Cell-Selective Cytotoxicity of a Fluorescent Rhodium Metalloinsertor Conjugate Results from Irreversible DNA Damage at Base Pair Mismatches
Abstract
Up to 20% of solid tumors are characterized by DNA mismatch repair (MMR) deficiency and microsatellite instability that confer resistance to standard of care chemotherapy. MMR-deficient cancers have an increased mutation rate, and DNA mismatches accumulate as part of these cancers. We previously described a class of compounds, rhodium metalloinsertors, that bind DNA mismatches with high specificity and selectivity and have potential as targeted therapy. [Rh(chrysi)(phen)(PPO)]2+ (RhPPO) is the most potent, selective compound in this class and acts by targeting DNA mismatches, resulting in preferential cytotoxicity to MMR-deficient cancers. To explore further the cellular mechanism of action of RhPPO, we conjugated the metal complex to a fluorescent probe, cyanine 3 (Cy3). RhPPO-Cy3 binds DNA mismatches and retains the selectivity and potent cytotoxic activity of RhPPO for MMR-deficient cell lines. RhPPO-Cy3 forms discrete foci in the cell nucleus that overlap with sites of DNA damage, suggesting that the lesions occur at or near DNA mismatch sites. RhPPO-Cy3 foci persist over time, despite initial processing of the lesion and recruitment of repair proteins, consistent with the idea that the complex binding to a mismatch prevents repair. RhPPO-Cy3 binding does not lead to activation of p53 and the apoptotic pathway. Together, these findings support the idea that RhPPO-Cy3 binding leads to irreversible DNA damage at DNA mismatches that enables selective cytotoxicity to MMR-deficient cells.
Additional Information
© 2020 American Chemical Society. Received: November 25, 2019; Revised: January 21, 2020; Published: January 22, 2020. The authors are grateful to the Beckman Laser Resources Center for its support. The authors thank Christopher Hale (Amgen) for technical assistance with image analysis. Author Contributions: A.N. and J.M.B. contributed equally to this work. This work was supported by funding from Amgen and from the Moore Foundation. The authors declare no competing financial interest.Attached Files
Supplemental Material - bi9b01037_si_001.pdf
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Additional details
- Eprint ID
- 100839
- DOI
- 10.1021/acs.biochem.9b01037
- Resolver ID
- CaltechAUTHORS:20200122-124618192
- Amgen
- Gordon and Betty Moore Foundation
- Created
-
2020-01-22Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field