In the mammalian ovary, progressive activation of primordial follicles from the dormant pool serves as the source of fertilizable ova. Menopause, or the end of female reproductive life, occurs when the primordial follicle pool is exhausted. However, the molecular mechanisms underlying follicle activation are poorly understood. We provide genetic evidence that in mice lacking PTEN (phosphatase and tensin homolog deleted on chromosome 10) in oocytes, a major negative regulator of phosphatidylinositol 3-kinase (PI3K), the entire primordial follicle pool becomes activated. Subsequently, all primordial follicles become depleted in early adulthood, causing premature ovarian failure (POF). Our results show that the mammalian oocyte serves as the headquarters of programming of follicle activation and that the oocyte PTEN-PI3K pathway governs follicle activation through control of initiation of oocyte growth.

Despite neoadjuvant/conversion chemotherapy, the prognosis of cT4a/bN+ gastric cancer is poor. Immune checkpoint inhibitors (ICIs) and antiangiogenic agents have shown activity in late-stage gastric cancer, but their efficacy in the neoadjuvant/conversion setting is unclear. In this single-armed, phase II, exploratory trial (NCT03878472), we evaluate the efficacy of a combination of ICI (camrelizumab), antiangiogenesis (apatinib), and chemotherapy (S-1 ± oxaliplatin) for neoadjuvant/conversion treatment of cT4a/bN+ gastric cancer. The primary endpoints are pathological responses and their potential biomarkers. Secondary endpoints include safety, objective response, progression-free survival, and overall survival. Complete and major pathological response rates are 15.8% and 26.3%. Pathological responses correlate significantly with microsatellite instability status, PD-L1 expression, and tumor mutational burden. In addition, multi-omics examination reveals several putative biomarkers for pathological responses, including RREB1 and SSPO mutation, immune-related signatures, and a peripheral T cell expansion score. Multi-omics also demonstrates dynamic changes in dominant tumor subclones, immune microenvironments, and T cell receptor repertoires during neoadjuvant immunotherapy. The toxicity and post-surgery complications are limited. These data support further validation of ICI- and antiangiogenesis-based neoadjuvant/conversion therapy in large randomized trials and provide candidate biomarkers.

In recent years, mammalian oocytes have been proposed to have important roles in the orchestration of ovarian follicular development and fertility. To determine whether intra-oocyte Foxo3a, a component of the phosphatidylinositol 3-kinase (PI3K) signaling pathway, influences follicular development and female fertility, a transgenic mouse model was generated with constitutively active Foxo3a expressed in oocytes. We found that the female transgenic mice were infertile, which was caused by retarded oocyte growth and follicular development, and anovulation. Further mechanistic studies revealed that the constitutively active Foxo3a in oocytes caused a dramatic reduction in the expression of bone morphogenic protein 15 (Bmp15), connexin 37 and connexin 43, which are important molecules for the establishment of paracrine and gap junction communications in follicles. Foxo3a was also found to facilitate the nuclear localization of p27^kip1 in oocytes, a cyclin-dependent kinase (Cdk) inhibitor that may serve to inhibit oocyte growth. The results from the current study indicate that Foxo3a is an important intra-oocyte signaling molecule that negatively regulates oocyte growth and follicular development. Our study may therefore give some insight into oocyte-borne genetic aberrations that cause defects in follicular development and anovulation in human diseases, such as premature ovarian failure.

Immature ovarian primordial follicles are essential for maintenance of the reproductive lifespan of female mammals. Recently, it was found that overactivation of the phosphatidylinositol 3-kinase (PI3K) signaling in oocytes of primordial follicles by an oocyte-specific deletion of Pten (phosphatase and tensin homolog deleted on chromosome ten), the gene encoding PI3K negative regulator PTEN, results in premature activation of the entire pool of primordial follicles, indicating that activation of the PI3K pathway in oocytes is important for control of follicular activation. To investigate whether PI3K signaling in oocytes of primary and further developed follicles also plays a role at later stages in follicular development and ovulation, we conditionally deleted the Pten gene from oocytes of primary and further developed follicles by using transgenic mice expressing zona pellucida 3 (Zp3) promoter-mediated Cre recombinase. Our results show that Pten was efficiently deleted from oocytes of primary and further developed follicles, as indicated by the elevated phosphorylation of the major PI3K downstream component Akt. However, follicular development was not altered and oocyte maturation was also normal, which led to normal fertility with unaltered litter size in the mutant mice. Our data indicate that properly controlled PTEN/PI3K-Akt signaling in oocytes is essential for control of the development of primordial follicles whereas overactivation of PI3K signaling in oocytes does not appear to affect the development of growing follicles. This suggests that there is a stage-specific function of PTEN/PI3K signaling in mouse oocytes that controls follicular activation.

In humans, the molecular mechanisms underlying ovarian follicle endowment and activation, which are closely related to the control of female reproduction, occurrence of menopause, and related diseases such as premature ovarian failure, are poorly understood. In the current study, we provide several lines of genetic evidence that the cyclin-dependent kinase (Cdk) inhibitor 1B (commonly known as p27^kip1 or p27) controls ovarian development in mice by suppressing follicle endowment and activation, and by promoting follicle death. In p27-deficient (p27^−/−) mice, postnatal follicle assembly was accelerated, and the number of endowed follicles was doubled as compared with p27^+/+ mice. Moreover, in p27^−/− ovaries the primordial follicle pool was prematurely activated once it was endowed, and at the same time the massive follicular death that occurs before sexual maturity was rescued by loss of p27. In early adulthood, however, the overactivated follicular pool in p27^−/− ovaries was largely depleted, causing premature ovarian failure. Furthermore, we have extensively studied the molecular mechanisms underlying the above-mentioned phenotypes seen in p27^−/− ovaries and have found that p27 controls follicular development by several distinct mechanisms at different stages of development of the ovary. For example, p27 controls oocyte growth by suppressing the functions of Cdk2/Cdc2-cyclin A/E1 in oocytes that are arrested at the diplotene stage of meiosis I. This function of p27 is distinct from its well-known role as a suppressor of cell cycle progression. In addition, we have found that p27 activates the caspase-9-caspase-3-caspase-7-poly (ADP-ribose) polymeraseapoptotic cascade by inhibiting Cdk2/Cdc2-cyclin A/B1 kinase activities in follicles, thereby inducing follicle atresia. Our results suggest that the p27 gene is important in determining mammalian ovarian development. This study therefore provides insight into ovary-borne genetic aberrations that cause defects in folliculogenesis and infertility in humans.