The present invention is related to a composition capable of inhibiting the growth of tumoral cells of different histological origins and of activated endothelial cells. The components of said compositions are polypeptide fragments of the serralisins, corresponding to the C-terminal fragment, from the internal metionine trough the end of the molecule, which could be combined among them and optionally with the prodigiosins that potentiate the antitumoral effect of the composition. The prodigiosins in the composition could be at a concentration of 0.1-100 nM. The anti-proliferative action of this composition is mediated by apoptotic mechanism. It's “in vivo” administration has antitumoral, antiangiogenic and protective effect against malignant tumors.