The polypeptide Fortilin (also known as Translationally Controlled Tumor Protein, TCTP) specifically interacts with p53, a tumor suppressor involved in the induction of apoptosis and the normal growth regulation of a cell. Fortilin also specifically binds MCL1 (Myeloid Cell Leukemia 1). Fortilin has the ability to prevent apoptosis, which may be unregulated in hyperproliferative cells. The present invention is directed at compositions and methods involving a Fortilin modulator, which can induce apoptosis, for the prevention, treatment, or diagnosis of hyperproliferative diseases and conditions, including cancer and atherosclerosis. It is directed also at compositions and methods involving Fortilin, which can inhibit apoptosis, for the treatment of diseases and condition characterized by apoptosis, including certain vascular conditions.