Cell production in tumour isografts measured using vincristine and Colcemid

Demonstration of vincristine resistance in primary intestinal neoplasms in the rat by the 'post-metaphase index'

A method is described enabling the direct measurement of vincristine resistance in intact tissues in vivo by morphological study. Using the metaphase arresting properties of the drug, counts were made of escaping anaphase and telophase mitotic figures at a range of doses. The proportion of post-metaphase mitotic figures is called the post-metaphase index (PMI). In 95 primary intestinal tumours induced by dimethylhydrazine (DMH) in rats, an increase in resistance to vincristine was shown over normal mucosa (P less than 0.001). The data were analysed by computer modelling and a linear relationship is demonstrated between the logit of the post-metaphase index, and log dose of vincristine. To achieve a PMI of 1% the fitted lines show an enhanced vincristine dose requirement over normal mucosa of 6 times in colonic tumours, and 8 times in small intestinal tumours. Non-neoplastic mucosa from the DMH-treated animals requires an enhanced dose of vincristine of 1.5 times, compared with normal mucosa, to achieve a PMI of 1%. Given current interest in the mechanism of vincristine resistance in cell lines this new approach provides a technique for assessing the resistance of solid tumours, both in vivo and in vitro, and for subsequent experimental manipulation.

Cell kinetics of urethane-induced murine pulmonary adenomas: III. Implications of the disparity between the rates of entry into DNA synthesis and into mitosis

Metaphase arrest by vincristine in urethane-induced murine pulmonary adenomas became linear after an interval of 60 min. The rate of entry into metaphase was 0-191%/h, which was considerably less than the 1%/h for the rate of entry into DNA synthesis obtained previously by double labelling. The duration of prophase plus metaphase was calculated to be 1-7 h. A growth fraction of 9% and a cell-loss factor of 52% were derived. The disparity between rates of entry into DNA synthesis and into metaphase was investigated by microdensitometry on Feulgen-stained squash preparations of tumours of varying ages. Tne DNA profiles showed an increasing frequency of hyperdiploid nuclei with age. Circumstantial evidence for polyploidy was provided by the presence of many binucleate cells in the tumours. By analogy with the liver, these cells may well represent a stage in the development of polyploidy, and the possible relevance of these findings to the neoplastic process is considered.

Growth kinetics of Kaposi's sacroma

This is a study of cell kinetics in nodular and florid (fungating) Kaposi's sarcomas. One or more tumours from 9 patients were examined at the Uganda Cancer Institute. The very variable clinical doubling time was assessed by direct measurements of tumour diameters, and an average obtained. The mitotic count, rate of entry of cells into mitosis and cell cycle time were measured in biopsy material, and use to estimate the potential doubling time. From the difference between the potential and the actual doubling times, the rate of cell loss and the cell loss factor were calculated. The average actual clinical doubling time was slightly, but not significantly, higher for growing nodular tumours than for florid tumours. Some nodular tumours were similar to those reported in the literature for other human malignacies. Kinetic studies of static and regressing human tumours have not been reported previously. The rate of cell production found in this tumour is lower than the values reported in the literature for other malignancies. The calculated mitotic duration is long, but similar to previously reported values. The cell loss factor is high: in the static tumours it is 1.0, and in the regressing tumours greater than 1.0. In regressing tumours, the rate of cell loss was 30% higher than the rate of cell production. These tumours did not differ histologically from nearly florid tumours which were increasing in size. It is postulated that regression is determined by local vascular or mechanical factors, supplemented possibly by delayed hypersensitivity responses in some patients.