Hepatic stellate cells regulate liver immunity to visceral leishmaniasis through P110δ-dependent induction and expansion of regulatory T cells in mice

Visceral leishmaniasis (VL) is associated with severe immune dysfunction and if untreated leads to death. Because the liver is one of the primary target organs in VL, unraveling the mechanisms governing the local hepatic immune response is important for understanding the immunopathogenesis of VL. We previously reported that mice with inactivating knockin mutation in the p110δ gene (p110δ(D910A) ) are resistant to VL, due in part to impaired regulatory T-cell (Treg) expansion. In this study, we investigated the mechanism of this resistance by focusing on hepatic stellate cells (HSCs), which are known to regulate Treg induction and expansion. We show that HSCs are infected with Leishmania donovani in vivo and in vitro and that this infection leads to the production of interleukin-2, interleukin-6, and transforming growth factor-β, cytokines known to induce Tregs. We further demonstrate that L. donovani infection leads to expansion of HSCs in a p110δ-dependent manner and that this correlated with proliferation of hepatic Tregs in vivo. In vitro studies clearly show that L. donovani-infected HSCs induce CD4(+) T cells to become Tregs and expand Tregs in a p110δ-dependent manner. Targeted depletion of HSCs during infection caused a dramatic reduction in liver Treg numbers and proliferation, which was associated with a decrease in interleukin-10 production by hepatic T cells and a more efficient parasite control.

CONCLUSION

These results demonstrate the critical role of HSCs in the pathogenesis of VL and suggest that the enhanced resistance of p110δ(D910A) mice to L. donovani infection is due in part to impaired expansion and inability of their HSCs to induce and expand Tregs in the liver.

Pancreatic progenitor-derived hepatocytes are viable and functional in a 3D high density bioreactor culture system

The rat pancreatic progenitor cell line B-13 is of interest for research on drug metabolism and toxicity since the cells trans-differentiate into functional hepatocyte-like cells (B-13/H) when treated with glucocorticoids. In this study we investigated the trans-differentiation and liver-specific functions of B-13/H cells in a three-dimensional (3D) multi-compartment bioreactor, which has already been successfully used for primary liver cell culture. Undifferentiated B-13 cells were inoculated into the bioreactor system and exposed to dexamethasone to promote hepatic trans-differentiation (B-13/HT). In a second approach, pre-differentiated B-13 cells were cultured in bioreactors for 15 days to evaluate the maintenance of liver-typical functions (B-13/HP). During trans-differentiation of B-13 cells into hepatocyte-like cells in the 3D bioreactor system (approach B-13/HT), an increase in glucose metabolism and in liver-specific functions (urea and albumin synthesis; cytochrome P450 [CYP] enzyme activity) was observed, whereas amylase - characteristic for exocrine pancreas and undifferentiated B-13 cells - decreased over time. In bioreactors with pre-differentiated cells (approach B-13/HP), the above liver-specific functions were maintained over the whole culture period. Results were confirmed by gene expression and protein analysis showing increased expression of carbamoyl-phosphate synthase 1 (CPS-1), albumin, CYP2E1, CYP2C11 and CYP3A1 with simultaneous loss of amylase. Immunohistochemical studies showed the formation of 3D structures with expression of liver-specific markers, including albumin, cytokeratin (CK) 18, CCAAT/enhancer-binding protein beta (CEBP-β), CYP2E1 and multidrug resistance protein 2 (MRP2). In conclusion, successful culture and trans-differentiation of B-13 cells in the 3D bioreactor was demonstrated. The requirement for only one hormone and simple culture conditions to generate liver-like cells makes this cell type useful for in vitro research using 3D high-density culture systems.

