PTEN functions to 'prioritize' chemotactic cues and prevent 'distraction' in migrating neutrophils.

Neutrophils encounter and 'prioritize' many chemoattractants in their pursuit of bacteria. Here we tested the possibility that the phosphatase PTEN is responsible for the prioritization of chemoattractants. Neutrophils induced chemotaxis by two separate pathways, the phosphatidylinositol-3-OH kinase (PI(3)K) phosphatase and tensin homolog (PTEN) pathway, and the p38 mitogen-activated protein kinase pathway, with the p38 pathway dominating over the PI(3)K pathway. Pten(-/-) neutrophils could not prioritize chemoattractants and were 'distracted' by chemokines when moving toward bacterial chemoattractants. In opposing gradients, PTEN became distributed throughout the cell circumference, which inhibited all PI(3)K activity, thus permitting 'preferential' migration toward bacterial products via phospholipase A(2) and p38. Such prioritization was defective in Pten(-/-) neutrophils, which resulted in defective bacterial clearance in vivo. Our data identify a PTEN-dependent mechanism in neutrophils to prioritize, 'triage' and integrate responses to multiple chemotactic cues.

Osteo-chondroprogenitor-specific deletion of the selenocysteine tRNA gene, Trsp, leads to chondronecrosis and abnormal skeletal development: a putative model for Kashin-Beck disease.

Kashin-Beck disease, a syndrome characterized by short stature, skeletal deformities, and arthropathy of multiple joints, is highly prevalent in specific regions of Asia. The disease has been postulated to result from a combination of different environmental factors, including contamination of barley by mold mycotoxins, iodine deficiency, presence of humic substances in drinking water, and, importantly, deficiency of selenium. This multifunctional trace element, in the form of selenocysteine, is essential for normal selenoprotein function, including attenuation of excessive oxidative stress, and for the control of redox-sensitive molecules involved in cell growth and differentiation. To investigate the effects of skeletal selenoprotein deficiency, a Cre recombinase transgenic mouse line was used to trigger Trsp gene deletions in osteo-chondroprogenitors. Trsp encodes selenocysteine tRNA([Ser]Sec), required for the incorporation of selenocysteine residues into selenoproteins. The mutant mice exhibited growth retardation, epiphyseal growth plate abnormalities, and delayed skeletal ossification, as well as marked chondronecrosis of articular, auricular, and tracheal cartilages. Phenotypically, the mice thus replicated a number of the pathological features of Kashin-Beck disease, supporting the notion that selenium deficiency is important to the development of this syndrome.

Simple and robust polymer-based sensor for rapid cancer detection using serum.

We report a polymer-based sensor that rapidly detects cancer based on changes in serum protein levels. Using three ratiometric fluorescence outputs, this simple system identifies early stage and metastatic lung cancer with a high level of accuracy exceeding many biomarker-based assays, making it an attractive strategy for point-of-care testing.

DNA mismatch repair deficiency accelerates lung neoplasm development in K-ras(LA1/+) mice: a brief report.

Inherited as well as acquired deficiencies in specific DNA mismatch repair (MMR) components are associated with the development of a wide range of benign and malignant neoplasms. Loss of key members such as MSH2 and MLH1 severely cripples the ability of the cell to recognize and correct such lesions as base:base mismatches and replicative DNA polymerase errors such as slippages at repetitive sequences. Genomic instability resulting from MMR deficiency not only predisposes cells to malignant transformation but may also promote tumor progression. To test the latter, we interbred Msh2(-/-) mice with the K-ras(LA1/+) transgenic line that spontaneously develops a range of premalignant and malignant lung lesions. Compared to K-ras(LA1/+) mice, K-ras(LA1/+); Msh2(-/-) mice developed lung adenomas and adenocarcinomas at an increased frequency and also demonstrated evidence of accelerated adenocarcinoma growth. Since MMR defects have been identified in some human lung cancers, the mutant mice may not only be of preclinical utility but they will also be useful in identifying gene alterations able to act in concert with Kras mutants to promote tumor progression.

Characterization of a murine model of metastatic human non-small cell lung cancer and effect of CXCR4 inhibition on the growth of metastases.

