Tumor border sharpness correlates with HLA-G expression in low-grade gliomas.

Human leukocyte antigen-G (HLA-G) is a tumor microenvironment molecule that is involved in the escape of cancerous tumors from host immune recognition and destruction. This study investigated the potential relationship between HLA-G expression levels and the sharpness of low-grade glioma tumor borders in magnetic resonance images. Preoperative T2-weighted images from 72 patients were retrospectively examined by manually segmenting the hyperintensive tumor areas and subsequently registering them to a standard brain template. Then, the intensity of the voxels inside the tumor border (tumor voxels) was compared with that of the voxels outside the tumor border (paratumor voxels). The radiologic sharpness of a tumor was defined as the mean ratio of the intensity of the tumor voxels to the intensity of the paratumor voxels. Tumors with high HLA-G expression were associated with larger tumors and lower mean hyperintensive contrast. These findings suggest that tumors with blurred boundaries may be those prone to diffuse invasion. Additionally, patients with tumors having high HLA-G expression were less likely to have undergone complete resections. Thus, this study is the first to identify an association between HLA-G expression and the radiologic morphology of the tumor border, and may further our understanding of the role of the HLA gene in immune escape in patients with low-grade gliomas.