Colon cancer is the most common cancer type after breast and prostate cancer in humans. Bortezomib is a proteasome inhibitor and is commonly preferred for the treatment of some types of cancer due to its efficiency and lower side effects. This study has investigated the impact of Bortezomib on cell death regarding the stimulation of autophagy. Bortezomib (Velcade) was treated to colorectal cancer cells (HT-29) for 24 hours at different concentrations (10 nM, 20 nM, and 40 nM). MTT analysis was used to determine the viability of Bortezomib-treated HT-29 cells, and immunocytochemical methods were used to determine bortezomib’s effects on the expression of Beclin-1 and LC3 levels in the HT-29 cells. In MTT analysis, viability was decreased with an increase in bortezomib concentration and the lowest viability was found at 40 nM concentration. In the study, Beclin- 1 immune reactive cells were seen as higher in 10nM and 40 nM concentrations of Bortezomib than other groups. Additionally, in LC3 evaluation, the immune reactive cell density was the highest at 40 nM concentration of Bortezomib (p