Because p21 and p27 protein expression remained unchanged following terpinen-4-ol treatment, it is plausible that terpinen-4-ol induces G2/M arrest via a p53 independent mechanism, and that decreases in the expression of cyclin B1 and Cdc25c contribute mainly to the G2/M arrest seen in terpinen-4-ol-treated lung cancer cells. The gene discussed is TP53; the disease is lung cancer.