Purpose: 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.
Methods and materials: 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.
Results: 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 gamma-irradiation (fractionated 5 x 2 Gy) were strongly Hsp70 membrane-positive. Irradiated, Hsp70-positive tumor cells are targets for Hsp70-peptide stimulated NK cells.
Conclusion: An irradiation-inducible, tumor-selective Hsp70 membrane localization provides a target structure for Hsp70-peptide stimulated human NK cells.