PDF(Pubmed)
Abstract：
Gemcitabine (2\',2\'-difluoro-2\'-deoxycytidine), a widely used anticancer drug, is considered a gold standard in treating aggressive pancreatic cancers. Gamma-proteobacteria that colonize the pancreatic tumors contribute to chemoresistance against gemcitabine by metabolizing the drug to a less active and deaminated form. The gemcitabine transporters of these bacteria are unknown to date. Furthermore, there is no complete knowledge of the gemcitabine transporters in Escherichia coli or any other related proteobacteria. In this study, we investigate the complement of gemcitabine transporters in E. coli K-12 and two common chemoresistance-related bacteria (Klebsiella pneumoniae and Citrobacter freundii). We found that E. coli K-12 has two high-affinity gemcitabine transporters with distinct specificity properties, namely, NupC and NupG, whereas the gemcitabine transporters of C. freundii and K. pneumoniae include the NupC and NupG orthologs, functionally indistinguishable from their counterparts, and, in K. pneumoniae, one additional NupC variant, designated KpNupC2. All these bacterial transporters have a higher affinity for gemcitabine than their human counterparts. The highest affinity (KM 2.5-3.0 μΜ) is exhibited by NupGs of the bacteria-specific nucleoside-H+ symporter (NHS) family followed by NupCs (KM 10-13 μΜ) of the concentrative nucleoside transporter (CNT) family, 15-100 times higher than the affinities reported for the human gemcitabine transporter hENT1/SLC29A1, which is primarily associated with gemcitabine uptake in the pancreatic adenocarcinoma cells. Our results offer a basis for further insight into the role of specific bacteria in drug availability within tumors and for understanding the structure-function differences of bacterial and human drug transporters.
摘要：
吉西他滨（2\'，2\'-二氟-2\'-脱氧胞苷)，一种广泛使用的抗癌药物，被认为是治疗侵袭性胰腺癌的黄金标准。定植于胰腺肿瘤的γ-蛋白细菌通过将药物代谢为活性较低和脱氨基形式而导致针对吉西他滨的化学抗性。这些细菌的吉西他滨转运蛋白迄今未知。此外，对大肠杆菌或任何其他相关变形杆菌中的吉西他滨转运蛋白没有完全了解。在这项研究中,我们研究了吉西他滨转运体在大肠杆菌K-12和两种常见的化学耐药相关细菌(肺炎克雷伯菌和弗氏柠檬酸杆菌)中的补体。我们发现大肠杆菌K-12有两个高亲和力吉西他滨转运体具有不同的特异性，即,NupC和NupG,而弗氏梭菌和肺炎克雷伯菌的吉西他滨转运体包括NupC和NupG直向同源物，在功能上与它们的对应物没有区别，and,在肺炎克雷伯菌中，一个额外的NupC变体，指定为KpNupC2。所有这些细菌转运蛋白对吉西他滨的亲和力高于其人类对应物。细菌特异性核苷H转运体（NHS）家族的NupG表现出最高的亲和力（KM2.5-3.0μM），其次是浓缩核苷转运蛋白（CNT）家族的NupC（KM10-13μM），比人吉西他滨转运体hENT1/SLC29A1报道的亲和力高15-100倍，这主要与胰腺腺癌细胞中的吉西他滨摄取有关。我们的结果为进一步了解特定细菌在肿瘤内药物利用中的作用以及了解细菌和人类药物转运蛋白的结构功能差异提供了基础。
