PRF1 and neoplasm: Previous studies of Multhoff group [1,2,3] identified a membrane-bound Hsp70 on tumor cells as a tumor-specific recognition structure for a perforin-independent, granzyme B-mediated attack by allogeneic and autologous NK cells that have been pre-stimulated with Hsp70-derived 14-mer peptide (TKD) in combination with low dose IL-2 [9].