As a newly discovered tumor-associated gene, p42.3 was originally ascertained in gastric cancer cell line BGC823 and has been confirmed as a cell cycle-dependent gene that is overexpressed in many human tumor cell lines and embryonic tissues. p42.3 can regulate the level of relevant cycle-dependent proteins and promote malignant transformation of cells. A variety of cellular functions, including cell proliferation, cell invasion and cell migration, are under control of p42.3. Our review, namely the introduction of the structure of p42.3, underlying activity regulation mechanisms of p42.3 as well as the role p42.3 plays in malignant cellular transformation process, are accompanied by the presentation of potential directions of further researches of cancer prevention and therapy in which p42.3 is inevitable.