Insight into the strong inhibitory action of salt on activity of neocarzinostatin

Chin, Der Hang; Li, Huang Hsien; Sudhahar, Christopher G.; Tsai, Perng Jy

doi:10.1016/j.bmc.2010.01.031

Cited by 1 publication

(2 citation statements)

References 31 publications

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“…The number of TS, SS, and DS strand breaks were analyzed by following the Poisson distribution [46] in the conversion of supercoiled DNA (form I) into relaxed circular (form II) and linear duplex (form III) forms. Without added caffeine, the number of SS, DS, and TS breaks per nM NCS obtained in the present study were comparable to known values [44, 45], confirming the validity of the employed analytical method.…”

Section: Resultssupporting

confidence: 89%

“…Concentration of the NCS‐C stock was determined by peak integration on the HPLC profile, monitored by absorbance at 226 nm, or by the increase in A 340 following titration into excess apoNCS using a UV/Vis spectrophotometer. Supercoiled plasmid DNA pBR322 was purified from E. coli DH5α harboring the plasmid DNA using a Mini‐Prep plasmid isolation kit (Qiagen, Inc., Hilden, Germany) [44]. Calf‐thymus DNA (ct‐DNA) (Sigma, St. Louis, MO) was sonicated (∼400 bp) and purified as described in Refs.…”

Section: Methodsmentioning

confidence: 99%

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Neocarzinostatin as a probe for DNA protection activity—molecular interaction with caffeine

Chin

Kuo

et al. 2011

Molecular Carcinogenesis

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Neocarzinostatin (NCS), a potent mutagen and carcinogen, consists of an enediyne prodrug and a protein carrier. It has a unique double role in that it intercalates into DNA and imposes radical-mediated damage after thiol activation. Here we employed NCS as a probe to examine the DNA-protection capability of caffeine, one of common dietary phytochemicals with potential cancer-chemopreventive activity. NCS at the nanomolar concentration range could induce significant single- and double-strand lesions in DNA, but up to 75 ± 5% of such lesions were found to be efficiently inhibited by caffeine. The percentage of inhibition was caffeine-concentration dependent, but was not sensitive to the DNA-lesion types. The well-characterized activation reactions of NCS allowed us to explore the effect of caffeine on the enediyne-generated radicals. Postactivation analyses by chromatographic and mass spectroscopic methods identified a caffeine-quenched enediyne-radical adduct, but the yield was too small to fully account for the large inhibition effect on DNA lesions. The affinity between NCS chromophore and DNA was characterized by a fluorescence-based kinetic method. The drug-DNA intercalation was hampered by caffeine, and the caffeine-induced increases in DNA-drug dissociation constant was caffeine-concentration dependent, suggesting importance of binding affinity in the protection mechanism. Caffeine has been shown to be both an effective free radical scavenger and an intercalation inhibitor. Our results demonstrated that caffeine ingeniously protected DNA against the enediyne-induced damages mainly by inhibiting DNA intercalation beforehand. The direct scavenging of the DNA-bound NCS free radicals by caffeine played only a minor role.

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Section: Resultssupporting

confidence: 89%

Section: Methodsmentioning

confidence: 99%