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Autophagy collaborates with ubiquitination to downregulate oncoprotein E2A/Pbx1 in B-cell acute lymphoblastic leukemia.

Yuan N, Song L, Lin W, Cao Y, Xu F, Liu S, Zhang A, Wang Z, Li X, Fang Y, Zhang H, Zhao W, Hu S, Wang J, Zhang S - Blood Cancer J (2015)

Bottom Line: With a pediatric t(1;19) B-ALL xenograft mouse model, we show here that activation of autophagy by preventive administration of rapamycin improved the survival of leukemia animals by partial restoration of hematopoietic stem/progenitor cells, whereas treatment of the animals with rapamycin caused leukemia bone marrow cell-cycle arrest.Activation of autophagy in vitro or in vivo by rapamycin or starvation downregulated oncogenic fusion protein E2A/Pbx1.Furthermore, E2A/Pbx1 was found to be colocalized with autophagy marker LC3 in autolysosomes and with ubiquitin in response to autophagy stimuli, whereas autophagy or ubiquitination inhibitor blocked these colocalizations.

View Article: PubMed Central - PubMed

Affiliation: Hematology Center of Cyrus Tang Medical Institute, Jiangsu Institute of Hematology, Jiangsu Key Laboratory for Stem Cell Research, Collaborative Innovation Center of Hematology, Affiliated Children's Hospital, Soochow University School of Medicine, Suzhou, China.

ABSTRACT
B-cell acute lymphoblastic leukemia (B-ALL) accounts for the most cancer incidences in children. We present here that autophagy is downregulated in pediatric B-ALL, suggesting a possible link between autophagy failure and pediatric B-ALL leukemogenesis. With a pediatric t(1;19) B-ALL xenograft mouse model, we show here that activation of autophagy by preventive administration of rapamycin improved the survival of leukemia animals by partial restoration of hematopoietic stem/progenitor cells, whereas treatment of the animals with rapamycin caused leukemia bone marrow cell-cycle arrest. Activation of autophagy in vitro or in vivo by rapamycin or starvation downregulated oncogenic fusion protein E2A/Pbx1. Furthermore, E2A/Pbx1 was found to be colocalized with autophagy marker LC3 in autolysosomes and with ubiquitin in response to autophagy stimuli, whereas autophagy or ubiquitination inhibitor blocked these colocalizations. Together, our data suggest a collaborative action between autophagy and ubiquitination in the degradation of E2A/Pbx1, thereby revealing a novel strategy for targeted preventive or treatment therapy on the pediatric ALL.

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Activation of autophagy before or after transplantation of B cell leukemia cells prolonged the survival of xenograft mice. The mice were divided into four groups: control (C), preventive group (P, rapamycin administrated before human B-ALL cell transplantation), model group (M, no rapamycin administrated before or after the B-ALL cell transplantation) and treatment group (T, rapamycin administrated 1 week after B-ALL cell transplantation). The survival curve (b) showed that activation of autophagy by rapamycin in the preventive and treatment group prolonged 5–9 days of the survival time compared with model group (with 10 mice in each group). The autophagy level (a, Beclin1 and LC3 expression), peripheral blood cell counting (c), the size and coefficient of liver and spleen (d), the pathological section of liver (e), B-ALL immune typing of human CD45, CD19 and CD10 expression in mice (f) were showed. It indicated that rapamycin slowed down the malignant transformation of leukemia cells in NOD-SCID mice. ***P<0.001, **P<0.01, *P<0.05.
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fig2: Activation of autophagy before or after transplantation of B cell leukemia cells prolonged the survival of xenograft mice. The mice were divided into four groups: control (C), preventive group (P, rapamycin administrated before human B-ALL cell transplantation), model group (M, no rapamycin administrated before or after the B-ALL cell transplantation) and treatment group (T, rapamycin administrated 1 week after B-ALL cell transplantation). The survival curve (b) showed that activation of autophagy by rapamycin in the preventive and treatment group prolonged 5–9 days of the survival time compared with model group (with 10 mice in each group). The autophagy level (a, Beclin1 and LC3 expression), peripheral blood cell counting (c), the size and coefficient of liver and spleen (d), the pathological section of liver (e), B-ALL immune typing of human CD45, CD19 and CD10 expression in mice (f) were showed. It indicated that rapamycin slowed down the malignant transformation of leukemia cells in NOD-SCID mice. ***P<0.001, **P<0.01, *P<0.05.

Mentions: To examine whether in vivo enhancement of autophagy is capable of fighting against B-ALL cells, we generated a human leukemia xenograft mouse model with B-ALL 697 cells. Ten mice each were used for survival curve in the four groups (control, model, preventative and treatment) administered with or without rapamycin as described in the Materials and methods. Western blotting analysis showed that LC3 lipidation, a typical autophagy activity indicator,20 was enhanced in the preventive or treatment groups, suggesting that rapamycin treatment ahead of, or right after B-ALL cell transplantation, activates or enhances autophagy response in the mouse models (Figure 2a).


