Abstract 4541: Tumor-selective bioactivation of duocarmycin bioprecursors by cytochrome P450 enzymes provides an opportunity to treat drug-resistant breast cancer cells
Authors: Shnyder Steven D. , Loadman Paul M. , Sutherland Mark , Sheldrake Helen M. , Searcey Mark , Patterson Laurence H. , Pors Klaus 
Published: August 2015

Abstract
Background
The cytochrome P450 (CYP) enzymes are responsible for the oxidation of a diverse range of xenobiotic and endogenous compounds. The high expression of CYP1A1, 1B1 and 2W1 in tumour tissue and surrounding stroma compared to nearby normal tissue provides an opportunity for development of selective cancer therapeutics. The ultrapotent duocarmycins are ideal candidates for bioprecursor development and we have demonstrated that these can be re-engineered into derivatives selectively activated by CYP1A1, 1B1 (unpublished) and 2W1 in vitro and in vivo.1-3
Materials and methods
Standard material and methods can be found in the references below. Briefly, these include synthetic chemistry necessary for synthesis of duocarmycin bioprecursors, use of recombinant CYP bactosomes for metabolite identification using LC/MS and cell culture experiments using the MTT assay.
Results
In the present study, we have focussed on the potential of eradicating both sensitive and drug-resistant breast cancer cells (MCF-7, MDA-MB-468 and MDA-MB-231). We have evaluated a library of novel compounds in vitro and shown 3-modified CPI bioprecursors to be bioactivated to potent (&lt;10 nM) metabolites capable of damaging DNA as shown using H2A.X phosphorylation as a marker of DNA damage. LCMS confirmed the presence of hydroxylated seco-duocarmycins and structure-activity relationship studies revealed that subtle changes to the substitution pattern of the DNA recognition motif resulted in changes to the CYP bioactivation and chemosensitivity. The duocarmycin bioprecursors were intolerant by functionalization at position 7, to some extent position 6 while position 5 was needed for potent bioactivation and anticancer activity.
Conclusion Modifications to the structure of the seco-duocarmycins influences the extent of their CYP-mediated activation and indicates their potential for breast cancer chemotherapy. [1] Sheldrake et al. Re-engineering of the duocarmycin structural architecture enables bioprecursor development targeting CYP1A1 and CYP2W1 for biological activity. J Med Chem. 2013, 56, 6273-7.
[2] Travica et al. Colon cancer-specific cytochrome P450 2W1 converts duocarmycin analogues into potent tumor cytotoxins. Clin Cancer Res. 2013, 19, 2952-61.
[3] Pors et al. Modification of the duocarmycin pharmacophore enables CYP1A1 targeting for biological activity. Chem Commun. 2011, 47, 12062-4.
Citation Format: Steven D. Shnyder, Paul M. Loadman, Mark Sutherland, Helen M. Sheldrake, Mark Searcey, Laurence H. Patterson, Klaus Pors. Tumor-selective bioactivation of duocarmycin bioprecursors by cytochrome P450 enzymes provides an opportunity to treat drug-resistant breast cancer cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4541. doi:10.1158/1538-7445.AM2015-4541