The Notch signaling pathway is involved in a wide group of processes during development of eukaryotic cells such as proliferation, migration, differentiation and apoptosis. Notch family is involved in tumorogenesis and stem cell self-renovation and is the key in determining cellular fate in diverse types of tumors. Our principal goal in this work was to evaluate if the pharmacological inhibition of the Notch pathway has a specific role in somatolactotropic tumor growth, hormone secretion, and protein expression. 700000 GH3 cells (somatolactotropic) were injected subcutaneously in the flank of Nude/Nude mice; after 21 days of growth the tumors were treated ip with DAPT, a gamma secretase inhibitor of the enzyme which activates the Notch pathway (8mg/kg of body weight). After three weeks of treatment the tumors were extracted. Tumor volumes in animals treated with DAPT were in average 42% smaller than in the control group (tumoral mass + SE: 490 + 80,7 and 284+ 67,5 mm2, control and DAPT, n=12 y n=11 respectively, p