In vivo transfer of antitumor activity by peritoneal exudate cells from mice treated with Corynebacterium parvum: reduced effect in irradiated recipients

Immunomodulation by propionibacteria

The ability of bacteria and bacterial products to modulate the immune response to unrelated antigens is well documented. Propionibacteria are amongst the most potent immunomodulators stimulating cell populations involved in nonspecific resistance. Generally, the activated immune system provides protection from infectious pathogens and malignancies via mechanisms of recognition and elimination. Accordingly, administration of propionibacteria could be shown to be of benefit in the treatment of neoplastic and infectious diseases. Thus, it can be recommended for further clinical investigations.

The proportion of stem cells in murine tumors

Considerable evidence suggests that tumors contain only a minority of cells which are capable of regrowing the tumor (ie. tumor stem cells). Since all tumor stem cells must be killed if treatment is to be successful, the number of stem cells in a tumor can be expected to be an important determinant of curability. We have attempted to examine the proportion of stem cells in a variety of murine tumors by making measurements of three different parameters which might be expected to be related to stem cell content: (a) the radiation dose required to control the tumor (TCD50); (b) the number of cells required to transplant the tumor (TD50) and (c) the in vitro plating efficiency. An inverse correlation has been demonstrated between measured TCD50 and TD50 values for two independent groups of murine tumors of varying histopathological type. An inverse correlation was also obtained between the TD50 value and in vitro plating efficiency for a group of spontaneous murine mammary tumors. These correlations most likely reflect underlying differences in the stem cell content of the tumors, and indicate that there is a wide range (2-3 orders of magnitude) of stem cell proportions in different murine tumors, even those which have been transplanted a number of times.

Effect of the radiosensitizer misonidazole and the radioprotector diethyldithiocarbamate on spontaneous metastasis formation of murine tumors

The effect of treatment with the hypoxic cell radiosensitizer misonidazole (MISO) and the radioprotector diethyldithiocarbamate (DDC) on the formation of spontaneous lung metastases of four different spontaneously metastasizing murine tumors was investigated. The tumors were mammary carcinoma MCA-K, hepatocarcinoma HCA-1, and sarcomas SA-4020 and SA-NH. Multiple daily treatments with MISO significantly enhanced the incidence of metastases only in MCA-K. Because only MCA-K, but not the three remaining tumors, is immunogenic, the treatment with MISO may be associated with the promotion of metastasis primarily in the immunogenic tumors. Treatment of mice with DDC had no influence on metastatic spread. However, when given prior to 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), DDC reduced BCNU-induced enhancement of HCA-1 metastases.

Metastatic properties of murine sarcomas and carcinomas. I. Positive correlation with lung colonization and lack of correlation with s.c. tumor take

The spontaneous metastatic properties of six sarcomas and seven carcinomas syngeneic to C3Hf/Kam mice were investigated and the correlation between spontaneous metastasis, the lung colony forming efficiency (LCFE) of i.v. injected tumor cells, and s.c. tumor take was determined. The incidence and number of spontaneous metastases in the lung were determined in mice that had primary tumors in the leg removed 17 to 120 days earlier, depending on tumor type. There was a significant positive correlation between spontaneous metastasis and LCFE when all 13 tumors were compared, but the significance was lost when carcinomas and sarcomas were considered separately. No significant correlation between spontaneous metastasis and the s.c. tumor take was observed. Also, no correlation was found between LCFE and the s.c. tumor take of carcinomas, but there was a strong inverse relationship between these two properties of sarcomas. The number of cells shed from primary tumors was estimated and found to be more extensive in tumors with higher metastatic properties. Thus, in general, highly metastatic tumors were characterized by a high LCFE and a significant cell shedding. Furthermore, LCFE was greatly increased by treatment of animals with cyclophosphamide and by admixing heavily irradiated tumor cells to viable cells, implying that local environmental factors are important in determining the establishment of tumor cell clonogens into metastasis.

