Pharmacological inhibition of mTORC1 increases CCKBR-specific tumor uptake of radiolabeled minigastrin analogue [ 177 Lu]Lu-PP-F11N

作者：Michal Grzmil, Yun Qin, Carina Schleuniger, Stephan Frank, Stefan Imobersteg, Alain Blanc, Martin Spillmann, Philipp Berger, Roger Schibli, Martin Béhé · 发表于：Theranostics · 年份：2020 · DOI：10.7150/thno.45440 · 被引用次数：20 · 研究领域：Lung Cancer Treatments and Mutations、PI3K/AKT/mTOR signaling in cancer、Radiopharmaceutical Chemistry and Applications

Rationale: A high tumor-to-healthy-tissue uptake ratio of radiolabeled ligands is an essential prerequisite for safe and effective peptide receptor radionuclide therapy (PRRT). In the present study, we searched for novel opportunities to increase tumor-specific uptake of the radiolabeled minigastrin analogue [ 177 Lu]Lu-DOTA-(DGlu)6-Ala-Tyr-Gly-Trp-Nle-Asp-Phe-NH2 ([ 177 Lu]Lu-PP-F11N), that targets the cholecystokinin B receptor (CCKBR) in human cancers. Methods: A kinase inhibitor library screen followed by proliferation and internalization assays were employed to identify compounds which can increase uptake of [ 177 Lu]Lu-PP-F11N in CCKBR-transfected human epidermoid carcinoma A431 cells and natural CCKBR-expressing rat pancreatic acinar AR42J cells. Western blot (WB) analysis verified the inhibition of the signaling pathways and the CCKBR level, whereas the cell-based assay analyzed arrestin recruitment. Biodistribution and SPECT imaging of the A431/CCKBR xenograft mouse model as well as histological analysis of the dissected tumors were used for in vivo validation. Results: Our screen identified the inhibitors of mammalian target of rapamycin complex 1 (mTORC1), which increased cell uptake of [ 177 Lu]Lu-PP-F11N. Pharmacological mTORC1 inhibition by RAD001 and metformin increased internalization of [ 177 Lu]Lu-PP-F11N in A431/CCKBR and in AR42J cells. Analysis of protein lysates from RAD001-treated cells revealed increased levels of CCKBR (2.2-fold) and inhibition of S6 ...