Tasmanian devil facial
tumor disease (
DFTD) and canine
transmissible venereal tumor (CTVT) are highly unusual
cancers capable of being transmitted between animals as an allograft. The concept that these
tumors represent a cancer stem-cell process has never been formally evaluated. For each, evidence of self-renewal is found in the natural history of these
tumors in the wild,
tumor initiation in recipient animals, and serial
transplantation studies. Additional data for stem-cell-specific genes and markers in
DFTD also exist. Although both
tumor types manifest as undifferentiated
cancers, immunocytohistochemistry supports a histiocytic phenotype for CTVT and a neural crest origin, possibly a Schwann-cell phenotype, for
DFTD. In these data, differential expression of lineage markers is seen which may suggest some capacity for differentiation toward a heterogeneous variety of cell types. It is proposed that
DFTD and CTVT may represent and may serve as models of the cancer stem-cell process, but formal investigation is required to clarify this. Appreciation of any such role may act as a stimulus to ongoing research in the pathology of
DFTD and CTVT, including further characterization of their origin and phenotype and possible therapeutic approaches. Additionally, they may provide valuable models for future studies of their analogous human
cancers, including any putative CSC component.