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Boronophenylalanine, a boron delivery agent for boron neutron capture therapy, is transported by ATB0,+, LAT1 and LAT2.

Wongthai P, Hagiwara K, Miyoshi Y, Wiriyasermkul P, Wei L, Ohgaki R, Kato I, Hamase K, Nagamori S, Kanai Y - Cancer Sci. (2015)

Bottom Line: Among aromatic amino acid transporters, ATB(0,+), LAT1 and LAT2 were found to transport BPA with Km values of 137.4 ± 11.7, 20.3 ± 0.8 and 88.3 ± 5.6 μM, respectively.ATB(0,+), LAT1 and LAT2 transport BPA at affinities comparable with their endogenous substrates, suggesting that they could mediate effective BPA uptake in vivo.ATB(0,+), as well as LAT1, could contribute significantly to the tumor accumulation of BPA at clinical dose.

View Article: PubMed Central - PubMed

Affiliation: Division of Bio-system Pharmacology, Department of Pharmacology, Graduate School of Medicine, Osaka University, Suita, Japan.

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Related in: MedlinePlus

Differential roles of ATB0,+ and LAT1 in p-boronophenylalanine (BPA) uptake. (a) Uptake of BPA in MCF-7 cells was measured for 10 min at 100 μM (left) and 1000 μM (right) BPA. At 1000 μM, the uptake rate in the presence of Na+ increased by ∽1.4-fold from the Na+-free uptake. (b) MCF-7 cells were transfected with non-targeting control siRNA #1 and #2, and LAT1-targeting siRNA #3, #4 and #5. The siRNAs #3–#5 achieved a ∽80% reduction of LAT1 protein amount. (c) Uptake by ATB0,+ was separated by LAT1 knockdown and lysine inhibition. The uptakes in the presence of Na+ and with mock knockdown were set at 1.0 at each BPA concentration (bars 1 and 4). At 100 μM BPA, the uptake levels with LAT1 knockdown did not differ regardless of Na+ (bars 2 and 3). At 1000 μM, LAT1 knockdown left a significant Na+-dependent component (bars 5 and 6). Overall, although with various statistical significances, the BPA uptake in bar 5 was inhibited by 5 mM lysine to a level similar to bar 6 (bar 7). This Na+-dependent and lysine-inhibitable component accounted for at least 20–25% of the total uptake. siRNA#1 was used for control siRNA. n.s., not significant.
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fig06: Differential roles of ATB0,+ and LAT1 in p-boronophenylalanine (BPA) uptake. (a) Uptake of BPA in MCF-7 cells was measured for 10 min at 100 μM (left) and 1000 μM (right) BPA. At 1000 μM, the uptake rate in the presence of Na+ increased by ∽1.4-fold from the Na+-free uptake. (b) MCF-7 cells were transfected with non-targeting control siRNA #1 and #2, and LAT1-targeting siRNA #3, #4 and #5. The siRNAs #3–#5 achieved a ∽80% reduction of LAT1 protein amount. (c) Uptake by ATB0,+ was separated by LAT1 knockdown and lysine inhibition. The uptakes in the presence of Na+ and with mock knockdown were set at 1.0 at each BPA concentration (bars 1 and 4). At 100 μM BPA, the uptake levels with LAT1 knockdown did not differ regardless of Na+ (bars 2 and 3). At 1000 μM, LAT1 knockdown left a significant Na+-dependent component (bars 5 and 6). Overall, although with various statistical significances, the BPA uptake in bar 5 was inhibited by 5 mM lysine to a level similar to bar 6 (bar 7). This Na+-dependent and lysine-inhibitable component accounted for at least 20–25% of the total uptake. siRNA#1 was used for control siRNA. n.s., not significant.

Mentions: ATB0,+ has a lower affinity to BPA than LAT1 (Table2). Thus, ATB0,+ is proposed to work at higher BPA concentrations. Consistent with this, a significant Na+-dependent uptake of BPA was observed at 1000 μM in MCF-7 cells (Fig.6a). To reduce the contribution of LAT1 to BPA uptake in MCF-7 cells, the LAT1 expression was silenced by RNA interference. Treatment of MCF-7 cells with siRNAs depleted the LAT1 protein amount to ∽20% (Fig.6b). Among the siRNAs tested, control siRNAs and LAT1 siRNAs had a similar impact on the LAT1 protein amount (Fig.6b) and BPA uptake (Fig. S2). After LAT1 was knocked down in 1000 μM BPA, the residual component was further decreased by removing Na+ and also inhibited by lysine, a high-affinity substrate of ATB0,+ (Km, ∽100 μM)21 but not interactive with LAT112 (Fig.6c). This Na+-dependent and lysine-inhibitable component is proposed to be mediated by ATB0,+. Such component was only found at 1000 μM, accounting for at least 20–25% of the total BPA uptake (Fig.6c). In 100 μM of BPA, the residual component after LAT1 knockdown was not dependent on Na+ (Fig.6c).


