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Published on: December 4, 2018
[Function of alternative NF-κB activity in B-cell chronic lymphocytic leukemia cells]
Jingjing Xu1, Peng Zhou1, Feng Guo1
1Central Lab, The First Affiliated Hospital of Soochow University, Suzhou 215006, China.
Insights
Alternative nuclear factor-kappa B (NF-κB) pathway activation, specifically RelB combined with RelA, promotes survival in B-cell chronic lymphocytic leukemia (B-CLL). Bone marrow stromal cells protect B-CLL cells by inducing RelA and RelB expression.
Area of Science:
- Molecular biology
- Immunology
- Oncology
Context:
- B-cell chronic lymphocytic leukemia (B-CLL) is a heterogeneous malignancy.
- The role of the alternative NF-κB pathway in B-CLL pathogenesis is not fully understood.
- NF-κB signaling is crucial for lymphocyte development and function.
Purpose:
- To investigate the function and activation patterns of the alternative NF-κB pathway in B-CLL cells.
- To determine the impact of RelA and RelB activation on B-CLL cell survival.
- To explore the influence of bone marrow microenvironment on NF-κB activity and B-CLL cell fate.
Summary:
- Quantitative RT-PCR and ELISA assays revealed significantly higher mRNA expression of NF-κB subunits (RelA, p50, RelB, p52) in B-CLL cells compared to normal B cells.
- RelA activation was observed in most B-CLL patients, while RelB activity was induced in a subset, indicating heterogeneous pathway activation.
- In vitro studies showed that combined RelA and RelB activation conferred a survival advantage to B-CLL cells, which was further enhanced by co-culture with bone marrow stromal cells (hBMSCs).
Impact:
- Findings suggest that the alternative NF-κB pathway, particularly the interplay between RelA and RelB, is a key determinant of B-CLL cell survival.
- The bone marrow microenvironment, via hBMSCs, actively promotes B-CLL cell survival through NF-κB pathway modulation.
- This study provides insights into potential therapeutic targets within the NF-κB signaling network for B-CLL treatment.
Objective:
To investigate the function of alternative NF-κB activity in B-cell chronic lymphocytic leukemia cells (B-CLL).
Methods:
The mRNA expression of individual NF-κB subunits in CD5⁺CD19⁺ cells (CLL B-cells) from bone marrow (BM) of 56 patients with B-CLL was analyzed by quantitative RT-PCR. An ELISA-based NF-κB family transcription factor activity assay was performed to quantify the κB DNA-binding activity in nuclear extracts from CLL B-cells. Cell death of CLL-B cells was determined by PI staining, RelA and RelB expression at protein level of CLL B-cells by Western blot analyses.
Results:
The expression levels of RelA, p50, RelB and p52 mRNA in CLL B-cells were all higher than that of normal B cells with statistical significance (P<0.05). RelA was activated in almost all the patients detected while RelB activity was induced in part of samples. The average RelA activity in CLL B-cells was increased compared to that in normal B cells while the average RelB activity was similar to that of normal B cells. When cultured in vitro for 24, 48 and 72 hours, the frequencies of cell death of CLL B-cells from RelA⁺/RelB⁻ group were(35.54±4.43)%,(50.92±8.44)%, and(49.24±8.16)%, respectively; that of the RelA⁺/RelB⁺ group were (20.65±2.37)%, (18.17±1.36)%, and (26.55±4.08)%, respectively. When the cells from RelA+/RelB⁻ group were co-cultured with bone marrow stromal cells (hBMSCs), the frequencies of cell death of CLL B-cells were decreased compared to that of the cells cultured alone, while the frequencies of cell death of RelA⁺/RelB⁻ CLL B-cells were higher than that of CLL B-cells from RelA⁺/RelB⁺ group when co-cultured with hBMSCs. RelA and RelB expression in CLL-B cells from the RelA⁺/RelB⁻ group was induced after co-cultured with hBMSCs for 48 h. RelB was reduced in the cytoplasm and increased in the nucleus in CLL-B cells from the RelA+/RelB+ group.
Conclusion:
The alternative NF-κB was indeed activated and presented heterogeneous in CLL B-cells from BM. Activation of RelB combined with RelA activity could provide the survival advantage to CLL B-cells from BM. Co-culture with hBMSCs could protect CLL-B cells through the induction of RelA and Rel B expressions.
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