DNA cross-links in human tumor cells exposed to the prodrug PR-104A: relationships to hypoxia, bioreductive metabolism, and cytotoxicity.
PR-104, currently in clinical trial, is converted systemically to the dinitrobenzamide nitrogen mustard prodrug PR-104A, which is reduced selectively in hypoxic cells to cytotoxic hydroxylamine (PR-104H) and amine (PR-104M) metabolites. Here, we evaluate the roles of this reductive metabolism, and DNA interstrand cross-links (ICL), in the hypoxic and aerobic cytotoxicity of PR-104. Using a panel of 9 human tumor cell lines, cytotoxicity was determined by clonogenic assay after a 2-hour aerobic or hypoxic exposure to PR-104A. PR-104H and PR-104M were determined by high performance liquid chromatography/mass spectrometry, and ICL with the alkaline comet assay. Under hypoxia, the relationship between ICL and cell killing was similar between cell lines. Under aerobic conditions, there was a similar relationship between ICL and cytotoxicity, except in lines with very low rates of aerobic reduction of PR-104A (A2780, C33A, H1299), which showed an ICL-independent mechanism of PR-104A cytotoxicity. Despite this, in xenografts from the same lines, the frequency of PR-104-induced ICL correlated with clonogenic cell killing (r(2) = 0.747) with greatest activity in the fast aerobic metabolizers. In addition, changing levels of hypoxia in SiHa tumors modified both ICL frequency and tumor growth delay in parallel. We conclude that both aerobic and hypoxic nitroreduction of PR-104A contribute to the monotherapy antitumor activity of PR-104 in human tumor xenografts, and that ICL are responsible for its antitumor activity and represent a broadly applicable biomarker for tumor cell killing by this novel prodrug.
Auckland Cancer Society Research Centre, The University of Auckland, Auckland, New Zealand.
Rachelle S
RS
Singleton
Christopher P
CP
Guise
Dianne M
DM
Ferry
Susan M
SM
Pullen
Mary J
MJ
Dorie
J Martin
JM
Brown
Adam V
AV
Patterson
William R
WR
Wilson
D000818:Animals; D016923:Cell Death / Q000187:drug effects; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D002699:Chlorambucil; D002853:Chromatography, Liquid; D004249:DNA Damage; D004273:DNA, Neoplasm / Q000187:drug effects* / Q000378:metabolism; D005260:Female; D045325:HCT116 Cells; D019073:HT29 Cells; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009369:Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D009588:Nitrogen Mustard Compounds / Q000493:pharmacokinetics / Q000494:pharmacology*; D011355:Prodrugs / Q000493:pharmacokinetics / Q000494:pharmacology; D053719:Tandem Mass Spectrometry; D023041:Xenograft Model Antitumor Assays
D004273:DNA, Neoplasm; D009588:Nitrogen Mustard Compounds; C524170:PR-104A; D011355:Prodrugs; D002699:Chlorambucil