Figure 6.

RNA sequencing supports upregulation of JAK2 signaling in pcAECyTCL. (A) Heat map showing 1,603 differentially expressed genes (1,076 upregulated, 527 downregulated, false discovery rate [FDR] <0.01) in pcAECyTCL when compared to skin-resident CD8+ T cells. (B) Gene set enrichment analysis (GSEA) uncovered upregulation of the JAK-STAT pathway, the cell cycle (E2F targets, G2/M checkpoint, mitotic spindle), the NF-κB pathway and high inflammatory response in pcAECyTCL. NES: normalized enrichment score; FDR q-value: false discovery rate q-value. (See the Online Supplementary Table S18 for a complete list of GSEA signatures) (C) Examination of differentially expressed genes involved in the JAK-STAT pathway revealed that JAK2 itself, enhancers of JAK2 signaling and components of cytokine receptors that signal predominantly via JAK2 are upregulated in primary cutaneous CD8+ aggressive epidermotropic cytotoxic T-cell lymphoma (pcAECyTCL). (D) Activation of the JAK-STAT pathway (via STAT3 and/or STAT5) in pcAECyTCL was confirmed by immunohistochemistry (IHC) on tumor tissue from sequenced patients (i.e., AEC1/3/5-10). Neoplastic cells exhibited activated STAT3 and/or STAT5 in the nucleus. Normal skin (control) displayed STAT3 activation in keratinocytes and endothelial cells as well as STAT5 activation in melanocytes and endothelial cells. Scale bar, 50 mm.