Figure 3

Algorithm depicting the selection process for dog specific osteosarcoma genes using a fold-expression methodology. In order to define a list of dog specific osteosarcoma genes that are variably expressed in human osteosarcoma, probe sets with matching gene names or symbols across both species were evaluated (14,391 probe sets). An initial list of dog osteosarcoma defining genes was generated by identifying those probe sets with the highest fold expression differentials between the canine tumors and their normal tissues and present expression in the human tumors and their normal tissues (dog: > 8-fold up-regulation in tumors versus normal; human: <2-fold upregulation in tumors versus normal). This yielded 27 probe sets, representing 15 unique genes. Those genes that also had representative probe sets upregulated in both dog and man (> 8 fold expression) were then excluded, leaving 10 genes. This was further filtered by retaining only those genes with consistent expression across all their Affymetrix probe sets; using these stringent criteria 4 dog-like specific osteosarcoma genes were defined.