PRF1 and neoplasm: A successful anti-tumor immune response requires a few key steps: (a) the capture of tumor antigens by MHC molecules, which are expressed on antigen-presenting cells (APCs), (b) the activation and expansion of CD4+ and/or CD8+ T cells, (c) the production of inflammatory cytokines (i.e., IFN-γ), and cytotoxin (i.e., granzymes B, perforin).