Heat shock protein 70 (Hsp70) membrane expression on head-and-neck cancer biopsy—a target for natural killer (NK) cells

Heat shock protein 70 (Hsp70) was detected on the cell membrane of human tumor cell lines, but not on normal cells. Here we studied Hsp70 membrane expression as a target for natural killer (NK) cells on tumor material and control tissues of head-and-neck cancer patients. Membrane-bound Hsp70 was determined by flow cytometry on single-cell suspensions of tumors and the corresponding normal tissues of head-and-neck cancer patients. The cytolytic activity of NK cells against Hsp70-positive tumor cells was measured in a standard cytotoxicity assay. In total, 54 of 74 primary tumors were found to be Hsp70 membrane-positive (73%); tongue/mouth, 21 of 24 (88%); oropharynx, 13 of 20 (65%); hypopharynx, 3 of 6 (50%); larynx, 8 of 11 (73%); trachea 1 of 2 (50%); esophagus, 4 of 5 (80%); lymph node metastases, 4 of 6 (67%). The corresponding control tissue was negative for membrane-bound Hsp70. Biopsies (6 of 6) of patients after in vivo γ-irradiation (fractionated 5 × 2 Gy) were strongly Hsp70 membrane-positive. Irradiated, Hsp70-positive tumor cells are targets for Hsp70-peptide stimulated NK cells. An irradiation-inducible, tumor-selective Hsp70 membrane localization provides a target structure for Hsp70-peptide stimulated human NK cells.