AIM: To study the differential gene expression profiles of target cells in primary gastric cancer and its metastatic lymph nodes using laser microdissection (LMD) in combi- nation with cDNA microarray. METHODS: Normal gastric tissue samples from 30 healthy individuals, 36 cancer tissue samples from pri- mary gastric carcinoma and lymph node metastasis tissue samples from 58 patients during gastric cancer resection were obtained using LMD in combination with cDNA microarray independently. After P27-based am- plification, aRNA from 36 of 58 patients (group 1) with lymph node metastasis and metastatic tissue specimens from the remaining 22 patients (group 2) were applied to cDNA microarray. Semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) and immunohisto- chemical assay verified the results of microarray in group 2 and further identified genes differentially expressed in the progression of gastric cancer. RESULTS: The expression of 10 genes was up-regulated while the expression of 15 genes was down-regulated in 22 gastric carcinoma samples compared with that of genes in the normal controls. The results were confirmed at the level of mRNA and protein, and suggested that four genes (OPCML, RNASE1, YES1 and ACK1) could play a key role in the tumorigenesis and metastasis of gastric cancer. The expression pattern of 3 genes (OPCML, RNASE1 and YES1) was similar to tumor suppressor genes. For example, the expression level of these genes was the highest in normal gastric epithelium, which was decreased in primary carcinoma, and further decreased in metastatic lymph nodes. On the contrary, the expres-sion pattern of gene ACK1 was similar to that of onco- gene. Four genes were further identified as differentially expressed genes in the majority of the cases in the pro- gression of gastric cancer. CONCLUSION: LMD in combination with cDNA microar- ray provides a unique support foe the identification of early expression profiles of differential genes and the ex- pression pattern of 3 genes (OPCML, RNASE1 and YES1) associated with the progression of gastric cancer. Further study is needed to reveal the molecular mechanism of lymph node metastasis in patients with gastric cancer. AIM: To study the differential gene expression profiles of target cells in primary gastric cancer and its metastatic lymph nodes using laser microdissection (LMD) in combi- nation with cDNA microarray. METHODS: Normal gastric tissue samples from 30 healthy individuals, 36 cancer tissue samples from pri- mary gastric carcinoma and lymph node metastasis tissue samples from 58 patients during gastric cancer resection were obtained using LMD in combination with cDNA microarray independently. After P27-based am- plification, aRNA from 36 of 58 patients (group 1) with lymph node metastasis and metastatic tissue specimens from the remaining 22 patients (group 2) were applied to cDNA microarray. Semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) and immunohisto- chemical assay verified the results of microarray in group 2 and further identified genes differentially expressed in the progression of gastric cancer. RESULTS: The expression of 10 genes was up-regulated while the expression of 15 genes was down-regulated in 22 gastric carcinoma samples compared with that of genes in the normal controls. The results were confirmed at the level of mRNA and protein, and suggested that four genes (OPCML, RNASE1, YES1 and ACK1) The expression pattern of 3 genes (OPCML, RNASE1 and YES1) was similar to tumor suppressor genes. For example, the expression level of these genes was the highest in normal gastric epithelium , which was decreased in primary carcinoma, and further decreased in metastatic lymph nodes. On the contrary, the expres-sion pattern of gene ACK1 was similar to that of onco- gene. Four genes were further identified as the differentially expressed genes in the majority of the cases in the pro-gression of gastric cancer. CONCLUSION: LMD in combination with cDNA microar- ray provides a unique support foe the identification of early expression profiles of differential genes and thFurther study is needed to reveal the molecular mechanism of lymph node metastasis in patients with gastric cancer. E ex-pression pattern of 3 genes (OPCML, RNASE1 and YES1)