B2M and neoplasm: In addition, proteins involved in antigen processing, transport and presentation, such as beta 2 microglobulin (β2M), human leukocyte antigen (HLA) molecules, large multifunctional protease (LMP), and transporter-associated with antigen processing (TAP) are important for tumour antigen processing and presentation, and genetic modifications of these proteins can lead to ICI resistance (37).