ABSTRACT
The germinal center (GC) dark zone (DZ) and light zone (LZ) regions spatially separate expansion and diversification from selection of antigen-specific B-cells to ensure antibody affinity maturation and B cell memory. The DZ and LZ differ significantly in their immune composition despite the lack of a physical barrier, yet the determinants of this polarization are poorly understood. This study provides novel insights into signals controlling asymmetric T-cell distribution between DZ and LZ regions. We identify spatially-resolved DNA damage response and chromatin compaction molecular features that underlie DZ T-cell exclusion. The DZ spatial transcriptional signature linked to T-cell immune evasion clustered aggressive Diffuse Large B-cell Lymphomas (DLBCL) for differential T cell infiltration. We reveal the dependence of the DZ transcriptional core signature on the ATR kinase and dissect its role in restraining inflammatory responses contributing to establishing an immune-repulsive imprint in DLBCL. These insights may guide ATR-focused treatment strategies bolstering immunotherapy in tumors marked by DZ transcriptional and chromatin-associated features.
ABSTRACT
T-cell acute lymphoblastic leukemia (T-ALL) is a malignancy of thymic T-cell precursors. Overexpression of oncogenic transcription factor TAL1 is observed in 40-60% of human T-ALL cases, frequently together with activation of the NOTCH1 and PI3K-AKT pathways. In this study, we performed chemical screening to identify small molecules that can inhibit the enhancer activity driven by TAL1 using the GIMAP enhancer reporter system. Among approximately 3,000 compounds, PIK- 75, a known inhibitor of PI3K and CDK, was found to strongly inhibit the enhancer activity. Mechanistic analysis demonstrated that PIK-75 blocks transcriptional activity, which primarily affects TAL1 target genes as well as AKT activity. TAL1-positive, AKT-activated T-ALL cells were very sensitive to PIK-75, as evidenced by growth inhibition and apoptosis induction, while T-ALL cells that exhibited activation of the JAK-STAT pathway were insensitive to this drug. Together, our study demonstrates a strategy targeting two types of core machineries mediated by oncogenic transcription factors and signaling pathways in T-ALL.
