Application of in vivo imaging techniques to monitor therapeutic efficiency of PLX4720 in an experimental model of microsatellite instable colorectal cancer.

OBJECTIVES: Patient-derived tumor cell lines are a powerful tool to analyze the sensitivity of individual tumors to specific therapies in mice. An essential prerequisite for such an approach are reliable quantitative techniques to monitor tumor progression in vivo. METHODS: We have employed HROC24 cells, grown heterotopically in NMRI Foxn1nu mice, as a model of microsatellite instable colorectal cancer to investigate the therapeutic efficiencies of 5'-fluorouracil (5'-FU) and the mutant BRAF inhibitor PLX4720, a vemurafenib analogue, by three independent methods: external measurement by caliper, magnetic resonance imaging (MRI) and positron emission tomography/computed tomography (PET/CT) with 2-deoxy-2-(18F)fluoro-D-glucose (18F-FDG). RESULTS: Repeated measure ANOVA by a general linear model revealed that time-dependent changes of anatomic tumor volumes measured by MRI differed significantly from those of anatomic volumes assessed by caliper and metabolic volumes determined by PET/CT. Over the investigation period of three weeks, neither 5'-FU, PLX4720 nor a combination of both drugs affected the tumor volumes. Also, there was no drug effect on the apparent diffusion constant (ADC) value as detected by MRI. Interestingly, however, PET/CT imaging showed that PLX4720-containing therapies transiently reduced the standardized uptake value (SUV), indicating a temporary response to treatment. CONCLUSIONS: 5'-FU and PLX4720 were largely ineffective with respect to HROC24 tumor growth. Tumoral uptake of 18F-FDG, as expressed by the SUV, proved as a sensitive indicator of small therapeutic effects. Metabolic imaging by 18F-FDG PET/CT is a suitable approach to detect effects of tumor-directed therapies early and even in the absence of morphological changes.

In vitro studies implicate an imbalanced activation of dendritic cells in the pathogenesis of murine autoimmune pancreatitis.

OBJECTIVES: MRL/MpJ mice spontaneously develop an autoimmune pancreatitis (AIP) and are widely used as a model to study the genetic, molecular and immunological basis of the disease. Here, we have addressed the question whether distinctive features of their dendritic cells (DCs) may predispose MRL/MpJ mice to the chronic inflammation. METHODS: Pancreatic lesions were analyzed employing histological methods. Cohorts of young (healthy) MRL/MpJ mice, adult (sick) individuals, and AIP-resistant CAST/EiJ mice were used to establish cultures of bone marrow (BM)-derived conventional DCs (cDCs). The cells were subsequently characterized regarding the expression profile of CD markers and selected genes, proliferative activity as well as cytokine secretion. RESULTS: In pancreatic lesions, large numbers of cells expressing the murine DC marker CD11c were detected in close spatial proximity to CD3+ cells. A high percentage of BM-derived cDCs from adult MRL/MpJ mice expressed typical markers of DC maturation (such as CD83) already prior to a treatment with lipopolysaccharide (LPS). After LPS-stimulation, cDC cultures of both MRL/MpJ mouse cohorts contained more mature cells, proliferated at a higher rate and secreted less interleukin-10 (but also less pro-inflammatory cytokines) than cultures of CAST/EiJ mice. Compared with corresponding cultures of the control strain, LPS-free cultured cDCs from MRL/MpJ mice expressed less mRNA of the inhibitory receptor triggering receptor expressed on myeloid cells 2 (trem2). CONCLUSIONS: BM-derived cDCs from AIP-prone MRL/MpJ mice display functional features that are compatible with the hypothesis of an imbalanced DC activation in the context of murine AIP.

A New Application for Albumin Dialysis in Extracorporeal Organ Support: Characterization of a Putative Interaction Between Human Albumin and Proinflammatory Cytokines IL-6 and TNFα.

Albumin dialysis in extracorporeal organ support is often performed in the treatment of liver failure as it facilitates the removal of toxic components from the blood. Here, we describe a possible effect of albumin dialysis on proinflammatory cytokine levels in vitro. Initially, albumin samples were incubated with different amounts of cytokines and analyzed by enzyme-linked immunosorbent assay (ELISA). Analysis of interleukin 6 (IL-6) and tumor necrosis factor alpha (TNFα) levels indicated that increased concentrations of albumin reduce the measureable amount of the respective cytokines. This led to the hypothesis that the used proinflammatory cytokines may interact with albumin. Size exclusion chromatography of albumin spiked with cytokines was carried out using high-performance liquid chromatography analysis. The corresponding fractions were evaluated by immunoblotting. We detected albumin and cytokines in the same fractions indicating an interaction of the small-sized cytokines IL-6 and TNFα with the larger-sized albumin. Finally, a two-compartment albumin dialysis in vitro model was used to analyze the effect of albumin on proinflammatory cytokines in the recirculation circuit during 6-h treatment. These in vitro albumin dialysis experiments indicated a significant decrease of IL-6, but not of TNFα, when albumin was added to the dialysate solution. Taken together, we were able to show a putative in vitro interaction of human albumin with the proinflammatory cytokine IL-6, but with less evidence for TNFα, and demonstrated an additional application for albumin dialysis in liver support therapy where IL-6 removal might be indicated.

Reduction of elevated cytokine levels in acute/acute-on-chronic liver failure using super-large pore albumin dialysis treatment: an in vitro study.

The removal of small water soluble toxins and albumin-bound toxins in acute liver failure patients (ALF) or acute-on-chronic liver failure (AocLF) patients has been established using extracorporeal liver support devices (e.g. Molecular Adsorbents Recirculating System; MARS). However, reduction of elevated cytokines in ALF/AocLF using MARS is still not efficient enough to lower patients' serum cytokine levels. New membranes with larger pores or higher cut-offs should be considered in extracorporeal liver support devices based on albumin dialysis in order to address these problems, as the introduction of super-large pore membranes could counterbalance high production rates of cytokines and further improve detoxification in vivo. Using an established in vitro two compartment albumin dialysis model, three novel membranes of different pore sizes were compared with the MARS Flux membrane for cytokine removal and detoxification qualities in vitro. Comparing the membranes, no improvement in the removal of water soluble toxins was found. Albumin-bound toxins were removed more efficiently using novel large (Emic2) to super-large pore sized membranes (S20; HCO Gambro). Clearance of cytokines IL-6 and tumor necrosis factor-α was drastically improved using super-large pore membranes. The Emic2 membrane predominantly removed IL-6. In vitro data suggest that the usage of larger pore sized membranes in albumin dialysis can efficiently reduce elevated cytokine levels and liver failure toxins. Using large to super-large pore membranes might exert effects on patients' serum cytokine levels. Combined with increased detoxification this could lead to higher survival in ALF/AocLF. Promising membranes for clinical evaluation have been identified.