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Published on: November 28, 2015
Radiosensitization by inhibition of IkappaB-alpha phosphorylation in human glioma cells
Gui-Rong Ding1, Naoko Honda, Takehisa Nakahara
1Department of Radiological Technology, School of Health Sciences, Faculty of Medicine, Hirosaki University, 66-1 Hon-cho, Hirosaki, 036-8564, Japan.
Abstract:
To assess the role of nuclear factor kappaB (NFKB) in cellular radiosensitivity, three different IkappaB-alpha (also known as NFKBIA) expression plasmids, i.e., S-IkappaB (mutations at (32, 36)Ser), Y-IkappaB (a mutation at (42)Tyr), and SY-IkappaB, were constructed and introduced into human brain tumor M054 cells. The clones were named as M054-S8, M054-Y2 and M054-SY4, respectively. Compared to the parental cell line, M054-S8 and M054-Y2 cells were more sensitive to X rays while M054-SY4 cells exhibited the greatest sensitivity. After treatment with N-acetyl-Leu-Leu-norleucinal, a proteasome inhibitor, the X-ray sensitivity of M054-S8 and M054-SY4 cells did not change, while that of M054-Y2 cells and the parental cells was enhanced. An increase in X-ray sensitivity accompanied by a decrease in translocation of NFKB to the nucleus in parental cells was observed after treatment with pervanadate, an inhibitor of tyrosine phosphatase, as well as in M054-S8 and M054-SY4 cells. Repair of potentially lethal damage (PLD) was observed in the parental cells but not in the clones. Four hours after irradiation (8 Gy), the expression of TP53 and phospho-p53 ((15)Ser) was induced in the parental cells but not in M054-S8, M054-Y2 or M054-SY4 cells. Our data suggest that inhibition of IkappaB-alpha phosphorylation at serine or tyrosine acts independently in sensitizing cells to X rays. NFKB may play a role in determining radiosensitivity and PLD repair in malignant glioma cells; TP53 may also be involved.
Insights
Nuclear factor kappaB (NFKB) plays a role in cellular radiosensitivity and DNA repair in glioma cells. Inhibiting IkappaB-alpha phosphorylation enhances X-ray sensitivity and affects TP53 expression.
Area of Science:
- Molecular Biology
- Cancer Research
- Radiation Oncology
Background:
- Nuclear factor kappaB (NFKB) signaling is implicated in cellular responses to DNA damage.
- Understanding the mechanisms of radiosensitivity is crucial for optimizing cancer therapy.
Purpose of the Study:
- To investigate the role of IkappaB-alpha (NFKBIA) mutations in modulating cellular radiosensitivity in human brain tumor cells.
- To elucidate the involvement of NFKB signaling and TP53 in radioresistance and potentially lethal damage (PLD) repair.
Main Methods:
- Construction and introduction of IkappaB-alpha expression plasmids (S-IkappaB, Y-IkappaB, SY-IkappaB) into M054 glioma cells.
- Assessment of X-ray sensitivity, proteasome inhibitor effects, and NFKB nuclear translocation after pervanadate treatment.
- Analysis of potentially lethal damage (PLD) repair and TP53/phospho-p53 expression post-irradiation.
Main Results:
- M054 cells expressing mutated IkappaB-alpha (M054-S8, M054-Y2, M054-SY4) exhibited increased sensitivity to X-rays, with M054-SY4 showing the greatest sensitivity.
- Proteasome inhibitor treatment enhanced radiosensitivity in parental and M054-Y2 cells, but not M054-S8 or M054-SY4.
- Pervanadate treatment decreased NFKB nuclear translocation and increased radiosensitivity in parental, M054-S8, and M054-SY4 cells.
- Parental cells showed PLD repair, which was absent in the mutated clones. TP53 and phospho-p53 expression were induced in parental cells but not in clones after irradiation.
Conclusions:
- Inhibition of IkappaB-alpha phosphorylation at serine or tyrosine independently sensitizes cells to X-rays.
- NFKB signaling is a key determinant of radiosensitivity and PLD repair in malignant glioma.
- TP53 pathway activation is associated with radioresistance and may be involved in the observed cellular responses.