Perego Paola, Gatti Laura, Righetti Sabina C, Beretta Giovanni L, Carenini Nives, Corna Elisabetta, Dal Bo Laura, Tinelli Stella, Colangelo Donato, Leone Roberto, Apostoli Piero, Lombardi Luciano, Beggiolin Gino, Piazzoni Laura, Zunino Franco
Istituto Nazionale Tumori, via Venezian 1, 20133 Milan, Italy.
Int J Cancer. 2003 Jul 10;105(5):617-24. doi: 10.1002/ijc.11140.
BBR3464 is a trinuclear platinum complex that exhibits a potent cytotoxicity and efficacy against cisplatin-resistant tumors. To better understand the determinants of cellular resistance to BBR3464, we selected a resistant ovarian carcinoma cell line after exposure to the complex. The resistant cells (A2780/BBR3464) exhibited a high level of resistance to the selecting agent, but a marginal cross-resistance to cisplatin. Although cellular accumulation of BBR3464 was similar in parental and in resistant cells, DNA platination was decreased in A2780/BBR3464 cells, suggesting a reduced drug accessibility to DNA. This behavior reflected a partial drug inactivation at cytoplasmic level, as a consequence of increased levels of nucleophilic molecules including metallothioneins and human neurofilament low, but not glutathione. A2780/BBR3464 cells also exhibited a reduced susceptibility to apoptosis, which was consistent with reduced expression of Bax, and an alteration of DNA mismatch repair system, as reflected by lack of expression of MLH1 and PMS2, which could impair the recognition/repair of DNA lesions. Whereas both platinum drugs induced G2/M arrest in the parental cells, BBR3464, but not cisplatin, caused a late G1 arrest of resistant cells. Cisplatin induced an appreciable increase of p21(WAF1) levels in both models, in contrast to BBR3464 that produced a substantial upregulation of p21(WAF1) only in parental cells. An inverse relationship with p21(WAF1) modulation was found for CHK1 in parental cells treated with both agents and in resistant cells treated with cisplatin. This pattern of response is consistent with a regulatory loop involving p53 and p21(WAF1) at G2 checkpoint. In contrast, no modulation of CHK1 was found in A2780/BBR3464 treated with the triplatinum compound. These findings, indicating a different activation of regulatory pathways at DNA damage checkpoints in response to cisplatin and BBR3464, support an altered ability of resistant cells to recognize or tolerate sublethal lesions induced by BBR3464.
BBR3464是一种三核铂配合物，对顺铂耐药肿瘤表现出强大的细胞毒性和疗效。为了更好地理解细胞对BBR3464耐药的决定因素，我们在将细胞暴露于该配合物后选择了一种耐药的卵巢癌细胞系。耐药细胞（A2780/BBR3464）对选择剂表现出高度耐药性，但对顺铂仅有轻微的交叉耐药性。尽管BBR3464在亲本细胞和耐药细胞中的细胞蓄积相似，但A2780/BBR3464细胞中的DNA铂化作用减弱，这表明药物与DNA的可及性降低。这种现象反映了药物在细胞质水平的部分失活，这是由于包括金属硫蛋白和人神经丝轻链但不包括谷胱甘肽在内的亲核分子水平升高所致。A2780/BBR3464细胞对凋亡的敏感性也降低，这与Bax表达降低一致，并且DNA错配修复系统发生改变，表现为MLH1和PMS2缺乏表达，这可能会损害对DNA损伤的识别/修复。两种铂类药物均在亲本细胞中诱导G2/M期阻滞，而BBR3464而非顺铂导致耐药细胞出现晚期G1期阻滞。顺铂在两种模型中均诱导p21（WAF1）水平显著升高，相反，BBR3464仅在亲本细胞中使p21（WAF1）大量上调。在用两种药物处理的亲本细胞和用顺铂处理的耐药细胞中，发现CHK1与p21（WAF1）调节呈负相关。这种反应模式与在G2检查点涉及p53和p21（WAF1）的调节环一致。相反，在用三铂化合物处理的A2780/BBR3464中未发现CHK1的调节。这些发现表明，顺铂和BBR3464在DNA损伤检查点的调节途径激活不同，这支持了耐药细胞识别或耐受BBR3464诱导的亚致死性损伤的能力发生改变。
