The Effects of Bleomycin on Growth and Apoptosis of Keloid Fibroblast

ABSTRACT

Bleomycin, the generic name for a group of sulfur- containing polypeptide antibiotics derived from Streptomyces verticillus, has been used as a single agent and in combination for treatment of various neoplasms and viral diseases. Recently, intradermal bleomycin injections have been shown to bring about significant improvements in keloid and hypertrophic scar. However, the mechanism by which this drug acts on keloid is not entirely clear. In this study, the effects of bleomycin on growth rate, apoptosis, production of transforming growth factor(TGF-beta) and expression of its receptor, secretion of fibronectin were evaluated in keloid and normal human dermal fibroblasts. Human keloid and normal fibroblasts were primarily cultured from earlobe keloids of three female patients and treated with various concentration of bleomycin. Cell toxicity was assessed by MTT assay, growth rate and apoptosis was assessed by FACS, production of fibronectin by immunoprecipitation and western blot, TGF-beta secretion by ELISA, and expression of TGF-beta receptor by western blot, respectively. The obtained results are follows : Bleomycin induced cell toxicity dose-dependently in keloid fibroblasts in the range of 0.0012-0.075mg/ml, and the MTT90 and MTT50 values of bleomycin were 0.0081mg/ml and 0.0352mg/ml, respectively. Even in lower concentration (MTT90) of bleomycin, the cell growth was significantly suppressed in both normal and keloid fibroblasts, with the latter more suppressed than the former. Keloid fibroblasts secreted more TGF-beta than normal fibroblasts, but there was no significant difference of TGF-beta secretion between the group with bleomycin treatment and the untreated control group. There was no significant effect of bleomycin on the suppression of the expression of TGF-beta receptor and the production of fibronection in fibroblast. Keloid fibroblasts responded to bleomycin more sensitively than normal fibroblasts, and the percentage of apoptosis was higher in keloid fibroblasts than in normal fibroblast at the MTT50 concentration of bleomycin. Bleomycin had growth-inhibitory effect with inducing the apoptosis directly in lower concentration(MTT90). Therefore, clinical application with lower concentration than 1.0 mg/ml is adviced. Further studies, including clinical demonstration, will be required to better elucidate the anti-keloid effect of bleomycin depending on the dosage and the additive effect of different anti-keloid action by other agents. In summary, bleomycin may be a drug of promise in the treatment of keloid and hypertrophic scar.