Purpose: CD4(+)CD25(+)FoxP3(+) regulatory T-cells (Treg) are responsible for immunoevasion mechanisms induced by cancer. Specific chemokines such as CCL22 are presumed to mediate active Treg trafficking into the tumour site. In this context, the effects of irradiation and hyperthermia of tumour cells on Treg migration and the CCL22 concentration in the tumour cell supernatants after treatment were studied. Moreover, the relationship between CCL22 concentration and Treg cell migration was also examined.
Materials and methods: Treg and CD4(+)CD25(-) T-cells were isolated from human peripheral blood. Supernatants were obtained from primary cell cultures derived from head and neck carcinoma patients. Tumour cell cultures were treated with a dose of 2 Gy and hyperthermia (41.5 degrees C) or with hyperthermia or irradiation alone. Cancer cell culture supernatants were then used for a transmigration assay.
Results: Treg and CD4(+)CD25(-) T-cells showed an increased transmigration towards supernatants of hyperthermia-treated tumour cells. After combined application of hyperthermia and irradiation, Treg migration was similar to control levels, but CD4(+)CD25(-) migration was still enhanced. Irradiation caused a significantly decreased Treg influx, whereas the CD4(+)CD25(-) T-cell migration was not altered after the same treatment. Changes of Treg chemotaxis could be attributed to a treatment-associated escalation of the CCL22 in the tumour cell supernatants.
Conclusion: The combination of irradiation and hyperthermia is able to modify transmigration of tumour infiltrating lymphocytes beneficially and individually. In this in vitro system hyperthermia alone negatively impacts the immune response by selectively recruiting Treg, whereas hyperthermia with the addition of irradiation negates this effect.