Proapoptotic protein Bim attenuates estrogen-enhanced survival in lymphangioleiomyomatosis
Chenggang Li, … , Elizabeth P. Henske, Jane J. Yu
Chenggang Li, … , Elizabeth P. Henske, Jane J. Yu
Published November 17, 2016
Citation Information: JCI Insight. 2016;1(19):e86629. https://doi.org/10.1172/jci.insight.86629.
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Research Article Cell biology Oncology

Proapoptotic protein Bim attenuates estrogen-enhanced survival in lymphangioleiomyomatosis

Abstract

Lymphangioleiomyomatosis (LAM) is a progressive lung disease that primarily affects young women. Genetic evidence suggests that LAM cells bearing TSC2 mutations migrate to the lungs, proliferate, and cause cystic remodeling. The female predominance indicates that estrogen plays a critical role in LAM pathogenesis, and we have proposed that estrogen promotes LAM cell metastasis by inhibition of anoikis. We report here that estrogen increased LAM patient–derived cells’ resistance to anoikis in vitro, accompanied by decreased accumulation of the proapoptotic protein Bim, an activator of anoikis. The resistance to anoikis was reversed by the proteasome inhibitor, bortezomib. Treatment of LAM patient–derived cells with estrogen plus bortezomib promoted anoikis compared with estrogen alone. Depletion of Bim by siRNA in TSC2-deficient cells resulted in anoikis resistance. Treatment of mice with bortezomib reduced estrogen-promoted lung colonization of TSC2-deficient cells. Importantly, molecular depletion of Bim by siRNA in Tsc2-deficient cells increased lung colonization in a mouse model. Collectively, these data indicate that Bim plays a key role in estrogen-enhanced survival of LAM patient–derived cells under detached conditions that occur with dissemination. Thus, targeting Bim may be a plausible future treatment strategy in patients with LAM.

Authors

Chenggang Li, Na Li, Xiaolei Liu, Erik Y. Zhang, Yang Sun, Kouhei Masuda, Jing Li, Julia Sun, Tasha Morrison, Xiangke Li, Yuanguang Chen, Jiang Wang, Nagla A. Karim, Yi Zhang, John Blenis, Mauricio J. Reginato, Elizabeth P. Henske, Jane J. Yu

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Figure 1

Estrogen decreases Bim expression in detached ELT3 cells and 621-101 cells.

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Estrogen decreases Bim expression in detached ELT3 cells and 621-101 cel...
(A) Tsc2-deficient rat uterine leiomyoma-derived (ELT3) cells (upper panels) and TSC2-deficient LAM patient–derived cells (621-101 cells) (lower panels) were seeded in poly-HEMA–coated plates, and treated with 10 nM 17-β-estradiol (E2) for 24 hours. Cells were stained with a BD Annexin V: FITC Apoptosis Detection Kit I. Anoikis was determined by flow cytometry (BD FACSCanto II). Annexin V+PI+ indicated cells undergoing anoikis (n = 3). (B) Immunoblotting analysis of Bim levels in ELT3 cells treated with E2 for indicated periods. (C) 621-101 cells were treated with 10 nM E2 or vehicle control for 24 hours in detachment conditions. Cleaved caspase 3 was used as an additional cell death marker. (D) 621-101 cells were treated with 10 nM E2 for 5, 15, and 30 minutes in detachment conditions. Immunoblotting analyses of Bim, phospho-Erk1/2, Erk1/2, and cleaved PARP were performed. In B–D, β-actin was used as a loading control; Bim levels were quantified using densitometry, and normalized to β-actin. Results are representative of 3 experiments. Statistical analysis performed using an unpaired, 2-tailed Student’s t test. **P < 0.01 was considered significant.