Li Chenggang, Zhang Erik, Sun Yang, Lee Po-Shun, Zhan Yongzhong, Guo Yanan, Osorio Juan C, Rosas Ivan O, Xu Kai-Feng, Kwiatkowski David J, Yu Jane J
Brigham and Women's Hospital/Harvard Medical School, Boston, Massachusetts, United States of America.
Peking Union Medical College, Beijing, China.
PLoS One. 2014 Oct 27;9(10):e104809. doi: 10.1371/journal.pone.0104809. eCollection 2014.
Tuberous sclerosis syndrome (TSC) is an autosomal dominant tumor suppressor gene syndrome affecting multiple organs, including renal angiomyolipomas and pulmonary lymphangioleiomyomatosis (LAM). LAM is a female-predominant interstitial lung disease characterized by the progressive cyst formation and respiratory failure, which is also seen in sporadic patients without TSC. Mutations in TSC1 or TSC2 cause TSC, result in hyperactivation of mammalian target of rapamycin (mTOR), and are also seen in LAM cells in sporadic LAM. We recently reported that prostaglandin biosynthesis and cyclooxygenase-2 were deregulated in TSC and LAM. Phospholipase A2 (PLA2) is the rate-limiting enzyme that catalyzes the conversion of plasma membrane phospholipids into prostaglandins. In this study, we identified upregulation of adipocyte AdPLA2 (PLA2G16) in LAM nodule cells using publicly available expression data. We showed that the levels of AdPLA2 transcript and protein were higher in LAM lungs compared with control lungs. We then showed that TSC2 negatively regulates the expression of AdPLA2, and loss of TSC2 is associated with elevated production of prostaglandin E2 (PGE2) and prostacyclin (PGI2) in cell culture models. Mouse model studies also showed increased expression of AdPLA2 in xenograft tumors, estrogen-induced lung metastatic lesions of Tsc2 null leiomyoma-derived cells, and spontaneous renal cystadenomas from Tsc2+/- mice. Importantly, rapamycin treatment did not affect the expression of AdPLA2 and the production of PGE2 by TSC2-deficient mouse embryonic fibroblast (Tsc2-/-MEFs), rat uterine leiomyoma-derived ELT3 cells, and LAM patient-associated renal angiomyolipoma-derived "mesenchymal" cells. Furthermore, methyl arachidonyl fluorophosphate (MAFP), a potent irreversible PLA2 inhibitor, selectively suppressed the growth and induced apoptosis of TSC2-deficient LAM patient-derived cells relative to TSC2-addback cells. Our findings suggest that AdPLA2 plays an important role in promoting tumorigenesis and disease progression by modulating the production of prostaglandins and may serve as a potential therapeutic target in TSC and LAM.
结节性硬化症（TSC）是一种常染色体显性肿瘤抑制基因综合征，可影响多个器官，包括肾血管平滑肌脂肪瘤和肺淋巴管平滑肌瘤病（LAM）。LAM是一种以女性为主的间质性肺病，其特征为进行性囊肿形成和呼吸衰竭，在无TSC的散发性患者中也可见到。TSC1或TSC2的突变导致TSC，导致雷帕霉素哺乳动物靶标（mTOR）过度激活，在散发性LAM的LAM细胞中也可见到。我们最近报道，前列腺素生物合成和环氧化酶-2在TSC和LAM中失调。磷脂酶A2（PLA2）是催化质膜磷脂转化为前列腺素的限速酶。在本研究中，我们利用公开可用的表达数据，确定了LAM结节细胞中脂肪细胞AdPLA2（PLA2G16）的上调。我们发现，与对照肺相比，LAM肺中AdPLA2转录本和蛋白水平更高。然后我们表明，TSC2负向调节AdPLA2的表达，在细胞培养模型中，TSC2的缺失与前列腺素E2（PGE2）和前列环素（PGI2）的产生增加有关。小鼠模型研究还显示，在异种移植肿瘤、雌激素诱导的Tsc2基因敲除平滑肌瘤来源细胞的肺转移病变以及Tsc2+/-小鼠的自发性肾囊肿腺瘤中，AdPLA2表达增加。重要的是，雷帕霉素治疗不影响AdPLA2的表达以及TSC2缺陷型小鼠胚胎成纤维细胞（Tsc2-/-MEFs）、大鼠子宫平滑肌瘤来源的ELT3细胞和LAM患者相关的肾血管平滑肌脂肪瘤来源的“间充质”细胞产生PGE2。此外，甲基花生四烯酰氟磷酸酯（MAFP）是一种有效的不可逆PLA2抑制剂，相对于TSC2回补细胞，它选择性地抑制TSC2缺陷型LAM患者来源细胞的生长并诱导其凋亡。我们的研究结果表明，AdPLA2通过调节前列腺素的产生在促进肿瘤发生和疾病进展中起重要作用，可能是TSC和LAM的潜在治疗靶点。
