A transgenic animal having a somatic cell in which at least one allele of an endogenous p53 and Pten gene is functionally disrupted is provided. The cell of the animal may be heterozygous or, more preferably, homozygous for the gene disruptions. The animals of the invention can be used to evaluate the efficacy of novel therapeutics and to identify novel points of therapeutic intervention for cancer. In certain embodiments, the transgenic animal is a transgenic mouse having functionally disrupted endogenous p53 and Pten genes. This mouse can be used to identify agents that inhibit the development of cancers, namely bladder cancers in humans in vivo. Nucleic acid constructs for functionally disrupting an endogenous p53 and Pten gene in a host cell, recombinant vectors including the nucleic acid construct, and host cells into which the nucleic acid construct has been introduced are also encompassed by the invention