Aminoacyl tRNA synthase complex-interacting multifunctional protein 1, also known as Multisynthase complex auxiliary component p43, Endothelial monocyte-activating polypeptide II, AIMP1, EMAP2 and SCYE1, is a nucleus protein which contains one tRNA-binding domain. AIMP1 (also known as p43) is a factor associated with a macromolecular aminoacyl-tRNA synthetase (ARS) complex but also plays diverse regulatory roles in various physiological processes. AIMP1 negatively regulates TGF-beta signaling via stabilization of Smurf2. It suggests the novel activity of AIMP1 as a component of negative feedback loop of TGF-beta signaling. Recently, it been demonstrated that AIMP1 is also secreted and acts as a novel pleiotropic cytokine. AIMP1 protein induces the maturation and activation of DCs, which skew the immune response toward a Th1 response. AIMP1 is known as a cytokine working in the control of angiogenesis, inflammation, and wound healing. AIMP1 is secreted from the pancreas upon glucose starvation, and it also plays a glucagon-like role in glucose homeostasis. Although AIMP1 was identified as a component of the macromolecular aminoacyl tRNA synthetase complex involved in the cellular translation process, it was also found to be secreted as a cytokine having complex physiological functions. Among these, AIMP1's angiostatic and immune stimulating activities suggest its potential use as a novel antitumor therapeutic protein. AIMP1 may exert its antitumor activity by inducing tumor-suppressing cytokines. Thus, AIMP1 may be useful as a novel anti-tumor agent.