(a) WST-1 cell proliferation assay for NIH 3T3 cells treated with cKH-FGF2 and native FGF2. Cells were treated with various concentrations ranging from 0 (control) to 50 ng/ml and the absorbance of soluble form azan was measured at 440 nm (*t-test, two-tailed, p<0.05). (b) WST-1 cell toxicity assay for NIH 3T3 cells treated with various concentrations of cKH-FGF2 or cKH-FGF2/pEGFP (equivalent of 0 to 80 μg/ml vector). In the tested range, no toxicity was observed with the vector (t-test, two-tailed, p<0.05).