Furthermore, we also calculated the CI (combination index) values of the merged XPF–ERCC1 blocker, 5-FU or OXA in HCT116 and SW620, and the results showed that their CI values were 0.72, 0.71, 0.58, and 1, respectively, when CI ≤ 1 means that he XPF–ERCC1 blocker could increase the toxicity of 5-FU and OXA to colorectal cancer cells. The gene discussed is ERCC4; the disease is colorectal cancer.