Project Title: Significance ofRb inactivation inclinicalbehavior ofosteosarcoma We have achieved a clinically significants tratification of dogs and humans with osteosarcoma, identifying two types of patients with distinct clinical outcome based on tumor intrinsic gene expression profiles. There is reciprocal expression of two gene clusters between tumors with"worse outcome"and tumors with "better outcome", with the latter resembling non-malignant bonecells. The signature includes coordinated over- or underexpression of approximately 300 genes, probably a consequenceof abnonnal function in one or a few regulatory factors.
We have identified several candidate motifs in the 5' and 3 'regions across genes of each cluster, but the most significant transcription factor annotations form otifs of the promoter regions of genes from both clusters were all variants of Rb-E2F-DP-1 complexes. A long with known roles of Rb to tightly regulate expression of cell cycle genes and microenvironment (celladhesion) genes,our results suggest that the mutationalstatus of Rb may uniquely determine tumor behavior, clinical progression,and outcome in patientswith osteosarcoma.
Here, wewill determine:
(1) the significance of Rb-regulated response elements in controlof a prototypical differentially expressed gene,
(2) whether reconstituting Rbactivity restores a "normal" gene expression profile in "worst out come" tumors,and
(3) whether a blating Rb activity creates a "worst outcome" gene expression profile in "better outcome "tumors.
Results from this project will provide a mechanistic link to our clinical profiles and begin to pointout markers that will help direct and design better treatment options for patients with osteosarcoma.