Effects of the combined action of hyperthermia and UV light on yeast cells: time factor and sequence of exposure

In modern methods of cancer therapy, combinations of influencing factors having various nature are widely used to achieve the highest therapeutic effect: ionizing radiation, chemotherapy drugs, hyperthermia, non-ionizing radiation, etc. The greatest cells damaging effect is achieved when the treatments are applied simultaneously. An increase in the interval between the treatments leads to final effect decrease. However, how the degree of the effect depends on the time gap has not been studied in detail. The paper presents the results of a study of this dependence with a different sequence of applied treatments. Combination of UV radiation and hyperthermia were examined. The choice of treatments is due to attention to the Vavilov-Cherenkov radiation, which arises when accompanies high-energy ionizing radiation used in oncotherapy and most of which is a continuous UV spectrum. And if we consider the Vavilov-Cherenkov radiation responsible for UV-like damages, which has its effect on the final result of the action of high-energy ionizing radiation, then it becomes clear that it is necessary to understand the behavior of UV light when it is used in combination with other damaging factors. Thus, the aim of the work is to study the effect of a sequence of applied treatments and the time gap between them on the magnitude of the final effect of the sequential action of UV light and hyperthermia on yeast cells. The dependence obtained in the work is of a multidirectional nature, changing from synergism to additivity, turning into antagonism with time gap rising. It is shown that the effect practically does not depend on the sequence of the treatments application, but significantly depends on the time gap between them. Such patterns were obtained for the first time. But it is indicates that when using in practice the combined action of ionizing radiation or UV light with hyperthermia, it should be remembered that the final effect can differ from expected.