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DNA-binding properties of novel cis- and trans platinum-based anticancer agents in 2 human ovarian carcinoma cell
K J Mellish1, C F Barnard, B A Murrer
1CRC Centre for Cancer Therapeutics, Institute of Cancer Research, Sutton, Surrey, UK.
Abstract:
We have investigated the comparative initial DNA binding properties of 7 platinum-based anticancer drugs: 5 cis-oriented compounds, cisplatin, tetraplatin (Ormaplatin), JM118 [cis ammine dichloro (cyclohexylamine) platinum (II)], JM216 [bisacetato cis ammine dichloro (cyclohexylamine) platinum (IV)] and JM149 [cis ammine dichloro (cyclohexylamine) trans dihydroxo platinum (IV)], and 2 trans-oriented compounds, transplatin and JM335 [trans ammine dichloro (cyclohexylamine) dihydroxo platinum (IV)] in SKOV-3 and CHI human ovarian carcinoma cells. Unlike transplatin, the trans complex JM335 was comparably cytotoxic to its cis isomer JM149 and cisplatin. No significant correlation was observed between levels of total platinum bound to DNA after exposure to the 7 drugs and cytotoxicity in either cell line. Using a competitive enzyme-linked immunoabsorbent assay, DNA extracted from CH1 cells exposed to the 5 cis platinum drugs was recognized by the monoclonal antibody ICR4 (raised against DNA platinated by cisplatin) in the order JM118 > cisplatin > JM216 > tetraplatin > JM149; a strong positive correlation which just attained statistical significance was observed between recognition by ICR4 and cytotoxicity. In contrast, DNA extracted from CH1 cells exposed to the trans platinum drugs transplatin and JM335 was no more immunoreactive than control DNA. Using alkaline elution, interstrand cross-link levels after exposure to drug did not correlate with cytotoxicity in either cell line. The 5 cis drugs formed interstrand cross-links in both cell lines, whereas transplatin formed very low levels in SKOV-3 and undetectable levels in CH1. JM335 was efficient at forming interstrand cross-links in SKOV-3 but, notably, none were observed in CH1. In contrast, in the CH1 cells, single-strand breaks were observed with JM335 (but not with any other drug). The novel trans complex JM335 was unique, among the platinum drugs studied, in its ability to form both DNA interstrand cross-links and single strand breaks (DNA lesion formation being cell line dependent), a property which may account for its cytotoxicity.
Insights
Platinum anticancer drugs showed varied DNA binding and cytotoxicity. The trans complex JM335 uniquely formed DNA interstrand cross-links and single-strand breaks, correlating with its effectiveness against ovarian cancer cells.
Area of Science:
- Pharmacology and Toxicology
- Molecular Biology
- Cancer Research
Background:
- Platinum-based drugs are crucial in cancer chemotherapy.
- Understanding their DNA binding mechanisms is key to improving efficacy.
- Existing platinum drugs exhibit varying responses in different cancer cell lines.
Purpose of the Study:
- To compare the initial DNA binding properties of seven platinum-based anticancer drugs.
- To correlate DNA binding and lesion formation with cytotoxicity in ovarian cancer cells.
- To investigate the unique DNA interaction profile of the trans complex JM335.
Main Methods:
- Comparative analysis of cis- and trans-platinum drug interactions with DNA in SKOV-3 and CH1 ovarian carcinoma cells.
- Enzyme-linked immunosorbent assay (ELISA) using monoclonal antibody ICR4 to detect platinum-DNA adducts.
- Alkaline elution assays to quantify DNA interstrand cross-links and single-strand breaks.
Main Results:
- No direct correlation found between total platinum bound to DNA and cytotoxicity for the seven drugs.
- Cis-platinum drugs showed varying DNA recognition by antibody ICR4, with JM118 > cisplatin > JM216 > tetraplatin > JM149, correlating with cytotoxicity.
- The trans complex JM335 exhibited unique DNA lesion formation (interstrand cross-links and single-strand breaks) dependent on the cell line, contributing to its cytotoxicity.
Conclusions:
- Initial DNA binding levels do not solely determine platinum drug cytotoxicity.
- The novel trans complex JM335 demonstrates a unique DNA damage profile, suggesting potential for targeted ovarian cancer therapy.
- Cell-specific DNA lesion formation by JM335 highlights the complexity of platinum drug mechanisms.