[Show abstract][Hide abstract] ABSTRACT: Aspergillus fumigatus forms ubiquitous airborne conidia that humans inhale on a daily basis. Although respiratory fungal infection activates the adaptor proteins CARD9 and MyD88 via C-type lectin, Toll-like, and interleukin-1 family receptor signals, defining the temporal and spatial pattern of MyD88- and CARD9-coupled signals in immune activation and fungal clearance has been difficult to achieve. Herein, we demonstrate that MyD88 and CARD9 act in two discrete phases and in two cellular compartments to direct chemokine- and neutrophil-dependent host defense. The first phase depends on MyD88 signaling because genetic deletion of MyD88 leads to delayed induction of the neutrophil chemokines CXCL1 and CXCL5, delayed neutrophil lung trafficking, and fatal pulmonary damage at the onset of respiratory fungal infection. MyD88 expression in lung epithelial cells restores rapid chemokine induction and neutrophil recruitment via interleukin-1 receptor signaling. Exogenous CXCL1 administration reverses murine mortality in MyD88-deficient mice. The second phase depends predominately on CARD9 signaling because genetic deletion of CARD9 in radiosensitive hematopoietic cells interrupts CXCL1 and CXCL2 production and lung neutrophil recruitment beyond the initial MyD88-dependent phase. Using a CXCL2 reporter mouse, we show that lung-infiltrating neutrophils represent the major cellular source of CXCL2 during CARD9-dependent recruitment. Although neutrophil-intrinsic MyD88 and CARD9 function are dispensable for neutrophil conidial uptake and killing in the lung, global deletion of both adaptor proteins triggers rapidly progressive invasive disease when mice are challenged with an inoculum that is sub-lethal for single adapter protein knockout mice. Our findings demonstrate that distinct signal transduction pathways in the respiratory epithelium and hematopoietic compartment partially overlap to ensure optimal chemokine induction, neutrophil recruitment, and fungal clearance within the respiratory tract.
[Show abstract][Hide abstract] ABSTRACT: Hepatocarcinogenesis results from the accumulation of genetic and epigenetic changes in liver cells. A common mechanism through which these alterations induce liver cancer is by deregulating signaling pathways. A number of signaling pathways, including the PI3K/PTEN/AKT and transforming growth factor β (TGF-β) pathways have been implicated in normal liver development as well as in cancer formation. In this study, we assessed the effect of the TGF-β signaling pathway on liver tumors induced by phosphatase and tensin homolog (Pten) loss. Inactivation of only the TGF-β receptor type II, Tgfbr2, in the mouse liver (Tgfbr2LKO) had no overt phenotype, while inactivation of Pten alone (PtenLKO), resulted in the formation of both hepatocellular carcinomas and cholangiocarcinomas (CC). Interestingly, deletion of both Pten and Tgfbr2 (PtenLKO;Tgfbr2LKO) in the mouse liver resulted in a dramatic shift in tumor type to predominantly CC. Assessment of the PI3K/PTEN/AKT pathway revealed increased phosphorylation of AKT and glycogen synthase kinase 3 beta (GSK-3β) in both the PtenLKO and PtenLKO;Tgfbr2LKO mice, suggesting that this pathway is constitutively active regardless of the status of the TGF-β signaling pathway. However, phosphorylation of p70 S6 kinase was observed in the liver of all three phenotypes (Tgfbr2LKO, PtenLKO, PtenLKO;Tgfbr2LKO) indicating that the loss of Tgfbr2 and/or Pten leads to an increase in this signaling pathway. Analysis of markers of liver progenitor/stem cells revealed that the loss of TGF-β signaling resulted in increased expression of c-Kit and CD133. Furthermore, in addition to increased c-Kit and CD133, Scf and EpCam expression were also increased in the double knock-out mice. These results suggest that the alteration in tumor types between the PtenLKO mice and PtenLKO;Tgfbr2LKO mice is secondary to the altered regulation of stem-cell features induced by the loss of TGF-β signaling.
