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Lymphangioleiomyomatosis (LAM) is a rare lung disease seen almost exclusively in female sexed individuals and characterized by slowly growing, metastatic smooth muscle cell-like adenomas that cause cyst formation in the lung parenchyma and irreversible loss of pulmonary function. Given the female specificity of disease manifestation, metastatic nature, and estrogen sensitivity of LAM cells, we previously proposed that LAM cells originate in the myometrium. Our subsequent reports showed that inactivation of TSC2 in the mouse uterus results in notable LAM features in the setting of primary myometrial tumors. Additionally, we established that estrogen is required to maintain LAM-like tumor progression in a uterine-specific Tsc2-knockout murine model. However, the observed estrogen sensitivity in vivo is more markedly pronounced than that of our estrogen receptor-positive TSC2-null cells when stimulated with estradiol in vitro, suggesting that estradiol may act elsewhere in vivo to promote LAM progression. Recent immunophenotyping of LAM-like TSC2-null uterine tumors revealed preferential increase in polymorphonuclear cell (PMNs) numbers of the tumor microenvironment; we also determined that PMNs are important regulators of tumor growth. Therefore, we hypothesize that, in addition to direct effects of estrogen on tumor cells, estrogen might also stimulate tumor growth by promoting PMN production in the bone marrow and actions in the tumor microenvironment. Here, we show that estrogen availability influences PMN mobilization in naïve and tumor-burdened mice. Using bone marrow cultures and CFC assay, we demonstrate that estradiol is a potent inducer of PMN production in chronic inflammatory conditions. Employing both pharmacologic agents and estrogen receptor (ER)-null bone marrow, we showed that ERα is necessary for promoting induction of PMN fate for myeloid progenitors. While we see that the migratory, invasive, and proliferative capacities of TSC2-null cell lines are not augmented when stimulated with E2 directly, experiments are underway to assess the extent to which estrogen promotes the pro-tumorigenic function of PMNs co-cultured with TSC2-null cell lines. Together 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. Presentation: Saturday, June 11, 2022 1:00 p.m. - 1:05 p.m., Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m. |
