Amelioration of sexual adverse effects in the early breast cancer patient

As the number of breast cancer survivors increases, the long term consequences of breast cancer treatment are gaining attention. Sexual dysfunction is a common complaint amongst breast cancer survivors, and there are few evidence based recommendations and even fewer well designed clinical trials to establish what treatments are safe or effective in this patient population. We conducted a PubMed search for articles published between 1995–2009 containing the terms breast cancer, sexual dysfunction, libido, vaginal dryness, testosterone, and vaginal estrogen. We initially reviewed articles focusing exclusively on sexual issues in breast cancer patients. Given the paucity of clinical trials addressing sexual issues in breast cancer patients, we also included studies evaluating both hormone and non-hormone based interventions for sexual dysfunction in post-menopausal women in general. Among breast cancer survivors, vaginal dryness and loss of libido represent some of the most challenging long term side effects of breast cancer treatment. In the general post-menopausal population, topical preparations of estrogens and testosterone both appear to improve sexual function; however there are conflicting reports about the efficacy and safety of these interventions in women with a history of breast cancer, and further research is warranted

Atmospheric oxygen regulation at low Proterozoic levels by incomplete oxidative weathering of sedimentary organic carbon

It is unclear why atmospheric oxygen remained trapped at low levels for more than 1.5 billion years following the Paleoproterozoic Great Oxidation Event. Here, we use models for erosion, weathering and biogeochemical cycling to show that this can be explained by the tectonic recycling of previously accumulated sedimentary organic carbon, combined with the oxygen sensitivity of oxidative weathering. Our results indicate a strong negative feedback regime when atmospheric oxygen concentration is of order pO2∼0.1 PAL (present atmospheric level), but that stability is lost at pO2<0.01 PAL. Within these limits, the carbonate carbon isotope (δ13C) record becomes insensitive to changes in organic carbon burial rate, due to counterbalancing changes in the weathering of isotopically light organic carbon. This can explain the lack of secular trend in the Precambrian δ13C record, and reopens the possibility that increased biological productivity and resultant organic carbon burial drove the Great Oxidation Event

Low rates of mutation in clinical grade human pluripotent stem cells under different culture conditions

Abstract: The occurrence of repetitive genomic changes that provide a selective growth advantage in pluripotent stem cells is of concern for their clinical application. However, the effect of different culture conditions on the underlying mutation rate is unknown. Here we show that the mutation rate in two human embryonic stem cell lines derived and banked for clinical application is low and not substantially affected by culture with Rho Kinase inhibitor, commonly used in their routine maintenance. However, the mutation rate is reduced by >50% in cells cultured under 5% oxygen, when we also found alterations in imprint methylation and reversible DNA hypomethylation. Mutations are evenly distributed across the chromosomes, except for a slight increase on the X-chromosome, and an elevation in intergenic regions suggesting that chromatin structure may affect mutation rate. Overall the results suggest that pluripotent stem cells are not subject to unusually high rates of genetic or epigenetic alterations

Trends in co-prescribing of antidepressants and tamoxifen among women with breast cancer, 2004–2010

INTRODUCTION: Nearly a decade ago, researchers identified a potential interaction between tamoxifen and strong CYP2D6 inhibitors, including several frequently used antidepressants. Based on evidence available at that time, a United States Food and Drug Administration advisory committee recommended tamoxifen’s label be changed in October 2006, noting that postmenopausal women with estrogen receptor-positive breast cancer who are poor CYP2D6 metabolizers by genotype or drug interactions may be at increased risk of cancer recurrence. The impact of accumulating drug risk information on antidepressant use is unknown. METHODS: Retrospective, longitudinal cohort study of 13,205 women aged 50–95 with breast cancer initiating tamoxifen between July 2004–December 2009. We evaluate trends in strong, moderate, and weak CYP2D6-inhibitor antidepressants and tamoxifen co-prescribing and factors associated with ongoing strong inhibitor use. A propensity-score matched control group (aromatase inhibitor initiators) was used to estimate changes in co-prescribing, accounting for secular trends. RESULTS: In each month, approximately 24% of tamoxifen and aromatase inhibitor users were prescribed antidepressants. Among women using tamoxifen and antidepressants, 34% used strong inhibitors between 2004 and 2006 versus 15% in 2010. Strong inhibitor use decreased more among tamoxifen users than aromatase inhibitor users (Difference-in-Differences, [DD]: −0.09, 95% Confidence Interval, [CI]: −0.15, −0.03). Weak inhibitor use increased among tamoxifen users from 32% between 2004 and 2006 to 52% in 2010, more rapidly than among aromatase inhibitor users (DD:0.15, CI:0.08, 0.23). The factor most strongly associated with strong inhibitor and tamoxifen co-prescribing after 2006 was prior strong inhibitor use (RR:4.73, CI:3.62–6.18). CONCLUSION: There were substantial declines in strong CYP2D6-inhibitor use among tamoxifen users following dissemination of information suggesting a potential for increased risk with co-prescribing. Whether patients and providers will continue to avoid strong inhibitor antidepressants is yet to be seen, but clinicians appear to be responsive to drug interaction risk information in this setting