[Show abstract][Hide abstract] ABSTRACT: Candida albicans is a commensal fungus that can cause systemic disease in patients with breaches in mucosal integrity, indwelling catheters, and defects in phagocyte function. Although circulating human and murine monocytes bind C. albicans and promote inflammation, it remains unclear whether -CC- chemokine receptor 2 (CCR2)- and Ly6C-expressing inflammatory monocytes exert a protective or a deleterious function during systemic infection. During murine systemic candidiasis, interruption of CCR2-dependent inflammatory monocyte trafficking into infected kidneys impaired fungal clearance and decreased murine survival. Depletion of CCR2-expressing cells led to uncontrolled fungal growth in the kidneys and brain and demonstrated an essential antifungal role for inflammatory monocytes and their tissue-resident derivatives in the first 48 hours post-infection. Adoptive transfer of purified inflammatory monocytes in depleted hosts reversed the defect in fungal clearance to a substantial extent, indicating a compartmentally- and temporally-restricted protective function that can be transferred to enhance systemic innate antifungal immunity.
The Journal of Infectious Diseases 08/2013; 209(1). DOI:10.1093/infdis/jit413 · 6.00 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Introduction Duchenne muscular dystrophy (DMD) is one of the most common forms of muscular dystrophy in humans. There is no cure for this deadly disease. Although magnetic resonance (MR) has emerged as a noninvasive tool capable of generating valuable information on tissue characteristics, clinical muscle MRI has been dependent on T1 and T2 weighted imaging to monitor inflammatory myopathies in patients with muscular dystrophy (1,2). These methods are useful because of their sensitivity to a wide range of mechanisms, but this generality means that they may not be able to identify specific cellular processes in the affected areas. Here we performed multi-parametric MRI to monitor treatment responses for mdx mice after adeno-associated virus (AAV) vector mediated gene therapy. We used quantitative T2, diffusion and magnetization transfer (MT) MRI to evaluate treatment effects for the AAV vector medicated gene therapy. Methods Eleven mdx mice and three normal C57Bl/6 mice were used for this study. Among 11 mdx mice, 7 were systemically treated with 10 13 vg of AAV virus containing a codon-optimized micro-dystrophin at 12 weeks of their ages. Multi-parametric 1 H MRI was carried out for mdx mice on a Bruker 14T Avance MR spectrometer (Bruker Corp., Billerica, MA). The high resolution MRI protocol includes scout imaging (gradient echo; TR (recycle delay)/TE (echo time) = 30/1.3 ms), planning for image planes (multislice RARE (rapid acquisition with refocused echoes): TR/TE = 668/4.5 ms), high resolution 2 dimensional imaging with thin slices (200 micron thick) (multi-slice RARE: TE/TE = 4000/6 ms) for muscle volume evaluation, multi-TE RARE imaging (TR/TE = 4000/ 6 ~ 75 ms, 12 echoes) for T2 measurements, magnetization transfer imaging, diffusion imaging with three b values of 0, 500 and 1000 s/mm 2 sequence (TR/TE = 4000/25 ms) and diffusion tensor imaging (DTI) with 4 shot echo planar imaging and b value of 1000 s/mm 2 (TR/TE = 4000/18 ms). Results and Discussion T2 and apparent diffusion coefficient (ADC) values were measured for both treated and untreated mdx mice and compared to those for normal mouse. Figure 1 shows T2 weighted images (TR/TE = 4 s/ 12.6 ms), T2 maps (TR/TE= 4 s/ 6.3 ~ 75.4 ms, 12 echoes), ADC maps acquired at 14T for untreated (A) and treated muscles (B, C) of mice with muscular dystrophy (mdx). T2 and ADC values were measured on tibialis anterior (TA) muscles (Fig. 1D). Three mdx mice (columns 2 -4 in Fig. 1) were systemically treated with adeno-associated virus (AAV) mediated microdystrophin genes while their litter mate control mdx mouse was untreated (1 st column in Fig. 1). T2 values of TA muscles were determined to show approximately 37% T2 decrease and up-to 16% ADC reduction on TA muscles for treated mdx mice compared to those for untreated control mouse. Also, T2 weighted (T2w) images and the T2 and ADC values for the treated mice are close to those acquired for normal mouse muscles (see Figure 2 for high resolution MR images for a normal mouse). The results demonstrate that the systemic micro-dystrophin treatments have high potential of an effective treatment approach for muscular dystrophy and that T2w, T2 and diffusion measurements would be important components in an MR protocol to monitor treatment responses. Figure 2 shows some results of T2 and DTI acquisitions conducted at 14T for in vivo hind-limb muscles of a normal C57BL/6 mouse. The corresponding T2 map and fractional anisotropy (FA) map were also generated by multi-slice multi-echo and DTI sequences, respectively. Conclusions Our results show T2, apparent diffusion coefficient (ADC) and MT ratio values would be potential MR markers to evaluate the treatment efficacy of gene therapy for muscular dystrophy. These noninvasive MR markers may be useful to timely monitor treatment responses for muscular dystrophy, which facilitates development of effective approaches to treat the deadly disease. References 1. Mercuri E, Jungbluth H, Muntoni F. Muscle imaging in clinical practice: diagnostic value of muscle magnetic resonance imaging in inherited neuromuscular disorders. Curr Opin Neurol 2005;18(5):526-537. 2. Mercuri E, Pichiecchio A, Allsop J, Messina S, Pane M, Muntoni F. Muscle MRI in inherited neuromuscular disorders: past, present, and future. J Magn Reson Imaging 2007;25(2):433-440.
