[Detection of Mycoplasma hyorhinis in gastric cancer using bio-chip technology]

To determine the prevalence of Mycoplasma hyorhinis in archived paraffin-embedded gastric cancer tissue and to find whether Mycoplasma hyorhinis infection can influence gene expression level in gastric cancer cells.

A high-dense tissue microarray containing 105 gastric cancer samples, 101 benign margin samples and 62 non-cancerous gastric disease samples resected during operation was constructed. PD4, a specific anti-Mycoplasma-hyorhinis Mab, was used to detect the infection rate in all the samples in the tissue microarrays immunohistochemically. Then, cDNA microarray was used to pinpoint differentially the expressed genes between gastric cancer cell line MGC803 samples with and without Mycoplasma hyorhinis infection.

The infection rate of M. hyorhinis was 54.1% 53/98 in gastric cancer samples, 51.7% 45/87 in benign margin samples, and 15.8 % 9/57 in non-cancerous disease samples respectively. The difference of infection rates between gastric cancer and non-cancerous gastric disease was statistically significant (P = 0.001). Highly differentiated adenocarcinomas had more opportunity (84.6%) to be infected with M. hyorhinis than poorly differentiated ones (45.9%)(P < 0.05). Intestinal type of gastric cancers (according to Lauren's classification) got the infection more often than diffused type. About 409 gene expression alterations were detected in 48 000 sites from two gastric cancer cell lines and the expression levels of some genes correlating with cell apoptosis and cell adhesion were down regulated after Mycoplasma hyorhinis infection.

The infection rate of M. hyorhinis is significantly higher in gastric cancer than in other gastric diseases, thus indicating the association between Mycoplasma infection and gastric cancer. Mycoplasma hyorhinis infection influences the gene expression level in gastric cancer cell line MGC803, which indicates that the infection could have something to do with the process of gastric cancer. The question whether M.hyorhinis has oncogenic potential remains to be elucidated.