Abstract
Metaphase-arrest agents and hyperthermia are both known to be capable of inducing apoptosis, and they have been used, separately, in cancer treatments. Here, we have examined whether the two treatments together may have a synergistic effect. We find that when H-HeLa cells are arrested in metaphase with spindle poisons (nocodazole or paclitaxel) and then subjected to mild heat treatment (41.5℃), they exhibit morphological changes typical of apoptosis within three hours. Moreover, those changes are blocked by the pan-caspase inhibitor zVAD-fmk, indicating apoptosis, and activated Procaspase 3 is detected by immunoblotting and by staining with the fluoresce-in-labelled caspase inhibitor FAM-VAD-fmk. Interphase cells treated in the same way do not under-go apoptosis, even with spindle poisons present. Induction of apoptosis is more rapid when the cells have been arrested longer in metaphase, suggesting that accumulation or depletion of some cellular component(s) during metaphase-arrest may make them more susceptible to hyperthermia. Further work is in progress to test whether other cell lines exhibit the same behavior and to learn more about the mechanism. The phenomenon is of interest because it may provide clues to how hyperthermia induces cell death and may yield novel therapeutic approaches to block or stimulate apoptosis.
Highlights
Apoptosis is a process of programmed cell death by which unneeded or unwanted cells are eliminated from the body without inflammation
Using a HeLa strain called H-HeLa [20], we show that mild hyperthermia induces apoptosis in metaphase-arrested cells but not in interphase cells
In order to observe the effects of hyperthermia, metaphase-arrested cultures of H-HeLa cells were either left at 37.0 ̊C or treated at 41.5 ̊C for three hours, and samples from control and heat-treated cultures were viewed by epifluorescence microscopy following staining with Hoechst 33342 (Figure 1)
Summary
Apoptosis is a process of programmed cell death by which unneeded or unwanted cells are eliminated from the body without inflammation It plays an important role in embryological development, in the body’s defense against disease, and in surveillance for cells that may become cancerous. Apoptosis is involved in the mechanism of cell killing in cancer chemotherapy and radiotherapy [1] [7]-[11]. It plays a role in therapies using hyperthermia and spindle poisons. The function of the mitotic spindle is disrupted, leading to arrest of the cells in metaphase of mitosis. (Properly speaking, the cells are arrested in prometaphase, but for simplicity we follow common practice and refer to them as metaphase-arrested.) These reagents are used in cancer chemotherapy and are capable of inducing apoptosis (e.g., [17] [18])
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