Mechanisms of tumor resistance to anti-HER/ErbB therapeutics

描述(申请人提供)：曲妥珠单抗(Herceptin)是一种人源化的抗HER2单抗，已被证明当它被添加到HER2过度表达的乳腺癌的标准化疗中时，可以提供明显的生存益处。然而，不幸的是，只有30-40%的HER2阳性乳腺肿瘤对曲妥珠单抗有反应。在这项提案中，我们将探讨促红细胞生成素(EPO)诱导的细胞信号在乳腺癌对曲妥珠单抗耐药中是否发挥作用。EPO是一种主要由肾脏中的一组特化细胞产生的主要造血细胞因子，作用于骨髓中的红系祖细胞，导致红细胞生成。重组人促红细胞生成素(RHuEPO)经常用于癌症患者，以预防和缓解癌症和癌症治疗相关的贫血和疲劳。最近的研究表明，EPO通过激活非造血组织中发现的EPO受体(EPOR)，对这些组织具有显著的细胞保护作用。有趣的是，EPOR也存在于一些临床肿瘤标本中，特别是乳腺癌患者的肿瘤标本中。作为I型细胞因子受体家族的一员，EPOR在EPO结合后同源二聚体，触发受体相关蛋白JAK2的激活，随后STAT5的磷酸化，以及由含有SH2结构域的适配器介导的信号转导级联，该信号转导通路基本上与HER2介导的信号通路重叠。在我们的初步研究中，我们发现EPOR和HER2在相当数量的已建立的乳腺癌细胞系和患者的乳腺癌组织样本中共表达。RHuEPO以EPOR表达依赖的方式激活细胞信号转导，与曲妥珠单抗和rHuEPO同时处理HER2/EPOR双阳性乳腺癌细胞降低了对曲妥珠单抗的治疗反应。我们假设，同时给予rHuEPO的细胞信号传递构成了乳腺癌对曲妥珠单抗耐药的临床相关机制。我们计划从四个具体目标验证这一假说：1)确认rHuEPO对曲妥珠单抗在HER2/EPOR双阳性乳腺癌细胞中的细胞保护作用；2)确定在HER2/EPOR双阳性乳腺癌移植瘤中同时给予rHuEPO能在多大程度上抵消曲妥珠单抗的抗肿瘤活性；3)通过激活rHuEPO介导对曲妥珠单抗的细胞保护作用，阐明EPOR下游信号通路；以及4)确认HER2和EPOR共表达的存在，并测定其在乳腺癌患者肿瘤标本中的表达频率。这些目标的实现将揭示EPO/EPOR信号是否与曲妥珠单抗耐药有关。积极的发现将为进一步研究是否应该继续在乳腺癌患者中同时使用rHuEPO和曲妥珠单抗提供依据。 公共卫生相关性：药物促红细胞生成素(EPO)通常用于乳腺癌患者，以帮助预防或减轻与治疗相关的贫血和疲劳；然而，来自我们实验室和其他实验室的一些证据表明，EPO可能会使乳腺癌对抗乳腺癌药物曲妥珠单抗产生耐药性。我们将调查这一可能性。我们的发现可能表明EPO不应该用于正在接受曲妥珠单抗治疗的乳腺癌患者。

DESCRIPTION (provided by applicant): Trastuzumab (Herceptin), a humanized anti-HER2 monoclonal antibody, has been demonstrated to confer a clear survival benefit when it is added to standard chemotherapy for HER2-overexpressing breast cancer. Unfortunately, however, only 30-40% of HER2-positive breast tumors respond to trastuzumab. In this proposal, we will explore whether erythropoietin (EPO)-induced cell signaling plays a role in breast cancer resistance to trastuzumab. EPO is a prime hematopoietic cytokine produced mainly by a group of specialized cells in the kidney and acts on erythroid progenitor cells in the bone marrow, leading to erythropoiesis. Recombinant human EPO (rHuEPO) is frequently used in cancer patients to prevent and alleviate cancer- and cancer treatment-related anemia and fatigue. Recent studies have shown that EPO has remarkable cytoprotective activity in nonhematopoietic tissues via activation of the EPO receptor (EpoR) found in these tissues. Interestingly, EpoR is also present in some clinical tumor specimens, particularly tumor specimens from breast cancer patients. As a member of the type I cytokine receptor family, EpoR homodimerizes upon EPO binding, triggering activation of the receptor-associated kinase Jak2, subsequent phosphorylation of STAT5, and a signal transduction cascade mediated by SH2 domain-containing adaptors that overlaps substantially with HER2-mediated signaling pathways. We found in our preliminary studies that EpoR is co-expressed with HER2 in a significant number of established breast cancer cell lines and breast cancer tissue specimens from patients. Exposure of breast cancer cells to rHuEPO activated cell signaling in an EpoR expression-dependent manner, and concurrent treatment of HER2/EpoR dual-positive breast cancer cells with trastuzumab and rHuEPO reduced the therapeutic response to trastuzumab treatment. We hypothesize that cell signaling in response to concurrent administration of rHuEPO constitutes a clinically relevant mechanism of breast cancer resistance to trastuzumab. We plan to test this hypothesis in four specific aims: 1) to confirm the cytoprotective effect of rHuEPO against trastuzumab in HER2/EpoR dual-positive breast cancer cells; 2) to determine the extent to which concurrent administration of rHuEPO counteracts the antitumor activity of trastuzumab in HER2/EpoR dual-positive breast cancer xenografts; 3) to elucidate the EpoR downstream signaling pathways through activation of which rHuEPO mediates cytoprotection against trastuzumab; and 4) to confirm the presence of HER2 and EpoR co-expression and to determine its frequency in tumor specimens from breast cancer patients. Attainment of these aims will reveal whether EPO/EpoR signaling contributes to trastuzumab resistance. A positive finding will warrant further investigation of whether rHuEPO should continue to be administered concurrently with trastuzumab in breast cancer patients. PUBLIC HEALTH RELEVANCE: The drug erythropoietin (EPO) is often given to breast cancer patients to help prevent or lessen treatment-related anemia and fatigue; however, some evidence from our laboratory and others suggests that EPO might make breast cancer resistant to the anti-breast cancer drug trastuzumab. We will investigate this possibility. Our findings may indicate that EPO should not be administered to breast cancer patients who are being treated with trastuzumab.