Progenitor-derived hepatocyte-like (B-13/H) cells metabolise 1'-hydroxyestragole to a genotoxic species via a SULT2B1-dependent mechanism

Rat B-13 progenitor cells are readily converted into functional hepatocyte-like B-13/H cells capable of phase I cytochrome P450-dependent activation of pro-carcinogens and induction of DNA damage. The aim of the present study was to investigate whether the cells are also capable of Phase II sulphotransferase (SULT)-dependent activation of a pro-carcinogen to an ultimate carcinogen. To this end we therefore examined the bioactivation of the model hepatic (hepato- and cholangio-) carcinogen estragole and its proximate SULT1A1-activated genotoxic metabolite 1'-hydroxyestragole. Exposing B-13 or B-13/H cells to estragole (at concentrations up to 1mM) resulted in the production of low levels of 1'-hydroxyestragole, but did not result in detectable DNA damage. Exposing B-13/H cells - but not B-13 cells - to 1'-hydroxyestragole resulted in a dose-dependent increase in DNA damage in comet assays, confirmed by detection of N(2)-(trans-isoestragol-3'-yl)-2'-deoxyguanosine adducts. Genotoxicity was inhibited by general SULT inhibitors, supporting a role for SULTS in the activation of 1-hydroxyestragole in B-13/H cells. However, B-13 and B-13/H cells did not express biologically significant levels of SULT1A1 as determined by qRT-PCR, Western blotting and its associated 7-hydroxycoumarin sulphation activity. B-13 and B-13/H cells expressed - relative to intact rat liver - high levels of SULT2B1 (primarily the b isoform) and SULT4A1 mRNAs and proteins. B-13 and B-13/H cells also expressed the 3'-phosphoadenosine 5'-phosphosulphate synthase 1 required for the generation of activated sulphate cofactor 3'-phosphoadenosine 5'-phosphosulphate. However, only B-13/H cells expressed functional SULT activities towards SULT2B1 substrates DHEA, pregnenolone and 4 methylumbelliferone. Since liver progenitor cells are bi-potential and also form cholangiocytes, we therefore hypothesised that B-13 cells express a cholangiocyte-like SULT profile. To test this hypothesis, the expression of SULTs was examined in liver by RT-PCR and immunohistochemistry. SULT2B1 - but not SULT1A1 - was determined to be expressed in both rat and human cholangiocytes. Since 1'-hydroxyestragole exposure readily produced DNA injury in B-13/H cells, these data suggest that cholangiocarcinomas generated in rats fed estragole may be dependent, in part, on SULT2B1 activation of the 1'-hydroxyestragole metabolite.

Sustained Isoprostane E2 Elevation, Inflammation and Fibrosis after Acute Ischaemia-Reperfusion Injury Are Reduced by Pregnane X Receptor Activation

Liver grafts donated after cardiac death are increasingly used to expand the donor pool but are prone to ischaemic-type biliary lesions. The anti-inflammatory effects of the activated pregnane X receptor have previously been shown to be beneficial in a number of inflammatory liver conditions. However, its role in reducing peri-portal inflammation and fibrosis following ischaemia-reperfusion injury has not been investigated. Hepatic injury and its response to pregnane X receptor activation was examined after partial hepatic ischaemia-reperfusion injury induced by surgically clamping the left and middle lobar blood vessels in rats. Molecular and pathological changes in the liver were examined over the following 28 days. Ischaemia-reperfusion injury resulted in transient cholestasis associated with microvillar changes in biliary epithelial cell membranes and hepatocellular injury which resolved within days after reperfusion. However, in contrast to chemically-induced acute liver injuries, this was followed by sustained elevation in isoprostane E2, peri-portal inflammation and fibrosis that remained unresolved in the ischaemic reperfused lobe for at least 28 days after clamping. Administration of pregnenolone-16α-carbonitrile—a rodent-specific pregnane X receptor activator—resulted in significant reductions in cholestasis, hepatic injury, ischaemic lobe isoprostane E2 levels, peri-portal inflammation and fibrosis. Hepatic ischaemia-reperfusion injury therefore results in inflammatory and fibrotic changes that persist well beyond the initial ischaemic insult. Drug-mediated activation of the pregnane X receptor reduced these adverse changes in rats, suggesting that the pregnane X receptor is a viable drug target to reduce ischaemic-type biliary lesions in recipients of liver transplants donated after cardiac death.