Effect of tumor type, size, and endpoint on tumor radioprotection by WR-2721

Experiments are reported showing that the degree of tumor radioprotection afforded by WR-2721 varies with the type of tumor and assay endpoint, and that for a given tumor system, microaggregates are protected better than larger cell masses. The tumors used were a methylcholanthrene-induced fibrosarcoma (FSa), and two tumors of spontaneous origin, another fibrosarcoma (NFSa), and a mammary carcinoma (MCa-4), all syngeneic to C3Hf/Kam mice. WR-2721 was given in a dose of 400 mg/kg 30 minutes before irradiation in all experiments. In TCD50 assays, WR-2721 protected 5 mm diameter and impalpable 3 day-old transplants of 5 X 10(5) FSa cells growing in the leg by factors of 1.11 and 1.13, respectively. Using the tumor latency endpoint, 3 day-old s.c. transplants of 10(3) FSa in the abdominal wall were protected by a factor of 1.27, a degree of protection similar to that reported earlier for sterilization of lung micrometastases of the same tumor. MCa-4 tumors growing in the leg were protected better than FSa in TCD50 assays with protection factors of 1.3 for 4 day-old transplants, 1.24 for 5 mm tumors, and 1.23 for 8 mm tumors. MCa-4 tumors recurrent after irradiation as 4 day-old transplants grew more rapidly in mice that had received WR-2721, and this was shown to be most likely due to protection by the drug against expression of the tumor bed effect. Using the lung micrometastases assay, NFSa was protected by a factor of 1.22. This variability in protection with different tumor types, sizes, and assay endpoints is discussed in terms of drug delivery and uptake, and also in relation to the influence of tumor hypoxia on the radioprotective ability of WR-2721.

Activation of macrophage function by intraperitoneal administration of the streptococcal antitumor agent OK-432

Motility, adhesiveness, IL1 production, and inhibition of tumor cell growth in vitro were examined in murine peritoneal macrophages obtained after intraperitoneal injection of a streptococcal preparation OK-432, heat-inactivated OK-432 (HI-OK-432), and thioglycollate medium (TG). By varying the interval between intraperitoneal injection of OK-432 and the harvest of peritoneal macrophages, it was found that OK-432 induced a time-dependent multi-step alteration of these properties: step I increased motility on day 1: step II increased adhesiveness on day 2; and step II increased inhibition of tumor cell growth and IL1 production. During step III, the peritoneal macrophage population, including Ia-bearing cells, increased dramatically in the peritoneal cavities of OK-432-treated mice. In contrast, injection of either HI-OK-432 or TG, which lack antitumor activity in vivo, initiated steps I and II, but not step III. The Ia-bearing macrophages induced by OK-432 showed high ability of IL1 production, but low growth inhibitory activity against tumor cells. Based on these results, OK-432 seems to be performing a dual function: eliciting a new population of macrophages to the site of injection (heat stable function), and inducing two different populations of antitumor macrophages and Ia-bearing macrophages (heat unstable function).

Studies on the antitumor activities of pyrimidinone-interferon inducers. Part 2. Potentiation of antitumor resistance mechanisms

In continuation of studies on antitumor activities of pyrimidinone interferon inducers, we report here that 2-amino-5-bromo-6-mF-phenyl-4(3H)-pyrimidinone (ABmFPP) is similarly effective to 2-amino-5-bromo-6-phenyl-4-pyrimidinone (ABPP) in its ability to reduce the number of metastatic nodules of a spontaneous fibrosarcoma (NFSa) and a spontaneous mammary carcinoma (MCa-K) in the lungs of C3Hf/Kam mice. Both compounds were more effective when given to mice prior to, rather than after, intravenous transplantation of tumor cells. In studies on the mechanism of the antitumor activity of pyrimidinones, 2-amino-5-iodo-6-phenyl-4-pyrimidinone (AIPP) was used in addition to ABPP and ABmFPP. These agents were capable of activating peritoneal macrophages that thus became capable of lysing in vitro 3T12 transformed cells but not syngeneic BALB/c embryo fibroblasts. Also, these agents were capable of augmenting significantly the natural killer (NK) cell activity in the spleen of C3Hf/Kam mice. Spleen cells from treated mice admixed to NFSa cells inhibited in vivo tumor take of these cells when the admixture was injected subcutaneously. Pyrimidinones were also effective against the development of NFSa nodules in the lungs of T-cell deficient mice implying that the presence of T-cells is not a prerequisite for the induction of antitumor activity by these agents. A further observation was that pyrimidinone compounds reduced the metastasis formation enhancing effect of cyclophosphamide. Therefore, pyrimidinone interferon inducers exhibit an appreciable antimetastatic activity mediated through antitumor resistance mechanisms involving activation of macrophages and stimulation of NK-cells.

