The Gli Family of Transcriptional Activators and Breast Cancer Mediated Osteolysi

Gli 转录激活剂家族和乳腺癌介导的骨质溶解

• 批准号: 7028456
• 负责人: GREGORY R MUNDY
• 金额: $ 13.68万
• 依托单位: VANDERBILT UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-12-01 至 2010-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7028456
• 关键词: MCF7 cell; athymic mouse; bone disorder; breast neoplasms; gel mobility shift assay; gene deletion mutation; genetic regulation; hormone regulation /control mechanism; host neoplasm interaction; hypercalcemia; metastasis; molecular oncology; morphometry; neoplastic cell; neoplastic growth; northern blottings; oligonucleotides; parathyroid hormone related protein; pathologic bone resorption; polymerase chain reaction; site directed mutagenesis; transcription factor

Parathyroid hormone-related peptide (PTH-rP) is the likely causative factor not only in humoral hypercalcemia of malignancy (HHM), but also in many cases of the local osteolysis associated with metastatic breast cancer. The reasons for overexpression of PTH-rP by cancer cells in these situations are unknown. In breast cancer, there is almost universal expression of PTH-rP in bone metastatic sites. Pharmacologic inhibition of PTH-rP transcription in bone causes reduction in osteolysis and tumor burden in that site. Understanding the mechanisms responsible for PTH-rP overexpression by cancer cells could thus lead to identification of molecular targets for drugs that could be effective in the prevention or treatment of breast cancer and other cancers that are associated with increased PTH-rP expression. We hypothesize that the Gli family of transcription factors, the hedgehog signaling molecules in vertebrate cells, are important heretofore uninvestigated regulators of PTH-rP expression in metastatic human breast cancer cells. We propose that Gli family members have distinct and separate functions with respect to regulating PTH-rP expression. GH2 is a powerful transcriptional activator, and the truncated form of Gli3 (produced by the actions of the specific E3 ubiquitin ligase beta-TrCP and subsequent proteasomal processing) is a strong represser of PTH-rP transcription. (Gli1 and Gli2 are not processed to truncated represser forms, and full length Gli1 and Gli3 have no significant effects on PTH-rP transcription according to our Preliminary Data). Our preliminary data suggests that human breast cancer cells overexpress Gli2, and that transient transfection of these cells with GN2 and truncated Gli3 regulate PTH-rP expression. Expression of endogenous Gli2 in breast cancer cells correlates with PTH-rP expression and capacity to cause hypercalcemia or osteolysis. Cancer cells stably transfected with Gli2 cause enhanced osteolysis in vivo. We plan to test our hypothesis by determining if Gli2 and truncated Gli3 enhance or reduce PTH-rP expression and osteolysis induced by human breast cancer cells in vivo, identify the molecular mechanisms whereby Gli2 enhances PTH-rP transcription, determine the effects of loss of function of Gli2 and the E3 ligase for Gli3, beta-TrCP, on PTH-rP expression and osteolysis, and the role of GH2 and truncated Gli3 in other PTH-rP overexpressing cancer cells that cause HHM. We propose therefore that the Gli family of transcriptional regulators represents an important molecular pathway that regulates PTH-rP expression in breast cancer cells, and subsequent breast cancer-mediated osteolysis.

甲状旁腺激素相关肽（PTH-rP）不仅是体液性高钙血症的可能致病因素 恶性肿瘤（HHM），而且在许多情况下还与转移性乳腺癌相关的局部骨溶解。 在这些情况下，癌细胞过度表达 PTH-rP 的原因尚不清楚。在乳腺癌中， PTH-rP 在骨转移部位几乎普遍表达。 PTH-rP 的药理学抑制 骨中的转录导致该部位的骨溶解和肿瘤负荷减少。因此，了解癌细胞 PTH-rP 过度表达的机制可以确定药物的分子靶标，这些药物可以有效预防或治疗乳腺癌和其他与 PTH-rP 表达增加相关的癌症。我们假设转录因子 Gli 家族（脊椎动物细胞中的刺猬信号分子）是转移性人乳腺癌细胞中 PTH-rP 表达的重要调节因子，迄今为止尚未研究。我们认为 Gli 家族成员在调节 PTH-rP 表达方面具有独特且独立的功能。 GH2 是一种强大的转录激活剂，截短形式的 Gli3（由特定 E3 泛素连接酶 β-TrCP 的作用和随后的蛋白酶体加工产生）是 PTH-rP 转录的强抑制剂。 （根据我们的初步数据，Gli1 和 Gli2 未加工成截短的阻遏蛋白形式，全长 Gli1 和 Gli3 对 PTH-rP 转录没有显着影响）。我们的初步数据表明，人类乳腺癌细胞过度表达 Gli2，并且用 GN2 和截短的 Gli3 瞬时转染这些细胞可调节 PTH-rP 表达。乳腺癌细胞中内源性 Gli2 的表达与 PTH-rP 表达以及引起高钙血症或骨溶解的能力相关。稳定转染 Gli2 的癌细胞会导致体内骨质溶解增强。我们计划通过确定 Gli2 和截短的 Gli3 是否增强或减少人乳腺癌细胞体内 PTH-rP 表达和骨质溶解来检验我们的假设，确定 Gli2 增强 PTH-rP 转录的分子机制，确定功能丧失的影响Gli2 和 Gli3 的 E3 连接酶、β-TrCP 对 PTH-rP 表达和骨质溶解的影响，以及 GH2 和截短的 Gli3 在其他疾病中的作用PTH-rP 过度表达的癌细胞会导致 HHM。 因此，我们认为转录调节因子 Gli 家族代表了调节乳腺癌细胞中 PTH-rP 表达以及随后乳腺癌介导的骨溶解的重要分子途径。