMA expression was increased while expression of Col1a1, Col1a2, and Col5a1 was diminished. Cell proliferation increased in the corneal epithelium and stroma, but not in the endothelium of TGF-αECK mice.

Conclusions

Excess TGF-α had detrimental effects on corneal morphogenesis during mouse development in that it changed the cell fate of corneal epithelial cells to assume conjunctival phenotypic expression of K13, and keratocytes to myofibroblast phenotype.

The glycan CA19-9 promotes pancreatitis and pancreatic cancer in mice

Glycosylation alterations are indicative of tissue inflammation and neoplasia, but whether these alterations contribute to disease pathogenesis is largely unknown. To study the role of glycan changes in pancreatic disease, we inducibly expressed human fucosyltransferase 3 and β1,3-galactosyltransferase 5 in mice, reconstituting the glycan sialyl-Lewis^a, also known as carbohydrate antigen 19-9 (CA19-9). Notably, CA19-9 expression in mice resulted in rapid and severe pancreatitis with hyperactivation of epidermal growth factor receptor (EGFR) signaling. Mechanistically, CA19-9 modification of the matricellular protein fibulin-3 increased its interaction with EGFR, and blockade of fibulin-3, EGFR ligands, or CA19-9 prevented EGFR hyperactivation in organoids. CA19-9-mediated pancreatitis was reversible and could be suppressed with CA19-9 antibodies. CA19-9 also cooperated with the Kras^G12D oncogene to produce aggressive pancreatic cancer. These findings implicate CA19-9 in the etiology of pancreatitis and pancreatic cancer and nominate CA19-9 as a therapeutic target.

PRDM3 attenuates pancreatitis and pancreatic tumorigenesis by regulating inflammatory response

Pancreatic ductal adenocarcinoma (PDAC) is associated with metaplastic changes in the pancreas but the transcriptional program underlying these changes is incompletely understood. The zinc finger transcription factor, PRDM3, is lowly expressed in normal pancreatic acini and its expression increases during tumorigenesis. Although PRDM3 promotes proliferation and migration of PDAC cell lines, the role of PRDM3 during tumor initiation from pancreatic acinar cells in vivo is unclear. In this study, we showed that high levels of PRDM3 expression in human pancreas was associated with pancreatitis, and well-differentiated but not poorly differentiated carcinoma. We examined PRDM3 function in pancreatic acinar cells during tumor formation and pancreatitis by inactivating Prdm3 using a conditional allele (Ptf1aCreER;Prdm3flox/flox mice) in the context of oncogenic Kras expression and supraphysiological cerulein injections, respectively. In Prdm3-deficient mice, KrasG12D-driven preneoplastic lesions were more abundant and progressed to high-grade precancerous lesions more rapidly. This is consistent with our observations that low levels of PRDM3 in human PDAC was correlated significantly with poorer survival in patient. Moreover, loss of Prdm3 in acinar cells elevated exocrine injury, enhanced immune cell activation and infiltration, and greatly increased acinar-to-ductal cell reprogramming upon cerulein-induced pancreatitis. Whole transcriptome analyses of Prdm3 knockout acini revealed that pathways involved in inflammatory response and Hif-1 signaling were significantly upregulated in Prdm3-depleted acinar cells. Taken together, our results suggest that Prdm3 favors the maintenance of acinar cell homeostasis through modulation of their response to inflammation and oncogenic Kras activation, and thus plays a previously unexpected suppressive role during PDAC initiation.

Role of ADAM17 in kidney disease

It is known that the renin-angiotensin system plays a major role in the pathophysiology of cardiovascular disease and renal injury. Within the renin-angiotensin system, angiotensin-converting enzyme 2 (ACE2) cleaves ANG II to generate ANG(1–7) peptide, which counteracts the adverse effects of ANG II accumulation. ACE2 can undergo cleavage or shedding to release the catalytically active ectodomain into the circulation by a disintegrin and metalloprotease (ADAM)17, also known as TNF-α-converting enzyme. ADAM17 is involved in many pathological processes such as cancer, inflammatory diseases, neurological diseases, cardiovascular diseases, atherosclerosis, diabetes, and hypertension. Clinical and experimental studies have shown that ADAM17 is involved in chronic kidney disease (CKD) with a proinflammatory and profibrotic role, suggesting that it could be an important mediator of CKD progression. ADAM17 inhibition attenuates fibrosis and inflammation, suggesting that its inhibition may be a possible new valuable therapeutic tool in fibrotic kidney disease treatment. In addition, in renal disease, some experimental studies have demonstrated that ADAM17 is differently expressed in the kidney. Thus, ADAM17 is highly expressed in distal renal tubules and increased in the whole kidney in diabetic models. In this article, we will review the role of ADAM17 under physiological and pathological conditions. We will mainly focus on the importance of ADAM17 in the context of CKD.

