Hypermethylation of MAPK13 Promoter in Oesophageal Squamous Cell Carcinoma Is Associated with Loss of p38[delta] MAPK Expression

The loss of tumour suppressor gene function is a hallmark of malignant transformation and can occur by a variety of genetic and/or epigenetic alterations. We have previously characterised p38[delta] mitogen-activated protein kinase (MAPK) as a tumour suppressor in oesophageal squamous cell carcinoma (OESCC) and outlined how loss of p38[delta] MAPK expression promotes increased proliferation and migration, as well as reduced chemosensitivity. Our aim was to investigate the underlying molecular causes of loss of p38[delta] MAPK expression in OESCC. Sequence analysis of DNA from p38[delta] MAPK positive and p38[delta] MAPK negative OESCC cell lines was used to investigate potential loss of function causing mutations. Epigenetic control of p38[delta] expression in OESCC was examined using methylation-specific PCR and sequencing of bisulfite-converted DNA. We did not identify any mutations in the MAPK13 sequence in OESCC cell lines which lack p38[delta] MAPK expression. However, we identified a differential pattern of methylation between p38[delta] MAPK positive and p38[delta] MAPK negative cell lines. We outline here for the first time differential MAPK13 promoter methylation in OESCC. Our results suggest that epigenetic alterations are responsible, in part, for the suppression of p38[delta] MAPK expression and promotion of tumourigenesis in OESCC.