Role of CYP1A1 in modulation of antitumor properties of the novel agent 2-(4-amino-3-methylphenyl)benzothiazole (DF 203, NSC 674495) in human breast cancer cells
Ms. Chua et al., Role of CYP1A1 in modulation of antitumor properties of the novel agent 2-(4-amino-3-methylphenyl)benzothiazole (DF 203, NSC 674495) in human breast cancer cells, CANCER RES, 60(18), 2000, pp. 5196-5203
2-(4-Amino-3-methylphenyl)benzothiazole (DF 203, NSC 674495) is a candidate
antitumor agent with potent and selective activity against human-derived t
umor cell lines ill vitro and in vivo, Only sensitive cell lines (e.g., MCF
-7) were able to accumulate and metabolize DF 203, forming the main inactiv
e metabolite, 2-(4-amino-3-methylphenyl)-6-hydroxybenzothiazole (6-OH 203).
selective metabolism may therefore underlie its antitumor profile. DF 203
6-hydroxylase activity by MCF-7 cells was not constitutive but induced only
after pretreatment of cells with DF 203, 3-methylcholanthrene, or beta-nap
hthoflavone, 6-Hydroxylation was strongly inhibited by either goat antirat
cytochrome P450 1A1 (CYP1A1) serum or cu-naphthoflavone. Both alpha-naphtho
flavone and 6-OH 203 abrogated DF 203-induced growth inhibition. Microsomes
from genetically engineered human B-lymphoblastoid cells expressing CYP1A1
, CYP1B1, or CYP2D6 metabolized DF 203 to 6-OH 203, Immunoblot analysis det
ected significantly enhanced CYP1A1 protein in a panel of sensitive breast
cancer cell lines after exposure to DF 203. Neither constitutive expression
nor induction of CYP1A1 protein was detected in nonresponsive breast (HBL
100, MDA-MB-435, and MCF-7/ADR) and prostate (PC 3 and DU 145) cancer cell
lines. The expression of CYP1B1 was also modulated by DF 203 in the same se
nsitive cell lines. However, of the two isoforms, only CYP1A1 activity was
irreversibly inhibited by DF 203 and significantly inhibited by 6-OH 203, I
n sensitive cell lines only, [C-4]DF 203-derived radioactivity bound covale
ntly to a M-r 50,000, protein which was immunoprecipitated by CYP1A1 antise
rum. The covalent binding of [C-14]DF 203 to recombinant CYP1A1 enzyme was
NADPH-dependent and reduced by 6-OH 203 and glutathione. CYP1A1 appears ess
ential for the metabolism of DF 203 and may have a pivotal, yet undefined,
role in its antitumor activity.