International Society for Magnetic Resonance in Medicine, Salt Lake City, UT; 04/2013
[Show abstract][Hide abstract] ABSTRACT: The accumulation of genetic and epigenetic alterations mediates colorectal cancer (CRC) formation by deregulating key signaling pathways in cancer cells. In CRC, one of the most commonly inactivated signaling pathways is the transforming growth factor-beta (TGF-β) signaling pathway, which is often inactivated by mutations of TGF-β type II receptor (TGFBR2). Another commonly deregulated pathway in CRC is the phosphoinositide-3-kinase (PI3K)-AKT pathway. Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is an important negative regulator of PI3K-AKT signaling and is silenced in ∼30% of CRC. The combination of TGFBR2 inactivation and loss of PTEN is particularly common in microsatellite-unstable CRCs. Consequently, we determined in vivo if deregulation of these two pathways cooperates to affect CRC formation by analyzing tumors arising in mice that lack Tgfbr2 and/or Pten specifically in the intestinal epithelium. We found that lack of Tgfbr2 (Tgfbr2(IEKO)) alone is not sufficient for intestinal tumor formation and lack of Pten (Pten(IEKO)) alone had a weak effect on intestinal tumor induction. However, the combination of Tgfbr2 inactivation with Pten loss (Pten(IEKO);Tgfbr2(IEKO)) led to malignant tumors in both the small intestine and colon in 86% of the mice and to metastases in 8% of the tumor-bearing mice. Moreover, these tumors arose via a β-catenin-independent mechanism. Inactivation of TGF-β signaling and loss of Pten in the tumors led to increased cell proliferation, decreased apoptosis and decreased expression of cyclin-dependent kinase inhibitors. Thus, inactivation of TGF-β signaling and loss of PTEN cooperate to drive intestinal cancer formation and progression by suppressing cell cycle inhibitors.Oncogene advance online publication, 22 April 2013; doi:10.1038/onc.2013.102.
[Show abstract][Hide abstract] ABSTRACT: Fluorescence can be harnessed to monitor microbial fate and to investigate functional outcomes of individual microbial cell-host cell encounters at portals of entry in native tissue environments. We illustrate this concept by introducing fluorescent Aspergillus reporter (FLARE) conidia that simultaneously report phagocytic uptake and fungal viability during cellular interactions with the murine respiratory innate immune system. Our studies using FLARE conidia reveal stepwise and cell-type-specific requirements for CARD9 and Syk, transducers of C-type lectin receptor and integrin signals, in neutrophil recruitment, conidial uptake, and conidial killing in the lung. By achieving single-event resolution in defined leukocyte populations, the FLARE method enables host cell profiling on the basis of pathogen uptake and killing and may be extended to other pathogens in diverse model host organisms to query molecular, cellular, and pharmacologic mechanisms that shape host-microbe interactions.
