Oncogenic RAD21 Amplification Suppresses Interferon Signalling to Promote Immune Evasion in Ovarian Cancer

Ovarian cancer (OV) is the leading cause of mortality from gynaecological malignancies with poor prognosis and limited therapeutic options. Prevalent copy number alteration (CNA) is a genetic characteristic of OV, but its contribution to tumorigenesis remain unclear. Here, we identify RAD21, a component of the cohesin complex, as a frequently amplified and overexpressed oncogene in high grade serous ovarian cancer (HGSOC), the most common subtype of OV. RAD21 copy number amplification and overexpression are correlated with poor prognosis in HGSOC. In HGSOC cells and xenograft models, depletion of RAD21 inhibited cell proliferation by inducing mitotic phase arrest and thereby reducing tumour growth, whereas overexpression of RAD21 conferred resistance to carboplatin. Mechanistically, we found that RAD21 interacts with YAP/TEAD4 transcriptional co-repressors and recruits NuRD complex to suppress the downstream targets. Additionally, genetic and pharmacologic inhibition of YAP disrupts the co-repressor complex to suppress the oncogenic activity of RAD21 and recapitulates the phenotypes of RAD21 depletion in HGSOC. Therefore, our work sheds light on the oncogenic role of frequent CNAs and identifies a previously unrecognized role of RAD21/YAP complex which contributes to tumorigenesis and chemo-resistance in HGSOC. Overall design: 1.RNA-seq for OVCAR8 cells upon knock-down of TEAD4. 2. ChIP-seq for TEAD4.