The Effect of Combined Heat and Ultrasound on Multicellular Tumour Spheroids

Abstract

The effect of combined ultrasound and heat treatments on Chinese hamster multicellular spheroids of varying size was investigated using growth rate, single cell survival and ultrastructural damage as endpoints. Ultrasonic irradiation at 37 degrees C had no effect on the growth rate of 200-730 microns spheroids. Similarly there was no effect on the growth rate of 350 microns spheroids when irradiated during a 60 min exposure to 41.5 degrees C. However, spheroids of 200-700 mm diameter showed growth delay when held at 43 degrees C for 1 h. The effect was enhanced with concomitant ultrasound irradiation but was not dependent on spheroid size. When 200 and 400 microns spheroids held at 43 degrees C for 60 min were irradiated with different ultrasonic intensities a dose-dependent decrease in surviving fraction and a dose-dependent increase in growth delay was obtained. When surviving fraction was plotted as a function of growth delay a good correlation was obtained, suggesting that the combination of heat and ultrasound irradiation does not produce cytostasis in the surviving cells of either 200 or 400 microns spheroids. At the ultrastructural level increased cytoplasmic vacuolation was the only result of ultrasonic irradiation at 37 degrees C. Exposure to 43 degrees C for 60 min was required to elicit thermal damage. This took the form of membrane evagination at the spheroid surface, vacuolation of the cytoplasm, grouping of organelles around the periphery of the nucleus, and fragmentation of the nucleolus. These effects were enhanced with concomitant ultrasonic irradiation but other features were also noted, viz. disaggregation of polyribosomes, dilation of the rough endoplasmic reticulum and blebbing of the nuclear membrane. Damage was independent of spheroid size. These results are in agreement with previous data obtained from single-cell studies. Indicating that there is a non-thermal, non-cavitational component to the cell killing in multicellular spheroids resulting from combined heat and ultrasound treatment.

Focused Ultrasound-Mediated Hyperthermia in Vitro: An Experimental Arrangement for Treating Cells under Tissue-Mimicking Conditions

“…Since there is no fundamental lower FUS intensity limit, applications for FUS-mediated drug delivery or general low-intensity ultrasound studies would also be possible. This setup offers advantages over previous ones (ter Haar et al, 1988, Mylonopoulou et al, 2013); in particular, embedding cells in a biological matrix within a bulk tissue-mimicking phantom better reproduces in vivo exposure conditions. Here, cells embedded within a collagen scaffold received the biological cues necessary for cell adhesion and proliferation in a 3-D culture environment that stimulates cell–cell communication and provides a tissue-mimicking cellular microenvironment (Dubessy et al, 2000, Engelhardt et al, 2010, Hu et al, 2010, Riedl et al, 2017).…”

A lesson from earthquake engineering for selectively damaging cancer cell structures

“…Previous works in fact testify a weaker sensitivity of cell aggregates to US treatments. In particular, Ter Haar et al (1988) did not find significant changes in growth curves of 200−700 μm diameter spheroids after irradiation at 2.6 MHz and 37 • C, a delay being instead obtained when hyperthermia was combined with ultrasound exposure. No statistical significances in mammalian multicell tumor spheroids irradiated in the band 0.9−2.6 MHz were instead documented in Conger et al (1981).…”

IL-8 Release of HL-60 Cells Treated with Electric Currents of Different Wave Forms

“…In general, not only two chemical mediators can interact synergistically but also a chemical and a physical agent: for example, phorbol ester and magnetic fields (Tuinstra et al, 1998), concanavalin A and magnetic fields (Walleczek and Liburdy, 1990), or cis-diamminedichloroplatinum and heat (Urano et al, 1990). Even two physical stressors are able to produce synergistic effects in biological systems, for example heat and magnetic fields can induce heat shock proteins (Junkersdorf et al, 2000), heat and ultrasound enhance cell inactivation (ter Haar et al, 1988), as well as heat and UV light (Petin et al, 2002).…”