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UNRAVELING THE MOLECULAR PATHOGENESIS OF INEFFECTIVE ERYTHROPOIESIS IN CONGENITAL DYSERYTHROPOIETIC ANEMIA TYPE II: IN VITRO EVALUATION OF RAP-011 TREATMENT
Author(s): ,
Gianluca De Rosa
Affiliations:
Molecular Medicine and Medical Biotechnology,CEINGE - Biotecnologie Avanzate,Naples,Italy
,
Immacolata Andolfo
Affiliations:
Molecular Medicine and Medical Biotechnology,CEINGE - Biotecnologie Avanzate,Naples,Italy
,
Francesco Manna
Affiliations:
Molecular Medicine and Medical Biotechnology,CEINGE - Biotecnologie Avanzate,Naples,Italy
,
Antonella Gambale
Affiliations:
Molecular Medicine and Medical Biotechnology,CEINGE - Biotecnologie Avanzate,Naples,Italy
,
Roberta Marra
Affiliations:
Molecular Medicine and Medical Biotechnology,CEINGE - Biotecnologie Avanzate,Naples,Italy
,
Barbara Eleni Rosato
Affiliations:
Molecular Medicine and Medical Biotechnology,CEINGE - Biotecnologie Avanzate,Naples,Italy
,
Achille Iolascon
Affiliations:
Molecular Medicine and Medical Biotechnology,CEINGE - Biotecnologie Avanzate,Naples,Italy
Roberta Russo
Affiliations:
Molecular Medicine and Medical Biotechnology,CEINGE - Biotecnologie Avanzate,Naples,Italy
(Abstract release date: 05/18/17) EHA Library. De Rosa G. 06/25/17; 182098; S811
Gianluca De Rosa
Gianluca De Rosa
Contributions
Abstract

Abstract: S811

Type: Oral Presentation

Presentation during EHA22: On Sunday, June 25, 2017 from 08:30 - 08:45

Location: Room N109

Background
Congenital Dyserythropoietic Anemias (CDAs) are subtypes of bone marrow failure syndromes, hallmarked by ineffective erythropoiesis. The most common form is CDAtype II (CDAII), showing moderate/severe anemia, relative reticulocytopenia, jaundice, and iron overload. It is inherited as autosomal recessive disorderdue to loss-of-function mutations inSEC23B gene. More than 300 CDAII cases and 80 causative mutationshave been described so far. Despite this high allelic heterogeneity, two variants, R14W and E109K, represent more than 50% of the mutational events. To date, treatments for CDAII patients consist of supportive therapy, such as erythrocyte transfusions, or bone marrow transplantation or splenectomy in transfusion-dependentcases.Recently, members of TGF-β superfamily have been studied as potential regulators of erythropoiesis,especially the growth differentiation factor 11 (GDF11). Through the binding of specific receptors, GDF11 leads to an inhibited late-stage erythropoiesis. Indeed, two GDF11 inhibitors, ACE-011 and ACE-536,have been associated to an improvement of hematologic parameters. Studies with the mouse counterpart of ACE-011, RAP-011, on mouse model of β-thalassemia showed increased differentiation of erythroid cells, improvement of anemic condition and reduced iron overload in treated mice.

Aims
The main aim of our study is to assess the effects of RAP-011 on different cellular models of CDAII.

Methods
We measured circulating GDF11 levels in CDAII patients and healthy controls(HC) bywestern blot(WB). To assess the effectiveness of RAP-011(provided by Celgene Corporation)in vitro, we established two different cellular models of CDAII: (i) K562 cells stably silencedfor SEC23B by Sh-RNA carried in GIPZ lentiviral vectors; (ii) K562 stably overexpressing SEC23B-WT and the two variants, R14W and E109K. In vitro treatment has been performed at 0, 3, and 6 days of erythroid differentiation by hemin + GDF11 in presence or absence of RAP-011 in K562 cells stably silencedfor SEC23B.

Results

WB and subsequent densitometric analysis showed an increase of GDF11 levels in serum samples from 18 CDAII patients compared to 18 HC (p=0.02). Stable silencing of SEC23B in K562 cellsled to the establishment of two different clones, Sh-70 and Sh-74, showing amarkedreduction of SEC23Bexpression compared to Sh-CTR (85-90% and 60-65%, respectively). At 3 and 6 days of K562 erythroid differentiation by hemin, we observed an increased expression of pSMAD2 in GDF11-treated cells compared to non-treated ones; interestingly, a reduction of pSMAD2 in RAP-011+GDF11-treated cells was observed.

