Related Experiment Videos
Cardiotoxicity of mitomycin A, mitomycin C, and seven N7 analogs in vitro
R T Dorr1, N G Shipp, J D Liddil
1College of Medicine, University of Arizona, Tucson.
Abstract:
The alkylating antitumor agents mitomycin A (MMA), mitomycin C (MMC), and seven N7 analogs were compared in terms of their cardiotoxic and antitumor activity in vitro. Neonatal rat-heart myocytes were sensitive to five of the compounds studied, including MMA, 7-dimethylamidinomitosane (BMY-25282), 7-(N-methyl-piperazinyl)-mitosane (RR-194), N7-(4-iodophenyl)-MMC (RR-208), and N7-(4-hydroxyphenyl)-MMC (M-83) in order of descending molar potency. MMA and RR-208 possessed the greatest cytotoxic potency against 8226 human myeloma tumor cells in vitro. Two of the nine mitomycins studied, BMY-25282 and M-83, showed greater cytotoxic potency for heart cells. For these two agents, the ratio of the 50% inhibitory concentration in heart cells to that in 8226 myeloma cells was 50 and 32, respectively. For the other analogs, the tumor-cell cytotoxic potency was much higher (ranging from 200 to 7,000). For the nine mitomycin compounds, a correlation was found between heart-cell toxicity and low reduction potentials (E1/2 values) ranging from -0.16 to -0.37 V. Thus, as the reduction potential decreased (easier reducibility), the cardiotoxic potency in vitro increased (r = 0.81). In contrast, mitomycins with reduction potentials of higher than -0.37 V were much less potent cardiotoxins. Thus, mitomycin C (E1/2 = -0.45 V) was noncardiotoxic even when tested at concentrations 100-fold above those pharmacologically achievable in humans. Mitomycin C also failed to enhance doxorubicin (Adriamycin) cardiotoxicity in vitro. Importantly, no correlation was found between the reduction potential and the antitumor activity of the nine analogs (n = 0.51), in this small series.
Insights
This study compared mitomycin analogs for antitumor and cardiotoxic effects. Lower reduction potentials correlated with increased cardiotoxicity, while antitumor activity showed no such link.
Area of Science:
- Pharmacology
- Medicinal Chemistry
- Toxicology
Background:
- Mitomycin analogs are alkylating agents used in cancer therapy.
- Cardiotoxicity is a significant concern with some antitumor agents.
- Understanding structure-activity relationships is crucial for developing safer drugs.
Purpose of the Study:
- To compare the in vitro cardiotoxic and antitumor activities of mitomycin A (MMA), mitomycin C (MMC), and seven N7 analogs.
- To investigate the correlation between the reduction potential of these compounds and their cardiotoxicity and antitumor efficacy.
- To identify mitomycin analogs with improved safety profiles regarding cardiotoxicity.
Main Methods:
- In vitro assessment of cytotoxicity using neonatal rat-heart myocytes and 8226 human myeloma tumor cells.
- Measurement of reduction potentials (E1/2 values) for nine mitomycin compounds.
- Calculation of ratios of 50% inhibitory concentrations (IC50) to compare selective toxicity.
Main Results:
- Five mitomycin analogs, including MMA and RR-208, exhibited cardiotoxicity in neonatal rat-heart myocytes.
- BMY-25282 and M-83 showed higher cytotoxic potency against heart cells compared to myeloma cells.
- A strong negative correlation (r = 0.81) was observed between reduction potential and cardiotoxicity; lower potentials (easier reducibility) increased cardiotoxicity.
- Mitomycin C (MMC) was noncardiotoxic in vitro, even at high concentrations, and did not enhance doxorubicin cardiotoxicity.
- No significant correlation was found between reduction potential and antitumor activity (n = 0.51).
Conclusions:
- Cardiotoxicity of mitomycin analogs is linked to their reduction potential, with more easily reducible compounds being more cardiotoxic.
- Mitomycin C demonstrates a favorable safety profile regarding cardiotoxicity.
- Further research into N7 analogs may yield antitumor agents with reduced cardiotoxic potential.