| Introduction: It is assumed that some differentiated-type(DT) gastric cancer transforms into undifferentiated-type(UDT) gastric cancer, and differentiated/undifferentiated mixed-histological-type(MT) gastric cancer is considered to be a lesion in which DT gastric cancer has partially transformed into UDT gastric cancer. By dividing MT gastric cancer into DT component and UDT component and performing comprehensive genetic analysis, we aimed to analyze the mechanism by which DT gastric cancer changes into UDT gastric cancer. Methods: Pathological tissues of resected specimens from 8 patients with MT gastric cancer were used and divided into DT component and UDT component using laser microdissection. DNA was extracted from each component, and DNA methylation analysis was performed using the Infinium MethylationEPIC array (Illumina, CA, USA). Results: After filtering, 706236 probes were used for analysis. Among the genes showing high methylation levels in the DT component, when we searched for the CpG island in the promoter region under the conditions of delta b values > 0.05 and p values < 0.05, multiple probes were detected, one of which had a gene symbol of CDX2. In 2 of 8 cases, immunohistochemical staining revealed CDX2 expression in the DT component, but not in the UDT component. Conclusion: Our results suggest that DNA methylation is involved in the mechanism by which DT gastric cancer transforms into UDT gastric cancer. |
