Molecular mechanism of intraductal papillary mucinous neoplasm and intraductal papillary mucinous neoplasm‐derived pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDA) is one of the most lethal human malignancies. Dissecting the mechanisms underlying PDA development is important for developing early detection methods and effective prevention and therapies for the disease. PDA is considered to arise from distinct precursor lesions, including pancreatic intraepithelial neoplasia (PanIN) and intraductal papillary mucinous neoplasia (IPMN). However, little is known about molecular mechanisms of development of IPMN and IPMN‐derived PDA. We have recently reported that loss of Brg1, a core subunit of SWI/SNF chromatin remodeling complexes, cooperates with oncogenic Kras to form cystic neoplastic lesions that resemble human IPMN and progress to PDA. Brg1 null IPMN‐PDA is less lethal compared to PanIN‐derived PDA (PanIN‐PDA) driven by mutant Kras and hemizygous p53 deletion, mirroring prognostic trends in PDA patients. Brg1 null IPMN‐PDA possesses a distinct molecular signature that supports less malignant potential compared to PanIN‐PDA. Furthermore, Brg1 deletion inhibits Kras‐dependent PanIN development from adult acinar cells, but promotes Kras‐driven preneoplastic transformation in adult duct cells. Therefore, Brg1 is a determinant of context‐dependent Kras‐driven pancreatic tumorigenesis and chromatin remodeling may underlie the development of distinct PDA subsets. Understanding molecular mechanism of IPMN and IPMN‐derived PDA could provide critical clues for novel diagnostic and therapeutic strategies of the disease.     

Identification of an autoantibody to vascular endothelial cell-specific antigens in patients with systemic vasculitis

PURPOSE: Although immunologic mechanisms have been postulated in the pathogenesis of vasculitis, an autoimmune process directed against specific autologous vascular wall antigens has not been previously documented. We examined the role of an immunologic response to vascular endothelial cell (VEC) antigens in patients with vasculitis, because of the observed immunogenicity of VECs in renal and cardiac allograft recipients. PATIENTS AND METHODS: The study patients included 21 with systemic vasculitis and four with hypersensitivity vasculitis. A healthy, normal control group consisted of 51 young subjects and 61 older subjects. Thirty-two patients with connective tissue diseases were also evaluated. The presence of autoantibody to autologous monocytes and other cell types was determined with previously described standard crossmatch techniques. Patient sera exhibiting autoantibody to autologous monocytes were screened against a panel of allogeneic cells. The cell panel consisted of concordant T and B lymphocytes, monocytes, and VECs from 16 umbilical cord donors. Sera from four patients were analyzed for specificity to the vascular endothelium of frozen sections of vessels. RESULTS: An autoantibody to VEC antigens was detected in 18 of the 21 patients (86%) with confirmed systemic vasculitis, not of the hypersensitivity type. This autoantibody was highly cytotoxic, complement-fixing, and specific for antigens on the surface of the VEC. Findings on allogeneic VEC panel analysis support the existence of multiple allotypes in the VEC antigen system. In three patients, fluctuations in the titer of the autoantibody generally correlated with clinical symptoms. In the four patients screened for the specificity of the autoantibody to anatomically different cadaveric blood vessels, specific anatomic patterns of reactivity were observed. Autoantibody to VEC antigens was not found in young controls and was documented in low frequency in older controls and in patients with connective tissue diseases. The autoantibody was seen in one of four patients (25%) with hypersensitivity vasculitis. CONCLUSION: Our results indicate that an autoantibody to VEC antigens may be involved in the pathogenesis of systemic vasculitis or may be a diagnostic marker for the disease process.     

Positional cloning of the young mutation identifies an essential role for the Brahma chromatin remodeling complex in mediating retinal cell differentiation

Zebrafish with the young (yng) mutation show a defect in retinal cell differentiation. Here we demonstrate that a mutation in a brahma-related gene (brg1) is responsible for the yng phenotype. Brahma homologues function as essential subunits for SWI/SNF-type chromatin remodeling complexes. Our analysis indicates that brg1 is required for the wave of mitogen-activated protein kinase activity that precedes retinal cell differentiation. Using specific inhibitors of the mitogen-activated protein kinase pathway we show this signal has a direct role in retinal cell differentiation. Lastly, through investigations of mutants in other chromatin remodeling subunits, we provide genetic evidence for gene and tissue specificity of the Brahma chromatin remodeling complex.     