An expandable donor-free supply of functional hepatocytes for toxicology

The B-13 cell is a readily expandable rat pancreatic acinar-like cell that differentiates on simple plastic culture substrata into replicatively-senescent hepatocyte-like (B-13/H) cells in response to glucocorticoid exposure. B-13/H cells express a variety of liver-enriched and liver-specific genes, many at levels similar to hepatocytes in vivo. Furthermore, the B-13/H phenotype is maintained for at least several weeks in vitro, in contrast to normal hepatocytes which rapidly de-differentiate under the same simple – or even under more complex – culture conditions. The origin of the B-13 cell line and the current state of knowledge regarding differentiation to B-13/H cells are presented, followed by a review of recent advances in the use of B-13/H cells in a variety of toxicity endpoints. B-13 cells therefore offer Toxicologists a cost-effective and easy to use system to study a range of toxicologically-related questions. Dissecting the mechanism(s) regulating the formation of B-13/H cell may also increase the likelihood of engineering a human equivalent, providing Toxicologists with an expandable donor-free supply of functional rat and human hepatocytes, invaluable additions to the tool kit of in vitro toxicity tests.

Stealth Amphotericin B nanoparticles for oral drug delivery: In vitro optimization

Purpose

Amphotericin B (AmB) is an effective anti-fungal and anti-leishmanial agent. However, AmB has low oral bioavailability (0.3%) and adverse effects (e.g., nephrotoxicity). The objectives of this study were to improve the oral bioavailability by entrapping AmB in pegylated (PEG) poly lactide co glycolide copolymer (PLGA–PEG) nanoparticles (NPs). The feasibility of different surfactants and stabilizers on the mean particle size (MPS) and entrapment efficiency were also investigated.

Materials and methods

NPs of AmB were prepared by a modified emulsification diffusion method employing a vitamin E derivative as a stabilizer. Physicochemical properties and particle size characterization were evaluated using Fourier Transform Infra-Red spectroscopy (FTIR), differential scanning calorimetry, scanning electron microscopy and transmission electron microscopy. Moreover, in vitro dissolution profiles were performed for all formulated AmB NPs.

Results

MPS of the prepared spherical particles of AmB ranged from 26.4 ± 2.9 to 1068 ± 489.8 nm. An increased stirring rate favored AmB NPs with a smaller MPS. There was a significant reduction in MPS, drug content and drug release, when AmB NPs were prepared using the diblock polymer PLGA–PEG with 15% PEG. Addition of three emulsifying agents poly vinyl pyrrolidone (PVP), Vitamin E (TPGS) and pluronic F-68 to AmB formulations led to a significant reduction in particle size and increase in drug entrapment efficiency (DEE) compared to addition of PVP alone. FTIR spectroscopy demonstrated a successful loading of AmB to pegylated PLGA–PEG copolymers. PLGA–PEG copolymer entrapment efficiency of AmB was increased up to 56.7%, with 92.7% drug yield. After a slow initial release, between 20% and 54% of AmB was released in vitro within 24 h phosphate buffer containing 2% sodium deoxycholate and were best fit Korsmeyer–Peppas model. In conclusion, PLGA–PEG diblock copolymer with 15% PEG produced a significant reduction (>70%) in MPS with highest drug content. The percentage of PEG in the copolymer and the surfactant/stabilizer used had a direct effect on AmB release in vitro, entrapment efficiency and MPS. These developed formulations are feasible, effective and improved alternatives to other carriers for oral delivery of AmB.

Quiescent hepatic stellate cells functionally contribute to the hepatic innate immune response via TLR3

Toll-like Receptor 3 (TLR3) is a pathogen pattern recognition receptor that plays a key role in innate immunity. TLR3 signalling has numerous functions in liver, both in health and disease. Here we report that TLR3 is expressed by quiescent hepatic stellate cells (HSC) where it functions to induce transcription and secretion of functional interferons as well as a number of other cytokines and chemokines. Upon transdifferentiation into myofibroblasts, HSCs rapidly loose the ability to produce interferon gamma (IFNγ). Mechanistically, this gene silencing may be due to Polycomb complex mediated repression via methylation of histone H3 lysine 27. In contrast to wild type, quiescent HSC isolated from tlr3 knockout mice do not produce IFNγ in response to Poly(I∶C) treatment. Therefore, quiescent HSC may contribute to induction of the hepatic innate immune system in response to injury or infection.

