IDENTIFICATION OF DIFFERENTIAL GENES IN OVARIAN CANCER USING REPRESENTATIONAL DIFFERENCE ANALYSIS OF cDNA

Objoctive To identify differential genes between normal ovarian epithelium tissue and ovarian epithelial cancer using representational difference analysis of cDNA （cDNA-RDA）. Methods cDNA-RDA was performed to identify the differentially expressed sequences between cDNAs from cancer tissue and cDNAs from normal ovarian tissue in the same patient who was in the early stage of ovarian serous cystadenocarcinoma. These differentially expressed fragments were cloned and analyzed, then sequenced and compared with known genes. Results Three differentially cxpressed cDNA fragments were isolated using cDNA from normal ovarian tissue as tester and cDNA from cancer tissue as driver amplicon by cDNA-RDA. DP Ⅲ- 1 and DP Ⅲ-2 cDNA clone showed significant homology to the cDNA of alpha actin gene; DPⅢ-3 cDNA clone showed significant homology to the cDNA oftransgelin gene. Conclusion cDNA-RDA can bc used to sensitively identify the differentially expressed genes in ovarian serous cystadenocarcinoma. Ovarian serous cystadenocarcinoma involves alteration of multiple genes.

cDNA representational difference analysis of differentially expressed cDNA sequences in human nasopharyngeal carcinoma

Objective To search differentially expressed sequences correlated with pathogenesis of human nasopharyngeal carcinoma (NPC), including the candidates of tumor suppressor genes Methods Representational difference analysis (RDA) was performed to isolate differentially expressed sequences between cDNA from normal human primary cultures of nasopharyngeal epithelial cells and cDNA from NPC cell line HNE1 The source of differentially expressed products were proved by Southern blot, Northern blot and in situ hybridization The fragments were cloned with pGEM T easy kit and sequenced by the chain termination reaction Results Four differentially expressed cDNA fragments were isolated in the fourth subtractive hybridization using cDNA from normal human nasopharyngeal epithelial cells as tester amplicon and cDNA from NPC cell line HNE1 as driver amplicon by cDNA RDA These differential cDNA fragments revealed that they really came from the tester amplicon and were not expressed or down regulated in the NPC HNE1 cells Some of the genes were expressed only in human nasopharyngeal epithelial cells but deleted or down regulated in the biopsies of NPC Of these obtained clones, some were the sequences of the human known genes including house keeping genes, the others represented novel gene sequences Conclusion The differentially expressed products including the candidates of tumor suppressor genes may be associated with the initiation of the NPC

ANALYSIS OF Lyl1 EXPRESSION AS A FREQUENT PARTNER OF LMO2 IN T-CELL LEUKEMOGENESIS IN HUMAN

Objective： To identify aberrant gene expression in primary human T-cell acute lymphoblastic leukemia （T-ALL） and to evaluate the differently expressed level of Lyll and LMO2 genes in human LMO2 positive/TALl negative T-ALL tumors. Methods： Three methods, representational difference analysis （RDA） of cDNA, cDNA microarrays and RT-PCR were used to detect if Lyll and LMO2 genes were differently expressed in human LMO2 positive/tall negative T-ALL tumors. Results： The results of cDNA RDA and cDNA array shown that Lyll and LMO2 genes are differently expressed in human T-cell tumors. The result of RT-PCR also shown Lyll and LMO2 are high expressed in human T-cell tumors and very low level or no expressed in normal group. Conclusion： We have found that cDNA RDA and cDNA microarray can be successfully used to identify aberrant gene expression in T-ALL cells. In the study described in this manuscript we found that Lyll and LMO2 are aberrantly expressed in human T-ALL LMO2 positive/TALl negative T-ALL tumors.

Metastatic suppressor genes inactivated by aberrant methylation in gastric cancer

AIM: To screen out the differentially methylated DNA sequences between gastric primary tumor and metastatic lymph nodes, test the methylation difference of gene PTPRG between primary gastric tumor and metastatic lymph nodes, and test the regulatory function of 5-aza- 2-deoxycytidine which is an agent with suppression on methylation and the level of methylation in gastric cancer cell line. METHODS: Methylated DNA sequences in genome were enriched with methylated CpG islands amplification (MCA) to undergo representational difference analysis (RDA), with MCA production of metastatic lymph nodes as tester and that of primary tumor as driver. The obtained differentially methylated fragments were cloned and sequenced to acquire the base sequence, which was analyzed with bioinformatics. With methylation-specific PCR (MSP) and RT-PCR, methylation difference of gene PTPRG was detected between primary tumor and metastatic lymph nodes in 36 cases of gastric cancer. Methylation of gene PTPRG and its regulated expression were observed in gastric cancer cell line before and after being treated with methylation-suppressive agent. RESULTS: Nineteen differentially methylated sequences were obtained and located at 5' end, exons, introns and 3' end, in which KL59 was observed to be located at 9p21 as the first exon of gene p16 and KL22 to be located at promoter region of PRPRG . KL22, as the probes, was hybridized with driver, tester and 3-round RDA products respectively with all positive signals except with the driver. Significant difference was observed in both methylation rate of gene PTPRG and PTPRG mRNA expression rate between primary tumor and metastatic lymph nodes. Demethylation of gene PTPRG, with recovered expression of PTPRG mRNA, was observed after gastric cancer cell line being treated with methylation-suppressive agent. CONCLUSION: Difference exists in DNA methylation between primary tumor and metastatic lymph nodes of gastric cancer, with MCA-RDA as one of the good analytical methods. Significant difference exists in methylation of gene PTPRG between primary tumor and metastatic lymph nodes of gastric cancer. Methylation level in gastric cancer cell line can be decreased by 5-aza-2'-deoxycytidine, which is the methylation- suppressive agent, with PTPRG expression being recovered.