Hedgehog-Gli1 Signaling Mediates Regulation Of AQP1 Expression In Human Glioma

PartⅠHedgehog-Gli1 Signaling Mediates Regulation of AQP1 Expression in Human GliomaGlioma, especially Glioblastoma multiformes (GBMs) express increased aquaporin1(AQP1) compared to normal brain. AQPs may contribute to brain edema, cell motility, and tumor angiogenesis. Although the physiology of AQP1 has been the subject of several publications, much less is known about the trans-acting factors involved in the control of AQP1 gene expression. Furthermore the relationship between the regulation of the AQP1 expression and the major intracellular signaling pathways is also poorly concerned. Hedgehog signaling pathway plays an important role in the genesis of Glioma and is also required for sustained glioma growth and survival. In the present study, we report that Gli1, the transcriptional activator of the Hedgehog pathway, is coexpressed with AQP1 in human Glioma tissues and can enhance AQP1 gene transcription by binding to conserved core Gli-binding site in the 5'-flanking promoter region of the AQP1. Transfection 293T and U251 with Gli1 can markedly increase the AQP1 promoter reporter activity and the AQP1expression level .However, suppressing the Gli1 expression using the specific RNAi can abort this effect. The ChIP and reporter mutation analysis showed that the -406～-398 region of the AQP1 promoter is essential for regulation activity of Gli1. Then we investigated the migration and invasion ability of cell lines expressing different levels of Gli1 and AQP1. The results demonstrated that restoring the AQP1 expression in the Gli1-knockdown cell line U251-PG1 can abort the decrease in the migration and invasion ability, which suggested that Gli1 may contribute to the invasion ability of glioma cells through AQP1. The upregulation of Gli1 and its consequences of increased AQP1 in gliomas may provide a new therapeutic target, either as a cell surface marker or as a functional intervention. Screening for the more effective Small-molecule Inhibitors of the Hedgehog signaling Pathway on the basis of JervineThe Hedgehog signaling pathway plays an important role in the embryonic patterning and development of many tissues and somatic structures as well as maintaining and repairing mature tissues in adults. Uncontrolled activation of the Hh-Gli pathway has been implicated in several cancers, including medulloblastoma, rhabdomyosarcoma, melanoma, basal cell carcinoma, and breast, lung, liver, stomach, prostate, and pancreatic cancers.Blocking the Hedgehog pathway can prevent tumor cell proliferation and induce apoptosis. Inhibition of the aberrant Hh-Gli pathway has thus emerged as an attractive target for anticancer therapy. Jervine is a natural steroidal alkaloids from plants of the genus Veratrum that block the Hh signaling pathway by antagonizing Smo function. However, as a natural product, Jervine is not as active as expected and the cytotoxicity of it is also a problem. Here we generated a series of Jervine analogues by structure modification and constructed a cell-based reporter assay of Gli mediated transcription to search for products that could more effectively inhibit Hh signaling. Foure more active modified compounds were identified and importantly, the discovered compounds efficiently inhibited in vitro tumor cell proliferation in a Hh-dependent manner and successfully blocked cell growth in an in vivo xenograft model using human prostate cancer cells harboring down stream activation of the Hh pathway.