Antiproliferative and apoptosis effect of Lactobacillus acidophilus on HT-29 cells accompanied by subG1 cycle arrest and modulation of mTOR/p62/FAS/Caspase8/Bax pathway

Abstract Lactobacillus acidophilus is the most commonly used probiotic that is paving the preventive and biotherapeutic methods for colorectal cancer. However, the mechanisms underlying its remedial utility are largely unknown. The cell viability of the HT-29 cell line under concentrations (10⁸,10⁹ and 10¹⁰ cfu/ml) of L. acidophilus Sonicated Extract (LSE) screened out, using the MTT assay at 24 and 72 hours. The apoptosis and cell cycle arrest were assessed via flow cytometry. A possible signaling pathway of mTOR/p62/FAS/Caspase8/Bax was examined using qRT-PCR. The LSE was found as an active cell apoptosis inducer and cell proliferation inhibitor (IC50 value as 10⁸ cfu/ml after 72 hr) in a time and dose-dependent manner. Cell cycle analysis demonstrated subG1 phase arrest. Disclosing mTOR/p62/FAS/Caspase8/Bax expression, revealed another one mechanism underlying LSE-induced apoptosis while leading to cell cycle arrest. LSE upregulated the expression of the Fas death receptor along with caspase8 and Bax-mediated apoptosis genes while suppressing the anti-apoptotic mTOR and p62 expression. The results suggest that LSE has a property in the treatment of colorectal cancer by interfering with multiple cellular functions which depends on the bacterial dose and time administered.