Embryonic chick epidermis, if cultured for 4 days on a TH millipore filter overlying certain malignant dermal fibroblasts, shows abnormalities ranging from complete degeneration to hypertrophy and abnormal differentiation. The effect of the tumour cells is prevented if the thickness of the filter is doubled, to 50 μm., but not if a 25 μm.-thick membrane is coated with a thin collagen gel. When a semipermeable membrane is interposed between the cells and the epidermis, the latter does not degenerate, but keratinizes without showing the usual stages of differentiation. The malignant cells sometimes cause hypertrophy of the epidermis when cultured beneath the dermis of intact skin, but have no effect when grown on the peridermal surface of this tissue or of isolated epidermis. Freeze- or heat-killed dermal cells, whether normal or malignant, provide an unsuitable substratum for epidermal survival, possibly due to adsorption of intracellular constituents on to their surfaces. It is suggested that the malignant fibroblasts examined produce at least two substances having an effect on epidermis: one of small molecular size affecting differentiation, and a toxic macromolecule. A growth-promoting substance may also be produced by the cells of one subline. ImagesFigs. 9-12Figs. 1-4Figs. 5-8

The 1 hour thymidine labeling indices have been determined for 8 hepatomas which have growth rates which vary by a factor of 14. The indices for these tumors vary only by a factor of 4. Little correlation was found. Preliminary results have been obtained on the kinetics of cell proliferation of the rapidly growing Hepatoma H-35tc2. The tumor transfer time is 0.7 months and the growth rate is 7.0 cm. per month. The calculated values for times in different phases of the cell cycle for H-35tc2, assuming a log normal distribution for phase duration, were as follows: Tg1 (Gap I)—11.0 hours; Ts (DNA synthetic period)—6.6 hours; Tg2 (Gap II)—4.2 hours; Tm (mitotic time)—0.4 hours. Therefore, the total time, Tc, for one cell cycle was calculated to be 22.2 hours. The potential doubling time was calculated to be 43 hours. The GF (growth fraction) was estimated to be 53 per cent which would suggest that approximately one-half the total cell population is nonproliferating.

Ehrlich ascites cells or another strain derived from a spontaneous mouse mammary carcinoma (DiVita's ascites cells) were incubated in vitro at 37° C. at cell concentrations of 1-2 × 107 cells/ml. with 10-4M Synkavit in Spinner-medium under various conditions. The cells were then inoculated under standard conditions into mice, and the growth of ascites tumour was determined. On this basis, Synkavit has been shown to retard the growth of ascites tumour provided that the cells were incubated in vitro at pH 7.4 for 30 minutes. This retardation of tumour growth was not dependent on the presence of glucose in the incubation medium and could be observed in the presence of about 5% ascitic fluid. However, the retardation appeared to be considerably less marked (though readily detectable) when the incubation with Synkavit was performed anaerobically. The retardation of tumour growth by Synkavit was abolished completely by simultaneous incubation with excess ATP or partially by equimolar ATP. Simultaneous incubation with excess ADP also abolished the retardation by Synkavit of the growth of tumour. Moreover, ATP addition to the medium at a later period appeared to be partially successful in abolishing the Synkavit effect on tumour growth. The mechanism by which ATP reduced the growth-inhibitory effect of Synkavit has been partially clarified by investigating the effect of ATP on the incorporation of a tritiated derivative of Synkavit, TRK 219. The results show that in Ehrlich ascites cells, simultaneous incubation in Spinner-medium with excess, or equimolar, ATP reduced the incorporation of labelled metabolites of Synkavit by 78% or 14% respectively. On the other hand, in a continuous cell line of human epithelial cells (HEp/2), excess ATP reduced the incorporation of metabolites of labelled Synkavit very slightly. These results have been discussed in the light of other evidence to consider the mechanism whereby ATP reduced the growth-inhibitory effects of Synkavit.

Activities of glucose-6-phosphatase, fructose 1,6-diphosphatase, ornithine transcarbamylase, arginase and xanthine oxidase were measured in thioacetamide induced primary hepatoma and its tumour cell suspension. It was observed that the percentage decrease in the activities of all the enzymes in tumour cell suspension was far more than that observed in tumour tissue. However, in these studies no qualitative difference was observed between the parenchymal cells and the tumour cells. ImagesFig. 1Fig. 2

Histochemical studies on the cell surface and intercellular matrix of normal cervical epithelium, and squamous cell carcinomata have shown the mucosubstances present may be symbolized by the descriptive formula: C(G) mucosubstance; B 3.5; A 2.5 (0.6m MgCl2); T; S. This indicates that sulphate groups are absent and that the intercellular matrix and cell coat are rich in hyaluronic and sialic acids or closely related compounds. These may be important in masking the antigenic expression of the tumour cells. We have not been able to detect any alteration in the mucosubstances at 7 days following radium treatment. ImagesFigs. 1-3

The plausibilities of two hypotheses explaining the increased cancer incidence rate in old age caused by a constant dose of carcinogen were compared using a mouse skin painting experiment in which two groups of mice started treatment at different ages. It was shown that the hypothesis of the increased rate being caused simply by increased vulnerability of old animals was not as plausible as the alternative hypothesis of the carcinogen acting to some extent cumulatively.

