Single cell suspensions of two allogeneic tumours (W-256 and Y-P388) injected intravenously produced macrocolonies in the lungs of rats. Colony forming efficiency (CFE, the number of colonies produced by each viable cell injected) was low in 6-week or older rats but was markedly increased by 1000-1500 rad local thoracic irradiation (LTI) given 7-14 days before the tumour cell injection, or by antilymphocytic serum (ALS) but not by sublethal whole body irradiation (WBI). Similarly, LTI increased the incidence of pulmonary metastases produced by a solid tumour growing in the leg muscle. Stimulation of CFE by LTI was a strictly local phenomenon and not due to effects of irradiation on thymus, spleen or other tissues of the rat. LTI failed to increase CFE in immunized rats. It is concluded that (1) LTI stimulates clonogenic growth of tumour cells arrested in the lungs, by causing inflammatory reactions accompanied by regenerative cellular proliferation of lung tissue, which increases the “plating” efficiency of tumour cells, (2) the increase in CFE in lungs is not due to suppression of immunity to tumour growth by LTI. Images Fig. 3

Summary.-Two rapidly growing allogeneic tumours, sublines of Yoshida (Y-P388) and Walker (W-256) injected intravenously in single cell suspensions produced tumour macrocolonies in the lungs of rats within 7 days. Y-P388 produced similar but fewer colonies in the kidneys. Colony forming efficiency (CFE) in lung was high in weanling rats given either sublethal whole body irradiation (WBI) or a single dose of rabbit anti-rat lymphocytic serum (ALS) to suppress immunity. In immunologically intact weanlings CFE was much lower and many 7-day old colonies showed signs of regression. CFE for primary tumour cell challenges decreased rapidly and markedly with increase in age of host during the first 1-2 weeks after weaning. This resistance to growth of a primary challenge in lungs of older rats was not significantly reduced by WBI but was decreased by ALS. CFE of a secondary challenge of tumour cells injected intravenously in rats which had been previously immunized with heavily irradiated (HR) tumour cells was very low; it was not significantly increased by WBI but was moderately increased by ALS. In weanling rats given lethal (900 ra4) WBI, 1 hour before intravenous injection of tumour cells, treatment with bone marrow (BM) cells derived from normal adult donors increased CFE, whereas BM (or spleen) cells from immunized donors decreased CFE. The results suggest that ALS and WBI not only increase tumour CFE by suppressing immunity to tumour growth but also " condition " host tissue (tumour bed) in such a way as to facilitate the survival, " take " and initial replication of grafted tumour cells before the rats recover from the immunosuppressive effects of these treatments.

Summary.-Acute inflammatory reactions were induced in rats by the intravenous injection of cellulose sulphate (CS) or The mechanisms which may be responsible for the nonspecific growth promoting effects of inflammatory reactions induced by various types of tissue injury on tumour induction and growth are discussed.

No abstract

A proportion of W-256 tumour cells injected intravenously into a tail vein of the rat are diverted into venous plexuses en route to the lungs; here tumour cells remain trapped, proliferate and form invasive solid tumours in the pelvis and hindquarters, which cause paraplegia, metastases and death. Also, cells trapped in veins produce tumour nodules distributed along the length of the tail; this effect in markedly enhanced by temporarily arresting the outflow of blood from the tail for a few seconds only immediately after cells are injected. Continous monitoring of the radioactive signal over the lungs after W-256 cells labelled with 125IUDR were injected showed that massaging the tail or intravenously injecting isotonic saline into the tail dislodged cells trapped in veins. In heparinized rats, tail trapping was markedly reduced, although not entirely abolished, and venous trapping in vertebral and pravertebral regions was decreased. The anatomical distribution of growth of the trapped cells in rats closely resembled metastases involving dissemination via the "vertebral venous system" produced by certain cancers in man. Labelled tumour cells trapped in the lungs of untreated mature rats commenced dying rapidly in situ wiht 1-2 h after injection; the majority had disappeared within 24 h, and less than 1% of the injected tumour cells survived to form lung colonies. Experimental evidence is presented which indicates that the lungs play a vital role in rapidly eliminating a high proportion of blood-borne cancer cells in the adult individual. Images Fig. 1 Fig. 2 Fig. 3