Challenges and Potential for Ovarian Preservation with SERMs

Molecular Action of Tamoxifen in the Ovaries of Rats with Mammary Neoplasia

Tamoxifen (TAM) is a drug commonly used in patients with breast cancer. The anticancer effect of TAM occurs via its ability to antagonize estrogen-dependent growth of mammary epithelial cells. Previously, we demonstrated that TAM prevented the chemotherapy-induced loss of ovarian follicular reserves in both cancer-free rats and rats with cancer. Such follicular loss is a main cause of infertility in young women treated for cancer. The current study was undertaken to discover the molecules and intracellular pathways involved in the action of TAM in the ovaries of rats with mammary tumors. To meet this goal we used transcriptomic (RNA-Seq) and proteomic (2D-DIGE/MS) approaches. TAM inhibited the expression of genes and lncRNAs involved in ovarian steroidogenesis. Moreover, TAM altered the expression of genes related to primordial follicle activation or arrest. In addition, proteomic screening indicated the importance of basic metabolic processes in the ovarian actions of TAM. Although simple extrapolation of these data to humans is not possible, the results of this study emphasize the need to explore the ability of TAM to affect ovarian function in women undergoing cancer treatment.

Tamoxifen decreases ovarian toxicity without compromising cancer treatment in a rat model of mammary cancer

BACKGROUND

Premenopausal women diagnosed with breast cancer often face aggressive chemotherapy resulting in infertility. Tamoxifen (TAM) is a selective estrogen receptor modulator that was previously suggested as a protective agent against chemotherapy-induced ovarian failure. In the current study, we examined mechanisms of the protective action of TAM in the ovaries of tumor-bearing rats treated with the chemotherapy drug cyclophosphamide (CPA).

RESULTS

TAM prevented CPA-induced loss of ovarian follicular reserves. The protective TAM effect in the rat ovary partially resulted from decreased apoptosis. In addition, transcriptomic and proteomic screening also implicated the importance of DNA repair pathways as well as cell adhesion and extracellular matrix remodeling in the protective ovarian actions of TAM.

CONCLUSIONS

Tamoxifen shielded the ovary from the side effects of chemotherapy without lessening the tumoricidal actions of mammary cancer treatment.

Oocyte DNA damage quality control requires consecutive interplay of CHK2 and CK1 to activate p63

The survival rate of cancer patients is steadily increasing, owing to more efficient therapies. Understanding the molecular mechanisms of chemotherapy-induced premature ovarian insufficiency (POI) could identify targets for prevention of POI. Loss of the primordial follicle reserve is the most important cause of POI, with the p53 family member p63 being responsible for DNA-damage-induced apoptosis of resting oocytes. Here, we provide the first detailed mechanistic insight into the activation of p63, a process that requires phosphorylation by both the priming kinase CHK2 and the executioner kinase CK1 in mouse primordial follicles. We further describe the structural changes induced by phosphorylation that enable p63 to adopt its active tetrameric conformation and demonstrate that previously discussed phosphorylation by c-Abl is not involved in this process. Inhibition of CK1 rescues primary oocytes from doxorubicin and cisplatin-induced apoptosis, thus uncovering a new target for the development of fertoprotective therapies.

Impact of tamoxifen therapy on fertility in breast cancer survivors

OBJECTIVE

To determine whether tamoxifen use is associated with decreased ovarian reserve and decreased likelihood of having a child after a breast cancer diagnosis, using data from the Furthering Understanding of Cancer, Health, and Survivorship in Adult (FUCHSIA) Women Study.

DESIGN

Population-based cohort study.

SETTING

Not applicable.

PATIENT(S)

Three hundred ninety-seven female breast cancer survivors aged 22-45 years whose cancer was diagnosed between ages 20 and 35 years and who were at least 2 years after diagnosis; 108 survivors also participated in a clinic visit.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Time to first child after cancer diagnosis, clinical measures of ovarian reserve (antimüllerian hormone [AMH] and antral follicle count [AFC]) after cancer.

RESULT(S)

Women who had ever used tamoxifen were substantially less likely to have a child after the breast cancer diagnosis (hazard ratio [HR] 0.29; 95% confidence interval [CI], 0.16, 0.54) than women who had never used tamoxifen. After adjusting for age at diagnosis, exposure to an alkylating agent, and race, the HR was 0.25 (95% CI, 0.14, 0.47). However, after adjusting for potential confounders, women who had used tamoxifen had an estimated geometric mean AMH level 2.47 times higher (95% CI, 1.08, 5.65) than women who had never taken tamoxifen. Antral follicle count was also higher in the tamoxifen group compared with the tamoxifen nonusers when adjusted for the same variables (risk ratio 1.21; 95% CI, 0.84, 1.73).

CONCLUSION(S)

Breast cancer survivors who had used tamoxifen were less likely to have a child after breast cancer diagnosis compared with survivors who never used tamoxifen. However, tamoxifen users did not have decreased ovarian reserve compared with the tamoxifen nonusers.

LH prevents cisplatin-induced apoptosis in oocytes and preserves female fertility in mouse

Premature ovarian failure and female infertility are frequent side effects of anticancer therapies, owing to the extreme sensitivity of the ovarian reserve oocytes to the damaging effects of irradiation and chemotherapy on DNA. We report here a robust protective effect of luteinizing hormone (LH) on the primordial follicle pool of prepubertal ovaries against the cisplatin (Cs)-induced apoptosis. In vitro LH treatment of prepubertal ovarian fragments generated anti-apoptotic signals by a subset of ovarian somatic cells expressing LH receptor (LHR) through cAMP/PKA and Akt pathways. Such signals, reducing the oocyte level of pro-apoptotic TAp63 protein and favoring the repair of the Cs-damaged DNA in the oocytes, prevented their apoptosis. Noteworthy, in vivo administration to prepubertal female mice of a single dose of LH together with Cs inhibited the depletion of the primordial follicle reserve caused by the drug and preserved their fertility in reproductive age, preventing significant alteration in the number of pregnancy and of delivered pups. In conclusion, these findings establish a novel ovoprotective role for LH and further support the very attracting prospective to use physiological 'fertoprotective' approaches for preventing premature infertility and risks linked to precocious menopause in young patients who survived cancer after chemotherapy.