title: Fluctuation of Rac1 activity is associated with the phenotypic and transcriptional heterogeneity of glioma cells.
abstract: Phenotypic heterogeneity of cancer cells is caused not only by genetic and epigenetic alterations but also by stochastic variation of intracellular signaling molecules. Using cells that stably express Förster resonance energy transfer (FRET) biosensors, we show here a correlation between a temporal fluctuation in the activity of Rac1 and the invasive properties of C6 glioma cells. By using long-term time-lapse imaging, we found that Rac1 activity in C6 glioma cells fluctuated over a timescale that was substantially longer than that of the replication cycle. Because the relative level of Rac1 activity in each cell was unaffected by a suspension-adhesion procedure, we were able to sort C6 glioma cells according to the levels of Rac1 activity, yielding Rac1(high) and Rac1(low) cells. The Rac1(high) cells invaded more efficiently than did Rac1(low) cells in a Matrigel invasion assay. We assessed the transcriptional profiles of Rac1(high) and Rac1(low) cells and performed gene ontology analysis. Among the 14 genes that were most associated with the term 'membrane' (membrane-related genes) in Rac1(high) cells, we identified four genes that were associated with glioma invasion and Rac1 activity by using siRNA knockdown experiments. Among the transcription factors upregulated in Rac1(high) cells, Egr2 was found to positively regulate expression of the four membrane-related invasion-associated genes. The identified signaling network might cause the fluctuations in Rac1 activity and the heterogeneity in the invasive capacity of glioma cells.
authors: Department of Pathology and Biology of Diseases, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan.
authors: Hiroko
authors: H
authors: Yukinaga
authors: Clara
authors: C
authors: Shionyu
authors: Eishu
authors: E
authors: Hirata
authors: Kumiko
authors: K
authors: Ui-Tei
authors: Takeshi
authors: T
authors: Nagashima
authors: Shinji
authors: S
authors: Kondo
authors: Mariko
authors: M
authors: Okada-Hatakeyama
authors: Honda
authors: H
authors: Naoki
authors: Michiyuki
authors: M
authors: Matsuda
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D015972:Gene Expression Regulation, Neoplastic; D005910:Glioma / Q000378:metabolism / Q000473:pathology*; D009361:Neoplasm Invasiveness; D010641:Phenotype; D021381:Protein Transport; D051381:Rats; D015398:Signal Transduction; D014158:Transcription, Genetic; D059467:Transcriptome; D015854:Up-Regulation; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
chemical_list: C499134:Rac1 protein, rat; D020830:rac1 GTP-Binding Protein
keywords: Elmo1; Freq; Heterogeneity; Invasion; MMP15; MT2-MMP; NCS1; Pstpip2; Rac1; TSN17; Tetraspanin 17