Antitumor activity of methoxymorpholinyl doxorubicin: potentiation by cytochrome P450 3A metabolism
1Department of Biology, Boston University, 5 Cummington Street, Boston, MA 02215, USA.
Abstract:
Methoxymorpholinyl doxorubicin (MMDX) is a novel liver cytochrome P450 (P450)-activated anticancer prodrug whose toxicity toward cultured tumor cells can be potentiated up to 100-fold by incubation with liver microsomes and NADPH. In the present study, a panel of human liver microsomes activated MMDX with potentiation ratios directly correlated to the CYP3A-dependent testosterone 6beta-hydroxylase activity of each liver sample. Microsome-activated MMDX exhibited nanomolar IC(50) values in growth-inhibition assays of human tumor cell lines representing multiple tissues of origin: lung (A549 cells), brain (U251 cells), colon (LS180 cells), and breast (MCF-7 cells). Analysis of individual cDNA-expressed CYP3A enzymes revealed that rat CYP3A1 and human CYP3A4 activated MMDX more efficiently than rat CYP3A2 and that human P450s 3A5 and 3A7 displayed little or no activity. MMDX cytotoxicity was substantially increased in Chinese hamster ovary cells after stable expression of CYP3A4 in combination with P450 reductase. CYP3A activation of MMDX abolished the parent drug's residual cross-resistance in a doxorubicin-resistant MCF-7 cell line that overexpresses P-glycoprotein. CYP3A-activated MMDX displayed a comparatively high intrinsic stability, with a t(1/2) of approximately 5.5 h at 37 degrees C. MMDX was rapidly activated by CYP3A at low ( approximately 1-5 nM) prodrug concentrations, with 100% tumor cell kill obtained after as short as a 2-h exposure to the activated metabolite. These findings demonstrate that MMDX can be activated by CYP3A metabolism to a potent, long-lived, and cell-permeable cytotoxic metabolite and suggest that this anthracycline prodrug may be used in combination with CYP3A4 in a P450 prodrug activation-based gene therapy for cancer treatment.
Insights
Methoxymorpholinyl doxorubicin (MMDX) is a novel anticancer prodrug activated by liver cytochrome P450 3A (CYP3A). This activation yields a potent metabolite effective against various cancer cells, suggesting its use in P450-based gene therapy.
Area of Science:
- Pharmacology
- Biochemistry
- Oncology
Background:
- Methoxymorpholinyl doxorubicin (MMDX) is a novel anticancer prodrug.
- Liver cytochrome P450 (P450) enzymes, particularly CYP3A, play a role in drug metabolism.
- Understanding prodrug activation mechanisms is crucial for developing effective cancer therapies.
Purpose of the Study:
- To investigate the activation of MMDX by human liver microsomes and specific CYP3A enzymes.
- To evaluate the cytotoxicity of MMDX-activated metabolites against various human tumor cell lines.
- To explore the potential of MMDX in P450 prodrug activation-based gene therapy.
Main Methods:
- Incubation of MMDX with human liver microsomes and NADPH to assess activation.
- Growth-inhibition assays using human tumor cell lines (lung, brain, colon, breast).
- Analysis of MMDX activation by individual cDNA-expressed CYP3A enzymes and P450 reductase-transfected cells.
Main Results:
- MMDX activation by liver microsomes showed potentiation ratios correlated with CYP3A activity.
- Activated MMDX exhibited nanomolar IC50 values against multiple tumor cell lines.
- Human CYP3A4 demonstrated efficient MMDX activation, leading to potent cytotoxicity and overcoming drug resistance.
- Activated MMDX metabolite is stable and rapidly kills tumor cells.
Conclusions:
- MMDX is effectively activated by CYP3A metabolism to a potent, stable, and cell-permeable cytotoxic metabolite.
- CYP3A4 is a key enzyme in MMDX activation.
- MMDX holds promise as an anthracycline prodrug for P450-based gene therapy in cancer treatment.
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