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MnTE-2-PyP Suppresses Prostate Cancer Cell Growth via H2O2 Production
Yuxiang Zhu1, Elizabeth A Kosmacek1, Arpita Chatterjee1
1Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198, USA.
Abstract:
Prostate cancer patients are often treated with radiotherapy. MnTE-2-PyP, a superoxide dismutase (SOD) mimic, is a known radioprotector of normal tissues. Our recent work demonstrated that MnTE-2-PyP also inhibits prostate cancer progression with radiotherapy; however, the mechanisms remain unclear. In this study, we identified that MnTE-2-PyP-induced intracellular H2O2 levels are critical in inhibiting the growth of PC3 and LNCaP cells, but the increased H2O2 levels affected the two cancer cells differently. In PC3 cells, many proteins were thiol oxidized with MnTE-2-PyP treatment, including Ser/Thr protein phosphatase 1 beta catalytic subunit (PP1CB). This resulted in reduced PP1CB activity; however, overall cell cycle progression was not altered, so this is not the main mechanism of PC3 cell growth inhibition. High H2O2 levels by MnTE-2-PyP treatment induced nuclear fragmentation, which could be synergistically enhanced with radiotherapy. In LNCaP cells, thiol oxidation by MnTE-2-PyP treatment was not observed previously and, similarly to PC3 cells, there was no effect of MnTE-2-PyP treatment on cell cycle progression. However, in LNCaP cells, MnTE-2-PyP caused an increase in low RNA population and sub-G1 population of cells, which indicates that MnTE-2-PyP treatment may cause cellular quiescence or direct cancer cell death. The protein oxidative modifications and mitotic catastrophes caused by MnTE-2-PyP may be the major contributors to cell growth inhibition in PC3 cells, while in LNCaP cells, tumor cell quiescence or cell death appears to be major factors in MnTE-2-PyP-induced growth inhibition.
Insights
The superoxide dismutase mimic MnTE-2-PyP inhibits prostate cancer progression by increasing hydrogen peroxide (H2O2) levels, causing different effects in PC3 and LNCaP cells. This leads to protein oxidation and nuclear fragmentation in PC3 cells, and quiescence or cell death in LNCaP cells.
Area of Science:
- Oncology
- Biochemistry
- Radiotherapy
Background:
- Prostate cancer is commonly treated with radiotherapy.
- MnTE-2-PyP, a superoxide dismutase (SOD) mimic, protects normal tissues from radiation.
- Previous studies showed MnTE-2-PyP inhibits prostate cancer progression alongside radiotherapy, but mechanisms were unclear.
Purpose of the Study:
- To elucidate the mechanisms by which MnTE-2-PyP inhibits prostate cancer cell growth, particularly in conjunction with radiotherapy.
- To investigate the differential effects of MnTE-2-PyP-induced hydrogen peroxide (H2O2) on PC3 and LNCaP prostate cancer cells.
Main Methods:
- Cell culture of PC3 and LNCaP prostate cancer lines.
- Measurement of intracellular H2O2 levels following MnTE-2-PyP treatment.
- Analysis of protein thiol oxidation and specific enzyme activity (PP1CB).
- Cell cycle analysis and assessment of nuclear fragmentation, RNA content, and sub-G1 population.
Main Results:
- MnTE-2-PyP treatment increased intracellular H2O2 in both PC3 and LNCaP cells, but with differential effects.
- In PC3 cells, MnTE-2-PyP induced protein thiol oxidation and nuclear fragmentation, potentially enhanced by radiotherapy.
- In LNCaP cells, MnTE-2-PyP treatment led to increased sub-G1 and low RNA populations, suggesting quiescence or cell death, without significant thiol oxidation.
Conclusions:
- MnTE-2-PyP's anti-cancer effects involve distinct mechanisms in different prostate cancer cell lines.
- In PC3 cells, oxidative modifications and mitotic catastrophe contribute to growth inhibition.
- In LNCaP cells, tumor cell quiescence or direct cell death are the primary mechanisms of MnTE-2-PyP-induced growth inhibition.
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