Thomas J. Gross

FDG-PET imaging and the diagnosis of non-small cell lung cancer in a region of high histoplasmosis prevalence

STUDY OBJECTIVEnDetermine the sensitivity and specificity of [F-18]-fluorine-2-deoxy-D-glucose positron emission tomography (FDG-PET) in differentiating non-small cell lung cancer (NSCLC) from benign solitary pulmonary nodules (SPNs) in a region with a high endemic rate of histoplamosis.nnnDESIGNnProspective, clinical study.nnnSETTINGnUniversity, tertiary referral hospital in the upper Mississippi River valley.nnnPATIENTSnNinety patients with SPNs.nnnINTERVENTIONSnIndependent interpretation of FDG-PET imaging, computed tomography and pathologic evaluation of the SPNs.nnnMEASUREMENTS AND RESULTSnTo detect malignant SPNs, FDG-PET imaging had a sensitivity of 93%, a specificity of 40%, a positive predictive value (PPV) of 88% and a negative predictive value (NPV) of 55%.nnnCONCLUSIONSnIn a region with a high prevalence of pulmonary fungal infection, FDG-PET is sensitive but has a low specificity and NPV for identifying NSCLC. In our study cohort, FDG-PET does not appear to reduce the need for SPN biopsies.

Cigarette Smoking Decreases Global MicroRNA Expression in Human Alveolar Macrophages

Human alveolar macrophages are critical components of the innate immune system. Cigarette smoking-induced changes in alveolar macrophage gene expression are linked to reduced resistance to pulmonary infections and to the development of emphysema/COPD. We hypothesized that microRNAs (miRNAs) could control, in part, the unique messenger RNA (mRNA) expression profiles found in alveolar macrophages of cigarette smokers. Activation of macrophages with different stimuli in vitro leads to a diverse range of M1 (inflammatory) and M2 (anti-inflammatory) polarized phenotypes that are thought to mimic activated macrophages in distinct tissue environments. Microarray mRNA data indicated that smoking promoted an “inverse” M1 mRNA expression program, defined by decreased expression of M1-induced transcripts and increased expression of M1-repressed transcripts with few changes in M2-regulated transcripts. RT-PCR arrays identified altered expression of many miRNAs in alveolar macrophages of smokers and a decrease in global miRNA abundance. Stratification of human subjects suggested that the magnitude of the global decrease in miRNA abundance was associated with smoking history. We found that many of the miRNAs with reduced expression in alveolar macrophages of smokers were predicted to target mRNAs upregulated in alveolar macrophages of smokers. For example, miR-452 is predicted to target the transcript encoding MMP12, an important effector of smoking-related diseases. Experimental antagonism of miR-452 in differentiated monocytic cells resulted in increased expression of MMP12. The comprehensive mRNA and miRNA expression profiles described here provide insight into gene expression regulation that may underlie the adverse effects cigarette smoking has on alveolar macrophages.

Human neutrophil elastase abolishes interleukin-8 chemotactic activity

A large body of literature supports the role of interleukin‐8 (IL‐8) in inflammatory lung disease. Numerous factors induce the local synthesis and secretion of this potent chemokine leading to the recruitment and activation of polymorphonuclear leukocytes. However, little is currently known about the fate of IL‐8 secreted at sites of inflammatory injury. We have found that incubation of recombinant human IL‐8 with purified human neutrophil elastase (HNE) results in the loss of IL‐8 chemotactic activity in a dose‐ and time‐dependent fashion. This loss in bioactivity is accompanied by a similar loss of IL‐8 immunoreactivity. Western blot analysis revealed that IL‐8 chemotactic activity is lost by proteolysis of the parent molecule into undetectable small fragments. The terminal digestion of IL‐8 was specific to HNE as no loss of bioactivity was observed with equimolar concentrations of the serine proteases urokinase, plasmin, thrombin, or cathepsin G. This effect on chemotactic activity is not limited to recombinant IL‐8 because HNE also digested IL‐8 secreted by human monocytes. HNE‐mediated proteolysis offers a novel mechanism for down‐regulating the inflammatory cascade initiated by IL‐8. J. Leukoc. Biol. 61: 361–366; 1997.

Coordinated DNA methylation and gene expression changes in smoker alveolar macrophages: specific effects on VEGF receptor 1 expression

Cigarette smoking is implicated in numerous diseases, including emphysema and lung cancer. The clinical expression of lung disease in smokers is not well explained by currently defined variations in gene expression or simple differences in smoking exposure. Alveolar macrophages play a critical role in the inflammation and remodeling of the lung parenchyma in smoking‐related lung disease. Significant gene expression changes in alveolar macrophages from smokers have been identified. However, the mechanism for these changes remains unknown. One potential mechanism for smoking‐altered gene expression is via changes in cytosine methylation in DNA regions proximal to gene‐coding sequences. In this study, alveolar macrophage DNA from heavy smokers and never smokers was isolated and methylation status at 25,000 loci determined. We found differential methylation in genes from immune‐system and inflammatory pathways. Analysis of matching gene expression data demonstrated a parallel enrichment for changes in immune‐system and inflammatory pathways. A significant number of genes with smoking‐altered mRNA expression had inverse changes in methylation status. One gene highlighted by this data was the FLT1, and further studies found particular up‐regulation of a splice variant encoding a soluble inhibitory form of the receptor. In conclusion, chronic cigarette smoke exposure altered DNA methylation in specific gene promoter regions in human alveolar macrophages.