Genome-Wide Analysis of DNA Methylation in Pseudomyxoma Peritonei Originated from Appendiceal Neoplasms.

INTRODUCTION: Pseudomyxoma peritonei (PMP) is a disease characterized by progressive accumulation of intraperitoneal mucinous ascites produced by neoplasms in the abdominal cavity. Since the prognosis of patients with PMP remains unsatisfactory, the development of effective therapeutic drug(s) is a matter of pressing concern. Genetic analyses of PMP have clarified the frequent activation of GNAS and/or KRAS. However, the involvement of global epigenetic alterations in PMPs has not been reported. METHODS: To clarify the genetic background of the 15 PMP tumors, we performed genetic analysis using AmpliSeq Cancer HotSpot Panel v2. We further investigated global DNA methylation in the 15 tumors and eight noncancerous colonic epithelial tissues using MethylationEPIC array BeadChip (Infinium 850k) containing a total of 865,918 probes. RESULTS: This is the first report of comprehensive DNA methylation profiles of PMPs in the world. We clarified that the 15 PMPs could be classified into at least two epigenotypes, unique methylation epigenotype (UME) and normal-like methylation epigenotype (NLME), and that genes associated with neuronal development and synaptic signaling may be involved in the development of PMPs. In addition, we identified a set of hypermethylation marker genes such as HOXD1 and TSPYL5 in the 15 PMPs. CONCLUSIONS: These findings may help the understanding of the molecular mechanism(s) of PMP and contribute to the development of therapeutic strategies for this life-threatening disease.

Wnt/ß-catenin signaling regulates amino acid metabolism through the suppression of CEBPA and FOXA1 in liver cancer cells.

Deregulation of the Wnt/ß-catenin pathway is associated with the development of human cancer including colorectal and liver cancer. Although we previously showed that histidine ammonia lyase (HAL) was transcriptionally reduced by the ß-catenin/TCF complex in liver cancer cells, the mechanism(s) of its down-regulation by the complex remain to be clarified. In this study, we search for the transcription factor(s) regulating HAL, and identify CEBPA and FOXA1, two factors whose expression is suppressed by the knockdown of ß-catenin or TCF7L2. In addition, RNA-seq analysis coupled with genome-wide mapping of CEBPA- and FOXA1-binding regions reveals that these two factors also increase the expression of arginase 1 (ARG1) that catalyzes the hydrolysis of arginine. Metabolome analysis discloses that activated Wnt signaling augments intracellular concentrations of histidine and arginine, and that the signal also increases the level of lactic acid suggesting the induction of the Warburg effect in liver cancer cells. Further analysis reveals that the levels of metabolites of the urea cycle and genes coding its related enzymes are also modulated by the Wnt signaling. These findings shed light on the altered cellular metabolism in the liver by the Wnt/ß-catenin pathway through the suppression of liver-enriched transcription factors including CEBPA and FOXA1.

Expression of PVRL4, a molecular target for cancer treatment, is transcriptionally regulated by FOS.

PVRL4 (or nectin­4) is a promising therapeutic target since its upregulated expression is found in a wide range of human cancer types. Enfortumab vedotin, an antibody­drug conjugate targeting PVRL4, is clinically used for the treatment of urothelial bladder cancer. In addition, rMV­SLAMblind, a genetically engineered oncolytic measles virus, can infect cancer cells and induce apoptosis through interaction with PVRL4. Although PVRL4 transcript levels are elevated in breast, lung and ovarian cancer, the mechanisms of its upregulation have not yet been uncovered. To clarify the regulatory mechanisms of elevated PVRL4 expression in breast cancer cells, Assay for Transposase­Accessible Chromatin­sequencing and chromatin immunoprecipitation­sequencing (ChIP­seq) data were used to search for its regulatory regions. Using breast cancer cells, an enhancer region was ultimately identified. Additional analyses, including ChIP and reporter assays, demonstrated that FOS interacted with the PVRL4 enhancer region, and that alterations of the FOS­binding motifs in the enhancer region decreased reporter activity. Consistent with these data, exogenous expression of FOS enhanced the reporter activity and PVRL4 expression in breast cancer cells. Furthermore, RNA­seq analysis using breast cancer cells treated with PVRL4 small interfering RNA revealed its possible involvement in the cytokine response and immune system. These data suggested that FOS was involved, at least partly, in the regulation of PVRL4 expression in breast cancer cells, and that elevated PVRL4 expression may regulate the response of cancer cells to cytokines and the immune system.