DIFFERENTIAL THERMO-RESISTANCE OF MULTICELLULAR TUMOR SPHEROIDS

Abstract

Many cell lines, when cultured under proper conditions, can form three dimensionalstructures called multicellular spheroids. These spheroids resemble in vivo tumor models in severalaspects. Therefore, studying growth characteristics and behavior of spheroids is beneficial inunderstanding the behavior of tumors under various experimental conditions. In this work, we havestudied the growth properties, along with the thermal characteristics of spheroids of DU 145 humanprostate carcinoma cell lines and compared the results to monolayer cultures of these cells. For thispurpose, the DU 145 cells were cultured either as monolayer or spheroids. At various times afterinitiation of cultures, the growth properties of spheroids as a function of seeding cell number wasdetermined. To evaluate the thermal characteristics of spheroids, they were heated at various stages ofgrowth at 43 °C for various periods. The thermal response was judged by the survival fraction of colonyforming cells in spheroids or monolayer culture following heat treatment. The results showed spheroidswere more resistant to heat than monolayer cultures at all stages of development. However, the extent ofthis thermal resistant was dependent on the age, and consequently, the size of the spheroid. The resultsuggests that the differential thermal resistance of the spheroid cultures develop gradually during thegrowth of spheroid cultures of DU 145 cell line.