[Show abstract][Hide abstract] ABSTRACT: Deregulated developmental processes in the cerebellum cause medulloblastoma, the most common pediatric brain malignancy. About
25 to 30% of cases are caused by mutations increasing the activity of the Sonic hedgehog (Shh) pathway, a critical mitogen
in cerebellar development. The proto-oncogene Smoothened (Smo) is a key transducer of the Shh pathway. Activating mutations in Smo that lead to constitutive activity of the Shh pathway have been identified in human medulloblastoma. To understand the developmental
and oncogenic effects of two closely positioned point mutations in Smo, we characterized NeuroD2-SmoA2 mice and compared them to NeuroD2-SmoA1 mice. While both SmoA1 and SmoA2 transgenes cause medulloblastoma with similar frequencies and timing, SmoA2 mice have severe aberrations in cerebellar development, whereas SmoA1 mice are largely normal during development. Intriguingly, neurologic function, as measured by specific tests, is normal in
the SmoA2 mice despite extensive cerebellar dysplasia. We demonstrate how two nearly contiguous point mutations in the same domain
of the encoded Smo protein can produce striking phenotypic differences in cerebellar development and organization in mice.
[Show abstract][Hide abstract] ABSTRACT: The Sonic Hedgehog (Shh) pathway drives a subset of medulloblastomas, a malignant neuroectodermal brain cancer, and other cancers. Small-molecule Shh pathway inhibitors have induced tumor regression in mice and patients with medulloblastoma; however, drug resistance rapidly emerges, in some cases via de novo mutation of the drug target. Here we assess the response and resistance mechanisms to the natural product derivative saridegib in an aggressive Shh-driven mouse medulloblastoma model. In this model, saridegib treatment induced tumor reduction and significantly prolonged survival. Furthermore, the effect of saridegib on tumor-initiating capacity was demonstrated by reduced tumor incidence, slower growth, and spontaneous tumor regression that occurred in allografts generated from previously treated autochthonous medulloblastomas compared with those from untreated donors. Saridegib, a known P-glycoprotein (Pgp) substrate, induced Pgp activity in treated tumors, which likely contributed to emergence of drug resistance. Unlike other Smoothened (Smo) inhibitors, the drug resistance was neither mutation-dependent nor Gli2 amplification-dependent, and saridegib was found to be active in cells with the D473H point mutation that rendered them resistant to another Smo inhibitor, GDC-0449. The fivefold increase in lifespan in mice treated with saridegib as a single agent compares favorably with both targeted and cytotoxic therapies. The absence of genetic mutations that confer resistance distinguishes saridegib from other Smo inhibitors.
Proceedings of the National Academy of Sciences 05/2012; 109(20):7859-64. DOI:10.1073/pnas.1114718109 · 9.67 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Colorectal cancer (CRC) remains a major cause of cancer mortality worldwide. Murine models have yielded critical insights
into CRC pathogenesis, but they often fail to recapitulate advanced-disease phenotypes, notably metastasis and chromosomal
instability (CIN). New models are thus needed to understand disease progression and to develop therapies. We sought to model
advanced CRC by inactivating two tumor suppressors that are mutated in human CRCs, the Fbw7 ubiquitin ligase and p53. Here
we report that Fbw7 deletion alters differentiation and proliferation in the gut epithelium and stabilizes oncogenic Fbw7
substrates, such as cyclin E and Myc. However, Fbw7 deletion does not cause tumorigenesis in the gut. In contrast, codeletion
of both Fbw7 and p53 causes highly penetrant, aggressive, and metastatic adenocarcinomas, and allografts derived from these
tumors form highly malignant adenocarcinomas. In vitro evidence indicates that Fbw7 ablation promotes genetic instability that is suppressed by p53, and we show that most Fbw7−/−; p53−/− carcinomas exhibit a CIN+ phenotype. We conclude that Fbw7 and p53 synergistically suppress adenocarcinomas that mimic advanced human CRC with respect
to histopathology, metastasis, and CIN. This model thus represents a novel tool for studies of advanced CRC as well as carcinogenesis
associated with ubiquitin pathway mutations.
