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Cytotoxic Efficacy of Photodynamic Therapy in Osteosarcoma Cells In Vitro
Published on: March 18, 2014
[APOPTOSIS IN HUMAN OSTEOSARCOMA CELL LINE MG63 INDUCED BY PYROPHEOPHORBIDE-a METHYL ESTER-MEDIATED PHOTODYNAMIC
Yong Tao1, Qiu Huang1, Yunsheng Ou1
1Department of Orthopedics, the First Affiliated Hospital of Chongqing Medical University, Chongqing, 400016, P.R.China.
Objective:
To explore the effect of pyropheophorbide-a methyl ester-mediated photodynamic therapy (MPPa-PDT) on the apoptosis in human osteosarcoma cell line MG63 and the underlying mechanism.
Methods:
Human osteosarcoma MG63 cells in logarithmic growth phase were divided into 4 groups: blank control group (control group), the MPPa treatment group (MPPa group), the light irradiation group (LED group), and MPPa-PDT treatment group (MPPa-PDT group). MPPa-PDT group and MPPa group were incubated with MPPa (0.75?μmol/ L) for 20 hours in dark condition; control group and LED group were incubated with equal volume of fresh medium for 20 hours in the same condition. After washing with PBS and replacement with fresh culture medium, LED group and MPPa-PDT group cells were exposed to light (4.8 J/cm2) for 120 seconds. After light exposure, all groups were cultured in dark condition again. Then cellular morphology changes were observed by an inverted phase contrast microscopy, endoplasmic reticulum morphology changes were observed by transmission electron microscopy, cellular apoptosis was detected by Hoechst33258 nuclear staining, cell apoptotic rate and the levels of Ca in cells were analyzed by flow cytometry, the expression of p-PERK, C/EBP homologous protein (CHOP), cleaved-Caspase-12 were assayed by Western blot.
Results:
In MPPa-PDT group, the retracted and round cells were observed; Hoechst33258 nuclear staining showed nuclear condensation, fragmentation, and other typical apoptotic morphological changes; the cell apoptotic rate (48.76%±3.54%) was significantly higher than that of control group (5.04%±0.41%), MPPa group (5.33%±0.38%), and LED group (6.48%±0.46%) (P < 0.05); the levels of Ca2+ in cells (485.29±58.77) was also significantly higher than that of control group (97.24±4.77), MPPa group (97.95±6.30), and LED group (101.17±5.26) (P < 0.05); swelling endoplasmic reticulum was observed under transmission electron microscope; the expressions of p-PERK, CHOP, and cleaved-Caspase-12 gradually increased at 1, 3, and 6 hours after treatment respectively, which were significantly higher than those of the other groups (P < 0.05). There was no typical apoptotic morphological changes and endoplasmic reticulum morphological changes in control group, MPPa group, and LED group, and there was no significant difference in the above indexes among 3 groups (P > 0.05).
Conclusions:
MPPa-PDT can significantly induce apoptosis in MG63 cells. The endoplasmic reticulum stress pathway is involved in the MPPa-PDT induced apoptosis.
Insights
Pyropheophorbide-a methyl ester-mediated photodynamic therapy (MPPa-PDT) effectively induces apoptosis in human osteosarcoma cells. This process involves the endoplasmic reticulum stress pathway, highlighting a potential therapeutic mechanism.
Area of Science:
- Oncology
- Cell Biology
- Biochemistry
Context:
- Osteosarcoma is a primary malignant bone tumor with limited treatment options.
- Photodynamic therapy (PDT) offers a targeted approach to cancer treatment.
- Pyropheophorbide-a methyl ester (MPPa) is a photosensitizer used in PDT.
Purpose:
- To investigate the efficacy of MPPa-mediated photodynamic therapy (MPPa-PDT) in inducing apoptosis in the human osteosarcoma cell line MG63.
- To elucidate the underlying molecular mechanism of MPPa-PDT-induced apoptosis, specifically focusing on the endoplasmic reticulum stress pathway.
Summary:
- MPPa-PDT treatment of MG63 cells resulted in significant apoptosis, characterized by nuclear condensation and fragmentation.
- Increased intracellular calcium levels and endoplasmic reticulum swelling were observed post-MPPa-PDT.
- Western blot analysis revealed elevated expression of p-PERK, CHOP, and cleaved-Caspase-12, indicating activation of the endoplasmic reticulum stress response.
Impact:
- MPPa-PDT demonstrates significant potential as a therapeutic strategy for osteosarcoma by inducing cancer cell apoptosis.
- The findings elucidate the role of the endoplasmic reticulum stress pathway in MPPa-PDT-induced cell death, providing a mechanistic basis for its anti-cancer effects.
- This research may pave the way for developing novel, targeted therapies for osteosarcoma leveraging PDT and understanding its molecular underpinnings.
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