Electrospray Ionization-Tandem Mass Spectrometry and 32P-Postlabeling Analyses of Tamoxifen-DNA Adducts in Humans

Beland, Frederick A.; Churchwell, Mona I.; Doerge, Daniel R.; Parkin, Daniel R; Malejka-Giganti, Danuta; Hewer, Alan; Phillips, David H.; Carmichael, Paul L.; Costa, Gonçalo Gamboa da; Marques, M. Matilde

doi:10.1093/jnci/djh195

Cited by 38 publications

(27 citation statements)

References 27 publications

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“…The discrepancy between excess total 14 C measured in intact DNA and that detected by HPLC-AMS for some patients may be due to the presence of multiple minor [ 14 C]-labeled components, eluting in areas of the chromatogram not selected for AMS analysis. These findings support the need to conduct such HPLC separations of adducted DNA for each compound under investigation when using AMS for adduct quantitation (24). Interestingly, none of the other patients exhibited a peak eluting at the same time as the polar peak 1 detected in patient 1, signifying that this is not consistently formed as a result of tamoxifen intervention.…”

Section: Hplc-ams Analysis Of Colon Dnasupporting

confidence: 53%

“…However, in each case, adducts were only observed in samples from a fraction of the patients, indicating variability in tamoxifen metabolic activation, the formation or repair of DNA adducts. Other investigators have failed to detect adducts in human samples, applying similar methods and alternative high-performance liquid chromatography (HPLC)-electrospray ionization tandem mass spectrometry approaches (24,25). Part of the reason for these discrepancies is the fact that if damage is induced, it is likely to be close to or below the limits of detection achievable with the assays typically employed.…”

Section: Introductionmentioning

confidence: 99%

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Tamoxifen Forms DNA Adducts in Human Colon after Administration of a Single [14C]-Labeled Therapeutic Dose

et al. 2007

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Tamoxifen is widely prescribed for the treatment of breast cancer and is also licensed in the United States for the prevention of this disease. However, tamoxifen therapy is associated with an increased occurrence of endometrial cancer in women, and there is also evidence that it may elevate the risk of colorectal cancer. The underlying mechanisms responsible for tamoxifen-induced carcinogenesis in women have not yet been elucidated, but much interest has focused on the role of DNA adduct formation. We investigated the propensity of tamoxifen to bind irreversibly to colorectal DNA when given to 10 women as a single [14 C]-labeled therapeutic (20 mg) dose, f18 h before undergoing colon resections. Using the sensitive technique of accelerator mass spectrometry, coupled with high-performance liquid chromatography separation of enzymatically digested DNA, a peak corresponding to authentic dG-N 2 -tamoxifen adduct was detected in samples from three patients, at levels ranging from 1 to 7 adducts/10 9 nucleotides. No [14 C]-radiolabel associated with tamoxifen or its major metabolites was detected. The presence of detectable CYP3A4 protein in all colon samples suggests that this tissue has the potential to activate tamoxifen to A-hydroxytamoxifen, in addition to that occurring in the systemic circulation, and direct interaction of this metabolite with DNA could account for the binding observed. Although the level of tamoxifeninduced damage displayed a degree of interindividual variability, when present, it was f10 to 100 times higher than that reported for other suspect human colon carcinogens such as 2-amino-1-methyl-6-phenyimidazo [4,5-b]pyridine. These findings provide a mechanistic basis through which tamoxifen could increase the incidence of colon cancers in women.

