Different patterns of beta-catenin expression in gastric carcinomas: relationship with clinicopathological parameters and prognostic outcome

Nuclear factor-kappa B inhibition reduces markedly cell proliferation in Epstein-Barr virus-infected stomach cancer, but affects variably in Epstein-Barr virus-negative stomach cancer

Nuclear factor-kappa B (NF-kappaB) inhibition by NF-kappaB p65-specific siRNA induced a near-cessation of cell proliferation in EBV-positive stomach cancer cell, and notably diminished cell proliferation in EBV- positive Raji lymphoma cell. In EBV-negative stomach cancer cells, NF-kappaB inhibition affected variably cell proliferation. Regardless of cell type, NF-kappaB inhibition suppressed antiapoptotic function of NF-kappaB, and tended to promote the nuclear accumulation of beta-catenin. This inverse relationship between NF-kappaB and beta-catenin was evident in 120 resected gastric carcinomas. Conclusively, NF-kappaB inhibition may be beneficial in the therapy of EBV-positive stomach cancer, but influence variously EBV-negative stomach cancer.

Epstein-Barr virus, beta-catenin, and E-cadherin in gastric carcinomas

Activated beta-catenin is suggested to inhibit NF-kappaB activation, and we previously demonstrated that NF-kappaB nuclear positivity was more frequent in Epstein-Barr virus (EBV)-infected gastric carcinomas. It is controversial that beta-catenin and E-cadherin are prognostic markers in gastric carcinomas. To define a relationship between beta-catenin and EBV, and the prognostic value of beta-catenin and E-cadherin, we analyzed in situ hybridization for EBV-encoded small RNAs, beta-catenin, and E-cadherin immunohistochemistry, and clinicopathological features in 111 gastric carcinomas. EBV infection was detected in seven carcinomas (6.3%); none of seven showed beta-catenin nuclear accumulation, and five out of seven revealed beta-catenin membranous loss or cytoplasmic expression. Eighty cases (72.1%) showed beta-catenin alteration; i.e., loss of membrane staining in 65 (58.6 %), cytoplasmic expression in 35 (31.5%), and nuclear accumulation in 15 (13.5%). E-cadherin alteration was observed in 34 cases (30.6%) and correlated with beta-catenin alteration. On multivariate analysis, the combined immunoexpression group of beta-catenin nuclear accumulation/ E-cadherin alteration and the advanced TNM cancer stage group showed poor patient's survival (p<0.05). In conclusion, beta-catenin activation through nuclear accumulation hardly occurred in EBV-infected gastric carcinomas. The combined immunoexpression pattern of beta-catenin and E-cadherin can be used as a prognostic marker in gastric carcinomas.

Differential expression of the eukaryotic release factor 3 (eRF3/GSPT1) according to gastric cancer histological types

BACKGROUND

There are now several lines of evidence to suggest that protein synthesis and translation factors are involved in the regulation of cell proliferation and cancer development.

AIMS

To investigate gene expression patterns of eukaryotic releasing factor 3 (eRF3) in gastric cancer.

METHODS

RNA was prepared from 25 gastric tumour biopsies and adjacent non-neoplastic mucosa. Real time TaqMan reverse transcription polymerase chain reaction (RT-PCR) was performed to measure the relative gene expression levels. DNA was isolated from tumour and normal tissues and gene dosage was determined by a quantitative real time PCR using SYBR Green dye.

RESULTS

Different histological types of gastric tumours were analysed and nine of the 25 tumours revealed eRF3/GSPT1 overexpression; moreover, eight of the 12 intestinal type carcinomas analysed overexpressed the gene, whereas eRF3/GSPT1 was overexpressed in only one of the 10 diffuse type carcinomas (Kruskal-Wallis Test; p < 0.05). No correlation was found between ploidy and transcript expression levels of eRF3/GSPT1. Overexpression of eRF3/GSPT1 was not associated with increased translation rates because the upregulation of eRF3/GSPT1 did not correlate with increased eRF1 levels.

CONCLUSIONS

Overexpression of eRF3/GSPT1 in intestinal type gastric tumours may lead to an increase in the translation efficiency of specific oncogenic transcripts. Alternatively, eRF3/GSPT1 may be involved in tumorigenesis as a result of its non-translational roles, namely (dis)regulating the cell cycle, apoptosis, or transcription.