Signaling Networks That Control Cellular Plasticity in Pancreatic Tumorigenesis, Progression, and Metastasis

Pancreatic ductal adenocarcinoma is one of the deadliest cancers, and its incidence on the rise. The major challenges in overcoming the poor prognosis with this disease include late detection and the aggressive biology of the disease. Intratumoral heterogeneity; presence of a robust, reactive, and desmoplastic stroma; and the crosstalk between the different tumor components require complete understanding of the pancreatic tumor biology to better understand the therapeutic challenges posed by this disease. In this review, we discuss the processes involved during tumorigenesis encompassing the inherent plasticity of the transformed cells, development of tumor stroma crosstalk, and enrichment of cancer stem cell population during tumorigenesis.

Functional roles of the human ribonuclease A superfamily in RNA metabolism and membrane receptor biology

The human ribonuclease A (hRNase A) superfamily is comprised of 13 members of secretory RNases, most of which are recognized as catabolic enzymes for their ribonucleolytic activity to degrade ribonucleic acids (RNAs) in the extracellular space, where they play a role in innate host defense and physiological homeostasis. Interestingly, human RNases 9-13, which belong to a non-canonical subgroup of the hRNase A superfamily, are ribonucleolytic activity-deficient proteins with unclear biological functions. Moreover, accumulating evidence indicates that secretory RNases, such as human RNase 5, can be internalized into cells facilitated by membrane receptors like the epidermal growth factor receptor to regulate intracellular RNA species, in particular non-coding RNAs, and signaling pathways by either a ribonucleolytic activity-dependent or -independent manner. In this review, we summarize the classical role of hRNase A superfamily in the metabolism of extracellular and intracellular RNAs and update its non-classical function as a cognate ligand of membrane receptors. We further discuss the biological significance and translational potential of using secretory RNases as predictive biomarkers or therapeutic agents in certain human diseases and the pathological settings for future investigations.

Cell of origin affects tumour development and phenotype in pancreatic ductal adenocarcinoma

OBJECTIVE

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive tumour thought to arise from ductal cells via pancreatic intraepithelial neoplasia (PanIN) precursor lesions. Modelling of different genetic events in mice suggests both ductal and acinar cells can give rise to PDAC. However, the impact of cellular context alone on tumour development and phenotype is unknown.

DESIGN

We examined the contribution of cellular origin to PDAC development by inducing PDAC-associated mutations, Kras^G12D expression and Trp53 loss, specifically in ductal cells (Sox9CreER;Kras^LSL-G12D;Trp53^flox/flox ('Duct:KP^cKO ')) or acinar cells (Ptf1a^CreER;Kras^LSL-G12D;Trp53^flox/flox ('Acinar:KP^cKO ')) in mice. We then performed a thorough analysis of the resulting histopathological changes.

RESULTS

Both mouse models developed PDAC, but Duct:KP^cKO mice developed PDAC earlier than Acinar:KP^cKO mice. Tumour development was more rapid and associated with high-grade murine PanIN (mPanIN) lesions in Duct:KP^cKO mice. In contrast, Acinar:KP^cKO mice exhibited widespread metaplasia and low-grade as well as high-grade mPanINs with delayed progression to PDAC. Acinar-cell-derived tumours also had a higher prevalence of mucinous glandular features reminiscent of early mPanIN lesions.

CONCLUSION

These findings indicate that ductal cells are primed to form carcinoma in situ that become invasive PDAC in the presence of oncogenic Kras and Trp53 deletion, while acinar cells with the same mutations appear to require a prolonged period of transition or reprogramming to initiate PDAC. Our findings illustrate that PDAC can develop in multiple ways and the cellular context in which mutations are acquired has significant impact on precursor lesion initiation, disease progression and tumour phenotype.

Cancer-associated acinar-to-ductal metaplasia within the invasive front of pancreatic cancer contributes to local invasion

The pancreas is an organ prone to inflammation, fibrosis, and atrophy because of an abundance of acinar cells that produce digestive enzymes. A characteristic of pancreatic cancer is the presence of desmoplasia, inflammatory cell infiltration, and cancer-associated acinar atrophy (CAA) within the invasive front. CAA is characterized by a high frequency of small ducts and resembles acinar-to-ductal metaplasia (ADM). However, the clinical significance of changes in acinar morphology, such as ADM with acinar atrophy, within the tumor microenvironment remains unclear. Here, we find that ADM within the invasive front of tumors is associated with cell invasion and desmoplasia in an orthotopic mouse model of pancreatic cancer. An analysis of resected human tumors revealed that regions of cancer-associated ADM were positive for TGFα, and that this TGFα expression was associated with primary tumor size and shorter survival times. Gene expression analysis identified distinct phenotypic profiles for cancer-associated ADM, sporadic ADM and chronic pancreatitis ADM. These findings suggest that the mechanisms driving ADM differ according to the specific tissue microenvironment and that cancer-associated ADM and acinar atrophy contribute to tumor cell invasion of the local pancreatic parenchyma.

