Genome binding/occupancy profiling by high throughput sequencing Expression profiling by high throughput sequencing
Summary
Epigenetic changes deregulate gene expression to drive oncogenesis. The reversible nature of these changes enables therapeutic targeting, as in cutaneous T-cell lymphoma (MF/SS), Histone deacetylase inhibitors (HDACi), which alter epigenetic modifications, are effective in ~30% of MF/SS patients. However, there are no markers that predict MF/SS progression or therapy resistance. We hypothesized that epigenetic alterations drive MF/SS progression and promote HDACi drug resistance. Therefore, we profiled the epigenomes and transcriptomes of malignant T cell purified from skin biopsies and peripheral blood from MF/SS patients (N=21) before and after treatment with HDACi, as well as in vitro HDACi-treated CD4+ T cells from healthy donors. Here we report for the first time the epigenome-wide map of acetylation changes in MF/SS patients treated with HDACi, and define the significant differences in regulatory element activity and corresponding transcriptional changes in HDACi-sensitive versus resistant tumors. Our studies identified genes not previously associated with MF/SS, nor with disease progression or HDACi resistance, and were enriched in pathways that regulate apoptosis (BIRC5), cell cycle (RRM2), and chromosome cohesion (CENPH). We also identified a striking number of genes whose products are involved in cell adhesion and migration, including CCR6, LAIR2, VCAM1, and EPCAM. The mRNA of LAIR2, which encodes a receptor protein secreted by activated T cells that binds collagen and prevents binding of the inhibitory receptor LAIR1, was significantly upregulated in MF/SS tumors that were resistant to HDACi therapy and manifested in both skin and peripheral blood. We also detected elevated levels of LAIR2 protein in the plasma of MF/SS patients with progressive disease. Taken together, these studies defined the first epigenome-wide acetylation landscape of HDACi responsive and resistant MF/SS tumors, identified significantly altered patterns of epigenetic regulation and corresponding gene expression in HDACi resistant MF/SS tumors, and connected them to novel pathways of disease progression, particularly in cell adhesion and migration. These findings may represent novel predictive markers for MF/SS progression that are also targets for future therapeutic development.
Overall design
RNA-seq and ChIP-seq (H3K9/K14ac, H3K27ac) profiling of primary HDACi-treated CTCL peripheral blood and skin samples along with in vitro romidepsin treated healthy control CD4+ T cells.
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