The role of NFIB-MAST1 signaling in mediating adaptive cisplatin resistance in SCLC

项目总结 顺铂是目前最有效、应用最广泛的抗癌药物之一。小细胞肺癌(SCLC) 目前以铂为基础的标准治疗已经三十多年没有改变了。强健的初始临床 通常在小细胞肺癌患者中观察到反应，但大多数患者死于化疗耐药。 复发。尽管已经做出了巨大的努力来了解小细胞肺癌细胞是如何发展成顺铂的 尽管存在耐药性，但确切的机制仍然难以捉摸。 作为我们破译化疗耐药机制的更大努力的一部分，我们使用了一个广泛的染色体。 微管相关丝氨酸/苏氨酸激酶1(MAST1)的shRNA筛选及鉴定 顺铂在小细胞肺癌中的致命伙伴。使用小细胞肺癌细胞系和患者来源的肿瘤(PDX)，我们有 MAST1基因敲除使ASCL1高表达的小细胞肺癌细胞对顺铂增敏 活着。对CCLE数据库的挖掘进一步表明MAST1在ASCL1高亚型SCLC中的表达上调 且与ASCL1高表达的小细胞肺癌细胞株对顺铂的耐药性呈正相关。通过转录因子 分析和无偏数据挖掘，我们发现顺铂物理结合并稳定NFIB蛋白，a SCLC驱动与疾病进展相关，促进MAST1的表达。事实上，击倒NFIB 阻断顺铂诱导的MAST1，提示MAST1可能是NFIB在小细胞肺癌中的下游靶点。 此外，为了确定MAST1可能导致顺铂耐药的下游效应因子， 我们进行了基于质谱学的蛋白质组学研究，并确定PLK1是一个潜在的结合 MAST1的合作伙伴。体外激酶实验证实MAST1直接磷酸化PLK1激活位点 T210。这些发现表明，MAST1是克服小细胞肺癌顺铂耐药的一个有希望的靶点。 然而，目前还没有针对MAST1的小分子药物。因此，我们使用了一种“药物” 重新调整用途“策略，并确定临床试验阶段的激酶抑制剂来妥替尼是一种新的MAST1抑制剂。 Lestaurtinib以最小的毒性显著恢复了SCLC细胞系和PDX模型对顺铂的敏感性。 我们的中心假设是顺铂稳定NFIB蛋白以促进MAST1-PLK1信号转导，导致 小细胞肺癌对顺铂的耐药性。因此，靶向MAST1-PLK1信号代表了一个很有前途的抗小细胞肺癌靶点 与顺铂联合应用，特别是对ASCL1高亚型小细胞肺癌。我们将通过以下方式测试我们的假设 目的：(1)确定顺铂是否以及如何稳定NFIB以促进MAST1的表达和 从而导致小细胞肺癌对顺铂耐药。(2)确定MAST1是否产生顺铂耐药 在顺铂存在的情况下，通过激活PLK1和促进细胞周期进程而诱导小细胞肺癌的发生。(3)验证 NFIB-MAST1-PLK1轴作为顺铂耐药小细胞肺癌的治疗靶点。

PROJECT SUMMARY Cisplatin is one of the most effective and widely used anti-cancer drugs. For small cell lung cancer (SCLC), the current platinum-based standard treatment has not changed for more than three decades. Robust initial clinical response is usually observed in SCLC patients but the majority of patients succumb to chemoresistant recurrence. Despite tremendous efforts have been made to understand how SCLC cells develop cisplatin resistance, the precise mechanism remains elusive. As a part of our larger effort to decipher the mechanism of chemo-resistance, we employed a kinome wide shRNA screening and identified microtubule-associated serine/threonine kinase 1 (MAST1) as a “synthetic lethal” partner of cisplatin in SCLC. Using both SCLC cell lines and patient-derived tumors (PDX), we have demonstrated that MAST1 knockdown sensitizes ASCL1-high SCLC cells to cisplatin treatment in vitro and in vivo. Mining of CCLE database further shows that MAST1 expression is elevated in ASCL1-high subtype SCLC and positively correlates with cisplatin resistance in ASCL1-high SCLC cell lines. Through transcription factor profiling and unbiased datamining, we discovered that cisplatin physically binds and stabilize NFIB protein, a SCLC driver associated with disease progression, to promote MAST1 expression. Indeed, knockdown of NFIB blocked MAST1 induction by cisplatin, suggesting that MAST1 may be a downstream target of NFIB in SCLC. In addition, to identify the potential downstream effectors of MAST1 that contributes to cisplatin resistance in SCLC, we performed mass spectrometry-based proteomic studies and identified PLK1 as a potential binding partner of MAST1. In vitro kinase assay demonstrated that MAST1 directly phosphorylates PLK1 activation site T210. These findings identified MAST1 as a promising target to overcome cisplatin resistance in SCLC. However, no small molecule drug targeting MAST1 is currently available. Thus, we employed a “drug repurposing” strategy and identified clinical trial-staged kinase inhibitor lestaurtinib as a novel MAST1 inhibitor. Lestaurtinib significantly restored cisplatin sensitivity in SCLC cell lines and PDX models with minimal toxicity. Our central hypothesis is that cisplatin stabilizes NFIB protein to promote MAST1-PLK1 signaling, leading to cisplatin resistance in SCLC. Thus, targeting MAST1-PLK1 signaling represents a promising anti-SCLC target in combination with cisplatin, particularly for ASCL1-high subtype SCLC. We will test our hypothesis through the following aims: (1) To determine whether and how cisplatin stabilizes NFIB to promote MAST1 expression and consequently lead to cisplatin resistance in SCLC. (2) To determine whether MAST1 confers cisplatin resistance to SCLC by activating PLK1 and promoting cell cycle progression in the presence of cisplatin. (3) To validate NFIB-MAST1-PLK1 axis as a therapeutic target for cisplatin-resistant SCLC.