Pathobiological behavior and molecular mechanism of signet ring cell carcinoma and mucinous adenocarcinoma of the stomach:A comparative study

AIM:To elucidate the distinctive pathobiological behavior between signet ring cell carcinoma (SRC) and mucinous adenocarcinoma of the stomach.METHODS: Based on the histological growth patterns and cell-functional differentiation classifications of stomach carcinoma, we conducted a series of comparative studies.All paraffin-embedded and frozen blocks were collected from the files of Cancer Institute of China Medical University. On the basis of histopathological observation, we applied enzymatic and mucous histochemistry, immunohistochemistry,flow cytometry (FCM) and molecular biology to compare these two categories of gastric cancers in terms of the DNA ploidy, proliferative kinetics, the expression of gastric carcinoma associated gene product and instabilities of mitochondrial DNA (mtDNA).RESULTS:Gastric SRC was commonly seen in females below 45 years, mostly presenting diffuse growth and ovary or uterine cervix metastasis. The majority of SRC were absorptive and mucus-producing functional differentiation type (AMPFDT), which growth relied on estrogen. Meanwhile,stomach mucinous adenocarcinomas were mostly observed in males over 50 years, prone to massive growth or nest growth and extensive peritoneal infiltration, showing two categories of cell-functional differentiation types: AMPFDT and mucus-secreting functional differentiation type (MSFDT).Expressions of ER, enzyme c-PDE and 67kDaLN-R in SRC were evidently higher than that in mucinous adenocarcinoma,while expressions of LN, CN-Ⅳ, CD44v6, and PTEN protein were obviously lower in SRC than that in mucinous adenocarcinoma (P<0.05).There was no statistic significance in VEGF, ECD and instabilities of mtDNA (P>0.05) between the above two gastric carcinomas.CONCLUSION: Though SRC and mucinous adenocarcinoma were both characterized by abundant mucus-secretion, they were quite different in morphology, ultrastructure, cell-functional differentiation and protein expression, indicating different mechanisms of carcinogenesis. We concluded that combining histological growth patterns, cell-functional differentiation type with tumor related markers might be significant in early diagnosis and prognosis assessment for SRC and mucinous adenocarcinoma of the stomach.

Pathobiological significance of vascular endothelial growth factor and Maspin expressions in human gastric carcinoma

AIM: To investigate the correlation between expression of vascular endothelial growth factor (VEGF) and cell differentiation, invasion, metastasis and Maspin expression in gastric carcinoma.METHODS: Formalin-fixed paraffin-embedded tissue specimens from 73 cases of gastric carcinoma were studied with SP immunohistochemistry, using anti-VEGF monoclonal antibody, and thirty-nine of them were studied using antiMaspin monoclonal antibody. VEGF expression was compared with the clinical stage, lymph node metastasis, and Borrmann's and WHO's classification of gastric carcinoma.RESULTS: The positive rate of VEGF expression was significantly higher in adjacent non-carcinoma epithelia (ANCE) than in non-metaplastic, non-carcinoma gastric epithelia (NMNCE), which were at least 4 cm distant from the primary tumor (P = 0.000, x^2= 73.03). The positive rate of VEGF expression was significantly higher in advanced gastric carcinoma (AGC) than in early gastric carcinoma (EGC) (P = 0.032, x^2 = 4.62). The positive rate of VEGF expression in gastric carcinomas with lymph node metastases was significantly higher than that in those without metastasis (P = 0.006, x^2 = 7.47). Maspin was weakly expressed in 16 out of 39 cases of NMNCE, and the positive immunoreaction was limited to gland cells of the stomach body. There was no significant correlation between the expression of VEGF and histological or gross classifications, and correlation between the expressions of VEGF and Maspin in gastric carcinoma (P = 0.648, x^2 = 0.21).CONCLUSION: Expression of VEGF is significantly correlated to the malignant biological behaviors of gastric carcinoma,but there is no significant correlation between the expression of VEGF and Maspin.

Mutations of mitochondrial 12S rRNA in gastric carcinoma and their significance

AIM: To detect the variations of mitochondrial 12S rRNA in patients with gastric carcinoma, and to study their significance and the relationship between these variations and the genesis of gastric carcinoma.METHODS: PCR amplified mitochondrial 12S rRNA of 44 samples including 22 from gastric carcinoma tissues and 22 from adjacent normal tissues, was detected by direct DNA sequencing. Then laser capture microdissection technique (LCM) was used to separate the cancerous cells and dysplasia cells with specific mutations. Denaturing high performance liquid chromatography (DHPLC) plus allele-specific PCR (ASPCR), nest-PCR and polyacrylamide gel electrophoresis (PAGE)were used to further evaluate this mutant property and quantitative difference of mutant type between cancerous and dysplasia cells. Finally, RNAdraw biosoft was used to analyze the RNA secondary structure of mutant-type 12S rRNA.RESULTS: Compared with Mitomap database, some new variations were found, among which np652 G insertion and np716 T-G transversion were found only in cancerous tissues.There was a statistic difference in the frequency of 12S rRNA variation between intestinal type (12/17, 70.59%) and diffusive type (5/17, 29.41%) of gastric carcinoma (P＜0.05).DHPLC analysis showed that 12S rRNA np652 G insertion and np716 T-G transversion were heteroplasmic mutations.The frequency of 12S rRNA variation in cancerous cells was higher than that in dysplasia cells (P＜0.01). 12S rRNA np652 G insertion showed obviously negative effects on the stability of 12S rRNA secondary structure, while others such as T-G transversion did not.CONCLUSION: The mutations of mitochondrial 12S rRNA may be associated with the occurrence of intestinal-type gastric carcinoma. Most variations exist both in gastric carcinomas and in normal tissues, and they might not be the characteristics of tumors. However, np652 G insertion and np716 T-G transversion may possess some molecular significance in gastric carcinogenesis. During the process from normality to dysplasia, then to carcinoma, 12S rRNA tends to convert from homoplasmy (wild type) to heteroplasmy,then to homoplasmy (mutant type, np717 T-G).