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Prognostication in oesophageal cancer on the basis of preoperative variables is challenging. Many of the accepted predictors of survival are only derived after surgical treatment and may be influenced by neoadjuvant therapy. This study aims to explore the relationship between pre-treatment endoscopic tumour morphology and postoperative survival.Patients with endoscopic descriptions of tumours were identified from the prospectively managed databases including the OCCAMS database. Tumours were classified as exophytic, ulcerating or stenosing. Kaplan Meier survival analysis and multivariable Cox regression analyses were performed to determine hazard ratios (HR) with 95% confidence intervals.262 patients with oesophageal adenocarcinoma undergoing potentially curative resection were pooled from St Thomas' Hospital (161) and the OCCAMS database (101). There were 70 ulcerating, 114 exophytic and 78 stenosing oesophageal adenocarcinomas. Initial tumour staging was similar across all groups (T3/4 tumours 71.4%, 70.2%, 74.4%). Median survival was 55 months, 51 months and 36 months respectively (p 0.001). Rates of lymphovascular invasion (P = 0.0176), pathological nodal status (P = 0.0195) and pathological T stage (P = 0.0007) increased from ulcerating to exophytic to stenosing lesions. Resection margin positivity was 21.4% in ulcerating tumours compared to 54% in stenosing tumours (p 0.001). When compared to stenosing lesions, exophytic and ulcerating lesions demonstrated a significant survival advantage on multivariable analysis (HR 0.56 95% CI 0.31-0.93, HR 0.42 95% CI 0.21-0.82).This study demonstrates that endoscopic morphology may be an important pre-treatment prognostic factor in oesophageal cancer. Ulcerating, exophytic and stenosing tumours may represent different pathological processes and tumour biology.

Summary: Protein arginine methyltransferase 1 (PRMT1) is overexpressed in various human cancers and linked to poor response to chemotherapy. Various PRMT1 inhibitors are currently under development; yet, we do not fully understand the mechanisms underpinning PRMT1 involvement in tumorigenesis and chemoresistance. Using mass spectrometry-based proteomics, we identified PRMT1 as regulator of arginine methylation in ovarian cancer cells treated with cisplatin. We showed that DNA-dependent protein kinase (DNA-PK) binds to and phosphorylates PRMT1 in response to cisplatin, inducing its chromatin recruitment and redirecting its enzymatic activity toward Arg3 of histone H4 (H4R3). On chromatin, the DNA-PK/PRMT1 axis induces senescence-associated secretory phenotype through H4R3me2a deposition at pro-inflammatory gene promoters. Finally, PRMT1 inhibition reduces the clonogenic growth of cancer cells exposed to low doses of cisplatin, sensitizing them to apoptosis. While unravelling the role of PRMT1 in response to genotoxic agents, our findings indicate the possibility of targeting PRMT1 to overcome chemoresistance in cancer. : Protein arginine methyltransferase 1 (PRMT1) overexpression is linked to cancer chemoresistance, but the mechanism is still unclear. Musiani et al. show that, upon cisplatin, PRMT1 is recruited by DNA-dependent protein kinase (DNA-PK) to chromatin, where it sustains the transcription of genes involved in the senescence-associated secretory phenotype (SASP), thus protecting cells from drug-induced apoptosis. Keywords: arginine methylation, MS-based proteomics, replication stress response, PRMT1, SASP, transcription, cisplatin, epigenetic drugs, DNA-PK

H3K27me3 is deposited at promoters by the preferential association of Polycomb repressive complex 2 (PRC2) with CpG-rich DNA elements regulating development by repressing gene transcription. H3K27 is also present in mono- and dimethylated states; however, the functional roles of H3K27me1 and H3K27me2 deposition remain poorly characterized. Here, we show that PRC2 activity is not only associated with H3K27me3 but also regulates all forms of H3K27 methylation in a spatially defined manner, contributing to different genomic functions in mouse embryonic stem cells. H3K27me1 accumulates within transcribed genes, promotes transcription, and is regulated by Setd2-dependent H3K36me3 deposition. Contrarily, H3K27me2 is present on approximately 70% of total histone H3 and is distributed in large chromatin domains, exerting protective functions by preventing firing of non-cell-type-specific enhancers. Considering that only 5%-10% of deregulated genes in PRC2-deficient cells are direct H3K27me3 targets, our data support an active role for all H3K27 methylated forms in regulating transcription and determining cell identity.