Circulating tumor cells (CTC) enter the blood from many carcinomas and represent a likely source of metastatic dissemination. In contrast to the peripheral circulation, KRAS mutation- positive CTC thrive in the portal venous blood of patients with pancreatic ductal adenocarcinoma (PDAC). To analyze the essential interactions that contribute to carcinoma CTC growth and immune resistance, portal venous blood was collected during pancreatico-duodenectomy in 41 patients with peri-ampullary pathologies (PDAC = 11; ampullary adenocarcinoma (AA) = 15; distal cholangiocarcinoma (CC) = 6; IPMN = 7; non-malignant pancreatitis = 2). FACS-isolated cell populations from the portal circulation were reconstituted ex vivo using mixed cell reaction cultures (MCR). During the first 48hr, PDAC, AA, and CC patient CTC were all highly proliferative (mean 1.7 hr/cell cycle, 61.5% ± 20% growing cells) and resistant to apoptosis (mean 39% ±  25% apoptotic cells). PDAC CTC proliferation and resistance to T cell cytotoxicity were decreased among patients who received pre-operative chemotherapy (p = 0.0019, p = 0.0191, respectively). After 7 days in culture, CTC from PDAC, CC, and AA patients recruited multiple immune cell types, including CD105 + CD14 + myeloid fibroblasts, to organize into spheroid-like clusters. It was only in PDAC and CC-derived MCR that cluster formation promoted CTC survival, growth, and fibroblast differentiation. FACS depletion of CTC or myeloid fibroblast cells eliminated cluster network formation, and re-introduction of these cell populations reconstituted such ability. Our findings suggest that PDAC and CC CTC survival within the portal venous circulation is supported by their interactions with immune cells within multi-cell type clusters that could represent vectors of local recurrence and metastatic progression.

Background: Silver nanoparticles (AgNPs) and silver (Ag)-based materials are increasingly being incorporated into consumer products, and although humans have been exposed to colloidal Ag in many forms for decades, this rise in the use of Ag materials has spurred interest into their toxicology. Recent reports have shown that exposure to AgNPs or Ag ions leads to oxidative stress, endoplasmic reticulum stress, and reduced cell proliferation. Previous studies have shown that Ag accumulates in tissues as silver sulfides (Ag2S) and silver selenide (Ag2Se).Objectives: In this study we investigated whether exposure of cells in culture to AgNPs or Ag ions at subtoxic doses would alter the effective metabolism of selenium, that is, the incorporation of selenium into selenoproteins.Methods: For these studies we used a keratinocyte cell model (HaCat) and a lung cell model (A549). We also tested (in vitro, both cellular and chemical) whether Ag ions could inhibit the activity of a key selenoenzyme, thioredoxin reductase (TrxR).Results: We found that exposure to AgNPs or far lower levels of Ag ions led to a dose-dependent inhibition of selenium metabolism in both cell models. The synthesis of protein was not altered under these conditions. Exposure to nanomolar levels of Ag ions effectively blocked selenium metabolism, suggesting that Ag ion leaching was likely the mechanism underlying observed changes during AgNP exposure. Exposure likewise inhibited TrxR activity in cultured cells, and Ag ions were potent inhibitors of purified rat TrxR isoform 1 (cytosolic) (TrxR1) enzyme.Conclusions: Exposure to AgNPs leads to the inhibition of selenoprotein synthesis and inhibition of TrxR1. Further, we propose these two sites of action comprise the likely mechanism underlying increases in oxidative stress, increases endoplasmic reticulum stress, and reduced cell proliferation during exposure to Ag.