Anti-angiogenic effects of resveratrol mediated by decreased VEGF and increased TSP1 expression in melanoma-endothelial cell co-culture

Resveratrol, a naturally occurring polyphenol, has been reported to be an anti-tumor and chemopreventive agent. Recent data show that it may also exert anti-angiogenic effects. We hypothesized that the anti-angiogenic activity of resveratrol may be caused by modulation of tumor cell release of thrombospondin-1 (TSP1) and vascular endothelial growth factor (VEGF) into the extracellular matrix, leading to vascular endothelial cell (VEC) apoptosis. We therefore evaluated the effects of resveratrol on melanoma cell lines co-cultured with vascular endothelial cells in monolayer and in three dimensional spheroids. We found that resveratrol stimulated isolated VEC proliferation, while it caused growth inhibition of VECs grown with melanoma cells in three-dimensional co-culture. This effect was associated with increased melanoma cell expression of tumor suppressor protein 53 and matrix protein TSP1, as well as decreased hypoxia-driven expression of hypoxia inducible factor-1α and inhibition of VEGF production.     

Convergent structural alterations define SWItch/Sucrose NonFermentable (SWI/SNF) chromatin remodeler as a central tumor suppressive complex in pancreatic cancer

Defining the molecular genetic alterations underlying pancreatic cancer may provide unique therapeutic insight for this deadly disease. Toward this goal, we report here an integrative DNA microarray and sequencing-based analysis of pancreatic cancer genomes. Notable among the alterations newly identified, genomic deletions, mutations, and rearrangements recurrently targeted genes encoding components of the SWItch/Sucrose NonFermentable (SWI/SNF) chromatin remodeling complex, including all three putative DNA binding subunits (ARID1A, ARID1B, and PBRM1) and both enzymatic subunits (SMARCA2 and SMARCA4). Whereas alterations of each individual SWI/SNF subunit occurred at modest-frequency, as mutational "hills" in the genomic landscape, together they affected at least one-third of all pancreatic cancers, defining SWI/SNF as a major mutational "mountain." Consistent with a tumor-suppressive role, re-expression of SMARCA4 in SMARCA4-deficient pancreatic cancer cell lines reduced cell growth and promoted senescence, whereas its overexpression in a SWI/SNF-intact line had no such effect. In addition, expression profiling analyses revealed that SWI/SNF likely antagonizes Polycomb repressive complex 2, implicating this as one possible mechanism of tumor suppression. Our findings reveal SWI/SNF to be a central tumor suppressive complex in pancreatic cancer.     

Coculture of Vascular Endothelial Cells and Smooth Muscle Cells from Spontaneously Hypertensive Rats

The effect of endothelium‐released vasoactive factors on vascular smooth muscle cell (VSMC) proliferation was studied in a coculture system. Isolated aortic endothelial cells and smooth muscle cells from 4‐week‐old spontaneously hypertensive rats (SHR) and age‐matched Wistar–Kyoto (WKY) rats were cocultured. After coculture, the VSMC proliferation rate was examined by ³H‐thymidine incorporation assay and the levels of the vasoactive factors in medium were determined by enzyme immunoassay (EIA). The results indicate that the proliferation rate of VSMCs in SHR was significantly higher than in WKY rats when VSMCs were cultured alone. When SHR vascular endothelial cells (VECs) were cocultured with VSMCs, the proliferation rate of SHR VSMCs was enhanced; however, there was no growth promoting effect in WKY VSMCs. When WKY VECs were cocultured with VSMCs, no VSMC proliferation effect was observed. When VSMCs were cultured alone, the endothelin‐1 (ET‐1) secretion in SHR was significantly higher than in WKY rats. When VECs and VSMCs were cocultured, the ET‐1 concentration increased in both SHR VEC and WKY VEC coculture groups in a similar manner; but the SHR VECs tended to release more thromboxaneA₂ (TXA₂) and less PGI₂ than WKY VECs. These results suggest that some kind of interaction between SHR VSMCs and SHR VECs is responsible for the high proliferation of SHR VSMCs but not the effects of SHR VECs per se.