Heat Shock Enhances the Susceptibility of Tumor Cells to Lysis by Lymphokine-Activated Killer Cells

Objective: To determine whether heat-treated thyroid cancer cells augment the susceptibility of target cells to lysis by autologous lymphokine-activated killer cells. Design: Peripheral blood lymphocytes from patients with thyroid cancer were incubated with recombinant interleukin 2 (100 U/mL) for 7 days, and thyroid cancer cells obtained from surgical specimens were heated at 44°C for 20 minutes and incubated at 37°C for 18 hours before performing the radioactive chromium Cr 51 release assay. Results: The susceptibility of heat-treated thyroid cancer cells to lysis by autologous and allogeneic lymphokine-activated killer cells was significantly greater than that of untreated tumor cells. The mechanism of enhanced susceptibility was unclear. However, the effect depended on de novo protein synthesis, because inhibition of RNA synthesis by dactinomycin completely abolished the heat-enhanced susceptibility of tumor cells. Conclusion: Immunotherapy combined with hyperthermia may be useful in management of thyroid cancer. (Arch Otolaryngol Head Neck Surg. 1995;121:1009-1014)