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Hoechst 33342 induces radiosensitization in malignant glioma cells via increase in mitochondrial reactive oxygen
Mohammad Athar1, Nabo K Chaudhury, Mohammad E Hussain
1Division of Radiation Biosciences, Institute of Nuclear Medicine and Allied Sciences, Defence R&D Organization, Brig. S. K. Mazumdar Road, Delhi, India.
Abstract:
Mitochondrial DNA plays an important role in cellular sensitivity to cancer therapeutic agents. Hoechst 33342, a DNA minor groove binding ligand, has shown radiosensitizing effects in different cancer cell lines. In the present study, the possible binding of Hoechst 33342 with mitochondrial DNA, isolated from human cerebral glioma (BMG-1) cells, was investigated and consequences of this binding on excessive reactive oxygen species (ROS) generation in irradiated BMG-1 cells were studied. Alteration in the fluorescence spectroscopic characteristics of Hoechst 33342 suggested binding of Hoechst 33342 with isolated mitochondria and mitochondrial DNA. Persistent increase in level of ROS in the presence of Hoechst 33342 has been observed, which was further enhanced in irradiated cells. Investigations using inhibitors of ETC complex I suggested that mitochondrial bound Hoechst 33342 contributed to increased ROS, which was associated with alteration in DeltaPsim and antioxidant machinery. These factors appeared to contribute in potentiating radiation-induced cell death in BMG-1 cells. The finding from these studies will be useful in designing better anti-cancer strategies.
Insights
Hoechst 33342 binds to mitochondrial DNA, increasing reactive oxygen species (ROS) and enhancing radiation-induced cancer cell death. This finding aids in developing novel anti-cancer strategies.
Area of Science:
- Biochemistry
- Cell Biology
- Cancer Research
Background:
- Mitochondrial DNA (mtDNA) influences cancer therapeutic agent sensitivity.
- Hoechst 33342, a DNA minor groove binder, exhibits radiosensitizing properties in cancer cells.
Purpose of the Study:
- Investigate Hoechst 33342 binding to mtDNA in human cerebral glioma (BMG-1) cells.
- Determine the impact of this binding on reactive oxygen species (ROS) generation in irradiated BMG-1 cells.
Main Methods:
- Fluorescence spectroscopy to detect Hoechst 33342 binding to isolated mitochondria and mtDNA.
- Measurement of ROS levels in BMG-1 cells with and without Hoechst 33342, with and without irradiation.
- Utilized electron transport chain (ETC) complex I inhibitors to probe ROS generation mechanisms.
- Assessed changes in mitochondrial membrane potential (DeltaPsim) and antioxidant machinery.
Main Results:
- Fluorescence spectroscopy confirmed Hoechst 33342 binding to isolated mitochondria and mtDNA.
- Hoechst 33342 alone increased ROS levels, with further enhancement observed in irradiated cells.
- Mitochondrial-bound Hoechst 33342 was linked to increased ROS, altered DeltaPsim, and modified antioxidant systems.
- These alterations contributed to potentiated radiation-induced cell death in BMG-1 cells.
Conclusions:
- Hoechst 33342 binding to mtDNA in glioma cells increases ROS production.
- This interaction enhances radiosensitivity by affecting mitochondrial function and antioxidant defenses.
- Findings support the development of targeted anti-cancer strategies involving mitochondrial DNA interactions.
