Reduced expression of the transporter associated with antigen processing 1 molecule in malignant glioma cells, and its restoration by interferon-γ and -β

Object It remains unclear whether malignant glioma cells can deliver tumor antigens efficiently to major histocompatibility complex (MHC) Class I molecules. To elucidate the mechanism of antigen presentation in malignant gliomas, the authors examined the expression of the transporter associated with antigen processing 1 (TAP1), which transports antigens to MHC Class I molecules, and low-molecular-mass polypeptide 2 (LMP2), which is a subunit of a proteasome. They also analyzed the effects of interferon (IFN)-γ and IFN-β on the expression of these molecules. Methods Five glioma cells expressed undetectable or very low levels of TAP1 protein and did not express TAP1 messenger (m)RNA. Normal brain tissue and glioma tissue specimens also showed undetectable levels of TAP1 protein and the same levels of LMP2 protein as lymphoblastoid B cells. Treatments of the tumor cells with IFN-γ or -β enhanced the expression of both TAP1 protein and mRNA as well as the expression of MHC Class I molecules. The expression of...