A novel ligand-receptor relationship between families of ribonucleases and receptor tyrosine kinases

Pancreatic ribonuclease is known to participate in host defense system against pathogens, such as parasites, bacteria, and virus, which results in innate immune response. Nevertheless, its potential impact to host cells remains unclear. Of interest, several ribonucleases do not act as catalytically competent enzymes, suggesting that ribonucleases may be associated with certain intrinsic functions other than their ribonucleolytic activities. Most recently, human pancreatic ribonuclease 5 (hRNase5; also named angiogenin; hereinafter referred to as hRNase5/ANG), which belongs to the human ribonuclease A superfamily, has been demonstrated to function as a ligand of epidermal growth factor receptor (EGFR), a member of the receptor tyrosine kinase family. As a newly identified EGFR ligand, hRNase5/ANG associates with EGFR and stimulates EGFR and the downstream signaling in a catalytic-independent manner. Notably, hRNase5/ANG, whose level in sera of pancreatic cancer patients, serves as a non-invasive serum biomarker to stratify patients for predicting the sensitivity to EGFR-targeted therapy. Here, we describe the hRNase5/ANG-EGFR pair as an example to highlight a ligand-receptor relationship between families of ribonucleases and receptor tyrosine kinases, which are thought as two unrelated protein families associated with distinct biological functions. The notion of serum biomarker-guided EGFR-targeted therapies will also be discussed. Furthering our understanding of this novel ligand-receptor interaction will shed new light on the search of ligands for their cognate receptors, especially those orphan receptors without known ligands, and deepen our knowledge of the fundamental research in membrane receptor biology and the translational application toward the development of precision medicine.

Plasticity of differentiated cells in wound repair and tumorigenesis, part I: stomach and pancreas

For the last century or so, the mature, differentiated cells throughout the body have been regarded as largely inert with respect to their regenerative potential, yet recent research shows that they can become progenitor-like and re-enter the cell cycle. Indeed, we recently proposed that mature cells can become regenerative via a conserved set of molecular mechanisms ('paligenosis'), suggesting that a program for regeneration exists alongside programs for death (apoptosis) and division (mitosis). In two Reviews describing how emerging concepts of cellular plasticity are changing how the field views regeneration and tumorigenesis, we present the commonalities in the molecular and cellular features of plasticity at homeostasis and in response to injury in multiple organs. Here, in part 1, we discuss these advances in the stomach and pancreas. Understanding the extent of cell plasticity and uncovering its underlying mechanisms may help us refine important theories about the origin and progression of cancer, such as the cancer stem cell model, as well as the multi-hit model of tumorigenesis. Ultimately, we hope that the new concepts and perspectives on inherent cellular programs for regeneration and plasticity may open novel avenues for treating or preventing cancers.

An EGFR ligand promotes EGFR-mutant but not KRAS-mutant lung cancer in vivo

EGFR ligands (e.g., EGF and TGFA) have been shown to be clinically associated with poor survival in lung cancer. Since TGFA itself initiates autochthonous tumors in liver, breast, and pancreas but not in the lung in transgenic mice in vivo, it would appear that an EGFR ligand may not initiate but rather promote lung cancer. However, it has not been proven in vivo whether lung cancer is promoted by an EGFR ligand. Using transgenic mouse models conditionally expressing EGFR^L858R or Kras^G12D with TGFA (an EGFR ligand) in lung epithelium, we determined that TGFA promoted the growth of EGFR^L858R-lung tumors in airway regions but not that of Kras^G12D-lung tumors. Analysis of TCGA datasets identified ΔNp63 and AGR2 as potential key tumor-promoting regulators, which were highly induced in the TGFA-induced EGFR^L858R-lung tumors. The expression of AGR2 was positively correlated with the expression of TGFA in human EGFR-mutant lung adenocarcinomas. The expression of TGFA in human EGFR-mutant lung adenocarcinomas but not in the EGFR wild-type lung adenocarcinoma was associated with poor survival. These results suggest that targeting EGFR ligands may benefit patients who carry EGFR-mutant lung tumors but will not benefit patients with KRAS-mutant lung tumors.

