Alterations of p73 preferentially occur in gastric adenocarcinomas with foveolar epithelial phenotype

Involvement of Krüppel-like factor 6 (KLF6) mutation in the development of nonpolypoid colorectal carcinoma

AIM: To examine Krüppel-like factor 6 (KLF6) mutations in nonpolypoid-type tumors and alterations of K-ras, p53, and B-raf in relation between mutation and morphologic type, particularly nonpolypoid-type colorectal carcinomas.

METHODS: Fifty-five early nonpolypoid colorectal carcinomas were analyzed. Loss of heterozygosity (LOH) of KLF6 and p53 was determined by microsatellite assay. Mutations of KLF6, K-ras, and B-raf were examined by polymerase chain reaction-single-strand conformation polymorphism followed by direct sequencing. In LOH-positive and/or mutation-positive tumors, multiple (4-7) samples in each tumor were microdissected and examined for genetic alterations. p53 expression was evaluated by immunohistochemistry.

RESULTS: LOH of KLF6 and p53 was found in 14 of 29 (48.3%) and 14 of 31 (45.2%) tumors, respectively. In 10 of the 14 (71.4%) KLF6 LOH-positive tumors and 9 of the 14 (64.3%) p53 LOH-positive tumors, LOH was found in all of the microdissected samples. In 1 of the 10 (10.0%) KLF6 LOH-positive tumors, a single missense mutation was identified. K-ras and B-raf mutations were found in 5 of 55 (9.1%) and 6 of 55 (10.9%) tumors, respectively. However, these mutations were detected only in subsets of microdissected tumor samples.

CONCLUSION: These data suggest that KLF6 and p53 mutations are involved in the development of nonpolypoid colorectal carcinoma, whereas K-ras and B-raf mutations are not.

Clinicopathological significances of P73 and P53 protein expression in gastric carcinomas with tissue microarray technique

AIM: To investigate the expression of P73 and mutant P53 (mP53) gene coding proteins and their significances in gastric carcinoma.

METHODS: Two tissue microarray blocks containing 104 cases of gastric cancer and precancerous lesions (1.0 mm each in diameter) was constructed. SABC immunohistochemical stainning was used to detect the expression of P73 and mP53 proteins and the correlation between their roles and the pathological behavior of gastric carcinoma was investigated.

RESULTS: The positive rate of P73 protein was significantly higher in gastric cancer, intestinal metaplasia and atypical hyperplasia than that in the normal tissues (90.1%, 44.0%, 80.0% vs 17.9%, P < 0.01). The expression of P73 protein was also markedly higher in gastric carcinoma of Borrman Ⅲ/Ⅳ types than that of Borrman Ⅱ type (92.9%/100% vs 57.1%, P < 0.05). Moreover, the expression P73 protein was markedly increased in gastric cancer with lymph node metastasis, liver metastasis and ovarian metastasis as compared with that in non-metastatic cancer (94.4%, 100%, 100% vs 76.2%, P < 0.01). There was a positive correlation between P73 and mP53 expression (χ² = 9.6736, P < 0.01).

CONCLUSION: P73 expression is correlated with the malignant behaviors of gastric cancer. Although P73 protein has a similar construction to P53 protein, its expression shows a positive correlation with that of mP53 protein. This finding indicates that P73 may play a role in the carcinogenesis of gastric cancer as a mimic mutant of P53.

Cellular and molecular aspects of gastric cancer

Gastric cancer remains a global killer with a shifting burden from the developed to the developing world. The cancer develops along a multistage process that is defined by distinct histological and pathophysiological phases. Several genetic and epigenetic alterations mediate the transition from one stage to another and these include mutations in oncogenes, tumour suppressor genes and cell cycle and mismatch repair genes. The most significant advance in the fight against gastric caner came with the recognition of the role of Helicobacter pylori (H pylori) as the most important acquired aetiological agent for this cancer. Recent work has focussed on elucidating the complex host/microbial interactions that underlie the neoplastic process. There is now considerable insight into the pathogenesis of this cancer and the prospect of preventing and eradicating the disease has become a reality. Perhaps more importantly, the study of H pylori-induced gastric carcinogenesis offers a paradigm for understanding more complex human cancers. In this review, we examine the molecular and cellular events that underlie H pylori-induced gastric cancer.

Primary adenocarcinomas of lower esophagus, esophagogastric junction and gastric cardia: in special reference to China

Gastric cardia adenocarcinoma (GCA) is an under-studied subject. The pathogenesis, molecular changes in the early stage of carcinogenesis and related risk factors have not been well characterized. There is evidence, however, that GCA differs from cancer of the rest of the stomach in terms of natural history and histopathogenesis. Adenocarcinomas of the lower esophagus, esophagogastric junction (EGJ) and gastric cardia have been given much attention because of their increasing incidences in the past decades, which is in striking contrast with the steady decrease in distal stomach adenocarcinoma. In China, epidemiologically, GCA shares very similar geographic distribution with esophageal squamous cell carcinoma (SCC), especially in Linzhou (formerly Linxian County), Henan Province, North China, the highest incidence area of esophageal SCC in the world. Historically, both GCA and SCC in these areas were referred to as esophageal cancer (EC) by the public because of the common syndrome of dysphagia. In Western countries, Barrett's esophagus is very common and has been considered as an important precancerous lesion of adenocarcinoma at EGJ. Because of the low incidence of Barrett's esophagus in China, it is unlikely to be an important factor in early stage of EGJ adenocarcinoma development. However, Z line up-growth into lower esophagus may be one of the characteristic changes in these areas in early stage of GCA development. Whether intestinal metaplasia (IM) is a premalignant lesion for GCA is still not clear. Higher frequency of IM observed at adjacent GCA tissues in Henan suggests the possibility of IM as a precancerous lesion for GCA in these areas. Molecular information on GCA, especially in early stage, is very limited. The accumulated data about the changes of tumor suppressor gene, such as p53 mutation, and ontogeny, such as C-erbB2, especially the similar alterations in GCA and SCC in the same patient, indicated that there might be some similar risk factors, such as nitrosamine, involved in both GCA and SCC in Henan population. The present observations also suggest that GCA should be considered as a distinct entity.