结节性硬化症(TSC)表现为涉及肺部、肾脏、大脑和心脏的多系统低等级肿瘤。淋巴管平滑肌瘤病(LAM)是一种逐渐恶化的肺部疾病，几乎只影响女性。TSC和LAM都由诱导mTORC1高度活化的TSC1和TSC2基因突变引起。此处，我们报道LAM肺的单细胞RNA测序发现了鞘脂生物合成通路的基因激活。相应地，鞘脂和酰胺代谢的关键酶酸性酰胺酶(ASAH1)和二氢酰胺脱氢酶(DeGS1)的表达在TSC2缺失细胞中显著增加。TSC2负调控肿瘤形成鞘脂的生物合成，用shRNA或抑制剂ARN14976 (17a) 抑制ASAH1显著降低TSC2缺失细胞的存活率。在体内，17a显著减少了TSC2缺失细胞来源的小鼠异种移植瘤的生长和TSC2缺失细胞的短期肺部殖株。联合雷帕霉素和17a治疗对Tsc2+/-小鼠的肾囊腺瘤生长产生协同作用，与增加的ASAH1表达和活性无关。综上，本研究发现TSC2缺失细胞和肿瘤中的拉帕霉素不敏感ASAH1上调，并提供了证据表明靶向异常鞘脂生物合成途径在mTORC1高度活化的肿瘤治疗中具有潜在疗效，包括TSC和LAM。

Tuberous Sclerosis Complex (TSC) is characterized by multi-system low-grade neoplasia involving the lung, kidneys, brain, and heart. Lymphangioleiomyomatosis (LAM) is a progressive pulmonary disease affecting almost exclusively women. TSC and LAM are both caused by mutations in TSC1 and TSC2 that results in mTORC1 hyperactivation. Here, we report that single-cell RNA sequencing of LAM lungs identified activation of genes in the sphingolipid biosynthesis pathway. Accordingly, the expression of acid ceramidase (ASAH1) and dihydroceramide desaturase (DEGS1), key enzymes controlling sphingolipid and ceramide metabolism, was significantly increased in TSC2-null cells. TSC2 negatively regulated the biosynthesis of tumorigenic sphingolipids, and suppression of ASAH1 by shRNA or the inhibitor ARN14976 (17a) resulted in markedly decreased TSC2-null cell viability. In vivo, 17a significantly decreased the growth of TSC2-null cell derived mouse xenografts and short-term lung colonization by TSC2-null cells. Combined rapamycin and 17a treatment synergistically inhibited renal cystadenoma growth in Tsc2+/- mice, consistent with increased ASAH1 expression and activity being rapamycin insensitive. Collectively, the present study identifies rapamycin-insensitive ASAH1 upregulation in TSC2-null cells and tumors and provides evidence that targeting aberrant sphingolipid biosynthesis pathways has potential therapeutic value in mTORC1-hyperactive neoplasms including TSC and LAM.