Androgens, although traditionally thought to be male sex steroids, play important roles in female reproduction, both in healthy and pathological states. This mini-review focuses on recent advances in our knowledge of the role of androgens in the ovary. Androgen receptor (AR) is expressed in oocytes, granulosa cells, and theca cells, and is temporally regulated during follicular development. Mouse knockout studies have shown that AR expression in granulosa cells is critical for normal follicular development and subsequent ovulation. In addition, androgens are involved in regulating dynamic changes in ovarian steroidogenesis that are critical for normal cycling. Androgen effects on follicle development have been incorporated into clinical practice in women with diminished ovarian reserve, albeit with limited success in available literature. At the other extreme, androgen excess leads to disordered follicle development and anovulatory infertility known as polycystic ovary syndrome (PCOS), with studies suggesting that theca cell AR may mediate many of these negative effects. Finally, both prenatal and postnatal animal models of androgen excess have been developed and are being used to study the pathophysiology of PCOS both within the ovary and with regard to overall metabolic health. Taken together, current scientific consensus is that a careful balance of androgen activity in the ovary is necessary for reproductive health in women.

Chronic inflammation promotes progression of many cancers, with circulating myeloid-derived suppressor cell (MDSC) levels correlating with poor prognosis. Here we examine effects of MDSCs on lymphangioleiomyomatosis (LAM), a rare disease occurring almost exclusively in women whereby estrogen-sensitive metastatic TSC2-null tumors grow throughout the lungs, markedly reducing pulmonary function. The LAM cell origin remains unknown; however, previous work demonstrated that Tsc2 inactivation in the mouse uterus induced estrogen-dependent myometrial tumors with nearly all features of LAM. Half of these animals developed metastatic myometrial tumors in the lungs, suggesting that LAM cells might originate from the myometrium, possibly explaining its overwhelming female prevalence and estrogen-sensitivity. Here we report that MDSC levels, and in particular granulocytic myeloid cell levels, are elevated in the periphery and in tumors of uterine-specific Tsc2-null mice. Importantly, MDSC depletion or inhibition of their recruitment impairs myometrial tumor growth. RNA and protein analysis of Tsc2-null myometrial tumors and xenografts demonstrate high expression and activity of the serine protease neutrophil elastase (NE), with selective qPCR studies indicating a stromal origin of the NE. Notably, treatment with sivelestat, a known NE inhibitor already approved for human use in some countries, reduces tumor growth similar to MDSC depletion. Furthermore, NE promotes Tsc2-null tumor cell growth, migration, and invasion in vitro. Finally, NE-expressing myeloid cells are present throughout the lungs of LAM patients but not controls. These data suggest that NE derived from granulocytic myeloid cells might directly promote LAM tumor cell progression and could be a novel therapeutic target for LAM.

No abstract

Lymphangioleiomyomatosis (LAM) is a rare cystic lung disease caused by smooth muscle cell-like tumors containing tuberous sclerosis (TSC) gene mutations and found almost exclusively in females. Patient studies suggest LAM progression is estrogen-dependent, an observation supported by in vivo mouse models. However, in vitro data using TSC-null cells lines demonstrate modest estradiol responses, suggesting estradiol effects in vivo may involve pathways independent of direct tumor stimulation. We previously reported tumor-dependent neutrophil expansion and promotion of TSC2-null tumor growth in an estradiol-sensitive LAM mouse model. We therefore hypothesized that estradiol stimulates tumor growth in part by promoting neutrophil production. Here we report that estradiol-enhanced lung colonization of TSC2-null cells is indeed dependent on neutrophils. We demonstrate that estradiol induces granulopoiesis via ERα in male and female bone marrow cultures. With our novel TSC2-null mouse myometrial cell line, we show that factors released from these cells drive estradiol-sensitive neutrophil production. Lastly, we analyzed single-cell RNA sequencing data from LAM patients and demonstrate the presence of tumor-activated neutrophils. Our data suggest a powerful positive feedback loop whereby estradiol and tumor factors induce neutrophil expansion, which in turn intensifies tumor growth and production of neutrophil-stimulating factors, resulting in continued TSC2-null tumor growth.

Predominately affecting women of reproductive age, lymphangioleiomyomatosis (LAM) is a rare lung disease characterized by slowly growing, estrogen-sensitive metastatic smooth muscle cell-like adenomas that result in cystic lung changes and loss of pulmonary function. We have previously reported that estrogen is required to maintain LAM-like tumor progression in a uterine-specific Tsc2-knockout murine model. Interestingly, the observed estrogen sensitivity in vivo is more markedly pronounced than that of our estrogen receptor-positive TSC2-null cells when stimulated with estradiol (E2) in vitro, suggesting that estradiol may act elsewhere to promote LAM progression. We hypothesized that, in addition to direct effects of estrogen on tumor cells, estrogen might also stimulate tumor growth by promoting polymorphonuclear cell (PMN) production in the bone marrow and actions in the tumor microenvironment. Here, using bone marrow cultures, we demonstrate that estradiol is a potent inducer of PMN production. This effect occurs equally with both male and female bone marrow. Employing both pharmacologic agents and bone marrow from ER_ knockout mice, we showed that ER_ is necessary for promoting a PMN fate for myeloid progenitors. While we see that the migratory and invasive capacities of TSC2-null cell lines are not augmented when stimulated with E2 directly, evidence shows estrogen promotes the pro-tumorigenic function of PMNs co-cultured with TSC2-null cell lines. These data provide insight into the robust effect of in vivo estrogen stimulation as estradiol may be a dual effector in LAM tumor progression and great target for anti-LAM therapeutic strategy.