Oncogene database

6608

SMO

smoothened, frizzled class receptor;SMO;smoothened, frizzled class receptor

frizzled family member 11|protein Gx|seven transmembrane helix receptor|smoothened homolog|smoothened, frizzled family receptor|smoothened, seven transmembrane spanning receptor

7q32.3

protein-coding

Hedgehog (Hh) pathway activation promotes tumors in several endodermally derived tissues, but its role in the pathogenesis of hepatocellular carcinoma (HCC) is unknown. Although normal hepatocytes lack Hh signaling, activation of the Hh pathway in endodermal progenitors is required for liver development. Thus, we hypothesized that hepatocarcinogenesis may involve regulation of Hh signaling. This pathway is activated when Hh ligand binds to its receptor, Patched (PTC). In an unoccupied state, PTC normally functions as a tumor suppressor that inhibits Smoothened (SMO), a proto-oncoprotein, from activating downstream components and transcription of target genes. Here we show that in HCCs, overexpression of the Smo proto-oncogene, as well as an increase in the stoichiometric ratio of Smo to Ptc mRNA levels, correlated with tumor size, a prognostic indicator in HCC biology. In one tumor we identified a novel Smo mutation in an evolutionarily conserved residue. We also demonstrated that HCC cell lines (HepG2 and Hep3B) expressed Hh pathway components and activated Hh transcriptional targets. In Hep3B cells, cyclopamine, an inhibitor of wild-type SMO, had no effect, but KAAD-cyclopamine, a blocker of oncogenic SMO, inhibited Hh signaling activity by 50%, decreased expression of the hepatocarcinogenic oncogene, c-myc, by 8-fold, and inhibited the growth rate of Hep3B cells by 94%. These data support our hypothesis that Hh signaling is dysregulated in human hepatocarcinogenesis. We demonstrate that overexpression and/or tumorigenic activation of the Smo proto-oncogene mediates c-myc overexpression which plays a critical role in hepatocarcinogenesis and suggests that Smo is a prognostic factor in HCC tumorigenesis.

Activation of the Hedgehog (Hh) pathway is known to drive development of basal cell carcinoma and medulloblastomas and to associate with many other types of cancer, but the exact molecular mechanisms underlying the carcinogenesis process remain elusive. We discovered that skin tumors derived from epidermal expression of oncogenic Smo, SmoM2, have elevated levels of IL-11, IL-11Ralpha, and STAT3 phosphorylation at Tyr(705). The relevance of our data to human conditions was reflected by the fact that ALL human basal cell carcinomas examined have detectable STAT3 phosphorylation, mostly in keratinocytes. The functional relevance of STAT3 in Smo-mediated carcinogenesis was revealed by epidermal specific knockout of STAT3. We showed that removal of STAT3 from mouse epidermis dramatically reduced SmoM2-mediated cell proliferation, leading to a significant decrease in epidermal thickness and tumor development. We also observed a significant reduction of epidermal stem/progenitor cell population and cyclin D1 expression in mice with epidermis-specific knockout of STAT3. Our evidence indicates that STAT3 signaling activation may be mediated by the IL-11/IL-11Ralpha signaling axis. We showed that tumor development was reduced after induced expression of SmoM2 in IL-11Ralpha null mice. Similarly, neutralizing antibodies for IL-11 reduced the tumor size. In two Hh-responsive cell lines, ES14 and C3H10T1/2, we found that addition of Smo agonist purmorphamine is sufficient to induce STAT3 phosphorylation at Tyr(705), but this effect was abolished after IL-11Ralpha down-regulation by shRNAs. Taken together, our results support an important role of the IL-11Ralpha/STAT3 signaling axis for Hh signaling-mediated signaling and carcinogenesis.

BACKGROUND: Few studies have associated microRNAs (miRNAs) with the hedgehog (Hh) pathway. Here, we investigated whether targeting smoothened (SMO) with miR-326 would affect glioma biological behavior and stemness. METHODS: To investigate the expression of SMO and miR-326 in glioma specimens and cell lines, we utilized quantitative real-time (qRT)-PCR, Western blot, immunohistochemistry, and fluorescence in situ hybridization. The luciferase reporter assay was used to verify the relationship between SMO and miR-326. We performed cell counting kit-8, transwell, and flow cytometric assays using annexin-V labeling to detect changes after transfection with siRNA against SMO or miR-326. qRT-PCR assays, neurosphere formation, and immunofluorescence were utilized to detect the modification of self-renewal and stemness in U251 tumor stem cells. A U251-implanted intracranial model was used to study the effect of miR-326 on tumor volume and SMO suppression efficacy. RESULTS: SMO was upregulated in gliomas and was associated with tumor grade and survival period. SMO inhibition suppressed the biological behaviors of glioma cells. SMO expression was inversely correlated with miR-326 and was identified as a novel direct target of miR-326. miR-326 overexpression not only repressed SMO and downstream genes but also decreased the activity of the Hh pathway. Moreover, miR-326 overexpression decreased self-renewal and stemness and partially prompted differentiation in U251 tumor stem cells. In turn, the inhibition of Hh partially elevated miR-326 expression. Intracranial tumorigenicity induced by the transfection of miR-326 was reduced and was partially mediated by the decreased SMO expression. CONCLUSIONS: This work suggests a possible molecular mechanism of the miR- 326/SMO axis, which can be a potential alternative therapeutic pathway for gliomas.