Abstract: A mouse expressing myc in B cells, because of defective function of one or more tumor suppressor genes, is useful for the testing of anti-lymphoma agents and for the testing of genes which may have an effect on the apoptotic pathway. Preferred embodiments include mice of genotypes E&mgr;-myc/p53+/−, E&mgr;-myc/Rb+/− and E&mgr;-myc/p16+/−, and cells derived from lymphomas arising in these mice, wherein the cells may have undergone further genetic alteration. Mouse strains, lymphoma cells and cell lines of the invention can be used in methods to discover new anti-lymphoma agents, methods to characterize tumors, and to characterize genes which may affect the development of resistance to anti-tumor agents. Such methods are also part of the invention.