Faculty Bibliography

During obesity, macrophage accumulation in adipose tissue propagates the chronic inflammation and insulin resistance associated with type 2 diabetes. The factors, however, that regulate the accrual of macrophages in adipose tissue are not well understood. Here we show that the neuroimmune guidance cue netrin-1 is highly expressed in obese but not lean adipose tissue of humans and mice, where it directs the retention of macrophages. Netrin-1, whose expression is induced in macrophages by the saturated fatty acid palmitate, acts via its receptor Unc5b to block their migration. In a mouse model of diet-induced obesity, we show that adipose tissue macrophages exhibit reduced migratory capacity, which can be restored by blocking netrin-1. Furthermore, hematopoietic deletion of Ntn1 facilitates adipose tissue macrophage emigration, reduces inflammation and improves insulin sensitivity. Collectively, these findings identify netrin-1 as a macrophage retention signal in adipose tissue during obesity that promotes chronic inflammation and insulin resistance.

RAS is the most frequently mutated oncogene in human cancers. Despite decades of effort, anti-RAS therapies have remained elusive. Isoprenylcysteine carboxylmethyltransferase (ICMT) methylates RAS and other CaaX-containing proteins, but its potential as a target for cancer therapy has not been fully evaluated. We crossed a Pdx1-Cre;LSL-KrasG12D mouse, which is a model of pancreatic ductal adenocarcinoma (PDA), with a mouse harboring a floxed allele of Icmt. Surprisingly, we found that ICMT deficiency dramatically accelerated the development and progression of neoplasia. ICMT-deficient pancreatic ductal epithelial cells had a slight growth advantage and were resistant to premature senescence by a mechanism that involved suppression of cyclin-dependent kinase inhibitor 2A (p16INK4A) expression. ICMT deficiency precisely phenocopied Notch1 deficiency in the Pdx1-Cre;LSL-KrasG12D model by exacerbating pancreatic intraepithelial neoplasias, promoting facial papillomas, and derepressing Wnt signaling. Silencing ICMT in human osteosarcoma cells decreased Notch1 signaling in response to stimulation with cell-surface ligands. Additionally, targeted silencing of Ste14, the Drosophila homolog of Icmt, resulted in defects in wing development, consistent with Notch loss of function. Our data suggest that ICMT behaves like a tumor suppressor in PDA because it is required for Notch1 signaling.

Pancreatic cancer is the most common cancer among men and women; the fourth leading cause of cancer death in the United States and the fifth leading cause of cancer death worldwide. This disease has a poor prognosis with a 5-year overall survival rate of less than 20%. Multiple mechanisms have been postulated for the development of benign and malignant pancreatic diseases. However, the nature and origin of the precursor cells for pancreatic cancer have not yet been delineated. Based on several molecular mechanism(s) proposed for pancreatic cancer, the phosphoinositide 3-kinase (PI3K)/Akt pathway is found to be constitutively activated and the mammalian target of rapamycin (mTOR) kinase is reported to be an important mediator for its signaling. The phosphoinositide 3-kinase-AKT-mammalian target of rapamycin (PI3K-AKT-mTOR) pathway is a frequently hyper activated pathway in cancer and is important for tumor cell growth and survival. The development of targeted therapies against mTOR pathway led to the approval of drugs including everolimus and temsirolimus, for the treatment pancreatic and other cancer types. However, the effectiveness and response among high risk patients still remains unclear. Epidemiologic and laboratory studies suggest that plant-derived bioactive food components reverse or prevent the development and progression of early-stage disease before it becomes aggressive and malignant. Lately, naturally occurring non-toxic dietary compounds are increasingly used as a novel strategy for the prevention of more aggressive cancers. Previous reports from our laboratory suggest that prolonged exposure of cancer cells to natural agents may effectively modulate mTOR signaling and promote anti-proliferative effects. In the present study, we evaluated the effectiveness of celastrol in human (AsPC-1) and mouse (Pan-02) pancreatic cancer cells. Celastrol is a plant extract isolated from the root extract of Tripterygium Wilfordi (Thunder of God vine -TGV) and Celastrus Regelii, is also known as !

