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Little is known of the localisation of injected Corynebacterium parvum. We therefore developed a method of radiolabelling this vaccine and determined its distribution in the mouse. Live C. parvum (Wellcome, strain CN 6134) was grown in the presence of 3H-thymidine and subsequently killed by formalin. A high activity, 1-6 x 10(5) cpm/0.1 ml of a 7 mg dry weight/ml concentrated suspension, was obtained. Its biological properties (hepatosplenomegaly and antitumour effects) were similar to those of commercially available vaccine. After intravenous or intraperitoneal injection into normal mice, high activity was recovered in liver and moderate activity in spleen, lungs and small gut. In contrast, after subcutaneous injection, most activity was recorded at the injection site, and little in other tissues. A similar distribution of labelled C. parvum was found in tumour-bearing mice. Only moderate counts were detected in tumour.

The effects of Corynebacterium parvum on the mouse primary Lewis lung carcinoma and its metastases were studied. C. parvum was given at the same time as subcutaneous inoculation of tumour or in combination with surgical excision of the primary after 10 days' growth. When intravenous C. parvum was given at the same time as tumour there was a reduction in the primary tumour growth rate. There was a similar reduction in growth if the drug was given intravenously 7 days after tumour inoculation. Intraperitoneal and subcutaneous administration of C. parvum had no effect on the primary tumour. The number of pulmonary metastases were significantly reduced after intravenous or intraperitoneal C. parvum given at the same time as tumour. When C. parvum and surgery were combined and C. parvum was given not more than 2 days before operation there was only a slight reduction in metastases, but when the injection was given intravenously or intraperitoneally 3-4 days before operation the number of metastases was significantly reduced. Subcutaneous administration of C. parvum had little effect on metastases. There was no difference in the number of metastases in C. parvum-treated mice were killed after 21 or 28 days. C. parvum given on the same day as surgery was more effective if tumour excision was performed before day 10 when the metastases were less well established. It was concluded that in well-defined conditions C. parvum is effective against metastases of the Lewis lung carcinoma.

The murine dose of i.v. C. parvum (466 microgram) was compared with a single, low, human-equivalent dose of 70 microgram and with repeated weekly low doses. All treatments increased the antibody titre against C. parvum (CP). However, repeated doses stimulated a much higher titre than single doses. In all treated animals spleen weight peaked at 2 weeks and then fell. A single low dose caused a 3-fold increase, a single high dose or multiple low doses a 6-fold increase. Liver weight changes followed a similar pattern. Hepatosplenomegaly was prolonged by multiple doses. The effects of these treatments on Lewis tumour metastases were studied. A single high dose and a single low dose on the day of tumour implantation (Day 0) were equally effective at inhibiting pulmonary metastases. Repeated low doses starting on Day 0 were no more effective than a single dose. The effect of CP on survival after primary-tumour excision on Day 10 was observed. Low dose CP on Day 7 doubled the harmonic mean of survival time. Repeated doses were no more effective than a single dose. Low-dose prophylaxis up to 2 weeks before tumour significantly inhibited metastases. However, when repeated low-dose prophylaxis was combined with a single low dose on Day 0, the anti-metastatic effect was abrogated. This neutralization of the anti-metastatic effect of CP given on Day 0 was found to persist after a 13-week treatment-free interval. Possible mechanisms for this phenomenon are discussed.

The effects of Corynebacterium parvum (C. parvum) on Lewis lung tumour metastases have been studied. I.v. and i.p., but not s.c. C. parvum significantly reduced pulmonary metastases. When combined with excision of the primary tumour, C. parvum given not more than 2 days before caused slight reduction of metastases, but when given earlier, it caused significant reduction and some mice were cured. Metastases were increased by silica or cortisone acetate but were unaffected by trypan blue. The antimetastatic action of C. parvum was not altered by these treatments. Thymectomy and irradiation did not affect tumour metastases, or the antimetastatic action of C. parvum, whereas ALS depressed metastasis and abrogated the protective effects of C. parvum. It appears that the inhibitory effects of C. parvum on tumour metastases are mediated through macrophages in concert with a subpopulation of T2 lymphocytes.

The effects of operation (lower-limb amputation) on the growth of the Lewis lung tumour and its metastases were studied. The role of C. parvum in counteracting these effects was investigated. Anaesthesia alone or with amputation did not affect primary tumour growth. C. parvum depressed this growth. Anaesthesia did not affect the number of pulmonary metastases, but amputation caused a significant increase. C. parvum inhibited metastases and completely counteracted the effects of operation on them. Large doses of cortisone acetate significantly increased metastases but small doses had no effect. Experiments with adrenalectomized mice suggested the effects of operation were due to non-specific stress.

Surgical operations depress immune responses. The aim of this study was to observe the effects of operation (amputation) on the growth of the Lewis lung tumour and its metastases and to see if C. parvum counteracted them. Anaesthesia alone, or with amputation, did not affect the growth of the primary tumour but C. parvum depressed it. Anaesthesia did not affect the number of pulmonary metastases but amputation caused significant increase. C. parvum inhibited metastases and completely counteracted the effects of operation. Large amounts of cortisone significantly increased metastases but small doses did not. Experiments in adrenalectomized mice suggested the effects of operation were due to non specific stress.

The effects of Corynebacterium parvum and cortisone acetate (CA) on the primary Lewis lung carcinoma and its pulmonary metastases were investigated. C. parvum given IV either on the same day or 7 days after tumour inoculation, reduced primary tumour growth, while 2.5 mg CA (high-dose) given SC 4 and 11 days after tumour, alone or in combination with C. parvum, administered on day 0, reduced primary tumour growth to the same extent as C. pravum alone. High-dose CA given on days 2 and 6 had no effect on primary tumour growth or the action of C. parvum, administered on day 7, while 0.05 mg CA (low-dose) given on days 4 and 11 did not alter tumour growth or the action of C. parvum given at the same time as tumour. High-dose CA given 4 and 11 days after tumour caused a significant enhancement in metastases. C. parvum given to these mice on the same day as tumour significantly reduced the pulmonary nodules but only to the level found in control, saline-treated mice. In mice given C. parvum alone, metastases were significantly reduced when compared with controls. Similarly, high-dose CA given on days 2 and 6 significantly enhanced metastases, and C. parvum on day 7 reduced their level to that found in control mice. Low-dose CA had no effect on the number of metastases or the antimetastatic action of C. parvum. The relevance of these results to the clinical situation is discussed.

The level of peripheral blood platelets was determined after i.v. injection of Corynebacterium parvum in normal C57BL mice and in those bearing the Lewis lung carcinoma. Twenty minutes after injection of a formalin-killed active strain (CN6134, (CN6134, which inhibited tumour metastases) or a killed inactive strain (CN 5888, which did not inhibit metastases) the number of circulating blood platelets was reduced by 50%. The level of platelets returned to control values by 8 h after the active, and by approximately 3 days after the inactive strain. The active strain alone caused a second and prolonged fall in platelet numbers, from approximately 16 h to 21 days after injection. Heparin given 3 X weekly to these mice restored the platelet count to normal values by 10 days after injection of active-strain C. parvum. The level of platelets in tumour-bearing mice was essentially similar to that in normal mice. Possible causes of the thrombocytopenia and the significance of platelets in metastasis are discussed.