Hyperthermia induces differentiation without apoptosis in permissive temperatures in human erythroleukaemia cells

Purpose: The aim of the present study was to investigate whether induction of differentiation by hyperthermia is accompanied by apoptosis and necrosis to further evaluate the benefits of using hyperthermia as a differentiation inducing physical modality. Materials and method: Differentiation was evaluated in K562 erythroleukaemia cells by measuring haemoglobin synthesis and flow cytometric measurement of glycophorin A expression. Apoptosis was measured by Annexin-V-FITC and Propidium Iodide (PI) double staining assay. Apoptosis and necrosis was also evaluated morphologically using staining with acridine orange/ethidium bromide (AO/EtBr) by fluorescence microscopy. Heat shock protein 70 (HSP70) level was measured by ELISA kit. Results: Hyperthermia (43°C) induced differentiation as judged by increased haemoglobin synthesis and glycophorin A expression. No sign of apoptosis or necrosis could be detected at this temperature. Cell viability did not change due to heat treatment, and cellular proliferation was reduced in a dose (heating time) dependent manner. At 45°C, hyperthermia induced apoptosis and necrosis with minimal or no sign of differentiation. HSP70 level was significantly increased at 43°C along with differentiation of leukaemic cells, while at 45°C no significant effect on HSP70 production could be observed. Conclusions: The encouraging results obtained here indicate that by heat treatment at 43°C, hyperthermia can be used alone or in combination with other modalities as a differentiation inducing agent without any detectable apoptotic activity. Positive correlation between HSP70 production and induction of differentiation and lack of apoptosis by hyperthermia confirm the possible role of HSP70 in the heat-induced differentiation and apoptosis in leukaemic cells

Acute and Long-Term Effects of Hyperthermia in B16-F10 Melanoma Cells

OBJECTIVE: Hyperthermia uses exogenous heat induction as a cancer therapy. This work addresses the acute and long-term effects of hyperthermia in the highly metastatic melanoma cell line B16-F10. MATERIALS AND METHODS: Melanoma cells were submitted to one heat treatment, 45°C for 30 min, and thereafter were kept at 37°C for an additional period of 14 days. Cultures maintained at 37°C were used as control. Cultures were assessed for the heat shock reaction. RESULTS: Immediately after the heat shock, cells began a process of fast degradation, and, in the first 24 h, cultures showed decreased viability, alterations in cell morphology and F-actin cytoskeleton organization, significant reduction in the number of adherent cells, most of them in a process of late apoptosis, and an altered gene expression profile. A follow-up of two weeks after heat exposure showed that viability and number of adherent cells remained very low, with a high percentage of early apoptotic cells. Still, heat-treated cultures maintained a low but relatively constant population of cells in S and G(2)/M phases for a long period after heat exposure, evidencing the presence of metabolically active cells. CONCLUSION: The melanoma cell line B16-F10 is susceptible to one hyperthermia treatment at 45°C, with significant induced acute and long-term effects. However, a low but apparently stable percentage of metabolically active cells survived long after heat exposure