CYP3A4, CYP2C9 and CYP2B6 expression and ifosfamide turnover in breast cancer tissue microsomes

Br J Cancer. 2004 Feb 23;90(4):911-6. doi: 10.1038/sj.bjc.6601492.


Ifosfamide is a prodrug that requires bioactivation by cytochrome P450 for antitumour activity. Up to now, little is known, to what extent in addition to the liver the ifosfamide metabolism may occur intratumorally. For this purpose, we investigated the expression of CYP3A4, CYP2C9 and CYP2B6 in breast cancer tissue using Western Blotting. Ifosfamide turnover was determined by detection of metabolites of the ifosfamide 4-hydroxylation and N-dechloroethylation in tumour microsomal incubations using HPLC/UV and LC/MS. The results demonstrate that all mammary tumours (n=11) reveal CYP3A4 expression; contents varied from 0.5 to 63 pmol mg(protein)(-1). CYP2C9 (n=9) was present in all tested breast tumour samples, too, while CYP2B6 (n=10) protein could not be detected. All measured breast cancer microsomes (n=4) showed an ifosfamide N-dechloroethylation capacity in the range from 0.04 to 0.21 pmol min(-1) mg(protein)(-1), while metabolites of the 4-hydroxylation could not be determined. In conclusion, the detected presence of CYP3A4 and CYP2C9 in breast tumours offers the possibility of intratumoral turnover of ifosfamide. For the first time in the literature, we could demonstrate a turnover of ifosfamide by microsomal preparations from human breast cancer tissue. A calculated modulation of intratumoral ifosfamide turnover could considerably influence its therapeutic efficiency.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Antineoplastic Agents, Alkylating / metabolism*
  • Antineoplastic Agents, Alkylating / pharmacokinetics*
  • Aryl Hydrocarbon Hydroxylases / biosynthesis*
  • Breast Neoplasms / genetics*
  • Breast Neoplasms / pathology*
  • Breast Neoplasms / surgery
  • Cytochrome P-450 CYP2B6
  • Cytochrome P-450 CYP2C9
  • Cytochrome P-450 CYP3A
  • Cytochrome P-450 Enzyme System / biosynthesis*
  • Female
  • Humans
  • Ifosfamide / metabolism*
  • Ifosfamide / pharmacokinetics*
  • Microsomes
  • Middle Aged
  • Oxidoreductases, N-Demethylating / biosynthesis*


  • Antineoplastic Agents, Alkylating
  • Cytochrome P-450 Enzyme System
  • CYP2C9 protein, human
  • Cytochrome P-450 CYP2C9
  • Aryl Hydrocarbon Hydroxylases
  • CYP2B6 protein, human
  • CYP3A protein, human
  • Cytochrome P-450 CYP2B6
  • Cytochrome P-450 CYP3A
  • CYP3A4 protein, human
  • Oxidoreductases, N-Demethylating
  • Ifosfamide