Background Inhibition of ChK1 appears as a promising strategy for selectively potentiate the efficacy of chemotherapeutic agents in G1 checkpoint-defective tumor cells such as those that lack functional p53 protein. The p53 pathway is commonly dysregulated in soft-tissue sarcomas (STS) through mutations affecting TP53 or MDM2 amplification. GDC-0575 is a selective ATP-competitive inhibitor of CHK1. Methods We have performed a systematic screening of a panel of 10 STS cell lines by combining the treatment of GDC-0575 with chemotherapy. Cell proliferation, cell death and cell cycle analysis were evaluated with high throughput assay. In vivo experiments were carried out by using TP53-mutated and TP53 wild-type patient-derived xenograft models of STS. Clinical activity of GDC-0575 combined with chemotherapy in patients with TP53-mutated and TP53 wild-type STS was also assessed. Results We found that GDC-0575 abrogated DNA damage-induced S and G2-M checkpoints, exacerbated DNA double-strand breaks and induced apoptosis in STS cells. Moreover, we observed a synergistic or additive effect of GDC-0575 together with gemcitabine in vitro and in vivo in TP53-proficient but not TP53-deficient sarcoma models. In a phase I study of GDC-0575 in combination with gemcitabine, two patients with metastatic TP53-mutated STS had an exceptional, long-lasting response despite administration of a very low dose of gemcitabine whereas one patient with wild-type TP53 STS had no clinical benefit. Genetic profiling of samples from a patient displaying secondary resistance after 1 year showed loss of one preexisting loss-of-function mutation in the helical domain of DNA2. Conclusion We provide the first preclinical and clinical evidence that potentiation of chemotherapy activity with a CHK1 inhibitor is a promising strategy in TP53-deficient STS and deserves further investigation in the phase II setting.

中文翻译：

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CHK1在软组织肉瘤中的抑制作用：生物学和临床意义。

背景抑制ChK1似乎是一种有前途的策略，可以选择性地增强G1检查点缺陷型肿瘤细胞（例如缺乏功能性p53蛋白的细胞）中化疗药物的功效。p53途径通常通过影响TP53或MDM2扩增的突变而在软组织肉瘤（STS）中失调。GDC-0575是CHK1的选择性ATP竞争性抑制剂。方法我们通过结合GDC-0575的治疗和化学疗法，对一组10个STS细胞系进行了系统的筛选。用高通量测定法评估细胞增殖，细胞死亡和细胞周期分析。通过使用TP53突变和TP53野生型患者来源的STS异种移植模型进行体内实验。还评估了GDC-0575联合化疗对TP53突变和TP53野生型STS患者的临床活性。结果我们发现，GDC-0575废除了DNA损伤诱导的S和G2-M检查点，加剧了DNA双链断裂，并诱导了STS细胞凋亡。此外，我们在TP53阳性但不是TP53缺失的肉瘤模型中观察到了GDC-0575与吉西他滨的协同作用或累加作用。在GDC-0575与吉西他滨联合进行的I期研究中，尽管给予了极低剂量的吉西他滨，但两名转移性TP53突变的STS患者仍表现出异常而持久的应答，而一名野生型TP53 STS的患者则没有临床受益。一位患者在一年后表现出继发性抗药性的样品的基因分析表明，DNA2螺旋结构域中丢失了一个先前存在的功能丧失突变。结论我们提供了首个临床前和临床证据，即在TP53缺失的STS中用CHK1抑制剂增强化疗活性是一种有前途的策略，值得在II期研究中进行进一步的研究。