MiR-145 functions as a tumor-suppressive RNA by targeting Sox9 and adducin 3 in human glioma cells

• Published in: Neuro-oncology (Charlottesville, Va.) Va.), 2013-10, Vol.15 (10), p.1302-1316
• Main Authors: Rani, Sandhya B, Rathod, Sachin Shivaji, Karthik, Shanmuganandam, Kaur, Navjot, Muzumdar, Dattatraya, Shiras, Anjali S
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis; Basic and Translational Investigations; Blotting, Western; Brain Neoplasms - genetics; Brain Neoplasms - metabolism; Brain Neoplasms - pathology; Calmodulin-Binding Proteins - genetics; Calmodulin-Binding Proteins - metabolism; Cell Adhesion; Cell Cycle; Cell Movement; Cell Proliferation; Glioma - genetics; Glioma - metabolism; Glioma - pathology; Humans; Mice; Mice, Inbred NOD; Mice, SCID; MicroRNAs - genetics; Neoplastic Stem Cells - metabolism; Neoplastic Stem Cells - pathology; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - genetics; SOX9 Transcription Factor - genetics; SOX9 Transcription Factor - metabolism
• ISSN: 1522-8517; 1523-5866
• DOI: 10.1093/neuonc/not090

MicroRNAs (miRNAs) are increasingly being recognized as being involved in cancer development and progression in gliomas. Using a model cell system developed in our lab to study glioma progression comprising human neuroglial culture (HNGC)-1 and HNGC-2 cells, we report here that miR-145 is one of the miRNAs significantly downregulated during malignant transformation in glioblastoma multiforme (GBM). In a study using tumor samples derived from various glioma grades, we show that expression of miR-145 is decreased in a graded manner, with GBM patients showing lowest expression relative to lower-grade gliomas (P < .05) and normal brain tissues (P < .0001). Functional studies involving ectopic expression of miR-145 in glioma cells had a negative impact on cell proliferation and tumor development, as well as invasion and induced apoptosis, providing further support to the concept that inactivation of miR-145 is important for glioma disease pathogenesis. More notably, these growth-suppressive effects of miR-145 are mediated through its target proteins Sox9 and the cell adhesion-associated molecule adducin 3 (ADD3). Inhibiting Sox9 and ADD3 rescued effects of miR-145 loss. Interestingly, miR-145 loss in glioma cells led to overexpression of molecules involved in cell proliferation, like cyclin D1, c-myc, and N-myc, as well as enhanced expression of cell adhesion- and invasion-related molecules N-cadherin and E-cadherin, an effect which was again restored upon miR-145 overexpression in glioma cells. The miR-145 promoter was methylated at its cytosine-phosphate-guanine (CpG) islands in the glioma cell lines studied. Our study demonstrates that miR-145 has a tumor-suppressive function in glioblastoma in that it reduces proliferation, adhesion, and invasion of glioblastoma cells, apparently by suppressing the activity of oncogenic proteins Sox9 and ADD3. Reduced levels of miR-145 may lead to neoplastic transformation and malignant progression in glioma due to unregulated activity of these proteins.