Non-alcoholic steatohepatitis (NASH) is the most common etiology of chronic liver dysfunction in the United States and can progress to cirrhosis and liver failure. Inflammatory insult resulting from fatty infiltration of the liver is central to disease pathogenesis. Dendritic cells (DC) are antigen presenting cells with an emerging role in hepatic inflammation. We postulated that DC are important in the progression of NASH. We found that intrahepatic DC expand and mature in NASH liver and assume an activated immune-phenotype. However, rather than mitigating the severity of NASH, DC depletion markedly exacerbated intrahepatic fibro-inflammation. Our mechanistic studies support a regulatory role for DC in NASH by limiting sterile inflammation via their role in clearance of apoptotic cells and necrotic debris. We found that DC limit CD8(+) T cell expansion and restrict Toll-like receptor expression and cytokine production in innate immune effector cells in NASH, including Kupffer cells, neutrophils, and inflammatory monocytes. Consistent with their regulatory role in NASH, during the recovery phase of disease, ablation of DC populations results in delayed resolution of intrahepatic inflammation and fibroplasia. Conclusion: Our findings support a role for DC in modulating NASH. Targeting DC functional properties may hold promise for therapeutic intervention in NASH. (HEPATOLOGY 2013.).

Dendritic cells (DC) are professional APCs that regulate innate and adaptive immunity. The role of fatty-acid synthesis in DC development and function is uncertain. We found that blockade of fatty-acid synthesis markedly decreases dendropoiesis in the liver and in primary and secondary lymphoid organs in mice. Human DC development from PBMC precursors was also diminished by blockade of fatty-acid synthesis. This was associated with higher rates of apoptosis in precursor cells and increased expression of cleaved caspase-3 and BCL-xL and downregulation of cyclin B1. Further, blockade of fatty-acid synthesis decreased DC expression of MHC class II, ICAM-1, B7-1, and B7-2 but increased their production of selected proinflammatory cytokines including IL-12 and MCP-1. Accordingly, inhibition of fatty-acid synthesis enhanced DC capacity to activate allogeneic as well as Ag-restricted CD4(+) and CD8(+) T cells and induce CTL responses. Further, blockade of fatty-acid synthesis increased DC expression of Notch ligands and enhanced their ability to activate NK cell immune phenotype and IFN-gamma production. Because endoplasmic reticulum (ER) stress can augment the immunogenic function of APC, we postulated that this may account for the higher DC immunogenicity. We found that inhibition of fatty-acid synthesis resulted in elevated expression of numerous markers of ER stress in humans and mice and was associated with increased MAPK and Akt signaling. Further, lowering ER stress by 4-phenylbutyrate mitigated the enhanced immune stimulation associated with fatty-acid synthesis blockade. Our findings elucidate the role of fatty-acid synthesis in DC development and function and have implications to the design of DC vaccines for immunotherapy.

Introduction: Portal/mesenteric vein resection (PVR) is technically challenging and adds potential morbidity to a pancreaticoduodenectomy (PD). We reviewed our experience with PD for pancreatic adenocarcinoma to evaluate both short and long term outcomes following PVR. Methods: From our institutional pancreatic adenocarcinoma database, we identified 223 patients who underwent pancreaticoduodenectomy (PD) with (Group I n= 20) or without (Group II n= 203) PVR during the period 1990-2011. The study end-points were overall morbidity, 30-day mortality, length of post-operative stay (LOS), overall survival (OS). Differences between groups were evaluated using t-test or chi-squared test. OS for each group was estimated with Kaplan-Meier method and compared using the log-rank statistics. Results: The two groups were similar in terms of gender, age, ethnicity, underlying comorbidities and performance status (see table 1). One patient in Group I and 8 in Group II were deemed borderline resectable (5.0% vs. 3.9%, p = 0.8) and underwent neo-adjuvant treatment. Duration of surgery was longer in Group I (532 vs. 456 min, p = 0.04), but there were no differences in operative blood losses (1047 vs. 991 ml, p = 0.8), length of stay (13.9 vs. 14.4 days, p = 0.8), overall morbidity (55% vs. 38%, p = 0.14). There were only 2 post-operative deaths, both in the Group II (p = 0.7). Pathology revealed similar TNM stage and rates of resections with negative margins (85% vs. 75%, p = 0.8). At median follow-up of 14 months there was no significant difference in OS (20.5 vs. 15.8 months, p = 0.6) Conclusions: In our experience, post-operative and long-term outcomes were not adversely affected by PVR. PVR should be offered to patients with pancreatic cancer involving portal or mesenteric veins. (Table Presented)