BACKGROUND: The Wnt signalling receptor ROR2 has been identified as a potential target in numerous cancers, however its exact role remains controversial. ROR2 has been shown to play distinct roles in regards to tumorigenesis in different tumour types. Our previous study suggested a potential tumour suppressor role for ROR2 in endometrial cancer (EC), however the mechanism associated with ROR2 repression in EC remains unclear. ROR2 has been found to be epigenetically inactivated in colorectal cancer. OBJECTIVE: The aim of this study was to investigate the role of ROR2 in EC, and to determine if ROR2 expression in EC was regulated epigenetically. METHODS: The correlation between ROR2 mRNA expression levels and clinicopathological parameters, including overall survival (OS) was analysed in The Cancer Genome Atlas Uterine Corpus Endometrial Carcinoma (TCGA-UCEC, n=546) cohort and GEO datasets (GSE17025, n=91). Immunohistochemistry (IHC) of ROR2 was performed on a large EC patient cohort (Australia-wide population-based Australian EC Study, ANECS, n=499). The correlation between ROR2 staining intensity (0-3) and clinicopathological parameters as well as 5-year progression free survival (PFS) and OS was analysed. Cox regression was also applied to analyse the impact of selected covariates (age, BMI, FIGO stage and grade) on the PFS and OS. Four EC cell lines (KLE, MFE-296, Ishikawa and ARK-1) and eight clinical EC samples were analysed for ROR2 methylation via COmbined Bisulphite Restriction Analysis (COBRA) and bisulphite genomic sequencing (BGS). RESULTS:ROR2 promoter methylation or reduced ROR2 expression were both found to correlate with lower OS, high grade and serous EC in the TCGA-UCEC and GEO dataset at p<0.05 level. In our ANECS cohort, the same trend of correlation was observed of ROR2 expression and grade (p=0.062). No significant correlation was observed for ROR2 expression with OS or PFS in this cohort at univariate or multivariable survival analysis. ROR2 was epigenetically silenced by promoter methylation in KLE and ARK-1 cell lines. There was also a significant correlation between ROR2 expression level and promoter methylation in our patient cohort (r=-0.79, p=0.02). CONCLUSION: ROR2 plays a tumour suppressor role in EC and is epigenetically suppressed with the development of disease. It may therefore be a diagnostic or therapeutic candidate for EC.

Citation Format: Dongli Liu, Luis Enriquez, Benjamin Daniels, Tracy O'Mara, Katrina Tang, Caroline Ford. ROR2 is epigenetically regulated in endometrial cancer [abstract]. In: Proceedings of the AACR Virtual Special Conference: Endometrial Cancer: New Biology Driving Research and Treatment; 2020 Nov 9-10. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(3_Suppl):Abstract nr PO042.