Stimulation of Clonogenic Growth of Tumour Cells and Metastases in the Lungs by Local X-Radiation

Abstract

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

The effect of low-dose pre-operative X-irradiation of implanted mouse mammary carcinomas on local recurrence and metastasis

“…The suggestion is that a first preoperative radiation dose should not be too low. It has been suggested that the anterior surface of the lung would have received more than 22 rad of scattered radiation measured at the centre of the body, and this may lead to the trapping of extra metastases den (Van Brenk et al, 1973). However, this explanation is unlikely because, in another experiment, Sheldon (1974) showed, with tumours also transplanted on the anterior chest wall, that the number of metastases in each lobe of the lungs were simply proportional to the size of each lobe, for both irradiated and control mice.…”

Search for an influence of natural immunity on the lung colony assay of a syngeneic transplanted murine tumour

“…injection with a single-cell suspension of tumour cells (Withers and Milas, 1973;van den Brenk et al, 1973a;Thompson, 1974). One of us (Janik, 1976) has recently confirmed this effect, using the tumour employed in the present experiments.…”

Promotion of Growth of Tumour Cells in Acutely Inflamed Tissues

“…THE PROPORTION of intravenously injected allogeneic tumour cells which survived and formed macrocolonies in the lungs of rats (colony forming efficiency, CFE) is relatively small (less than 1%), but CFE was greatly increased if the lungs of recipients had been treated locally with x-ravs before the tumour cells were injected (van den Brenk, Sharpington and Orton, 1973a;van den Brenk et al, 1973b). In mice, local x-irradiation of the lungs also stimulated CFE of intravenously injected syngeneic tumour cells (Withers and Milas, 1973).…”