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anti-Na /K ATPase α1
Control siRNA siRNA
Fig. 6. Incorporation of BPA-Tyr and Tyr-BPA into tumor Maresin 1 via PEPT1 assessed by knockdown. (A) The knockdown of PEPT1 was confirmed by western blot analysis using the crude membrane fraction of AsPC-1 cells transfected with non-targeting control siRNA, PEPT1-targeting siRNA #1 or PEPT1-targeting siRNA #2. Naþ/Kþ ATPase a1 was detected as a loading control. (B) [3H]Gly-Sar uptake (10 mM) was measured for 10 min in AsPC-1 cells transfected with non-targeting control siRNA, PEPT1-targeting siRNA #1 or PEPT1-targeting siRNA #2. Boron contents were measured by ICP-AES after the treatment with 500 mM BPA-Tyr (C) or 500 mM Tyr-BPA (D) for 10 min in AsPC-1 cells transfected with non-targeting
Fig. 7. Boron accumulation in xenograft tumors in vivo after BPA-Tyr adminis-
tration. Boron contents in tumor (open columns) and blood (closed columns) were
In conclusion, our present study proposes that the oligo-peptide transporters, especially PEPT1, are promising candidates for a novel molecular target of BNCT. BPA-containing dipeptides have a great potential for the development of novel boron car-riers targeting PEPT1. BNCT using the dipeptide-based boron compounds may become an alternative therapeutic option that can be applied to the patients with less responding to BPA-BNCT because of the low expression of LAT1 responsible for BPA accumulation in tumor cells. In BPA-BNCT, 18F-BPA PET tracer is currently used for patient selection.33 Likewise, it may be also possible to introduce 18F into BPA-containing dipeptide to develop a dipeptide PET tracer for the prediction of therapeutic efficacy. It is also worth considering a dual transporter-targeting strategy in which the dipeptide-based boron compounds and BPA are used in combination to increase the 10B accumulation in cancer lesions.
Conflict of interest
The authors declare no conflicts of interest.
Authors thank Ms. Miyuki Kurauchi and Ms. Ayaka Adachi for technical assistance. We also thank Dr. Hiroshi Furutani and Mr. Shigeru Tamiya (Center for Scientific Instrument Renovation and Manufacturing Support, Osaka University) for ICP-AES. This work was supported by Grants-in-Aid for Scientific Research [15H04685 and 18K19429 to Y.K.; 10680486 and 12680507 to K.Y.] from the Japan Society for the Promotion of Science, and by the Project for Cancer Research And Therapeutic Evolution [JP16cm0106118 and JP18cm0106131 to Y.K.] from the Japan Agency for Medical Research and Development. Appendix A. Supplementary data
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