Plasma Membrane- Derived Vesicles Shows Effects on the Induction of Differentiation of Promonocytes into Macrophages: A Possible Cancer Therapy

Background: Acute promyelocytic leukaemia (APL) represents 5-15% of all adult leukaemias. One of the approaches to treat APL is differentiation therapy which works by inducing differentiation of leukaemic promonocytes into mature non-replicative cell types that eventually undergo apoptosis. Plasma Membrane-derived Vesicles, (PMVs) are a heterogeneous group of small, membrane-coated vesicles with phospholipid rich particles, membrane receptors as well as other proteins inherent in their parental cells. There is evidence that PMVs are involved in differentiation in the hematopoietic environment in the bone marrow which suggests a possible involvement in leukaemia myeloid development, and possibly monocytic haematopoiesis. This work aimed to show principally whether PMVs can initiate differentiation/stop proliferation in HL-60 cells (promonocytes) and cause their differentiation into macrophages. This way, PMVs can be considered for differentiation therapy. Methods: PMVs were induced from cells using differential centrifugation. We also employed flow cytometry, ELISA, fluorescent microscopy analysis, SDS-PAGE, western blotting, growth inhibition & differentiation assays, nitroblue tetrazolium assay and cell cycle analysis to conduct our experiments. Results: HL-60 cells treated with PMVs showed a dose-dependent increase in adherence and increased expression of CD11b and CD14 as a sign of differentiation. Morphological changes were induced in HL-60 as well as phosphorylation of the TGF-?/Smad signaling pathway upon treatment with PMVs. Again, TGF-?1-bearing PMVs reduced the proliferation of HL-60 cells and caused them to exit the cell cycle at G0/G1. It was also shown that PMVs from HL60 or THP-1 cells but not from MCF-7 cells significantly reduce the growth rate of HL-60 cells and the reduction in proliferation was dependent on TGF-?1 delivered by the PMVs. Conclusion: This work showed that PMVs (isolated from HL-60 and THP-1 cells) carry TGF-β1 on their membrane surface. These TGF-β1-bearing PMVs can modulate the growth rate of HL-60 promonocytes without inducing apoptosis, the cells exiting the cell cycle at G0/G1. In addition, dramatic changes in the morphology of PMV-treated cells were observed as they became increasingly irregular in shape with membrane extensions resembling pseudopodia. It might therefore be prudent to look at PMV-releasing agents, as potential alternative drugs in differentiation therapy against APL. Background: Acute promyelocytic leukaemia (APL) represents 5-15% of all adult leukaemias. One of the approaches to treat APL is differentiation therapy which works by inducing differentiation of leukaemic promonocytes into mature non-replicative cell types that eventually undergo apoptosis. Plasma Membrane-derived Vesicles, (PMVs) are a heterogeneous group of small, membrane-coated vesicles with phospholipid rich particles, membrane receptors as well as other proteins inherent in their parental cells. There is evidence that PMVs are involved in differentiation in the hematopoietic environment in the bone marrow which suggests a possible involvement in leukaemia myeloid development, and possibly monocytic haematopoiesis. This work aimed to show principally whether PMVs can initiate differentiation/stop proliferation in HL-60 cells (promonocytes) and cause their differentiation into macrophages. This way, PMVs can be considered for differentiation therapy. Methods: PMVs were induced from cells using differential centrifugation. We also employed flow cytometry, ELISA, fluorescent microscopy analysis, SDS-PAGE, western blotting, growth inhibition & differentiation assays, nitroblue tetrazolium assay and cell cycle analysis to conduct our experiments. Results: HL-60 cells treated with PMVs showed a dose-dependent increase in adherence and increased expression of CD11b and CD14 as a sign of differentiation. Morphological changes were induced in HL-60 as well as phosphorylation of the TGF-?/Smad signaling pathway upon treatment with PMVs. Again, TGF-?1-bearing PMVs reduced the proliferation of HL-60 cells and caused them to exit the cell cycle at G0/G1. It was also shown that PMVs from HL60 or THP-1 cells but not from MCF-7 cells significantly reduce the growth rate of HL-60 cells and the reduction in proliferation was dependent on TGF-?1 delivered by the PMVs. Conclusion: This work showed that PMVs (isolated from HL-60 and THP-1 cells) carry TGF-β1 on their membrane surface. These TGF-β1-bearing PMVs can modulate the growth rate of HL-60 promonocytes without inducing apoptosis, the cells exiting the cell cycle at G0/G1. In addition, dramatic changes in the morphology of PMV-treated cells were observed as they became increasingly irregular in shape with membrane extensions resembling pseudopodia. It might therefore be prudent to look at PMV-releasing agents, as potential alternative drugs in differentiation therapy against APL. Background: Acute promyelocytic leukaemia (APL) represents 5-15% of all adult leukaemias. One of the approaches to treat APL is differentiation therapy which works by inducing differentiation of leukaemic promonocytes into mature non-replicative cell types that eventually undergo apoptosis. Plasma Membrane-derived Vesicles, (PMVs) are a heterogeneous group of small, membrane-coated vesicles with phospholipid rich particles, membrane receptors as well as other proteins inherent in their parental cells. There is evidence that PMVs are involved in differentiation in the hematopoietic environment in the bone marrow which suggests a possible involvement in leukaemia myeloid development, and possibly monocytic haematopoiesis. This work aimed to show principally whether PMVs can initiate differentiation/stop proliferation in HL-60 cells (promonocytes) and cause their differentiation into macrophages. This way, PMVs can be considered for differentiation therapy. Methods: PMVs were induced from cells using differential centrifugation. We also employed flow cytometry, ELISA, fluorescent microscopy analysis, SDS-PAGE, western blotting, growth inhibition & differentiation assays, nitroblue tetrazolium assay and cell cycle analysis to conduct our experiments. Results: HL-60 cells treated with PMVs showed a dose-dependent increase in adherence and increased expression of CD11b and CD14 as a sign of differentiation. Morphological changes were induced in HL-60 as well as phosphorylation of the TGF-?/Smad signaling pathway upon treatment with PMVs. Again, TGF-?1-bearing PMVs reduced the proliferation of HL-60 cells and caused them to exit the cell cycle at G0/G1. It was also shown that PMVs from HL60 or THP-1 cells but not from MCF-7 cells significantly reduce the growth rate of HL-60 cells and the reduction in proliferation was dependent on TGF-?1 delivered by the PMVs. Conclusion: This work showed that PMVs (isolated from HL-60 and THP-1 cells) carry TGF-β1 on their membrane surface. These TGF-β1-bearing PMVs can modulate the growth rate of HL-60 promonocytes without inducing apoptosis, the cells exiting the cell cycle at G0/G1. In addition, dramatic changes in the morphology of PMV-treated cells were observed as they became increasingly irregular in shape with membrane extensions resembling pseudopodia. It might therefore be prudent to look at PMV-releasing agents, as potential alternative drugs in differentiation therapy against APL.