Pancreatic DCLK1+ cells originate distinctly from PDX1+ progenitors and contribute to the initiation of intraductal papillary mucinous neoplasm in mice

PanINs and IPMNs are the two most common precursor lesions that can progress to invasive pancreatic ductal adenocarcinoma (PDA). DCLK1 has been identified as a biomarker of progenitor cells in PDA progressed from PanINs. To explore the potential role of DCLK1-expressing cells in the genesis of IPMNs, we compared the incidence of DCLK1-positive cells in pancreatic tissue samples from genetically-engineered mouse models (GEMMs) for IPMNs, PanINs, and acinar to ductal metaplasia by immunohistochemistry and immunofluorescence. Mouse lineage tracing experiments in the IPMN GEMM showed that DCLK1⁺ cells originated from a cell lineage distinct from PDX1⁺ progenitors. The DCLK1⁺ cells shared the features of tuft cells but were devoid of IPMN tumor biomarkers. The DCLK1⁺ cells were detected in the earliest proliferative acinar clusters prior to the formation of metaplastic ductal cells, and were enriched in the "IPMN niches". In summary, DCLK1 labels a unique pancreatic cellular lineage in the IPMN GEMM. The clustering of DCLK1⁺ cells is an early event in Kras-induced pancreatic tumorigenesis and may contribute to IPMN initiation.

Acinar cell plasticity and development of pancreatic ductal adenocarcinoma

Acinar cells in the adult pancreas show high plasticity and can undergo transdifferentiation to a progenitor-like cell type with ductal characteristics. This process, termed acinar-to-ductal metaplasia (ADM), is an important feature facilitating pancreas regeneration after injury. Data from animal models show that cells that undergo ADM in response to oncogenic signalling are precursors for pancreatic intraepithelial neoplasia lesions, which can further progress to pancreatic ductal adenocarcinoma (PDAC). As human pancreatic adenocarcinoma is often diagnosed at a stage of metastatic disease, understanding the processes that lead to its initiation is important for the discovery of markers for early detection, as well as options that enable an early intervention. Here, the critical determinants of acinar cell plasticity are discussed, in addition to the intracellular and extracellular signalling events that drive acinar cell metaplasia and their contribution to development of PDAC.

Smad2/3 Linker Phosphorylation Is a Possible Marker of Pancreatic Stem/Progenitor Cells in the Regenerative Phase of Acute Pancreatitis

OBJECTIVES

The aims of this study are to characterize cell proliferation and differentiation during regeneration after pancreatitis and pancreatic buds during development to evaluate the role of Smad2/3, phosphorylated at the specific linker threonine residues (pSmad2/3L-Thr) in positive cells.

METHODS

Male C57BL/6 mice received hourly intraperitoneal injections of cerulein and were analyzed after induced pancreatitis. Pancreatitis-affected tissue sections and pancreatic buds were immunostained for pSmad2/3L-Thr, with other markers thought to be stem/progenitor markers of the pancreas.

RESULTS

pSmad2/3L-Thr immunostaining-positive cells increased as the pancreatitis progressed. The expression of pSmad2/3L-Thr was seen in acinar cells and ductlike tubular complexes. These results suggest that pSmad2/3L-Thr is expressed during acinar-ductal metaplasia. Immunohistochemical colocalization of pSmad2/3L-Thr with Ki67 was never observed. pSmad2/3L-Thr-positive cells may remain in an undifferentiated state. During the pancreatic development process, pSmad2/3L-Thr was expressed as other markers. pSmad2/3L-Thr develops in duct structure of the undifferentiated cell population in the last part of viviparity that acinar structure is formed clearly.

CONCLUSIONS

pSmad2/3L-Thr expression occurs during acinar-ductal metaplasia after pancreatitis and may represent the contribution of stem cells and/or progenitor cells to the differentiation of the pancreas.

Chronic inflammation initiates multiple forms of K-Ras-independent mouse pancreatic cancer in the absence of TP53

Chronic inflammation (CI) is a risk factor for pancreatic cancer (PC) including the most common type, ductal adenocarcinoma (PDAC), but its role and the mechanisms involved are unclear. To investigate the role of CI in PC, we generated genetic mouse models with pancreatic specific CI in the presence or absence of TP53. Mice were engineered to express either cyclooxygenase-2 (COX-2) or IκB kinase-2 (IKK2), and TP53^+/+ or TP53^f/f specifically in adult pancreatic acinar cells by using a full-length pancreatic elastase promoter-driven Cre. Animals were followed for >80 weeks and pancreatic lesions were evaluated histologically and immunohistochemically. The presence of K-ras mutations was assessed by direct sequencing, locked nuclei acid (LNA)-based PCR, and immunohistochemistry. We observed that sustained COX-2/IKK2 expression caused histological abnormalities of pancreas, including increased immune cell infiltration, proliferation rate and DNA damage. A minority of animals with CI developed pre-neoplastic lesions, but cancer was not observed in any TP53^+/+ animals within 84 weeks. In contrast, all animals with CI-lacking TP53 developed various subtypes of PC, including acinar cell carcinoma, ductal adenocarcinoma, sarcomatoid carcinoma and neuroendocrine tumors, and all died within 65 weeks. No evidence of K-ras mutations was observed. Variations in the activity of the Hippo, pERK and c-Myc pathways were found in the diverse cancer subtypes. In summary, chronic inflammation is extremely inefficient at inducing PC in the presence of TP53. However, in the absence of TP53, CI leads to the development of several rare K-ras-independent forms of PC, with infrequent PDAC. This may help explain the rarity of PDAC in persons with chronic inflammatory conditions.

