This indicates a functional relationship between Kallik reins and the vascularisation related gene, placental growth factor Pgf and the Thrombospondin 2 gene Thbs2 which showed close correlation with these genes. Given the prominent angiogenic phenotype that develops in these pre cancerous skin lesions follow ing MYC activation, it is reasonable to speculate here that Kallikreins and Pgf may be involved. Conclusions Deregulation or over expression of the MYC onco pro tein is a frequent feature of human cancers, which attests to the pleiotropic role that ectopic MYC plays in cellular function. However, oncogenic MYC can also trigger activation of intrinsic tumour suppressor Inhibitors,Modulators,Libraries pro grams such as p19Arf p53, which serve to limit propaga tion of such harmful cells by inducing growth arrest or apoptosis.

While much is known about the mechanisms of MYC functions, the pathways responsible Inhibitors,Modulators,Libraries for deciding the ultimate fate of the cell between life and death in vivo are not yet clear. The decision for a cell to become apoptotic depends on the complex interactions of many pro and anti apoptotic factors. Different tissues may exhibit vary ing levels of these factors ultimately Cilengitide determining the fate of a cell. However, tissue specific environmental charac teristics can also affect the interaction between these factors, having a decisive effect on cell fate. The MYC ERTAM transgenic mouse model allows controlled over expression of MYC in distinct adult tissues, SBK and pancreatic b cells, enabling tracking of early changes downstream of aberrant MYC activity.

In this study, high throughput transcriptional profiling was used to identify transcriptional events that may provide clues to explain the disparity in the phenotypic response to MYC activation in SBK and pancreatic b cells. Whilst expression of genes relating to multiple cellular functions is common to both tissues, expression of genes involved in Inhibitors,Modulators,Libraries DNA damage and repli cation is enriched to b cells. Consistent with early increased expression of Ki67 in b cells, key G1 S phase genes showed early changes in expression, whilst G2 M phase genes showed changes at later time points. Down regulation of the cyclin dependent kinase inhibitor Cdkn1b gene in b cells was evident as previously shown in other cell types. The CDKI Cdkn2c, which inhibits Cdk4 and Cdk6, was also down regulated, Inhibitors,Modulators,Libraries consistent with G1 S phase transi tion.

The short time period over which these changes were seen supports the idea that MYC induced cell cycle progression occurs through direct activation of key cell cycle genes such as Ccnd1, Ccnd2 and Ccne2. In SBK, although there were changes in cell cycle related genes, the response was much less prominent in comparison with b cells. Gene expression changes included up regulation of Krt6a, Pcna, Ccnd3, Cdk4, and the key G1 S phase cyclin gene Ccnd2, accompa nied by significant down regulation of the CDKI gene Cdkn1b throughout the time course.