Tamoxifen and the Risk of Parkinson's Disease in Female Patients with Breast Cancer in Asian People: A Nationwide Population-Based Study

Tamoxifen in breast cancer and risk of Parkinson's disease: A meta-analysis

BACKGROUND

Tamoxifen is widely used for hormone-sensitive breast cancer, achieved by modulating the estrogen receptor activity in a tissue-specific manner. There is evidence to support the protective effects of estrogen against Parkinson's disease (PD), a common neurodegenerative condition. Some epidemiologic studies suggest the use of tamoxifen may modulate the PD risk. We conducted a meta-analysis to examine the association between tamoxifen and risk of PD.

METHODS

A search of PubMed using search terms synonymous with "tamoxifen" and "Parkinson's disease" was conducted. Outcomes of interest were the odds ratio (OR) of PD comparing tamoxifen-exposed to -unexposed women, as well as the incidence rate of PD in tamoxifen-exposed women.

RESULTS

A total of 37,932 subjects with breast cancer, comprising 17,233 tamoxifen-exposed subjects and 20,699 tamoxifen-unexposed subjects, satisfied the inclusion criteria. The exposure to tamoxifen ranged from 30-96 months. Using the common-effect model, the pooled OR of PD was 2.4, with (95% CI 1.91-3.01, P < 0.0001), with high heterogeneity (I2 = 81.5%, Cochran's Q test P = 0.001). Pooling 28,640 tamoxifen-exposed patients under the common-effect model found an incidence rate of 5.86 events per 10,000 person-years (95% CI 4.82-7.12) with minimal heterogeneity (I2 = 26%, Cochran's Q test P = 0.258).

CONCLUSIONS

Our meta-analysis suggests that tamoxifen use may be associated with an increased PD risk in women. However, due to heterogeneity and potential limitations of some of the studies, further clinical and functional validation will be needed. Longitudinal studies supported by imaging and biomarkers evaluation will be useful to identify the mechanisms linking tamoxifen and PD risk.

Aromatase inhibitors and the incidence of Parkinson disease: A population-based cohort study

BACKGROUND

Current guidelines recommend the treatment of hormone receptor-positive breast cancer with aromatase inhibitors (AIs) and tamoxifen in the adjuvant setting. Some observational studies have raised concerns that tamoxifen may be associated with an increased risk of Parkinson disease (PD). However, no studies have directly compared the risk of PD between AIs and tamoxifen in women diagnosed with breast cancer.

METHODS

Using the UK Clinical Practice Research Datalink, the authors assembled a cohort of women newly diagnosed with breast cancer and newly treated with either AIs or tamoxifen between January 1, 1995, and December 31, 2017. Patients were followed 1 year after treatment initiation (ie, a 1-year lag) until an incident diagnosis of PD or were censored at death from any cause, the date of transfer out of the practice, or the end of the study period (December 31, 2018). Cox proportional hazards models with inverse probability of treatment weights were used to estimate weighted hazard ratios (HRs) and 95% confidence intervals (CIs) for PD comparing AIs with tamoxifen and accounting for more than 30 confounders.

RESULTS

In all, 30,140 women with nonmetastatic breast cancer were identified: 13,838 initiated AIs, and 16,302 initiated tamoxifen. Compared with tamoxifen, AIs were not associated with an increased risk of PD (HR, 0.94; 95% CI, 0.60-1.47). Consistent results were observed across all secondary and sensitivity analyses.

CONCLUSIONS

In this large observational study, the use of AIs, in comparison with tamoxifen, was not associated with an increased risk of PD in women diagnosed with nonmetastatic breast cancer in a real-world setting.

LAY SUMMARY

Previous studies have indicated that tamoxifen may increase the risk of Parkinson disease in the treatment of breast cancer. However, no studies have directly compared the risk of Parkinson disease between aromatase inhibitors and tamoxifen. This study included 30,140 women diagnosed with breast cancer and treated with aromatase inhibitors or tamoxifen. Overall, compared with tamoxifen, aromatase inhibitors were not associated with an increased risk of Parkinson disease in women diagnosed with breast cancer. This study provides an important addition to the comparative safety profile of aromatase inhibitors and tamoxifen in the treatment of breast cancer.

