Decreased expression of HLA class I on ocular melanoma cells following in vitro photodynamic therapy.

Our objective was to investigate whether photodynamic therapy (PDT) influences the expression of HLA Class I and beta 2-microglobulin molecules on cultured uveal melanoma cells. Uveal melanoma cells were incubated with hematoporphyrin esters (HPE) and illuminated using red light. HLA expression on cells was determined by flowcytometry. PDT treatment induced an immediate reduction in expression of HLA Class I and beta 2-microglobulin, followed by a transient increase in expression after 2 h. Normalization occurred after 6 h. Treatment of ocular melanoma cells with PDT temporally alters the expression of HLA Class I and beta 2-microglobulin, which may affect anti-tumor-immune responses.