Boronophenylalanine, a boron delivery agent for boron neutron capture therapy, is transported by ATB0,+, LAT1 and LAT2.

Wongthai P, Hagiwara K, Miyoshi Y, Wiriyasermkul P, Wei L, Ohgaki R, Kato I, Hamase K, Nagamori S, Kanai Y - Cancer Sci. (2015)

Differential roles of ATB0,+ and LAT1 in p-boronophenylalanine (BPA) uptake. (a) Uptake of BPA in MCF-7 cells was measured for 10 min at 100 μM (left) and 1000 μM (right) BPA. At 1000 μM, the uptake rate in the presence of Na+ increased by ∽1.4-fold from the Na+-free uptake. (b) MCF-7 cells were transfected with non-targeting control siRNA #1 and #2, and LAT1-targeting siRNA #3, #4 and #5. The siRNAs #3–#5 achieved a ∽80% reduction of LAT1 protein amount. (c) Uptake by ATB0,+ was separated by LAT1 knockdown and lysine inhibition. The uptakes in the presence of Na+ and with mock knockdown were set at 1.0 at each BPA concentration (bars 1 and 4). At 100 μM BPA, the uptake levels with LAT1 knockdown did not differ regardless of Na+ (bars 2 and 3). At 1000 μM, LAT1 knockdown left a significant Na+-dependent component (bars 5 and 6). Overall, although with various statistical significances, the BPA uptake in bar 5 was inhibited by 5 mM lysine to a level similar to bar 6 (bar 7). This Na+-dependent and lysine-inhibitable component accounted for at least 20–25% of the total uptake. siRNA#1 was used for control siRNA. n.s., not significant.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4376436&req=5

fig06: Differential roles of ATB0,+ and LAT1 in p-boronophenylalanine (BPA) uptake. (a) Uptake of BPA in MCF-7 cells was measured for 10 min at 100 μM (left) and 1000 μM (right) BPA. At 1000 μM, the uptake rate in the presence of Na+ increased by ∽1.4-fold from the Na+-free uptake. (b) MCF-7 cells were transfected with non-targeting control siRNA #1 and #2, and LAT1-targeting siRNA #3, #4 and #5. The siRNAs #3–#5 achieved a ∽80% reduction of LAT1 protein amount. (c) Uptake by ATB0,+ was separated by LAT1 knockdown and lysine inhibition. The uptakes in the presence of Na+ and with mock knockdown were set at 1.0 at each BPA concentration (bars 1 and 4). At 100 μM BPA, the uptake levels with LAT1 knockdown did not differ regardless of Na+ (bars 2 and 3). At 1000 μM, LAT1 knockdown left a significant Na+-dependent component (bars 5 and 6). Overall, although with various statistical significances, the BPA uptake in bar 5 was inhibited by 5 mM lysine to a level similar to bar 6 (bar 7). This Na+-dependent and lysine-inhibitable component accounted for at least 20–25% of the total uptake. siRNA#1 was used for control siRNA. n.s., not significant.
Mentions: ATB0,+ has a lower affinity to BPA than LAT1 (Table2). Thus, ATB0,+ is proposed to work at higher BPA concentrations. Consistent with this, a significant Na+-dependent uptake of BPA was observed at 1000 μM in MCF-7 cells (Fig.6a). To reduce the contribution of LAT1 to BPA uptake in MCF-7 cells, the LAT1 expression was silenced by RNA interference. Treatment of MCF-7 cells with siRNAs depleted the LAT1 protein amount to ∽20% (Fig.6b). Among the siRNAs tested, control siRNAs and LAT1 siRNAs had a similar impact on the LAT1 protein amount (Fig.6b) and BPA uptake (Fig. S2). After LAT1 was knocked down in 1000 μM BPA, the residual component was further decreased by removing Na+ and also inhibited by lysine, a high-affinity substrate of ATB0,+ (Km, ∽100 μM)21 but not interactive with LAT112 (Fig.6c). This Na+-dependent and lysine-inhibitable component is proposed to be mediated by ATB0,+. Such component was only found at 1000 μM, accounting for at least 20–25% of the total BPA uptake (Fig.6c). In 100 μM of BPA, the residual component after LAT1 knockdown was not dependent on Na+ (Fig.6c).

Bottom Line: Among aromatic amino acid transporters, ATB(0,+), LAT1 and LAT2 were found to transport BPA with Km values of 137.4 ± 11.7, 20.3 ± 0.8 and 88.3 ± 5.6 μM, respectively.ATB(0,+), LAT1 and LAT2 transport BPA at affinities comparable with their endogenous substrates, suggesting that they could mediate effective BPA uptake in vivo.ATB(0,+), as well as LAT1, could contribute significantly to the tumor accumulation of BPA at clinical dose.

View Article: PubMed Central - PubMed

Affiliation: Division of Bio-system Pharmacology, Department of Pharmacology, Graduate School of Medicine, Osaka University, Suita, Japan.

Show MeSH
Related in: MedlinePlus