Abstract 102P
Background
Angiosarcomas are a group of aggressive rare tumors of endothelial origin. The genomic landscape of the disease was recently characterized, identifying distinct subtypes defined by ultraviolet (UV) mutational signatures and human herpesvirus-7 (HHV-7) as possible aetiologies.
Methods
To further characterize the molecular events regulating angiosarcoma development, we investigated the epigenomic enhancer landscape using H3K27ac chromatin immunoprecipitation with sequencing (ChIP-seq) of tumor samples (n=14) and their matched normal tissue where available (n=9). RNA-seq was also performed for tumor (n=16) and normal tissue (n=7) samples. Tumor (MO-LAS, ISO-HAS, ASM) and normal HDMEC cell-lines were similarly profiled.
Results
Unsupervised hierarchical clustering of H3K27ac signals at enhancers revealed global similarity between tumor samples, regardless of UV or HHV-7 status. Among the top ranking tumor-specific differentially-bound enhancers and expressed genes include PREX1, CCR1, LYN, PIK3R6, CSF2RB, CKAP2L, BCL2A1, HCK, RHOH and CXCL6. We focused on LYN, a potentially-druggable Src-family kinase. In keeping with initial observations, LYN was expressed higher in the tumor cell-lines by quantitative PCR and further validated on Western blot. Bafetinib, a known inhibitor of LYN kinase, was able to inhibit the viability of all tumor cell-lines in a dose-dependent manner at 72 hours (IC50 all between 5-10 μM), while decreasing protein expression of LYN and phospho-LYN. However, HDMEC cells were relatively resistant (IC50 > 10 μM). Finally, to investigate transcription factor-binding site enrichment, we analysed frequencies of cognate consensus DNA-binding motifs at super-enhancer regions using HOMER motif analysis and identified bZIP-domain and EST-domain transcription factors as candidate angiosarcoma regulators, including that of LYN expression.
Conclusions
We described the enhancer landscape of human angiosarcomas, highlighting LYN as a potential therapeutic target. Our preliminary analysis of potential transcription factor binding identified candidate transcription factors responsible for regulating LYN expression.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
This work was supported by the Singapore Ministry of Health’s National Medical Research Council under its Transition Award (TA21jun-0005) and RTF Seed Fund (SEEDFD21jun-0002); SingHealth Duke-NUS Academic Medical Centre and Oncology ACP Sarcoma Research Fund (08-FY2020/EX/25-A96 and 08-FY2020/EX/75-A151).
Disclosure
J.Y. Chan: Financial Interests, Personal, Invited Speaker: Takeda Pharmaceuticals, AstraZeneca, Novartis, Roche, MSD, Specialised Therapeutics; Financial Interests, Personal, Advisory Board: Antengene; Financial Interests, Personal, Research Grant: SymBio Pharmaceuticals, Scinnohub Pharmaceuticals, Invitae, Miltenyi Biotec; Financial Interests, Personal, Product Samples: Stemcell Technologies, MGI Tech, Twist Biosciences; Financial Interests, Personal, Other, Travel support: Janssen, Amgen. All other authors have declared no conflicts of interest.