MCJ function in mouse mammary tumor properties

描述（由申请人提供）：乳腺癌是人类最常见的癌症之一。它是美国女性癌症死亡的第二大原因。化疗在乳腺癌的控制中起着重要作用。在早期乳腺癌中，化疗可使年复发率降低24%，死亡率降低15%。紫杉醇类（紫杉醇和多西紫杉醇）和蒽环类（阿霉素、表柔比星）是治疗乳腺癌最有效的药物。然而，无反应者和初次反应后失败的百分比仍然相对较高。因此，了解耐药性的分子机制是非常重要的。MCJ是DnaJ家族中一个相对较新发现的成员，MCJ的表达缺失与卵巢癌患者化疗反应差和生存率低有关。我们最近首次发现MCJ在对化疗药物敏感的人乳腺癌细胞中表达，但在多药耐药的乳腺癌细胞中表达缺失。此外，抑制MCJ在药物敏感癌细胞系中的表达，通过c-Jun上调特异性ABC转运蛋白基因的表达，从而阻止化疗药物在细胞内的积累，从而诱导体外多药耐药。在这里，我们提出证明MCJ在乳腺肿瘤中的表达缺失会促进体内多药耐药。为了实现我们的目标，我们已经在小鼠中鉴定和表征了人类MCJ的同源性。为了证明小鼠乳腺癌细胞中MCJ的缺失增强了肿瘤在体内对化疗的抵抗（特异性目的1），我们建议使用：1)MCJ缺陷小鼠和2)在乳腺组织中特异性表达MCJ siRNA的转基因小鼠。为了证明人乳腺癌细胞中MCJ的缺失促进了体内的多药耐药（Specific Aim 2），我们将使用在免疫缺陷小鼠中失去MCJ表达的人乳腺癌细胞的异种移植物。因此，我们不仅要研究MCJ表达缺失与化疗耐药增强的潜在相关性，还要研究MCJ表达缺失是否是多药耐药的原因之一。虽然对人乳腺组织中MCJ表达的分析可以提供相关信息，但我们的研究将证明MCJ表达缺失与多药耐药之间的因果关系。考虑到多药耐药是乳腺癌治疗的头号问题，这些研究具有高度相关性。

DESCRIPTION (provided by applicant): Breast cancer is one of the most common cancers in humans. It is the second leading cause of cancer death among women in United States. Chemotherapy plays an important role in the control of breast cancer. In early breast cancer, chemotherapy decreases the annual odds of recurrence by 24% and odds of death by 15%. Taxanes (paclitaxel and docetaxel) and anthracyclines (doxorubicin, epirubicin) are among the most active drugs used in the treatment of breast cancer. The percentage of non-responders and of failures following an initial response however remains relatively high. Understanding the molecular mechanisms of drug resistance is therefore of major importance. Loss of expression of MCJ, a relatively new identified member of the DnaJ family of co-chaperones, has been shown to correlate with poor chemotherapy response and poor survival in ovarian cancer patients. We have recently shown for the first time that MCJ is expressed in human breast cancer cells that are sensitive to chemotherapeutic drugs, but its expression is lost in multidrug resistant breast cells. Furthermore, inhibition of MCJ expression in drug-sensitive cancer cell lines induces multidrug resistance in vitro by preventing intracellular accumulation of chemotherapeutic drugs due to the upregulation of specific ABC transporter gene expression through c-Jun. Here we propose to demonstrate that loss of MCJ expression in breast tumors promotes multidrug resistance in vivo. To achieve our goals we have already identified and characterized the ortholog of human MCJ in mouse. To demonstrate that the absence of MCJ in mouse breast cancer cells enhances tumor resistance to chemotherapy in vivo (Specific Aim 1) we propose to use: 1) MCJ deficient mice and 2) transgenic mice expressing a siRNA for MCJ specifically in mammary tissue. To demonstrate that the loss of MCJ in human breast cancer cells promotes multidrug resistance in vivo (Specific Aim 2) we will use xenografts of human breast cancer cells that have lost MCJ expression in immunodeficient mice. Thus, we will investigate, not only a potential correlation of loss of MCJ expression with enhanced chemotherapy resistance, but whether the loss of MCJ expression is a cause of multidrug resistance. While the analysis of MCJ expression in human breast tissue can provide correlative information, our studies will demonstrate a cause-effect of loss of MCJ expression and multidrug resistance. These studies are highly relevant considering that multidrug resistance is number one problem in breast cancer therapy.