Knock‐down of SOX11 induces autotaxin‐dependent increase in proliferation in vitro and more aggressive tumors in vivo

The transcription factor SOX11 is a novel diagnostic marker for mantle cell lymphoma (MCL), distinguishing this aggressive tumor from potential simulators. Recent data also show that the level of SOX11 correlates to in vitro growth properties in MCL, as well as the clinical progression. We have previously shown that MCL‐associated pathways, such as Rb‐E2F, are dysregulated leading to decreased proliferation upon overexpression of SOX11, emphasizing the impact of SOX11 on MCL‐specific gene expression and growth control. However, it remains to be determined which growth regulatory pathways that are induced upon SOX11 knock‐down, leading to an increased cellular growth. Consequently, we established a model cell line with constitutive down‐regulation of SOX11. The highly proliferative features of this cell line were investigated by gene expression analysis, proliferation assay, cell cycle distribution and potential to induce tumors in NOD‐SCID mice. Our in vitro studies demonstrated a SOX11‐dependent regulation of MCL‐specific gene expression. In addition, we identified autotaxin (ATX) to be regulated by SOX11. Our results clearly showed a correlation between SOX11 level and cellular growth rate, which was dependent on ATX, as well as a direct relation between the level of SOX11 in tumorigenic cells and the growth rate of these tumors in NOD‐SCID mice.