Acteoside exerts neuroprotection effects in the model of Parkinson's disease via inducing autophagy: Network pharmacology and experimental study

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease. At present, the incidence rate of PD is increasing worldwide, there is no effective cure available so far, and currently using drugs are still limited in efficacy due to serious side effects. Acteoside (ACT) is an active ingredient of many valuable medicinal plants, possesses potential therapeutic effects on many pathological conditions. In this study, we dissected the neuroprotection effects of ACT on PD and its potential molecular mechanism in our PD model pathology based on network pharmacology prediction and experimental assays. Network pharmacology and bioinformatics analysis demonstrated that ACT has 381 potential targets; among them 78 putative targets associated with PD were closely related to cellular autophagy and apoptotic processes. Our experimental results showed that ACT exerted significant neuroprotection effects on Rotenone (ROT) -induced injury of neuronal cells and Drosophila melanogaster (D. melanogaster). Meanwhile, ACT treatment induced autophagy in both neuronal cell lines and fat bodies of D. melanogaster. Furthermore, ACT treatment decreased ROT induced apoptotic rate and reactive oxygen species production, increased mitochondrial membrane potentials in neuronal cells, and promoted clearance of α-synuclein (SNCA) aggregations in SNCA overexpressed cell model through the autophagy-lysosome pathway. Interestingly, ACT treatment significantly enhanced mitophagy and protected cell injury in neuronal cells. Taken together, ACT may represent a potent stimulator of mitophagy pathway, thereby exerts preventive and therapeutic effects against neurodegenerative diseases such as PD by clearing pathogenic proteins and impaired cellular organelles like damaged mitochondria in neurons.

A Report of Tamoxifen and Parkinson's Disease in a US Population and a Review of the Literature

BACKGROUND

Tamoxifen, a selective estrogen receptor modulator, has been shown to variably affect Parkinson's disease (PD) risk.

OBJECTIVE

The aim of this study was to review epidemiological literature and evaluate the rate of PD in women with breast cancer with tamoxifen exposure in a US population.

METHODS

A literature search was conducted to identify relevant studies. We performed a retrospective cohort analysis using the Nurses' Health Study Version One to report descriptive statistics.

RESULTS

Most studies suggest there may be a time-dependent effect of tamoxifen on PD risk, with the risk increasing with time from exposure. However, rates of PD in persons exposed to tamoxifen overall appear to be low. In our cohort, PD was evident in 6.2 per 1,000 of those with tamoxifen use and 3.6 per 1,000 of those without tamoxifen use. Time from breast cancer to PD diagnosis was 9.7 years among women with tamoxifen exposure and 11.7 among women without.

CONCLUSIONS

Tamoxifen may be associated with an increased risk for PD. Further research is needed to elucidate the role of estrogen and selective estrogen antagonism in PD. © 2021 International Parkinson and Movement Disorder Society.

Unraveling Targetable Systemic and Cell-Type-Specific Molecular Phenotypes of Alzheimer's and Parkinson's Brains With Digital Cytometry

Alzheimer's disease (AD) and Parkinson's disease (PD) are the two most common neurodegenerative disorders worldwide, with age being their major risk factor. The increasing worldwide life expectancy, together with the scarcity of available treatment choices, makes it thus pressing to find the molecular basis of AD and PD so that the causing mechanisms can be targeted. To study these mechanisms, gene expression profiles have been compared between diseased and control brain tissues. However, this approach is limited by mRNA expression profiles derived for brain tissues highly reflecting their degeneration in cellular composition but not necessarily disease-related molecular states. We therefore propose to account for cell type composition when comparing transcriptomes of healthy and diseased brain samples, so that the loss of neurons can be decoupled from pathology-associated molecular effects. This approach allowed us to identify genes and pathways putatively altered systemically and in a cell-type-dependent manner in AD and PD brains. Moreover, using chemical perturbagen data, we computationally identified candidate small molecules for specifically targeting the profiled AD/PD-associated molecular alterations. Our approach therefore not only brings new insights into the disease-specific and common molecular etiologies of AD and PD but also, in these realms, foster the discovery of more specific targets for functional and therapeutic exploration.

