Institute of Medical Science, Tokyo Medical University, 6-1-1 Shinjuku, Shinjuku-ku, Tokyo 160-8402, Japan.
Department of Molecular Preventive Medicine, Tokyo Medical University, 6-1-1 Shinjuku, Shinjuku-ku, Tokyo 160-8402, Japan.
Int J Mol Sci. 2020 Jul 22;21(15):5190. doi: 10.3390/ijms21155190.
Choline, an organic cation, is one of the biofactors that play an important role in the structure and the function of biological membranes, and it is essential for the synthesis of phospholipids. Choline positron emission tomography-computed tomography (PET/CT) provides useful information for the imaging diagnosis of cancers, and increased choline accumulation has been identified in a variety of tumors. However, the molecular mechanisms of choline uptake and choline transporters in pancreatic cancer have not been elucidated. Here, we examined molecular and functional analyses of choline transporters in human pancreatic-cancer cell line MIA PaCa-2 and the elucidation of the action mechanism behind the antitumor effect of novel choline-transporter-like protein 1 (CTL1) inhibitors, Amb4269951 and its derivative Amb4269675. CTL1 and CTL2 mRNAs were highly expressed in MIA PaCa-2 cells, and CTL1 and CTL2 proteins were localized in the plasma membrane and the intracellular compartments, respectively. Choline uptake was characterized by Na-independence, a single-uptake mechanism, and inhibition by choline-uptake inhibitor HC-3, similar to the function of CTL1. These results suggest that the uptake of extracellular choline in MIA PaCa-2 cells is mediated by CTL1. Choline deficiency and HC-3 treatment inhibited cell viability and increased caspase 3/7 activity, suggesting that the inhibition of CTL1 function, which is responsible for choline transport, leads to apoptosis-induced cell death. Both Amb4269951 and Amb4269675 inhibited choline uptake and cell viability and increased caspase-3/7 activity. Ceramide, which is increased by inhibiting choline uptake, also inhibited cell survival and increased caspase-3/7 activity. Lastly, both Amb4269951 and Amb4269675 significantly inhibited tumor growth in a mouse-xenograft model without any adverse effects such as weight loss. CTL1 is a target molecule for the treatment of pancreatic cancer, and its inhibitors Amb4269951 and Amb4269675 are novel lead compounds.
胆碱是一种有机阳离子，是生物膜结构和功能的重要生物因子之一，也是磷脂合成所必需的。胆碱正电子发射断层扫描-计算机断层扫描（PET/CT）为癌症的成像诊断提供了有用的信息，并且已经在各种肿瘤中发现了胆碱的积累增加。然而，胰腺癌中胆碱摄取和胆碱转运体的分子机制尚未阐明。在这里，我们研究了人胰腺癌细胞系 MIA PaCa-2 中胆碱转运体的分子和功能分析，并阐明了新型胆碱转运蛋白样蛋白 1（CTL1）抑制剂 Amb4269951 及其衍生物 Amb4269675 的抗肿瘤作用机制。CTL1 和 CTL2 mRNA 在 MIA PaCa-2 细胞中高表达，CTL1 和 CTL2 蛋白分别定位于质膜和细胞内区室。胆碱摄取具有 Na 非依赖性、单一摄取机制和胆碱摄取抑制剂 HC-3 的抑制作用，类似于 CTL1 的功能。这些结果表明，MIA PaCa-2 细胞中外源性胆碱的摄取是由 CTL1 介导的。胆碱缺乏和 HC-3 处理抑制细胞活力并增加 caspase 3/7 活性，表明负责胆碱转运的 CTL1 功能的抑制导致凋亡诱导的细胞死亡。Amb4269951 和 Amb4269675 均抑制胆碱摄取和细胞活力，并增加 caspase-3/7 活性。通过抑制胆碱摄取而增加的神经酰胺也抑制细胞存活并增加 caspase-3/7 活性。最后，Amb4269951 和 Amb4269675 均显著抑制荷瘤小鼠模型中的肿瘤生长，而没有体重减轻等不良反应。CTL1 是治疗胰腺癌的靶分子，其抑制剂 Amb4269951 和 Amb4269675 是新型先导化合物。
