Estradiol and tamoxifen stimulate LAM-associated angiomyolipoma cell growth and activate both genomic and nongenomic signaling pathways

Lymphangioleiomyomatosis (LAM) is a progressive lung disease affecting almost exclusively women. The reasons for this strong gender predisposition are poorly understood. Renal angiomyolipomas occur in 50-60% of sporadic LAM patients. The smooth muscle cells of pulmonary LAM and renal angiomyolipomas are nearly indistinguishable morphologically. Here, we report the first successful cell culture of a LAM-associated renal angiomyolipoma. The cells carried inactivating mutations in both alleles of the TSC2 gene and expressed estrogen receptor alpha, estrogen receptor beta, and androgen receptor. To elucidate the cellular pathways through which steroid hormones influence LAM pathogenesis, we treated the cells with both estradiol and tamoxifen. Cell growth was stimulated by estradiol, associated with phosphorylation of p44/42 MAPK at 5 min and an increase in c-myc expression at 4 h. Tamoxifen citrate also stimulated cell growth, associated with increased phosphorylation of p44/42 MAPK and expression of c-myc, indicating that tamoxifen has agonist effects on angiomyolipoma cells. This response to tamoxifen in human angiomyolipoma cells differs from prior studies of Eker rat leiomyoma cells, possibly reflecting cell type or species differences in cells lacking tuberin. Our data provide the first evidence that estradiol stimulates the growth of angiomyolipoma cells, that tamoxifen has agonist effects in angiomyolipoma cells, and that estradiol and tamoxifen impact both genomic and nongenomic signaling pathways in angiomyolipoma cells. The responsiveness of angiomyolipoma cells to estradiol may be related to the underlying reasons that LAM affects primarily women.