Op18 belongs to the stathmin family of genes and encodes a ubiquitous cytosolic phosphoprotein that may function as an intracellular relay integrating several signaling pathways such as those involved in cell proliferation and differentiation.  Op18 has also been shown to be involved in the regulation of the microtubule filament system by destabilizing microtubules, thereby preventing assembly and promoting the disassembly of microtubules.  More recently, op18 has been implicated as a potential target of the ASK1-p38 MAP kinase cascade, suggesting that the ASK1-p38 cascade may regulate microtubule dynamics through op18.  Op18 is highly expressed in a wide variety of human malignancies, including leukemia, prostate cancer, ovarian carcinoma, and breast carcinoma, suggesting that op18 may be an ideal target for anti-cancer therapeutics.