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Section: Hplc-ams Analysis Of Colon Dnasupporting

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Tamoxifen Forms DNA Adducts in Human Colon after Administration of a Single [14C]-Labeled Therapeutic Dose

et al. 2007

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“…There is also a controversy with respect to the formation of tamoxifen-DNA adducts. Although several studies have found tamoxifen-DNA adducts in endometrial tissue from women treated with tamoxifen (Hemminki et al, 1996;Shibutani et al, 2000;Hernandez-Ramon et al, 2014) or from incubation of tamoxifen with human endometrial explants (Andersson et al, 2010), there are other reports that such adducts were not detected in endometrium (Carmichael et al, 1996(Carmichael et al, , 1999Beland et al, 2004). As recently reviewed, there is clear evidence for involvement of estrogens in endometrial carcinogenesis (Ri zner, 2013), and several metabolites of tamoxifen have been shown to have estrogen agonist properties (Jordan and Gosden, 1982;Jordan, 2007).…”

Section: Discussionmentioning

confidence: 99%

Endoxifen and Other Metabolites of Tamoxifen Inhibit Human Hydroxysteroid Sulfotransferase 2A1 (hSULT2A1)

2014

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Although tamoxifen is a successful agent for treatment and prevention of estrogen-dependent breast cancer, its use has been limited by the low incidence of endometrial cancer. Human hydroxysteroid sulfotransferase 2A1 (hSULT2A1) catalyzes the formation of an a-sulfooxy metabolite of tamoxifen that is reactive toward DNA, and this has been implicated in its carcinogenicity. Also, hSULT2A1 functions in the metabolism of steroid hormones such as dehydroepiandrosterone (DHEA) and pregnenolone (PREG). These roles of hSULT2A1 in steroid hormone metabolism and in generating a reactive metabolite of tamoxifen led us to examine its interactions with tamoxifen and several of its major metabolites. We hypothesized that metabolites of tamoxifen may regulate the catalytic activity of hSULT2A1, either through direct inhibition or through serving as alternate substrates for the enzyme. We found that 4-hydroxy-N-desmethyltamoxifen (endoxifen) is a potent inhibitor of hSULT2A1-catalyzed sulfation of PREG and DHEA, with K i values of 3.5 and 2.8 mM, respectively. In the hSULT2A1-catalyzed sulfation of PREG, 4-hydroxytamoxifen (4-OHTAM) and N-desmethyltamoxifen (N-desTAM) exhibited K i values of 12.7 and 9.8 mM, respectively, whereas corresponding K i values of 19.4 and 17.2 mM were observed with DHEA as substrate. A K i value of 9.1 mM was observed for tamoxifen-N-oxide with DHEA as substrate, and this increased to 16.9 mM for the hSULT2A1-catalyzed sulfation of PREG. Three metabolites were substrates for hSULT2A1, with relative sulfation rates of 4-OHTAM > N-desTAM > > endoxifen. These results may be useful in interpreting ongoing clinical trials of endoxifen and in improving the design of related molecules.

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“…A study in Cynomolgus monkeys dosed with tamoxifen for 30 days showed that the levels of tamoxifen-DNA adducts detected in various organs by LC-ESI-MS/MS SRM were comparable to the levels detected by using a chemiluminescence immunoassay (176). Beland et al used both LC-ESI-MS/MS SRM and 32 P-postlabelling to show that tamoxifen-DNA adducts were not present in human endometrial tissue obtained from women that had been treated with tamoxifen (177).…”

Section: Quantitation Of Dna Adducts By Lc-msmentioning

confidence: 99%

Liquid chromatography-electrospray ionization-mass spectrometry: the future of DNA adduct detection

2005

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Electrospray Ionization-Tandem Mass Spectrometry and 32P-Postlabeling Analyses of Tamoxifen-DNA Adducts in Humans

Abstract: The initiation of endometrial cancer by tamoxifen is probably not due to a genotoxic mechanism involving the formation of dG-Tam or dG-desMeTam.

Cited by 38 publications

References 27 publications

Tamoxifen Forms DNA Adducts in Human Colon after Administration of a Single [14C]-Labeled Therapeutic Dose

Tamoxifen Forms DNA Adducts in Human Colon after Administration of a Single [14C]-Labeled Therapeutic Dose

Endoxifen and Other Metabolites of Tamoxifen Inhibit Human Hydroxysteroid Sulfotransferase 2A1 (hSULT2A1)

Liquid chromatography-electrospray ionization-mass spectrometry: the future of DNA adduct detection

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