title: Metabolism of the EGFR tyrosin kinase inhibitor gefitinib by cytochrome P450 1A1 enzyme in EGFR-wild type non small cell lung cancer cell lines.
abstract: BACKGROUND
  Gefitinib is a tyrosine kinase inhibitor (TKI) of the epidermal growth factor receptor (EGFR) especially effective in tumors with activating EGFR gene mutations while EGFR wild-type non small cell lung cancer (NSCLC) patients at present do not benefit from this treatment.The primary site of gefitinib metabolism is the liver, nevertheless tumor cell metabolism can significantly affect treatment effectiveness.
  
  
  RESULTS
  In this study, we investigated the intracellular metabolism of gefitinib in a panel of EGFR wild-type gefitinib-sensitive and -resistant NSCLC cell lines, assessing the role of cytochrome P450 1A1 (CYP1A1) inhibition on gefitinib efficacy. Our results indicate that there is a significant difference in drug metabolism between gefitinib-sensitive and -resistant cell lines. Unexpectedly, only sensitive cells metabolized gefitinib, producing metabolites which were detected both inside and outside the cells. As a consequence of gefitinib metabolism, the intracellular level of gefitinib was markedly reduced after 12-24 h of treatment. Consistent with this observation, RT-PCR analysis and EROD assay showed that mRNA and activity of CYP1A1 were present at significant levels and were induced by gefitinib only in sensitive cells. Gefitinib metabolism was elevated in crowded cells, stimulated by exposure to cigarette smoke extract and prevented by hypoxic condition. It is worth noting that the metabolism of gefitinib in the sensitive cells is a consequence and not the cause of drug responsiveness, indeed treatment with a CYP1A1 inhibitor increased the efficacy of the drug because it prevented the fall in intracellular gefitinib level and significantly enhanced the inhibition of EGFR autophosphorylation, MAPK and PI3K/AKT/mTOR signalling pathways and cell proliferation.
  
  
  CONCLUSIONS
  Our findings suggest that gefitinib metabolism in lung cancer cells, elicited by CYP1A1 activity, might represent an early assessment of gefitinib responsiveness in NSCLC cells lacking activating mutations. On the other hand, in metabolizing cells, the inhibition of CYP1A1 might lead to increased local exposure to the active drug and thus increase gefitinib potency.
authors: Department of Experimental Medicine, Unit of Experimental Oncology, University of Parma, Parma, Italy. roberta.alfieri@unipr.it
authors: Roberta R
authors: RR
authors: Alfieri
authors: Maricla
authors: M
authors: Galetti
authors: Stefano
authors: S
authors: Tramonti
authors: Roberta
authors: R
authors: Andreoli
authors: Paola
authors: P
authors: Mozzoni
authors: Andrea
authors: A
authors: Cavazzoni
authors: Mara
authors: M
authors: Bonelli
authors: Claudia
authors: C
authors: Fumarola
authors: Silvia
authors: S
authors: La Monica
authors: Elena
authors: E
authors: Galvani
authors: Giuseppe
authors: G
authors: De Palma
authors: Antonio
authors: A
authors: Mutti
authors: Marco
authors: M
authors: Mor
authors: Marcello
authors: M
authors: Tiseo
authors: Ettore
authors: E
authors: Mari
authors: Andrea
authors: A
authors: Ardizzoni
authors: Pier Giorgio
authors: PG
authors: Petronini
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D002289:Carcinoma, Non-Small-Cell Lung; D045744:Cell Line, Tumor; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism*; D019008:Drug Resistance, Neoplasm; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D000077156:Gefitinib; D006801:Humans; D008175:Lung Neoplasms; D009154:Mutation; D010766:Phosphorylation; D011799:Quinazolines / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; D011799:Quinazolines; D019363:Cytochrome P-450 CYP1A1; D066246:ErbB Receptors; D000077156:Gefitinib