Molecular and Functional Analysis of Choline Transporters and Antitumor Effects of Choline Transporter-Like Protein 1 Inhibitors in Human Pancreatic Cancer Cells.

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.

Anticancer Activity of Amb4269951, a Choline Transporter-Like Protein 1 Inhibitor, in Human Glioma Cells.

Choline transporter-like protein 1 (CTL1) is highly expressed in glioma cells, and inhibition of CTL1 function induces apoptotic cell death. Therefore, CTL1 is a potential target molecule for glioma therapy. Here, we investigated the therapeutic mechanism underlying the antitumor effects of Amb4269951, a recently discovered novel CTL1 inhibitor, in the human glioma cell line U251MG, and evaluated its in vivo effects in a mouse xenograft model. Amb4269951 inhibited choline uptake and cell viability and increased caspase-3/7 activity. CTL1-mediated choline uptake is associated with cell viability, and the functional inhibition of CTL1 by Amb4269951 may promote apoptotic cell death via ceramide-induced suppression of the expression of survivin, an apoptotic inhibitory factor. Finally, Amb4269951 demonstrated an antitumor effect in a mice xenograft model by significantly inhibiting tumor growth without any weight loss. Amb4269951 is the lead compound in the treatment of glioma and exhibits a novel therapeutic mechanism. These results may lead to the development of novel anticancer drugs targeting the choline transporter CTL1, which has a different mechanism of action than conventional anticancer drugs against gliomas.