Spindle cell/sclerosing rhabdomyosarcoma (ssRMS) is a rare subtype of rhabdomyosarcoma (RMS) that has fascicular spindle cell and/or sclerosing morphology. SsRMS has a diverse molecular background and is categorized into three groups: congenital/infantile ssRMS with a gene fusion involving the NCOA2 and VGLL2, ssRMS with the MYOD1 mutation, and ssRMS with no recurrent identifiable genetic alterations. Because ssRMS is a newly defined disease concept of RMS, the optimal treatment methods have not been determined. This results in unfavorable prognosis and consequently signals the urgent need for continuous research. Patient-derived cell lines are essential tools in basic and translational research. However, only two ssRMS cell lines with the MYOD1 mutation have been reported to date. Thus, we established a novel ssRMS cell line named NCC-ssRMS2-C1 using a surgically resected tumor tissue from an adult ssRMS patient. NCC-ssRMS2-C1 cells retained the copy number alterations corresponding to the original tumor and are categorized into the group with no recurrent identifiable genetic alterations. NCC-ssRMS2-C1 cells demonstrated constant proliferation, spheroid formation, and capability for invasion in vitro, reflecting the malignant features of the original tumor tissue. In a drug screening test, ssRMS demonstrated remarkable sensitivity to romidepsin, trabectedin, actinomycin D, and bortezomib. Hence, we conclude that the NCC-ssRMS2-C1 cell line is the first ssRMS cell line which belongs to the group with no recurrent identifiable genetic alterations, and it will be a useful resource in both basic and translational studies for ssRMS.

梭形细胞/硬化性横纹肌肉瘤 (ssRMS) 是一种罕见的横纹肌肉瘤 (RMS) 亚型，具有束状梭形细胞和/或硬化形态。SsRMS 具有不同的分子背景，分为三组：先天性/婴儿 ssRMS 具有涉及NCOA2和VGLL2的基因融合，ssRMS 具有MYOD1突变，以及 ssRMS 没有复发性可识别的遗传改变。由于 ssRMS 是 RMS 新定义的疾病概念，因此尚未确定最佳治疗方法。这导致不利的预后，因此表明迫切需要继续研究。源自患者的细胞系是基础研究和转化研究中必不可少的工具。然而，只有两个 ssRMS 细胞系与MYOD1迄今为止已经报道了突变。因此，我们使用从成年 ssRMS 患者手术切除的肿瘤组织建立了一种名为 NCC-ssRMS2-C1 的新型 ssRMS 细胞系。NCC-ssRMS2-C1 细胞保留了对应于原始肿瘤的拷贝数改变，并被归类为没有复发性可识别遗传改变的组。NCC-ssRMS2-C1 细胞在体外表现出持续增殖、球体形成和侵袭能力，反映了原始肿瘤组织的恶性特征。在药物筛选试验中，ssRMS 显示出对罗米地辛、曲贝替定、放线菌素 D 和硼替佐米的显着敏感性。因此，我们得出结论，NCC-ssRMS2-C1 细胞系是第一个 ssRMS 细胞系，它属于没有复发性可识别遗传改变的组，