RNA-Binding Protein Musashi1 Modulates Glioma Cell Growth through the Post-Transcriptional Regulation of Notch and PI3 Kinase/Akt Signaling Pathways

Musashi1 (MSI1) is an RNA-binding protein that plays critical roles in nervous-system development and stem-cell self-renewal. Here, we examined its role in the progression of glioma. Short hairpin RNA (shRNA)-based MSI1-knock down (KD) in glioblastoma and medulloblastoma cells resulted in a significantly lower number of self renewing colony on day 30 (a 65% reduction), compared with non-silencing shRNA-treated control cells, indicative of an inhibitory effect of MSI1-KD on tumor cell growth and survival. Immunocytochemical staining of the MSI1-KD glioblastoma cells indicated that they ectopically expressed metaphase markers. In addition, a 2.2-fold increase in the number of MSI1-KD cells in the G2/M phase was observed. Thus, MSI1-KD caused the prolongation of mitosis and reduced the cell survival, although the expression of activated Caspase-3 was unaltered. We further showed that MSI1-KD glioblastoma cells xenografted into the brains of NOD/SCID mice formed tumors that were 96.6% smaller, as measured by a bioluminescence imaging system (BLI), than non-KD cells, and the host survival was longer (49.3±6.1 days vs. 33.6±3.6 days; P<0.01). These findings and other cell biological analyses suggested that the reduction of MSI1 in glioma cells prolonged the cell cycle by inducing the accumulation of Cyclin B1. Furthermore, MSI1-KD reduced the activities of the Notch and PI3 kinase-Akt signaling pathways, through the up-regulation of Numb and PTEN, respectively. Exposure of glioma cells to chemical inhibitors of these pathways reduced the number of spheres and living cells, as did MSI1-KD. These results suggest that MSI1 increases the growth and/or survival of certain types of glioma cells by promoting the activation of both Notch and PI3 kinase/Akt signaling

Synthesis, Structure–Activity Relationship, and Pharmacological Studies of Novel Melanin-Concentrating Hormone Receptor 1 Antagonists 3-Aminomethylquinolines: Reducing Human Ether-a-go-go-Related Gene (hERG) Associated Liabilities

Recently, we discovered 3-aminomethylquinoline derivative <b>1</b>, a selective, highly potent, centrally acting, and orally bioavailable human MCH receptor 1 (hMCHR1) antagonist, that inhibited food intake in F344 rats with diet-induced obesity (DIO). Subsequent investigation of <b>1</b> was discontinued because <b>1</b> showed potent hERG K⁺ channel inhibition in a patch-clamp study. To decrease hERG K⁺ channel inhibition, experiments with ligand-based drug designs based on <b>1</b> and a docking study were conducted. Replacement of the terminal <i>p</i>-fluorophenyl group with a cyclopropylmethoxy group, methyl group introduction on the benzylic carbon at the 3-position of the quinoline core, and employment of a [2-(acetylamino)­ethyl]­amino group as the amine portion eliminated hERG K⁺ channel inhibitory activity in a patch-clamp study, leading to the discovery of <i>N</i>-{3-[(1<i>R</i>)-1-{[2-(acetylamino)­ethyl]­amino}­ethyl]-8-methylquinolin-7-yl}-4-(cyclopropylmethoxy)­benzamide <b>(</b><i><b>R</b></i><b>)-10h</b>. The compound <b>(</b><i><b>R</b></i><b>)-10h</b> showed potent inhibitory activity against hMCHR1 and dose-dependently suppressed food intake in a 2-day study on DIO-F344 rats. Furthermore, practical chiral synthesis of <b>(</b><i><b>R</b></i><b>)-10h</b> was performed to determine the molecule’s absolute configuration