Contributions
Abstract: EP405
Type: E-Poster Presentation
Session title: Acute myeloid leukemia - Biology & Translational Research
Background
Acute myeloid leukemia (AML) is a heterogeneous clonal disorder characterized by immature myeloid cell proliferation. Leukemic cells reside in highly specialized bone marrow (BM) niches composed of distinct cell populations, including mesenchymal stromal cells (MSCs). AML cells depend for survival on B-cell lymphoma 2 (BCL-2) family members, which regulate the intrinsic pathway of programmed cell death. Venetoclax (VEN) was the first BCL-2-selective agent to enter the clinic and it showed breaking through effect in combination with demethylating agents in older patients with treatment-naïve AML. Despite the encouraging clinical results of VEN, mechanisms of resistance were also described. Of note, the high rate of relapse may in part be explained by the inability of treatments to efficiently overcome the protection of the BM niche. Indeed, recent evidence demonstrated that BM-derived MSCs provide a protective microenvironment, which modulates drug sensitivity in several hematological disorders, including AML. However, the role of MSCs in modulating the response to VEN treatment has been poorly elucidated.
Aims
The aim of this study is to investigate the mechanisms of MSC-mediated VEN resistance in AML, to unravel new MSC–dependent mechanisms promoting leukaemia progression.
Methods
We isolated BM-derived mononuclear cells from healthy donors (HDs, undergoing stem cell transplant) and AML patients to generate HD/AML-MSCs. Next, we set up co-cultures with HD/AML-MSCs and the AML cell line (MV4-11) or primary AML cells. Before and after co-culture, we investigated the viability of AML cells treated with different doses of VEN.
Results
First, we studied the effects of single-agent therapy with VEN on the AML cell line, MV4-11. We evaluated cell apoptosis and we confirmed that VEN reduced significantly the viability of MV4-11 in a dose-dependent manner, with an enhanced effect at higher concentration. Next, we performed co-culture experiments between MV4-11 and HD-/AML-MSCs. We set up the co-cultures with and without trans-wells to unearth if the MSC-mediated protection is contact-dependent or is based on the release of soluble factors. We found that both HD- and AML-MSCs, significantly reduced the apoptosis of MV4-11 after VEN exposure, regardless VEN dose, supporting the fundamental role of MSCs in drug resistance. Interestingly, we clarified that the mechanisms involved in MSC-mediated protection were contact-dependent. Indeed, the addiction of trans-wells to the co-culture system almost abrogated the MSC-protective effect on VEN-induced apoptosis, suggesting a complex interplay between AML cells and adhesion molecules in our setting (a set of experiments to identify the signaling pathway involved is ongoing). Finally, we performed the co-culture experiments with primary AML cells, isolated at diagnosis. We found that AML cells, treated with VEN, showed different apoptotic rates, suggesting that AML cells have intrinsic factors making them more resistant or sensitive to the treatment. Furthermore, we found that both HD- and AML-MSCs protected AML cells from apoptosis induced by VEN, confirming the key role of MSCs in drug resistance.
Conclusion
For the first time, our data clarify that both primary HD- and AML-MSCs protect AML cells, including primary samples, from VEN-induced apoptosis, through contact-dependent mechanisms. Overall, our results indicate that the BM microenvironment, in particular MSCs, can promote leukemia progression, favoring drug resistance to VEN treatment.
Keyword(s): Bone marrow stroma, Drug resistance
Abstract: EP405
Type: E-Poster Presentation
Session title: Acute myeloid leukemia - Biology & Translational Research
Background
Acute myeloid leukemia (AML) is a heterogeneous clonal disorder characterized by immature myeloid cell proliferation. Leukemic cells reside in highly specialized bone marrow (BM) niches composed of distinct cell populations, including mesenchymal stromal cells (MSCs). AML cells depend for survival on B-cell lymphoma 2 (BCL-2) family members, which regulate the intrinsic pathway of programmed cell death. Venetoclax (VEN) was the first BCL-2-selective agent to enter the clinic and it showed breaking through effect in combination with demethylating agents in older patients with treatment-naïve AML. Despite the encouraging clinical results of VEN, mechanisms of resistance were also described. Of note, the high rate of relapse may in part be explained by the inability of treatments to efficiently overcome the protection of the BM niche. Indeed, recent evidence demonstrated that BM-derived MSCs provide a protective microenvironment, which modulates drug sensitivity in several hematological disorders, including AML. However, the role of MSCs in modulating the response to VEN treatment has been poorly elucidated.
Aims
The aim of this study is to investigate the mechanisms of MSC-mediated VEN resistance in AML, to unravel new MSC–dependent mechanisms promoting leukaemia progression.
Methods
We isolated BM-derived mononuclear cells from healthy donors (HDs, undergoing stem cell transplant) and AML patients to generate HD/AML-MSCs. Next, we set up co-cultures with HD/AML-MSCs and the AML cell line (MV4-11) or primary AML cells. Before and after co-culture, we investigated the viability of AML cells treated with different doses of VEN.
Results
First, we studied the effects of single-agent therapy with VEN on the AML cell line, MV4-11. We evaluated cell apoptosis and we confirmed that VEN reduced significantly the viability of MV4-11 in a dose-dependent manner, with an enhanced effect at higher concentration. Next, we performed co-culture experiments between MV4-11 and HD-/AML-MSCs. We set up the co-cultures with and without trans-wells to unearth if the MSC-mediated protection is contact-dependent or is based on the release of soluble factors. We found that both HD- and AML-MSCs, significantly reduced the apoptosis of MV4-11 after VEN exposure, regardless VEN dose, supporting the fundamental role of MSCs in drug resistance. Interestingly, we clarified that the mechanisms involved in MSC-mediated protection were contact-dependent. Indeed, the addiction of trans-wells to the co-culture system almost abrogated the MSC-protective effect on VEN-induced apoptosis, suggesting a complex interplay between AML cells and adhesion molecules in our setting (a set of experiments to identify the signaling pathway involved is ongoing). Finally, we performed the co-culture experiments with primary AML cells, isolated at diagnosis. We found that AML cells, treated with VEN, showed different apoptotic rates, suggesting that AML cells have intrinsic factors making them more resistant or sensitive to the treatment. Furthermore, we found that both HD- and AML-MSCs protected AML cells from apoptosis induced by VEN, confirming the key role of MSCs in drug resistance.
Conclusion
For the first time, our data clarify that both primary HD- and AML-MSCs protect AML cells, including primary samples, from VEN-induced apoptosis, through contact-dependent mechanisms. Overall, our results indicate that the BM microenvironment, in particular MSCs, can promote leukemia progression, favoring drug resistance to VEN treatment.
Keyword(s): Bone marrow stroma, Drug resistance