GTPase Racl plays a role in various cellular processes pertinent to cancer development.In the present study,we investigated the molecular mechanisms underlying apoptosis regulation by Rac1 by functional proteomic analysis using M14 cell lines stably transfected with constitutively active Rac1V12 or dominant negative Rac1N17.We found that the dominant negative N17 mutant inhibited paclitaxel-evoked apoptosis in the melanoma cells.Protein composition comparisons amongst the Rac1N17,Rac1V12 and control cells using proteomic analysis identified two peptide spots of interest.One was heat shock protein 27 (Hsp27),which Was upregulated in Rac1N17 cells as assessed in our gel image interpretation,peptide mass fingerprinting (PMF) and Western blot analysis.