Existence of a stem-cell lineage in an infectious venereal tumor of the dog

Abstract

Recent investigations with rat ascites tumors have revealed the occurrence of a stem-lineage (or -lineages) of tumor cells which are primary contributors to the neoplastic growth, and maintain the genetic pattern of each tumor. The stem-cells are generally characterized by a very pronounced constancy with specific chromosome-number mode and by a particular ideogram which is persistent through from cell to cell by the regular mitotic behavior of the chromosomes during serial transfers. The present paper is to report the data which strongly support the stem-cell concept, by finding in the venereal tumor of a dog the existence of a population of tumor cells that are characterized by a high frequency of occurrence, and by a particular chromosome pattern.
The chromosomes were observed in tumor cells occurring in the body fluid from the surface of the venereal tumor of a female dog with the water-pretreatment and acetic dahlia squash technique.
Out of 146 tumor cells under study the cells containing 60 chromosomes were found at the highest frequency (32%), though frequent variations fall between 57 and 61. The ideogram of the most frequent tumor cells is characterized by the constant existence of 14 V- or J-shaped chromosomes and 46 rod-shaped ones (Figs. 11-16). It is then apparent that the most frequently occurring tumor cells which possess characteristic chromosome-number mode along with a particular ideogram from a stem-cell lineage, the members of which serve as the primary progenitors of this tumor.
The normal somatic chromosomes of the dog were investigated in cells from the lung culture according to the roller tube method. The somatic complement comprises 77 rod-shaped elements and a large V-shaped one, the X-element (Fig. 17). The difference of the chromosome pattern is thus strikingly remarkable between the somatic cell of the dog and the stem-cell of the venereal tumor studied here.
It is interesting to note that the chromosomes of the present tumor show a considerable difference, either in number or in morphology, from those of the dog venereal tumor of similar nature which was studied by Watanabe and Azuma (1956) in Nagasaki.