Variable Radiobiological Responses of Spheroids

Abstract

Several techniques are now available for the growth of mammalian cells in culture as 3-dimensional spheroids. Use of these spheroids as in vitro models of solid tumors is increasing, yet little characterization of most systems, other than histological appearance, has been forthcoming. Spheroids produced with different sublines of V79 Chinese hamster cells may exhibit vastly different radiobiological properties, despite having a similar histological appearance. Quantitative characterization of the radiation response of these spheroids indicates that the responses are highly dependent upon cell type, whether spherhoids are irradiated in stirred or unstirred cultures and the techniques used to recover cells from spheroids. The extent and/or degree of hypoxia within spheroids does not always correlate with spheroid radiosensitivity or development of central necrosis. The necessity of adequately characterizing such model systems were indicated and results obtained with 1 spheroid system apparently cannot be used as a baseline for another.