Fermentation product of RS3 inhibited proliferation and induced apoptosis in colon cancer cell HCT-116

Cell free supernatant containing short chain fatty acid (SCFA) resulted from fermentation of resistant starch type three (RS3) by Clostridium butyricum BCC B2571 or Eubacterium rectale DSM 17629 were investigated for their ability to inhibit proliferation and induce apoptosis of human colon cancer cell line HCT-116. HCT-116 was cultured in complete medium and after 50% confluent, incubation was continued for another 48 hours in the absence or presence cell free supernatant containing SCFA mixture at butyrate levels up to 10 mM. The study revealed that the proliferation inhibition effect was higher (>80%) on HCT-116 treated with supernatant of C. butyricum BCC B2571 than that (<70%) of HCT-116 treated with supernatant of E. rectale DSM 17629. The cells were induced to undergo apoptosis by both supernatant. The apoptosis occured through mitochondrial pathway by changing the expression of gene Bcl-2 and Bax, thus incresed the Bax/Bcl-2 ratio by more than 3.5 fold. The protein caspase-3 was increased by more than 250% in the presence of the cell free supernatant.