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Cell-Selective Cytotoxicity of a Fluorescent Rhodium Metalloinsertor Conjugate Results from Irreversible DNA Damage
Adela Nano1, Julie M Bailis2, Natalie F Mariano2
1Division of Chemistry and Chemical Engineering , California Institute of Technology , Pasadena , California 91125 , United States.
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.
Insights
Rhodium metalloinsertors target DNA mismatches in MMR-deficient cancers, offering a new therapeutic strategy. A fluorescently labeled compound, RhPPO-Cy3, visualizes DNA damage and confirms selective cytotoxicity in these tumors.
Area of Science:
- Oncology
- Molecular Biology
- Chemical Biology
Background:
- DNA mismatch repair (MMR) deficiency characterizes up to 20% of solid tumors, leading to microsatellite instability and chemotherapy resistance.
- MMR-deficient cancers exhibit increased mutation rates and accumulated DNA mismatches, presenting a potential therapeutic vulnerability.
- Rhodium metalloinsertors are a novel class of compounds designed to selectively bind DNA mismatches, with potential as targeted cancer therapies.
Purpose of the Study:
- To elucidate the cellular mechanism of action of the potent rhodium metalloinsertor, [Rh(chrysi)(phen)(PPO)]2+ (RhPPO).
- To investigate the DNA binding and cellular effects of RhPPO conjugated to a fluorescent probe (RhPPO-Cy3) in MMR-deficient cancer cells.
Main Methods:
- Conjugation of the rhodium complex RhPPO with the fluorescent probe cyanine 3 (Cy3) to create RhPPO-Cy3.
- Cellular imaging to observe the localization and dynamics of RhPPO-Cy3 within the nucleus of MMR-deficient cancer cells.
- Assessment of DNA damage, repair protein recruitment, and apoptotic pathway activation in response to RhPPO-Cy3 treatment.
Main Results:
- RhPPO-Cy3 selectively binds to DNA mismatches and retains the potent cytotoxic activity of RhPPO against MMR-deficient cell lines.
- RhPPO-Cy3 forms discrete nuclear foci that colocalize with sites of DNA damage, indicating targeted lesion formation at mismatch sites.
- Persistent RhPPO-Cy3 foci and inhibited repair protein recruitment suggest that complex binding prevents DNA mismatch repair, leading to irreversible damage.
- RhPPO-Cy3 treatment does not activate the p53 and apoptotic pathways.
Conclusions:
- RhPPO-Cy3 binding induces irreversible DNA damage specifically at DNA mismatches within MMR-deficient cells.
- This targeted DNA damage mechanism underlies the selective cytotoxicity of RhPPO towards MMR-deficient cancers.
- The findings support the development of rhodium metalloinsertors as a targeted therapy for MMR-deficient solid tumors.
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