Colocalization of Inflammatory Response with B7-H1 Expression in Human Melanocytic Lesions Supports an Adaptive Resistance Mechanism of Immune Escape

Although many human cancers such as melanoma express tumor antigens recognized by T cells, host immune responses often fail to control tumor growth for as yet unexplained reasons. Here, we found a strong association between melanocyte expression of B7-H1 (PD-L1), an immune-inhibitory molecule, and the presence of tumor-infiltrating lymphocytes (TILs) in human melanocytic lesions: 98% of B7-H1(+) tumors were associated with TILs compared with only 28% of B7-H1(-) tumors. Indeed, B7-H1(+) melanocytes were almost always localized immediately adjacent to TILs. B7-H1/TIL colocalization was identified not only in melanomas but also in inflamed benign nevi, indicating that B7-H1 expression may represent a host…