A NEURAL TRANSCRIPTION FACTOR IN LUNG CANCER EVOLUTION

描述(申请人提供)：具有神经内分泌(NE)特征的肺癌，特别是小细胞肺癌(SCLC)，利用胎儿神经系统发育过程中保守的转录调控级联反应。在这些肺癌中，bHLH(碱性螺旋-环-螺旋)转录因子人achaete scute Homolog-1(hASH1，小鼠同源基因MASH1)可能在促进肿瘤毒力和原始NE表型方面发挥关键作用。我们发现，在转基因的呼吸道上皮细胞中过表达该因子会导致SV40大T抗原的增殖和促进癌变，并伴随NE的反式分化。沉默培养的小细胞肺癌细胞中的hASH1导致G1期细胞周期停滞。在这项研究方案中，我们将通过诱导敲除Mash1基因来解决Hashi/MASH1是否是小细胞肺癌发生所必需的问题，在新开发的小鼠SCLC样模型的背景下，利用可诱导的pRb和p53基因敲除。因此，我们将确定在这个小鼠模型系统中，MASH1的诱导是否是由p53和Rb缺失所诱导的毒力NE表型所必需的。在其他小鼠模型中，我们将进一步探索hASH1与Rb和P53基因的个体缺失协同促进增殖、肿瘤发生和NE转分化的机制。最后，我们将试图确定对小细胞肺癌侵袭性生长行为和原始NE表型至关重要的Mashi/hASH1转录行为。我们将研究用hASH1特异性siRNA处理的SCLC细胞中的候选生长调节基因和NE基因，以及cDNA阵列，并在小鼠异种移植瘤和现有的转基因肺肿瘤模型中进行相关研究。拟议的研究应该为小细胞肺癌生物学提供新的见解，并为确定hASH1和hASH1调节的生长机制是否应该作为小细胞肺癌的治疗靶点提供坚实的基础。

DESCRIPTION (provided by applicant): Lung cancers with neuroendocrine (NE) features, particularly small cell lung cancer (SCLC), utilize transcriptional regulatory cascades conserved from fetal nervous system development. In these lung cancers, the bHLH (basic helix-loop-helix) transcription factor human achaete scute homolog-1 (hASH1, mouse ortholog MASH1) may have a critical role in promoting tumor virulence and a primitive NE phenotype. We have shown that over-expression of this factor in transgenic airway epithelium leads to hyperplasia and enhanced carcinogenesis by SV40 Large T antigen, with NE trans-differentiation. Silencing of hASH1 in cultured SCLC cells leads to G1 cell cycle arrest. In this research proposal, we will address the question of whether hASHI/MASH1 is essential to SCLC tumorigenesis by inducibly knocking out the Mash1 gene in the context of a newly-developed mouse SCLC-like model employing an inducible knockout of both pRb and p53. We will thereby determine whether MASH1 induction is necessary for the virulent NE phenotype induced by p53 and Rb loss in this mouse model system. In additional mouse models, we will further explore the mechanisms whereby hASH1 can cooperate with individual loss of the Rb and p53 genes to promote hyperplasia, tumorigenesis, and NE transdifferentiation. Finally, we will attempt to identify transcriptional actions of MASHI/hASH1 that are critical for the aggressive growth behavior and primitive NE phenotype of SCLC. We will study candidate growth regulatory and NE genes, plus cDNA arrays in SCLC cells treated with hASHl-specific siRNA's, performing correlative studies in mouse xenografts and existing transgenic lung tumor models. The proposed studies should provide novel insights in SCLC biology and a firm basis for determining whether hASH1, and hASHl-regulated growth mechanisms, should be intensively pursued as therapeutic targets for SCLC.