Vibrio vulnificus infections are associated with raw oyster consumption, and disease reservoirs are determined by the ability of this bacterium to infect and persist in oysters. Surface structures, such as capsular polysaccharide (CPS), pili and flagella, function as virulence factors in mouse infection models. Furthermore, virulence is related to phase variation in colony morphology, which reflects CPS expression and includes opaque (encapsulated, virulent), translucent (reduced encapsulation, avirulent) and rugose (wrinkled, biofilm-enhanced) colony types. The role of these factors in environmental survival is unknown; therefore, mutational analysis and phase variation of V. vulnificus were examined in an oyster infection model. Oysters (Crassostrea virginica) were pre-treated with tetracycline to reduce background bacteria and subsequently inoculated via filter feeding with 10(6) colony-forming units (cfu) ml(-1) of V. vulnificus wild-type strains and phase variants, as well as strains with deletion mutations in genes related to CPS (Delta wza), pili (Delta pilA), flagella (Delta flaCDE/Delta flaFBA) and motility (Delta motAB). All mutants were significantly reduced in their dissemination to oyster haemolymph as compared with wild type; however, recovery of mutants from gills and intestinal tissue was generally similar to wild type. Translucent and rugose inocula showed induction of high-frequency phase variation to the opaque encapsulated phenotype (100% and 72% respectively) during oyster infections that did not occur in strains recovered from seawater. Thus, multiple bacterial factors determine uptake of V. vulnificus in oysters, and phase variation during oyster infection is a likely mechanism for environmental survival and for induction of the more virulent phenotype.

Selenium has been shown to be present as a labile cofactor in a small class of molybdenum hydroxylase enzymes in several species of clostridia that specialize in the fermentation of purines and pyrimidines. This labile cofactor is poorly understood, yet recent bioinformatic studies have suggested that Enterococcus faecalis could serve as a model system to better understand the way in which this enzyme cofactor is built and the role of these metalloenzymes in the physiology of the organism. An mRNA that encodes a predicted seleniumdependent molybdenum hydroxylase (SDMH) has also been shown to be specifically increased during the transition from planktonic growth to biofilm growth. Based on these studies, we examined whether this organism produces an SDMH and probed whether selenoproteins may play a role in biofilm physiology. We observed a substantial increase in biofilm density upon the addition of uric acid to cells grown in a defined culture medium, but only when molybdate (Mo) and selenite (Se) were also added. We also observed a significant increase in biofilm density in cells cultured in tryptic soy broth with 1% glucose (TSBG) when selenite was added. In-frame deletion of selD, which encodes selenophosphate synthetase, also blocked biofilm formation that occurred upon addition of selenium. Moreover, mutation in the gene encoding the molybdoenzyme (xdh) prevented the induction of biofilm proliferation upon supplementation with selenium. Tungstate or auranofin addition also blocked this enhanced biofilm density, likely through inhibition of molybdenum or selenium cofactor synthesis. A large protein complex labeled with 75 Se is present in higher concentrations in biofilms than in planktonic cells, and the same complex is formed in TSBG. Xanthine dehydrogenase activity correlates with the presence of this labile selenoprotein complex and is absent in a selD or an xdh mutant. Enhanced biofilm density correlates strongly with higher levels of extracellular peroxide, which is produced upon the addition of selenite to TSBG. Peroxide levels are not increased in either the selD or the xdh mutant upon addition of selenite. Extracellular superoxide production, a phenomenon well established to be linked to clinical isolates, is abolished in both mutant strains. Taken together, these data provide evidence that an SDMH is involved in biofilm formation in Enterococcus faecalis, contributing to oxidant production either directly or alternatively through its involvement in redox-dependent processes linked to oxidant production.