Utility of B-13 progenitor-derived hepatocytes in hepatotoxicity and genotoxicity studies

AR42J-B-13 (B-13) cells form hepatocyte-like (B-13/H) cells in response to glucocorticoid treatment. To establish its utility in toxicity and genotoxicity screening, cytochrome P450 (CYP) induction, susceptibility to toxins, and transporter gene expression were examined. Conversion to B-13/H cells resulted in expression of male-specific CYP2C11 and sensitivity to methapyrilene. B-13/H cells constitutively expressed CYP1A, induced expression in response to an aryl hydrocarbon receptor agonist, and activated benzo[α]pyrene to a DNA-damaging species. Functional CYP1A2 was not expressed due to deletions in the Cyp1a2 gene. A B-13 cell line stably expressing the human CYP1A2 was therefore engineered (B-13^−TR/h1A2) and the derived B-13/H cells expressed metabolically functional CYP1A2. Treatment with the cooked food mutagen 2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine resulted in a dose-dependent increase in DNA damage. B-13/H cells expressed constitutive androstane receptor (CAR) and induced CYP2B1 mRNA levels in response to classical CAR activators. However, translation to functional CYP2B1 protein was low and increased minimally by CAR activator treatment. B-13/H cells expressed high levels of pregnane X-receptor (PXR) and induced CYP3A1 in response to classical PXR activators. CYP3A genes were inducible, functional, and activated aflatoxin B1 to a DNA-damaging species. All 23 major hepatic transporters were induced when B-13 cells were converted to B-13/H cells, although in many cases, levels remained below those present in adult rat liver. However, bile salt export pump, Abcb1b, multidrug resistance-associated protein, and breast cancer resistance protein transporters were functional in B-13/H cells. These data demonstrate that the B-13 cell generates hepatocyte-like cells with functional drug metabolism and transporter activities, which can alone—or in a humanized form—be used to screen for hepatotoxic and genotoxic endpoints in vitro.

Abstract P6-10-04: The Presence of Anaplastic Lymphoma Kinase Recapitulates Formation of Breast Tumor Emboli with Encircling Lymphovasculogenesis

Background: Genetic abnormalities in the anaplastic lymphoma kinase (ALK) gene result in activation of signaling pathways including Akt, mTor, and JAK/Stat3. ALK has been shown to be a primary oncogenic driver in a variety of human tumors, including both hematologic malignancies such as anaplastic large cell lymphoma, as well as solid tumors including neuroblastoma, non-small cell lung cancer, myofibroblastic tumors and most recently, high grade serous ovarian carcinoma. While only ∼3% of all breast cancers have been reported to have ALK genetic abnormalities, our studies revealed that inflammatory breast cancer (IBC), the most lethal variant of breast cancer, is characterized by prevalent ALK gene amplification with activated ALK signaling. The present studies investigated the role of ALK in breast cancer by expressing full-length wild type ALK in MCF-7 cells.

Materials and Methods: Clones of MCF-7 breast cancer cells expressing wild type ALK or non-target vector were produced by lentivirus infection and selection of single cell clones. MCF-7 ALK clones were evaluated using live cell and phase contrast imaging, immunofluorescent staining with confocal imaging, gene profiling, phospho-protein array analysis, western blot and ELISA validation. In vivo studies were performed by injection of MCF-7 ALK clones into using NOD. Cg-Prkdcscid Il2rgtm1Wjl/SzJ mice using IACUC approved animal protocols.

Results: When cultured on plastic substrates, MCF-7 ALK clones formed tumor cell aggregates instead of monolayer cultures, and when cultured as tumor spheroids under non-adherent 3D conditions had a distinct cellular phenotype with significantly greater clonogenicity than either non-target vector MCF-7 clones or the parental cell line. Whole transcriptome analysis, with validation using protein arrays, western blots and ELISA analysis revealed that the presence of ALK up-regulated phospho-src. In vivo studies revealed that ALK expressing MCF-7 clones formed tumor emboli that were enwrapped by dermal lymphatic vessels, essentially recapitulating the phenotype of IBC tumor emboli that exhibit encircling lymphovasculogenesis. Enforced expression of wild type ALK in another breast cancer cell line resulted in similar formation of tumor emboli.

