APRIL (A PRoliferation-Inducing Ligand) is a member of the tumor necrosis factor family. APRIL shows high levels of expression in tumors of different origin and low level of expression in normal cells. APRIL shares two TNF receptor family members, TACI and BCMA with another TNF homolog, BlyS/BAFF both of which have been reported to play a role in autoimmune disease and cancer. The gene encoding the APRIL protein is localized to chromosome 17g 13.3. APRIL appears to play a role in T-independent type II antigen responses and T cell survival, but can also induce proliferation/survival of non-lymphoid cells. Local production of APRIL was found in arthritic joints of patients with inflammatory arthritis. Biologically active BlyS/BAFF and APRIL heterotrimers are expressed in patients with systemic immune-based rheumatic diseases. A soluble form of the high affinity BCMA receptor has been shown to inhibit the proliferative activity of APRIL in vitro, thus decreasing tumor cell proliferation, while APRIL-transfected cells show an increased rate of tumor growth very directly, suggesting that APRIL is implicated in the regulation of tumor cell growth.