C. parvum immuntherapy of transplanted rat tumours

C.parvum (Wellcome CN 6134) has been tested for tumour suppression against a range of syngeneically transplanted rat tumours, both carcinogen-induced and of spontaneous origin. Subcutaneous growth was not prevented by distant subcutaneous or intravenous injection of the preparation, although growth rates were sometimes depressed or accelerated. In contrast, C. parvum injected in admixture with tumour cells consistently suppressed their growth and with highly immunogenic tumours induced systemic tumour immunity, C. parvum injected intravenously retarded development of pulmonary tumour deposits, and intrapleural injection suppressed growth of pleural tumours and malignant effusions. Host immunosuppression failed to abrogate the tumour-suppressive effect of locally applied C. parvum, but host macrophage depletion with silica totally abolished the response. These studies indicate that in the rat, tumour suppression is most consistently achieved by regional application of C. parvum, and that this response is more dependent upon local macrophage stimulation than generation of systemic immune responses.     

C. parvum treatment of transplanted rat tumours of spontaneous origin.

C. parvum (Wellcome CN6134) has been examined for suppression of a range of transplanted rat tumours of spontaneous origin. With five tumours (three mammary carcinomas and two fibrosarcomas) growth of comparatively high cell inocula (with respect to the minimum for growth in control rats) was suppressed by admixture with the vaccine. Equivalent dry weights of Glaxo, Pasteur or Connaught BCGs were relatively ineffective. Intralesional injection of C. parvum into three three established tumours (two mammary carcinomas and one fibrosarcoma) retarded development of only one, the mmamary carcinoma Sp4. With three mammary carcinomas and one fibrosarcoma, active specific immune stimulation with vaccines of viable or irradiated cells admixed with C. parvum was again consistently effective only with carcinoma Sp4, and this tumour was also susceptible to intradermal but not intravenous treatment with C. parvum alone.     

Levamisole treatment of local and metastatic growth of transplanted rat tumours.

Levamisole has been examined for its ability to control local growth and pulmonary metastases of transplanted rat tumours. The compound did not suppress subcutaneous growth of 3-methylcholanthrene induced sarcomata when administered systemically in a variety of regimens, or when injected in admixture with tumour cells. In addition, levamisole treatment failed to suppress pulmonary growth of intravenously transferred sarcoma cells or spontaneous pulmonary metastases appearing after surgical removal of a transplanted epithelioma.     

BCG therapy of pleural and peritoneal growth of transplanted rat tumours.

Growth of intrapleurally injected cells of immunogenic methylcholanthrene-induced rat sarcomas was suppressed by intrapleural injection of viable or 1 times 10-6 R radiation-sterilized BCG vaccine. As little as 10 mug moist weight of organisms was effective, and treatment could be given several days before or after tumour challenge. Pleural effusion growth of a moderately immunogenic ascitic hepatoma was also controlled by intrapleurally administered BCG. In contrast, BCG injected intravenously, subcutaneously or intraperitoneally was without influence on pleural tumour growths. Similarly, intraperitoneal growth of these tumours was suppressed only by intraperitoneal injection of BCG. With two other transplanted tumours, a chemically induced mammary carcinoma and a spontaneous sarcoma, both of which lack significant immunogenicity, BCG treatment of pleural and peritoneal growths was less successful and more variable. Nevertheless, these studies indicate the potential of this type of treatment of thoracic and peritoneal tumour deposits for possible clinical application in the treatment of malignant mesothelioma.     

Lack of tumorigenicity of aminopyrine orally administered to B6C3F1 mice

To test the tumorigenic potential of aminopyrine, an antipyretic analgesic, it was administered in drinking water at levels of 0 (control), 0.04 and 0.08% to 50 male and 50 female B6C3F1 mice for 100 weeks, and the mice were subsequently maintained without aminopyrine for a further 4 weeks. The most frequent types of tumor, in both treated and control groups, were hepatocellular tumor in male mice and malignant lymphoma/lymphoid leukemia in female mice. No statistically significant differences were observed in the incidences of these tumors between treated and control groups. The incidences of several other tumors in male and female mice also showed no statistically significant differences between treated and control groups. Therefore, no tumorigenic effect of orally administered aminopyrine in B6C3F1 mice was apparent in the present study.     

Hepatocellular tumorigenicity of butylated hydroxytoluene administered orally to B6C3F1 mice

Butylated hydroxytoluene (BHT), a preservative widely found in food as a food additive, was orally administered at concentrations of 1% and 2% of the diet to B6C3F1 mice for 104 consecutive weeks. Treated animals underwent a 16-week recovery period prior to pathological examination. In male mice administered BHT, the incidence of mice with either a hepatocellular adenoma or a focus of cellular alteration in the liver was increased in a clear dose-response relationship. The incidences of male mice with other tumors and the incidences of female mice with any tumor were not significantly increased as a consequence of BHT administration. The results of this study indicate BHT to be tumorigenic to the liver of the B6C3F1 male mouse.     

