Expression of the CIC-DUX4 fusion oncoprotein mirrors human CIC-rearranged sarcoma in a transgenic mouse model (ChIP-Seq)

CIC-DUX4 sarcoma (CDS) is a rare but highly aggressive undifferentiated small round cell sarcoma driven by a fusion between the tumor suppressor Capicua (CIC) and DUX4. Currently, there are no effective treatments and efforts to identify and translate better therapies is limited by the scarcity of tissues and patients. To minimize, we made three genetically engineered mouse models of CDS (Ch7CDS, Ai9CDS, and TOPCDS). Remarkably, chimeric mice from all three models developed spontaneous tumors and widespread metastasis in the absence of Cre-recombinase. The penetrance of spontaneous (Cre-independent) tumor formation was complete irrespective of bi-allelic CIC function and loxP site proximity. Characterization of primary and metastatic mouse tumors showed that they consistently expressed the CIC-DUX4 fusion protein as well as other downstream markers of the disease authenticating them as CDS. Lastly, tumor-derived cell lines were generated and ChIP-seq was preformed to map fusion-gene specific binding using an N-terminal HA epitope tag. These datasets, along with paired H3K27ac ChIP-seq maps, validate CIC-DUX4 as a neomorphic transcriptional activator and point to ETS family transcription factors as cooperative and redundant drivers of the core regulatory circuitry. To authenticate the tumors and tumor-derived cell lines obtained from our genetically-engineered mouse models (Ch7CDS, Ai9CDS, TOPCDS), RNA-sequencing and ChIP-sequencing was performed. Comparative gene expression profiling analysis was carried out using KP (KrasG12D, p53fl/fl) tumors/cells and normal hindlimb skeletal muscle as controls.