Human tumor testsystems: a new screening approach.

Recently, a new screening system which is mostly based on the use of human tumor material has been developed. This system uses various in vitro or in vivo test systems, such as the human tumor clonogenic assay, the subrenal capsule assay and the human tumor xenograft model to evaluate the potential clinical effectiveness of new drugs on human tumors. The predictive value of those test systems indicated by a reasonable correlation between test results and clinical activity has been shown in retrospective and even prospective clinical trials. To overcome the tumor heterogeneity and to circumvent the questionable preselection of drugs using fast proliferating tumors, this human tumor based test system uses a broad panel of slow proliferating human tumors which are established in nude mice to allow repeated tests. Recently some drugs being preferentially active in this human tumor based test system which are at the same time only marginally active in the usual NCI animal tumor screening system have been developed.