Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts.
Broad Institute of MIT and Harvard, Cambridge, Massachusetts.
Clin Cancer Res. 2023 Dec 15;29(24):5128-5139. doi: 10.1158/1078-0432.CCR-23-0998.
Leiomyosarcoma (LMS) is an aggressive sarcoma for which standard chemotherapies achieve response rates under 30%. There are no effective targeted therapies against LMS. Most LMS are characterized by chromosomal instability (CIN), resulting in part from TP53 and RB1 co-inactivation and DNA damage repair defects. We sought to identify therapeutic targets that could exacerbate intrinsic CIN and DNA damage in LMS, inducing lethal genotoxicity.
We performed clinical targeted sequencing in 287 LMS and genome-wide loss-of-function screens in 3 patient-derived LMS cell lines, to identify LMS-specific dependencies. We validated candidate targets by biochemical and cell-response assays in vitro and in seven mouse models.
Clinical targeted sequencing revealed a high burden of somatic copy-number alterations (median fraction of the genome altered =0.62) and demonstrated homologous recombination deficiency signatures in 35% of LMS. Genome-wide short hairpin RNA screens demonstrated PRKDC (DNA-PKcs) and RPA2 essentiality, consistent with compensatory nonhomologous end joining (NHEJ) hyper-dependence. DNA-PK inhibitor combinations with unconventionally low-dose doxorubicin had synergistic activity in LMS in vitro models. Combination therapy with peposertib and low-dose doxorubicin (standard or liposomal formulations) inhibited growth of 5 of 7 LMS mouse models without toxicity.
Combinations of DNA-PK inhibitors with unconventionally low, sensitizing, doxorubicin dosing showed synergistic effects in LMS in vitro and in vivo models, without discernable toxicity. These findings underscore the relevance of DNA damage repair alterations in LMS pathogenesis and identify dependence on NHEJ as a clinically actionable vulnerability in LMS.
平滑肌肉瘤（LMS）是一种侵袭性肉瘤，标准化疗的缓解率低于 30%。目前尚无针对 LMS 的有效靶向治疗方法。大多数 LMS 的特点是染色体不稳定性（CIN），部分原因是 TP53 和 RB1 共失活和 DNA 损伤修复缺陷。我们试图寻找能够加剧 LMS 固有 CIN 和 DNA 损伤的治疗靶点，从而诱导致命的遗传毒性。
我们对 287 例 LMS 进行了临床靶向测序，并对 3 例患者来源的 LMS 细胞系进行了全基因组功能丧失筛选，以鉴定 LMS 特异性依赖性。我们通过体外和在 7 种小鼠模型中的生化和细胞反应测定验证了候选靶点。
临床靶向测序显示体细胞拷贝数改变负担高（改变的基因组部分中位数=0.62），并在 35%的 LMS 中显示同源重组缺陷特征。全基因组短发夹 RNA 筛选表明 PRKDC（DNA-PKcs）和 RPA2 是必需的，与代偿性非同源末端连接（NHEJ）过度依赖一致。在体外 LMS 模型中，DNA-PK 抑制剂联合低剂量阿霉素具有协同作用。与低剂量阿霉素（标准或脂质体制剂）联合使用 peposertib 抑制了 7 种 LMS 小鼠模型中的 5 种模型的生长，且没有毒性。
DNA-PK 抑制剂与非传统低剂量、增敏阿霉素联合用药在体外和体内 LMS 模型中具有协同作用，且无明显毒性。这些发现强调了 DNA 损伤修复改变在 LMS 发病机制中的相关性，并确定了 NHEJ 依赖作为 LMS 临床可操作的弱点。
