Hsp70 plasma membrane expression on primary tumor biopsy material and bonemarrow of leukemic patients

A tumor-selective cell surface localization of heat shock protein 70 (Hsp70 ), the major heat-inducible member of the Hsp70 group, correlates with an i ncreased sensitivity to lysis mediated by human natural killer (NK) cells a nd, therefore, might be of clinical relevance. With the exception of mammar y carcinomas, an Hsp70 plasma membrane expression was found on freshly isol ated human biopsy material of colorectal, lung, neuronal, and pancreas carc inomas, liver metastases, and leukemic blasts of patients with acute myelog enous leukemia. Since normal tissues and bone marrow of healthy human indiv iduals do not express Hsp70 on the cell surface, Hsp70 can be considered as a tumor-selective structure in vivo. Furthermore, we demonstrate that auto logous, Hsp70-positive leukemic blasts can be killed by NK cells stimulated with low doses of interleukin 2 plus recombinant Hsp70 protein.