Despite successful preclinical testing carried out through the use of subcutaneous xenografted tumors, many anti-cancer agents have gone on to fail in human trials. One potential factor accounting for this discrepancy may relate to the inadequacy of the commonly employed preclinical models to recapitulate the human disease, particularly when it comes to discovery of agents that are effective against advanced disease. Herein, we report the characterization of a NSCLC model and an exploration of the impact that a CXCR4 inhibitor, AMD3100, had on NCI-H1299-derived metastasis. These cells express a variety of metastasis-promoting factors, hence we selected them for a study of their metastatic colonization potential. To accomplish this, luciferase-expressing H1299 (H1299-luc2) cells were inoculated into athymic mice via the intracardiac route. This strategy produced adrenal, bone, ovarian, and pancreatic metastases, sites commonly involved in human metastatic NSCLC. Notably, micro-computed tomography and histological evaluation of the skeletal lesions revealed the presence of extensive osteolysis. To investigate the potential role of CXCR4 in mediating metastatic colonization of tissues, AMD3100 was administered to mice inoculated with H1299-luc2 cells. While this treatment did not appreciably alter the frequency of metastatic colonization, it was able to slow the growth of macrometastases. This model, recapitulating some of the events seen in late-stage human NSCLC, may prove useful in the evaluation of new therapies targeting metastatic disease.

Mind the gap: genetic manipulation of basicranial growth within synchondroses modulates calvarial and facial shape in mice through epigenetic interactions.

Phenotypic integration patterns in the mammalian skull have long been a focus of intense interest as a result of their suspected influence on the trajectory of hominid evolution. Here we test the hypothesis that perturbation of cartilage growth, which directly affects only the chondrocranium during development, will produce coordinated shape changes in the adult calvarium and face regardless of mechanism. Using two murine models of cartilage undergrowth that target two very different mechanisms, we show that strong reduction in cartilage growth produces a short, wide, and more flexed cranial base. This in turn produces a short, wide face in both models. Cranial base and face are already correlated early in ontogeny, and the relationship between these modules gains structure through postnatal growth and development. These results provide further evidence that there exist physical interactions between developing parts of the phenotype that produce variation at a distance from the actual locus upon which a particular selective pressure is acting. Phenotypic changes observed over the course of evolution may not all require adaptationist explanations; rather, it is likely that a substantial portion of observed phenotypic variation over the history of a clade is not directly adaptive but rather a secondary consequence of some local response to selection.

DMXAA causes tumor site-specific vascular disruption in murine non-small cell lung cancer, and like the endogenous non-canonical cyclic dinucleotide STING agonist, 2'3'-cGAMP, induces M2 macrophage repolarization.

The vascular disrupting agent 5,6-dimethylxanthenone-4-acetic acid (DMXAA), a murine agonist of the stimulator of interferon genes (STING), appears to target the tumor vasculature primarily as a result of stimulating pro-inflammatory cytokine production from tumor-associated macrophages (TAMs). Since there were relatively few reports of DMXAA effects in genetically-engineered mutant mice (GEMM), and models of non-small cell lung cancer (NSCLC) in particular, we examined both the effectiveness and macrophage dependence of DMXAA in various NSCLC models. The DMXAA responses of primary adenocarcinomas in K-rasLA1/+ transgenic mice, as well as syngeneic subcutaneous and metastatic tumors, generated by a p53R172HΔg/+; K-rasLA1/+ NSCLC line (344SQ-ELuc), were assessed both by in vivo bioluminescence imaging as well as by histopathology. Macrophage-dependence of DMXAA effects was explored by clodronate liposome-mediated TAM depletion. Furthermore, a comparison of the vascular structure between subcutaneous tumors and metastases was carried out using micro-computed tomography (micro-CT). Interestingly, in contrast to the characteristic hemorrhagic necrosis produced by DMXAA in 344SQ-ELuc subcutaneous tumors, this agent failed to cause hemorrhagic necrosis of either 344SQ-ELuc-derived metastases or autochthonous K-rasLA1/+ NSCLCs. In addition, we found that clodronate liposome-mediated depletion of TAMs in 344SQ-ELuc subcutaneous tumors led to non-hemorrhagic necrosis due to tumor feeding-vessel occlusion. Since NSCLC were comprised exclusively of TAMs with anti-inflammatory M2-like phenotype, the ability of DMXAA to re-educate M2-polarized macrophages was examined. Using various macrophage phenotypic markers, we found that the STING agonists, DMXAA and the non-canonical endogenous cyclic dinucleotide, 2'3'-cGAMP, were both capable of re-educating M2 cells towards an M1 phenotype. Our findings demonstrate that the choice of preclinical model and the anatomical site of a tumor can determine the vascular disrupting effectiveness of DMXAA, and they also support the idea of STING agonists having therapeutic utility as TAM repolarizing agents.

Selumetinib produces a central core of apoptosis in breast cancer bone metastases in mice.

