Targeted Cancer Therapeutics and Heart Failure: Mechanisms and Post-Injury Rep

该项目研究了小分子酪氨酸激酶引起的心脏损伤。 抑制剂(TKI)。这些药物针对的是酪氨酸激酶，其突变或扩增是原因或 在各种实体肿瘤和白血病中有很强的贡献。他们彻底改变了对一名 这些恶性肿瘤的数量，将一致致命的恶性肿瘤转变为长期可控的，如果不是 可治愈的疾病。许多这些突变的激酶激活促进增殖或阻止增殖的通路 因此，细胞凋亡和抑制细胞凋亡的药物会导致癌细胞周期停滞或细胞死亡。 细胞。然而，所有这些突变的酪氨酸激酶都有野生型的对应物，其中许多是 在心肌细胞和/或心脏常驻干细胞/祖细胞(CRSCs)中表达。这引起了人们的担忧 抑制心脏中的野生型激酶可能会对心肌细胞产生不利影响，可能 导致心脏功能不全，甚至心力衰竭。事实上，我们的临床合作者最近已经确定 FDA批准的两种药物的心脏毒性：伊马替尼(格列卫)和舒尼替尼(舒坦)。这些 这些发现引导我们对培养的心肌细胞和小鼠模型进行研究，这些研究已经确定了分子 伊马替尼引起心脏毒性的机制。在具体目标1中，我们将通过以下方式确定机制 舒尼替尼和另一种药物索拉非尼(Nexavar)，两个不仅阻止 血管生成还可诱导癌细胞凋亡，导致心功能不全。这些研究是 至关重要，因为它们将1)识别TKI的特定靶点，抑制TKI诱导心肌细胞 功能障碍和/或死亡，以及2)确定TKI激活的信号通路(S) 调解功能障碍和死亡。通过确定特定的靶点和介导毒性的途径，我们 应该能够：a)预测也抑制该靶点的未来药物的心脏毒性；b)影响未来的药物 设计，因为在某些情况下，抑制介导毒性的靶点对肿瘤细胞并不是必需的 杀戮和TKI可以被修改以避免这些“旁观者目标；c)确定新的战略，以 在伊马替尼等介导毒性的信号通路不是中心的情况下的心脏保护 对肿瘤细胞的杀伤(例如，JNKs介导伊马替尼毒性，因此抑制JNKs的策略可以减少 伊马替尼心脏毒性，但肿瘤细胞杀伤力保持不变)；d)提醒临床医生和监管机构注意潜在的 仍在开发中的药物(例如JAK2抑制剂来妥替尼)的问题，鼓励他们 在后期临床试验或FDA批准后的早期前瞻性检查左室功能。 本项目的后半部分集中于TKI治疗停药后的修复机制。我们 发现在服用伊马替尼和舒尼替尼的情况下，患者的左心功能在治疗后恢复相当显著 停止将军澳。此外，在对小鼠的研究中，我们发现了心肌细胞脱落的明确证据。 (左心室重量下降)，但几乎没有证据表明过度的细胞凋亡、坏死或自噬。这是我们的 假设至少部分毒性及其可逆性是由于TKIs对KEY的不良影响 CRSCs的功能。具体地说，我们的初步研究将表明，伊马替尼除了Abl外，还 抑制许多CRSCs上表达的c-Kit(干细胞因子受体)，显著减少 C-Kit+CRSCs体外分化为心肌细胞的能力。此外，伊马替尼还可阻止 增殖并诱导c-Kit(-)CRSCs(心脏侧群或SP细胞)的凋亡。因此，分成两部分 不同谱系的CRSCs，伊马替尼导致增殖、分化和凋亡的失调。我们 将采用慢病毒介导的对伊马替尼靶向的激酶的伊马替尼耐药突变的基因转移(Ab1， PDGFRs和c-Kit)试图将这些CRSCs从伊马替尼的不良影响中拯救出来，从而 确定规范这些过程的关键目标(S)。这些研究不应该仅仅确定小说 TKI心脏毒性的机制，但也确定了调节这些关键CRSC的因素和途径 功能，从而促进我们对基本干细胞生物学的理解。最后，我们将把这些关联起来 体外发现与体内研究，检测CRSC的增殖和新的心肌细胞形成。 综上所述，我们相信这些研究将揭示癌症治疗中一个日益严重的问题， 希望通过早期识别和治疗TKI引发的心脏毒性，患者 或许能够在这些救命疗法中维持下去。

This Project examines cardiac injury induced by members of the class of small molecule tyrosine kinase inhibitors (TKIs). These drugs target tyrosine kinases, mutations or amplications of which are causal or strongly contributory in various solid tumors and leukemias. They have revolutionized the treatment of a number of these malignancies, converting uniformly fatal malignancies to chronically manageable, if not curable, diseases. Many of these mutated kinases activate pathways that promote proliferation or prevent apoptosis, and the drugs that inhibit them, therefore, lead to cell cycle arrest or cell death of the cancerous cells. However, all of these mutated tyrosine kinases have wild-type counterparts, many of which are expressed in cardiomyocytes and/or in cardiac-resident stem/progenitor cells (CRSCs). This raises concerns that inhibition of wild-type kinases in the heart might have adverse consequences on cardiomyocytes, possibly leading to cardiac dysfunction and even heart failure. Indeed, our clinical collaborators have recently identified cardiotoxicity of two of these agents that are FDA-approved: imatinib (Gleevec) and sunitinib (Sutent). These findings led us to studies in cultured cardiomyocytes and mouse models that have identified molecular mechanisms by which imatinib induces cardiotoxicity. In Specific Aim 1 we will determine the mechanisms by which sunitinib and another agent, sorafenib (Nexavar), two "multi-targeted" TKIs that not only block angiogenesis but also induce apoptosis of cancer cells, induce cardiac dysfunction. These studies are essential