Distinct Modulatory Effects of Fever-Range Hyperthermia on the Response of Breast Cancer Cells and Macrophages to Mistletoe (Viscum album L.) Extract

Abstract

Heat utility as a critical component of fever is often ignored, although the symptom is observed in many medical conditions. Mistletoe extract (ME) is an adjunctive medication prescribed to cancer patients. The increase in body temperature is frequently observed in patients following ME administration. Nevertheless, the impact of this fever on the effectiveness of therapy is unknown. Therefore, we aimed to investigate the effect of fever-range temperatures on ME-treated breast cancer cells and macrophages. The cells were simultaneously stimulated with ME and subjected to fever-range hyperthermia (FRH; 39 °C or 41 °C). After co-treatment, the cell viability, generation of reactive oxygen species (ROS), cell cycle distribution, and production of pro-inflammatory factors (interleukin (IL)-1β, IL-6, and cyclooxygenase (COX)-2) were evaluated. The results showed that the exposure of ME-treated breast cancer cells to FRH at 39 °C resulted in a slight decrease in their viability, whereas FRH of 41 °C enhanced this effect. Only FRH of 41 °C induced minor changes in ROS level in ME-treated breast cancer cell lines. In ME-treated macrophages, FRH stimulated cell proliferation. The cell cycle distribution analysis showed a difference between cells cultured at 39 °C and 41 °C in all examined cell lines. Moreover, hyperthermia at 41 °C completely inhibited the ME-induced increase in IL-1β and IL-6 expression in MCF-7 breast cancer cells, whereas this effect was not observed in 4T1 breast cancer cells. In contrast, in ME-treated macrophages, FRH of 41 °C strongly up-regulated expression of the pro-inflammatory factors. We conclude that fever is an important component of ME therapy that differentially affects cancer and immune cells.

Fever-Range Hyperthermia Promotes Macrophage Polarization towards Regulatory Phenotype M2b

“…We revealed that FRH alone induces an M2-like phenotype manifested by increased expression of CD163, IL-10, and Arg-1. However, we observed an increased level of pro-inflammatory TNF-α, which was in line with our previous experiments showing that FRH-treated macrophages can release pro-inflammatory cytokines such as IL-6 and IL-β [4]. Other authors have found that stimulation of RAW264.7 cells induces a heightened responsiveness to lipopolysaccharide in a model of inflammatory responses when compared to J774A.1 macrophages [28].…”

“…Despite reported benefits in the treatment of chronic diseases such as rheumatic diseases or cardiovascular disorders [3], the molecular changes induced by FRH remain poorly characterized. In our previous studies on mistletoe extract, we observed that macrophages are heat-sensitive cells that respond to heat with increased expression of pro-inflammatory cytokines such as interleukin (IL)-1β and IL-6 [4]. This observation is in accordance with other studies that demonstrated that elevated temperature can decrease the activation threshold required for the production of effector molecules in macrophages [5].…”

“…Additionally, FRH can support standard cancer treatments, including chemotherapy and radiation [21]. Although it is known that macrophages are sensitive to heat [4], relatively little attention has been given to the underlying molecular mechanism.…”

“…The effects of co-treatment with heat and LPS derived from Escherichia coli 0111:B4 (Sigma-Aldrich) on ROS generation in TLR-4 inhibited and non-inhibited RAW264.7 and J774A.1 cells were measured by H 2 DCF_DA (Sigma-Aldrich) staining, followed by flow cytometry analysis as described previously [4]. Cells were seeded in 6-well plates at the density of 1 × 10 6 cells per well.…”

Role of natural products in tumor therapy from basic research and clinical perspectives

“…Cellular and animal experiments have demonstrated that mistletoe induces apoptosis and inhibits metastasis by targeting the STAT3-FOXM1 pathway in BC [181]. Mistletoe exerts distinct effects on BC cells and macrophages, influencing cell viability, ROS generation, cell cycle arrest, and inflammation, all of which are modulated by changing in fever-range hyperthermia [182]. Although clinical trials have been conducted to investigate the potential of mistletoe in mitigating the side effects and enhancing anti-cancer effects, only a few numbers of animal studies have delved into the underlying molecular targets and mechanisms of its actions.…”