Randomized Phase II Clinical Trial of Sulforaphane in Former Smokers at High Risk for Lung Cancer

Abstract

Experimental studies have shown that dietary isothiocyanates reduced cellular proliferative marker Ki-67 and increased apoptotic markers caspase-3 and terminal deoxynucleotidyl transferase–mediated dUTP nick end labeling (TUNEL) in animals, but human data are lacking. The present study was to assess whether sulforaphane would stop/reverse the progression of bronchial histopathology, reduce the Ki-67 index, and/or increase caspase-3 and TUNEL indices in humans. A randomized clinical trial (NCT03232138) was conducted in former smokers. Forty-three subjects were randomly assigned to the placebo or the treatment with a potential daily dose of 95 μmol sulforaphane for 12 months. The endpoints were the changes in histopathology scores and Ki-67, caspase-3, and TUNEL indices in post- versus pretreatment bronchial biopsies. Thirty-seven participants (17 in the sulforaphane and 20 in the placebo group) completed the study. Supplementation of sulforaphane did not show significant impact on bronchial histopathology but significantly reduced the Ki-67 index with a 20% decrease in the sulforaphane group and a 65% increase in the placebo (P ¼ 0.014). The difference was even greater in high-density (3+) positive Ki-67, with a 44% decrease in the sulforaphane group compared with a 71% increase in the placebo (P ¼ 0.004). Higher bioavailability of sulforaphane was correlated with greater reduction of the Ki-67 index (P for trend ¼ 0.019). Sulforaphane treatment had no impact on the caspase-3 or TUNEL index in bronchial biopsies. No severe adverse event was observed in the study participants. The findings of oral sulforaphane that significantly reduced the Ki-67 index in bronchial tissue support further development as a potential chemopreventive agent against lung cancer development.