Role of proton-coupled folate transporter in pemetrexed resistance of mesothelioma: clinical evidence and new pharmacological tools
Role of proton-coupled folate transporter in pemetrexed resistance of mesothelioma: clinical evidence and new pharmacological tools
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DOI：
10.1093/annonc/mdx499
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发表时间：
2017-11-01
影响因子：
50.5
通讯作者：
Peters, G. J.
中科院分区：
文献类型：
--
作者：
Giovannetti, E.;Zucali, P. A.;Peters, G. J.
胸苷酸合成酶（TS）在培美曲塞治疗间皮瘤中的预测作用；然而，其他的化学耐药机制尚不清楚。在这里，我们探讨了叶酸载体（RFC/SLC19A1）和质子偶联叶酸转运体（PCFT/SLC46A1）在间皮瘤抗叶酸耐药中的作用。分别采用冷冻组织定量RT-PCR和组织微阵列免疫组化检测两组培美曲塞治疗患者的PCFT、RFC和TS RNA及PCFT蛋白水平。数据分析采用t检验、Fisher’s/log-rank检验和Cox比例模型。通过5-aza-2'-脱氧胞苷介导的去甲基化和sirna敲低，在间皮瘤细胞和球体中评估PCFT表达和PCFT启动子甲基化对培美曲塞活性的贡献。在试验（N = 73, 11.3个月对20.1个月，P = 0.01）和验证（N = 51, 12.6个月对30.3个月，P = 0.02）队列中，培美喋呤治疗的低PCFT患者的疾病控制率显著降低，总生存期（OS）较短。多因素分析证实了与pcft无关的预后作用。低pcft蛋白水平也与较短的OS相关。低pcft和高ts水平的患者预后最差（OS， 5.5个月），而RFC和未经培美曲塞治疗的患者均未发现关联。PCFT沉默降低了培美曲塞的敏感性，而5-aza-2'-脱氧胞苷克服了耐药性。这些发现首次确定了PCFT作为一种新的间皮瘤预后生物标志物，促进了对其有效性的前瞻性试验。此外，临床前数据表明，靶向pcft启动子甲基化可能会根除以低pcft表达为特征的培美曲塞耐药细胞。
Thymidylate synthase (TS) has a predictive role in pemetrexed treatment of mesothelioma; however, additional chemoresistance mechanisms are poorly understood. Here, we explored the role of the reduced-folate carrier (RFC/SLC19A1) and proton-coupled folate transporter (PCFT/SLC46A1) in antifolate resistance in mesothelioma.PCFT, RFC and TS RNA and PCFT protein levels were determined by quantitative RT-PCR of frozen tissues and immunohistochemistry of tissue-microarrays, respectively, in two cohorts of pemetrexed-treated patients. Data were analyzed by t-test, Fisher's/log-rank test and Cox proportional models. The contribution of PCFT expression and PCFT-promoter methylation to pemetrexed activity were evaluated in mesothelioma cells and spheroids, through 5-aza-2'-deoxycytidine-mediated demethylation and siRNA-knockdown.Pemetrexed-treated patients with low PCFT had significantly lower rates of disease control, and shorter overall survival (OS), in both the test (N = 73, 11.3 versus 20.1 months, P = 0.01) and validation (N = 51, 12.6 versus 30.3 months, P = 0.02) cohorts. Multivariate analysis confirmed PCFT-independent prognostic role. Low-PCFT protein levels were also associated with shorter OS. Patients with both low-PCFT and high-TS levels had the worst prognosis (OS, 5.5 months), whereas associations were neither found for RFC nor in pemetrexed-untreated patients. PCFT silencing reduced pemetrexed sensitivity, whereas 5-aza-2'-deoxycytidine overcame resistance.These findings identify for the first time PCFT as a novel mesothelioma prognostic biomarker, prompting prospective trials for its validation. Moreover, preclinical data suggest that targeting PCFT-promoter methylation might eradicate pemetrexed-resistant cells characterized by low-PCFT expression.