Neuroprotective and neurotoxic outcomes of androgens and estrogens in an oxidative stress environment

BACKGROUND

The role of sex hormones on cellular function is unclear. Studies show androgens and estrogens are protective in the CNS, whereas other studies found no effects or damaging effects. Furthermore, sex differences have been observed in multiple oxidative stress-associated CNS disorders, such as Alzheimer's disease, depression, and Parkinson's disease. The goal of this study is to examine the relationship between sex hormones (i.e., androgens and estrogens) and oxidative stress on cell viability.

METHODS

N27 and PC12 neuronal and C6 glial phenotypic cell lines were used. N27 cells are female rat derived, whereas PC12 cells and C6 cells are male rat derived. These cells express estrogen receptors and the membrane-associated androgen receptor variant, AR45, but not the full-length androgen receptor. N27, PC12, and C6 cells were exposed to sex hormones either before or after an oxidative stressor to examine neuroprotective and neurotoxic properties, respectively. Estrogen receptor and androgen receptor inhibitors were used to determine the mechanisms mediating hormone-oxidative stress interactions on cell viability. Since the presence of AR45 in the human brain tissue was unknown, we examined the postmortem brain tissue from men and women for AR45 protein expression.

RESULTS

Neither androgens nor estrogens were protective against subsequent oxidative stress insults in glial cells. However, these hormones exhibited neuroprotective properties in neuronal N27 and PC12 cells via the estrogen receptor. Interestingly, a window of opportunity exists for sex hormone neuroprotection, wherein temporary hormone deprivation blocked neuroprotection by sex hormones. However, if sex hormones are applied following an oxidative stressor, they exacerbated oxidative stress-induced cell loss in neuronal and glial cells.

CONCLUSIONS

Sex hormone action on cell viability is dependent on the cellular environment. In healthy neuronal cells, sex hormones are protective against oxidative stress insults via the estrogen receptor, regardless of sex chromosome complement (XX, XY). However, in unhealthy (e.g., high oxidative stress) cells, sex hormones exacerbated oxidative stress-induced cell loss, regardless of cell type or sex chromosome complement. The non-genomic AR45 receptor, which is present in humans, mediated androgen's damaging effects, but it is unknown which receptor mediated estrogen's damaging effects. These differential effects of sex hormones that are dependent on the cellular environment, receptor profile, and cell type may mediate the observed sex differences in oxidative stress-associated CNS disorders.

Assessment of Drug-Induced Toxicity Biomarkers in the Brain Microphysiological System (MPS) Using Targeted and Untargeted Molecular Profiling

Early assessment of adverse drug effects in humans is critical to avoid long-lasting harm. However, current approaches for early detection of adverse effects still lack predictive and organ-specific biomarkers to evaluate undesired responses in humans. Microphysiological systems (MPSs) are in vitro representations of human tissues and provide organ-specific translational insights for physiological processes. In this study, a brain MPS was utilized to assess molecular signatures of neurotoxic and non-neurotoxic compounds using targeted and untargeted molecular approaches. The brain MPS comprising of human embryonic stem (ES) cell-derived neural progenitor cells seeded on three-dimensional (3D), chemically defined, polyethylene glycol hydrogels was treated with the neurotoxic drug, bortezomib and the non-neurotoxic drug, tamoxifen over 14-days. Possible toxic effects were monitored with human N-acetylaspartic acid (NAA) kinetics, which correlates the neuronal function/health and DJ-1/PARK7, an oxidative stress biomarker. Changes in NAA levels were observed as early as 2-days post-bortezomib treatment, while onset detection of oxidative stress (DJ-1) was delayed until 4-days post-treatment. Separately, the untargeted extracellular metabolomics approach revealed distinct fingerprints 2-days post-bortezomib treatment as perturbations in cysteine and glycerophospholipid metabolic pathways. These results suggest accumulation of reactive oxygen species associated with oxidative stress, and disruption of membrane structure and integrity. The NAA response was strongly correlated with changes in a subset of the detected metabolites at the same time point 2-days post-treatment. Moreover, these metabolite changes correlated strongly with DJ-1 levels measured at the later time point (4-days post-treatment). This suggests that early cellular metabolic dysfunction leads to later DJ-1 leakage and cell death, and that early measurement of this subset of metabolites could predict the later occurrence of cell death. While the approach demonstrated here provides an individual case study for proof of concept, we suggest that this approach can be extended for preclinical toxicity screening and biomarker discovery studies.