Discussion: These studies provide first time evidence for the association between full length ALK and formation of highly invasive tumor emboli enwrapped by lymphatic vessels, which is a primary characteristic of IBC. These studies, taken together with discovery of the prevalence of ALK gene amplification in IBC patients, indicate that ALK represents an important therapeutic target for IBC, with the availability of new ALK targeted therapies to evaluate as single agents and in combinations with other agents that may effectively target IBC tumor emboli that we have now linked to ALK and which represent the metastatic lesion of this lethal variant of breast cancer.

Funding by Susan G. Komen Organization Promise Grant KG081287 (FMR and MC).

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P6-10-04.

Abstract P4-06-03: Zinc Finger Nuclease Genome Engineering Reveal Multiple Functions of Secretory Leukocyte Peptidase Inhibitor in Regulating Pleuripotency of Cancer Stem Cells in Inflammatory Breast Cancer

Background: Inflammatory breast cancer (IBC) is the most aggressive and lethal variant of this disease and is known to be enriched for cells with a cancer stem cell phenotype. IBC is characterized by the presence of cell aggregates, defined as tumor emboli, that metastasize into skin and chest wall. The only documented biomarker of tumor emboli is the surface glycoprotein, E-cadherin. We previously demonstrated that IBC tumor emboli express the alarm anti-protease, secretory leukocyte peptidase inhibitor (SLPI), a metastasis related gene highly expressed in IBC patient tumors. Since the function of SLPI in IBC is unknown, the present studies used zinc finger technology to knockout (KO) copies of SLPI in the SUM149 IBC cell line to define the role of SLPI in IBC.

Materials and Methods: Using CompoZr zinc finger nuclease (ZFN) technology (Sigma-Aldrich), SLPI KO cell lines were generated by disrupting all alleles (3) in exon 1 of SUM149 cells derived from an IBC primary tumor with a high CD44+cell population. The target-specific ZFNs bound DNA at a sequence-specific location and created double strand breaks repaired by non-homologous end joining, resulting in deletions at the SLPI locus. Single cell SLPI KO clones were isolated and serially passaged to establish stable cell lines. Functional assays were used to assess proliferation, invasion, tube formation and clonogenicity. Global transcriptional profiling was performed to identify genes and signaling pathways directly regulated by SLPI.

Results: SUM149 SLPI KO clones did not produce SLPI protein and had a significantly slower turn-over time of 75 hrs compared with 24 hrs in SUM149 wild type clones. Loss of SLPI blocked invasion by 50%, and completely inhibited formation of tube-like structures, an activity defined as vasculogenic mimicry, characteristic of IBC. The loss of only 1 SLPI allele resulted in the inability of SUM149 cells to grow as anchorage independent clones in soft agar, commonly used as a predictor of in vivo tumorigenicity. SLPI directly regulated expression of multiple genes within the embryonic stem cell pleuripotency canonical pathway, including WNT, Frizzled, PDK-1, platelet derived growth factor receptor and sphingosine-1-phosphate receptor. Studies are underway to determine the specific role of SLPI in IBC tumor growth and metastasis.

Conclusions: Our previous studies demonstrated that SLPI is expressed by IBC tumor emboli and can be used as a biomarker of tumor emboli in IBC core and skin punch biopsies. SLPI was found to not only regulate critical functional activities of IBC tumor cells but also to directly regulate genes within pathways critically important to maintenance of pleuripotency of tumors with a cancer stem cell phenotype. Collectively, these studies demonstrate the power and utility of the zinc finger technology, which enables the interrogation of tumor cells to discern the direct function and role of specific genes of interest.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P4-06-03.

