Gene expression profiling of canine osteosarcoma reveals genes associated with short and long survival times

Osteosarcoma (OS) accounts for approximately 80% of all malignant bone tumors in the dog. Tumors are highly metastatic and long-term survival is poor. This study aims to investigate the prognosis associated gene expression profile in primary canine OS. Canine specific cDNA microarray representing 20,313 genes was used to analyze expression profiles in a panel of thirty-two primary osteosarcoma to identify genes associated with survival. The 32 tumours were classified into two groups of prognosis based on survival time (ST). They were defined as short survivors (dogs with poor prognosis that survived less than 6 months) and long survivors (dogs with better prognosis that survived longer than 6 months). Fifty-one genes were found to be differentially expressed, with common up regulation of these genes in the short survivors. The overexpression of these genes in short survivors suggests a possible role for increased proliferation, drug resistance or metastasis. Several deregulated pathways were identified in the present study includes Wnt signaling, Integrin signaling and Chemokine / cytokine signaling which were comparable to the pathway analysis conducted on human OS, adding more value for the dog as an excellent model to study human OS. Our results suggest that a molecular-based method for discrimination of outcome for short survivors and long survivors of canine OS may be useful for future prognostic stratification of dogs at initial diagnosis, where genes and pathways associated with cell cycle/ proliferation, drug resistance and metastasis could be potential targets for therapy that may not just be beneficial for dogs but also for humans. Thirty-two histologically confirmed canine OS with available survival data, that were presented at the University Clinic for Companion Animals in Utrecht from 1996 – 2003 were selected in this study. These dogs were not subjected to any sort of therapy prior to harvesting of the tumor tissue. Tumor samples were harvested under sterile conditions during surgery (amputation / marginal resection / total resection). Samples were snap-frozen in liquid nitrogen and stored in sterile tubes at -70°C. Various clinical and pathological parameters were evaluated retrospectively for the dogs included in this study. Thirty-two tumors were assigned into two groups of prognosis based on survival time (ST). They were defined as short-term survivors (SS; 16 dogs with poor prognosis that survived less than 6 months) and long-term survivors (LS; 16 dogs with better prognosis that survived longer than 6 months). A common reference cRNA pool consisting of equal quanitity of cRNA from all 32 tumors was used to hybridize against each tumor on the array. Equal numbers of samples per tissue group were labelled with Cy3 and Cy5 (dye swap).