Cytotoxicity and genotoxicity of the carcinogen aristolochic acid I (AA-I) in human bladder RT4 cells

Medjda Bellamri, Kyle Brandt, Christina V. Brown, Ming Tsang Wu, Robert J. Turesky

Research output: Contribution to journalArticlepeer-review

Abstract

Aristolochic acid (AA-I) induces upper urothelial tract cancer (UUTC) and bladder cancer (BC) in humans. AA-I forms the 7-(2ʹ-deoxyadenosin-N6-yl)aristolactam I (dA-AL-I) adduct, which induces multiple A:T-to-T:A transversion mutations in TP53 of AA-I exposed UTUC patients. This mutation is rarely reported in TP53 of other transitional cell carcinomas and thus recognized as an AA-I mutational signature. A:T-to-T:A transversion mutations were recently detected in bladder tumors of patients in Asia with known AA-I-exposure, implying that AA-I contributes to BC. Mechanistic studies on AA-I genotoxicity have not been reported in human bladder. In this study, we examined AA-I DNA adduct formation and mechanisms of toxicity in the human RT4 bladder cell line. The biological potencies of AA-I were compared to 4-aminobiphenyl, a recognized human bladder carcinogen, and several structurally related carcinogenic heterocyclic aromatic amines (HAA), which are present in urine of smokers and omnivores. AA-I (0.05–10 µM) induced a concentration- and time-dependent cytotoxicity. AA-I (100 nM) DNA adduct formation occurred at over a thousand higher levels than the principal DNA adducts formed with 4-ABP or HAAs (1 µM). dA-AL-I adduct formation was detected down to a 1 nM concentration. Studies with selective chemical inhibitors provided evidence that NQO1 is the major enzyme involved in AA-I bio-activation in RT4 cells, whereas CYP1A1, another enzyme implicated in AA-I toxicity, had a lesser role in bio-activation or detoxification of AA-I. AA-I DNA damage also induced genotoxic stress leading to p53-dependent apoptosis. These biochemical data support the human mutation data and a role for AA-I in BC.

Original languageEnglish (US)
Pages (from-to)2189-2199
Number of pages11
JournalArchives of Toxicology
Volume95
Issue number6
DOIs
StatePublished - Jun 2021

Bibliographical note

Funding Information:
The Turesky laboratory gratefully acknowledges the support of the Masonic Chair in Cancer Causation.

Publisher Copyright:
© 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

Keywords

  • Aristolochic acid I
  • Bladder cancer
  • DNA adducts
  • Genotoxicity
  • p53

PubMed: MeSH publication types

  • Journal Article

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