Pro-Oncogenic Role of LKB1 in NSCLC

LKB1 在 NSCLC 中的促癌作用

• 批准号: 8830435
• 负责人: Wei Zhou
• 金额: $ 32.16万
• 依托单位: EMORY UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-03-14 至 2017-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8830435
• 关键词: Accounting; Apoptosis; Apoptotic; Bypass; Cancer Etiology; Cancer Patient; Cancer cell line; Cell Line; Cell Proliferation; Cells; Clinical; Clinical Management; Data; Dependence; Development; Dominant-Negative Mutation; Drug resistance; Epidermal Growth Factor Receptor; Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitor; Future; Gefitinib; Generations; Genes; Growth; Health; Induced Mutation; Inhibition of Apoptosis; Lung Neoplasms; Malignant Neoplasms; Malignant neoplasm of lung; Mediating; Molecular; Mutate; Mutation; Non-Small-Cell Lung Carcinoma; Null Lymphocytes; Oncogenic; Pathway interactions; Pharmacologic Substance; Phospho-Specific Antibodies; Phosphorylation; Phosphorylation Site; Play; Proto-Oncogene Proteins c-akt; RNA; RNA Interference; Resistance; Role; STK11 gene; Signal Transduction; Site; Smoking; Stream; Testing; Tetanus Helper Peptide; Therapeutic; Threonine; Tumor Suppressor Proteins; Tyrosine Kinase Inhibitor; Xenograft procedure; attenuation; base; cancer cell; cell type; mutant; neoplastic cell; non-smoking; novel; novel therapeutic intervention; personalized medicine; pro-apoptotic protein; protein complex; response; restoration; tumor

DESCRIPTION (provided by applicant): EGFR activation mutations are frequently present in non-smoking related lung cancer. Most of these tumors are addicted to EGFR signaling and can be effectively treated with tyrosine kinase inhibitors (TKI), such as gefitinib. High sensitivity to gefitinib in lung cancer is closely correlated with dependence on AKT activation in response to EGFR signaling, and gefitinib treatment suppresses AKT activation. The restoration of AKT function was recently found to be a key step in EGFR mutant lung tumors that acquired resistance to TKI, and one potential mechanism involves the amplification of c-MET which bypasses the requirement for EGFR, rendering EGFR inhibitors ineffective. LKB1 is commonly known as a tumor suppressor because somatic LKB1 inactivation mutation is one of the most frequently mutated genes in smoking-related lung cancer. However, LKB1 mutations were rarely found in lung cancers with EGFR mutations. We have discovered a novel, potentially oncogenic role for LKB1 in lung cancers that are addicted to EGFR signaling. We found the suppression of LKB1 expression led to apoptosis in six cell lines in which either EGFR or AKT is constitutively active, but not in two cell lines without EGFR or AKT activation. More importantly, EGFR mutant cells with acquired TKI-resistance through two known mechanisms are still prone to apoptosis induced by LKB1 depletion. Mechanistically, we found that EGFR/AKT activation led to increased phosphorylation of FoxO3A at threonine 32 (Thr32) in LKB1 wild-type cells, but not in LKB1-null cells. Depletion of LKB1 in the cells with wild- type LKB1 resulted in attenuation of that phosphorylation of FoxO3A by activated EGFR/AKT, while the restoration of LKB1 function in LKB1-null cells re-established EGFR/AKT mediated FoxO3A phosphorylation. Upon expanding our analysis to other AKT targets, using three different isogenic LKB1 knockdown cell line pairs and a phospho-specific antibody microarray, we observed that there was a requirement for LKB1 in the phosphorylation of other AKT down-stream targets, including BAD (Ser136), FoxO1 (Ser319), FoxO4 (Ser197) and GSK32 (Ser9). Because the phosphorylation of these sites by AKT suppresses apoptosis, the requirement of LKB1 suggests that LKB1 may have a pro-apoptotic role in tumor cells that are addicted to EGFR signaling. In summary, we believe LKB1 plays dual roles in lung cancer development. While it is a tumor-suppressor in lung cancer caused by smoking, we hypothesize that the integrity of the LKB1/AMPK pathway is a critical determinant of the phosphorylation and inactivation of pro-apoptotic proteins in non-smoking related lung cancers that are addicted to EGFR signaling. A better understanding of this novel, potential pro-oncogenic role of the LKB1/AMPK pathway in NSCLC and its role in chemosensitivity may have a direct impact on the targeted clinical use of existing therapies, such as EGFR inhibitors, and may provide a molecular basis for future implementation of "personalized" therapy.

描述（由申请人提供）：EGFR 激活突变经常存在于非​​吸烟相关肺癌中。大多数这些肿瘤都依赖于 EGFR 信号传导，并且可以用酪氨酸激酶抑制剂 (TKI)（例如吉非替尼）有效治疗。肺癌对吉非替尼的高敏感性与 EGFR 信号传导对 AKT 激活的依赖性密切相关，而吉非替尼治疗可抑制 AKT 激活。最近发现，AKT 功能的恢复是获得 TKI 耐药性的 EGFR 突变型肺肿瘤的关键步骤，其中一种潜在机制涉及 c-MET 的扩增，绕过了对 EGFR 的需求，从而使 EGFR 抑制剂无效。 LKB1 通常被称为肿瘤抑制因子，因为体细胞 LKB1 失活突变是吸烟相关肺癌中最常见的突变基因之一。然而，在EGFR突变的肺癌中很少发现LKB1突变。我们发现 LKB1 在依赖 EGFR 信号传导的肺癌中具有一种新的潜在致癌作用。我们发现 LKB1 表达的抑制会导致 EGFR 或 AKT 持续激活的 6 种细胞系发生凋亡，但 2 种 EGFR 或 AKT 没有激活的细胞系则不会发生凋亡。更重要的是，通过两种已知机制获得 TKI 耐药的 EGFR 突变细胞仍然容易因 LKB1 耗尽而诱导细胞凋亡。 从机制上讲，我们发现在 LKB1 野生型细胞中，EGFR/AKT 激活导致 FoxO3A 在苏氨酸 32 (Thr32) 处的磷酸化增加，但在 LKB1 缺失细胞中则不然。具有野生型LKB1的细胞中LKB1的耗尽导致激活的EGFR/AKT对FoxO3A的磷酸化减弱，而LKB1缺失细胞中LKB1功能的恢复则重新建立了EGFR/AKT介导的FoxO3A磷酸化。将我们的分析扩展到其他 AKT 靶点后，使用三种不同的同基因 LKB1 敲低细胞系对和磷酸化特异性抗体微阵列，我们观察到其他 AKT 下游靶点的磷酸化需要 LKB1，包括 BAD (Ser136)、FoxO1 (Ser319)、FoxO4 (Ser197) 和 GSK32 (Ser9)。由于 AKT 对这些位点的磷酸化会抑制细胞凋亡，因此 LKB1 的需要表明 LKB1 可能在依赖 EGFR 信号转导的肿瘤细胞中具有促凋亡作用。 总之，我们认为 LKB1 在肺癌发展中发挥双重作用。虽然它是吸烟引起的肺癌的肿瘤抑制剂，但我们假设 LKB1/AMPK 通路的完整性是依赖 EGFR 信号转导的非吸烟相关肺癌中促凋亡蛋白磷酸化和失活的关键决定因素。更好地了解 LKB1/AMPK 通路在 NSCLC 中的这种新颖的、潜在的促癌作用及其在化疗敏感性中的作用可能会对现有疗法（如 EGFR 抑制剂）的靶向临床使用产生直接影响，并可能为未来实施“个性化”治疗提供分子基础。