Hyperthermia increases natural killer cell cytotoxicity against SW-872 liposarcoma cell line.

BACKGROUND

Although there is convincing data in support of the effectiveness of hyperthermia in tumor therapy, the molecular mechanisms underlying the clinical effects of hyperthermia are still poorly understood.

OBJECTIVE

To investigate natural killer (NK) cell cytotoxicity against heat-treated SW-872 and HeLa tumor cell lines.

METHODS

NKG2D ligands and HLA class I transcription were examined using quantitative real-time PCR in treated tumor cell lines at 0, 2, 4, 6 and 12 h following thermal treatment at 39C and 42C for 1 h. The expression of MICA/B, ULBP1 and ULBP2 were also determined by flow cytometry. NK92-MI cytotoxic activity against heat-treated target cell lines was assessed by LDH release as well as annexin-V and 7-AAD assays.

RESULTS

Our results showed that heat treatment at 39C improved the cytolytic activity of NK cells against SW-872 cells without increasing NKG2D ligand concentration or decreasing HLA class I levels.

CONCLUSIONS

The observed increase in the cytotoxicity of NK cells against SW-872 cells after hyperthermia does not coincide with changes in MICA/B, ULBP1 and ULBP2 ligands of NKG2, however, the expression of other ligands in target cells may have made the cells susceptible to the cytotoxic effect of NK cells.