Estrogen Receptor α (ERα) Signaling and Tumor Cell-Derived Factors Mediate Pro-Tumor Neutrophil Activation in the Setting of Lymphangioleiomyomatosis (LAM)

Lymphangioleiomyomatosis (LAM), is a rare disease characterized by the abnormal proliferation of smooth muscle-like cells containing tuberous sclerosis complex (TSC) gene mutations. This proliferation leads to tumor formation and cyst development in the lung parenchyma, resulting in declining respiratory function. Notably, LAM primarily affects biological females and appears to be estrogen-sensitive. Recent work from our laboratory suggests that estradiol not only stimulates TSC-null smooth muscle cells but also promotes neutrophil production via estrogen receptor-alpha (ERα) signaling in the bone marrow, which in turn stimulates TSC-null tumor progression. While prior studies have showed that estradiol influences tumor-induced production of leukocytes, the direct effects of ERα signaling in neutrophils are not well understood. In concert with tumor-derived factors, we hypothesized that estradiol may augment pro-tumorigenic and immunosuppressive functions of neutrophils. To address this, we employed real-time quantitative PCR to assess for ERα-mediated transcription-level expression changes in several genes associated with alternative neutrophil activation in other tumor microenvironments. Our results show that neutrophils cultured in tumor-conditioned media (TCM) require ERα for full expression of neutrophil elastase (Elane) and nitric oxide synthase 2 (Nos2) mRNA, while programmed death-ligand 1 (Cd274) mRNA expression is mediated byTMC) alone. These findings indicate that, in addition to stimulating neutrophil production in bone marrow, estradiol signaling through ERα receptors on neutrophils and tumor-derived factors significantly influences the quality of tumor-exposed neutrophil activation, promoting a pro-tumorigenic immunosuppressive phenotype.