Effects of hyperthermia on natural killer cells: inhibition of lytic function and microtubule organization

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.

The effect of induced hyperthermia on the immune system

Therapeutical hyperthermia has been considered for cancer therapy since William Coley observed tumour remission after induction of fever by bacterial toxins at the end of the 19th century. Because fever is associated with a variety of immunological reactions, it has been suspected, that therapeutical hyperthermia might also activate the immune system in a reproducible manner and thereby positively influence the course of the disease. During the last decade, new insight has been gained regarding the immunological changes taking place during therapeutic hyperthermia. In this chapter, we review the most relevant data known about the effect of hyperthermia on the immune system with special focus on alterations induced by therapeutical whole-body hyperthermia (WBH) in cancer patients.

Hyperthermia suppresses the cytotoxicity of NK cells via down-regulation of perforin/granzyme B expression

Hyperthermia, which is used as an adjunctive therapy for cancer, is known to modulate the activity of natural killer (NK) cells in vitro, but its effect in vivo is unclear. In the present study, we used a whole body hyperthermia (WBH) device heated by infrared rays to evaluate the effect of WBH on mice models. We demonstrate here that wild type C57BL/6J mice exposed to 42 degrees C for 60min had reduced NK cell cytolytic activity against YAC-1 target cells as determined by cytolytic assay. This result was confirmed using Rag-2 knockout mice, which possess functional NK but not cytolytic T or NK-T cells. Moreover, WBH decreased the mRNA expression of perforin and granzyme B in spleens of mice. But the expression of TNF cytokines (Fas ligand and TRAIL) was unchanged. These data suggest that the suppression of NK cell activity induced by WBH could be mediated through the perforin/granzyme pathway.

Stress induced changes in lymphocyte subpopulations and associated cytokines during whole body hyperthermia of 41.8-42.2 degrees C

Extreme acute physical stress leads to transient impairment of T-lymphocytes, which are essential for tumor defence and prevention of infectious diseases. Radiant whole body hyperthermia (WBH) at 41.8-42.2 degrees C may enhance the efficacy of systemic chemotherapy in patients with advanced malignancies, but is associated with marked physical stress. Aim of this study was to demonstrate stress induced short-time effects on lymphocyte subpopulations and associated cytokines during WBH. Total leukocyte count, white blood cell differential blood count, lymphocyte subpopulations (T-helper-/T4-cells, T-suppressor-/T8-cells, natural-killer-/NK-cells, gammadelta-T-cells) as well as plasma levels of Interleukin(IL)-10, IL-12 and Interferon-gamma (IFN-gamma) were measured in ten patients treated with WBH and additional cytostatic chemotherapy. Blood samples were drawn before treatment, at three temperature points during WBH, and 24 h after start of treatment. Results were compared with those obtained from a control group consisting of six patients receiving chemotherapy alone. Numbers of T4-cells decreased significantly during WBH, while numbers of NK-cells and gammadelta-T-cells increased, resulting in transient impairments of total lymphocyte counts and T4/T8-ratio. IL-12 plasma levels as well as IFN-gamma/IL-10-ratio also decreased during WBH. No significant changes were found in T8-cells of WBH patients. Changes were reversible within 24 h and could not been found in control patients. Our results support the hypothesis that WBH combined with chemo therapy induces a strong but reversible anti-inflammatory stress response in cancer patients during therapy. Further studies are necessary to examine the pathophysiological details and to evaluate the meaning of these transient immunological changes for patient's outcome.

Heat shock reduces developmental competence and alters spindle configuration of bovine oocytes

Heat shock may enhance the thermotolerance of, or cause detrimental effects on, a variety of cell types or organisms, depending on the duration and intensity of the thermal challenge. Experiments were designed to investigate the effect of heat shock on the developmental competence and cytoskeletal structures of bovine oocytes following IVF. In Experiment 1, bovine cumulus-oocyte complexes (COCs) were subjected to standard IVM culture conditions for 20 h and were then randomly allocated to groups for heat shock at 42 degrees C for 0 (control), 1, 2, or 4h. The oocytes were fertilized after heat shock and followed by culture in KSOM for 8d. There were no significant differences in cleavage rates, but blastocyst formation (27% versus 44%) and total cell number per blastocyst (82+/-21 versus 108+/-36; mean+/-S.D.) were lower in the 4-h heat shock group compared to the control (P<0.05). Trophectoderm, but not ICM, cell numbers were decreased (P<0.05) in the 4-h heat shock group compared to the control. Alterations in the meiotic spindle of IVM oocytes (n=120-126) were examined after 1 to 4-h of heat shock in Experiments 2 and 3. The metaphase spindle became elongated or aberrant and smaller following heat shock, compared to the non-heat shock oocytes (P<0.05). The basis for changes in spindle configuration and the differential decrease in trophectoderm cell numbers after heat shock are not clear, but may lead to reduced embryonic development and perhaps the low pregnancy rate of domestic animals during hot seasons.

