Research ArticleHEALTH AND MEDICINE

Poly(vinyl alcohol) boosting therapeutic potential of p-boronophenylalanine in neutron capture therapy by modulating metabolism

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Science Advances  22 Jan 2020:
Vol. 6, no. 4, eaaz1722
DOI: 10.1126/sciadv.aaz1722
  • Fig. 1 Schematic illustration of influx and efflux of BPA.

    (A) Molecular structure of BPA (white-, gray-, red-, blue-, and pink-colored atoms are H, C, O, N, and B, respectively). (B) Cell internalization of BPA through the LAT1 transporter. LAT1 imports extracellular BPA and exports intracellular substrates including glutamine. (C) Efflux of intracellular BPA. When extracellular concentration of BPA decreases, intracellular BPA could be exchanged with an extracellular substrate including tyrosine. (D) Chemical structure of PVA and PVA-BPA. PVA-BPA formation does not involve phenylalanine structure in BPA, which is critical for recognition by LAT1. (E) Internalization pathway of PVA-BPA. PVA-BPA is expected to interact with LAT1, followed by internalization through endocytosis.

  • Fig. 2 Cellular uptake and subcellular localization.

    (A) Confocal laser scanning microscopic images of BxPC-3 cells incubated with fructose-BPA and Cy5-labeled PVA-BPA. BPA and endo-/lysosomes were labeled using DAHMI and LysoTracker Red DND-99, respectively. Control cells were treated with DAHMI and LysoTracker Red DND-99. BPA (DAHMI), Cy5-labeled PVA, and endo-/lysosomes (LysoTracker Red DND-99) are shown in blue, red, and green, respectively. White arrows indicate representative colocalization of DAHMI, Cy5, and LysoTracker Red DND-99. (B) Cellular uptake of BPA. BxPC-3 cells were incubated with BPA for 3 hours without/with system L inhibitor (BCH). The results are expressed as means ± SD (n = 3). *P < 0.05 and **P < 0.001 (Neuman-Keuls test). (C) Intracellular retention of BPA. The cells were incubated with BPA for 3 hours without/with additional incubation in fresh medium without BPA. The results without the additional incubation are the same with those shown in (B). The results are expressed as means ± SD (n = 3).

  • Fig. 3 Biodistribution and intratumoral distribution.

    (A) Tumor accumulation within a subcutaneous hypovascular BxPC-3 tumor in a BALB/c nude mouse. The results are expressed as means ± SD (n = 4). *P < 0.01 and **P < 0.001 (Tukey post hoc test). (B) Tumor accumulation within a subcutaneous hypervascular CT26 tumor in a BALB/c mouse. The results are expressed as means ± SD (n = 4). **P < 0.001 (Tukey post hoc test). (C and D) Distribution to normal organs of (C) PVA-BPA and (D) fructose-BPA. The results are expressed as means ± SD (n = 4). (E) Distribution to normal organs 24 hours after administration. The results are expressed as means ± SD (n = 3). (F and G) Intratumoral distribution of Cy5-labeled PVA-BPA in (F) a BxPC-3 tumor model and (G) a CT26 tumor model. Nuclei and blood vessels were labeled with intravenously injected Hoechst 33342– and DyLight 488–conjugated tomato lectin, respectively.

  • Fig. 4 Antitumor effect in a subcutaneous hypovascular BxPC-3 tumor model.

    (A) Tumor growth curves. The indicated samples were intravenously injected, and the tumors were irradiated with epi-/thermal neutrons 3 hours after injection on day 0. The results are expressed as means ± SD (n = 8 for control; n = 6 for fructose-BPA and PVA-BPA). *P < 0.05 (one-way Student’s t test). (B and C) Individual tumor growth treated with (B) fructose-BPA and (C) PVA-BPA.

  • Fig. 5 Antitumor effect in a subcutaneous hypervascular CT26 tumor model.

    (A and B) Tumor growth curves. The indicated samples were intravenously injected, and the tumors were irradiated with epi-/thermal neutrons 3 or 6 hours after injection on day 1. The results are expressed as means ± SD. *P < 0.05, **P < 0.00001, and ***P < 0.00000001 (Bonferroni method) in (A). N.S., not significant. **P < 0.0001 and ***P < 0.000001 (Bonferroni method) in (B). (C) Body weight. The results are expressed as means ± SD. (D and E) Histology (hematoxylin and eosin) of tumors treated by BNCT with (D) fructose-BPA and (E) PVA-BPA (3-hour interval). The tumors were collected 25 days after the treatment. The dashed rectangle in (D) indicates a representative damaged region characterized by shrinkage of nuclei.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/6/4/eaaz1722/DC1

    Fig. S1. Synthetic scheme of PVAc and PVA.

    Fig. S2. GPC chart of PVAc.

    Fig. S3. 1H NMR spectrum of PVAc in DMSO-d6.

    Fig. S4. GPC chart of PVA.

    Fig. S5. 1H NMR spectrum of PVA in DMSO-d6.

    Fig. S6. 11B NMR spectra of BPA, fructose-BPA, and PVA-BPA.

    Fig. S7. T/B ratios in BxPC-3 and CT26 tumor models.

    Fig. S8. Tumor accumulation of fructose-19F-BPA and PVA-19F-BPA in subcutaneous CT26 tumor models.

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Synthetic scheme of PVAc and PVA.
    • Fig. S2. GPC chart of PVAc.
    • Fig. S3. 1H NMR spectrum of PVAc in DMSO-d6.
    • Fig. S4. GPC chart of PVA.
    • Fig. S5. 1H NMR spectrum of PVA in DMSO-d6.
    • Fig. S6. 11B NMR spectra of BPA, fructose-BPA, and PVA-BPA.
    • Fig. S7. T/B ratios in BxPC-3 and CT26 tumor models.
    • Fig. S8. Tumor accumulation of fructose-19F-BPA and PVA-19F-BPA in subcutaneous CT26 tumor models.

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