[Show abstract][Hide abstract] ABSTRACT: Hepatocellular carcinoma (HCC) results from the accumulation of deregulated tumor suppressor genes and/or oncogenes in hepatocytes. Inactivation of TP53 and inhibition of transforming growth factor-beta (TGF-β) signaling are among the most common molecular events in human liver cancers. Thus, we assessed whether inactivation of TGF-β signaling, by deletion of the TGF-β receptor, type II (Tgfbr2), cooperates with Trp53 loss to drive HCC formation. Albumin-cre transgenic mice were crossed with floxed Trp53 and/or floxed Tgfbr2 mice to generate mice lacking p53 and/or Tgfbr2 in the liver. Deletion of Trp53 alone (Trp53(KO) ) resulted in liver tumors in approximately 41% of mice by 10 months of age, whereas inactivation of Tgfbr2 alone (Tgfbr2(KO) ) did not induce liver tumors. Surprisingly, deletion of Tgfbr2 in the setting of p53 loss (Trp53(KO) ;Tgfbr2(KO) ) decreased the frequency of mice with liver tumors to around 17% and delayed the age of tumor onset. Interestingly, Trp53(KO) and Trp53(KO) ;Tgfbr2(KO) mice develop both HCC and cholangiocarcinomas, suggesting that loss of p53, independent of TGF-β, may affect liver tumor formation through effects on a common liver stem cell population. Assessment of potential mechanisms through which TGF-β signaling may promote liver tumor formation in the setting of p53 loss revealed a subset of Trp53(KO) tumors that express increased levels of alpha-fetoprotein. Furthermore, tumors from Trp53(KO) mice express increased TGF-β1 levels compared with tumors from Trp53(KO) ;Tgfbr2(KO) mice. Increased phosphorylated Smad3 and ERK1/2 expression was also detected in the tumors from Trp53(KO) mice and correlated with increased expression of the TGF-β responsive genes, Pai1 and Ctgf. CONCLUSION: TGF-β signaling paradoxically promotes the formation of liver tumors that arise in the setting of p53 inactivation.
[Show abstract][Hide abstract] ABSTRACT: Recent advances in nanotechnology have led to the development of biocompatible nanoparticles for in vivo molecular imaging and targeted therapy. Many nanoparticles have undesirable tissue distribution or unacceptably low serum half-lives. Pharmacokinetic (PK) and biodistribution studies can help inform decisions determining particle size, coatings, or other features early in nanoparticle development. Unfortunately, these studies are rarely done in a timely fashion because many nanotechnology labs lack the resources and expertise to synthesize radioactive nanoparticles and evaluate them in mice.
To address this problem, we developed an economical, radioactivity-free method for assessing serum half-life and tissue distribution of nanoparticles in mice. Iron oxide nanoparticles coated with chitosan and polyethylene glycol that utilize chlorotoxin as a targeting molecule have a serum half-life of 7-8 hours and the particles remain stable for extended periods of time in physiologic fluids and in vivo. Nanoparticles preferentially distribute to spleen and liver, presumably due to reticuloendothelial uptake. Other organs have very low levels of nanoparticles, which is ideal for imaging most cancers in the future. No acute toxicity was attributed to the nanoparticles.
We report here a simple near-infrared fluorescence based methodology to assess PK properties of nanoparticles in order to integrate pharmacokinetic data into early nanoparticle design and synthesis. The nanoparticles tested demonstrate properties that are excellent for future clinical imaging strategies and potentially suitable for targeted therapy.
PLoS ONE 03/2010; 5(3):e9536. DOI:10.1371/journal.pone.0009536 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Reduced expression of the CDK inhibitor p27(Kip1) (p27) in human lung cancer correlates with tumor aggressiveness and poor prognosis. However, the regulation of p27 expression and the role of p27 during lung cancer are poorly understood. Urethane-induced lung tumors in mice frequently harbor mutations in the Kras oncogene, and in this study, we use this model to address the regulation of p27 during tumorigenesis. The Ras effector Akt is known to regulate p27 mRNA abundance by phosphorylating and inactivating the FOXO transcription factors. Phosphorylated Akt and FOXO proteins were both increased in lung tumors, correlating with a reduction in p27 mRNA transcript. Akt also directly phosphorylates p27 and regulates its nuclear/cytoplasmic localization. Tumors showed a reduced nuclear/cytoplasmic ratio of p27 protein, together with an increase in phosphorylated Thr197 p27 in the cytoplasmic pool. Treatment of lung tumor-bearing mice with the phosphoinositol-3 kinase inhibitor LY294002 induced a rapid decrease in phosphorylated Akt and phosphorylated p27, concomitant with an increase in nuclear p27. Germline p27 deficiency accelerated both the growth and malignant progression of urethane-induced lung tumors, and did so in a cell autonomous manner, confirming a causal role of p27 in tumor suppression. These results show that p27 is a potent barrier to the growth and malignant progression of Kras-initiated lung tumors. Further, the reduction of nuclear p27 in tumors is mediated by oncogene signaling pathways, which can be reversed by pharmacological agents.
