Bmi1 is required for tumorigenesis in a mouse model of intestinal cancer

The epigenetic regulator BMI1 is upregulated progressively in a wide variety of human tumors including colorectal cancer. In this study, we assessed the requirement for Bmi1 in intestinal tumorigenesis using an autochthonous mouse model in which Apc was conditionally ablated in the intestinal epithelium. Germline mutation of Bmi1 significantly reduced both the number and size of small intestinal adenomas arising in this model, and it acted in a dose-dependent manner. Moreover, in contrast to wild-type controls, Bmi1[superscript −/−] mice showed no increase in median tumor size, and a dramatic decrease in tumor number, between 3 and 4 months of age. Thus, Bmi1 is required for both progression and maintenance of small intestinal adenomas. Importantly, Bmi1 deficiency did not disrupt oncogenic events arising from Apc inactivation. Instead, the Arf tumor suppressor, a known target of Bmi1 epigenetic silencing, was upregulated in Bmi1 mutant tumors. This was accompanied by significant upregulation of p53, which was confirmed by sequencing to be wild-type, and also elevated apoptosis within the smallest Bmi1[superscript −/−] adenomas. By crossing Arf into this cancer model, we showed that Arf is required for the induction of both p53 and apoptosis, and it is a key determinant of the ability of Bmi1 deficiency to suppress intestinal tumorigenesis. Finally, a conditional Bmi1 mutant strain was generated and used to determine the consequences of deleting Bmi1 specifically within the intestinal epithelium. Strikingly, intestinal-specific Bmi1 deletion suppressed small intestinal adenomas in a manner that was indistinguishable from germline Bmi1 deletion. Thus, we conclude that Bmi1 deficiency impairs the progression and maintenance of small intestinal tumors in a cell autonomous and highly Arf-dependent manner.Virginia and D.K. Ludwig Fund for Cancer ResearchNational Science Foundation (U.S.)National Cancer Institute (U.S.

Immune Responses to RHAMM in Patients with Acute Myeloid Leukemia after Chemotherapy and Allogeneic Stem Cell Transplantation

Leukemic blasts overexpress immunogenic antigens, so-called leukemia-associated antigens like the receptor for hyaluronan acid-mediated motility (RHAMM). Persistent RHAMM expression and decreasing CD8+ T-cell responses to RHAMM in the framework of allogeneic stem cell transplantation or chemotherapy alone might indicate the immune escape of leukemia cells. In the present study, we analyzed the expression of RHAMM in 48 patients suffering from acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). Furthermore, we correlated transcripts with the clinical course of the disease before and after treatment. Real-time quantitative reverse transcriptase polymerase chain reaction was performed from RNA of peripheral blood mononuclear cells. T cell responses against RHAMM were assessed by tetramer staining (flow cytometry) and enzyme-linked immunospot (ELISPOT) assays. Results were correlated with the clinical outcome of patients. The results of the present study showed that almost 60% of the patients were RHAMM positive; specific T-cells recognizing RHAMM could be detected, but they were nonfunctional in terms of interferon gamma or granzyme B release as demonstrated by ELISPOT assays. Immunotherapies like peptide vaccination or adoptive transfer of RHAMM-specific T cells might improve the immune response and the outcome of AML/MDS patients

P2Y₁₂-dependent activation of hematopoietic stem and progenitor cells promotes emergency hematopoiesis after myocardial infarction

Emergency hematopoiesis is the driving force of the inflammatory response to myocardial infarction (MI). Increased proliferation of hematopoietic stem and progenitor cells (LSK) after MI enhances cell production in the bone marrow (BM) and replenishes leukocyte supply for local cell recruitment to the infarct. Decoding the regulation of the inflammatory cascade after MI may provide new avenues to improve post-MI remodeling. In this study, we describe the influence of adenosine diphosphate (ADP)-dependent P2Y12-mediated signaling on emergency hematopoiesis and cardiac remodeling after MI. Permanent coronary ligation was performed to induce MI in a murine model. BM activation, inflammatory cell composition and cardiac function were assessed using global and platelet-specific gene knockout and pharmacological inhibition models for P2Y12. Complementary in vitro studies allowed for investigation of ADP-dependent effects on LSK cells. We found that ADP acts as a danger signal for the hematopoietic BM and fosters emergency hematopoiesis by promoting Akt phosphorylation and cell cycle progression. We were able to detect P2Y12 in LSK, implicating a direct effect of ADP on LSK via P2Y12 signaling. P2Y12 knockout and P2Y12 inhibitor treatment with prasugrel reduced emergency hematopoiesis and the excessive inflammatory response to MI, translating to lower numbers of downstream progeny and inflammatory cells in the blood and infarct. Ultimately, P2Y12 inhibition preserved cardiac function and reduced chronic adverse cardiac remodeling after MI. P2Y12-dependent signaling is involved in emergency hematopoiesis after MI and fuels post-ischemic inflammation, proposing a novel, non-canonical value for P2Y12 antagonists beyond inhibition of platelet-mediated atherothrombosis

