ESTIMATING THE PROBABILITY OF INITIATED CELL-DEATH BEFORE TUMOR-INDUCTION

The effects of cell toxicity are known to be inherent in carcinogenesi s induced by radiation or chemical carcinogens, The event of cell deat h precludes tumor induction from occurring, A long standing problem is to estimate the proportion of initiated cells that die before tumor i nduction, No experimental techniques are currently available for direc tly gauging the rate of cell death over extended periods of time, The obstacle can be surmounted by newly developed theoretical methods of c arcinogenesis modeling, In this paper, we apply such methods to publis hed data on multiple lung tumors in mice receiving different schedules of urethane, Bioassays of this type play an important role in testing environmental chemicals for carcinogenic activity, Our estimates for urethane-induced carcinogenesis show that, unexpectedly, many initiate d cells die early in the course of tumor promotion, We present numeric al estimates for the probability of initiated cell death for different schedules (and doses) of urethane administration.