Project Update, March 2012
Osteosarcoma is the most common bone cancer of dogs and, in 2006 a UK Kennel Club/British Small Animal Veterinary Association Purebred Dog Health Survey reported that it was the most common cause of death in Irish Wolfhounds. In September 2008, we were awarded funding by the United States-based Morris Animal Foundation to undertake a study to attempt to locate inherited genetic defects that increase the risk of Irish Wolfhounds developing osteosarcoma.
In collaboration with Dr. Kerstin Lindblad-Toh's group (divided between the University of Uppsala in Sweden and the Broad Institute in the United States), we have analysed 170,000 genetic markers (called 'SNPs') in DNA samples from 103 affected Wolfhounds and 82 unaffected veteran Wolfhounds. This analysis did not identify any SNP that has a statistically significant 'association' with osteosarcoma (that is, a SNP that is present significantly more often in the DNA of Wolfhounds with osteosarcoma than in the DNA of unaffected Wolfhounds). Consequently, we will need to analyse DNA samples from additional affected dogs and unaffected dogs, and continually reanalyse the data until we obtain statistically significant results.
An extremely generous donation of £4,000 made by the Irish Wolfhound Club in June 2011 has enabled us to collect samples from a further 2 Wolfhounds with osteosarcoma and 6 unaffected veteran Wolfhounds. We plan to continue to use the funds to finance sample collection and the isolation of DNA from the samples collected. In addition, we ultimately hope to use the funds to cover at least part of the cost of analysing (referred to as 'genotyping') the additional DNA samples. It costs around £150 to analyse the DNA sample from one dog. However, the minimum number of reagents (called 'chips' - one chip is to used to analyse one DNA sample) that can be purchased is 48, at a total cost of £7,200 (48 x £150). This means that we either have to find £7,200, or find someone else who has dog DNA samples to analyse with whom to share the £7,200 cost. At present we have a total of 7 DNA samples from affected Wolfhounds and 25 DNA samples from unaffected veteran Wolfhounds awaiting analysis, and so we are in discussions with Dr. Lindblad-Toh about splitting the £7,200 cost for analysing a further 48 Wolfhound DNA samples.
Although the comparison of 103 affected Wolfhounds and 82 unaffected Wolfhounds did not identify any genetic marker that has a statistically significant 'association' with osteosarcoma, a second comparison of 28 affected Wolfhounds (aged less than 6 years old) and 82 unaffected veteran Wolfhounds found statistically significant 'associations' between osteosarcoma and SNPs located on two different chromosomes. The motivation for this comparison was that we wondered whether Wolfhounds that developed osteosarcoma earlier than the average 6.3 years (approximately) age of onset may contain genetic risk factors additional to those carried by Wolfhounds that develop osteosarcoma later in life. Although osteosarcoma tends to occur in middle-aged to older dogs, some reports in the scientific literature have reported a 'second peak' between 18 and 24 months of age. The two SNPs that we have identified appear to pinpoint locations on two chromosomes that contain an inherited genetic abnormality that confers an increased risk of developing osteosarcoma. We have provided DNA samples to Dr. Lindblad-Toh's group (who have the necessary funds and personnel required to undertake the work) in order to assist them to attempt to identify the genetic abnormalities in the two chromosomal regions.
Dr. Mike Starkey
Oncology Research Group