Sterols can be metabolized by gut microbiota. The
cholesterol metabolites have been proposed as promoters of
colorectal cancer (CRC), while the effect of
plant sterol metabolites is unknown. This study aimed to evaluate the cytotoxicity of metabolites from
cholesterol (
coprostanol,
cholestanol,
coprostanone and cholestenone) and β-
sitosterol (ethylcoprostanol) on human colon
tumor (Caco-2) and non-
tumor (CCD-18Co) cells at physiological concentrations (9-300 μM) and exposure time (24 h). Ethylcoprostanol reduced the
tumor cell proliferation (MTT), showing in flow cytometry assays induction of apoptosis via production of
reactive oxygen species (ROS) and
ceramide. Transcriptomic analysis (qPCR) showed activation of the intrinsic apoptosis pathway (BAX/BCL2 ratio and CASP9 increased), accompanied by downregulation of the p21 gene.
Cholesterol metabolites, mainly the most hydrophobic, induced apoptosis and G0/G1 phase arrest in non-
tumor cells through overproduction of ROS. Both the intrinsic and extrinsic (CASP8 increased) apoptosis pathways occurred. In turn, a reduction in the expression of the
cyclin E1 gene confirmed the cell cycle arrest. In addition, ethylcoprostanol protected non-
tumor cells from the most cytotoxic
cholesterol metabolite (cholestenone). In conclusion, ethylcoprostanol is a promising candidate as a therapeutic adjuvant in CRC, while
cholesterol metabolites could act as CRC promoters through their cytotoxicity.