Thymidine Labelling Studies in a Transmissible Venereal Tumour of the Dog

Abstract

Summary.-The cell population kinetics of the transmissible venereal tumour of the dog was studied at two different stages of tumour growth using the labelled mitoses technique. At the first stage the tumours were growing with a doubling time of about 4 days; at the second stage their growth rate was limited, probably by an immune reaction on the part of the host, to a doubling time greater than 20 days.Labelling of the tumour cells was found to be extremely heterogeneous throughout the tumour. Mitotic figures, however, were present in well labelled as well as in poorly labelled fields, suggesting that thymidine did not reach all regions of the tumour nodules. The data were therefore analysed assuming that the cells in well labelled areas were representative of the total cell population in the neoplasm. The timing of the cell cycle was found to be similar in the rapidly growing tumours and in those growing more slowly. It is concluded that the slowing of growth was due to a considerable increase in the rate of cell loss as a result of the immune reaction.

Cell proliferation markers in the transplanted canine transmissible venereal tumor

“…Here, the mitotic index was higher in growing phases than in regressive phases of the TVT. This result differs from that presented by Cohen and Steel (1972), who did not succeed in distinguishing both TVT evolution phases through mitotic index. A major stimulus for the evaluation of proliferation indexes is the conviction that it could provide data to support a more accurate procedure with the patient.…”

Mathematical Models of Carcinogenesis and Tumor Growth in an Experimental Rat Colon Adenocarcinoma

“…In solid tumors, reduction in growth fraction and/or increasing ceH loss has been clearly shown to accompany tumor growth (Killmannet al, 1962;Frindelet al, 1967;Hermens and Barendsen, 1969;Clifton and Yatvin, 1970;Griswold et al, 1970;Huemer and Bickert, 1971;McCredie et al, 1971;Cohen and Steel, 1972). In the present experimental colon carcinoma too, preliminary observations on tritiated thymidine incorporation indicate a lower labeling index in large vs. early lesions.…”

Immunology of naturally transmissible tumours

“…24 Instead, following transmission, tumour cells undergo a period of growth followed by stasis and/or regression. Under experimental conditions, approximately 13% of CTVT cells are reported to survive transmission and form a visible tumour, 21 with little cell death for between 1 and 3 months. [24][25][26][27] This is followed by either a period of stasis, where the tumour mass does not increase or decrease; immediate regression of the tumour; or stasis followed by regression.…”