Characterization of epidermal stem cells: biology, carci

肿瘤生物学实验室多年来一直使用v-Ha-ras转基因Tg.AC小鼠模型来研究与皮肤肿瘤发生相关的分子和生物学事件。实验室的早期工作表明，乳头状瘤的发展与ras转基因在毛囊、表皮干细胞和祖细胞中的异位表达之间存在潜在的联系。由此我们发现，CD34是小鼠皮肤毛囊隆起角质形成细胞上唯一表达的造血干细胞标志物。CD34表达的凸起细胞已被证明是缓慢周期和多潜能的，鉴定它们是干细胞和祖细胞群体。由于CD34在毛囊中的致癌物靶细胞上的定位，我们验证了CD34在皮肤肿瘤发生中可能具有动态功能的假设。通过使用CD34KO小鼠系，我们利用皮肤肿瘤发生的两阶段模型证明了CD34在干细胞激活和乳头状瘤形成中发挥作用。 对CD34+角质形成细胞的基因表达分析表明，该缺失基因在裂手/裂足1(Dss1)中的表达，随后被证明在细胞中具有生长调节作用。我们已经确定Dss1通过直接与蛋白酶体组装的19S调节颗粒的Rpn3/S3亚单位结合来介导其生长调节作用，在蛋白酶体与泛素化底物结合和随后的蛋白质降解中具有重要意义。 为了了解肿瘤发生中的关键信号通路，我们建立了p19ARFhetTgAChemi和p19ARFnullTgAChemi小鼠，以探讨Ha-ras和p19ARF在皮肤肿瘤发生中的关系。P19ARFnullTgAChem小鼠出人意料地出现了胃肠道肿瘤，随后被发现是胃肠道间质肿瘤(GIST)，这是人类最常见的胃肠道间充质肿瘤。这一模型为研究从早期侵袭前病变到恶性病变的GIST生物学提供了独特的机会。

The Cancer Biology Laboratory has for many years used the v-Ha-ras transgenic Tg.AC mouse model to study the molecular and biological events associated with skin tumor development. Early work in the laboratory demonstrated a potential link between papilloma development and ectopic expression of the ras transgene in hair follicle epidermal stem and progenitor cells. From this, we discovered that the hematopoietic stem cell marker CD34 is uniquely expressed on hair follicle bulge keratinocytes in mouse skin. CD34-expressing bulge cells have been demonstrated to be both slowly cycling and multipotent, identifying them as a stem and progenitor cell population. Because of the localization of CD34 on carcinogen target cells in the hair follicle, we tested the hypothesis that CD34 may have a dynamic function in skin tumor development. Using a CD34KO mouse line, we have shown that CD34 plays a role in stem cell activation and papillomagenesis using the two-stage model of skin tumorigenesis. Gene expression analysis of CD34+ keratinocytes revealed expression of the Deleted in Split Hand/Split Foot 1 (Dss1), which has subsequently been shown to have a growth regulatory role in the cell. We have determine that Dss1 mediates its growth regulation effects through direct binding with the Rpn3/S3 subunit of the 19S regulatory particle of the proteasome assembly, with important implications in binding of the proteasome to ubiquitinylated substrates and subsequent protein degradation. To understand key signaling pathways in tumor development, we generated p19ARFhetTgAChemi and p19ARFnullTgAChemi mice to explore the relationship between Ha-ras and p19ARF in skin tumor development. The p19ARFnullTgAChem mice unexpectedly developed tumors in the gastrointestinal tract that were subsequently revealed to be Gastrointestinal Stromal Tumors (GIST), which are the most common mesenchymal tumor of the gastrointestinal tract in humans. This model offers the unique opportunity to study GIST biology from the early preinvasive lesion to malignancy.