A NEURAL TRANSCRIPTION FACTOR IN LUNG CANCER EVOLUTION

描述（由申请人提供）：具有神经内分泌（NE）特征的肺癌，特别是小细胞肺癌（SCLC），利用从胎儿神经系统发育中保守的转录调控级联。在这些肺癌中，bHLH（碱性螺旋-环-螺旋）转录因子人无毛鳞片同源物-1（hASH 1，小鼠直系同源物MASH 1）可能在促进肿瘤毒力和原始NE表型中起关键作用。我们已经表明，该因子在转基因气道上皮细胞中的过度表达导致增生和增强的癌发生SV 40大T抗原，NE转分化。在培养的SCLC细胞中沉默hASH 1导致G1细胞周期停滞。在这项研究中，我们将解决的问题，是否hASHI/MASH 1是必不可少的SCLC肿瘤发生的诱导敲除Mash 1基因的背景下，新开发的小鼠SCLC样模型采用诱导敲除pRb和p53。因此，我们将确定MASH 1诱导是否是必要的毒性NE表型诱导的p53和Rb的损失，在这个小鼠模型系统。在另外的小鼠模型中，我们将进一步探索hASH 1与Rb和p53基因的个体缺失合作促进增生、肿瘤发生和NE转分化的机制。最后，我们将试图确定MASHI/hASH 1的转录作用，这对小细胞肺癌的侵袭性生长行为和原始NE表型至关重要。我们将研究候选的生长调节和NE基因，加上用hASH 1特异性siRNA处理的SCLC细胞中的cDNA阵列，在小鼠异种移植物和现有的转基因肺肿瘤模型中进行相关研究。拟议的研究应该提供SCLC生物学方面的新见解，并为确定hASH 1和hASH 1调节的生长机制是否应该作为SCLC的治疗靶点而深入研究奠定坚实的基础。

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.