To obtain more detailed information regarding the mode of action of PBT, 5FU, and PBT-5FU on colorectal adenocarcinoma cells, the expression of certain genes involved in apoptosis was evaluated: Bax, Bid, Bad, and Bak (pro-apoptotic genes) and Bcl-2 and Bcl-XL (anti-apoptotic genes). The gene discussed is BAX; the disease is colorectal adenocarcinoma.