Conclusion

We firstly demonstrated the increased levels of GDF11 in CDAII patients. Thus, we used a combined treatment with hemin+GDF11 in SEC23B-silenced K562 stable clones, in order to reproducethe pathologic phenotype of the disease, andto make K562 cells suitable for RAP-011 treatment, as attested by the increased expression of pSMAD2 in GDF11-treated cells. The reduced pSMAD2 in RAP-011+GDF11-treated cells suggests that RAP-011treatment leads to repression of ActRIIA/B pathway, which in turn should increase nuclear levels of GATA1 transcription factor. This action should lead to an increased expression of GATA1-activated genes involved in erythroid development. The evaluation of GATA1 activation is ongoing, as well as the in vitro treatment of K562 stably overexpressing SEC23B-WT,SEC23B-R14W and -E109K.

Session topic: 31. Other Non-malignant hematopoietic disorders

Keyword(s): Treatment, Bone Marrow Failure, Anemia

Abstract: S811

Type: Oral Presentation

Presentation during EHA22: On Sunday, June 25, 2017 from 08:30 - 08:45

Location: Room N109

Background
Congenital Dyserythropoietic Anemias (CDAs) are subtypes of bone marrow failure syndromes, hallmarked by ineffective erythropoiesis. The most common form is CDAtype II (CDAII), showing moderate/severe anemia, relative reticulocytopenia, jaundice, and iron overload. It is inherited as autosomal recessive disorderdue to loss-of-function mutations inSEC23B gene. More than 300 CDAII cases and 80 causative mutationshave been described so far. Despite this high allelic heterogeneity, two variants, R14W and E109K, represent more than 50% of the mutational events. To date, treatments for CDAII patients consist of supportive therapy, such as erythrocyte transfusions, or bone marrow transplantation or splenectomy in transfusion-dependentcases.Recently, members of TGF-β superfamily have been studied as potential regulators of erythropoiesis,especially the growth differentiation factor 11 (GDF11). Through the binding of specific receptors, GDF11 leads to an inhibited late-stage erythropoiesis. Indeed, two GDF11 inhibitors, ACE-011 and ACE-536,have been associated to an improvement of hematologic parameters. Studies with the mouse counterpart of ACE-011, RAP-011, on mouse model of β-thalassemia showed increased differentiation of erythroid cells, improvement of anemic condition and reduced iron overload in treated mice.

Aims
The main aim of our study is to assess the effects of RAP-011 on different cellular models of CDAII.

Methods
We measured circulating GDF11 levels in CDAII patients and healthy controls(HC) bywestern blot(WB). To assess the effectiveness of RAP-011(provided by Celgene Corporation)in vitro, we established two different cellular models of CDAII: (i) K562 cells stably silencedfor SEC23B by Sh-RNA carried in GIPZ lentiviral vectors; (ii) K562 stably overexpressing SEC23B-WT and the two variants, R14W and E109K. In vitro treatment has been performed at 0, 3, and 6 days of erythroid differentiation by hemin + GDF11 in presence or absence of RAP-011 in K562 cells stably silencedfor SEC23B.

Results

WB and subsequent densitometric analysis showed an increase of GDF11 levels in serum samples from 18 CDAII patients compared to 18 HC (p=0.02). Stable silencing of SEC23B in K562 cellsled to the establishment of two different clones, Sh-70 and Sh-74, showing amarkedreduction of SEC23Bexpression compared to Sh-CTR (85-90% and 60-65%, respectively). At 3 and 6 days of K562 erythroid differentiation by hemin, we observed an increased expression of pSMAD2 in GDF11-treated cells compared to non-treated ones; interestingly, a reduction of pSMAD2 in RAP-011+GDF11-treated cells was observed.

Conclusion

We firstly demonstrated the increased levels of GDF11 in CDAII patients. Thus, we used a combined treatment with hemin+GDF11 in SEC23B-silenced K562 stable clones, in order to reproducethe pathologic phenotype of the disease, andto make K562 cells suitable for RAP-011 treatment, as attested by the increased expression of pSMAD2 in GDF11-treated cells. The reduced pSMAD2 in RAP-011+GDF11-treated cells suggests that RAP-011treatment leads to repression of ActRIIA/B pathway, which in turn should increase nuclear levels of GATA1 transcription factor. This action should lead to an increased expression of GATA1-activated genes involved in erythroid development. The evaluation of GATA1 activation is ongoing, as well as the in vitro treatment of K562 stably overexpressing SEC23B-WT,SEC23B-R14W and -E109K.

Session topic: 31. Other Non-malignant hematopoietic disorders

Keyword(s): Treatment, Bone Marrow Failure, Anemia

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