title: Functional inactivation of the KLF6 tumor suppressor gene by loss of heterozygosity and increased alternative splicing in glioblastoma.
abstract: Glioblastoma multiforme (GBM) is the most common and aggressive primary brain tumor and possesses a high incidence of 10p loss. The KLF6 (Kruppel-like transcription factor) tumor suppressor gene on 10p15 is inactivated by loss of heterozygosity (LOH) and/or somatic mutation in a number of human cancers and forced expression of KLF6 in GBM lines inhibits their growth and transformation. In addition, increased expression of its alternatively spliced, cytoplasmic isoform KLF6-SV1 has now been shown to play a role in cancer pathogenesis. On the basis of these findings we examined the role of KLF6 and KLF6-SV1 in the development and progression of GBM. LOH analysis of 17 primary GBM patient samples using KLF6-specific microsatellite markers revealed that 88.2% (15/17) had LOH of the KLF6 locus. Interestingly, no KLF6 somatic mutations were identified. RNA analysis revealed concomitant decreases in all primary GBM tumors (n = 11) by approximately 80% in KLF6 expression (p < 0.001) coupled with increased KLF6-SV1 expression (p < 0.001) when compared to normal astrocytes. To determine the biological relevance of these findings, we examined the effect of KLF6 expression and KLF6-SV1 knockdown in A235 and CRL2020 cell lines. Reconstitution of KLF6 decreased cell proliferation by almost 50%, whereas targeted KLF6 reduction increased cell proliferation 2.5-4.5 fold. Conversely, targeted KLF6-SV1 reduction decreased cell proliferation by 50%. Taken together, our findings demonstrate that KLF6 allelic imbalance and decreased KLF6 and increased KLF6-SV1 expression are common findings in primary GBM tumors, and these changes have antagonistic effects on the regulation of cellular proliferation in GBM cell lines.
authors.affiliation: Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, NY 10029, USA.
authors.forename: Olga
authors.initials: O
authors.lastname: Camacho-Vanegas
authors.forename: Goutham
authors.initials: G
authors.lastname: Narla
authors.forename: Miriam S
authors.initials: MS
authors.lastname: Teixeira
authors.forename: Analisa
authors.initials: A
authors.lastname: DiFeo
authors.forename: Anjan
authors.initials: A
authors.lastname: Misra
authors.forename: Gobind
authors.initials: G
authors.lastname: Singh
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Chan
authors.forename: Scott L
authors.initials: SL
authors.lastname: Friedman
authors.forename: Burt G
authors.initials: BG
authors.lastname: Feuerstein
authors.forename: John A
authors.initials: JA
authors.lastname: Martignetti
mesh_terms: D017398:Alternative Splicing; D015153:Blotting, Western; D001932:Brain Neoplasms / Q000235:genetics*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015870:Gene Expression; D016147:Genes, Tumor Suppressor / Q000502:physiology; D005909:Glioblastoma / Q000235:genetics*; D006801:Humans; D000075723:Kruppel-Like Factor 6; D051741:Kruppel-Like Transcription Factors / Q000235:genetics*; D019656:Loss of Heterozygosity; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C105465:KLF6 protein, human; D000075723:Kruppel-Like Factor 6; D051741:Kruppel-Like Transcription Factors; D011518:Proto-Oncogene Proteins