Significant downregulation of platelet gene expression in metastatic lung cancer.

Platelets play a major role in the metastatic dissemination of tumor cells in vivo . Recent evidence reveals megakaryocyte-derived platelet pre-mRNA is spliced to mRNA and then translated into functional proteins in response to external stimulation. Employing a human lung cancer model, we hypothesized a subset of megakaryocyte/platelet genes exists that are significantly over or underexpressed in metastasis compared with noncancer. Microarray analysis employing platelet mRNA followed by unsupervised hierarchical clustering revealed an expression profile that includes decreased expression of 197 of the 200 platelet genes with the most altered expression (p < 1.0 × 10(-4)). Among the 608 splicing events identified between the metastasis and negative control groups, 33 highly variable genes were identified with between 3 and 13 splicing events each. In conclusion, this preliminary study reveals a platelet-based gene expression signature that differentiates metastatic lung cancer from negative controls on the basis of decreased expression of 197 of the 200 genes with the most altered expression levels. Further study may yield a prognostic tool for future metastasis among subsets of early stage lung cancer patients.

Prostacyclin prevents pulmonary endothelial cell apoptosis induced by cigarette smoke.

RATIONALE: Impaired endothelial cell-dependent vasodilation, inflammation, apoptosis, and proliferation are manifestations of endothelial dysfunction in chronic obstructive pulmonary disease (COPD). Prostacyclin (PGI(2)) is a major product of the cyclooxygenase pathway with potent vasodilatory and antimitogenic properties and may be relevant to endothelial dysfunction in COPD. OBJECTIVES: To determine if PGI(2) expression is altered in smoking-related lung disease and if it may be protective in COPD-associated endothelial dysfunction. METHODS: We evaluated, by immunohistochemistry, Western blotting, and polymerase chain reaction, human emphysema tissue compared with normal tissue for expression of prostacyclin synthase (PGI(2)S). We examined the effects of cigarette smoke extract (CSE) and aldehyde components on eicosanoid expression in primary human pulmonary microvascular endothelial cells. Finally, we used a murine model of lung-specific PGI(2)S overexpression and in vitro studies to determine if PGI(2) expression has protective effects on cigarette smoke-induced endothelial apoptosis. MEASUREMENTS AND MAIN RESULTS: Human emphysema lung tissue exhibited lower PGI(2)S expression within the pulmonary endothelium than in normal lung. In vitro studies demonstrated that CSE, and in particular the alpha,beta unsaturated aldehyde acrolein, suppressed PGI(2)S gene expression, whereas CSE significantly induced the upstream mediators COX-2 and cytosolic phospholipase A2 in human pulmonary microvascular endothelial cells. Mice with lung-specific PGI(2)S overexpression exhibited less endothelial apoptosis after chronic smoke exposure. In vitro, iloprost exhibited protective effects on CSE-induced apoptosis. CONCLUSIONS: PGI(2) has protective effects in the pulmonary vasculature after acute and chronic cigarette smoke exposure. An imbalance in eicosanoid expression may be important to COPD-associated endothelial dysfunction.

Attenuation of glucocorticoid functions in an Anx-A1-/- cell line.

The Ca(2+)- and phospholipid-binding protein Anx-A1 (annexin 1; lipocortin 1) has been described both as an inhibitor of phospholipase A(2) (PLA(2)) activity and as a mediator of glucocorticoid-regulated cell growth and eicosanoid generation. Here we show that, when compared with Anx-A1(+/+) cells, lung fibroblast cell lines derived from the Anx-A1(-/-) mouse exhibit an altered morphology characterized by a spindle-shaped appearance and an accumulation of intracellular organelles. Unlike their wild-type counterparts, Anx-A1(-/-) cells also overexpress cyclo-oxygenase 2 (COX 2), cytosolic PLA(2) and secretory PLA(2) and in response to fetal calf serum, exhibit an exaggerated release of eicosanoids, which is insensitive to dexamethasone (10(-8)- 10(-6) M) inhibition. Proliferation and serum-induced progression of Anx-A1(+/+) cells from G(0)/G(1) into S phase, and the associated expression of extracellular signal-regulated kinase 2 (ERK2), cyclin-dependent kinase 4 (cdk4) and COX 2, is strongly inhibited by dexamethasone, whereas Anx-A1(-/-) cells are refractory to the drug. Loss of the response to dexamethasone in Anx-A1(-/-) cells occurs against a background of no apparent change in glucocorticoid receptor expression or sensitivity to non-steroidal anti-inflammatory drugs. Taken together, these observations suggest strongly that Anx-A1 functions as an inhibitor of signal-transduction pathways that lead to cell proliferation and may help to explain how glucocorticoids regulate these processes.