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

项目摘要 顺铂是最有效和最广泛使用的抗癌药物之一。对于小细胞肺癌（SCLC）， 目前基于铂的标准治疗三十多年来没有改变。稳健的初始临床 通常在SCLC患者中观察到缓解，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SCLC细胞如何产生顺铂， 耐药性，精确的机制仍然难以捉摸。 作为我们破译化学抗性机制的更大努力的一部分， shRNA筛选并鉴定微管相关丝氨酸/苏氨酸激酶1（MAST 1）为"合成的 顺铂在SCLC中的"致命"伙伴。使用SCLC细胞系和患者来源的肿瘤（PDX），我们 表明MAST 1敲低使ASCL1-高SCLC细胞对顺铂治疗在体外和体内敏感。 vivo. CCLE数据库的挖掘进一步显示MAST 1在ASCL1高亚型SCLC中表达升高 并且与ASCL1高SCLC细胞系中的顺铂抗性正相关。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和稳定NFIB蛋白， 与疾病进展相关的SCLC驱动因子，以促进MAST 1表达。事实上，NFIB的击倒 阻断顺铂诱导的MAST 1，表明MAST 1可能是SCLC中NFIB的下游靶点。 此外，为了鉴定MAST 1的潜在下游效应物，其有助于顺铂耐药。 SCLC，我们进行了基于质谱的蛋白质组学研究，并确定PLK1作为潜在的结合 MAST1的合作伙伴。体外激酶试验表明MAST 1直接磷酸化PLK 1激活位点 T210这些发现将MAST 1确定为克服SCLC中顺铂耐药性的有希望的靶点。 然而，目前没有靶向MAST 1的小分子药物可用。因此，我们使用了一种"药物 重新利用"策略，并将临床试验阶段的激酶抑制剂来鲁替尼鉴定为新型MAST 1抑制剂。 来鲁替尼在SCLC细胞系和PDX模型中显著恢复顺铂敏感性，毒性最小。 我们的中心假设是顺铂稳定NFIB蛋白以促进MAST1-PLK1信号传导，导致 顺铂耐药。因此，靶向MAST1-PLK1信号传导代表了有希望的抗SCLC靶点 与顺铂联合，特别是用于ASCL1-高亚型SCLC。我们将测试我们的假设，通过 以下目的：（1）确定顺铂是否以及如何稳定NFIB以促进MAST 1表达， 从而导致SCLC中顺铂耐药。(2)确定MAST 1是否赋予顺铂耐药性 通过激活PLK1和促进细胞周期进程，顺铂的存在下，小细胞肺癌。(3)验证 NFIB-MAST 1-PLK 1轴作为顺铂耐药SCLC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.