TY - JOUR
T1 - In vivo imaging of antileukemic drug asparaginase reveals a rapid macrophage-mediated clearance from the bone marrow
AU - Van Der Meer, Laurens T.
AU - Terry, Samantha Y.A.
AU - Van Ingen Schenau, Dorette S.
AU - Andree, Kiki C.
AU - Franssen, Gerben M.
AU - Roeleveld, Debbie M.
AU - Metselaar, Josbert M.
AU - Reinheckel, Thomas
AU - Hoogerbrugge, Peter M.
AU - Boerman, Otto C.
AU - van Leeuwen, Frank N.
PY - 2017/2/1
Y1 - 2017/2/1
N2 - Maxima Center for Pediatric Oncology, Utrecht, The Netherlands The antileukemic drug asparaginase, a key component in the treatment of acute lymphoblastic leukemia, acts by depleting asparagine from the blood. However, little is known about its pharmacokinetics, and mechanisms of therapy resistance are poorly understood. Here, we explored the in vivo biodistribution of radiolabeled asparaginase, using a combination of imaging and biochemical techniques, and provide evidence for tissue-specific clearance mechanisms, which could reduce the effectiveness of the drug at these specific sites. Methods: In vivo localization of 111In-labeled Escherichia coli asparaginase was performed in C57BL/6 mice by both small-animal SPECT/CT and ex vivo biodistribution studies. Mice were treated with liposomal clodronate to investigate the effect of macrophage depletion on tracer localization and drug clearance in vivo. Moreover, macrophage cell line models RAW264.7 and THP-1, as well as knockout mice, were used to identify the cellular and molecular components controlling asparaginase pharmacokinetics. Results: In vivo imaging and biodistribution studies showed a rapid accumulation of asparaginase in macrophage-rich tissues such as the liver, spleen, and in particular bone marrow. Clodronate-mediated depletion of phagocytic cells markedly prolonged the serum half-life of asparaginase in vivo and decreased drug uptake in these macrophage-rich organs. Immunohistochemistry and in vitro binding assays confirmed the involvement of macrophagelike cells in the uptake of asparaginase. We identified the activity of the lysosomal protease cathepsin B in macrophages as a rate-limiting factor in degrading asparaginase both in vitro and in vivo. Conclusion: We showed that asparaginase is rapidly cleared from the serum by liver-, spleen-, and bone marrow-resident phagocytic cells. As a consequence of this efficient uptake and protease-mediated degradation, particularly bone marrow-resident macrophages may provide a protective niche to leukemic cells.
AB - Maxima Center for Pediatric Oncology, Utrecht, The Netherlands The antileukemic drug asparaginase, a key component in the treatment of acute lymphoblastic leukemia, acts by depleting asparagine from the blood. However, little is known about its pharmacokinetics, and mechanisms of therapy resistance are poorly understood. Here, we explored the in vivo biodistribution of radiolabeled asparaginase, using a combination of imaging and biochemical techniques, and provide evidence for tissue-specific clearance mechanisms, which could reduce the effectiveness of the drug at these specific sites. Methods: In vivo localization of 111In-labeled Escherichia coli asparaginase was performed in C57BL/6 mice by both small-animal SPECT/CT and ex vivo biodistribution studies. Mice were treated with liposomal clodronate to investigate the effect of macrophage depletion on tracer localization and drug clearance in vivo. Moreover, macrophage cell line models RAW264.7 and THP-1, as well as knockout mice, were used to identify the cellular and molecular components controlling asparaginase pharmacokinetics. Results: In vivo imaging and biodistribution studies showed a rapid accumulation of asparaginase in macrophage-rich tissues such as the liver, spleen, and in particular bone marrow. Clodronate-mediated depletion of phagocytic cells markedly prolonged the serum half-life of asparaginase in vivo and decreased drug uptake in these macrophage-rich organs. Immunohistochemistry and in vitro binding assays confirmed the involvement of macrophagelike cells in the uptake of asparaginase. We identified the activity of the lysosomal protease cathepsin B in macrophages as a rate-limiting factor in degrading asparaginase both in vitro and in vivo. Conclusion: We showed that asparaginase is rapidly cleared from the serum by liver-, spleen-, and bone marrow-resident phagocytic cells. As a consequence of this efficient uptake and protease-mediated degradation, particularly bone marrow-resident macrophages may provide a protective niche to leukemic cells.
KW - Asparaginase
KW - Cathepsin B
KW - Imaging
KW - Leukemia
KW - Macrophages
KW - n/a OA procedure
UR - http://www.scopus.com/inward/record.url?scp=85011982895&partnerID=8YFLogxK
U2 - 10.2967/jnumed.116.177741
DO - 10.2967/jnumed.116.177741
M3 - Article
C2 - 27493268
AN - SCOPUS:85011982895
SN - 0161-5505
VL - 58
SP - 214
EP - 220
JO - The Journal of nuclear medicine
JF - The Journal of nuclear medicine
IS - 2
ER -
