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），利用胎儿神经系统发育中保守的转录调节级联。在这些肺癌中，bHLH（碱性螺旋-环-螺旋）转录因子人类无毛鳞鳞同源物-1 （hASH1，小鼠同源物MASH1）可能在促进肿瘤毒力和原始NE表型中起关键作用。我们已经证明，在转基因气道上皮中，该因子的过度表达可导致SV40大T抗原的增生和癌变增强，并伴有NE反分化。在培养的SCLC细胞中沉默hASH1可导致G1细胞周期阻滞。在本研究计划中，我们将通过诱导敲除MASH1基因，在新开发的小鼠SCLC样模型中，通过诱导敲除pRb和p53，来解决hASHI/MASH1是否对SCLC肿瘤发生至关重要的问题。因此，我们将确定在该小鼠模型系统中，p53和Rb丢失诱导的恶性NE表型是否需要诱导MASH1。在其他小鼠模型中，我们将进一步探索hASH1与个体Rb和p53基因缺失合作促进增生、肿瘤发生和NE转分化的机制。最后，我们将尝试确定MASHI/hASH1的转录作用，这对SCLC的侵袭性生长行为和原始NE表型至关重要。我们将研究候选生长调控基因和NE基因，以及经过hashl特异性siRNA处理的SCLC细胞的cDNA阵列，并在小鼠异种移植和现有的转基因肺肿瘤模型中进行相关研究。拟议的研究将为SCLC生物学提供新的见解，并为确定是否应该深入研究hASH1和hASH1调节的生长机制作为SCLC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.