Cross-species comparison of orthologous gene expression in human bladder cancer and carcinogen-induced rodent models

Genes differentially expressed by tumor cells represent promising drug targets for anti-cancer therapy. Such candidate genes need to be validated in appropriate animal models. This study examined the suitability of rodent models of bladder cancer in B6D2F1 mice and Fischer-344 rats to model clinical bladder cancer specimens in humans. Using a global gene expression approach cross-species analysis showed that 13-34% of total genes in the genome were differentially expressed between tumor and normal tissues in each of five datasets from humans, rats, and mice. About 20% of these differentially expressed genes overlapped among species, corresponding to 2.6 to 4.8% of total genes in the genome. Several genes were consistently dysregulated in bladder tumors in both humans and rodents. Notably, CNN1, MYL9, PDLIM3, ITIH5, MYH11, PCP4 and FM05 were found to commonly down-regulated; while T0P2A, CCNB2, KIF20A and RRM2 were up-regulated. These genes are likely to have conserved functions contributing to bladder carcinogenesis. Gene set enrichment analysis detected a number of molecular pathways commonly activated in both humans and rodent bladder cancer. These pathways affect the cell cycle, HIF-1 and MYC expression, and regulation of apoptosis. We also compared expression changes at mRNA and protein levels in the rat model and identified several genes/proteins exhibiting concordant changes in bladder tumors, including ANXA1, ANXA2, CA2, KRT14, LDHA, LGALS4, SERPINA1, KRT18 and LDHB. In general, rodent models of bladder cancer represent the clinical disease to an extent that will allow successful mining of target genes and permit studies on the molecular mechanisms of bladder carcinogenesis

Gene Expression Profiling of Chemically Induced Rat Bladder Tumors

A variety of genetic alterations and gene expression changes are involved in the pathogenesis of bladder tumors. To explore expression changes in 4-hydroxybutyl(butyl)nitrosamine-induced rat bladder tumors, microarray analysis was performed. Analysis yielded 1,138 known genes and 867 expressed sequence tags that were changed when comparing tumors to normal rat epithelia. Altered genes included cell cycle-related genes, EGFR-Ras signaling genes, apoptosis genes, growth factors, and oncogenes. Using the pathway visualization tool GenMAPP, we found that these genes can be grouped along several pathways that control apoptosis, cell cycle, and integrin-mediated cell adhesion. When comparing current data with previous mouse bladder tumor data, we found that > 280 of the same known genes were differentially expressed in both mouse and rat bladder tumors, including cell cycle-related genes, small G proteins, apoptosis genes, oncogenes, tumor-suppressor genes, and growth factors. These results suggest that multiple pathways are involved in rat bladder tumorigenesis, and a common molecular mechanism was found in both rat and mouse bladder tumors

Altered Gene Expression Profile in Mouse Bladder Cancers Induced by Hydroxybutyl(butyl)nitrosamine

A variety of genetic alterations and gene expression changes are involved in the pathogenesis of bladder tumor. To explore these changes, oligonucleotide array analysis was performed on RNA obtained from carcinogen-induced mouse bladder tumors and normal mouse bladder epithelia using Affymetrix (Santa Clara, CA) MGU74Av2 GeneChips. Analysis yielded 1164 known genes that were changed in the tumors. Certain of the upregulated genes included EGFR-Ras signaling genes, transcription factors, cell cycle-related genes, and intracellular signaling cascade genes. However, downregulated genes include mitogen-activated protein kinases, cell cycle checkpoint genes, Rab subfamily genes, Rho subfamily genes, and SH2 and SH3 domains-related genes. These genes are involved in a broad range of different pathways including control of cell proliferation, differentiation, cell cycle, signal transduction, and apoptosis. Using the pathway visualization tool GenMAPP, we found that several genes, including TbR-I, STAT1, Smad1, Smad2, Jun, NFκB, and so on, in the TGF-β signaling pathway and p115 RhoGEF, RhoGDI3, MEKK4A/MEKK4B, PI3KA, and JNK in the G13 signaling pathway were differentially expressed in the tumors. In summary, we have determined the expression profiles of genes differentially expressed during mouse bladder tumorigenesis. Our results suggest that activation of the EGFR-Ras pathway, uncontrolled cell cycle, aberrant transcription factors, and G13 and TGF-β pathways are involved, and the cross-talk between these pathways seems to play important roles in mouse bladder tumorigenesis

Pharmacometabolomic Pathway Response of Effective Anticancer Agents on Different Diets in Rats with Induced Mammary Tumors

Metabolomics is an effective approach to characterize the metabotype which can reflect the influence of genetics, physiological status, and environmental factors such as drug intakes, diet. Diet may change the chemopreventive efficacy of given agents due to the altered physiological status of the subject. Here, metabolomics response to a chemopreventive agent targretin or tamoxifen, in rats with methylnitrosourea-induced tumors on a standard diet (4% fat, CD) or a high fat diet (21% fat, HFD) was evaluated, and found that (1) the metabolome was substantially affected by diet and/or drug treatment; (2) multiple metabolites were identified as potential pharmacodynamic biomarkers related to targretin or tamoxifen regardless of diet and time; and (3) the primary bile acid pathway was significantly affected by targretin treatment in rats on both diets, and the lysolipid pathway was significantly affected by tamoxifen treatment in rats on the high fat diet

Diffusion weighted imaging evaluated the early therapy effect of tamoxifen in an MNU-induced mammary cancer rat model.

To assess the optimal time point of diffusion-weighted imaging (DWI) for early prognosis of breast cancer following tamoxifen therapy using a methylnitrosourea (MNU)-induced ER-positive breast-cancer model.Two groups of Sprague-Dawley rats (n = 15 for group 1; n = 10 for group 2) were used. All animals (50 days old) were intravenously injected with MNU (50 mg/kg body weight) to induce ER-positive mammary tumors. When tumors were approximately 2 cm in diameter, DWI was performed on days 0, 3, and 7, and intratumoral apparent diffusion coefficient (ADC) values were measured. Therapy started on day 0 with tamoxifen (10 mg/kg diet) and continued for 4 weeks for group 1, but only 1 week for group 2, while tumor volume was measured by caliper twice weekly. All animals of group 2 were euthanized on day 7 after imaging, and Ki-67, TUNEL, ERα, and ERβ staining were performed on tumor tissue.DW images of MNU-induced mammary tumors were successfully obtained with minimal motion artifact. For group 1, ADC change for 3 days after therapy initiation (ADC3D) was significantly correlated with tumor-volume change until day 11, but the significant correlation between ADC change for 7 days (ADC7D) and the tumor-volume change was observed until day 18. Similarly, for group 2, either ADC7D or ADC3D was significantly correlated with the tumor-volume change, but the higher significance was observed for ADC7D. Furthermore, ADC7D was significantly correlated with apoptotic (TUNEL stained), proliferative (Ki-67 stained), and ERβ-positive cell densities, but ADC3D was not significantly correlated with any of those.ADC7D might be a more reliable surrogate imaging biomarker than ADC3D to assess effectiveness of tamoxifen therapy for ER-positive breast cancer, which may enable personalized treatment. The significant correlation between ADC7D and ERβ-positive cell density suggests that ERβ may play an important role as a therapeutic indicator of tamoxifen