because they will 1) identify the specific target of the TKI, inhibition of which induces cardiomyocyte dysfunction and/or death, and 2) identify the signaling pathway(s) activated in response to the TKIs that mediate dysfunction and death. By identifying the specific target and the pathways mediating toxicity, we should be able to: a) predict cardiotoxicity of future agents that also inhibit that target; b) impact future drug design since in some instances the target, inhibition of which mediates toxicity, is not essential for tumor cell killing and the TKI can be modified to avoid these "bystander targets; c) identify novel strategies for cardioprotection in cases such as with imatinib in which the signaling pathway mediating toxicity is not central to tumor cell killing (e.g. JNKs mediate imatinib toxicity, and thus strategies to inhibit JNKs could reduce imatinib cardiotoxicity but leave tumor cell killing intact); d) alert clinicians and regulatory agencies to potential problems with agents still in development (e.g. lestaurtinib, a JAK2 inhibitor), encouraging them to prospectively examine LV function in late phase clinical trials or early post-FDA approval. The second half of this project focuses on mechanisms of repair following withdrawal of TKI therapy. We have found in the case of imatinib and sunitinib, that recovery of LV function in patients is quite dramatic after stopping the TKIs. Furthermore, in studies in mice, we have found clear-cut evidence of myocyte dropout (decline in LV mass), yet there was little evidence of excessive apoptosis, necrosis, or autophagy. It is our hypothesis that at least part of the toxicity and its reversibility are due to adverse effects of TKIs on key functions of CRSCs. Specifically, our preliminary studies will show that imatinib, which in addition to Abl also inhibits c-Kit (the receptor for stem cell factor), which is expressed on many CRSCs, markedly reduces the ability of c-Kit+ CRSCs in culture to differentiate into cardiomyocytes. Furthermore, imatinib also blocks proliferation and induces apoptosis of c-Kit(-) CRSCs (cardiac side population or SP cells). Thus in two different lineages of CRSCs, imatinib leads to dysregulation of proliferation, differentiation, and apoptosis. We will employ lentivirus-mediated gene transfer of imatinib-resistant mutants of kinases targeted by imatinib (Abl, PDGFRs, and c-Kit) to attempt to "rescue" these CRSCs from the adverse effects of imatinib, thereby identifying the critical target(s) regulating these processes. These studies should not only identify novel mechanisms of TKI cardiotoxicity, but also define factors and pathways regulating these critical CRSC functions, thereby advancing our understanding of basic stem cell biology. Finally, we will correlate these findings in vitro with studies in vivo, examining CRSC proliferation and new myocyte formation. Taken together, we believe these studies will shed light on a burgeoning problem in cancer treatment, with the hope being that with early identification and treatment of patients with TKI-induced cardiotoxicity, patients may be able to be maintained on these life-saving therapies.