[en] The close relationship between signaling pathways regulating tumor growth and cardiac hypertrophy has attracted considerable interest. Although the involvement of proto-oncogenes in positively modulating myocardial hypertrophy has long been recognized, little is known about factors that counterregulate them. In this article, we review the novel tumor suppressor Ras-association domain family protein isoform 1A (RASSF1A), which strongly inhibits the prohypertrophic Ras-Raf1-ERK1/2 pathway in the heart. RASSF1A interacts with a number of important signaling molecules regulating cell growth, survival, and apoptosis; therefore, it serves as a key adaptor molecule that integrates the upstream stimuli and transduces them to the selective downstream effectors.