B-cell CLL/lymphoma 9 protein is a protein that in humans is encoded by the BCL9 gene.
BCL9, together with its paralogue gene BCL9L (BCL9 like or BCL9.2), have been extensively studied for their role as transcriptional beta-catenin cofactors, fundamental for the transcription of Wnt target genes.
BCL9 and BCL9L have been shown to take part in other tissue-specific molecular mechanisms, showing that their role in the Wnt signaling cascade is only one aspect of their mode of action.
BCL9 is associated with B-cell acute lymphoblastic leukemia. It may be a target of translocation in B-cell malignancies with abnormalities of 1q21. The overexpression of BCL9 may be of pathogenic significance in B-cell malignancies.
BCL9 and BCL9L are potential clinical targets for human cancers; for instance, the gene expression changes that they promote is associated with a poor outcome in colorectal cancer.
Like BCL2, BCL3, BCL5, BCL6, BCL7A, and BCL10, it has clinical significance in lymphoma.