Canine
transmissible venereal tumor (CTVT) is an intriguing
cancer that is transmitted naturally as an allograft by
transplantation of viable
tumor cells from affected to susceptible dogs. At least initially, the
tumor is able to evade the host's immune response; thus, CTVT has potential to provide novel insights into
tumor immunobiology. The nature of CTVT as a "contagious"
cancer, originating from a common ancestral source of
infection, has been demonstrated previously by a series of studies comparing geographically distinct
tumors at the molecular level. While these studies have revealed that apparently unrelated
tumors share a striking degree of karyotypic conservation, technological restraints have limited the ability to investigate the chromosome composition of CTVTs in any detail. We present characterization of a strategically selected panel of CTVT cases using microarray-based comparative genomic hybridization analysis at ~one-megabase resolution. These data show for the first time that the
tumor presents with an extensive range of non-random chromosome copy number aberrations that are distributed widely throughout the dog genome. The majority of abnormalities detected were imbalances of small subchromosomal regions, often involving centromeric and telomeric sequences. All cases also showed the sex chromosome
complement XO. There was remarkable conservation in the cytogenetic profiles of the
tumors analyzed, with only minor variation observed between different cases. These data suggest that the CTVT genome demonstrates a vast degree of both structural and numerical reorganization that is maintained during transmission among the domestic dog population.