Histopathology of shock wave treated tumor cell suspensions and multicell tumor spheroids.

L1210 mouse leukemia cell suspensions exposed to 500 shock waves (SW) in an experimental lithotripter (XL1, Dornier) revealed severe cellular damage. Apart from cell fragments and cellular debris, cells exhibited alterations of shape, vacuolization of the cytoplasm, perinuclear cisternae, swelling of mitochondria or rupture of the mitochondrial fine structure, and permeabilization of the cell membrane. Treatment of multicell tumor spheroids of both HeLa and EMT6/Ro cells in suspension with 500 SW resulted either in loss of peripheral cells and serious cellular damage in the outer regions or in a fragmentation of the spheroids. Many of the geometrically intact cells exhibited the same histopathological alterations as the suspended L1210 cells. Immobilization of the spheroids in agar or gelatine, however, prevented spheroids from being agitated and accelerated during SW-exposure. After treatment with 500 SW, spheroids immobilized in gelatine were not different from control cultures, as investigated with light- and electronmicroscopy. From our results we conclude that spheroids in suspension are subject to cavitation and liquid jet formation, causing not only acceleration and shearing forces but also collisions which account for the observed cell damage.