Protein Mis18-beta (OIP5)

**Protein Mis18-beta (OIP5)** is a centromere- and chromatin-associated protein that is essential for recruitment of centromere protein-A (CENP-A) through interaction with Holliday junction recognition protein and other mitotic regulators[1][5]. Encoded by the OIP5 gene (chromosome 15), it acts as a driver of cell cycle progression and chromatin organization, ensuring normal chromosome segregation during mitosis[1][5]. OIP5 is categorized as a cancer/testis antigen, with low or absent expression in most somatic tissues except testis, but is aberrantly overexpressed in a range of cancers—including glioblastoma, liver, breast, colorectal, bladder, and lung cancers—where its expression correlates with increased tumor proliferation, metastasis, and poor patient outcomes[1][2][3][4][6]. Experimental knockdown of OIP5 suppresses cancer cell proliferation, colony formation, and tumorigenicity, and induces cell cycle arrest and apoptosis in xenograft models[2][3]. Mechanistically, OIP5 is involved in a positive feedback loop with the E2F1 signaling pathway, further promoting aggressive tumor biology[2]. Its cancer/testis expression profile, role in cell cycle regulation, and impact on prognosis make OIP5 an attractive candidate for targeted cancer therapy and biomarker development[2][3][5]. Currently, no drugs directly target OIP5, but it is being actively studied for its potential as a therapeutic target and biomarker.

Other names

Protein Mis18-betaOIP5MIS18BCT86Cancer/testis antigen 86Opa-interacting protein 5hMIS18betaLINT-25LAP2alpha interactor-25MIS18 kinetochore protein homolog B

N/A (no approved drugs known to directly target OIP5; future mechanisms likely to involve inhibition of cell cycle progression or disruption of centromere assembly)