Abstract: Colon cancer cells resistance to apoptosis inducing factors, particularly those working through the
extrinsic apoptotic rout, such as Tumour necrosis factor alpha (TNF-α), may due to that these cells lack of the
presence of FAS receptor on their membrane, to which TNF-α binds and causes the recruitment of caspase-8 and
other caspases cascade required in apoptotic cell death. In addition to its reported impact as anti-tumour dietary
elements, Diallyl disulfide (DADS), a major organosulfur compound found in garlic oil, was examined in this
research for its ability to induce membrane FAS expression in colonic adenocarcinoma cell line (Caco-2), and
thereby synthetizes such cells to TNF-alpha-mediated apoptosis. Our results show that the administration of DADS
to Caco-2 cell cultures significantly increased the number of dead cells, exhibited morphological changes
characteristic to apoptosis and induced caspas-3 cleavage but not caspase-8. Western blot along with flow-cytometry
data confirmed the induction of FAS expression, at the protein level, after DADS treatment, RT-PCR also confirmed
FAS expression, at the transcriptional level. This resulted in restoring Caco-2 cells sensitivity to TNF-α and
initiating the extrinsic pathway through FAS and caspase-8 cleavage. These results suggest that DADS induces
apoptosis in colonic cancerous cells not only through the intrinsic pathways but also through enhancing the extrinsic