Liver as a tumor-cell-killing organ

ICAM-1 on Breast Cancer Cells Suppresses Lung Metastasis but Is Dispensable for Tumor Growth and Killing by Cytotoxic T Cells

Breast tumors and their derived circulating cancer cells express the leukocyte β₂ integrin ligand Intercellular adhesion molecule 1 (ICAM-1). We found that elevated ICAM-1 expression in breast cancer cells results in a favorable outcome and prolonged survival of breast cancer patients. We therefore assessed the direct in vivo contribution of ICAM-1 expressed by breast cancer cells to breast tumorigenesis and lung metastasis in syngeneic immunocompetent mice hosts using spontaneous and experimental models of the lung metastasis of the C57BL/6-derived E0771 cell line, a luminal B breast cancer subtype. Notably, the presence of ICAM-1 on E0771 did not alter tumor growth or the leukocyte composition in the tumor microenvironment. Interestingly, the elimination of Tregs led to the rapid killing of primary tumor cells independently of tumor ICAM-1 expression. The in vivo elimination of a primary E0771 tumor expressing the ovalbumin (OVA) model neoantigen by the OVA-specific OVA-tcr-I mice (OT-I) transgenic cytotoxic T lymphocytes (CTLs) also took place normally in the absence of ICAM-1 expression by E0771 breast cancer target cells. The whole lung imaging of these cells by light sheet microscopy (LSM) revealed that both Wild type (WT)- and ICAM-1-deficient E0771 cells were equally disseminated from resected tumors and accumulated inside the lung vasculature at similar magnitudes. ICAM-1-deficient breast cancer cells developed, however, much larger metastatic lesions than their control counterparts. Strikingly, the vast majority of these cells gave rise to intravascular tumor colonies both in spontaneous and experimental metastasis models. In the latter model, ICAM-1 expressing E0771- but not their ICAM-1-deficient counterparts were highly susceptible to elimination by neutrophils adoptively transferred from E0771 tumor-bearing donor mice. Ex vivo, neutrophils derived from tumor-bearing mice also killed cultured E0771 cells via ICAM-1-dependent interactions. Collectively, our results are a first indication that ICAM-1 expressed by metastatic breast cancer cells that expand inside the lung vasculature is involved in innate rather than in adaptive cancer cell killing. This is also a first indication that the breast tumor expression of ICAM-1 is not required for CTL-mediated killing but can function as a suppressor of intravascular breast cancer metastasis to lungs.

Murine Kupffer cells and hepatic natural killer cells regulate tumor growth in a quantitative model of colorectal liver metastases

This investigation aimed to develop a biologically relevant murine model of colorectal liver metastases and determine if Kupffer cells (KC) and hepatic natural killer cells (hNKC) regulate tumor growth. The model involves the injection of murine colon adenocarcinoma 26 (MCA 26) tumor cells into the portal vein of female-specific pathogen-free BALB/c mice. Metastases developed in all animals, and the growth was limited entirely to the liver. To determine if KC and hNKC control the development of liver metastases, the in vivo function of these hepatic effector cells was modulated. Tumor growth was quantitated by the uptake of 125I into tumor DNA. Stimulation of the KC and hNKC produced a significant (P less than 0.01) dose-dependent decrease in 125I uptake in the liver in both treatment groups, which was associated with a significant improvement in survival (P less than 0.05). The in vivo cytotoxic function of the liver was inhibited with an intravenous injection of gadolinium chloride (for KC) or asialo GM1 antiserum (for hNKC). Inhibition of KC and hNKC cytotoxic function led to a significant (P less than 0.01) increase in 125I uptake in the liver and a significant decrease in survival (P less than 0.05).

Cytotoxic T-cells and antibody-producing cells isolated from liver and spleen of immunized rats

Liver, strategically positioned within the circulation system, is a major trap for circulating tumor cells. Trapping and killing of tumor cells may be mediated by Kupffer cells and natural killer cells. In addition to these spontaneously cytotoxic cells, we isolated T-killer cells and antibody-producing cells from the liver after immunization with xenogeneic cells. Since tumor surveillance may include T-killer cells and antibody-dependent killer cells, the liver is able to attack tumor cells by "natural" and "induced" cytotoxic mechanisms.

Inhibition of murine hepatic tumor growth by liposomes containing a lipophilic muramyl dipeptide

We have investigated the ability of liposomes containing a lipophilic muramyl dipeptide, N-acetylmuramyl-L-alanyl-D-isoglutamine glycerol dipalmitate (MDP-GDP) to activate Kupffer cell tumoricidal activity in situ and to inhibit the growth of experimental hepatic micrometastases of tumor cell line H-59, a liver-homing variant of the Lewis lung carcinoma. Liposomes prepared from distearoylphosphatidylcholine/dimyristoylphosphatidylglycerol (DSPC/DMPG) and containing MDP-GDP (1 mumol and 2 micrograms, respectively) were efficiently taken up by the liver after i.v. administration. A single i.v. injection of DSPC/DMPG liposomes containing MDP-GDP was capable of inducing Kupffer cell tumoricidal activity against H-59 tumor cells as measured in vitro. Control liposomes or 100 micrograms free MDP were ineffective in inducing Kupffer cell tumoricidal activity in situ. Two treatment regimens were evaluated in vivo: firstly, C57BL/6 mice were injected with tumor cell line H-59 and subsequently treated with multiple injections of liposomal MDP-GDP. Secondly, treatment with liposomal MDP-GDP was initiated prior to tumor cell injection and continued after tumor cell injection. The ability of liposomes containing MDP-GDP to reduce the number of hepatic micrometastases using the first protocol was related to the tumor cell inoculum, significant inhibition being observed at lower liver tumor burdens (less than 25 tumor nodules). Pretreatment of the mice prior to tumor cell challenge followed by treatment afterwards greatly enhanced the efficacy of liposomal MDP-GDP and brought about a highly significant inhibition of the growth of experimental metastases even at high liver tumor burdens (greater than 50 nodules).

