Suppression of Ehrlich ascites tumors in mice by minute virus of mice

As a model system to study parvoviral oncosuppression, Ehrlich ascites (EA) cells were injected into the peritoneal cavities of ICR mice, and the effect of im injection of minute virus of mice (MVM) on EA tumor growth was examined. Coinjection with MVM resulted in a dramatic inhibition of EA tumor formation. Tumor suppression required viable, infectious virus. Mice that had survived one EA-MVM coinjection acquired long-term resistance to additional injections of EA cells.

Effect of nonspecific immune stimulation with BCG and polidin on the Ehrlich ascites tumor growth

Investigations were performed to study: 1) the antitumor effect of BCG pretreatment on the development of Ehrlich ascites tumor in mice; 2) the effect of BCG administration in relation to the period of time before tumor inoculation and the dose levels used, and 3) the antitumor effect of an associated pretreatment of BCG and Polidin on the development of Ehrlich ascites tumor. BCG administered prior to Ehrlich ascites tumor inoculation have a protective effect evidenced by a delay in tumor development, a prolonged survival of the tumor host and, in some cases, even inhibition of tumor growth. The effect of BCG was highly dependent on 1) the dose and the time of administration of BCG and) 2 the combined pretreatment of BCG and Polidin.

Selenium interactions with carcinogens

Although selenium was once considered to be a toxic, undesirable and carcinogenic element, it is now recognized as an essential element with anticarcinogenic properties. Epidemiological studies in the United States have shown an inverse relationship between selenium intake and certain forms of cancer in humans, but other factors must be considered since cancer is not higher in people living in selenium-deficient areas of the world (Finland, New Zealand, and Keshan disease area, China). Under most dietary conditions, selenium has been shown to reduce the spontaneous mammary tumor incidence in an inbred strain of mice. In general, selenium will counteract to various degrees, the chemical carcinogens used to produce lesions of the skin [coal tar, 3-methylcholanthrene, alpha-pyrene, and 7,12 dimethylbenz(a) anthracene (DMBA)], liver (3-methyl-4-dimethyl-aminoazobenzene, aflatoxin B1, and 2-acetylaminofluorene), mammary gland (DMBA and N-methyl-N-nitrosurea), and intestinal tract [1,2-dimethylhydrazine, bis(2-oxopropyl)nitrosamine, and azoxymethane]. Dietary factors, such as fat, will modify the protective effects of selenium. High dietary unsaturated fats, for example, markedly increase the mammary tumors in rats treated with DMBA, and selenium will reduce the tumor incidence but not to the level of rats fed a low fat diet. Other factors known to affect the anticarcinogenic effects of selenium include synthetic antioxidants, vitamin E, vitamin A and ascorbic acid. The mechanisms of selenium counteraction of carcinogens remain unknown.

The effect of nonspecific immune stimulation with Corynebacterium parvum and polidin on the Ehrlich ascites tumor growth

Investigations were performed: a) to compare the effect of two nonspecific immunostimulants, Polidin and Corynebacterium parvum, on the development of Ehrlich ascites carcinoma in mice; b) to determine whether the effects are dependent on the tumor cell dose inoculated into the animals. C. parvum and Polidin administered prior to Ehrlich ascites tumor inoculation have a protective effect evidenced by a delay in tumor development, a retardation in tumor growth and a prolonged survival of the tumor host. The effect of immunostimulants was highly dependent on the tumor cell dose inoculated into mice and was more marked with C. parvum.

Antitumor component(s) of yogurt: fractionation

Two methods of fractionation were employed to separate antitumor component(s) from yogurt. First, yogurt was separated by dialysis. Although feeding of the dialyzate fraction to mice inoculated with Ehrlich ascites tumor cells resulted in 32.9% inhibition of tumor cell counts and 23.5 to 26.3% reduction of deoxynucleic acid content of ascitic fluid, feeding of the yogurt retentate did not reduce tumor proliferation. Second, an aqueous fraction of yogurt was prepared by removal of the ether soluble matter. Administration of aqueous fraction at 2 mg/mouse intravenously resulted in 25.1 to 32.3% less cell growth whereas intraperitoneal inoculation resulted in only 15.0 to 15.9% reduced tumor proliferation. Antitumor activity may be due to a component(s) with a molecular weight less than or equal to 14,000, and it presumably is not bound chemically to any larger compound because it could be separated by dialysis.

[Effects of the contamination by polychlorobiphenyls (PCBs) on the growth of the Ehrlich tumor in mice (author's transl)]

The effects of a 3-month experimental contamination with a commercial mixture of PCBs, DP5 (corresponding to Aroclor 1254) have been studied on groups of 25 SWISS female mice, at levels of 0, 10, 50 and 250 ppm added at feeding. After subcutaneous injection of 0,2 ml of Ehrlich's tumoral ascites liquid, the evolution of tumors as well as the mortality level, were different in the treated groups as compared to the control group. The percentages of mortality due to tumors were the following: control (0 ppm) = 50% 10 ppm = 5% 50 ppm = 5% 250 ppm = 35% Thus, contamination by PCBs seems to have protected these mice against the Ehrlich tumor. No decrease in body weight was noted neither were differences in size or appearance of the thymus and the spleen in the treated mice; an evident liver hypertrophy was noted in all PCB treated mice.

