Division of Pediatric Hematology/Oncology, Department of Pediatrics, Oregon Health and Science University (OHSU), Portland, Oregon 97239, USA.
Department of Pathology, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA.
Cold Spring Harb Mol Case Stud. 2022 Jan 10;8(1). doi: 10.1101/mcs.a006140. Print 2022 Jan.
Spindle cell/sclerosing rhabdomyosarcoma (ssRMS) is a rare subtype of rhabdomyosarcoma, commonly harboring a gain-of-function L122R mutation in the muscle-specific master transcription factor MYOD1. -mutated ssRMS is almost invariably fatal, and development of novel therapeutic approaches based on the biology of the disease is urgently needed. MYOD1 L122R affects the DNA-binding domain and is believed to confer MYC-like properties to MYOD1, driving oncogenesis. Moreover, the majority of the -mutated ssRMS harbor additional alterations activating the PI3K/AKT pathway. It is postulated that the PI3K/AKT pathway cooperates with MYOD1 L122R. To address this biological entity, we established and characterized a new patient-derived ssRMS cell line OHSU-SARC001, harboring MYOD1 L122R as well as alterations in , , and We explored the functional impact of these aberrations on oncogenic signaling with gain-of-function experiments in C2C12 murine muscle lineage cells. These data reveal that PIK3CA, the novel PIK3CA variant discovered in this patient specimen, is a constitutively active kinase, albeit to a lesser extent than PI3KCA, a hotspot oncogenic mutation. Furthermore, we examined the effectiveness of molecularly targeted PI3K/AKT/mTOR and RAS/MAPK inhibitors to block oncogenic signaling and suppress the growth of OHSU-SARC001 cells. Dual PI3K/mTOR (LY3023414, bimiralisib) and AKT inhibitors (ipatasertib, afuresertib) induced dose-dependent reductions in cell growth. However, mTOR-selective inhibitors (everolimus, rapamycin) alone did not exert cytotoxic effects. The MEK1/2 inhibitor trametinib did not impact proliferation even at the highest doses tested. Our data suggest that molecularly targeted strategies may be effective in PI3K/AKT/mTOR-activated ssRMS. Taken together, these data highlight the importance of utilizing patient-derived models to assess molecularly targetable treatments and their potential as future treatment options.
纺锤体细胞/硬化性横纹肌肉瘤（ssRMS）是一种罕见的横纹肌肉瘤亚型，通常在肌肉特异性主转录因子 MYOD1 中存在功能获得性 L122R 突变。-突变的 ssRMS 几乎总是致命的，迫切需要基于疾病生物学开发新的治疗方法。MYOD1 L122R 影响 DNA 结合域，据信使 MYOD1 具有 MYC 样特性，从而驱动肿瘤发生。此外，大多数 -突变的 ssRMS 还具有激活 PI3K/AKT 途径的其他改变。据推测，PI3K/AKT 途径与 MYOD1 L122R 合作。为了解决这个生物学实体，我们建立并表征了一个新的患者来源的 ssRMS 细胞系 OHSU-SARC001，该细胞系携带 MYOD1 L122R 以及 、 和 的改变。我们通过在 C2C12 鼠肌肉谱系细胞中进行功能获得实验，研究了这些异常对致癌信号的功能影响。这些数据表明，PI3KCA，在该患者标本中发现的新的 PIK3CA 变体，是一种组成性激活的激酶，尽管其活性低于热点致癌突变 PI3KCA。此外，我们还检查了分子靶向 PI3K/AKT/mTOR 和 RAS/MAPK 抑制剂阻断致癌信号和抑制 OHSU-SARC001 细胞生长的有效性。双重 PI3K/mTOR（LY3023414、bimiralisib）和 AKT 抑制剂（ipatasertib、afuresertib）诱导细胞生长的剂量依赖性降低。然而，单独使用 mTOR 选择性抑制剂（everolimus、rapamycin）并没有产生细胞毒性作用。即使在测试的最高剂量下，MEK1/2 抑制剂 trametinib 也不会影响增殖。我们的数据表明，分子靶向策略可能对 PI3K/AKT/mTOR 激活的 ssRMS 有效。总之，这些数据强调了利用患者来源的模型来评估分子靶向治疗及其作为未来治疗选择的潜力的重要性。
