Genomic analysis of HPV-positive versus HPV-negative oesophageal adenocarcinoma identifies a differential mutational landscape

Background: High-risk human papillomavirus (hr-HPV) has been implicated in a subset of patients with oesophageal adenocarcinoma (OAC). We therefore hypothesised that HPV associated OAC may have distinct genomic aberrations compared with viral negative oesophageal cancer. Methods: Whole exome sequencing was performed to explore the mutational landscape and potential molecular signature of HPV-positive versus HPV-negative OAC. Four hr-HPV-positive and 8 HPV-negative treatment-naive fresh-frozen OAC tissue specimens and matched normal tissue were analysed to identify somatic genomic mutations. Data were subjected to cancer driver gene identification and pathway analysis. Results: The HPV-positive cohort harboured approximately 50% less non-silent somatic mutations than the virus-negative patients with oesophageal cancer (1.31 mutations/Mb vs 2.56 mutations/Mb, p=0.048). TP53 aberrations were absent in the HPV-positive OAC group whereas 50% of the HPV-negative patients with OAC exhibited TP53 mutations. HPV-negative cancers were enriched with non-silent mutations in cancer driver genes, but not HPV-positive tumours. Enriched A>C transversions at adenine-adenine (AA) dinucleotide was observed in 5/7 Siewert class I OAC samples but none (0/5) in Siewert class II tumours (p=0.027). Conclusions: These findings demonstrate distinct genomic differences between HPV-positive and HPV-negative OACs indicating different biological mechanisms of tumour formation

HNF4A and GATA6 loss reveals therapeutically actionable subtypes in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) can be divided into transcriptomic subtypes with two broad lineages referred to as classical (pancreatic) and squamous. We find that these two subtypes are driven by distinct metabolic phenotypes. Loss of genes that drive endodermal lineage specification, HNF4A and GATA6, switch metabolic profiles from classical (pancreatic) to predominantly squamous, with glycogen synthase kinase 3 beta (GSK3b) a key regulator of glycolysis. Pharmacological inhibition of GSK3b results in selective sensitivity in the squamous subtype; however, a subset of these squamous patient-derived cell lines (PDCLs) acquires rapid drug tolerance. Using chromatin accessibility maps, we demonstrate that the squamous subtype can be further classified using chromatin accessibility to predict responsiveness and tolerance to GSK3b inhibitors. Our findings demonstrate that distinct patterns of chromatin accessibility can be used to identify patient subgroups that are indistinguishable by gene expression profiles, highlighting the utility of chromatin-based biomarkers for patient selection in the treatment of PDAC