In neuroblastoma and small-cell lung cancer, the coordinated transcriptional silencing of components of the MHC class I antigen presentation pathway (including MHC class I heavy chains, TAP1/2, PSMB8/9, and NLRC5 transactivator) is associated with activity of the polycomb repressive complex 2 (PRC2) and bivalent H3K4me3 and H3K27me3 histone modifications. This evidence concerns the gene TAP1 and neuroblastoma.