The growth of a CBA mammary adenocarcinoma has been studied following transplantation to syngeneic and allogeneic recipients, with particular reference to the susceptibilities of the primary and secondary responses elicited by the tumour allografts, to impairment by whole-body X-irradiation and by treatment with rabbit-anti-mouse lymphocyte serum. In syngeneic recipients, the diameter of tumour implants increases linearly with time and there is no difference in the growth curves in females and in males. Later tumour generations grow faster than earlier generations. In allogeneic recipients, there is a relationship between the tumour diameter on day 21 (T) and the dose of X-irradiation (D) administered before implantation: T = 0.028 D - 9.17 for early tumour generations (SMT4) but this is obscured for later generations (SMT21). The primary response to tumour allografts was radiosensitive whereas the secondary response was radioresistant. This radioresistance of the secondary response persisted for at least 5 months after primary sensitization. Unlike whole-body X-irradiation, treatment with rabbit-anti-mouse lymphocyte serum suppresses both the primary and secondary responses to tumour allografts. The possibility is considered that after exposure to antigenic stimulation, an immunologically reactive cell population is formed which is radioresistant but sensitive to ALS, unlike the precursor cells from which this population is derived, which are radiosensitive and sensitive to ALS. ImagesFig. 2

Medication with L-thyroxine or methylthiouracil of castrate rats painted weekly 5, 10, 20 or 40 times with DMBA does not alter the order of thresholds for carcinogenesis which increases from that for cervico-vaginal epitheliomas via squamous celled and basal celled vulval tumours to cervicovaginal sarcomas. Methylthiouracil lowers the threshold for basal celled vulval neoplasms. Sarcomas reach a peak of 25% with 20 doses of DMBA in non-medicated rats, but rise to 90% and at a faster rate in animals given either of the thyroactive drugs with further carcinogenic treatment. The optimal dose phenomenon for cervico-vaginal epitheliomas, i.e. a significant fall with continued painting from a peak reached by 5 to 20 doses of DMBA, is not affected by medication with methylthiouracil or L-thyroxine. Thyroactive compounds accelerate the formation of squamous celled vulval tumours which reach a maximum with 20 DMBA paintings; the total incidence as well as the proportion of carcinomas to papillomas falls with further treatment. Methylthiouracil promotes formation of basal celled vulval tumours at low dose levels, but inhibits it at the highest. In medicated as in non-medicated rats the induction of basal celled tumours of the vulva follows an optimum dose pattern. The optimal dose phenomenon and the effect of thyroactive compounds on the tissue-specific sensitivity to carcinogens are discussed. ImagesFigs. 1-2Figs. 3-5

In a previous paper, the exact conditions under which the radioactive drug 2-methyl-6,7-ditritio-1,4-naphthaquinol bis disodium phosphate could be selectively incorporated into HEp/2 cells were reported. This work has now been extended and suggests that the selective property associated with two human tumour cell lines established in culture, HEp/2 and HeLa, and two forms of mouse ascites tumour cells propagated in vivo, is a metabolic conversion of the drug (priming stage) to a form which can probably be freely incorporated by all cell types. It is suggested that the observed variations in uptake of label with changes in pH, cell concentration and the inorganic phosphate concentration of the medium indicate that the “priming” stage is critically dependent on the conditions of the experiment. Work with the non-radioactive analogue, Synkavit, indicates that under conditions where the drug is incorporated selectively into cells, incubations in excess of 20 minutes cause a large percentage of the population to lose its reproductive integrity. ImagesFig. 1Figs. 3-4

Analysis of 4500 cases of malignancy encountered in a general hospital in Western India showed that: (1) parts of buccopharynx were the site involved in nearly 25 per cent of these cases. In women the incidence of buccopharyngeal carcinoma was less than in men but was not insignificant (nearly 5 per cent of all malignancies found in women); (2) the cervix was the next frequent site involved accounting for 22 per cent of the total and 80 per cent of the female cancer; (3) cancer of breast was not less common (5 per cent of the total and 12 per cent of the female cancer); (4) oesophageal cancer was far more common than malignant neoplastic lesions of the other parts of the gastrointestinal tract (two-thirds of all cases being found in the oesophagus); (5) carcinoma of skin was not a common lesion. High frequency of the types of cancer mentioned in the first two paragraphs is a “ommon facto” of many such reports from India. On the other hand, reported incidences of the types mentioned in the paragraphs number (3), (4) and (5) show wide variations in different parts of the country.