Expression of HLA-G in hemangioma and its clinical significance

This study examined the roles of HLA-G in the pathogenesis, development and immune tolerance of hemangioma. From 2000 to 2007, 52 paraffin-embedded specimens (26 from males and 26 from females) of skin capillary hemangioma and 7 samples of adjacent normal skin tissues were collected. Four fresh specimens of hemangioma were also harvested. All samples were HE-stained and proliferative cell nuclear antigen (PCNA) was immunohistochemically detected by using SP method. The samples were classified into proliferative group and degenerative group according to the Mulliken criteria and the expression pattern of PCNA. SP method and quantum dots double staining were applied to detect the expression of HLA-G and PCNA in hemangioma and normal tissue samples. The expression of HLA-G was detected by RT-PCR. The results showed that among the 52 samples of hemangioma, 29 were of proliferative type and 23 degenerative type, and of the four fresh samples of hemangioma, 2 were of proliferative type and 2 degenerative type. SP method results showed that HLA-G was expressed in both proliferative and degenerative hemangioma, but not in normal tissues. The quantum dots double staining exhibited that HLA-G expression was significantly higher in proliferative group than in degenerative (P < 0.05) and normal groups (P < 0.05), but there was no statistically significant difference between the latter two groups (P > 0.05). RT-PCR revealed that HLA-G was transcribed in both the proliferative and degenerative hemangioma tissues, but not in normal tissues. We are led to conclude that the elevated expression of HLA-G in proliferative hemangioma cells may lead to immune tolerance, which allows cells to escape immune surveillance and proliferate. On the other hand, the lower expression of HLA-G in degenerative hemangioma may result in immune cells-induced degeneration of hemangioma.