Department of Medicine, Oncology Division, National Jewish Health, Denver, Colorado.
Department of Medicine, University of Colorado, Denver, Colorado.
J Thorac Oncol. 2020 Sep;15(9):1522-1534. doi: 10.1016/j.jtho.2020.05.026. Epub 2020 Jun 26.
SCLC represents 15% of all lung cancer diagnoses in the United States and has a particularly poor prognosis. We hypothesized that kinases regulating SCLC survival pathways represent therapeutically targetable vulnerabilities whose inhibition may improve SCLC outcome.
A short-hairpin RNA (shRNA) library targeting all human kinases was introduced in seven chemonaive patient-derived xenografts (PDX) and the cells were cultured in vitro and in vivo. On harvest, lost or depleted shRNAs were considered as regulating-cell survival pathways and deemed essential kinases.
Unsupervised hierarchical cluster analysis of recovered shRNAs separated the PDXs into two clusters, suggesting kinase-based heterogeneity among the SCLC PDXs. A total of 23 kinases were identified as essential in two or more PDXs, with mechanistic Target of Rapamycin (mTOR) a candidate essential kinase in four. mTOR phosphorylation status correlated with PDX sensitivity to mTOR kinase inhibition, and mTOR inhibition sensitized the PDX to cisplatin and etoposide. In the PDX in which mTOR was defined as essential, mTOR inhibition caused a 43% decrease in tumor volume at 21 days (p < 0.01). Combining mTOR inhibition with cisplatin and etoposide decreased PDX tumor volume 96% compared with cisplatin and etoposide alone at 70 days (p < 0.002). Chemoresistance did not develop with the combination of mTOR inhibition and cisplatin and etoposide in mTOR-essential PDX over 105 days. The prevalence of phospho-mTOR-Ser-2448 in a tissue microarray of chemonaive SCLC was 27%, thus, identifying an important SCLC subtype that might benefit from the addition of mTOR inhibition to standard chemotherapy.
These studies reveal that kinases can define SCLC subgroups, can identify therapeutic vulnerabilities, and can potentially be used to optimize therapeutic approaches. Significance We used functional genomics to identify kinases regulating SCLC survival. mTOR was identified as essential in a subset of PDXs. mTOR inhibition decreased PDX growth, sensitized PDX to cisplatin and etoposide, and prevented chemoresistance.
小细胞肺癌（SCLC）约占美国所有肺癌诊断的 15%，预后特别差。我们假设调节 SCLC 存活途径的激酶代表了可治疗的靶向弱点，抑制这些弱点可能会改善 SCLC 的预后。
将靶向所有人类激酶的短发夹 RNA（shRNA）文库引入七种未经化疗的患者来源异种移植（PDX）中，并在体外和体内培养细胞。收获时，丢失或耗尽的 shRNA 被认为是调节细胞存活途径的，并被视为必需激酶。
未监督的层次聚类分析回收的 shRNA 将 PDX 分为两个群，表明 SCLC PDX 之间存在基于激酶的异质性。共有 23 种激酶被确定为两种或更多 PDX 中的必需激酶，其中雷帕霉素（mTOR）是四种 PDX 中的候选必需激酶。mTOR 磷酸化状态与 PDX 对 mTOR 激酶抑制的敏感性相关，mTOR 抑制使 PDX 对顺铂和依托泊苷敏感。在 mTOR 被定义为必需的 PDX 中，mTOR 抑制在 21 天内使肿瘤体积减少 43%（p < 0.01）。与顺铂和依托泊苷单独使用相比，mTOR 抑制与顺铂和依托泊苷联合使用使 PDX 肿瘤体积在 70 天内减少 96%（p < 0.002）。在 mTOR 必需 PDX 中，mTOR 抑制与顺铂和依托泊苷联合使用 105 天内未发生化疗耐药。在未经化疗的 SCLC 的组织微阵列中，磷酸化 mTOR-Ser-2448 的流行率为 27%，因此，确定了一种重要的 SCLC 亚型，可能受益于将 mTOR 抑制添加到标准化疗中。
这些研究表明，激酶可以定义 SCLC 亚群，确定治疗弱点，并可用于优化治疗方法。意义我们使用功能基因组学来鉴定调节 SCLC 存活的激酶。mTOR 被确定为一部分 PDX 的必需激酶。mTOR 抑制可降低 PDX 生长，使 PDX 对顺铂和依托泊苷敏感，并防止化疗耐药。
