MiRNA deregulation can contribute to breakdown of MHC I class antigen processing and presenting machinery in breast cancer cells

Background: To attack tumors, cytotoxic CD8+ T cells need to recognize tumor antigen peptides loaded onto major histocompatibility complex (MHC) class I molecules. Antigen processing and presentation is multistep process that includes proteasome-dependent and independent cleavage of cytosolic proteins, transport of derived peptides into the endoplasmic reticulum (ER) by transporters associated with antigen processing (TAPs), peptide trimming by ER aminopeptidases (ERAPs), peptide loading onto MHC molecules with the help of calnexin, calreticulin, protein disulfide-isomerase A3 and tapasin, movement of vesicles with MHC-peptide complex via the Golgi apparatus to the cell surface. Being one of the main immune escape pathways, defects in this machinery are frequently observed in various tumors and correlate with tumor grade and aggressiveness. This research aims to identify how the tumor-related abnormalities in microRNA (miRNA) expression pattern can disrupt antigen processing and presentation in breast cancer cells.