Autophagy collaborates with ubiquitination to downregulate oncoprotein E2A/Pbx1 in B-cell acute lymphoblastic leukemia.

Yuan N, Song L, Lin W, Cao Y, Xu F, Liu S, Zhang A, Wang Z, Li X, Fang Y, Zhang H, Zhao W, Hu S, Wang J, Zhang S - Blood Cancer J (2015)

Activation of autophagy before or after transplantation of B cell leukemia cells prolonged the survival of xenograft mice. The mice were divided into four groups: control (C), preventive group (P, rapamycin administrated before human B-ALL cell transplantation), model group (M, no rapamycin administrated before or after the B-ALL cell transplantation) and treatment group (T, rapamycin administrated 1 week after B-ALL cell transplantation). The survival curve (b) showed that activation of autophagy by rapamycin in the preventive and treatment group prolonged 5–9 days of the survival time compared with model group (with 10 mice in each group). The autophagy level (a, Beclin1 and LC3 expression), peripheral blood cell counting (c), the size and coefficient of liver and spleen (d), the pathological section of liver (e), B-ALL immune typing of human CD45, CD19 and CD10 expression in mice (f) were showed. It indicated that rapamycin slowed down the malignant transformation of leukemia cells in NOD-SCID mice. ***P<0.001, **P<0.01, *P<0.05.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4314458&req=5

fig2: Activation of autophagy before or after transplantation of B cell leukemia cells prolonged the survival of xenograft mice. The mice were divided into four groups: control (C), preventive group (P, rapamycin administrated before human B-ALL cell transplantation), model group (M, no rapamycin administrated before or after the B-ALL cell transplantation) and treatment group (T, rapamycin administrated 1 week after B-ALL cell transplantation). The survival curve (b) showed that activation of autophagy by rapamycin in the preventive and treatment group prolonged 5–9 days of the survival time compared with model group (with 10 mice in each group). The autophagy level (a, Beclin1 and LC3 expression), peripheral blood cell counting (c), the size and coefficient of liver and spleen (d), the pathological section of liver (e), B-ALL immune typing of human CD45, CD19 and CD10 expression in mice (f) were showed. It indicated that rapamycin slowed down the malignant transformation of leukemia cells in NOD-SCID mice. ***P<0.001, **P<0.01, *P<0.05.
Mentions: To examine whether in vivo enhancement of autophagy is capable of fighting against B-ALL cells, we generated a human leukemia xenograft mouse model with B-ALL 697 cells. Ten mice each were used for survival curve in the four groups (control, model, preventative and treatment) administered with or without rapamycin as described in the Materials and methods. Western blotting analysis showed that LC3 lipidation, a typical autophagy activity indicator,20 was enhanced in the preventive or treatment groups, suggesting that rapamycin treatment ahead of, or right after B-ALL cell transplantation, activates or enhances autophagy response in the mouse models (Figure 2a).

Bottom Line: With a pediatric t(1;19) B-ALL xenograft mouse model, we show here that activation of autophagy by preventive administration of rapamycin improved the survival of leukemia animals by partial restoration of hematopoietic stem/progenitor cells, whereas treatment of the animals with rapamycin caused leukemia bone marrow cell-cycle arrest.Activation of autophagy in vitro or in vivo by rapamycin or starvation downregulated oncogenic fusion protein E2A/Pbx1.Furthermore, E2A/Pbx1 was found to be colocalized with autophagy marker LC3 in autolysosomes and with ubiquitin in response to autophagy stimuli, whereas autophagy or ubiquitination inhibitor blocked these colocalizations.

View Article: PubMed Central - PubMed

Affiliation: Hematology Center of Cyrus Tang Medical Institute, Jiangsu Institute of Hematology, Jiangsu Key Laboratory for Stem Cell Research, Collaborative Innovation Center of Hematology, Affiliated Children's Hospital, Soochow University School of Medicine, Suzhou, China.

ABSTRACT
B-cell acute lymphoblastic leukemia (B-ALL) accounts for the most cancer incidences in children. We present here that autophagy is downregulated in pediatric B-ALL, suggesting a possible link between autophagy failure and pediatric B-ALL leukemogenesis. With a pediatric t(1;19) B-ALL xenograft mouse model, we show here that activation of autophagy by preventive administration of rapamycin improved the survival of leukemia animals by partial restoration of hematopoietic stem/progenitor cells, whereas treatment of the animals with rapamycin caused leukemia bone marrow cell-cycle arrest. Activation of autophagy in vitro or in vivo by rapamycin or starvation downregulated oncogenic fusion protein E2A/Pbx1. Furthermore, E2A/Pbx1 was found to be colocalized with autophagy marker LC3 in autolysosomes and with ubiquitin in response to autophagy stimuli, whereas autophagy or ubiquitination inhibitor blocked these colocalizations. Together, our data suggest a collaborative action between autophagy and ubiquitination in the degradation of E2A/Pbx1, thereby revealing a novel strategy for targeted preventive or treatment therapy on the pediatric ALL.

Show MeSH
Related in: MedlinePlus