Novel mechanisms of oncogenic transformation in lung cancer

描述（由申请人提供）：在美国，死于肺癌的人数比死于乳腺癌、前列腺癌和结肠癌的人数总和还要多。特定的癌基因，如生长因子信号转导GT3-KRAS，在肺癌中突变并组成性活跃。虽然很明显致癌蛋白可以驱动肺癌的发展，但对导致这一过程以及肺癌的起始和进展的分子和遗传事件的理解并不完全。microRNA（miRNA）是一种调节蛋白质表达的非编码RNA，与肿瘤发生、发展的细胞过程有关。我们推测，在肺癌中过表达的特定miRNA本身可能作为癌基因发挥作用，或与已知癌基因合作启动这种恶性肿瘤。为了确定特定的miRNA是否在肺腺癌（最常见的肺癌）中具有致癌作用，我们研究了miRNA的表达。在肺腺癌中检测到特异性miRNA水平的改变，并且一种特定的miRNA在一组还含有KRAS激活突变的肺腺癌细胞系中过表达。值得注意的是，在人肺腺癌患者样本中检测到该miRNA水平升高，并且这与疾病阶段相关。在未转化的人肺上皮细胞中过表达该miRNA导致增殖增加和锚定非依赖性生长。在异种移植模型中，抑制人肺腺癌细胞中的这种miRNA抑制增殖和过表达诱导的肿瘤形成。重要的是，在一个新的，新产生的小鼠模型中，这种miRNA在肺中的诱导表达迅速导致增生和腺瘤的发展。我们还鉴定了RAS通路信号传导的多个负调节因子作为该miRNA的靶点。因此，我们假设这种miRNA是通过调节RAS致癌信号通路启动肺腺癌的新驱动因素，并且它在肺癌发展中与突变型KRAS合作。我们建议用三个具体目标来检验这一假设。在目标1中，我们将使用新的肺特异性诱导型miRNA小鼠来评估这种miRNA表达增加对肺癌发生的影响及其对突变型KRAS驱动的肺癌的贡献。在目标2中，我们将研究致癌RAS通路的负调控因子作为特定miRNA的靶点，并将确定在腺癌发生和进展期间促成肺早期和晚期变化的新靶点。在目标3中，我们将确定人类肺癌中的基因突变和调节这种miRNA表达的信号通路。本申请中提出的小鼠模型、患者样本、分子生物学、生物化学和细胞生物学的整合将显著增加对miRNA对肺腺癌的贡献以及导致这种致命疾病开始的分子事件的理解。这些研究的结果也可能为肺腺癌确定新的治疗靶点和诊断及预后标志物。

DESCRIPTION (provided by applicant): More people in the US die from lung cancer than from breast, prostate and colon cancer combined. Specific oncogenes, such as the growth factor signaling GTPase KRAS, are mutated and constitutively active in lung cancers. Although it is clear oncogenic proteins can drive lung cancer development, there is incomplete understanding of the molecular and genetic events that result in this process and in the initiation and progression of lung cancers. microRNA (miRNA), non-coding RNA that regulate protein expression, have been linked to cellular processes involved in tumor development and progression. We postulated that specific miRNA that are overexpressed in lung cancer may function as oncogenes themselves or cooperate with known oncogenes in the initiation of this malignancy. To determine whether specific miRNA have an oncogenic role in lung adenocarcinoma, the most common lung cancer, we investigated miRNA expression. Altered levels of specific miRNA were detected in lung adenocarcinoma, and one particular miRNA was overexpressed in a panel of lung adenocarcinoma cells lines that also contained activating mutations of KRAS. Notably, elevated levels of this miRNA were detected in human lung adenocarcinoma patient samples and this correlated with disease stage. Overexpression of this miRNA in untransformed human lung epithelial cells resulted in increased proliferation and anchorage-independent growth. Inhibition of this miRNA in human lung adenocarcinoma cells suppressed proliferation and overexpression induced tumor formation in a xenograft model. Importantly, in a novel, newly generated mouse model, inducible expression of this miRNA in the lungs rapidly led to hyperplasia and adenoma development. We have also identified multiple negative regulators of RAS pathway signaling as targets of this miRNA. Therefore, we hypothesize this miRNA is a novel driver of lung adenocarcinoma initiation through modulation of the RAS oncogenic signaling pathway and that it cooperates with mutant KRAS in lung cancer development. We propose to test this hypothesis with three Specific Aims. In Aim 1, we will use the novel lung specific inducible miRNA mouse to evaluate the effects of increased expression of this miRNA on lung cancer initiation and its contribution to mutant KRAS-driven lung cancer. In Aim 2, we will investigate the negative regulators of the oncogenic RAS pathway as targets of the specific miRNA, and we will identify novel targets that contribute to early and late changes in the lung during adenocarcinoma initiation and progression. In Aim 3, we will determine the genetic mutations in human lung cancer and the signaling pathways that regulate the expression of this miRNA. The integration of mouse models, patient samples, molecular biology, biochemistry, and cell biology proposed in this application will significantly increase understanding of the contribution of miRNA to lung adenocarcinoma and the molecular events that lead to the initiation of this deadly disease. Results from these studies are also likely to identify novel therapeutic targets and diagnostic and prognostic markers for lung adenocarcinoma.