Host treatments affecting artificial pulmonary metastases; interpretation of loss of radioactivity labelled cells from lungs

The effect was examined of various host treatments (Corynebacterium parvum injection, immunization, thoracic irradiation, cyclophosphamide injection and anticoagulation) on both lung colony formation and lung clearance of radioactive cells after i.v. injection of tumour cells. The non-immunogenic KHT tumour in C3H/Km mice, and the immunogenic EMT6 tumour in BALB/c/Ka mice were used. For all pretreatments except immunization, the curve loss of radioactivity from the lungs had an initial steep portion representing intravascular death of the tumour cells, followed 1-2 days after tumour-cell injection by a shallow exponential curve which likely represented spontaneous death of tumour cells in the perivascular tissues. Essentially all the injected tumour cells lodged initially in the lungs, and this was unaffected by the different host treatments. Except for specific immunization, cell death in the perivascular tissues was also unaffected by host treatment. However, the survival of the tumour cells during the 24 h after injection was extremely dependent on the particular host pretreatment. The results indicated that host treatments such as C. parvum injection or anticoagulation can markedly affect the number of blood-borne pulmonary metastases, but are only effective if given before the tumour cells arrive in the lung vasculature. (author)