Mammary Epithelial Cells Treated Concurrently with TGF-α and TGF-β Exhibit Enhanced Proliferation and Death

Transforming growth factor-α (TGF-α) stimulates while TGF-β inhibits mammary epithelial cell growth, suggesting that when cells are treated concurrently with the growth factors their combined effects would result in no net growth. However, combined treatments stimulate proliferation and cellular transformation in several cell lines. The objective of this paper was to describe the effect of long-term (6 days) concurrent TGF-α and TGF-β treatment on normal mammary epithelial cell growth pattern, morphology, and gene expression. Growth curve analysis showed that TGF-α enhanced while TGF-β suppressed growth rate until Day 4, when cells entered lag phase. However, cells treated concurrently with both growth factors exhibited a dichotomous pattern of growth marked by growth and death phases (with no intermittent lag phase). These changes in growth patterns were due to a marked induction of cell death from Day 2 (16.5%) to Day 4 (89.5%), resulting in the transition from growth to death phases, even though the combined treated cultures had significantly more ( P < 0.05) cells in S phase on Day 4. TGF-β stimulated epithelial to mesenchyme transdifferentiation (EMT) in the presence of TGF-α, as characterized by increased expression of fibronectin and changes in TGF-β receptor binding. Expression patterns of genes that regulate the cell cycle showed significant interaction between treatment and days, with TGF-β overriding TGF-α–stimulated effects on gene expression. Overall, the combined treatments were marked by enhanced rates of cellular proliferation, death, and trans-differentiation, behaviors reminiscent of breast tumors, and thus this system may serve as a good model to study breast tumorigenesis.

A Disintegrin and Metalloprotease 17 in the Cardiovascular and Central Nervous Systems

ADAM17 is a metalloprotease and disintegrin that lodges in the plasmatic membrane of several cell types and is able to cleave a wide variety of cell surface proteins. It is somatically expressed in mammalian organisms and its proteolytic action influences several physiological and pathological processes. This review focuses on the structure of ADAM17, its signaling in the cardiovascular system and its participation in certain disorders involving the heart, blood vessels, and neural regulation of autonomic and cardiovascular modulation.

Mitogen-activated Protein Kinase Kinase Activity Maintains Acinar-to-Ductal Metaplasia and Is Required for Organ Regeneration in Pancreatitis

BACKGROUND & AIMS

Mitogen-activated protein kinase (MAPK) signaling in the exocrine pancreas has been extensively studied in the context of pancreatic cancer, where its potential as a therapeutic target is limited by acquired drug resistance. However, its role in pancreatitis is less understood. We investigated the role of mitogen-activated protein kinase kinase (MEK)-initiated MAPK signaling in pancreatitis to determine the potential for MEK inhibition in treating pancreatitis patients.

METHODS

To examine the role of MEK signaling in pancreatitis, we used both genetic and pharmacologic approaches to inhibit the MAPK signaling pathway in a murine model of cerulein-induced pancreatitis. We generated mice harboring inducible short hairpins targeting the MEK isoforms Map2k1 and/or Map2k2 specifically in the pancreatic epithelium. We also used the MEK inhibitor trametinib to determine the efficacy of systemic inhibition in mice with pancreatitis.

RESULTS

We demonstrated an essential role for MEK signaling in the initiation of pancreatitis. We showed that both systemic and parenchyma-specific MEK inhibition in established pancreatitis induces epithelial differentiation and stromal remodeling. However, systemic MEK inhibition also leads to a loss of the proliferative capacity of the pancreas, preventing the restoration of organ mass.

CONCLUSIONS

MEK activity is required for the initiation and maintenance of pancreatitis. MEK inhibition may be useful in the treatment of chronic pancreatitis to interrupt the vicious cycle of destruction and repair but at the expense of organ regeneration.

