To determine whether Rb is required for histone deacetylase inhibitor-induced colorectal cancer cell apoptosis, Rb expression can be knocked out using a stably transfected Rb shRNA expression vector and cells then treated with histone deacetylase inhibitors +/- the Wnt activity inhibitor iCRT3 (to evaluate whether the observed effects are Wnt activity-dependent). Here, RB1 is linked to colorectal cancer.