[Show abstract][Hide abstract] ABSTRACT: During colorectal cancer pathogenesis, mutations and epigenetic events cause neoplastic behavior in epithelial cells by deregulating the Wnt, Ras-Raf-extracellular signal-regulated kinase (ERK), and transforming growth factor (TGF)-beta-signaling pathways, among others. The TGF-beta-signaling pathway is often inactivated in colon cancer cells by mutations in the gene encoding the TGF-beta receptor TGFBR2. The RAS-RAF-ERK pathway is frequently up-regulated in colon cancer via mutational activation of KRAS or BRAF. We assessed how these pathways interact in vivo and affect formation of colorectal tumors.
We analyzed intestinal tumors that arose in mice that express an oncogenic (active) form of Kras and that have Tgfbr2 inactivations-2 common molecular events observed in human colorectal tumors. LSL-KrasG12D mice were crossed with Villin-Cre;Tgfbr2E2flx/E2flx mice, which do not express Tgfbr2 in the intestinal epithelium.
Neither inactivation of Tgfbr2 nor expression of oncogenic Kras alone was sufficient to induce formation of intestinal neoplasms. Histologic abnormalities arose in mice that expressed Kras, but only the combination of Tgfbr2 inactivation and Kras activation led to intestinal neoplasms and metastases. The cancers arose via a beta-catenin-independent mechanism; the epidermal growth factor-signaling pathway was also activated. Cells in the resulting tumors proliferated at higher rates, expressed decreased levels of p15, and expressed increased levels of cyclin D1 and cdk4, compared with control cells.
A combination of inactivation of the TGF-beta-signaling pathway and expression of oncogenic Kras leads to formation of invasive intestinal neoplasms through a beta-catenin-independent pathway; these adenocarcinomas have the capacity to metastasize.
[Show abstract][Hide abstract] ABSTRACT: Insulin-like growth factor-I (IGF-I) is a polypeptide hormone that can influence growth, differentiation, and survival of cells expressing the cognate type 1 receptor (IGF-IR). To better understand cell autonomous IGF-IR signaling in the epithelial compartment of the prostate gland, we generated a conditional (Cre/loxP) prostate-specific IGF-IR knockout mouse model. In contrast to epidemiologic studies that established a correlation between elevated serum IGF-I and the risk of developing prostate cancer, we show that abrogation of IGF-IR expression in the dorsal and lateral prostate could activate extracellular signal-regulated kinase 1/2 signaling and cause cell autonomous proliferation and hyperplasia. Moreover, persistent loss of IGF-IR expression in dorsal and ventral lobes induced p53-regulated apoptosis and cellular senescence rescue programs, predicting that titration of IGF-IR signaling might facilitate growth of tumors with compromised p53 activity. Therefore, we crossed the mice carrying the prostate-specific IGF-IR knockout alleles into the transgenic adenocarcinoma of the mouse prostate model that is driven, in part, by T antigen-mediated functional inactivation of p53. Consistent with our prediction, prostate epithelial-specific deletion of IGF-IR accelerated the emergence of aggressive prostate cancer when p53 activity was compromised. Collectively, these data support a critical role for IGF-IR signaling in prostate tumorigenesis and identify an important IGF-IR-dependent growth control mechanism.