P2-05-04: Mapping the Specific Gene Families Activated in the Lymphangiogenesis and Vasculogenic Mimicry Exhibited by Inflammatory Breast Cancer

Background: Inflammatory breast cancer (IBC) is the most metastatic variant of locally advanced breast cancer. Although IBC is diagnosed less commonly than other types of breast cancer, it is extremely aggressive, and accounts for a disproportionate number of breast cancer related deaths annually. IBC exhibits very specific patterns of lymphangiogenesis and vasculogenic mimicry, however detailed studies of the genes and proteins involved in these angiogenic processes are lacking. This study performed whole unbiased gene transcription studies with validation by protein arrays using all available pre-clinical cell lines and in vivo xenograft models of IBC, including a new model of IBC, FC-IBC01, which exhibits lymphovascular invasion, to identify the specific pathways involved in the distinctive angiogenesis observed in IBC.

Materials and Methods: Real-time quantitative RT-PCR, cDNA microarray gene profiling, immunofluorescence with confocal imaging and protein arrays were used to examine differential expression of specific angiogenic gene families including VEGFA,B,C,D, VEGF Receptor genes, and ANG/TIE genes linked to angiogenesis and lymphangiogenesis.

Results: Activity of the matrix metalloproteinase, MMP-2, is required for IBC tumor cells to undergo vasculogenic mimicry (VM), which is associated with a loss of TIMP-2, a well known inhibitor of angiogenesis. Therapeutics that target MMP activity can successfully inhibit this VM. Furthermore, pre-clinical models of IBC that form IBC tumor emboli exhibit lymphovascular invasion that is associated with distinct patterns of expression of genes that encode for distinct receptor tyrosine kinases that may represent important therapeutic targets for IBC.

Discussion: Identification of the distinct angiogenic pathways that are activated in IBC provides insight into the therapeutic targets that may abrogate the distinct lymphovascular invasion and vasculogenic mimicry that are linked to the aggressive metastasis of IBC.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-05-04.

P1-02-03: The Reciprocal Roles of E-Cadherin and ZEB1 Demonstrate the Mesenchymal-Epithelial Transition as a Primary Characteristic of Inflammatory Breast Cancer

Background: Inflammatory breast cancer (IBC) is a rare but very aggressive form of breast cancer. IBC is characterized by nests of tightly aggregated cells, defined as tumor emboli, that exhibit characteristics of cancer stem cells (CSCs). IBC tumor emboli express E-cadherin which is required to maintain their integrity and our recent evidence demonstrates that expression of E-cadherin by tumor emboli is associated with lack of ZEB1 expression, a transcriptional repressor of E-cadherin. This is at odds with the current hypothesis that metastatic progression is associated with the process of epithelial mesenchymal transition (EMT), with loss of E-cadherin and gain of transcription factors including ZEB1, acquisition of CSC characteristics and enhanced invasive capabilities.

Materials and Methods: shRNA knockdown and over-expression methods, real time PCR arrays, western blotting, and in vitro assays to evaluate proliferation, invasion, growth in soft agar and clonogenicity and in vivo animal studies were used.

Results: Expression of E-cadherin was reduced by shRNA and ZEB1 was expressed in SUM149 IBC tumor cells. Numerous EMT-related genes were upregulated with loss of E-cadherin and gain of ZEB1, including N-cadherin and vimentin. However, there were marginal differences in the in vitro parameters of proliferation, Matrigel invasion and anchorage independent growth in soft agar between SUM149-shECad or SUM149-ZEB1 clones and their respective vector control cells. The loss of E-cadherin and gain of ZEB1 altered the morphology of SUM149 cells when cultured under low adherence conditions permissive for the enrichment of CSC, exhibiting a reversion in grape-like morphology to more well defined spheres, which was accompanied by increased clonogenicity in both SUM149-shECad and SUM149-ZEB1 cells. The loss of E-cadherin and the gain of ZEB1 significantly inhibited tumor growth of cells injected in the mammary fat pad of NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ mice. Tumor volume at 56 days for E-cadherin vector control cells was 771.9 mm3 +/− 185.6 compared to shECadherin tumors, which was 13.6 mm3 +/− 7.2. Tumor volume of ZEB1 vector control tumors was 346.1 mm3 +/− 96 compared to volume of ZEB1 expressing tumors, which was 21.5 mm3 +/− 7.2.Conclusions: E-cadherin with lack of ZEB1 expression in IBC is consistent with a mesenchymal-epithelial transition (MET), consistent with the retention of the epithelial phenotype while maintaining a program of rapid metastasis and colonization of lymph nodes and distant organ sites. Furthermore, we demonstrate that the E-cadherin-ZEB1 axis is critical for the in vivo growth of IBC tumor cells. Although SUM149 cells are fully capable of undergoing an EMT process, which is under negative regulation by E-cadherin, the process of EMT does not drive in vivo tumor growth in IBC.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-02-03.

