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Changes in antigen expression on human FME melanoma cells after exposure to photoactivated hematoporphyrin derivative
Abstract:
Exponentially growing melanoma cells of the line FME were incubated with hematoporphyrin derivative (HpD) for 1 and 18 h and subsequently exposed to light in the presence of HpD. Quantitative changes in the expression of the melanoma-associated surface antigen p250 recognized by the monoclonal antibody 9.2.27 were studied by flow cytometry. Treatment with HpD and light resulted in no immediate changes in the antigen expression. However, a few hours after light exposure a significant reduction in antigen expression was observed. For cells incubated with HpD for 1 h, the minimum expression of the antigen was observed 6 h after the irradiation, and the duration of the reduced expression was almost dose independent. On the other hand, the duration of the reduced antigen expression increased strongly with light dose for cells incubated with HpD for 18 h. In both cases antigen expression decreased exponentially with the product of drug concentration and light dose, indicating that there is no rapid mechanism by which the cells can repair the damage which leads to reduced antigen expression. Days were needed before the cells expressed a normal level of the antigen. A slight overshoot of the level of antigen expression above that for untreated cells was observed 2-5 days after light exposure depending on the incubation conditions with HpD and the light dose. At a given cell survival level (greater than 0.1), the decrease in antigen expression was more pronounced on cells incubated with HpD for 1 h than on cells incubated with the drug for 18 h.
Insights
Hematoporphyrin derivative (HpD) photodynamic therapy reduces melanoma-associated antigen p250 expression. This reduction is dose-dependent and persists for days, indicating limited cellular repair mechanisms.
Area of Science:
- Biochemistry
- Cell Biology
- Photomedicine
Background:
- Melanoma-associated surface antigen p250 plays a role in melanoma progression.
- Hematoporphyrin derivative (HpD) is a photosensitizer used in photodynamic therapy.
- Understanding antigen expression changes post-photodynamic therapy is crucial for melanoma treatment.
Purpose of the Study:
- To investigate the quantitative changes in melanoma-associated surface antigen p250 expression after HpD-based photodynamic therapy.
- To determine the kinetics and dose-dependency of antigen expression reduction.
- To assess the cellular repair mechanisms affecting antigen expression.
Main Methods:
- Melanoma cells (FME line) were incubated with HpD for 1 or 18 hours.
- Cells were subsequently exposed to light in the presence of HpD.
- Antigen p250 expression was quantified using flow cytometry and monoclonal antibody 9.2.27.
Main Results:
- Photodynamic therapy caused a significant reduction in antigen p250 expression hours after light exposure.
- The duration of reduced expression was dose-independent for 1-hour incubation but increased with light dose for 18-hour incubation.
- Antigen expression decreased exponentially with the combined drug and light dose, suggesting slow repair.
- A transient overshoot in antigen expression was observed days post-treatment.
Conclusions:
- HpD photodynamic therapy effectively reduces melanoma-associated antigen p250 expression.
- The observed antigen reduction is a dose-dependent process with limited rapid cellular repair.
- These findings have implications for understanding melanoma cell response to photodynamic therapy and potential immunomodulatory effects.