influx in response to thrombin exposure. We observed that thrombininduced Ca 2ϩ influx in TNF-␣-stimulated HPAEC was twofold greater than in control cells. To address the relationship between store-operated Ca 2ϩ influx and TRPC1 expression, we overexpressed TRPC1 by three-to fourfold in the human dermal microvascular endothelial cell line (HMEC) using the TRPC1 cDNA. Thrombininduced store Ca 2ϩ depletion in these cells caused approximately twofold greater increase in Ca 2ϩ influx than in control cells. Furthermore, the inositol 1,4,5-trisphosphate-sensitive store-operated cationic current was increased greater than twofold in TRPC1-transfected cells compared with control. To address the role of Ca 2ϩ influx via TRPC1 in signaling endothelial permeability, we measured actinstress fiber formation and transendothelial monolayer electrical resistance (TER) in the TRPC1 cDNA-transfected HMEC and TNF-␣-challenged HPAEC. Both thrombin-induced actin-stress fiber formation and a decrease in TER were augmented in TRPC1-overexpressing HMEC compared with control cells. TNF-␣-induced increased TRPC1 expression in HPAEC also resulted in marked endothelial barrier dysfunction in response to thrombin. These findings indicate the expression level of TRPC1 in endothelial cells is a critical determinant of Ca 2ϩ influx and signaling of the increase in endothelial permeability.tumor necrosis factor-␣; store-operated calcium ion influx; transient receptor potential channel 1; endothelial barrier dysfunction MICROVASCULAR ENDOTHELIAL cells regulate the vessel wall permeability of solutes, liquid, and macromolecules and produce numerous autocrine and paracrine factors, such as NO, that modulate the contractility of the underlying vascular smooth muscle (4,5,21

Elevated levels of PAX3 and cell proliferation genes are characteristic features of rhabdomyosarcoma (RMS). We hypothesize that the increased levels of these genes are stabilized due to downregulation of specific miRNAs. In this study, we show that downregulation of miR-1, -206 and -29 stabilizes the expression of PAX3 and CCND2 in both embryonal (ERMS) and alveolar (ARMS) RMS types. Ectopic expression of miR-1 and 206 in JR1, an ERMS cell line, show significant downregulation of PAX3 protein expression, whereas overexpression of these miRNAs in Rh30, an ARMS cell line, did not show any effect in PAX3 protein levels. In ARMS, PAX3 forms a fusion transcript with FOXO1 and the resultant loss of PAX3 3 0 UTR in the fusion transcript indicate an oncogenic mechanism to evade miRNA-mediated regulation of PAX3. Further, we show that miR-1, -206 and -29 can regulate the expression of CCND2, a cell cycle gene. In addition to CCND2, miR-29 also targets E2F7, another cell cycle regulator. Cell function analysis shows that overexpression of miR-29 downregulates the expression of these cell cycle genes, induces partial G1 arrest leading to decreased cell proliferation. Taken together our data suggest that the RMS state is stabilized by the deregulation of multiple miRNAs and their target genes, supporting a tumor suppressor role for these miRNA. KEYWORDS: cell cycle genes; miRNAs; PAX3; regulatory networks; rhabdomyosarcoma Rhabdomyosarcoma (RMS) is a malignant striated muscle tumor that accounts for B3% of all childhood cancers. 1 RMS arises from primitive muscle cells and tumors show varying degrees of skeletal muscle differentiation that serves to define their classification as either embryonal (ERMS) or alveolar (ARMS) types. 2,3 ERMS, the most common type has features of embryonic muscle and are generally associated with favorable prognosis. In contrast, ARMS display poor muscle differentiation and are associated with poor outcomes. 4 Most ARMS cases are characterized by chromosomal translocation t(2;13) or t(1;13) involving genes PAX3-FKHR or PAX7-FKHR, respectively. 5 Regulatory disruptions in growth and differentiation pathways of myogenic precursor cells have been implicated in RMS development. Genes involved with muscle cell differentiation and cell proliferation have been associated with RMS development and metastasis. 6-11 Gene expression profiles comparing PAX-FOXO1-positive ARMS vs translocation-negative ERMS have identified genes relevant to tumorigenic process of ARMS and ERMS. 12 microRNAs (miRNAs) have been implicated in RMS. [13][14][15] miRNAs are small (18-22 nucleotides) evolutionarily conserved, non-coding RNAs that post-transcriptionally regulate gene expression through mRNA degradation, translation inhibition or chromatin-based silencing mechanisms. 16 Each miRNA can potentially regulate hundreds of targets either directly or indirectly. miRNAs have been shown to be deregulated in many types of cancers. 17 As a consequence, miRNAs from tumor tissue have been proposed for use in the diagnosis, classif...