ABSTRACT
AIMS: The molecular mechanisms underlying the infiltrative growth of glioblastomas, the most common primary tumours of the central nervous system in adults, are still poorly understood. We aimed to identify and functionally validate novel glioma invasion-associated candidate genes. METHODS: Microarray-based expression analysis was applied to identify differentially expressed genes in microdissected infiltrating glioma cells in vivo. Promising candidate genes were selected by the invasion-associated gene ontology terms cell adhesion, endocytosis, extracellular matrix and cell migration and validated in vitro by invasion assays and in situ by immunohistochemistry. RESULTS: We identified 180 up-regulated and 61 down-regulated genes (fold change: ≥ 2; P < 0.01) in the infiltration zone relative to more central cell-rich tumour areas of malignant astrocytic gliomas (n = 11). Twenty-seven of these genes matched to invasion-related gene ontology terms. From these, we confirmed the genes encoding cadherin-11 (CDH11), proprotein convertase subtilisin/kexin type 6 (PCSK6) and SH3-domain GRB2-like 3 (SH3GL3) as novel glioma invasion-associated candidate genes, with knockdown of PCSK6 and SH3GL3 inhibiting glioma cell invasion, while inhibition of CDH11 promoted glioma cell invasion in vitro. Immunohistochemistry on glioblastoma tissue sections revealed expression of CDH11 and PCSK6 protein in glioma cells of more central, cell-rich tumour areas, with only weak or absent CDH11 immunoreactivity but consistent PCSK6 staining in infiltrating glioma cells. CONCLUSION: Using molecular profiling of microdissected primary tumour tissue specimens followed by functional in vitro analysis, we identified and validated CDH11, PCSK6 and SH3GL3 as novel glioma invasion-associated candidate genes that likely contribute to the invasive phenotype of malignant gliomas.
Subject(s)
Adaptor Proteins, Signal Transducing/genetics , Brain Neoplasms/genetics , Cadherins/genetics , Glioma/genetics , Neoplasm Invasiveness/genetics , Proprotein Convertases/genetics , Serine Endopeptidases/genetics , Adolescent , Adult , Brain Neoplasms/metabolism , Cell Movement/genetics , Female , Gene Expression Profiling , Gene Expression Regulation, Neoplastic , Glioma/metabolism , Humans , Male , Middle Aged , Young AdultABSTRACT
Pharmacological inhibitors and knockout mice have developed into routine tools to analyze the role of specific genes in behavior. Both strategies have limitations like the availability of inhibitors for only a subset of proteins and the large efforts required to construct specific mouse mutants. The recent emergence of RNA interference (RNAi)-mediated gene silencing provides a fast alternative that can be applied to any coding gene. We established an approach for the efficient generation of transgenic knockdown mice by targeted insertion of short hairpin (sh) RNA vectors into a defined genomic locus and studied the efficiency of gene silencing in the adult brain and the utility of such mice for behavioral analysis. We generated shRNA knockdown mice for the corticotropin-releasing hormone receptor type 1 (Crhr1), the leucine-rich repeat kinase 2 (Lrkk2) and the purinergic receptor P2X ligand-gated ion channel 7 (P2rx7) genes and show the ubiquitous expression of shRNA and efficient suppression of the target mRNA and protein in the brain of young and 11-month-old knockdown mice. Knockdown mice for the Crhr1 gene exhibited decreased anxiety-related behavior, an impaired stress response, and thereby recapitulate the phenotype of CRHR1 knockout mice. Our results show the feasibility of gene silencing in the adult brain and validate knockdown mice as new genetic models suitable for behavioral analysis.