Cancer Research 06/2008; 68(9):3495-504. DOI:10.1158/0008-5472.CAN-07-6531 · 9.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Toward the goal of generating a mouse medulloblastoma model with increased tumor incidence, we developed a homozygous version of our ND2:SmoA1 model. Medulloblastomas form in 94% of homozygous Smo/Smo mice by 2 months of age. Tumor formation is, thus, predictable by age, before the symptomatic appearance of larger lesions. This high incidence and early onset of tumors is ideal for preclinical studies because mice can be enrolled before symptom onset and with a greater latency period before late-stage disease. Smo/Smo tumors also display leptomeningeal dissemination of neoplastic cells to the brain and spine, which occurs in many human cases. Despite an extended proliferation of granule neuron precursors (GNP) in the postnatal external granular layer (EGL), the internal granular layer formed normally in Smo/Smo mice and tumor formation occurred only in localized foci on the superficial surface of the molecular layer. Thus, tumor formation is not simply the result of over proliferation of GNPs within the EGL. Moreover, Smo/Smo medulloblastomas were transplantable and serially passaged in vivo, demonstrating the aggressiveness of tumor cells and their transformation beyond a hyperplastic state. The Smo/Smo model is the first mouse medulloblastoma model to show leptomeningeal spread. The adherence to human pathology, high incidence, and early onset of tumors thus make Smo/Smo mice an efficient model for preclinical studies.
Cancer Research 04/2008; 68(6):1768-76. DOI:10.1158/0008-5472.CAN-07-5092 · 9.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Toll-like receptors and the β-glucan receptor, dectin-1, mediate macrophage inflammatory responses to Aspergillus fumigatus through MyD88-dependent and -independent signaling mechanisms; however, pulmonary inflammatory responses in MyD88-deficient
mice challenged with A. fumigatus are poorly defined. The role of MyD88 signaling in early pulmonary inflammation and fungal clearance was evaluated in C57BL/6J
wild-type (WT) and MyD88-deficient (MyD88−/−) mice. Early (<48 h) after infection, MyD88−/− mice had higher fungal burdens than those of WT mice, although fungal burdens rapidly declined (>72 h) in both. MyD88−/− mice had less consolidated inflammation, with fewer NK cells, in lung tissue early (24 h) after infection than did WT mice.
At the latter time point, MyD88−/− mouse lungs were characterized by a large amount of necrotic cellular debris and fibrin, while WT lungs had organized inflammation.
Although there were equivalent numbers of macrophages in WT and MyD88−/− mouse lung tissues, MyD88−/− cells demonstrated delayed uptake of green fluorescent protein-expressing A. fumigatus (GFP-Af293); histologically, MyD88−/− mouse lungs had more hyphal invasion of terminal airways and vessels, the appearance of bronchiolar epithelial cell necrosis,
and necrotizing vasculitis. MyD88−/− lung homogenates contained comparatively decreased amounts of interleukin-1β (IL-1β), IL-6, KC, and gamma interferon and
paradoxically increased amounts of tumor necrosis factor alpha and macrophage inflammatory protein 1α. These data indicate
that the MyD88-dependent pathway mediates acute pulmonary fungal clearance, inflammation, and tissue injury very early after
infection. Resolution of abnormalities within a 3-day window demonstrates the importance of redundant signaling pathways in
mediating pulmonary inflammatory responses to fungi.
Infection and immunity 03/2008; 76(3):952-8. DOI:10.1128/IAI.00927-07 · 3.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Hemoproteins are critical for the function and integrity of aerobic cells. However, free heme is toxic. Therefore, cells must
balance heme synthesis with its use. We previously demonstrated that the feline leukemia virus, subgroup C, receptor (FLVCR)
exports cytoplasmic heme. Here, we show that FLVCR-null mice lack definitive erythropoiesis, have craniofacial and limb deformities
resembling those of patients with Diamond-Blackfan anemia, and die in midgestation. Mice with FLVCR that is deleted neonatally
develop a severe macrocytic anemia with proerythroblast maturation arrest, which suggests that erythroid precursors export
excess heme to ensure survival. We further demonstrate that FLVCR mediates heme export from macrophages that ingest senescent
red cells and regulates hepatic iron. Thus, the trafficking of heme, and not just elemental iron, facilitates erythropoiesis
and systemic iron balance.