Detection of cancer cells and gene expression of cytokines in the peritoneal cavity in patients with gastric cancer.

BACKGROUND: The gene expression of the cytokines interleukin-2 (IL-2) and IL-10 in peritoneal washings was examined in relation to the presence of cancer cells in the peritoneal cavity in patients with gastric cancer.

METHODS: Total RNA was extracted from 50-ml peritoneal wash samples from 124 patients (gastric cancer, n = 110; controls, n = 14). Carcinoembrionic antigen (CEA) messenger RNA (mRNA) was used to identify the number of cancer cells in peritoneal wash samples by a real-time reverse transcription-polymerase chain reaction (RT-PCR) method, which method was also used to assay the IL-2 and IL-10 gene expression levels.

RESULTS: In the 14 control samples, CEA mRNA was not detected, while CEA mRNA was detected in 2 of the 51 stage I gastric cancer patients. Thus, the specificity of this method for the detection of cancer cells in peritoneal wash samples was 97% (63/65). The CEA-based real-time RT-PCR method demonstrated greater prognostic impact than the traditional cytological method. IL-2 gene expression in peritoneal wash samples that were CEA mRNA-positive was suppressed compared with that in peritoneal wash samples that were CEA mRNA-negative, while IL-10 gene expression did not differ according to the CEA mRNA findings.

CONCLUSION: The detection of small numbers of cancer cells in peritoneal wash samples from patients with advanced gastric cancer is a good marker for peritoneal metastatic recurrence. In the peritoneal cavity, cancer cells may escape from immune surveillance by controlling the expression of cytokines.