CD44v6 in peripheral blood and bone marrow of patients with gastric cancer as micro-metastasis

AIM: To detect the expression of CD44 correlated with the ability of micro-metastasis in peripheral blood and bone marrow of patients with gastric cancer and to deduce its clinical significance. METHODS: Preoperative peripheral blood and bone marrow specimens from 46 patients with gastric cancer and 6 controls were studied by semi-quantitative RT-PCR amplification of CD44v6mRNA. Preoperative and postoperative peripheral blood specimens from 40 patients with gastric cancer and 14 controls were studied by quantitative RT-PCR amplification of CD44v6mRNA in the corresponding period. RESULTS: Semi-quantitative RT-PCR amplification showed that CD44v6mRNA expression of peripheral blood and bone marrow was positive in 39 (84.8%) and 40 (86.9%) of 46 patients with gastric cancer, respectively. In peripheral blood, CD44v6mRNA expression was positive for diffuse type in 30 (93.8%) of 32 patients and for intestinal type in 9 (64.3%) of 14 patients. On the other hand, in bone marrow, CD44v6mRNA expression was positive for diffuse type in 31 (96.9%) of 32 patients and for intestinal type in 10 (71.4%) of 14 patients. There was a significant difference between the diffuse type and intestinal type. Quantitative RT-PCR amplification demonstrated that CD44v6mRNA was not expressed in the peripheral blood of controls and CD44v6mRNA expression was positive for preoperative peripheral blood in 40 patients with gastric cancer, the expression levels being from 4.9 x 10(8) - 3.2 x 10(11) copies/g RNA. The average expression level of CD44v6mRNA in peripheral blood was 3.9 x 10(10) copies/g RNA. The expression levels of CD44v6mRNA in peripheral blood in gastric cancer patients after curative operation increased from 5.5 x 10(6) to 7.6 x 10(9) copies/g RNA and the average level was 2.4 x 10(8) copies/g RNA (Figure 3B) (P = 0.00496). After curative operation, the expression level decreased markedly. CONCLUSION: Semi-quantitative and quantitative RT-PCR amplification for CD44v6mRNA is a sensitive and specific method for the detection of micro-metastasis in peripheral blood and bone marrow, which might be used as an indicator of tumor burden and therapeutic effect.