Identification and Targeting Therapy Resistant Osteosarcoma

描述(申请人提供)：骨肉瘤(OS)是一种侵袭性骨癌，主要影响儿童和青少年。标准的OS治疗包括手术前后的化疗和积极的手术切除。尽管如此，约30%的局部疾病患者和80%的转移性疾病患者在确诊时将因肿瘤进展或复发而失败治疗并死亡。治疗失败的主要原因是肿瘤治疗耐药性的产生。显然，重要的是确定OS耐药的分子基础，以及靶向治疗耐药细胞的方法。30多年来，顺铂(CP)一直是OS的主要治疗药物，尽管CP的耐药机制仍不清楚。我们从OS细胞中建立了顺铂(CP)抗性克隆，并将它们与敏感克隆进行了比较。抗性克隆经CP处理后，P53基因表达水平降低，活性降低。抗性克隆也表现出在CP处理后DNA损伤反应增强，包括DNA修复和ATM-ATR-CHK1/2损伤反应通路的增强/延长激活。重要的是，我们确定了激活p53和p73的小分子MDM2拮抗剂(Nutlin-3，MI-319)可以有效地杀死CP抗性的OS克隆。此外，我们还观察到一种小分子Chk1抑制剂(UCN01)可以使多个耐药的OS细胞株和选定的克隆对CP增敏。基于这些发现，我们假设1)在OS中CP耐药将与P53或P73的低水平/激活、DNA损伤反应增强和DNA修复有关，以及2)MDM2拮抗剂和/或Chk1抑制剂将有效地靶向CP耐药的OS，并将在人类OS肿瘤复发的新动物模型中阻止肿瘤的再生长。

DESCRIPTION (provided by applicant): Osteosarcoma (OS) is an aggressive bone cancer that primarily affects children and adolescents. Standard OS treatment includes pre- and post-operative chemotherapy and aggressive surgical resection. Nonetheless, approximately 30% of patients with localized disease and 80% of patients with metastatic disease at diagnosis will fail therapy and die due to tumor progression or relapse. The main reason for treatment failure is the development of tumor therapy resistance. Clearly, it is important to identify the molecular basis for therapy resistance in OS, and ways to target therapy resistant cells. Cisplatin (CP) has been a mainstay OS therapy agent for over 30 yrs, though mechanisms for resistance to CP remain ill-defined. We established Cisplatin (CP) resistant clones from OS cells and compared them with sensitive counterparts. P53 was induced to a lower level and less active after CP in resistant clones. Resistant clones also displayed a heightened DNA damage response after CP treatment that included DNA repair and heightened/prolonged activation of the ATM-ATR-CHK1/2 damage response pathways. Importantly, we determined that small molecule MDM2 antagonists that activate p53 and p73 and which are currently in clinical development (Nutlin-3, MI-319) could effectively kill the CP resistant OS clones. Moreover, we observed that a small molecule Chk1 inhibitor (UCN01) could sensitize multiple resistant OS cell lines and selected clones to CP. Based on these findings, we hypothesize 1) that CP resistance in OS will associate with lower levels/activation of p53 or p73, a heightened DNA damage response, and DNA repair, and 2) that MDM2 antagonists and/or Chk1 inhibitors will effectively target CP resistant OS, and will block tumor regrowth in a novel animal model of human OS tumor recurrence.