Local proliferation dominates lesional macrophage accumulation in atherosclerosis

During the inflammatory response that drives atherogenesis, macrophages accumulate progressively in the expanding arterial wall1,2. The observation that circulating monocytes give rise to lesional macrophages3–9 has reinforced the concept that monocyte infiltration dictates macrophage build-up. Recent work indicates, however, that macrophages do not depend on monocytes in some inflammatory contexts10. We therefore revisited the mechanism of macrophage accumulation in atherosclerosis. We show that murine atherosclerotic lesions experience a surprisingly rapid, 4-week, cell turnover. Replenishment of macrophages in these experimental atheromata depends predominantly on local macrophage proliferation rather than monocyte influx. The microenvironment orchestrates macrophage proliferation via the involvement of scavenger receptor (SR)-A. Our study reveals macrophage proliferation as a key event in atherosclerosis and identifies macrophage self-renewal as a therapeutic target for cardiovascular disease

The transcription factor NR4A1 is essential for the development of a novel macrophage subset in the thymus

Tissue macrophages function to maintain homeostasis and regulate immune responses. While tissue macrophages derive from one of a small number of progenitor programs, the transcriptional requirements for site-specific macrophage subset development are more complex. We have identified a new tissue macrophage subset in the thymus and have discovered that its development is dependent on transcription factor NR4A1. Functionally, we find that NR4A1-dependent macrophages are critically important for clearance of apoptotic thymocytes. These macrophages are largely reduced or absent in mice lacking NR4A1, and Nr4a1-deficient mice have impaired thymocyte engulfment and clearance. Thus, NR4A1 functions as a master transcription factor for the development of this novel thymus-specific macrophage subset

Downregulation of organic cation transporters OCT1 (SLC22A1) and OCT3 (SLC22A3) in human hepatocellular carcinoma and their prognostic significance

<p>Abstract</p> <p>Background</p> <p>Organic cation transporters (OCT) are responsible for the uptake and intracellular inactivation of a broad spectrum of endogenous substrates and detoxification of xenobiotics and chemotherapeutics. The transporters became pharmaceutically interesting, because OCTs are determinants of the cytotoxicity of platin derivates and the transport activity has been shown to correlate with the sensitivity of tumors towards tyrosine kinase inhibitors. No data exist about the relevance of OCTs in hepatocellular carcinoma (HCC).</p> <p>Methods</p> <p>OCT1 (<it>SLC22A1</it>) and OCT3 (<it>SLC22A3</it>) mRNA expression was measured in primary human HCC and corresponding non neoplastic tumor surrounding tissue (TST) by real time PCR (n = 53). Protein expression was determined by western blot analysis and immunofluorescence. Data were correlated with the clinicopathological parameters of HCCs.</p> <p>Results</p> <p>Real time PCR showed a downregulation of <it>SLC22A1 </it>and <it>SLC22A3 </it>in HCC compared to TST (p ≤ 0.001). A low <it>SLC22A1 </it>expression was associated with a worse patient survival (p < 0.05). Downregulation was significantly associated with advanced HCC stages, indicated by a higher number of T3 tumors (p = 0.025) with a larger tumor diameter (p = 0.035), a worse differentiation (p = 0.001) and higher AFP-levels (p = 0.019). In accordance, <it>SLC22A1 </it>was less frequently downregulated in tumors with lower stages who underwent transarterial chemoembolization (p < 0.001) and liver transplantation (p = 0.001). Tumors with a low <it>SLC22A1 </it>expression (< median) showed a higher <it>SLC22A3 </it>expression compared to HCC with high <it>SLC22A1 </it>expression (p < 0.001). However, there was no significant difference in tumor characteristics according to the level of the <it>SLC22A3 </it>expression.</p> <p>In the western blot analysis we found a different protein expression pattern in tumor samples with a more diffuse staining in the immunofluorescence suggesting that especially OCT1 is not functional in advanced HCC.</p> <p>Conclusion</p> <p>The downregulation of OCT1 is associated with tumor progression and a worse patient survival.</p

