title: PI3 kinase pathway regulated miRNome in glioblastoma: identification of miR-326 as a tumour suppressor miRNA.
abstract: Glioblastomas (GBM) continue to remain one of the most dreaded tumours that are highly infiltrative in nature and easily preclude comprehensive surgical resection. GBMs pose an intricate etiology as they are being associated with a plethora of genetic and epigenetic lesions. Misregulation of the PI3 kinase pathway is one of the most familiar events in GBM. While the PI3 kinase signalling regulated pathways and genes have been comprehensively studied, its impact on the miRNome is yet to be explored. The objective of this study was to elucidate the PI3 kinase pathway regulated miRNAs in GBM.
  
  
  
  miRNA expression profiling was conducted to monitor the differentially regulated miRNAs upon PI3 kinase pathway abrogation. qRT-PCR was used to measure the abundance of miR-326 and its host gene encoded transcript. Proliferation assay, colony suppression assay and wound healing assay were carried out in pre-miR transfected cells to investigate its role in malignant transformation. Potential targets of miR-326 were identified by transcriptome analysis of miR-326 overexpressing cells by whole RNA sequencing and selected targets were validated. Several publically available data sets were used for various investigations described above.
  
  
  
  We identified several miRNA that were regulated by PI3 kinase pathway. miR-326, a GBM downregulated miRNA, was validated as one of the miRNAs whose expression was alleviated upon abrogation of the PI3 kinase pathway. Overexpression of miR-326 resulted in reduced proliferation, colony suppression and hindered the migration capacity of glioma cells. Arrestin, Beta 1 (ARRB1), the host gene of miR-326, was also downregulated in GBM and interestingly, the expression of ARRB1 was also alleviated upon inhibition of the PI3 kinase pathway, indicating similar regulation pattern. More importantly, miR-326 exhibited a significant positive correlation with ARRB1 in terms of its expression. Transcriptome analysis upon miR-326 overexpression coupled with integrative bioinformatics approach identified several putative targets of miR-326. Selected targets were validated and interestingly found to be upregulated in GBM.
  
  
  
  Taken together, our study uncovered the PI3 kinase regulated miRNome in GBM. miR-326, a PI3 kinase pathway inhibited miRNA, was demonstrated as a tumour suppressor miRNA in GBM.
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, 560012, India.
authors.forename: Zahid
authors.initials: Z
authors.lastname: Nawaz
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, 560012, India.
authors.forename: Vikas
authors.initials: V
authors.lastname: Patil
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, 560012, India.
authors.forename: Yashna
authors.initials: Y
authors.lastname: Paul
authors.affiliation: Department of Neurosurgery, Sri Satya Sai Institute of Higher Medical Sciences, Bangalore, 560066, India.
authors.forename: Alangar S
authors.initials: AS
authors.lastname: Hegde
authors.affiliation: Departments of Neurosurgery, National Institute of Mental Health and Neuro Sciences, Bangalore, 560029, India.
authors.forename: Arimappamagan
authors.initials: A
authors.lastname: Arivazhagan
authors.affiliation: Departments of Neuropathology, National Institute of Mental Health and Neuro Sciences, Bangalore, 560029, India.
authors.forename: Vani
authors.initials: V
authors.lastname: Santosh
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, 560012, India. skumar@mcbl.iisc.ernet.in.
authors.forename: Kumaravel
authors.initials: K
authors.lastname: Somasundaram
mesh_terms: D001932:Brain Neoplasms / Q000235:genetics* / Q000378:metabolism*; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D016000:Cluster Analysis; D019295:Computational Biology / Q000379:methods; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D063990:Gene Ontology; D016147:Genes, Tumor Suppressor; D005909:Glioblastoma / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D035683:MicroRNAs / Q000235:genetics*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference; D015398:Signal Transduction; D059467:Transcriptome; D000071559:beta-Arrestin 1 / Q000235:genetics
chemical_list: D035683:MicroRNAs; D000071559:beta-Arrestin 1; D019869:Phosphatidylinositol 3-Kinases
keywords: ARRB1; Glioblastoma; Growth suppression and RNA sequencing; LY294002; PI3 kinase pathway; miR-326; miRNome