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  • 1
    Abstract: The mTOR signaling plays an integral role in cellular homeostasis controlling the transition between the catabolic and anabolic states. Originally approved as immunosuppressive agents preventing allograft rejection, inhibitors of mTOR signaling have recently entered the arena of cancer therapy. Using rapamycin derivative (RAD001) as a prototype inhibitor, we aimed to systematically analyze the molecular mechanisms underlying the pleiotropic effects of mTOR signaling. Using proliferation- and clonogenic survival assays, a preferential sensitivity of microvascular endothelial cells (HDMVEC) followed by fibroblasts and U87 gliblastoma to RAD001 treatment was found. In contrast, lung- and prostate tumor cells demonstrated relative resistance against RAD001 treatment. In co-culture with fibroblasts, RAD001 exerted potent antiangiogenic effects by inhibiting endothelial cell tube formation. Further, RAD001 treatment efficiently prevented tumor growth in U87 tumor xenografts. Integrative transcriptome analysis was performed to decipher the molecular mechanism underlying RAD001 -induced anti-tumor and antiangiogenic effects. The predominant expression pattern was downregulation of genes after RAD001 treatment in all three sensitive cell types. Among the RAD001 downregulated genes, a transcriptional network was discovered enriched for genes related to angiogenesis processes and extracellular matrix remodeling, e. g., VEGF, HIF1A, CXCLs, IL6, FN, PAI-1 or NRP1. Of note, key components of PI3K upstream (PDK1) as well as mTORC2 downstream signaling (SGK1, NDRG) were downregulated by RAD001. Decreased expression of IMPDH and 139 common gene targets between mycophenolic acid and RAD001 suggested in part shared mechanisms underlying their antiangiogenic and immunosuppressive effects. In summary, key genetic participants governing anti-tumor and anti-angiogenic effects of mTOR inhibition were identified.
    Type of Publication: Journal article published
    PubMed ID: 23530502
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  • 2
    Keywords: ANGIOGENESIS ; CANCER ; CELLS ; ENDOTHELIAL-CELLS ; GROWTH ; IN-VITRO ; proliferation ; tumor ; CELL ; Germany ; human ; IN-VIVO ; INHIBITION ; tumor growth ; VITRO ; VIVO ; DENSITY ; RISK ; GENE ; PROTEIN ; TUMORS ; MICE ; PATIENT ; MECHANISM ; TRANSCRIPTION FACTOR ; TRANSPLANTATION ; mechanisms ; fibroblasts ; ACID ; MALIGNANCIES ; ASSAY ; NUDE-MICE ; MODULATION ; RELATIVE RISK ; signaling ; AGENT ; molecular ; ONCOLOGY ; MOLECULAR-BASIS ; fibroblast ; TUMOR-GROWTH ; DEHYDROGENASE ; mycophenolic acid ; MOLECULAR-MECHANISMS ; analysis ; ASSAYS ; USA ; cancer research ; PROTEIN-KINASE-A ; GLIOBLASTOMA ; microvascular density ; quantitative ; MOFETIL
    Abstract: The relative risk for the development of malignancies following solid organ transplantation seems to be decreased in patients treated with the immunosuppressive agent mycophenolic acid (MPA). However, the molecular mechanisms of the antineoplastic effects of MPA are not completely understood. Here, we report that human endothelial cells and fibroblasts are highly sensitive to MPA treatment. We found that U87 glioblastoma cells were resistant to MPA treatment in vitro. However U87 tumor growth was markedly inhibited in vivo in BALB/c nude mice, suggesting that MPA exerted its antitumor effects via modulation of the tumor microenvironment. Accordingly, microvascular density and pericyte coverage were markedly reduced in MPA-treated tumors in vivo. Using functional in vitro assays, we showed that MPA potently inhibited endothelial cell and fibroblast proliferation, invasion/migration, and endothelial cell tube formation. To identify the genetic participants governing the antiangiogenic and antifibrotic effects of MPA, we performed genome-wide transcriptional analysis in U87, endothelial and fibroblast cells at 6 and 12 h after MPA treatment. Network analysis revealed a critical role for MYC signaling in endothelial cells treated with MPA. Moreover, we found that the antiangiogenic effects of MPA were organized by coordinated communications between MYC and NDRG1, YY1, HIF1A, HDAC2, CDC2, GSK3B, and PRKACB signaling. The regulation of these "hub nodes" was confirmed by real-time quantitative reverse transcription-PCR and protein analysis. The critical involvement of MYC in the antiangiogenic signaling of MPA was further shown by gene knockdown experiments. Together, these data provide a molecular basis for the antiangiogenic and antifibrotic effects of MPA, which warrants further clinical investigations
    Type of Publication: Journal article published
    PubMed ID: 18566237
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