Expression of HLA-G in malignant mesothelioma and clinically aggressive breast carcinoma

The aim of the present study was to evaluate HLA-G expression in breast carcinoma and malignant mesothelioma (MM). Malignant breast carcinoma effusions (46) and corresponding solid tumors (39) and 104 MM (26 effusions, 78 solid tumors) were analyzed using immunohistochemistry (IHC). HLA-G protein and mRNA expression were further studied using immunoblotting (IB) and RT-PCR. HLA-ABC expression was analyzed using flow cytometry (FCM). IHC showed predominantly focal HLA-G expression in 12 of 46 (26%) breast carcinoma effusions and 16 of 39 (41%) solid lesions. In MM, 20 of 78 (26%) solid lesions and 14 of 26 (54%) effusions were focally HLA-G positive. Expression in MM was higher in effusions (p=0.008). IB showed more frequent HLA-G expression in MM compared with breast carcinoma effusions, while RT-PCR showed HLA-G mRNA expression in both tumors. FCM showed conserved HLA-ABC expression in 15 of 15 effusions. Breast cancer patients with HLA-G-positive tumor cells had shorter disease-free survival (mean 37 vs 85, median 25 vs 31 months), though not significantly (p=0.14). In conclusion, HLA-G is focally expressed in MM and breast carcinoma, while HLA-ABC expression is conserved. However, the up-regulated expression of HLA-G in MM effusions and its possible association with shorter disease-free survival in advanced stage of breast carcinoma suggest a possible role in immune response evasion in some tumors.