Scientists have shown that therapies which combine heat and radiation have a different effect on lab-grown mini tumours than they do on lab-grown cancer cells grown in a more traditional way in a two-dimensional layer.
In a new study, scientists at The Institute of Cancer Research, London, tested the effects of a combination of hyperthermia and radiation on mini tumours grown in what’s called a spheroid – where cells are packed in a 3D structure, much like a small ball.
Cells at the centre of the ball have less access to oxygen and nutrients compared to those on the outside, and this closely mimics tumours in the real world.
Making cells more vulnerable to treatments
Hyperthermia involves exposing cells to high temperatures, for example through high-intensity therapeutic ultrasound (HIFU) – a pioneering technology developed at the ICR.
Scientists are exploring the potential of combining hyperthermia and radiation because heating could make cells become more vulnerable to standard radiation treatments given for cancer.
It is thought that the application of heat increases the blood circulation to the cancer cells, thereby increasing the amount of oxygen available to them, which in turn could make the cells easier to kill with radiation.
ICR is a pioneer in use of mini-tumours
In a series of experiments, the researchers exposed mini tumours to 47 degrees C, radiation, and a combination of both. They repeated these treatments for standard cancer cells grown in dishes in the lab to allow them to compare the effects of the treatments between the two.
They found that cells in the mini tumours are more resistant to heat than standard lab-grown cancer cells. It was also found that in some cases, following heat treatment, cells in mini tumours were inclined to grow at a faster rate.
This may be because changes in the environment around the tumour made more oxygen available to the centre of the mini tumour, leading to increased growth.
Based on these results, the scientists believe more work is needed to calculate what the best ‘fractions’, or doses, of radiotherapy given to patients in combination with heat treatment could be. This work should be more closely based on data from experiments with mini tumours rather than that from layers of cells.
The ICR has pioneered the use of mini tumours, now in use in many labs, which more closely model the growth of a real tumour than two-dimensional cell cultures and also help limit the use of animals in research.
’We have been at the forefront of developing this treatment path’
Study co-leader Professor Gail ter Haar, Professor of Therapeutic Ultrasound at the ICR, said:
“The main aim of our study was to assess the response of tumour spheroids to hyperthermia, radiation, and a combination of the two treatments, and to see if the results were able to give us an accurate picture of how sensitive the cancer cells are to radiation after heat treatment.
“Heat-based treatments are effective at rapidly killing tissues when delivered via high intensity therapeutic ultrasound, and we have been at the forefront of developing this treatment path.
“In this study we were looking specifically at the ability of heat to make cells more susceptible to treatment with radiation, and it looks like further work is needed to improve this in the clinic.”
“Adding rapid heating of tumours to radiotherapy could make it more effective in some circumstances, through making cells more vulnerable to radiation treatment.
“This study focused on designing new tumour spheroids that could help us gain a much better insight into the effects of heating on cancer cells, and showed that our new models give a more accurate picture of how radiation and heating really affects tumours. Further experiments will give us a better understanding of exactly which combination of treatments might work.”