Understanding the Impact of ErbB Activating Events and Signal Transduction on Antigen Processing and Presentation: MHC Expression as a Model

Advances in molecular pathology have changed the landscape of oncology. The ability to interrogate tissue samples for oncogene amplification, driver mutations, and other molecular alterations provides clinicians with an enormous level of detail about their patient's cancer. In some cases, this information informs treatment decisions, especially those related to targeted anti-cancer therapies. However, in terms of immune-based therapies, it is less clear how to use such information. Likewise, despite studies demonstrating the pivotal role of neoantigens in predicting responsiveness to immune checkpoint blockade, it is not known if the expression of neoantigens impacts the response to targeted therapies despite a growing recognition of their diverse effects on immunity. To realize the promise of 'personalized medicine', it will be important to develop a more integrated understanding of the relationships between oncogenic events and processes governing anti-tumor immunity. One area of investigation to explore such relationships centers on defining how ErbB/HER activation and signal transduction influences antigen processing and presentation.

Chromosomal instability, tolerance of mitotic errors and multidrug resistance are promoted by tetraploidization in human cells

Up to 80% of human cancers, in particular solid tumors, contain cells with abnormal chromosomal numbers, or aneuploidy, which is often linked with marked chromosomal instability. Whereas in some tumors the aneuploidy occurs by missegregation of one or a few chromosomes, aneuploidy can also arise during proliferation of inherently unstable tetraploid cells generated by whole genome doubling from diploid cells. Recent findings from cancer genome sequencing projects suggest that nearly 40% of tumors underwent whole genome doubling at some point of tumorigenesis, yet its contribution to cancer phenotypes and benefits for malignant growth remain unclear. Here, we investigated the consequences of a whole genome doubling in both cancerous and non-transformed p53 positive human cells. SNP array analysis and multicolor karyotyping revealed that induced whole-genome doubling led to variable aneuploidy. We found that chromosomal instability (CIN) is a frequent, but not a default outcome of whole genome doubling. The CIN phenotypes were accompanied by increased tolerance to mitotic errors that was mediated by suppression of the p53 signaling. Additionally, the expression of pro-apoptotic factors, such as iASPP and cIAP2, was downregulated. Furthermore, we found that whole genome doubling promotes resistance to a broad spectrum of chemotherapeutic drugs and stimulates anchorage-independent growth even in non-transformed p53-positive human cells. Taken together, whole genome doubling provides multifaceted benefits for malignant growth. Our findings provide new insight why genome-doubling promotes tumorigenesis and correlates with poor survival in cancer.

Regulation of Cellular Identity in Cancer

Neoplastic transformation requires changes in cellular identity. Emerging evidence increasingly points to cellular reprogramming, a process during which fully differentiated and functional cells lose aspects of their identity while gaining progenitor characteristics, as a critical early step during cancer initiation. This cell identity crisis persists even at the malignant stage in certain cancers, suggesting that reactivation of progenitor functions supports tumorigenicity. Here, we review recent findings that establish the essential role of cellular reprogramming during neoplastic transformation and the major players involved in it with a special emphasis on pancreatic cancer.

Regulation of Cellular Identity in Cancer

Neoplastic transformation requires changes in cellular identity. Emerging evidence increasingly points to cellular reprogramming, a process during which fully differentiated and functional cells lose aspects of their identity while gaining progenitor characteristics, as a critical early step during cancer initiation. This cell identity crisis persists even at the malignant stage in certain cancers, suggesting that reactivation of progenitor functions supports tumorigenicity. Here, we review recent findings that establish the essential role of cellular reprogramming during neoplastic transformation and the major players involved in it with a special emphasis on pancreatic cancer.

EGFR Signaling in Liver Diseases

The epidermal growth factor receptor (EGFR) is a transmembrane receptor tyrosine kinase that is activated by several ligands leading to the activation of diverse signaling pathways controlling mainly proliferation, differentiation, and survival. The EGFR signaling axis has been shown to play a key role during liver regeneration following acute and chronic liver damage, as well as in cirrhosis and hepatocellular carcinoma (HCC) highlighting the importance of the EGFR in the development of liver diseases. Despite the frequent overexpression of EGFR in human HCC, clinical studies with EGFR inhibitors have so far shown only modest results. Interestingly, a recent study has shown that in human HCC and in mouse HCC models the EGFR is upregulated in liver macrophages where it plays a tumor-promoting function. Thus, the role of EGFR in liver diseases appears to be more complex than what anticipated. Further studies are needed to improve the molecular understanding of the cell-specific signaling pathways that control disease development and progression to be able to develop better therapies targeting major components of the EGFR signaling network in selected cell types. In this review, we compiled the current knowledge of EGFR signaling in different models of liver damage and diseases, mainly derived from the analysis of HCC cell lines and genetically engineered mouse models (GEMMs).

