PDF file - 4.8, Effect of chemical inhibitors on the activity of signaling pathways in MDA MB231 and A549 cells expressing various levels of Ran. Western blots of phospho- and total Akt, ERK and S6K proteins in MDA MB231 and A549 cells expressing various levels of Ran grown in different growth conditions. Representative blots from two independent experiments are shown.
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.
