Abe T, Unno M, Onogawa T, Tokui T, Kondo T N, Nakagomi R, Adachi H, Fujiwara K, Okabe M, Suzuki T, Nunoki K, Sato E, Kakyo M, Nishio T, Sugita J, Asano N, Tanemoto M, Seki M, Date F, Ono K, Kondo Y, Shiiba K, Suzuki M, Ohtani H, Shimosegawa T, Iinuma K, Nagura H, Ito S, Matsuno S
Division of Nephrology, Endocrinology, and Vascular Medicine, Department of Medicine, Tohoku University School of Medicine, Sendai, Japan.
Gastroenterology. 2001 Jun;120(7):1689-99. doi: 10.1053/gast.2001.24804.
BACKGROUND & AIMS: One approach to the development of targeted cancer chemotherapy exploits increased uptake of the agent into neoplastic cells. In this scenario, higher concentrations of the agent in cancer cells are responsible for differential killing, whereas the low concentration in normal human cells decreases side effects. The aim of this study was to isolate an organic anion transporter that is weak in normal cells, but abundantly expressed in cancer cells, to deliver the anticancer drugs to the cells.
A human liver complementary DNA (cDNA) library was screened with liver-specific transporter (LST)-1 cDNA as a probe. Northern blot analyses were performed using the isolated cDNA (termed LST-2). An LST-2-specific antibody was raised, and immunohistochemical analyses including immunoelectron microscopy were performed. Xenopus oocyte expression system was used for functional analysis. We also established a permanent cell line that consistently expresses LST-2 to examine the relationship between methotrexate uptake and sensitivity.
The isolated cDNA, LST-2, has 79.7% of overall homology with human LST-1. LST-2 exclusively expressed in the liver under normal conditions and its immunoreactivity was highest at the basolateral membrane of the hepatocytes around the central vein. Although its weak expression in the liver, LST-2 is abundantly expressed in the gastric, colon, and pancreatic cancers. On the other hand, the LST-1 was only detected in a hepatic cell line. LST-2 transports methotrexate in a saturable and dose-dependent manner. Furthermore, introduction of the LST-2 gene into mammalian cells potentiates sensitivity to methotrexate.
LST-2 is one of the prime candidate molecules for determining methotrexate sensitivity and may be a good target to deliver anticancer drugs to the gastrointestinal cancers.
靶向癌症化疗药物研发的一种方法是利用药物在肿瘤细胞中摄取增加。在这种情况下，癌细胞中较高浓度的药物导致差异杀伤，而正常人体细胞中低浓度药物则减少副作用。本研究的目的是分离一种在正常细胞中表达较弱但在癌细胞中大量表达的有机阴离子转运体，以便将抗癌药物递送至细胞。
以肝脏特异性转运体（LST）-1 cDNA为探针筛选人肝脏互补DNA（cDNA）文库。使用分离得到的cDNA（命名为LST-2）进行Northern印迹分析。制备LST-2特异性抗体，并进行包括免疫电子显微镜在内的免疫组织化学分析。使用非洲爪蟾卵母细胞表达系统进行功能分析。我们还建立了持续表达LST-2的永久细胞系，以研究甲氨蝶呤摄取与敏感性之间的关系。
分离得到的cDNA，即LST-2，与人LST-1的总体同源性为79.7%。LST-2在正常条件下仅在肝脏中表达，其免疫反应性在中央静脉周围肝细胞的基底外侧膜处最高。虽然LST-2在肝脏中表达较弱，但在胃癌、结肠癌和胰腺癌中大量表达。另一方面，LST-1仅在一种肝细胞系中检测到。LST-2以可饱和且剂量依赖的方式转运甲氨蝶呤。此外，将LST-2基因导入哺乳动物细胞可增强对甲氨蝶呤的敏感性。
LST-2是决定甲氨蝶呤敏感性的主要候选分子之一，可能是将抗癌药物递送至胃肠道癌症的良好靶点。
