Chromium and Hedgehog signaling

描述（申请人提供）：六价铬，Cr(VI)，广泛应用于许多工业过程，包括铬颜料生产，镀铬，不锈钢制造，皮革制革等。流行病学研究报告，在职业接触六价铬的工人中，肺癌的发病率很高。虽然Cr（VI）致癌性的机制有多种，但介导Cr（VI）诱导肺癌的分子和途径尚不清楚。Hedgehog （Hh）信号通路在胚胎发生过程中多个组织的形成和成人干细胞群体的维持中发挥重要作用。Hh信号通路的失调在多种人类癌症中被发现，包括基底细胞癌、髓母细胞瘤、结肠癌、胰腺癌和肺癌。我们的初步数据显示，在Cr（VI）转化的细胞中，刺猬相互作用蛋白（HHIP）的mRNA水平显著降低，HHIP是Hh信号的下游靶点和天然拮抗剂。有趣的是，Hh信号在这些细胞中发生了改变，下游靶基因如Gli1和Ptch1水平的升高证明了这一点，这表明Hh信号在Cr（VI）诱导的细胞转化和癌变中可能起作用。本研究计划的主要重点是确定Hh信号在Cr（VI）诱导的细胞转化中的作用，并剖析Cr（VI）调节Hh信号的机制。首先，为了确定HHIP水平的降低和Hh信号的增强是否有助于Cr（VI）诱导的细胞转化和癌变，我们将调节Hh信号通路主要成分的水平，并分析细胞增殖、非锚定生长和体内肿瘤形成的变化。接下来，为了剖析Cr（VI）转化细胞中HHIP下调的表观遗传机制，我们将分析HHIP启动子中的组蛋白修饰和DNA甲基化。我们提出的研究可能是第一个将慢性Cr（VI）暴露与Hh信号通路失调联系起来的研究。该研究方案的成功将显著提高我们对Cr（VI）暴露后Hh信号级联变化的理解，并可能为开发更好的Cr（VI）相关人类癌症的治疗策略提供新的见解。

DESCRIPTION (provided by applicant): Hexavalent chromium, Cr(VI), is widely used in numerous industrial processes, including chrome pigment production, chrome plating, stainless steel manufacturing, and leather tanning, etc. Epidemiological studies have reported a high incidence of lung cancer among chromium workers exposed occupationally to Cr(VI) by inhalation. Although multiple mechanisms were suggested to contribute to Cr(VI) carcinogenicity, the molecules and pathways that mediate Cr(VI) induced lung cancer are not well understood. Hedgehog (Hh) signaling is a key pathway that plays important roles in the formation of multiple tissues during embryogenesis and in the maintenance of stem cell populations in adults. Dysregulation of the Hh signaling pathway was found in a variety of human cancers, including basal cell carcinomas, medulloblastomas, colon cancers, pancreatic cancers, and lung cancers. Our preliminary data demonstrated a significant decrease in mRNA levels of hedgehog-interacting protein (HHIP), a downstream target and a natural antagonist of Hh signaling, in Cr(VI) transformed cells. Interestingly, Hh signaling was altered in these cells a evidenced by increased levels of downstream target genes, such as Gli1 and Ptch1, suggesting a potential role of Hh signaling in Cr(VI) induced cell transformation and carcinogenesis. The primary focus of this research proposal is to determine the role of Hh signaling in Cr(VI) induced cell transformation and to dissect the mechanism by which Cr(VI) modulates Hh signaling. First, to determine whether decreased HHIP levels and enhanced Hh signaling contribute to Cr(VI) induced cell transformation and carcinogenesis, we will modulate the levels of major components of Hh signaling pathway and analyze the changes in cell proliferation, anchorage-independent growth and in vivo tumor formation. Next, to dissect the epigenetic mechanism underlying the down-regulation of HHIP in Cr(VI) transformed cells, we will analyze the histone modifications and DNA methylation in HHIP promoter. Our proposed study may be the first to link chronic Cr(VI) exposure to the dysregulation of the Hh signaling pathway. The success of this research proposal will significantly improve our understanding of the changes in Hh signaling cascade after Cr(VI) exposure and may provide new insights for developing a better therapeutic strategy for Cr(VI)-related human cancer.