PPIG and lung carcinoma: If not be removed by the CYPs, metabolic intermediates of carcinogens are often highly active and can induce initiation and promotion of tumor [18,19].The PXR expression was associated with the inducibility of CYP genes’ activities in lung, suggesting that PXR participates in the inactivation of tobacco-carcinogenic agents and may be involve in the development of lung cancer [20].