Proteomic and pathway analyses reveal a network of inflammatory genes associated with differences in skin tumor promotion susceptibility in DBA/2 and C57BL/6 mice.

Genetic susceptibility to two-stage skin carcinogenesis is known to vary significantly among different stocks and strains of mice. In an effort to identify specific protein changes or altered signaling pathways associated with skin tumor promotion susceptibility, a proteomic approach was used to examine and identify proteins that were differentially expressed in epidermis between promotion-sensitive DBA/2 and promotion-resistant C57BL/6 mice following treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA). We identified 19 differentially expressed proteins of which 5 were the calcium-binding proteins annexin A1, parvalbumin α, S100A8, S100A9, and S100A11. Further analyses revealed that S100A8 and S100A9 protein levels were also similarly differentially upregulated in epidermis of DBA/2 versus C57BL/6 mice following topical treatment with two other skin tumor promoters, okadaic acid and chrysarobin. Pathway analysis of all 19 identified proteins from the present study suggested that these proteins were components of several networks that included inflammation-associated proteins known to be involved in skin tumor promotion (e.g. TNF-α, NFκB). Follow-up studies revealed that Tnf, Nfkb1, Il22, Il1b, Cxcl1, Cxcl2 and Cxcl5 mRNAs were highly expressed in epidermis of DBA/2 compared with C57BL/6 mice at 24h following treatment with TPA. Furthermore, NFκB (p65) was also highly activated at the same time point (as measured by phosphorylation at ser276) in epidermis of DBA/2 mice compared with C57BL/6 mice. Taken together, the present data suggest that differential expression of genes involved in inflammatory pathways in epidermis may play a key role in genetic differences in susceptibility to skin tumor promotion in DBA/2 and C57BL/6 mice.

Differential expression of multiple anti-apoptotic proteins in epidermis of IGF-1 transgenic mice as revealed by 2-dimensional gel electrophoresis/mass spectrometry analysis.

Overexpression of insulin-like growth factor-1 (IGF-1) has been associated with a number of human tumors, including breast, colon, lung, and prostate cancers. In previous studies, we found that mice overexpressing human IGF-1 in the basal layer of the epidermis (BK5.IGF-1 mice) developed skin tumors following treatment with the skin tumor initiator, 7,12-dimethylbenz[a]anthracene, indicating that IGF-1 can act as a skin tumor promoter. In the present study, we employed a proteomics approach of two-dimensional (2-D) gel electrophoresis and mass spectrometry to profile differentially expressed proteins in skin epidermis between BK5.IGF-1 transgenic and nontransgenic littermates. Two-D gels from each of three transgenic and three age/sex matched wild-type littermates were compared at two different pH ranges. Differentially expressed protein spots were identified by Bio-Rad's PDQuest image analysis, in-gel digested, and analyzed on a MALDI-TOF MS system. A total of 23 proteins were identified as differentially expressed, 17 of them overexpressed in transgenic mice. These proteins included 14-3-3 sigma, galectin-7, an apoptosis-related protein, three heat shock proteins, four calcium binding proteins, three proteases or protease inhibitors, one actin regulatory capping protein, and translation initiation factor 5A. The differential expression of GRP78, alpha enolase, and galectin-7 was verified by 1-D western blot analysis. Two-D western blot analyses of alpha enolase and galectin-7 further revealed that alpha enolase had more than one protein spot dependent on charge. The current data suggest that some of the differentially expressed proteins may play a role in the tumor promoting action of IGF-1 in mouse skin.

Genetic linkage maps of the West African clawed frog Xenopus tropicalis.

Amphibians, and particularly the African clawed frog Xenopus laevis, have been used for more than a century as models of vertebrate embryonic development. However, in many cases, elucidation of developmental functions of specific gene sequences could be severely impeded, because X. laevis is a tetraploid species, with multiple functional copies of many genes of interest. Recent studies have shifted focus to the West African or tropical clawed frog, X. tropicalis, the only known diploid species of the genus Xenopus. Here, we present two preliminary linkage maps, constructed by analysis of joint segregation of amplified fragment length polymorphism (AFLP) markers in a X. tropicalis interstrain hybrid. A total of 53 markers, including 51 AFLP markers and 2 isozyme markers, are presently assigned to 13 multipoint linkage groups on a map of the maternal strain, whereas 9 AFLP markers from the paternal strain are assigned to 3 linkage groups on a separate map. A dense genetic linkage map is essential in mapping new developmental mutants and determining their sequences by positional cloning.