DNA Interstrand Cross-Linking by Epichlorohydrin

Abstract

Epichlorohydrin (ECH), an important industrial chemical, is a bifunctional alkylating agent with the potential to form DNA cross-links. Occupational exposure to this suspect carcinogen leads to chromosomal aberrations, and ECH has been shown previously to undergo reaction with DNA in vivo and in vitro.We used denaturing polyacrylamide gel electrophoresis to monitor the possible formation of interstrand cross-links within DNA oligomers by ECH and the related compound, epibromohydrin (EBH). Although both compounds did indeed form cross-links between deoxyguanosine residues, EBH was a more efficient cross-linker than ECH. The optimal pH for cross-linking also varied, with ECH more efficient at pH 5.0 and EBH more efficient at pH 7.0. Both agents were relatively flexible in the sequences targeted, with comparable efficiencies for 5′-GGC and 5′GC sites. Furthermore, interstrand cross-linking by the two optical isomers of ECH correlated with their relative cytotoxicities, with R-ECH about twice as potent as S-ECH.

DNA Interstrand Cross-Linking Activity of (1-Chloroethenyl)oxirane, a Metabolite of β-chloroprene

“…No cross-links were detected at pH 7.0 (Figure 2). This combination of optimal pH (5.0) and reaction time (∼ 6 h) is similar to the conditions previously established for ECH (10). …”

“…To optimize reaction conditions for CEO cross-linking we used Duplex 1 (Table 1), containing a central 5′-GGC site previously shown to be cross-linked efficiently by ECH (10). Radiolabeled Duplex 1 was incubated with CEO at pH 5.0, 6.0, or 7.0 and aliquots removed hourly for 8 hours.…”

“…Duplexes radiolabeled on the 3′- or 5′- terminus were prepared as described previously (10). Racemic DEB and ECH were purchased from Sigma-Aldrich Chemical Company (Milwaukee, WI); CEO was prepared as described above.…”

DNA Interstrand Cross-Linking Agents and their Chemotherapeutic Potential

“…13) [22]. Epichlorhydrin 47 as well as the related epibromohydrin 48 proved the crosslinking ability that was monitored by using denaturing polyacrylamide gel electrophoresis [21]. Although both epoxides induced cross-links between deoxyguanosine residues at 5´G C and 5´G GC, epibromhydrin 48 was found to have a higher cross-linking efficiency than epichlorhydrin 47.…”

“…Another group of bifunctional alkylating agents based on the epoxide domain comprises the monoepoxides epichlorhydrin 47 [21] and (1-chloroethenyl)oxirane 49 ( Fig. 13) [22].…”