PDF file - 1.6MB, Percentage of sub-G1 phase apoptotic MCF10a and MDA MB231 cells grown in serum-containing medium after Ran silencing. (A-B) Cells were infected with shRan1 and shRan2. Medium was changed to serum-free medium (DMEM) 24hr post-infection. Cells were harvested at 72hr and 96hr post-infection for (A) cell cycle and (B) Western blot analyses. (A) Significantly more sub-G1 phase cells were observed in MDA MB231 breast cancer cells than in immortalized breast epithelial cells 72 and 96 hr post-infection of the shRNAs. (B) More cleaved PARP, caspase 9 and caspase 3 were observed in MDA MB231 than in MCF10A cells upon Ran silencing, suggesting a higher apoptotic response in MDA MB231 than in MCF10a cells. Levels of Ran knockdown were similar in both cell lines. Actin was used as a loading control. (C-D) Cells were infected with shRan1 and shRan2, and harvested 72hr post-infection for (C) cell cycle and (D) Western blot analyses. (C) More apoptotic cells were observed in MDA MB231 than MCF10a cells upon Ran-silencing 72hr post-infection of shRNAs, when these two cell lines were grown in their normal medium. (D) Higher levels of cleaved PARP, caspase 9 and caspase 3 were observed at 72hr post-infection of shRNAs. Results are plotted as histogram showing the mean � SD from three independent experiments. Key; * represents p < 0.05 and ** represents p <0.01.
ARTICLE ABSTRACT
Purpose: Cancer cells have been shown to be more susceptible to Ran knockdown than normal cells. We now investigate whether Ran is a potential therapeutic target of cancers with frequently found mutations that lead to higher Ras/MEK/ERK [mitogen-activated protein/extracellular signal-regulated kinase (ERK; MEK)] and phosphoinositide 3-kinase (PI3K)/Akt/mTORC1 activities.Experimental Design: Apoptosis was measured by flow cytometry [propidium iodide (PI) and Annexin V staining] and MTT assay in cancer cells grown under different conditions after knockdown of Ran. The correlations between Ran expression and patient survival were examined in breast and lung cancers.Results: Cancer cells with their PI3K/Akt/mTORC1 and Ras/MEK/ERK pathways inhibited are less susceptible to Ran silencing–induced apoptosis. K-Ras–mutated, c-Met–amplified, and Pten-deleted cancer cells are also more susceptible to Ran silencing–induced apoptosis than their wild-type counterparts and this effect is reduced by inhibitors of the PI3K/Akt/mTORC1 and MEK/ERK pathways. Overexpression of Ran in clinical specimens is significantly associated with poor patient outcome in both breast and lung cancers. This association is dramatically enhanced in cancers with increased c-Met or osteopontin expression, or with oncogenic mutations of K-Ras or PIK3CA, all of which are mutations that potentially correlate with activation of the PI3K/Akt/mTORC1 and/or Ras/MEK/ERK pathways. Silencing Ran also results in dysregulation of nucleocytoplasmic transport of transcription factors and downregulation of Mcl-1 expression, at the transcriptional level, which are reversed by inhibitors of the PI3K/Akt/mTORC1 and MEK/ERK pathways.Conclusion: Ran is a potential therapeutic target for treatment of cancers with mutations/changes of expression in protooncogenes that lead to activation of the PI3K/Akt/mTORC1 and Ras/MEK/ERK pathways. Clin Cancer Res; 18(2); 380–91. ©2011 AACR.
