Transgenic mouse models for tumour‐suppressor genes

. Tumour‐suppressor genes are negative regulators of cell division and growth. Over the past decade, multiple, distinct tumour‐suppressor genes have been identified and cloned. In recent years, the ability to specifically manipulate the mouse genome via over‐expression, underexpression or deletion of genes using transgenic expression systems and embryonic stem cell (ES) technology has led to the identification and definition of the precise function of several tumour suppressor genes in vivo . Included in this group are mice with mutations in the p53 and retinoblastoma (Rb) genes. p53 Mutant mice are highly susceptible to tumour development and will serve as excellent models to understand the aetiology and pathology of several human cancers. In contrast to the role of the Rb gene in human retinoblastomas, mice heterozygous for a mutant Rb allele do not develop retinoblastoma, but develop pituitary tumours instead. Similar ES cell technology has been used to generate α‐inhibin deficient mice. Inhibin‐deficient mice develop gonadal and adrenal tumours with nearly 100% penetrance. These studies have identified inhibin as a novel secreted tumour suppressor. In the future, many of the unidentified functions of tumour‐suppressor genes can be tested using this powerful in vivo assay system.