Ménétrier's Disease: Its Mimickers and Pathogenesis

Ménétrier’s disease is a rare protein-losing hypertrophic gastropathy. Histologically, it can be mistaken for other disorders showing hypertrophic gastropathy. The pathogenesis of Ménétrier’s disease is not fully understood; however, it appears that the epidermal growth factor receptor (EGFR) ligand, transforming growth factor alpha, contributes to the pathogenesis of this disorder. In this review, we will discuss disease entities that can mimic Ménétrier’s disease and the role of EGFR signaling in Ménétrier’s disease.

Rhomboid domain containing 1 promotes colorectal cancer growth through activation of the EGFR signalling pathway

Rhomboid proteins perform a wide range of important functions in a variety of organisms. Recent studies have revealed that rhomboid proteins are involved in human cancer progression; however, the underlying molecular mechanism remains largely unclear. Here we show that RHBDD1, a rhomboid intramembrane serine protease, is highly expressed and closely associated with survival in patients with colorectal cancer. We observe that inactivation of RHBDD1 decreases tumor cell growth. Further studies show that RHBDD1 interacts with proTGFα and induces the ADAM-independent cleavage and secretion of proTGFα. The secreted TGFα further triggers the activation of the EGFR/Raf/MEK/ERK signalling pathway. Finally, the positive correlation of RHBDD1 expression with the EGFR/Raf/MEK/ERK signalling pathway is further corroborated in a murine model of colitis-associated colorectal cancer. These findings provide evidence of a growth-promoting role for RHBDD1 in colorectal cancer and may aid the development of tumor biomarkers or antitumor therapeutics.

Transgenic expression of the human growth hormone minigene promotes pancreatic β-cell proliferation

Transgenic mouse models are designed to study the role of specific proteins. To increase transgene expression the human growth hormone (hGH) minigene, including introns, has been included in many transgenic constructs. Until recently, it was thought that the hGH gene was not spliced, transcribed, and translated to produce functional hGH protein. We generated a transgenic mouse with the transcription factor Forkhead box M1 (FoxM1) followed by the hGH minigene, under control of the mouse insulin promoter (MIP) to target expression specifically in the pancreatic β-cell. Expression of FoxM1 in isolated pancreatic islets in vitro stimulates β-cell proliferation. We aimed to investigate the effect of FoxM1 on β-cell mass in a mouse model for diabetes mellitus. However, we found inadvertent coexpression of hGH protein from a spliced, bicistronic mRNA. MIP-FoxM1-hGH mice had lower blood glucose and higher pancreatic insulin content, due to increased β-cell proliferation. hGH signals through the murine prolactin receptor, and expression of its downstream targets tryptophan hydroxylase-1 (Tph1), tryptophan hydroxylase-2 (Tph2), and cytokine-inducible SH2 containing protein (Cish) was increased. Conversely, transcriptional targets of FoxM1 were not upregulated. Our data suggest that the phenotype of MIP-FoxM1-hGH mice is due primarily to hGH activity and that the FoxM1 protein remains largely inactive. Over the past decades, multiple transgenic mouse strains were generated that make use of the hGH minigene to increase transgene expression. Our work suggests that each will need to be carefully screened for inadvertent hGH production and critically evaluated for the use of proper controls.

Reserve stem cells: Differentiated cells reprogram to fuel repair, metaplasia, and neoplasia in the adult gastrointestinal tract

It has long been known that differentiated cells can switch fates, especially in vitro, but only recently has there been a critical mass of publications describing the mechanisms adult, postmitotic cells use in vivo to reverse their differentiation state. We propose that this sort of cellular reprogramming is a fundamental cellular process akin to apoptosis or mitosis. Because reprogramming can invoke regenerative cells from mature cells, it is critical to the long-term maintenance of tissues like the pancreas, which encounter large insults during adulthood but lack constitutively active adult stem cells to repair the damage. However, even in tissues with adult stem cells, like the stomach and intestine, reprogramming may allow mature cells to serve as reserve ("quiescent") stem cells when normal stem cells are compromised. We propose that the potential downside to reprogramming is that it increases risk for cancers that occur late in adulthood. Mature, long-lived cells may have years of exposure to mutagens. Mutations that affect the physiological function of differentiated, postmitotic cells may lead to apoptosis, but mutations in genes that govern proliferation might not be selected against. Hence, reprogramming with reentry into the cell cycle might unmask those mutations, causing an irreversible progenitor-like, proliferative state. We review recent evidence showing that reprogramming fuels irreversible metaplastic and precancerous proliferation in the stomach and pancreas. Finally, we illustrate how we think reprogrammed differentiated cells are likely candidates as cells of origin for cancers of the intestine.

