Multidrug resistance transporter-1 dysfunction perturbs meiosis and Ca2+ homeostasis in oocytes

In brief

Oocyte quality remains the most important and unsolved issue in reproduction. Our data show that multidrug resistance transporters and oocyte mitochondria are involved in determining oocyte quality in a mouse model.

Abstract

Multidrug resistance transporter-1 (MDR-1) is a transmembrane ATP-dependent effluxer present in organs that transport a variety of xenobiotics and by-products. Previous findings by our group demonstrated that this transporter is also present in the oocyte mitochondrial membrane and that its mutation led to abnormal mitochondrial homeostasis. Considering the importance of these organelles in the female gamete, we assessed the impact of MDR-1 dysfunction on mouse oocyte quality, with a particular focus on the meiotic spindle organization, aneuploidies, Ca2+ homeostasis, ATP production and mtDNA mutations. Our results demonstrate that young Mdr1a mutant mice produce oocytes characterized by lower quality, with a significant delay in the germinal vesicle to germinal vesicle breakdown transition, an increased percentage of symmetric divisions, chromosome misalignments and a severely altered meiotic spindle shape compared to the wild types. Mutant oocytes exhibit 7000 more SNPs in the exomic DNA and twice the amount of mitochondrial DNA (mtDNA) SNPs compared to the wild-type ones. Ca2+ analysis revealed the inability of MDR-1 mutant oocytes to manage Ca2+ storage content and oscillations in response to several stimuli, and ATP quantification shows that mutant oocytes trend toward lower ATP levels compared to wild types. Finally, 1-year-old mutant ovaries express a lower amount of SIRT1, SIRT3, SIRT5, SIRT6 and SIRT7 compared to wild-type levels. These results together emphasize the importance of MDR-1 in mitochondrial physiology and highlight the influence of MDR-1 on oocyte quality and ovarian aging.

Enumeration and Confirmation of Bacillus cereus in Foods: Collaborative Study

A collaborative study was conducted in 15 laboratories to evaluate 2 different techniques for enumerating Bacillus cereus in foods. A direct plating technique using mannitol-egg yolk-polymyxin agar and a most probable number (MPN) technique using trypticase-soy-polymyxin broth were compared for the enumeration of high and low populations of B. cereus in mashed potatoes. The collaborative results showed that the overall mean recovery obtained with the low population level was essentially the same by both techniques. However, the overall mean recovery was significantly higher by the direct plating technique at the high population level. A statistical evaluation of the data also showed that the direct plating technique had better repeatability and reproducibility than did the MFN technique at both the high and low population levels. These results suggest that the MPN technique is suitable for examining foods containing low populations of B. cereus, but that the direct plating technique is preferable for foods that contain a high population of this organism. The confirmatory technique used in the proposed method is reliable for presumptive identification of isolates as B. cereus. The method has been adopted as official first action.

Abstract P5-15-02: Evaluating the cost of endocrine therapy vs. radiation therapy alone for low risk hormone positive early stage breast cancer in elderly patients

Objective: Elderly patients with low-risk hormone-positive breast cancer are at risk of over treatment. Avoidance of radiation therapy (RT) in favor of endocrine therapy alone was first heralded as the optimal conservative strategy due to logistical simplicity, low acute sequelae and a reduction of contralateral cancers not seen with RT. However, long-term use of aromatase inhibitors (AI) is not without costs and morbidity, often leading to low compliance and notable late effects. We therefore performed a cost-effectiveness analysis to compare the outcomes and costs between AI for five years without RT versus hypofractionated RT alone without endocrine therapy.

Materials and Methods: Using data from available phase III trials and meta-analyses, we constructed a patient-level microsimulation Markov decision model to replicate the comparative outcomes between the strategies above from the societal perspective among 200,000 simulated patients. Five years of anastrozole was compared to a 15-fraction hypofractionated whole breast RT course without boost in a cohort of patients with low-risk disease as defined by CALGB 9343 entry criteria. Noncompliance with AI was modeled from recent population-based data. Relative effectiveness on ipsilateral breast tumor recurrence and contralateral breast cancers were based off the NSABP B-21 trial, adjusted to match the modern outcomes demonstrated in CALGB 9343 and PRIME II with further adjustment for AI over tamoxifen (ATAC, EBCTCG meta-analysis). Indirect costs of travel were accounted for, as were the costs of common and serious side-effects from RT (dermatitis, fibrosis, second malignancy, heart disease) and AI (arthralgia, hot flashes, osteopenia, fracture, thrombosis). A 1-year cycle time and lifetime horizon were used, with all costs adjusted to 2018 US dollars and extracted primarily from Medicare reimbursement data. The primary measure of efficacy was the quality-adjusted life-year (QALY) with age-adjusted utilities extracted from the literature. Half-cycle correction and a 3% discount rate were applied. Probabilistic sensitivity analysis was used to vary all parameters simultaneously.

Results: On average, RT was approximately $3,981 more expensive than endocrine therapy over the lifetime horizon. Under a number of assumptions, RT appeared similar in long-term effectiveness to AI therapy, with a difference of less than 0.03 quality-adjusted life years. Given the low value of the denominator in the incremental cost-effectiveness ratio (ICER), RT did not meet the formally defined $100,000/QALY threshold. On one-way sensitivity analysis, the ICER was particularly sensitive to the incidence and impact of salvage strategies for recurrence, treatment of contralateral breast cancers, cardiac events and fracture rates.

Conclusions: Modeling with the available evidence suggests it is likely that quality-of-life after RT-alone is nearly identical to an AI-alone strategy but associated with a small increase in cost. These results suggest select patients at risk of noncompliance can safely be treated with RT-alone rather than AI alone. Given the relative pros and cons of each strategy, RT-alone should be considered for select elderly low-risk breast patients.

Citation Format: Ward MC, Vicini F, Chadha M, Pierce L, Recht A, Hayman J, Thaker N, Khan A, Keisch M, Shah C. Evaluating the cost of endocrine therapy vs. radiation therapy alone for low risk hormone positive early stage breast cancer in elderly patients [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-15-02.

Cryopreservation of bacterial vegetative cells used in antibiotic assay

A long-term cryopreservation study of vegetative cells of Micrococcus lutea ATCC 9341a, Micrococcus lutea ATCC 15957, and Staphylococcus epidermidis ATCC 12228 cells, used in our antibiotic bioassay procedure, was conducted. The cryoprotective abilities of 1% methylcellulose solution and a 15% glycerol solution at -14 degrees C were determined. More organisms remained viable in 1% methylcellulose than in 15% glycerol. Overall survival of Staphylococcus epidermidis ATCC 12228 after 365 days was 1.5 logs lower than the other 2 organisms. The sensitivity and the resistance of the preserved organisms to various antibiotics did not change. The methodology is simple and inexpensive, saves analytical time, and avoids risk of contamination and sudden loss of a well-characterized culture.