The IC50 dosage of styrax liquidus (Turkish sweet gum obtained from trees) was set by the (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, and the apoptotic effect of styrax liquidus on HEp-2 cancer cell was determined by assessing the expression of genes involved in apoptosis (Bax, Bad, Bak1, p53, Bcl-2, Bcl-XL, Apaf-1, Caspase2, Caspase3a, Caspase9, and Caspase12) by quantitative real-time polymerase chain reaction. The gene discussed is APAF1; the disease is cancer.