Changes on cancer and normal cells viability and ability to proliferate in response to hyperthermia

Abstract

Hyperthermic treatment alone or in combination with chemotherapy or radiotherapy is widely used for cancer therapy. However, treatment efficiency varies in different types of cancer cells and more detailed knowledge on response of different cells to hyperthermia is needed. Tests used for cell viability usually are based on estimation of certain cellular function (metabolism based on one substance, plasma membrane permeability, etc.). It is often not clear, whether these viability tests reveal survival of the cells or loss of some metabolic functions recover with the time passed without an impact on survival of treated cells. The aim of our work was to determine changes on cancer and normal cells viability and ability to proliferate in response to hyperthermia using different methods and to estimate correlation of results obtained by various viability tests with actual cell survival. Hyperthermia (HT) (42 ºC) was applied on cancer (WEHI-164, L929, MH22a, B16-F12, PANC1, BXPC3) and normal (BHK-21, CHO, McCoy) cell lines for 30 min. Immediately after the HT treatment, viability of cells was estimated by calcein-AM or propidium iodide methods. For cell survival colony formation assay was used. Diversity in response among the analysed cell lines to hyperthermia estimated by viability tests was observed. Cell staining with calcein-AM showed that 42 ºC HT inactivated esterases by 40% in 2 (out of 3) normal and 3 (out of 6) cancer cell lines. Meanwhile, plasma membrane permeability evaluation by cell staining with propidium iodide indicated negligible viability changes (up to 15%) nearly in all cell lines. Furthermore, the assay of colony formation revealed that MH22a cells had only 30% survival ratio, although these cells appeared resistant to HT when evaluated by calcein-AM and propidium iodide methods. [...]