Bone is a common site for metastatic colonization in patients with breast cancer, hence the importance of identifying new treatments for this disease. Preclinical studies of bone metastases have commonly employed MDA-MB-231 cells that possess an activated KRAS allele. While activating RAS mutations are relatively rare in human breast cancer, increased RAS-RAF-MEK pathway activity is common in high-grade breast cancers. To study the consequences of MEK inhibition on bone metastases stemming from the intra-cardiac injection of luciferase-expressing MDA-MB-231 cells in mice, we used the MEK inhibitor AZD6244 (Selumetinib). We found that AZD6244 treatment caused decreased tumor bioluminescence that was associated with cavitation of the bone metastases, owing to apoptosis of cells specifically within the central region of the bone lesions. Hypothesizing that the latter effect was due to the increased sensitivity of poorly perfused regions to pro-apoptotic stimuli, we found that the combination of serum deprivation and AZD6244 led to dramatic induction pf MDA-MB-231 apoptosis in vitro. Our results suggest that MEK inhibition may be a strategy for triggering cell death within the hypoperfused, oxygen and nutrient poor regions of tumors with activated RAS alleles.

Micro-CT evaluation of bone defects: applications to osteolytic bone metastases, bone cysts, and fracture.

Bone defects can occur in various forms and present challenges to performing a standard micro-CT evaluation of bone quality because most measures are suited to homogeneous structures rather than ones with spatially focal abnormalities. Such defects are commonly associated with pain and fragility. Research involving bone defects requires quantitative approaches to be developed if micro-CT is to be employed. In this study, we demonstrate that measures of inter-microarchitectural bone spacing are sensitive to the presence of focal defects in the proximal tibia of two distinctly different mouse models: a burr-hole model for fracture healing research, and a model of osteolytic bone metastases. In these models, the cortical and trabecular bone compartments were both affected by the defect and were, therefore, evaluated as a single unit to avoid splitting the defects into multiple analysis regions. The burr-hole defect increased mean spacing (Sp) by 27.6%, spacing standard deviation (SpSD) by 113%, and maximum spacing (Spmax) by 72.8%. Regression modeling revealed SpSD (ß=0.974, p<0.0001) to be a significant predictor of the defect volume (R(2)=0.949) and Spmax (ß=0.712, p<0.0001) and SpSD (ß=0.271, p=0.022) to be significant predictors of the defect diameter (R(2)=0.954). In the mice with osteolytic bone metastases, spacing parameters followed similar patterns of change as reflected by other imaging technologies, specifically bioluminescence data which is indicative of tumor burden. These data highlight the sensitivity of spacing measurements to bone architectural abnormalities from 3D micro-CT data and provide a tool for quantitative evaluation of defects within a bone.

Quantitative ex-vivo micro-computed tomographic imaging of blood vessels and necrotic regions within tumors.

Techniques for visualizing and quantifying the microvasculature of tumors are essential not only for studying angiogenic processes but also for monitoring the effects of anti-angiogenic treatments. Given the relatively limited information that can be gleaned from conventional 2-D histological analyses, there has been considerable interest in methods that enable the 3-D assessment of the vasculature. To this end, we employed a polymerizing intravascular contrast medium (Microfil) and micro-computed tomography (micro-CT) in combination with a maximal spheres direct 3-D analysis method to visualize and quantify ex-vivo vessel structural features, and to define regions of hypoperfusion within tumors that would be indicative of necrosis. Employing these techniques we quantified the effects of a vascular disrupting agent on the tumor vasculature. The methods described herein for quantifying whole tumor vascularity represent a significant advance in the 3-D study of tumor angiogenesis and evaluation of novel therapeutics, and will also find potential application in other fields where quantification of blood vessel structure and necrosis are important outcome parameters.

The lysyl oxidase inhibitor, beta-aminopropionitrile, diminishes the metastatic colonization potential of circulating breast cancer cells.

Lysyl oxidase (LOX), an extracellular matrix remodeling enzyme, appears to have a role in promoting breast cancer cell motility and invasiveness. In addition, increased LOX expression has been correlated with decreases in both metastases-free, and overall survival in breast cancer patients. With this background, we studied the ability of beta-aminopropionitrile (BAPN), an irreversible inhibitor of LOX, to regulate the metastatic colonization potential of the human breast cancer cell line, MDA-MB-231. BAPN was administered daily to mice starting either 1 day prior, on the same day as, or 7 days after intracardiac injection of luciferase expressing MDA-MB-231-Luc2 cells. Development of metastases was monitored by in vivo bioluminescence imaging, and tumor-induced osteolysis was assessed by micro-computed tomography (microCT). We found that BAPN administration was able to reduce the frequency of metastases. Thus, when BAPN treatment was initiated the day before, or on the same day as the intra-cardiac injection of tumor cells, the number of metastases was decreased by 44%, and 27%, and whole-body photon emission rates (reflective of total tumor burden) were diminished by 78%, and 45%, respectively. In contrast, BAPN had no effect on the growth of established metastases. Our findings suggest that LOX activity is required during extravasation and/or initial tissue colonization by circulating MDA-MB-231 cells, lending support to the idea that LOX inhibition might be useful in metastasis prevention.