Cenni Vittoria, Maraldi Nadir M, Ruggeri Alessandra, Secchiero Paola, Del Coco Rosalba, De Pol Anto, Cocco Lucio, Marmiroli Sandra
Laboratory of Cell Biology and Electron Microscopy, Rizzoli Orthopedic Institute, Via di Barbiano 1/10, I-40136 Bologna, Italy.
Int J Oncol. 2004 Dec;25(6):1599-608.
Chemotherapeutic agents have been used for the treatment of patients with osteosarcoma (OS). However, inherent or acquired resistance to these agents is a serious problem in the management of OS patients. The emergence of the multidrug resistance (MDR) phenotype in cancer cells is often associated with the overexpression of P-glycoprotein, encoded by the multidrug resistance gene MDR-1. The administration of some of the most common chemotherapeutic agents to these cells becomes ineffective because of their P-gp-driven efflux from the cell. Apo2L/TRAIL is a member of the tumor necrosis factor (TNF) family of cytokines that is considered to induce death of cancer cells but not normal cells. Its powerful apoptotic activity is mediated through its cell surface death domain-containing receptors, TRAIL-R1/DR4 and TRAIL-R2/DR5, which in turn spread the signal in the cytosol through the activation of the caspase cascade. The Akt/PKB kinase is an important cell survival protein which is regulated by D3-phosphoinositides. High Akt expression and activity levels are well documented in many types of tumors, which very often show an altered PI3-K/Akt/PTEN pathway. In this study the U2OS human osteosarcoma cell line and its multidrug resistant (MDR) subline that overexpresses MDR-1 gene, MDR-U2OS, have been analyzed for their responsiveness to TRAIL. In conflict with the presence of active DR4 and DR5 receptors in both clones, U2OS cells exhibited only a low responsiveness to TRAIL, while the MDR-U2OS subline did exhibit a marked TRAIL sensitivity. An analysis of the post-receptor events showed that TRAIL responsiveness correlates with a reduced expression of endogenous Akt. In fact, expression in MDR-U2OS cells of a constitutively active Akt strongly decreased their sensitivity to TRAIL. The identification of Akt as a key modulator of TRAIL responsiveness could help to design TRAIL-based combinations for treatment of osteosarcoma. Moreover, the discovery that multidrug resistant osteosarcomas are highly sensitive to TRAIL-induced apoptosis indicates TRAIL as a new candidate for the treatment of multidrug resistant bone malignancies.
化疗药物已被用于治疗骨肉瘤（OS）患者。然而，这些药物的内在或获得性耐药是骨肉瘤患者治疗中的一个严重问题。癌细胞中多药耐药（MDR）表型的出现通常与多药耐药基因MDR - 1编码的P - 糖蛋白的过表达有关。由于这些细胞中P - gp驱动的药物外排，向这些细胞施用一些最常见的化疗药物变得无效。Apo2L/TRAIL是肿瘤坏死因子（TNF）细胞因子家族的成员，被认为可诱导癌细胞而非正常细胞死亡。其强大的凋亡活性通过其含细胞表面死亡结构域的受体TRAIL - R1/DR4和TRAIL - R2/DR5介导，这些受体进而通过激活半胱天冬酶级联反应在细胞质中传播信号。Akt/PKB激酶是一种重要的细胞存活蛋白，受D3 - 磷酸肌醇调节。在许多类型的肿瘤中，Akt的高表达和活性水平都有充分记录，这些肿瘤常常显示PI3 - K/Akt/PTEN途径发生改变。在本研究中，对人骨肉瘤细胞系U2OS及其过表达MDR - 1基因的多药耐药（MDR）亚系MDR - U2OS对TRAIL的反应性进行了分析。与两个克隆中均存在活性DR4和DR5受体的情况相反，U2OS细胞对TRAIL仅表现出低反应性，而MDR - U2OS亚系确实表现出明显的TRAIL敏感性。对受体后事件的分析表明，TRAIL反应性与内源性Akt表达的降低相关。事实上，在MDR - U2OS细胞中组成型活性Akt的表达强烈降低了它们对TRAIL的敏感性。将Akt鉴定为TRAIL反应性的关键调节因子有助于设计基于TRAIL的联合疗法来治疗骨肉瘤。此外，多药耐药骨肉瘤对TRAIL诱导的凋亡高度敏感这一发现表明TRAIL是治疗多药耐药骨恶性肿瘤的新候选药物。
