Quantitative studies of translymphnodal passage of tumour cells naturally disseminated from a non immunogenic murine squamous carcinoma.

A squamous cell carcinoma of spontaneous orgin in a WHT/Ht mouse was used to study the frequency with which the regional axillary lymph nodes draining subcutaneous or intradermal tumours gave rise to tumours after their isogeneic transplantation as whole nodes. This frequency (similar to 40%) was found not to vary significantly with the size or duration of the tumour drained and not to be increased by coincident infective, traumatic or antigenic stimuli acting at the tumour site or in adjacent tissue. Because tumour growth occurred in only 2/55 (4%) nodes which were left in situ in mice whose tumours were radically excised, it was concluded that tumour forming node transplants reflected a small and limited content (estimated to be about 13) of transnodally passing tumour cells destined to pass on to the blood; separate experiments showed that tumour cells reaching the blood survived for only a few hours. Nodes from tumour-excised mice gave rise to tumours as frequently when autografted as when isografted to mice with no previous expose to the tumour. A review of the finding reported here and of previous quantitative data for this system enabled us to exclude any implication of anti-tumour immunity from our interpretation of the results of the experiments

Failure of preoperative C. parvum vaccine to modify secondary disease following excision of two non-immunogenic murine carcinomas.

Sadler and Castro (1976) reported that a single dose of C. parvum vaccine given i.p. or i.v. to mice 4 days before excision of subcutaneous transplants of Lewis lung carcinoma significantly reduced the incidence of lung metastases in the operated mice. In similarly designed experiments, using 2 different carcinomas of spontaneous origin in our own inbred mouse colonies, we were unable to demonstrate any influence of C. parvum vaccine on the incidence or latent period of secondary disease in operated mice. We discuss possible reasons for our failure to reproduce the findings of Sadler and Castro

Effect of Induced Host Anaemia on the Viability and Radiosensitivity of Murine Malignant Cells in vivo

Within 48 hours of the institution of severe phenylhydrazineinduced anaemia in mice bearing ascites tumours or generalised leukaemia, a substantial proportion of the malignant cells disappeared respectively from the peritoneal cavity or infiltrated liver. The results of radiobiological experiments permitting determination of the proportion of viable leukaemia cells which were severely hypoxic and relatively radioresistant in the livers of leukaemic mice, showed that induction of anaemia was associated with a several hundredfold increase in the proportion of such cells. The proportion of hypoxic cells was greatly reduced when the anaemic leukaemic mice were transfused with packed erythrocytes or allowed to breathe oxygen under high pressure. Similar experi - ments with solid sarcomas indicated that a high proportion of the tumour cells were hypoxic in non-anaemic mice breathing air. The hypoxic fraction was not significantly reduced when tumour-bearing mice were made severely anaemic during growth of the tumour and were later transfused. Thus, the hypoxic cells in leukaemic livers and those in solid tumours are markedly different in their capacity for oxygenation following the induction of relative hyperoxaemia

Facilitation of nodal metastasis from a non-immunogenic murine carcinoma by previous whole-body irradiation of tumour recipients.

Of 193 CBA mice kept under prolonged observation after excision of small intradermal transplants of a non-immunogenic tumour (CBA Carcinoma NT), 27 (14%) presented with local recurrence, 19 (10%) with regional lymphnodal metastasis (RNM) and 72 (37%), with pulmonary metastasis +/- other systemic metastases. When mice were exposed to sublethal whole-body irradiation (WBI) before tumour transplantation, the incidence of RNM rose to approximately 80% and the latent period was reduced from approximately 60 days to approximately 40 days after tumour transplantation. This enhancement of RNM by WBI was undiminished when the interval between WBI and tumour transplantation was increased from 1 to 90 days. An explanation for this effect in terms of immunosuppression by the WBI is unlikely for the following reasons: the tumour was non-immunogenic by standard quantitative tests; the effect persisted long after the expected time for recovery of immune reactivity; and i.v. injection of normal marrow and lymphoid cells after WBI failed to reduce the effect. That the effect was systemic was proved by failure of local pre-irradiation of the tumour bed or regional node to enhance RNM. The effect was not observed when WBI was given 4 days after excision of tumours. These and other experiments failed to indicate the mechanism of the effect of WBI, but its long persistence suggests that it may relate to stored lethal radiation damage in migrating cells of slow turnover tissues

Further studies of the relationship between lymphatic dissemination and lymphnodal metastasis in non-immunogenic murine tumours.

In all 6 different murine tumours of spontaneous origin, a high proportion (22-95%) of the regional lympgh nodes draining small intradermal tumours gave rise to tumours after their isogeneic transplantation as whole nodes. In separate experiments with 4 of these tumours, equivalent tumour-bearing mice had their tumours surgically excised and were observed for the development of regional nodal corresponding frequency of tumour formation by transplanted nodes. After high-dose radiotherapy of intradermal carcinomas, there was a progressive fall in the incidence of positive regional node transplants from 48 to 96 h after irradiation. It is concluded that continual lymphatic dissemination of viable cancer cells is characteristic of malignant tumours, but that there is a relatively small chance of such cells giving rise to nodal metastatic growth. Related studies showed that the ability of a small number of cancer cells to give rise to tumours was very much greater if they were incorporated in a lymph node at transplantation than if they were transplanted directly as a suspension