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The portal venous circulation provides a conduit for pancreatic ductal adenocarcinoma (PDAC) tumor cells to the liver parenchyma sinusoids, a frequent site of metastasis. Turbulent flow in the portal circulation promotes retention of PDAC shed circulating tumor cells (CTC) and myeloid-derived immunosuppressor cells (MDSC). Excessive colony stimulating factor-1 receptor (CSF1R) signaling can induce myeloid differentiation to MDSC and transformation of MDSC to myeloid-derived fibroblasts (M-FB). Interactions between PDAC CTC and M-FB in the portal blood promotes the formation of immunoresistant clusters that enhance CTC proliferation, migration, and survival. Analysis of portal and peripheral blood samples collected intraoperatively from 30 PDAC patients undergoing pancreatico-duodenectomy showed that PDAC patient plasma contained high levels of macrophage colony stimulating factor (M-CSF/CSF1), granulocyte-macrophage colony stimulating factor (GM-CSF/CSF2), interleukin-8 (IL-8), and interleukin-34 (IL-34) compared to healthy control levels. Moreover, the level of M-CSF in portal blood was significantly higher than that detected in the peripheral blood of PDAC patients. PDAC CTC aseptically isolated by fluorescence activated cell sorting (FACS) out of freshly collected patient portal blood mononuclear cells (PortalBMC) had elevated RNA expression of IL34 (IL-34 gene) and CSF1 (M-CSF/CSF1 gene) which both signal through CSF1R. PDAC CTC also had high levels of RNA expression for CXCL8, the gene encoding chemokine interleukin-8 (IL-8) which can attract myeloid cells through their CXCR2 receptors. FACS-isolated portal PDAC CTC and M-FB co-cultured ex vivo had increased CTC proliferation, motility, and cluster formation compared to CTC cultured alone. CSF1R and CXCR2 cell surface expression were found on PDAC portal blood CTC and M-FB, suggesting that both cell types may respond to M-CSF, IL-34, and IL-8-mediated signaling. Portal PDAC CTC displayed enhanced RNA expression of CSF1 and IL34, while CTC+M-FB+ clusters formed in vivo had increased RNA expression of CSF2 and IL34. Portal M-FB were found to have high CSF1R RNA expression. CTC isolated from ex vivo 7-day cultures of PDAC patient portal blood mononuclear cells (PortalBMC) expressed elevated CSF1, IL34, and IL8 RNA, and CSF1 expression was elevated in M-FB. Treatment with rabbit anti-CSF1R antibodies decreased CTC proliferation. Treatment of PortalBMC cultures with humanized anti-CSF1R, humanized anti-IL-8, or anti-IL-34 antibodies disrupted CTC cluster formation and increased CTC apoptosis. U937 myeloid precursor cell line cultures treated with conditioned media from PortalBMC ex vivo cultures without treatment or treated with anti-IL-8 and/or anti-CSF1R did not prevent myeloid differentiation in the myeloid precursor cell line U937 to macrophage, dendritic cell, MDSC, and M-FB phenotypes; whereas, U937 cultures treated with conditioned media from PortalBMC ex vivo cultures exposed to anti-IL-34 were significantly inhibited in their myeloid differentiation to all but the M-FB phenotype. PDAC patient T cells that were found phenotypically anergic (CD3+CD25+CTLA4+PD1L1+) in PortalBMC could be re-activated (CD3+CD25+CTLA4-PD1L1-), and displayed increased interferon gamma (IFNγ) production when PortalBMC ex vivo cultures were treated with anti-CSF1R, anti-IL-8, and anti-IL-34 antibodies alone or in combination. These findings suggest that PDAC CTC have the potential to influence myeloid differentiation and/or antigen presenting cell activation in the PDAC portal blood microenvironment, and that disruption of CTC/M-FB interactions may be potential targets for reversing the immunosuppression supporting CTC survival in the portal blood.

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Studies have shown enhanced survival of ovarian cancer patients in which the tumors are infiltrated with tumor infiltrating lymphocytes and natural killer cells showing the importance of immune surveillance and recognition in ovarian cancer. Therefore, in this study, we tested cellular immunotherapy and varying combinations of cytokines (IL-2 and/or pegylated-IFNα-2b) in a xenograft mouse model of ovarian cancer. SKOV3-AF2 ovarian cancer cells were injected intra-peritoneally (IP) into athymic nude mice. On day 7 post-tumor cell injection, mice were injected IP with peripheral blood mononuclear cells (PBMC; 5 × 10(6) PBMC) and cytokine combinations [IL-2 ± pegylated-IFNα-2b (IFN)]. Cytokine injections were continued weekly for IFN (12,000 U/injection) and thrice weekly for IL-2 (4000 U/injection). Mice were euthanized when they became moribund due to tumor burden at which time tumor and ascitic fluid were measured and collected. Treatment efficacy was measured by improved survival at 8 weeks and overall survival by Kaplan-Meier analysis. We observed that the mice tolerated all treatment combinations without significant weight loss or other apparent illness. Mice receiving PBMC plus IL-2 showed improved median survival (7.3 weeks) compared to mice with no treatment (4.2 weeks), IL-2 (3.5 weeks), PBMC (4.0 weeks), or PBMC plus IL-2 and IFN (4.3 weeks), although PBMC plus IL-2 was not statistically different than PBMC plus IFN (5.5 weeks, p > 0.05). We demonstrate that cytokine-stimulated cellular immune therapy with PBMC and IL-2 was well tolerated and resulted in survival advantage compared to untreated controls and other cytokine combinations in the nude-mouse model.