Oncogenic role of SOX9-DHCR24-cholesterol biosynthesis axis in IGH-BCL2 positive diffuse large B-cell lymphomas.

Overview

Although oncogenicity of the stem cell regulator SOX9 has been implicated in many solid tumors, its role in lymphomagenesis remains largely unknown. In this study, we showed that SOX9 is overexpressed preferentially in a subset of diffuse large B-cell lymphomas (DLBCL) harboring IGH-BCL2 translocations. SOX9 positivity in DLBCL correlates with advanced stage of disease. Silencing of SOX9 decreased cell proliferation, induced G1/S arrest and increased apoptosis of DLBCL cells, both in vitro and in vivo. Whole transcriptome analysis and CHIP-seq assays identified DHCR24, a terminal enzyme in cholesterol biosynthesis, as a direct target of SOX9, which promotes cholesterol synthesis by increasing DHCR24 expression. Enforced expression of DHCR24 was capable of rescuing the phenotypes associated with SOX9 knockdown in DLBCL cells. In DLBCL cell line xenograft models, SOX9 knockdown resulted in lower DHCR24 level, reduced cholesterol content and decreased tumor load. Pharmacological inhibition of cholesterol synthesis also inhibited DLBCL xenograft tumorigenesis, the reduction of which is more pronounced in DLBCL cell line with higher SOX9 expression, suggesting that it may be addicted to cholesterol. In summary, our study demonstrates that SOX9 can drive lymphomagenesis through DHCR24 and the cholesterol biosynthesis pathway. This SOX9-DHCR24-cholesterol biosynthesis axis may serve as a novel treatment target for DLBCL.