Microarray analysis of rat mammary carcinogenesis

7,12-Dimethylbenz[a]anthracene (DMBA)-induced rat mammary carcinoma is a well-recognized model, however, the genetic alterations during its carcinogenesis have yet to be determined. We used laser capture microdissection to specifically isolate cells from terminal end buds (TEBs), the origin of carcinoma, at 2 weeks after sesame oil- treatment (control) or DMBA-treatment (DMBA-TEBs), ductal carcinoma in situ (DCIS) and invasive mammary carcinoma (MC). Using an oligonucleotide microarray representing 20600 rat probe sequences, we analyzed gene expression profiles and validated mRNA and protein levels of genes of interest by real-time quantitative PCR, immunohistochemistry and immunofluorescence. The number of differentially expressed genes was smallest in DMBA-TEBs (63), followed by DCIS (798) and MC (981). Only the expression of PEP-19, an anti-apoptic gene, showed significant increases in DMBA-TEBs (4-fold), DCIS (10-fold) and MC (16-fold). MMP-13 expression was increased markedly in DCIS (19-fold) and MC (61-fold) while OPN expression was increased 6-fold in DCIS and 8-fold in MC. MMP-7 expression was increased 4-fold in MC. Nidogen-1; a participant in the assembly of basement membranes, TSP-2; an inhibitor of angiogenesis and COUP-TFI; a transcription repressor showed significant decreases in DCIS (4-, 9-, and 17-fold, respectively) and MC (10-, 37-, and 100-fold). Network analyses with IPA software revealed that the most significant network was centered on Akt groups in DCIS and ERK groups in MC. The present findings provide insights into the molecular changes and suggest the importance of PEP-19 overexpression very early on during mammary carcinogenesis. Keywords: Comparative experiments of sesame oil treatment（control）and 7,12-Dimethylbenz[a]anthracene（DMBA）treatment group. Or comparative experiments of tissue type Experiment：7,12-Dimethylbenz[a]anthracene (DMBA)-induced rat mammary carcinoma is a well-recognized model, however, the genetic alterations during carcinogenesis have yet to be determined. We used laser capture microdissection to specifically isolate the cells from terminal end buds (TEBs), the origin of MC, at 2 weeks after sesame oil-(control) or DMBA-treatment (DMBA-TEBs), ductal carcinoma in situ (DCIS) and invasive mammary carcinoma (MC). At 50 days after birth, inbred Sprague-Dawley female rats were given 1ml sesame oil (control) or 20 mg DMBA (Nacalai tesque, Inc. Kyoto Japan) dissolved in 1ml sesame oil, by gastric intubations. Animals in control group were euthanized after 2 weeks (W) and DMBA-treated group were euthanized after 2 weeks (W), 6W and 8W, respectively. From for 4 sample(control, DMBA-TEBs, DCIS, MC), we performed a hybridization repeatedly, respectively.