Anti-tumor effects of hyperthermia plus granulocyte colony-stimulating factor

Old and new facts about hyperthermia-induced modulations of the immune system

Hyperthermia (HT) is a potent sensitiser for radiotherapy (RT) and chemotherapy (CT) and has been proven to modulate directly or indirectly cells of the innate and adaptive immune system. We will focus in this article on how anti-tumour immunity can be induced by HT. In contrast to some in vitro assays, in vivo examinations showed that natural killer cells and phagocytes like granulocytes are directly activated against the tumour by HT. Since heat also activates dendritic cells (DCs), HT should be combined with further death stimuli (RT, CT or immune therapy) to allocate tumour antigen, derived from, for example, necrotic tumour cells, for uptake by DCs. We will outline that induction of immunogenic tumour cells and direct tumour cell killing by HT in combination with other therapies contributes to immune activation against the tumour. Studies will be presented showing that non-beneficial effects of HT on immune cells are mostly timely restricted. A special focus is set on immune activation mediated by extracellular present heat shock proteins (HSPs) carrying tumour antigens and further danger signals released by dying tumour cells. Local HT treatment in addition to further stress stimuli exerts abscopal effects and might be considered as in situ tumour vaccination. An increased natural killer (NK) cell activity, lymphocyte infiltration and HSP-mediated induction of immunogenic tumour cells have been observed in patients. Treatments with the addition of HT therefore can be considered as a personalised cancer treatment approach by specifically activating the immune system against the individual unique tumour.

Granulocyte-colony stimulating factor enhances anti-tumour effect of hyperthermia

The combined effect of granulocyte-colony stimulating factor (GCSF) and hyperthermia in the treatment of experimental tumours was studied to examine the possible involvement of activated granulocytes in the antitumour effect of hyperthermia. Two weeks after transplantation of SCC VII cells (1 x 10(5)) into the instep of the left leg of C3H/HeJ male mice, the mice were given subcutaneous injections of GCSF (0.2 mg/kg) for 4 days. On day 4, hyperthermia was applied locally at 43 degrees C for 40 min. Hyperthermia inhibited the tumour growth, and this effect was enhanced by pre-treating the animals with GCSF. The numbers of circulating neutrophils in control and GCSF-treated mice were 2728 +/- 517/microl and 3124 +/- 194/microl, respectively (p = 0.53). Hyperthermia increased the number of neutrophils to 4409 +/- 700/microl (p < 0.05). Hyperthermia combined with GCSF significantly increased the number of netrophils to 5479 +/- 691/microl (p < 0.01). Chemiluminescence analysis using L-012 revealed that GCSF enhanced the generation of reactive oxygen species by about 10-fold. Glutathione contents in tumours 24 h after hyperthermia decreased by about 50% in both the hyperthermia groups with or without GCSF, as compared to those in the control. The GCSF-enhanced anti-tumour activity of hyperthermia was markedly inhibited by administration of a long-acting superoxide dismutase derivative (SM-SOD). These results suggest that GCSF activates the ability to generate active oxygen species by neutrophils and, thereby, enhances the anti-tumour effect of hyperthermia.

Effects of hyperthermia and granulocyte-macrophage colony-stimulating factor on the differentiation of human leukemic cell line U937

We have studied the effects of granulocyte-macrophage colony-stimulating factor (GM-CSF) and hyperthermia individually and in combination on the cell growth and differentiation of human monoblastic leukemia cell line U937. Several criteria were used to evaluate the differentiation of these cells, including the reduction in the plating efficiency and cell growth, the ability to phagocytize latex particles, the reduction of nitro blue tetrazolium (NBT), and development of surface antigenic markers. Hyperthermia alone was able to inhibit cell proliferation, reduce cell viability, and induce differentiation. In the range of 41-43 degrees C, the major effect of hyperthermia was cell differentiation induction as judged by above criteria. On average, hyperthermia induced differentiation in 32% of cells. GM-CSF was able to induce differentiation in 37% of U937 cells as judged by similar criteria. The combined treatment with GM-CSF and hyperthermia resulted in the differentiation of 60% of U937 cells. The extent of differentiation obtained is comparable or better than other combinatorial treatments using various cytokines or cytokines and chemical reagents reported before.