Studies on the endotoxin induced tumor resistance

In summary, this report has discussed the immunologic mechanisms involved in the enhancement of nonspecific resistance to tumor by endotoxin. The optimal conditions for tumor protection involved pretreatment with approximately 25 mug LPS administered at the siteof subsequent tumor challenge. In an attempt to relate endotoxin structural components to the ability to enhance TUR, a variety of whole LPS's, endotoxic glycolipids and PS preparations were compared. While all of the intact LPS's and several of the glycolipids were effective in enhancing TUR, some endotoxic glycolipids were totally inactive although they were equally toxic. Some lipid-free PS preparations were also active although less than whole LPS. Evidence was presented to suggest that mechanism for enhancement of TUR involves B cells and macrophages but not T cells. The mechanism also involves the production of soluble factors which are released into the serum of mice in response to LPS or PS. These factors can transfer and mediate the antitumor effects of LPS. The preinfection of mice with BCG enhanced the activity of LPS and PS in the production of antitumor activity.

Inhibition of growth of mouse ehrlich ascites by normal tissue extracts

A dialyzable component from the aqueous extracts of mouse skeletal muscle and liver inhibited in vitro growth of a mouse Ehrlich ascites. A similar component was not detected in extracts of spleen, kidney, lung, skin, serum or small intestine. The muscle component appeared to be different from that of the liver in its resistance to heat and its stability in the culture medium. Both components however were stable on storage at 4, 23 and 37 degrees C for 72 h. Intraperitoneal injection of the muscle and liver component into mice previously innoculated with Ehrlich ascites significantly decreased tumor incidence in these animals as compared with the control.

Regression of Ehrlich ascites carcinoma in BCG-sensitized mice

Intraperitoneal inoculation of CF1 mice with Bacillus Calmette-Guérin (BCG) protected many of them against the ascites form of Ehrlich carcinoma; and, for those that developed cancer, complete regression occurred in up to 50% of the cases at an advanced state of the neoplastic disease. In contrast, when a booster dose of BCG was administered in admixture with tumor cells, the incidence of the tumor was lower and tumor regressions were very rarely observed in mice that developed cancer. Trypan blue, an inhibitor of lysosomal enzymes of macrophages, was found to markedly suppress the natural (innate) antitumor resistance of control mice as well as the acquired resistance and tumor regressions of BCG-sensitized mice. Moreover, a comparison of the cytotoxic activity of the adherent (macrophages) and nonadherent (predominantly lymphocytes) cells isolated from the peritoneal cavity of BCG-sensitized mice, as measured by the inhibition of DNA synthesis, revealed that the effector cells were amongst the macrophages. In contrast, spleen macrophages were devoid of cytotoxicity. The spleen lymphocytes from both BCG-sensitized and control mice possessed about the same significant cytotoxic activity. These results indicate that the activated peritoneal macrophages, induced by a local injection of BCG, could play an important role in the antitumor immunity against Ehrlich carcinoma.

C'3 participation in the rejection of some experimental tumors

The possibility that C'3 participates in tumor rejection was investigated in DBA/2 mice previously immunized against L1210 leukemia and in Swiss mice previously immunized against Ehrlich's adenocarcinoma. In both the cases, animals treated with an appropriate dose of cobra venom factor to produce a C'3 depletion for some days after the tumor challenge, developed the neoplasia and had a mortality rate analogous to that of non-immunized animals. Studies on the peritoneal washing cells obtained at different times after the challenge revealed that in C'3 depleted immunized mice IgM are present on lymphocytes, macrophages and tumor cells, as in the immunized controls, but no contract between the cells and no macrophage phagocytosis were observed and the number of tumor cells increased progressively. These findings indicate that C'3 is critically involved in the rejection of the experimental tumors considered.

Enhancement of immunity against murine syngeneic tumors by a fraction extracted from non-pathogenic mycobacteria

The data reported here demonstrate that a preparation extracted from nonpathogenic mycobacteria such as Mycobacterium smegmatis and hereafter referred to as interphase material protected mice against Ehrlich ascitic carcinoma, L-1210 leukemia, and another syngeneic lymphoid leukemia. Furthermore, mice treated by this preparation were much less susceptible to endotoxins than when stimulated by BCG (bacillus Calmette-Guerin) or M. smegmatis cells. Moreover, guinea pigs treated by interphase material administered in Freund's incomplete adjuvant showed an increased immune response, yet their sensitivity to tuberculin was much weaker than that of controls sensitized with Freund's complete adjuvant. Finally, resistance to Columbia SK virus infection could be demonstrated when interphase material was administered to mice prior to virus challenge.

Low molecular weight water-soluble peptidoglycans as adjuvants and immunostimulants

The tetrasaccharide-heptapeptide (TH), when injected with mineral oil, exerted a strong adjuvant effect. It stimulated B and T cells, but did not increase the phagocytic activity of the reticulo-endothelial system. While BCG exerted significant preventive effect on the growth of sarcoma 180, leucosarcomatosis an EHRLICH ascitic tumor, TH, at the doses used, was devoid of such activity.

The prevention of Ehrlich ascites tumor using intraperitoneal colloidal 198Au. Dose vs. size of inoculum

Previous work has shown that radioactive colloids can cure Ehrlich ascites tumor. In this experiment, the dose of colloidal 198Au needed has been correlated with the number of tumor cells inoculated. On Day 1, varying numbers of Ehrlich cells (10(2), 10(3), 10(4), 10(5), 10(6)) were injected intraperitoneally into 310 BALB/c male mice. Two hours later, varying doses (10, 20, 40, 80, and 160 muCi) of 198Au were injected intraperitoneally. Controls were injected with normal saline. Generally, the lower cell inoculums and higher doses of 198Au yielded better survival rates.