Katie M. Anderson

Cancer-related changes in prostate DNA as men age and early identification of metastasis in primary prostate tumors

Using statistical analyses of Fourier transform-IR spectra, we show that DNA of the histologically normal prostates of men 16–80 years old undergoes structural changes in the bases and backbone with increasing age. Of the older men (ages 55–80), 42% exhibited a DNA phenotype mimicking that of primary prostate tumors from a comparable age group. This cancer-like phenotype, which was not found in the younger men (ages 16–36), appears to arise from progressive age-related damage to DNA. The mean concentrations of 8-hydroxypurine lesions (e.g., 8-hydroxyguanine) were substantially higher for the older men than for the younger men. This finding suggests that the hydroxyl radical contributed to the structural changes that characterize the cancer-like phenotype. Strikingly, we were additionally able to discriminate between the DNA of primary prostate tumors and the DNA of primary prostate tumors from which distant metastases had been identified. Moreover, logistic regression analysis was able to predict the probability that a tumor had metastasized with ≈90% sensitivity and specificity. Collectively, these findings are particularly promising for identifying men at risk for developing prostate cancer, as well as for the early determination of whether a primary tumor has progressed to the metastatic state. This is highly important because the prognosis of histologically similar prostate carcinomas varies, thus creating a need to predict which cancers are most likely metastatic.

Antioxidant-induced changes in oxidized DNA

N-acetylcysteine (NAC), a strong antioxidant, has antigenotoxic and anticarcinogenic properties currently being investigated in clinical trials. NAC detoxifies free radicals (e.g., the hydroxyl radical, ·OH) that cause DNA changes implicated in disease (e.g., cancer). The ·OH reacts with purines to form mutagenic 8-hydroxypurine (8-OH) and putatively nonmutagenic formamidopyrimidine (Fapy) lesions. Fapy lesions inhibit DNA synthesis likely modulating the mutagenic potential of the 8-OH lesions, which would suggest that the ratio of these oxidized bases is biologically important. However, little is known about how NAC modifies oxidized DNA structure or how such modifications may affect cellular processes, such as replication and transcription. By using gas chromatography-mass spectrometry and Fourier transform-infrared spectroscopy, we found that dietary NAC (5% in the diet for 14 days) affected ·OH-induced structural changes in DNA of the hind leg of the BALB/c mouse. For example, mutagenic 8-hydroxyguanine (8-OH-Gua) was reduced ≈50% (P = 0.02) in mice fed NAC compared with controls. NAC reduced the log10 (8-OH-Gua/FapyGua) ratio from 0.58 ± 0.15 to essentially zero, a virtually neutral redox status. DNA from control mice had a remarkably high variance compared with mice fed NAC. Moreover, the DNA from treated and control mice was distinct with respect to base structure and vertical base-stacking interactions. The findings showing that NAC lowered the concentration of 8-OH-Gua, the log ratio, and the variance (previously associated with neoplastic changes) suggest that NAC reduces the mutagenic potential of oxidized DNA. These benefits could be offset by the other structural changes found after NAC exposure, which may affect the fidelity of DNA synthesis.

Oxidative changes in the DNA of stroma and epithelium from the female breast : Potential implications for breast cancer

Reciprocal interactions between the stroma and epithelium are considered to be intimately associated with the development of breast cancer. In studies of whole breast tissues, a keen interest exists in the occurrence of the mutagenic DNA lesions 8-hydroxy-2γ-deoxyguanosine and 8-hydroxy-2γ-deoxyadenosine. However, there is an apparent lack of information on the occurrence of these lesions in the DNA of the stroma, epithelium, and myoepithelium, despite the fact that these oxidation products may significantly influence reciprocal interactions between these cell types implicated in carcinogenesis. We report age-related increases in concentrations of both lesions in the stromal DNA, which occur roughly commensurate with the known rise in breast cancer incidence between 30 and 40 years of age. However, no further increases in these concentrations occurred in the older women. Plots of lesion concentrations revealed an uneven distribution, with some younger women having relatively high concentrations and some older women having relatively low concentrations. This finding implies that while increased age is a probable factor in lesion accumulations, other factors may also be influential [e.g., cellular concentrations of reactive oxygen species (ROS)]. Distinct differences were found between the base and backbone structures of the stromal DNA from younger women (ages 17-30), compared to older women (ages 50-62). In addition, comparisons of matched stromal, epithelial, and myoepithelial DNA (from the same individual) showed no differences in DNA damage, suggesting a random attack by the hydroxyl radical on all three groups. Collectively, the findings reveal that the structural changes in DNA described may potentially disrupt normal reciprocal interactions between the cell types, thus increasing breast cancer risk.

Biomarkers Signal Contaminant Effects on the Organs of English Sole (Parophrys vetulus) from Puget Sound

Fish living in contaminated environments accumulate toxic chemicals in their tissues. Biomarkers are needed to identify the resulting health effects, particularly focusing on early changes at a subcellular level. We used a suite of complementary biomarkers to signal contaminant-induced changes in the DNA structure and cellular physiology of the livers and gills of English sole (Parophrys vetulus). These sediment-dwelling fish were obtained from the industrialized lower Duwamish River (DR) in Seattle, Washington, and from Quartermaster Harbor (QMH), a relatively clean reference site in south Puget Sound. Fourier transform–infrared (FT-IR) spectroscopy, liquid chromatography/mass spectrometry (LC/MS), and gas chromatography/mass spectrometry (GC/MS) identified potentially deleterious alterations in the DNA structure of the DR fish livers and gills, compared with the QMH fish. Expression of CYP1A (a member of the cytochrome P450 multigene family of enzymes) signaled changes in the liver associated with the oxidation of organic xenobiotics, as previously found with the gill. The FT-IR models demonstrated that the liver DNA of the DR fish had a unique structure likely arising from exposure to environmental chemicals. Analysis by LC/MS and GC/MS showed higher concentrations of DNA base lesions in the liver DNA of the DR fish, suggesting that these base modifications contributed to this discrete DNA structure. A comparable analysis by LC/MS and GC/MS of base modifications provided similar results with the gill. The biomarkers described are highly promising for identifying contaminant-induced stresses in fish populations from polluted and reference sites and, in addition, for monitoring the progress of remedial actions.