Nuclear and cytoskeletal alterations of in vitro matured porcine oocytes under hyperthermia

The effects of heat shock (HS) on the nucleus and cytoskeleton of in vitro matured pig oocytes were examined in this study. Porcine cumulus-oocyte complexes (COCs) were aspirated from 3 to 6 mm diameter follicles and subjected to standard in vitro maturation (IVM) procedures for 42 hr. In Experiment 1, IVM-derived oocytes were then randomly allocated to different HS treatments at 41.5 degrees C for 0 (control, C0h, n = 101), 1 (HS1h, n = 113), 2 (HS2h, n = 104), and 4 hr (HS4h, n = 111), respectively. An additional control group of oocytes was cultured for 4 hr without HS (C4h, n = 93). Immunocytochemical staining was performed using anti-tubulins and FITC-conjugated mouse IgG for microtubule (MT) labeling. The chromatin and microfilaments (MFs) were stained using Hoechst 33342 and rhodamine-phalloidin, respectively. In the severe HS (4 hr), the chromosomes of the MII oocytes became an aggregated chromatin structure and separated into groups. The spindle MTs were completely depolymerized or formed MT arrays. The relative fluorescence intensity (RFI) or amount of the MF structures including transzona processes (TZPs), vitelline ring (VR), and pericytoplasmic MF, were changed in various degrees. The reversibility of these alterations in the chromatin and the cytoskeleton depended on the duration of the HS. In general, abnormalities in the chromosomes, spindle MTs and the percentages of oocytes with pericytoplasmic MTs increased with length of HS treatment. The size of the spindle and the RFI of MFs in the HS oocytes were also altered. The significant changes in the nucleus and the cytoskeleton in porcine oocytes after HS may be associated with reduced development under hyperthermia and, perhaps, with the low pregnancy rates in domestic species during hot seasons.

Influences of Follicular Size on Parthenogenetic Activation and in Vitro Heat Shock on the Cytoskeleton in Cattle Oocytes

The availability of cow ovaries from the slaughterhouse has been very limited in Taiwan. To maximize the use of cow ovaries for research purposes, whole ovary dissection was performed and the developmental competence of the oocytes derived from different sizes of follicles was assessed by the rates of in vitro maturation (IVM) and parthenogenetic activation of the oocytes in Experiment 1 (Exp 1). Cumulus-oocyte complexes (COCs) derived from small (1-2 mm) and large (3-8 mm) follicles were subjected to standard IVM culture for 24 h. Mature oocytes were selected and then parthenogenetically activated using A23187 (5 microm, 5 min) or thimerosal (200 microm, 10 min) alone or combined with 6-dimethylaminopurine (2.5 mm and 3.5 h, respectively). Activation rates of the oocytes, neither from the large nor small follicles, were affected by different activation treatments (single or combined stimuli). Whereas maturation rates for the oocytes from large follicles were superior to those from small follicles in both the single (59% vs 45%) and combined treatments (76% vs 40%; p < 0.05). To understand how prolonged heat shock (HS) influences cytoskeletal configurations of mature bovine oocytes, in Experiment 2 (Exp 2), matured oocytes derived from large follicles were randomly allocated to different durations of HS treatments at 41.5 degrees C for 0 (C0h, control, n = 12), 1 (HS1h, n = 28), 2 (HS2h, n = 31), and 4 h (HS4h, n = 30). An additional control group was cultured for 4 h without HS (38.5 degrees C, 4 h, n = 35). Alterations in nuclear structures, microtubules (MTs), and microfilaments (MFs) of the oocytes were examined. Abnormalities in the chromosomes, spindle MTs and the percentages of oocytes with cytoplasmic MTs increased with time of HS treatment. The intensity of the MF distribution in the HS oocytes was also altered. Significant changes in the cytoskeleton after HS may be associated with the reduced development under hyperthermia and, perhaps, with the low pregnancy rates of the animals during hot seasons.

Whole body hyperthermia induces apoptosis in subpopulations of blood lymphocytes

Whole Body Hyperthermia (WBH) has been shown to induce alterations of lymphocyte subpopulations in peripheral blood: T-cells decrease and NK-cells increase in number in the course of this therapy. As elevated temperature induces programmed cell death in healthy lymphocytes in vitro, we intended to determine the role of lymphocyte apoptosis in WBH by measuring the rate of apoptosis in blood lymphocytes in the course of this treatment. Blood was taken from cancer patients, treated with whole body hyperthermia and chemotherapy, before, during and the day after treatment. Apoptosis rates of the whole lymphocyte population, as well as, of B-, T-, CD4 + -T-, CD8 + -T-, and Natural-Killer (NK)-cell-subpopulations were determined by staining with AnnexinV-FITC and FACS flow analysis. A significant rise of apoptosis in the whole lymphocyte population, in CD4 + -T- and in CD8 + -T-cells occurred during treatment. In contrast, an elevated rate of apoptosis in NK-cells was observed 20 hours after termination of WBH. These differences were similar when the cells were incubated at 37 degrees C for 24 hours. Our results suggest, that apoptosis is one reason for the previously described decrease of T-cells during WBH and of NK-cells after WBH, and that the hyperthermia-related apoptosis-inducing mechanism is different in T-cells and NK-cells.