Abstract 3837: Selective ezh2 functional activation alters the metastatic landscape of triple negative breast cancer

Abstract

Abstract India is the TNBC capital of the world due to its highest (31%) prevalence and globally it has huge unmet medical need for its high mortality rate. Aggressive early metastasis is the key for such poor clinical outcome. So, there is a dire need to tackle this deadly disease worldwide by targeting its metastatic process. Epigenetic modulator Enhancer of Zeste homolog 2 (EZH2) promotes hetero-chromatinization of target genes by tri-methylating lysine at 27 of histone H3 (H3K27me3) and it has been shown to be associated with poor prognosis of TNBC. Besides its canonical function as a transcriptional repressor, EZH2 protein has recently been observed to perform H3K27me3 independent functions. Contribution of EZH2 protein (non-canonical) versus H3K27me3 dependent (canonical) function in TNBC pathogenesis remains poorly understood. Here, we aim to dissect the differential role of EZH2 protein versus H3K27me3 in the context of TNBC growth and metastasis. Utilizing stable EZH2 (protein versus hyperactivated H3K27me3) TNBC cells, we discovered that selective hyperactivation of H3K27me3 function of EZH2 but not its protein overexpression markedly promotes cell migration and invasion though cellular proliferation remains unaltered in both the cases. EZH2 protein overexpression (EPOE) and hyperactivation of H3K27me3 (EFHA) in TNBC cells resulted in similar tumor volume and growth pattern in-vivo in an orthotopic TNBC animal model but mice bearing EFHA tumors died significantly earlier than control and EPOE mice. Sequential Luc-GFP/Td tomato based live animal imaging of tumor bearing mice confirmed that EFHA profoundly augments TNBC metastasis compared to control and interestingly, it changes metastatic landscape of TNBC. Control tumors tend to metastasize to lung whereas; EFHA tumors metastasize to spleen first. Splenic metastasis of TNBC shows selective hyperactivation of H3K27me3 as compared to lung and liver metastasis at basal state. EZH2 functional inhibitor EPZ-6438 (currently in Phase-II clinical trial) though did not alter TNBC primary tumor growth but significantly abrogated TNBC metastasis and increased the life expectancy of tumor bearing mice. The high-throughput Illumina RNA-sequencing data identified unique gene signature of EFHA mediated TNBC metastasis corroborating with patient samples and TCGA database. In summary, our data indicate that splenic metastasis of TNBC may be driven by trimethylation function of EZH2 and targeting the methyltransferase activity of EZH2 could be a wonderful strategy to prevent TNBC metastasis in the clinic. Citation Format: Ayushi Verma, Akhilesh Singh, Anup Kumar Singh, Priyank Chaturvedi, Mushtaq Ahmad Nengroo, Krishan kumar Saini, abhipsa Sinha, Dipak Datta. Selective ezh2 functional activation alters the metastatic landscape of triple negative breast cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3837.