Molecular Pathology of Gastric Carcinoma

Gastric carcinoma (GC) is a biologically heterogeneous disease involving numerous genetic and epigenetic alterations. A very small proportion of GCs can be caused by a specific germ-line mutation of the E-cadherin gene (CDH1). Sporadic GC is developed through multistep processes that begin with Helicobacter pylori-induced atrophic gastritis. Epstein-Barr virus is another infectious cause of GC, and the above two infection-associated GCs are characterized by global CpG island methylation in the promoter region of cancer-related genes. Mutations of tumor protein p53 (TP53) and β-catenin (CTNNB1) genes occur early in the development of GC and contribute to gastric carcinogenesis. Furthermore, significant numbers of GCs show loss of Runx3 due to hemizygous deletion and hypermethylation of the promoter region. Aberrant Cdx2 expression has been shown in precancerous lesions as well as GC. However, it remains unclear whether Cdx2 plays an oncogenic role in gastric carcinogenesis. GC with microsatellite instability is also a well-defined subset exhibiting distinctive clinicopathologic features. Targeted therapy against GC with ERBB2 amplification recently improved the prognosis of patients with advanced GC. In addition, epigenetic changes in GC could be attractive targets for cancer treatment with modulators. A genome-wide search has been undertaken to identify novel methylation-silenced genes in GC, which will help us understand the overall molecular features of GC and further provide novel opportunities in the treatment of GC.