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​​吸烟相关的肺癌中。这些肿瘤中的大多数都沉迷于EGFR信号传导，可以用酪氨酸激酶抑制剂（TKI）（例如Gefitinib）有效治疗。对吉非替尼在肺癌中的高灵敏度与响应于EGFR信号的AKT激活的依赖性密切相关，而Gefitinib治疗抑制了AKT的激活。最近发现，AKT功能的恢复是获得对TKI耐药性的EGFR突变肺肿瘤的关键步骤，并且一种潜在的机制涉及C-MET的扩增，C-MET绕过EGFR的需求，使EGFR抑制剂效应不佳。 LKB1通常被称为肿瘤抑制剂，因为体细胞LKB1失活突变是吸烟相关的肺癌中最常见的突变基因之一。然而，在具有EGFR突变的肺癌中很少发现LKB1突变。我们发现了沉迷于EGFR信号传导的肺癌中LKB1的新型，潜在的致癌作用。我们发现LKB1表达的抑制导致六个细胞系中的凋亡，其中EGFR或AKT具有组成性活性，但在没有EGFR或AKT激活的两个细胞系中却没有。更重要的是，通过两种已知机制获得的TKI抗性的EGFR突变细胞仍然容易受到LKB1耗竭引起的凋亡。 从机械上讲，我们发现EGFR/AKT激活导致LKB1野生型细胞中苏氨酸32（THR32）在苏氨酸32（THR32）上的磷酸化增加，但在LKB1-NULL细胞中却没有。 LKB1在具有野生型LKB1的细胞中的耗竭导致FOXO3A的磷酸化通过激活的EGFR/AKT对FOXO3A的磷酸化衰减，而LKB1 lkb1在LKB1无效细胞中的恢复恢复了EGFR/Akt egfr/akt介导的FOXO3A磷酸化。 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).由于AKT对这些位点的磷酸化抑制了凋亡，因此LKB1的需求表明LKB1在肿瘤细胞中可能具有促凋亡作用，而这些作用会上瘾于EGFR信号传导。 总而言之，我们认为LKB1在肺癌开发中起双重作用。虽然它是吸烟引起的肺癌中的肿瘤抑制剂，但我们假设LKB1/AMPK途径的完整性是磷酸化和促凋亡蛋白的关键决定因素，在非吸烟相关的相关肺癌中吸引了促凋亡的蛋白质，这些肺癌吸引了EGFR信号。更好地理解NSCLC中LKB1/AMPK途径的这种新颖的潜在亲核作用及其在化学敏感性中的作用可能会直接影响现有疗法的靶向临床使用，例如EGFR抑制剂，并可能为未来实施“个性化”疗法提供分子基础。