Abstract
Purpose: The pleiotropic effects of heat on cancer cells have been well documented. The biological effects seen depend on the temperature applied, and the heating duration. In this study we investigate the cytotoxic effects of heat on colon cancer cells and determine how different cell death processes such as autophagy, apoptosis and necroptosis play a role in cell response. Materials and methods: The thermal dose concept was used to provide a parameter that will allow comparison of different thermal treatments. Two human colon cancer cell lines, HCT116 and HT29, were subjected to ablative temperatures using a polymerase chain reaction thermal cycler. Temperature was recorded using thermocouples. Cell viability was assessed using the MTT assay. Induction of apoptosis was estimated using an enzyme-linked immunosorbent assay that detects cleaved cytoplasmic nucleosomes. Protein regulation was determined using immunoblotting. The percentage of cells undergoing apoptosis and autophagy was determined with annexin V/propidium iodide staining and a cationic amphiphilic tracer using fluorescence-activated cell sorting analysis. Results: Exposure of colon cancer cells to ablative thermal doses results in decreased cell viability. The cytotoxic effect of heat is associated with induction of apoptosis and autophagy, the amount depending on both the thermal dose applied and on the time elapsed after treatment. Autophagy induction is mainly seen in live cells. RIPK3 protein levels are increased after exposure of cells to heat. A necroptosis inhibitor does not affect cell viability. Conclusions: Autophagy, apoptosis and necroptosis are associated with the response of these cancer cell lines to supra-normal temperatures.
Highlights
Cancer mortality accounts for more than 150,000 deaths a year in the UK [1], with the most reliable estimate for the worldwide death toll being more than 8 million deaths in 2012 alone [2]
The cytotoxic effect of heat is associated with induction of apoptosis and autophagy, the amount depending on both the thermal dose applied and on the time elapsed after treatment
The time/temperature combinations used in the study were each recorded 25 times in each of five different positions in the polymerase chain reaction (PCR) tubes to evaluate the accuracy of the thermal dose delivery of the thermal cycler (Table 1)
Summary
Cancer mortality accounts for more than 150,000 deaths a year in the UK [1], with the most reliable estimate for the worldwide death toll being more than 8 million deaths in 2012 alone [2]. Thermal treatments are often described in terms of thermal dose (TD) which has the units of equivalent minutes at 43 C (EM43). This concept attempts to provide a parameter that allows comparison of treatments delivered at different temperatures for varying lengths of time. Using knowledge of the temperature achieved as a function of time, and a mathematical description of this relationship for thermal damage, a treatment can be related to an exposure time at a chosen reference temperature. Since a typical temperature profile consists, at a minimum, of three phases: an initial heating period, a period of approximately constant temperature, and a cooling period, it is necessary to calculate the accumulated thermal dose using the expression in Equation 2: TD 1⁄4 EM43 1⁄4 t1⁄4Xfinal Rð43ÀTÞDt ð2Þ t1⁄40
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
