Cancer is a disease of altered cellular homeostasis. Therefore, pathways for induction of differentiation and programmed cell death are being considered as targets for therapeutic approaches (1 ,2) . Data indicate that those lung cancer patients whose tumors demonstrate squamous differentiation tend to survive longer (3 ,4) . Because lung tumors appear to be metaplastic to an extent (5 ,6) , attainment of the squamous state of differentiation may be feasible for all lung tumors, resulting in control of malignancy through terminal differentiation or programmed cell death (7 ,8) .
