F-box only protein 9 (FBXO9)

F-box only protein 9 (FBXO9) is a substrate recognition component of the SCF E3 ubiquitin-protein ligase complex and belongs to the F-box protein family, specifically the Fbxs subclass characterized by diverse protein-protein interaction domains. FBXO9 drives the ubiquitination and proteasomal degradation of select phosphorylated proteins, influencing processes such as cell cycle progression, protein translation, adipocyte differentiation (via PPARγ ubiquitination), survival of epithelial cells, maintenance of chromosome stability, and pluripotency regulation. In cancer, FBXO9 displays context-dependent roles: it can act as a tumor suppressor (e.g., inhibiting lung cancer migration and metastasis by suppressing Wnt signaling via V-ATPase regulation) or as an oncogene (multiple myeloma, hepatic carcinoma). Levels of FBXO9 expression have been linked to patient prognosis in certain cancers, and its function is under investigation for therapeutic targeting and biomarker applications. FBXO9 is also known by several aliases, including NY-REN-57, and is recognized as a renal carcinoma antigen and cross-immune reaction antigen. No approved drugs currently directly target FBXO9, though V-ATPase inhibitors may have therapeutic relevance in the context of FBXO9-related cancer biology.

Other names

FBXO9FBX9VCIA1NY-REN-57Cross-immune reaction antigen 1Renal carcinoma antigen NY-REN-57dJ341E18.2F-box protein Fbx9

Drugs inhibiting V-ATPase may suppress metastatic signaling in FBXO9-deficient tumors (by restoring vesicular acidification and blocking Wnt/β-catenin activation). Theoretical design of E3 ligase modulators could alter protein stability of key substrates (e.g., PPARγ, mTORC1 components).