A NEURAL TRANSCRIPTION FACTOR IN LUNG CANCER EVOLUTION

这项拨款申请的重点是转录因子，人类无鳞鳞同源物-1 （hASH1）在小细胞肺癌（SCLC）进化中的关键作用。与其他三种主要类型的肺癌不同，SCLC的特点是神经和神经内分泌（NE）特征的表达。HASH1是人类与果蝇-鳞片复合物的对应物，这是一个保守的基本螺旋环螺旋转录因子家族，对于未分化前体的原始神经母细胞的承诺至关重要。在哺乳动物发育过程中，ASH1（在啮齿动物中称为MASH1）对于交感肾上腺、肠、嗅觉、视网膜和脑交感神经元的正常分化至关重要。我们最近发现，正常胎儿肺中的ASH1仅限于肺NE细胞。此外，转基因敲除ASH1会导致肺NE细胞完全无法分化，并在出生时导致致命的呼吸功能不全。肺损伤模型的初步研究表明，hASH1在增生性肺NE细胞的募集中起重要作用。在广泛的肺癌表型中，hASH1表达与NE表型标记物严格一致。我们发现，从培养的SCLC细胞中去除hASH1蛋白会导致NE标记物表达的相应降低，以及凋亡比例的增加。我们研究了一种新的转基因模型，其中hASH1使用细胞特异性CC10启动子靶向肺Clara细胞。这些小鼠发生涉及cc10反应细胞的远端气道进行性增生。值得注意的是，hASH1与SV40 t抗原有效合作，促进这些靶细胞的恶性转化和NE肿瘤。总的来说，这些发现表明，hASH1可能在肺NE前体细胞的SCLC进化中起关键作用。我们提出的一系列研究现在试图确定：1)hASH1和相关的前膜转录因子如何在新型肺癌发生模型中起作用；2)与肺癌进化相关的hASH1的转录靶点是什么？ 3)在SCLC细胞中，如何通过Notch通路改变hASH1的调控。这些研究将提供对hASH1在SCLC发病机制中的作用的更全面的了解，可能导致在新的治疗策略中利用SCLC肿瘤的特定脆弱性。

This grant proposal focuses on the critical role of the transcription factor, human achaete-scute homolog-1 (hASH1) in the evolution of small cell lung cancer (SCLC). Unlike the other three major types of lung cancer, SCLC is distinguished by expression of neural and neuroendocrine (NE) features. HASH1 is a human counterpart to the Drosophila achaete-scute complex, a conserved family of basic helix loop helix transcription factors that are essential for commitment of primitive neuroblasts from undifferentiated precursors. In mammalian development, ASH1 (termed MASH1 in rodents) is essential for normal differentiation of sympathoadrenal, enteric, olfactory, retinal, and brain sympathetic neurons. We have recently shown that ASH1 in the normal fetal lung is restricted to lung NE cells. Furthermore, transgenic knockout of ASH1 results in a complete failure of lung NE cells to differentiate and causes fatal respiratory insufficiency at birth. Preliminary studies from lung injury models suggest an important role for hASH1 in the recruitment of hyperplastic lung NE cells. Across a broad spectrum of lung cancer phenotypes, hASH1 expression is strictly concordant with NE phenotypic markers. We found that depletion of hASH1 protein from cultured SCLC cells resulted in a comparable reduction of NE marker expression, and an increase in apoptotic fraction. We have studied a new transgenic model in which hASH1 is targeted to lung Clara cells, using a cell-specific CC10 promoter. These mice develop progressive hyperplasia of their distal airway involving the CC10-reactive cells. Remarkably, hASH1 cooperates potently with the SV40 T-Antigen to promote malignant transformation and NE tumors in these target cells. Collectively, these findings indicate that hASH1 may be critical in the evolution of SCLC from lung NE precursor cells. Our proposed series of studies now seek to determine: 1) How hASH1 and related proneural transcription factors function in novel models of lung carcinogenesis; 2) What are the transcriptional targets of hASH1, relevant to the evolution of lung cancer, and 3) How hASH1 regulation, via the Notch pathway, may be altered in SCLC cells. These studies will provide a more comprehensive understanding of hASH1 action in SCLC pathogenesis, potentially leading to exploitation of specific vulnerabilities of SCLC tumors in novel treatment strategies.