Sun Yuchen, Furihata Tomomi, Ishii Seiya, Nagai Miki, Harada Manami, Shimozato Osamu, Kamijo Takehiko, Motohashi Shinichiro, Yoshino Ichiro, Kamiichi Atsuko, Kobayashi Kaoru, Chiba Kan
Laboratory of Pharmacology and Toxicology, Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana, Chuou-ku, Chiba-shi 260-8675, Chiba, Japan.
Division of Biochemistry and Molecular Carcinogenesis, Chiba Cancer Center Research Institute, Chiba, Japan.
Clin Transl Med. 2014 Nov 18;3:37. doi: 10.1186/s40169-014-0037-y. eCollection 2014.
We have previously identified the cancer-type organic anion transporting polypeptide 1B3 (Ct-OATP1B3) mRNA in several human colon and lung cancer tissues. Ct-OATP1B3 is a variant of the liver-type OATP1B3 (Lt-OATP1B3) mRNA, which is a hepatocyte plasma membrane transporter with broad substrate specificity. However, in cancer tissues, both the detailed characteristics of Ct-OATP1B3 mRNA expression and its biological functions remain unclear. With this point in mind, we sought to characterize Ct-OATP1B3 mRNA expression in colon and lung cancer tissues. In addition, we attempted to obtain functional implication of Ct-OATP1B3 in cancer cells.
Matched pairs of cancer and normal tissues were collected from 39 colon cancer and 28 lung cancer patients. The OATP1B3 mRNA expression levels in each of these tissues were separately determined by quantitative real-time polymerase chain reaction. Mann-Whitney U test and Fisher's exact test were used in statistical analysis. The Ct-OATP1B3 functional expression in colon cancer cells was then examined by Western blotting and transport analyses.
Ct-OATP1B3 mRNA, but not Lt-OATP1B3 mRNA, was abundantly expressed in colon cancer tissues at a higher detection frequency (87.2%) than that of the adjacent normal tissues (2.6%). Furthermore, it was found that Ct-OATP1B3 mRNA expression was often detected in early colon cancer stages (88.9%, n = 18), and that its expression was associated with well-differentiated colon cancer statuses. On the other hand, Ct-OATP1B3 mRNA also showed a predominant and cancer-associated expression profile in lung tissues, although at frequencies and expression levels that were lower than those obtained from colon cancer. As for attempts to clarify the Ct-OATP1B3 functions, neither protein expression nor transport activity could be observed in any of the cell lines examined.
Based on the unique characteristics of the Ct-OATP1B3 mRNA expression profile identified in this study, Ct-OATP1B3 mRNA can be expected to become a biomarker candidate for use in colon (and lung) cancer diagnosis. Simultaneously, our results advance the possibility that Ct-OATP1B3 might play yet unidentified roles, in addition to transporter function, in cancer cell biology.
我们之前在多种人类结肠癌和肺癌组织中鉴定出了癌症类型的有机阴离子转运多肽1B3（Ct-OATP1B3）mRNA。Ct-OATP1B3是肝型OATP1B3（Lt-OATP1B3）mRNA的一种变体，Lt-OATP1B3是一种具有广泛底物特异性的肝细胞质膜转运体。然而，在癌症组织中，Ct-OATP1B3 mRNA表达的详细特征及其生物学功能仍不清楚。考虑到这一点，我们试图对结肠癌和肺癌组织中Ct-OATP1B3 mRNA的表达进行表征。此外，我们还试图了解Ct-OATP1B3在癌细胞中的功能意义。
从39例结肠癌患者和28例肺癌患者中收集癌组织和正常组织的配对样本。通过定量实时聚合酶链反应分别测定这些组织中OATP1B3 mRNA的表达水平。统计分析采用曼-惠特尼U检验和费舍尔精确检验。然后通过蛋白质印迹法和转运分析检测Ct-OATP1B3在结肠癌细胞中的功能表达。
Ct-OATP1B3 mRNA在结肠癌组织中大量表达，而Lt-OATP1B3 mRNA未大量表达，其检测频率（87.2%）高于相邻正常组织（2.6%）。此外，发现Ct-OATP1B3 mRNA在结肠癌早期阶段也经常被检测到（88.9%，n = 18），并且其表达与高分化结肠癌状态相关。另一方面，Ct-OATP1B3 mRNA在肺组织中也显示出主要的且与癌症相关的表达模式，尽管其频率和表达水平低于结肠癌组织。至于试图阐明Ct-OATP1B3的功能，在所检测的任何细胞系中均未观察到蛋白质表达和转运活性。
基于本研究中鉴定出的Ct-OATP1B3 mRNA表达谱的独特特征，预计Ct-OATP1B3 mRNA可成为用于结肠癌（和肺癌）诊断的生物标志物候选物。同时，我们的结果进一步表明，除了转运体功能外，Ct-OATP1B3在癌细胞生物学中可能还发挥着尚未明确的作用。
