miR-30 as a tumor suppressor connects EGF/Src signal to ERG and EMT.

Src tyrosine kinase (Src) is implicated in the development of bone metastasis and castration resistance of prostate cancer. Src inhibitors are currently being tested in clinical trials for such diseases. Understanding the molecular and cellular actions of Src inhibitors holds the key to future improvement of this line of therapy. Here we describe the microRNA expression profiles modulated by two Src inhibitors and demonstrate that the miR-30 family members are the most prominently induced species. Consistent with its tumor suppressor role, miR-30 is downmodulated by oncogenic signals such as epidermal growth factor (EGF) and hepatocyte growth factor, and is generally underexpressed in prostate cancer specimens. A number of epithelial-to-mesenchymal transition (EMT)-associated genes are predicted targets of miR-30. Among these genes the Ets-related gene (ERG) is the most frequently overexpressed oncogene in prostate cancer activated by genomic fusion events between promoter upstream sequences of the TMPRSS2 and coding sequences of ERG. We showed by ERG 3' untranslated region reporter and mutagenesis assays that ERG is a direct target of miR-30. Overexpression of miR-30 in prostate cancer cells suppresses EMT phenotypes and inhibits cell migration and invasion. It also inhibits the in vitro and in vivo growth of VCaP cells, which depends on TMPRSS2-ERG for proliferation. TMPRSS2-ERG is generally regulated by androgen at the transcriptional level. Our finding reveals a new post-transcriptional mechanism of TMPRSS2-ERG regulation by Src and growth signals via miR-30 providing a rationale for targeting ERG-positive castration-resistant tumors with Src inhibitors.

CBAP interacts with the un-liganded common beta-subunit of the GM-CSF/IL-3/IL-5 receptor and induces apoptosis via mitochondrial dysfunction.

The cytoplasmic domain of the common beta-chain (betac) of the granulocyte-macrophage-colony-stimulating factor (GM-CSF)/interleukin-3 (IL-3)/IL-5 receptor contains a membrane proximal region that is sufficient to mediate ligand-dependent mitogenic activity. Within this region two motifs, designated as box 1 and box 2, are highly conserved among members of the cytokine receptor superfamily. Whereas box 1 is required for the recruitment and phosphorylation of Janus kinase-2, the function of box 2 remains largely unknown. Here, we report the identification of a novel transmembrane protein (common beta-chain associated protein (CBAP)) which directly associated with betac via the box 2 motif. Interestingly, such an association only occurred in the absence of GM-CSF in vivo. Ectopic overexpression of CBAP triggered apoptosis of factor-dependent cells via mitochondrial dysfunction, which could be inhibited by Bcl-2 overexpression. Reduced expression of endogenous CBAP by small interfering RNA did not interfere GM-CSF-activated signaling molecules, but such treatment significantly inhibited apoptosis induced by GM-CSF deprivation, but not other death stimuli. Domain mapping studies indicated that one apoptogenic domain of CBAP correlated with its ability to interact with betac. Taken together, these results suggest that CBAP modulates GM-CSF-deprivation-induced apoptosis possibly via a novel mechanism involving interaction with an un-liganded betac molecule.

Hydroxychavicol, a novel betel leaf component, inhibits platelet aggregation by suppression of cyclooxygenase, thromboxane production and calcium mobilization.

BACKGROUND AND PURPOSE: Platelet hyperactivity is important in the pathogenesis of cardiovascular diseases. Betel leaf (PBL) is consumed by 200-600 million betel quid chewers in the world. Hydroxychavicol (HC), a betel leaf component, was tested for its antiplatelet effect. EXPERIMENTAL APPROACH: We tested the effect of HC on platelet aggregation, thromboxane B(2) (TXB(2)) and reactive oxygen species (ROS) production, cyclooxygenase (COX) activity, ex vivo platelet aggregation and mouse bleeding time and platelet plug formation in vivo. The pharmacokinetics of HC in rats was also assessed. KEY RESULTS: HC inhibited arachidonic acid (AA) and collagen-induced platelet aggregation and TXB(2) production. HC inhibited the thrombin-induced TXB(2) production, but not platelet aggregation. SQ29548, suppressed collagen- and thrombin-induced TXB(2) production, but not thrombin-induced platelet aggregation. HC also suppressed COX-1/COX-2 enzyme activity and the AA-induced ROS production and Ca(2+) mobilization. HC further inhibited the ex vivo platelet aggregation of platelet-rich plasma (>100 nmole/mouse) and prolonged platelet plug formation (>300 nmole/mouse) in mesenteric microvessels, but showed little effect on bleeding time in mouse tail. Moreover, pharmacokinetics analysis found that more than 99% of HC was metabolized within 3 min of administration in Sprague-Dawley rats in vivo. CONCLUSIONS AND IMPLICATIONS: HC is a potent COX-1/COX-2 inhibitor, ROS scavenger and inhibits platelet calcium signaling, TXB(2) production and aggregation. HC could be a potential therapeutic agent for prevention and treatment of atherosclerosis and other cardiovascular diseases through its anti-inflammatory and antiplatelet effects, without effects on haemostatic functions.