Differential sensitivity of two murine leukaemia sublines to cytolysis by Corynebacterium parvum-activated macrophages

We observed the growth of 2 sublines of leukaemia L1210 in histocompatible DBA2 mice given 10(3) cells i.p. and studied the protective effect of Corynebacterium parvum (CP). The growth of subline L1210-M was unaffected by pretreatment with CP or admixture with 10(5) peritoneal cells (PC) from CP-treated mice. In contrast, the growth of subline L1210-C was inhibited; CP pretreatment increased the proportion of long-term survivors (70% vs 20%) and admixture with CP-PC prolonged the survival time (59 days vs 49 days; P less than 0.05). In vitro experiments indicated that Sublines M and C were equally sensitive to cytostasis by CP-PC, as measured in a terminal labelling assay (greater than 90% inhibition of proliferation). However, subline C was much more sensitive to cytolysis (18h 125IUDR-release assay) by CP-PC; percentage specific release from L1210-C was at least 90%, whilst from L1210-M it was generally less than 25%. The differential susceptibility of the 2 sublines to cytolytic PC was maintained through 75 passages in culture. The effector cells were considered to be macrophages, because they were adherent, phagocytic, and sensitive to silica. Cytolysis was unrelated to endotoxin contamination, because it was not inhibited by polymyxin B, and was inhibited by pre-incubating PC in culture medium for 24 or 48 h before adding target cells. Thus the relevance of nonspecific macrophage-mediated cytotoxicity in vitro to tumour resistance in vivo may depend on the strength of the cytotoxic reaction.

The correlation of susceptibility of different Propionibacterium strains to macrophage killing and antitumor activity

The stimulation of the reticuloendothelial system and antitumor activity against sarcoma-L-1 of three different strains of Propionibacterium was investigated. The bacteria injected intraperitoneally with a single dose of 1 mg per mouse appeared to possess different effectiveness in both assays used. The same strains were examined for their susceptibility to phagocytosis and intracellular killing by murine peritoneal macrophages. The results obtained showed correlations between Propionibacterium resistance to degradation by phagocytic cells and their antitumor and stimulatory activities. It is concluded that the potency of antitumor and stimulatory activities of different strains of Propionibacterium are closely related to their cell wall structure.

Activation of pleural macrophages by intrapleural application of Corynebacterium parvum

A single ipl injection of 0.25 mg CP into CBA mice led to accumulation of macrophages in the pleural cavity, but it did not influence RES as an injection given iv ipl CP caused a three-to-five-fold increase in the number of nucleated cells in the pleural cavity which persisted at least 14 days. Of these cells 86% were macrophages as shown by their esterase activity. Less than 30% of cells from the pleural cavity of normal mice were esterase positive. Macrophages from the pleural cavity of CP-treated mice were capable of destroying in vitro cultures of a syngeneic mammary carcinoma, while normal pleural macrophages exerted no effect; the former were not cytotoxic for either syngeneic or allogeneic embryo fibroblasts. Ipl CP protected mice against iv injected mammary carcinoma cells; given to mice 7 days after iv inoculation of tumor cells it significantly reduced the number of tumor nodules in their lungs.