Identification and functional validation of CDH11, PCSK6 and SH3GL3 as novel glioma invasion-associated candidate genes.

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. 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. 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. 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.