Murine liver metastasis model using L5178Y-ML lymphoma and the effect of antitumor agents on the metastasis

A reproducible tumor model for liver metastasis has been developed from murine L5178Y lymphoma line by sequential cycles of subcutaneous inoculation of liver tumor cells, that were originally generated in livers of female (BALB/c x DBA/2)F1 mice by injecting the parental cells into the tail vein. This variant (L5178Y-ML) metastasized predominantly to the liver after intravenous or subcutaneous injection. The livers of the animals killed 9 days after intravenous implantation of 5 x 10(5) tumor cells were about 3 times the weight of control livers. All tumor-bearing mice died 10 to 12 days after inoculation. Subcutaneous implantation of L5178Y-ML in the side flank of mice induced metastatic nodules spontaneously in the livers. The tumor cells proliferated more in livers than in the implanted sites, compared with the parental L5178Y cells. The effects of 5-fluorouracil, mitomycin C, cis-platinum and doxorubicin on the liver metastasis of L5178Y-ML were examined at subtoxic doses; 5-fluorouracil was the most effective in both inhibiting the tumor growth in livers and prolonging the survival period of mice. This model provides a useful tool for the experimental therapy of hepatic tumors in mice.

Activation of murine Kupffer cell tumoricidal activity by liposomes containing lipophilic muramyl dipeptide

The ability of liposomes containing a lipophilic muramyl dipeptide, N-acetylmuramyl-L-alanyl-D-isoglutamine-glycerol dipalmitate, to induce Kupffer cell tumoricidal activity has been investigated. Liposomal N-acetylmuramyl-L-alanyl-D-isoglutamine-glycerol dipalmitate was 16-fold more potent than liposomal N-acetylmuramyl-L-alanyl-D-isoglutamine and 2,400-fold more potent than N-acetylmuramyl-L-alanyl-D-isoglutamine in inducing Kupffer cell tumoricidal activity in vitro. A single i.v. injection of liposomes containing N-acetylmuramyl-L-alanyl-D-isoglutamine-glycerol dipalmitate was capable of inducing Kupffer cell tumoricidal activity as measured against B16-melanoma cells after Kupffer cell isolation. Maximal cytotoxic activity was obtained with 1 microgram muramyl dipeptide-glycerol dipalmitate encapsulated within liposomes: doses of 10 or 100 micrograms inhibited tumoricidal activity. Kupffer cells from mice treated with liposomes containing N-acetylmuramyl-L-alanyl-D-isoglutamine-glycerol dipalmitate remained cytotoxic for at least 6 days after injection. Liposomal N-acetylmuramyl-L-alanyl-D-isoglutamine was significantly less potent than liposomal N-acetylmuramyl-L-alanyl-D-isoglutamine-glycerol dipalmitate in inducing Kupffer cell tumoricidal activity in situ. N-Acetylmuramyl-L-alanyl-D-isoglutamine was capable of inducing Kupffer cell tumoricidal activity in vitro: its failure to induce tumoricidal activity in situ at doses of 1,000 micrograms demonstrates the utility of liposomal carriers for the in vivo activation of Kupffer cells by muramyl dipeptides.

Natural cytotoxic cells from rat liver and spleen kill human glioma cells

Natural cytotoxic cells from rat spleen and rat liver, (isolated using the collagenase method) were found to be cytotoxic against different lines of human gliomas: T406, T508, T705, HeRo, HeRoCl 1, HeRoCl 8, and HeRo-SV 7/114. After 18 h the lytic units ranged from 75 to 251 in the liver and from 5 to 24 in the spleen. Analyzing the ratio of lysis at 4 h/18 h, it may be concluded that this natural killing is predominantly macrophage (Kupffer cell)-dependent. Lysis by Kupffer cells cannot be increased by transforming glioma cells with SV40. Experiments with SV40-transformed mouse fibroblasts (3T3) and virus-transformed human cell lines (SV80) suggested a "SV40" receptor on Kupffer cells. Thus Kupffer cells have receptors for glioma cells and SV40-dependent membrane structures.

Mechanisms of immunological response induced in CD2F1 mice by administration of semisyngeneic L 1210 leukemia cells treated with cyclophosphamide

CD2F1 mice were immunized against semisyngeneic L 1210 leukemia. Immunization was achieved by four i.p. injections, in weekly intervals, of L 1210 cells treated in vivo twice with 200 mg/kg of cyclophosphamide. The immunized animals survived i.p. challenge with 1000 untreated L 1210 cells that was lethal for nonimmunized mice. The immunity could be abrogated in vivo with anti-mouse thymocyte serum, carrageenan or reserpine, but not by anti-mouse IgG serum, suggesting participation of T lymphocytes and macrophages in the response. Moreover, lymphocytes and macrophages from the peritoneal cavity of immunized mice were cytotoxic in vitro for L 1210 cells. The immunity, at least partially, could be adoptively transferred with peritoneal exudate cells or splenocytes.