A Small Peptide of SPARC Reverses Chemoresistance Figure 1. Over-expression of the N-terminus domain of SPARC diminished cell viability and induced apoptosis in colorectal cancer cell lines. A) The biological domains of SPARC (SP) and sites of mutations introduced within the N-terminus (SP-N), follistatin-like (SP-F), and extracellular (SP-C) domains are represented. B-D) The effect on cell viability following over-expression of SPARC domains were assessed by transient transfection of sensitive (B) and (C) CPT resistant MIP101 cells (MIP/CPT) with plasmid constructs for SP, SP-N, SP-F, SP-C, and empty vector (ZEO) for 48 h, followed by no treatment (gray bars) or treatment (white or red bars) with 100 mM CPT-11, for an additional 24 h. Cell viability was assessed by WST assay. Transfection with the empty vector (ZEO) served as control for all experiments; ‘‘No txfn’’ = untransfected cells. D) Transfection of chemoresistant MIP/5FU cells with different mutations introduced into SP-N (SP-N mut 1 or SP-N mut2) no longer diminished the survival of cells exposed to 1000 mM 5-FU for 24 hrs. E) Cell lines stably transfected with and overexpressing SPARC (MIP/SP), SP-N (MIP/SP-N), SP-F (MIP/SP-F), SP-C (MIP/SP-C), and empty-vector (MIP/ZEO) were treated with 5 mM 5-FU for 24 h. (*) = statistically different (p,0.05) from respective untreated control (B–E) F) Stable MIP101 cells overexpressing SPARC, the different SPARC domains or empty-vector control were assessed for apoptosis by M30 staining: i) Comparison of % M30 positive cells in different cell lines after exposure to 5 mM 5-FU for 24 h, ii) representative images from M30 staining in cells after 5-FU treatment. Results represent mean 6 s.e. (n = 3–4 independent studies). doi:10.1371/journal.pone.0026390.g001 PLoS ONE | www.plosone.org 2 November 2011 | Volume 6 | Issue 11 | e26390