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，局部骨质溶解与转移性乳腺癌。 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质溶解和肿瘤负荷减少。因此，了解负责癌细胞PTH-rP过表达的机制可能会导致识别药物的分子靶点，这些药物可能有效地预防或治疗乳腺癌和其他与PTH-rP表达增加相关的癌症。我们推测，Gli家族的转录因子，刺猬信号分子在脊椎动物细胞中，是重要的迄今未调查的调节PTH-rP在转移性人乳腺癌细胞中的表达。我们认为Gli家族成员在调节PTH-rP表达方面具有独特和独立的功能。GH 2是一种强大的转录激活因子，截短形式的Gli 3（由特异性E3泛素连接酶β-TrCP和随后的蛋白酶体加工作用产生）是PTH-rP转录的强阻遏物。(Gli1和Gli 2不被加工成截短的阻遏物形式，并且根据我们的初步数据，全长Gli 1和Gli 3对PTH-rP转录没有显著影响）。我们的初步数据表明，人乳腺癌细胞过度表达Gli 2，和瞬时转染这些细胞与GN 2和截断Gli 3调节PTH-rP的表达。乳腺癌细胞中内源性Gli 2的表达与PTH-rP表达和引起高钙血症或骨质溶解的能力相关。用Gli 2稳定转染的癌细胞在体内引起增强的骨质溶解。我们计划通过确定Gli 2和截短的Gli 3是否增强或减少人乳腺癌细胞体内诱导的PTH-rP表达和骨质溶解来验证我们的假设，确定Gli 2增强PTH-rP转录的分子机制，确定Gli 2和Gli 3的E3连接酶β-TrCP功能丧失对PTH-rP表达和骨质溶解的影响，以及GH 2和截短的Gli 3在导致HHM的其他PTH-rP过表达癌细胞中的作用。 因此，我们建议Gli家族的转录调节因子代表了一个重要的分子途径，调节PTH-rP在乳腺癌细胞中的表达，以及随后的乳腺癌介导的骨质溶解。