The AP-1 -BATF and -BATF3 module is essential for growth, survival and TH17/ILC3 skewing of anaplastic large cell lymphoma

Transcription factor AP-1 is constitutively activated and IRF4 drives growth and survival in ALK+ and ALK– Anaplastic Large Cell Lymphoma (ALCL). Here we demonstrate high-level expression of BATF and BATF3 in ALCL, irrespective of the ALK-status. Both BATFs bind classical AP-1 motifs and interact with in ALCL deregulated AP-1 factors. Together with IRF4, they co-occupy AP-1-IRF composite elements (AICE), differentiating ALCL from non-ALCL. Gene-specific inactivation of BATFs by CRISPR/Cas9 or siRNAs, or global AP-1 inhibition by the dominant-negative A-Fos results in ALCL growth retardation and/or cell death in vitro and in vivo. Furthermore, the AP-1-BATF module establishes TH17 / innate lymphoid cell type 3 (ILC3)-associated gene expression in ALCL, including marker genes such as AHR, IL17F, IL22, IL26, IL23R, IL18R1 and RORγt. Elevated IL-17A and IL-17F levels were detected in pretreatment sera of a subset of children and adolescents with ALK+ ALCL. Finally, pharmacological inhibition of RORC as single treatment leads to cell death in ALCL cell lines, and, in combination with the ALK inhibitor crizotinib, enforces death induction in ALK+ ALCL. Our data highlight the crucial role of AP-1 / BATFs for ALCL biology and lead to the concept that ALCL might originate from ILC3 cells. This GEO dataset consists of 10 measured cell lines, including 6 ALCL cell lines (4 ALK+, 2 ALK-) and 4 control samples.