Investigate The Mechanism Of The Occurrence And Development Of Pancreatic Cancer In SD Rats Induced By DMBA

Objective:The incidence of pancreatic cancer increases year by year, and the death rate has been ranked second in gastrointestinal cancer. Early diagnosis of pancreatic cancer is very difficult, simply because the mechanisms of its occurrence and development are not clear. In preliminary studies in our laboratory, we had successfully established the rat model of pancreatic cancer. This in vivo model is similar to the process of human pancreatic cancer. By observing its morphological and histological changes, we provided the latest experimental evidence to understand the occurrence of pancreatic cancer. In this issue, we plan to collect the tissue samples at different time points in the process of inducing rat model of pancreatic cancer. Then we investigate the gene expression profile among those samples in order to further explore the molecular biologic mechanism of the occurrence and development of pancreatic cancer cell and offer new clues for early diagnosis and gene therapy of pancreatic cancer.Method:1. Establish SD rat animal model of pancreatic cancer induced by chemical carcinogen DMBA.2. Gene expression profile was screened in all time points tested of rat model of pancreatic cancer using oligonucleotide microarray (Affymetrix Genechip Rat Expression Set 230).3. Genespring software was applied in functional analysis of differentially expressed genes, according to Gene Ontology (GO) in molecular function and biological process categories. And according to their gene expression patterns, hierarchical cluster analysis and self-organizing map clustering (SOM) were analyzed.4. Microarray raw data were analyzed by using Mann-Kendall trend monotone test of human and rat whole genome were compared in order to get homologous differentially expressed genes of rat and human.5. Fluorescence real-time quantitative PCR and immunohistochemical staining were used to exam levels of mRNA and protein validation of the significance differentially expressed gene to determine the reliability of microarray results.Results:1. Successfully induced the rat models of pancreatic cancer by using 5mg dose DMBA with low non-experimental accident death rate. After 1 month, the incidence of cancer occurrence was 80%(12/15) in DMBA experimental group, accompanied by two cases of high-level Pan IN. After 3 months, the incidence of cancer occurrence was 100%(14/14) in DMBA experimental group, mortality was only 6%(1/15).2. A comprehensive, differential gene expression profile was obtained for normal pancreas, DMBA experimental groups after 7 days,2 weeks,1 month and 3 months. Totally,661 genes group changes in the overall situation.3. According to GO classification, the selected 661 differentially expressed genes involved in different molecular function categories, and participated in many biological processes. According to the similarity of differentially expressed gene expression by using two-way hierarchical clustering analysis, we could completely discriminate the normal pancreas, acute and chronic pancreatitis, Pan IN and early and advanced pancreatic cancer samples.4. There were 11 up-regulated genes (probe) and 142 down-regulated genes (probe) (P <0.05) by Mann-Kendall trend Monotone test. We successfully screened out the homologous genes of rat and human at different time points in the process of rat models of pancreatic cancer. 5. The real-time quantitative PCR and immunohistochemical staining of CXCR7 and UBe2c revealed a similar expression pattern to microarray results.Conclusion:1. Obtaining the different stages of pancreatic cancer tissue samples in rat models made the dynamic study for the molecular biologic mechanism of occurrence and development of pancreatic cancer possible.2. Obtaining differentially expressed genes dynamically and high throughput during the development of pancreatic cancer by application of the expression of rat whole genome microarrays.3. Combined with rat models of pancreatic cancer at different time points and the different pathological state, the global transcriptome profiling shows that occurrence and development of pancreatic cancer is a complicated and multifactorial process and may involve some of all of the following changes:inflammation, chemokines, cell stress response increased and enhanced resistance to oxidative damage, inhibition of tumor cell apoptosis, regulation of proliferation and growth inhibition of the signaling pathways of balance, cell cycle and mitosis of the disorder as well as structural changes in the cytoskeleton, and many other genetic changes. And these changes in pancreatic cancer development and progression of different periods have different characteristic, the results may be closely related to occurrence and development of pancreatic cancer.4. Successfully screening the homologous genes of rat and human was significance for the further study for the molecular biologic mechanism of occurrence and development of pancreatic cancer in human pancreatic cancer cell lines and pancreatic cancer patients.5. Suggesting that CXCR7 and UBe2c may be related to the occurrence and development of pancreatic cancer, further studies of these genes may provide new clues of molecular mechanisms and treatment of pancreatic cancer.