Characterization of Rhodamine-123 as a Tracer Dye for Use In In vitro Drug Transport Assays

Fluorescent tracer dyes represent an important class of sub-cellular probes and allow the examination of cellular processes in real-time with minimal impact upon these processes. Such tracer dyes are becoming increasingly used for the examination of membrane transport processes, as they are easy-to-use, cost effective probe substrates for a number of membrane protein transporters. Rhodamine 123, a member of the rhodamine family of flurone dyes, has been used to examine membrane transport by the ABCB1 gene product, MDR1. MDR1 is viewed as the archetypal drug transport protein, and is able to efflux a large number of clinically relevant drugs. In addition, ectopic activity of MDR1 has been associated with the development of multiple drug resistance phenotype, which results in a poor patient response to therapeutic intervention. It is thus important to be able to examine the potential for novel compounds to be MDR1 substrates. Given the increasing use rhodamine 123 as a tracer dye for MDR1, a full characterisation of its spectral properties in a range of in vitro assay-relevant media is warranted. Herein, we determine λmax for excitation and emission or rhodamine 123 and its metabolite rhodamine 110 in commonly used solvents and extraction buffers, demonstrating that fluorescence is highly dependent on the chemical environment: Optimal parameters are 1% (v/v) methanol in HBSS, with λex = 505 nm, λem = 525 nm. We characterise the uptake of rhodamine 123 into cells, via both passive and active processes, and demonstrate that this occurs primarily through OATP1A2-mediated facilitated transport at concentrations below 2 µM, and via micelle-mediated passive diffusion above this. Finally, we quantify the intracellular sequestration and metabolism of rhodamine 123, demonstrating that these are both cell line-dependent factors that may influence the interpretation of transport assays

The multidrug resistance 1 (MDR1) gene polymorphism G-rs3789243-A is not associated with disease susceptibility in Norwegian patients with colorectal adenoma and colorectal cancer; a case control study

<p>Abstract</p> <p>Background</p> <p>Smoking, dietary factors, and alcohol consumption are known life style factors contributing to gastrointestinal carcinogenesis. Genetic variations in carcinogen handling may affect cancer risk. The multidrug resistance 1(<it>MDR1/ABCB1</it>) gene encodes the transport protein P-glycoprotein (a phase III xenobiotic transporter). P-glycoprotein is present in the intestinal mucosal lining and restricts absorption of certain carcinogens, among these polycyclic aromatic hydrocarbons. Moreover, P-glycoprotein transports various endogenous substrates such as cytokines and chemokines involved in inflammation, and may thereby affect the risk of malignity. Hence, genetic variations that modify the function of P-glycoprotein may be associated with the risk of colorectal cancer (CRC). We have previously found an association between the <it>MDR1 </it>intron 3 G-rs3789243-A polymorphism and the risk of CRC in a Danish study population. The aim of this study was to investigate if this <it>MDR1 </it>polymorphism was associated with risk of colorectal adenoma (CA) and CRC in the Norwegian population.</p> <p>Methods</p> <p>Using a case-control design, the association between the <it>MDR1 </it>intron 3 G-rs3789243-A polymorphism and the risk of colorectal carcinomas and adenomas in the Norwegian population was assessed in 167 carcinomas, 990 adenomas, and 400 controls. Genotypes were determined by allelic discrimination. Odds ratio (OR) and 95 confidence interval (95% CI) were estimated by binary logistic regression.</p> <p>Results</p> <p>No association was found between the <it>MDR1 </it>polymorphism (G-rs3789243-A) and colorectal adenomas or cancer. Carriers of the variant allele of MDR1 intron 3 had odds ratios (95% CI) of 0.97 (0.72–1.29) for developing adenomas, and 0.70 (0.41–1.21) for colorectal cancer, respectively, compared to homozygous wild type carriers.</p> <p>Conclusion</p> <p>The <it>MDR1 </it>intron 3 (G-rs3789243-A) polymorphism was not associated with a risk of colorectal adenomas or carcinomas in the present Norwegian study group. Thus, this <it>MDR1 </it>polymorphism does not seem to play an important role in colorectal carcinogenesis in this population.</p