Single-nucleus ATAC-seq analysis resolves chromatin and transcriptional features of fibrolamellar carcinoma

Fibrolamellar carcinoma (FLC) is a rare malignancy disproportionately affecting adolescents and young adults with no curative therapy. FLC is characterized by thick stroma, which has long suggested an important role of the tumor microenvironment. Over the past decade, several studies have revealed aberrant chromatin activity and gene expression in FLC. However, an important limitation of these efforts is that they were conducted on bulk tumor samples. Consequently, the cell types that contribute to the different epigenomic and transcriptional features of FLC have remained unknown. In this study we primarily leverage single nucleus ATAC-seq, along with supporting single nucleus RNA-seq, to unveil cell-type specific signal for chromatin activity, microRNAs, transcription factor networks (such as CREB3L1), and super enhancers including those nearby to notable FLC-enriched genes such as CDH11 and SLC16A14. The results provide a high resolution map of chromatin features of FLC, which in turn affords the opportunity to study cell type specific transcriptional reprogramming in the FLC tumor microenvironment.