HLA-G expression in basal cell carcinomas of the skin recurring after radiotherapy

Basal cell carcinoma (BCC) of the skin represents the most common malignancy in the fair-skinned population worldwide. HLA-G is one of the molecules implicated in immunotolerance. To investigate the role of HLA-G in recurring BCCs, we constructed a tissue microarray containing 38 primary BCCs that underwent radiotherapy and 14 secondary BCCs recurring on the primary site after radiotherapy, and evaluated the HLA-G protein expression by immunohistochemistry. The HLA-G protein was most frequently expressed in aggressive sclerosing BCCs. Nodular BCC demonstrated the strongest HLA-G expression. Interestingly, tumor infiltrating mononuclear cells (TIMC) expressed the HLA-G molecule in BCCs that showed no recurrence. After comparing primary BCCs and BCCs relapsed after radiotherapy, we observed decreased HLA-G expression on tumor cells and the loss of HLA-G expression on TIMC in relapsed BCCs. After radiotherapy, immunobiology of BCC may change resulting in the down-regulation of HLA-G expression on tumor and on tumor-infiltrating cells.