Serine/threonine protein kinase SGK1 in glucocorticoid-dependent transdifferentiation of pancreatic acinar cells to hepatocytes

Elevated glucocorticoid levels result in the transdifferentiation of pancreatic acinar cells into hepatocytes through a process that requires a transient repression of WNT signalling upstream of the induction of C/EBP-β. However, the mechanism by which glucocorticoid interacts with WNT signalling is unknown. A screen of microarray data showed that the serine/threonine protein kinase SGK1 (serum- and glucocorticoid-regulated kinase 1) was markedly induced in the model B-13 pancreatic rat acinar cell line after glucocorticoid treatment (which converts them into hepatocyte-like 'B-13/H' cells) and this was confirmed at the level of mRNA (notably an alternatively transcribed SGK1C form) and protein. Knockdown of SGK1 using an siRNA designed to target all variant transcripts inhibited glucocorticoid-dependent transdifferentiation, whereas overexpression of the human C isoform (and also the human SGK1F isoform, for which no orthologue in the rat has been identified) alone - but not the wild-type A form - inhibited distal WNT signalling Tcf/Lef transcription factor activity, and converted B-13 cells into B-13/H cells. These effects were lost when the kinase functions of SGK1C and SGK1F were mutated. Inhibition of SGK1 kinase activity also inhibited glucocorticoid-dependent transdifferentiation. Expression of SGK1C and SGK1F resulted in the appearance of phosphorylated β-catenin, and recombinant SGK1 was shown to directly phosphorylate purified β-catenin in vitro in an ATP-dependent reaction. These data therefore demonstrate a crucial role for SGK1 induction in B-13 cell transdifferentiation to B-13/H hepatocytes and suggest that direct phosphorylation of β-catenin by SGK1C represents the mechanism of crosstalk between glucocorticoid and WNT signalling pathways.

Departures from the protocol during conduct of a clinical trial: a pattern from the data record consistent with a learning curve

OBJECTIVE

Recognition of learning curves in medical skill acquisition has enhanced patient safety through improved training techniques. Clinical trials research has not been similarly scrutinised. The VALsartan In Acute myocardial iNfarcTion, a large multinational, pragmatic, randomised, double-blind, multicentre trial, was retrospectively evaluated for evidence of research conduct consistent with a performance "learning curve".

DESIGN

Records provided protocol departure (deviations/violations) and documentation query data. For each site, analysis included patient order (eg, first, second), recruitment rate and first enrollment relative to study start date.

SETTING

Computerised data from a trial coordinated by an academic research organisation collaborating with 10 academic and 2 commercial research organisations and an industry sponsor. Interventions 931 sites enrolled 14,703 patients. Departures were restricted to the first year. Exclusions included patient's death or loss to follow-up within 12 months and subjects enrolled 80th or higher at a site. Departures were assessed for variance with higher patient rank, more frequent recruitment and later start date.

METHODS AND RESULTS

12,367 patients at 931 sites were analysed. Departures were more common for patients enrolled earlier at a site (p<0.0001). For example, compared with the 30th patient, the first had 47% more departures. Departures were also more common with slower enrollment and site start closer to the trial start date (p<0.0001). Similar patterns existed for queries.

CONCLUSIONS

Research performance improved during the VALsartan In Acute myocardial iNfarcTion consistent with a "learning curve". Although effects were not related to a change in outcome (mortality), learning curves in clinical research may have important safety, ethical, research quality and economic implications for trial conduct.