SOX11 Directly Represses Wnt/β-Catenin Signaling and Identifies a Subgroup of Mantle Cell Lymphoma Patients with Improved Survival with Intensive Treatment

Abstract 895 The SOX11 (Sex determining region Y)-box 11 transcription factor is aberrantly expressed in the majority (78-93%) of Mantle Cell Lymphoma (MCL) patients. Functionally, SOX11 represses MCL cell proliferation in vitro. We identify SOX11 mediated repression of Wnt signaling as contributory to the proliferation block in vitro and determine the clinical consequences of SOX11 overexpression in a meta-analysis of 3 large international patient cohorts. We have previously identified SOX11 direct binding target genes using chromatin immunoprecipitation coupled with high resolution, next generation sequencing (ChIP-Seq). Members of the Wnt signaling pathway, which is known to promote proliferation in MCL, were significantly enriched in our ChIP analysis in MCL patients and cell lines. Using a luciferase reporter assay for nuclear beta-catenin activity, we find that overexpression of SOX11 represses Wnt signaling (p The relationship between SOX11 and proliferation was validated in primary patient samples. Interrogation of an eighty-two patient gene-expression dataset demonstrates that SOX11 mRNA expression is significantly (p Prior studies examining the impact of SOX11 expression on patient outcomes using immunohistochemistry have been hampered by small numbers and heterogeneity in treatment. To overcome patient selection and treatment biases, we analyzed SOX11 expression in a total of 386 patients from three independent well-annotated tissue microarrays from University of Wisconsin, Karolinska Institute and British Columbia Cancer Agency. Higher SOX11 expression was associated with improved overall survival (p In conclusion, building from our previous ChIP-seq data, we further validated the inverse association between SOX11 and proliferation in primary patient samples. Our functional data showing direct repression of Wnt signaling represents one pathway through which SOX11 can exert its anti-proliferative effect. Our meta-analysis indicates that higher SOX11 expression is associated with improved survival in MCL patients treated with intensive chemotherapy. This supports prospective validation of SOX11 as a bioassay to select patients more likely to benefit from intensive therapy in MCL. Transcriptional regulation of Wnt and other biological pathways affected by SOX11 target genes help explain the impact of SOX11 expression on patient outcomes. Disclosures: Goy: Milennium: Membership on an entity9s Board of Directors or advisory committees, Speakers Bureau; Celgene: Membership on an entity9s Board of Directors or advisory committees; Seattle Genetics: Membership on an entity9s Board of Directors or advisory committees; Pharmacyclics: Membership on an entity9s Board of Directors or advisory committees; J & J: Membership on an entity9s Board of Directors or advisory committees; Pfizer: Membership on an entity9s Board of Directors or advisory committees.