TAPBP and neoplasm: Defects in key APM elements like TAP, tapasin, and MHC class I are frequently observed across various human tumors, disrupting the tumor cells’ ability to present antigens and be recognized by tumor-specific cytotoxic T cells, thereby facilitating immune evasion.161,163 For example, hypermethylation of promoters or enhancers of genes such as TAP, tapasin, and MHC class I itself leads to their downregulation, impairing antigen presentation and facilitating tumor escape from cytotoxic T cell recognition.