Transient impact of paclitaxel on mouse fertility and protective effect of gonadotropin‑releasing hormone agonist

Inhibition of Drp1 orchestrates the responsiveness of breast cancer cells to paclitaxel but insignificantly relieves paclitaxel-related ovarian damage in mice

Chemoresistance and chemotherapy-related ovarian damage are well-reported in breast cancer (BC) young patients. Herein, the inhibition of the mitochondrial fission was invested to explore its chemosensitizing role in Paclitaxel (PTX)-resistant cells, and its ability to restore the ovarian integrity in mice receiving PTX or cisplatin chemotherapy. To establish these aims, PTX-resistance was generated in BC cells, which were treated with PTX in combination with Drp1 deficiency, via mdivi-1, or Drp1-specific siRNA transfection. Furthermore, the alterations in the ovarian structure and the endocrine-related hormones were explored in mice receiving repetitive doses of PTX or cisplatin. We found that combining PTX with mdivi-1 improved cell responsiveness to PTX, induced apoptosis- and autophagy-mediated cell death, and relieved cellular oxidative stress. Additionally, the expression of PCNA1 and cyclin B1 genes were downregulated, meanwhile, p53, p21, and mitochondrial fusion proteins (Mfu1&Mfu2) were increased. The in vivo investigations in mice demonstrated that PTX induced gonadotoxic damage similar to cisplatin, whereas dual treatment of mice with PTX+ mdivi-1 failed to restore their normal follicular count and the circulating levels of E2 and AMH hormones. These results suggested that combining Drp1 inhibition with PTX resensitized breast cancer cells to PTX but failed to offer enough protection against chemotherapy-related gonadotoxicity.

The future of fertility preservation for women treated with chemotherapy

Cytotoxic chemotherapies have been a mainstay of cancer treatment, but are associated with numerous systemic adverse effects, including impacts to fertility and endocrine health. Irreversible ovarian damage and follicle depletion are side-effects of chemotherapy that can lead to infertility and premature menopause, both being major concerns of young cancer patients. Notably, many women will proceed with fertility preservation, but unfortunately existing strategies don't entirely solve the problem. Most significantly, oocyte and embryo freezing do not prevent cancer treatment-induced ovarian damage from occurring, which may result in the impairment of long-term hormone production. Unfortunately, loss of endogenous endocrine function is not fully restored by hormone replacement therapy. Additionally, while GnRH agonists are standard care for patients receiving alkylating chemotherapy to lessen the risk of premature menopause, their efficacy is incomplete. The lack of more broadly effective options stems, in part, from our poor understanding of how different treatments damage the ovary. Here, we summarise the impacts of two commonly utilised chemotherapies - cyclophosphamide and cisplatin - on ovarian function and fertility, and discuss the mechanisms underpinning this damage. Additionally, we critically analyse current research avenues in the development of novel fertility preservation strategies, with a focus on fertoprotective agents.

Effects of chemotherapy on ovaries of pregnant mice

PURPOSE

It is unknown if future fertility is compromised by the administration of chemotherapy during pregnancy. The aim of this study was to identify if chemotherapy affects the maternal ovaries during pregnancy and whether these effects depend on type of chemotherapy and duration of exposure.

METHODS

Pregnant 8-week-old female BL6 mice were exposed to 6 different single chemotherapeutic agents (carboplatin, cisplatin, paclitaxel, epirubicin, doxorubicin, or cyclophosphamide) or saline at gestational day (GD) 13.5. The mice were sacrificed at GD 15.5 or GD 18.5. Ovaries were assessed by histopathology and immunohistochemistry. Follicle count was determined per follicle stage and per treatment modality.

RESULTS

Maternal ovarian damage was demonstrated by the presence of apoptosis and necrosis in preantral follicles. The extent of this damage depends upon type of chemotherapy and duration of exposure (2 or 5 days). After short exposure, 81% of ovaries showed histopathologic signs of damage compared to 36% after long exposure, which might suggest a transient effect. Loss of primordial follicles (PMFs) was observed after both short and long exposure, with a reduction of more than 70%. Evidence of DNA damage, as demonstrated by phospho-H2AX expression, was present in 23% (range 0-89%) of PMFs exposed to chemotherapy, but only in the short exposure group. Overall, the least damage was seen after administration of paclitaxel.

CONCLUSION

Despite physiological ovarian function suppression during gestation, chemotherapy-induced damage of the ovaries occurs in pregnant mouse models, potentially affecting future fertility.

Ovarian toxicity of carboplatin and paclitaxel in mouse carriers of mutation in BRIP1 tumor suppressor gene

More than 10% of women diagnosed with breast cancer during reproductive age carry hereditary germline pathogenic variants in high-penetrance BRCA genes or in others genes involved in DNA repair mechanisms such as PALB2, BRIP or ATM. Anticancer treatments may have an additional negative impact on the ovarian reserve and subsequently on the fertility of young patients carrying such mutations. Recently, the combination of carboplatin and paclitaxel is being recommended to these BRCA-mutated patients as neoadjuvant therapy. However, the impact on the ovary is unknown. Here, we investigated their effect of on the ovarian reserve using mice carriers of BRCA1-interacting protein C-terminal helicase-1 (BRIP1) mutation that plays an important role in BRCA1-dependent DNA repair. Results revealed that the administration of carboplatin or paclitaxel did not affect the ovarian reserve although increased DNA double-strand breaks were observed with carboplatin alone. Co-administration of carboplatin and paclitaxel resulted in a significant reduction of the ovarian reserve leading to a lower IVF performance, and an activation of the PI3K-Pten pathway, irrespective of the genetic background. This study suggests that co-administration of carboplatin and paclitaxel induces cumulative ovarian damage and infertility but a heterozygote genetic predisposition for DNA damage related to BRCA1 gene function does not increase this risk.

The effects and mechanism of taxanes on chemotherapy-associated ovarian damage: A review of current evidence

Chemotherapy is often a cause of premature ovarian insufficiency and infertility since the ovarian follicles are extremely sensitive to the effects of chemotherapeutic agents. Different chemotherapeutic agents with varying mechanisms of action may damage ovarian function differently. Taxanes are widely used in clinical cancer treatment, but the specific reproductive toxicological information is still controversial. This review described the impact and duration of taxanes on ovarian function in women and analyzed the possible reasons for different conclusions. Furthermore, the toxicity of taxanes on ovarian function and its possible mechanisms were discussed. The potential protective strategies and agents against ovarian damage induced by taxanes are also reviewed.