Single and Multiple Gene Manipulations in Mouse Models of Human Cancer

Mouse models of human cancer play a critical role in understanding the molecular and cellular mechanisms of tumorigenesis. Advances continue to be made in modeling human disease in a mouse, though the relevance of a mouse model often relies on how closely it is able to mimic the histologic, molecular, and physiologic characteristics of the respective human cancer. A classic use of a genetically engineered mouse in studying cancer is through the overexpression or deletion of a gene. However, the manipulation of a single gene often falls short of mimicking all the characteristics of the carcinoma in humans; thus a multiple gene approach is needed. Here we review genetic mouse models of cancers and their abilities to recapitulate human carcinoma with single versus combinatorial approaches with genes commonly involved in cancer.

What are the macrophages and stellate cells doing in pancreatic adenocarcinoma?

Pancreatic ductal adenocarcinoma is a devastating disease characterized by a dense desmoplastic stroma. Chemo- and radio-therapeutic strategies based on targeting cancer cells have failed in improving the outcome of this cancer suggesting important roles for stroma in therapy resistance. Cells in the tumor stroma have been shown to regulate proliferation, resistance to apoptosis and treatments, epithelial to mesenchymal transition (EMT) and stemness of cancer cells. Stellate cells in their activated state have been thought over the past decade to only have tumor promoting roles. However, recent findings suggest that stellate cells may have protective roles as well. The present review highlights the latest findings on the role of two major components of tumor stroma, pancreatic stellate cells and macrophages, in promoting or inhibiting pancreatic cancer, focused on their effects on EMT and cancer stemness.

Smad4 loss synergizes with TGFα overexpression in promoting pancreatic metaplasia, PanIN development, and fibrosis

AIMS

While overexpression of TGFα has been reported in human pancreatic ductal adenocarcinoma (PDAC), mice with overexpressed TGFα develop premalignant pancreatic acinar-to-ductal metaplasia (ADM) but not PDAC. TGF-β signaling pathway is pivotal to the development of PDAC and tissue fibrosis. Here we sought to investigate the interplay between TGFα and TGF-β signaling in pancreatic tumorigenesis and fibrosis, namely via Smad4 inactivation.

METHODS

The MT-TGFα mouse was crossed with a new Smad4 conditional knock-out mouse (Smad4flox/flox;p48-Cre or S4) to generate Smad4flox/flox;MT-TGFα;p48-Cre (STP). After TGFα overexpression was induced with zinc sulfate water for eight months, the pancreata of the STP, MT-TGFα, and S4 mice were examined for tumor development and fibrotic responses. PanIN lesions and number of ducts were counted, and proliferation was measured by Ki67 immunohistochemistry (IHC). Qualitative analysis of fibrosis was analyzed by Trichrome Masson and Sirius Red staining, while vimentin was used for quantification. Expression analyses of fibrosis, pancreatitis, or desmoplasia associated markers (α-SMA, Shh, COX-2, Muc6, Col1a1, and Ctgf) were performed by IHC and/or qRT-PCR.

RESULTS

Our STP mice exhibited advanced ADM, increased fibrosis, increased numbers of PanIN lesions, overexpression of chronic pancreatitis-related marker Muc6, and elevated expression of desmoplasia-associated marker Col1A1, compared to the MT-TGFα mice. The inactivation of Smad4 in the exocrine compartment was responsible for both the enhanced PanIN formation and fibrosis in the pancreas. The phenotype of the STP mice represents a transient state from ADMs to PanINs, closely mimicking the interface area seen in human chronic pancreatitis associated with PDAC.

CONCLUSION

We have documented a novel mouse model, the STP mice, which displayed histologic presentations reminiscent to those of human chronic pancreatitis with signs of early tumorigenesis. The STP mice could be a suitable animal model for interrogating the transition of chronic pancreatitis to pancreatic cancer.

Protein kinase D1 drives pancreatic acinar cell reprogramming and progression to intraepithelial neoplasia

The transdifferentiation of pancreatic acinar cells to a ductal phenotype (acinar-to-ductal metaplasia, ADM) occurs after injury or inflammation of the pancreas and is a reversible process. However, in the presence of activating Kras mutations or persistent epidermal growth factor receptor (EGF-R) signalling, cells that underwent ADM can progress to pancreatic intraepithelial neoplasia (PanIN) and eventually pancreatic cancer. In transgenic animal models, ADM and PanINs are initiated by high-affinity ligands for EGF-R or activating Kras mutations, but the underlying signalling mechanisms are not well understood. Here, using a conditional knockout approach, we show that protein kinase D1 (PKD1) is sufficient to drive the reprogramming process to a ductal phenotype and progression to PanINs. Moreover, using 3D explant culture of primary pancreatic acinar cells, we show that PKD1 acts downstream of TGFα and Kras, to mediate formation of ductal structures through activation of the Notch pathway.