The initiation/promotion standard protocol 28 (protocol 28), developed and used previously as an experimental model to verify the cancerogenic process of initiation/promotion in mouse skin, was revised in three aspects: (a) statistically it was shown sufficient to use, per promoter dose group, 16 colony-outbred female NMRI mice: (b) by weekly individual records of tumor response (and health status) of each mouse in a dose group, cumulative tumor incidences (and mean and extreme body weights) are determined; from these data the collective records (tumor response, health status), the only data accessible from protocol 28, may be generated in addition; (c) the details of dose groups and all data on tumor response and health status are processed by computer using the program package PAPILLOM. The latter was developed specifically for this purpose, is written in the programming language APL and designed for easy handling by staff of animal laboratories. The program package calculates, from the individual records per promoter dose group, cumulative tumor incidences (and survival data) with confidence limits for any one exposure time, and the package may be linked to programs for statistical validations. In addition, from the collective records it calculates the tumor rates, tumor yields and survival rates for any one exposure time. These data, obtained by either of the standard protocols (16 or 28), are fully comparable. For pure compounds they may be used to calculate semiquantitative tumor-promoting potencies. These values for more than 80 polyfunctional diterpenes of the tigliane, ingenane and daphnane type, scattered in or calculated from previous papers, together with their irritancies, were compiled. Within recent years, computer-assisted standard protocol 16 has been used to handle and evaluate about 1000 promoter dose groups. Protocol 16 allows one to extract and utilize more and better toxicological information on tumor response and health status from any one dose group, utilizing significantly fewer experimental animals than required by protocol 28. Thus, the computer-assisted standard protocol 16 optimizes the utility of the experimental model of mouse skin for the amount, quality and management of experimental data as well as for the requirements of animal protection.