Radiation-killed BCG in the treatment of transplanted rat tumours

Growth of syngeneic transplants of methylcholanthrene-induced sarcomas and an aminoazo-dye-induced hepatoma in rats was suppressed when tumour cells were injected in admixture with BCG vaccine containing living organisms, or vaccine sterilized by exposure to 1 to 3 × 10⁶ R γ-irradiation. Rejection of mixed inocula containing viable or radiation-killed BCG induced immunity to further challenge with tumour cells. Also pulmonary tumour growth produced by intravenous injection of sarcoma cells was controlled by intravenous injection of living or radiation-killed BCG. These studies indicate that radiation-sterilized preparations may replace viable vaccine in immuno-therapy, at least where tumour suppression results from contact with BCG. The use of sterilized vaccine in comparable clinical situations would remove any danger of the generalized BCG infection which has recently been reported in patients receiving BCG immunotherapy.     

Methanol extraction residue of BCG in the treatment of transplanted rat tumours.

Subcutaneous growth of immunogenic chemically induced rat sarcomata and a hepatoma was restricted when cells were injected into syngeneic animals in admixture with MER. Rats rejecting mixed inocula were immune to further challenge with the same tumour. Growth of a chemically induced mammary carcinoma which lacks detectable immunogenicity was suppressed when low cell inocula were injected in admixture with MER or intact BCG organisms, although animals were not immune to re-challenge. These studies indicate that clinically MER may be a suitable alternative to BCG for contact suppression of tumour growth or incorporation into tumour cell:adjuvant vaccines for active immunotherapy.     

Accumulation of labelled vitamin B12 in some transplanted tumours

The accumulation of labelled vitamin B₁₂ in four different kinds of transplanted tumour was studied using whole-body autoradiography and impulse counting. The tumours were ⁹⁰Sr-induced soft fibroblastic osteosarcomas, spontaneous mammary carcinomas, Ehrlich ascites and Moloney virus-induced tumours. The ⁹⁰Sr-induced soft sarcoma, which was the most rapidly growing tumour, showed the greatest uptake of radio-B₁₂, the concentration being higher than in any normal tissue. In all tumours the radioactivity was localized to the peripheral, still actively growing parts. It is suggested that a connection exists between growth rate and accumulation of B₁₂ and that B₁₂ is needed for rapid cell multiplication.     

Further observations on the effect of C. parvum and anti-tumour globulin on syngeneically transplanted mouse tumours

The inhibitory effect of an i.v. or i.p. injection of C. parvum on intrastrain transplants of a mammary carcinoma in A/HeJ mice has been confirmed, and it has been shown further that C. parvum inhibits the growth of transplants of sarcomata induced with methylcholanthrene both in this strain (members of which lack the fifth component of complement) and in CBA mice (which are not complement deficient). In experiments with the mammary carcinoma, 2 injections of C. parvum on days + 3 and + 9 were more effective than a single injection on day + 3; injections on days + 3 and + 6, or + 3 and + 12, appeared to be marginally less effective than on days + 3 and + 9, but the difference was not statistically significant.     

Effect of prolactin and bromocriptine on growth of transplanted hormone-dependent mouse mammary tumours

Administration of ovine prolactin alone supported growth of hormone-dependent GR mouse mammary tumours. Growth of hormone-independent tumours was not stimulated. Furthermore, administration of bromocriptine, a compound that inhibits release of prolactin from the pituitary gland, was shown to inhibit the growth of hormone-dependent tumours in animals receiving treatment with progesterone + oestrone. Administration of prolactin or bromocriptine to mice bearing tumours that grew independently of progesterone + oestrone treatment had no influence on tumour growth. We conclude that direct as well as indirect evidence has been found for the involvement of prolactin in the growth of transplanted, hormone-dependent GR mouse mammary tumours.     

Resistance to flow through tissue-isolated transplanted rat tumours located in two different sites.

The perfusion characteristics of the P22 carcinosarcoma were investigated in tissue-isolated tumour preparations in the ovarian and inguinal fat pads of BD9 rats. Tumours were perfused with a physiological buffer of known viscosity and changes in perfusion pressure were recorded at different perfusion rates in an ex vivo system. At perfusion pressures exceeding 30-40 mmHg tumour flow rate was directly proportional to the perfusion pressure in all tumours, indicating a constant resistance to flow. An apparent positive pressure difference across the tumour vasculature of 20-30 mmHg occurred under conditions of zero flow in either site. At low perfusion pressures, the flow resistance increased sharply due to increases in the geometric resistance of the tumours. These findings are in accord with previously published data. Geometric resistance increased with tumour volume in both sites and was approximately five times greater in the inguinal tumours than it was in the ovarian tumours, on a weight to weight basis. The dependence of tumour geometric resistance on perfusion pressure differs from the situation in normal tissues and may provide a means of manipulating the tumour microcirculation to the exclusion of the systemic blood supply. The dependence of geometric resistance on tumour site may partly explain why tumours located in different sites respond differently to various forms of therapy.     

The effect of cotrimoxazole on the absorption of orally administered 6-mercaptopurine in the rat

Summary The effect of cotrimoxazole (CTX) on plasma levels of 6-mercaptopurine (6-MP) was studied in the rat. Animals receiving CTX in conjunction with 6-MP were found to have a marked but non-significant decrease in the area under the plasma time curve as compared with animals receiving 6-MP alone. It is suggested that the bioavailability and thereby, the antileukaemic effect) during maintenance therapy of ALL of 6-MP may be decreased by the co-administration of CTX.