High levels of dietary fat: alteration of hepatic promutagen activation in the rat

Male Ola:Sprague-Dawley rats were fed diets containing either low or high levels of fats. After being fed these diets for 4 weeks, the rats were killed and individual hepatic postmitochondrial (S9) fractions were prepared. The ability of these fractions to convert the heterocyclic aromatic amines (HAAs)--2-amino-3-methylimidazo[4,5-f]quinoline; 2-amino-3,4-dimethylimidazo[4,5-f] quinoline; and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (compounds produced during the cooking of proteinaceous food)--to bacterial mutagens was studied, with the use of Salmonella typhimurium TA98 as indicator. Fractions from rats fed high-fat diets exhibited a greater ability to activate the HAAs than did those from rats fed the low-fat diet. The magnitude of the increase was dependent on the type of fat used.     

Gamma interferon priming of mouse and human macrophages for induction of tumor necrosis factor production by bacterial lipopolysaccharide

Priming of macrophages from both murine and human sources by recombinant immune interferons from Escherichia coli (r-IFN-gamma s) and activation by lipopolysaccharide (LPS) resulted in the production of tumor necrosis factor (TNF). r-IFN-gamma alone did not induce TNF production by macrophages; for this to occur, the second signal provided by small amounts (nanograms) of LPS was required. The small amounts of LPS alone were insufficient to activate the macrophages for TNF production. Priming by r-IFN-gamma was not necessary when larger amounts of LPS were employed, although an enhancement of yield resulted. Priming could also be demonstrated in vivo. Inoculation of r-IFN-gamma into mice resulted in increased yields of TNF following LPS challenge 12 hours later.     

Eradication of primary murine fibrosarcomas and induction of systemic immunity by adenovirus-mediated interferon beta gene therapy.

We determined whether an adenoviral vector-mediated murine IFN-beta gene therapy could eradicate established s.c. tumors produced by murine UV-2237m fibrosarcoma cells. The tumor cells were highly susceptible to infection by adenoviral vectors. Cells infected with 10 or 100 multiplicity of infection of AdCIFN-beta, an adenoviral vector encoding murine IFN-beta driven by the human cytomegalovirus promoter, expressed high levels of steady-state IFN-beta mRNA and produced 500 or 7,000 units of IFN-beta activity/10(6) cells/24 h, respectively. Infection of tumor cells with 30 multiplicity of infection of AdCIFN-beta (but not control AdCLacZ vector) inhibited in vitro tumor cell proliferation by 40-45%. Intralesional injection of 5 x 10(8) plaque-forming units of AdCIFN-beta (but not AdLacZ) eradicated established s.c. fibrosarcomas in syngeneic mice but not fibrosarcomas in nude mice. Mice cured of the disease developed systemic immunity against rechallenge with UV-2237m cells but not against another syngeneic tumor, the K-1735 M2 melanoma. Immunohistochemical analysis revealed that tumors injected with AdCIFN-beta contained more macrophages and CD4+ and CD8+ cells than did tumors injected with AdCLacZ or saline. Most cells in the PBS- and AdCLacZ-treated tumors stained positive for proliferating cell nuclear antigen, and few cells stained for terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling. In sharp contrast, AdCIFN-beta-treated tumors contained few proliferating cell nuclear antigen-positive cells and many terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling-positive cells. Taken together, our data demonstrate that IFN-beta gene therapy delivered by adenoviral vectors can be effective against fibrosarcomas.     

Kinetics of depression and recovery of murine hepatic cytochrome P-450 levels after treatment with the interferon inducer polyriboinosinic-polyribocytidylic acid

In vivo treatment of randombred Swiss Webster mice with polyriboinosinic-polyribocytidylic acid (poly l X poly C) inhibited the induction of cytochrome P-450's by both 3-methylcholanthrene [(MCA) CAS: 56-49-5] and phenobarbitol [(PB) CAS: 50-06-6]. Concomitant treatments with poly l X poly C and a single dose of MCA inhibited the induction of P-450's for 24 hours and delayed the obtainment of the MCA-induced P-450 levels for approximately 48-72 hours. When cytochrome P-450 levels were induced by four successive daily treatments of MCA or PB and when poly l X poly C was given on only the 1st day, induction of P-450's was completely suppressed for 24 hours and obtainment of the maximal P-450 level was delayed by 72-96 hours. Treatment with poly l X poly C of animals preinduced for P-450's by four successive daily treatments with either PB or MCA decreased the P-450 content to the noninduced basal level within 24 hours. The effect was temporary in the MCA-treated mice since P-450 content recovered to the MCA-preinduced levels within 72 hours. PB-dependent P-450 induction was short lived, and no recovery occurred after poly l X poly C treatment of PB-preinduced mice. Reduced hepatic cytochrome P-450 contents correlated with decreased abilities of liver homogenates to metabolically activate benzo [a]pyrene (CAS: 50-32-8) and N-acetyl-2-aminofluorene (CAS: 53-96-3), as scored in an Ames Salmonella typhimurium revertant assay.     

Association of protein kinase C activation with induction of ornithine decarboxylase in murine but not human keratinocyte cultures

The goal of this study was to compare the response of mouse epidermal keratinocytes (MEKs) and human epidermal keratinocytes (HEKs) to 12-O-tetradecanoylphorbol-13-acetate (TPA) with respect to the activation and downregulation of protein kinase C (PKC), the expression of c-jun and c-fos, and the expression and induction of ornithine decarboxylase (ODC) activity. Keratinocytes from adult CD-1 mice and from discarded adult human skin were grown in primary culture in a high-calcium serum-free medium that supported proliferation and differentiation. Immunoblotting of freshly isolated and cultured MEKs and HEKs for isozymes of protein kinase C revealed that fresh HEKs contained PKCα, PKCβ, and PKCδ; no PKCγ, PKC?, or PKCζ were detected. In fresh MEKs, PKCα, PKCβ, PKCΔ, and PKCζ were observed, but not PKCγ or PKCζ. After 2 wk in culture, the isozyme profiles of MEKs and HEKs were similar except that PKCγ was noticeably present in HEK cultures. Activation of partially purified total PKC by TPA was similar in freshly isolated and cultured MEKs and HEKs, indicating that the two species were similar in this regard and that 2 wk of culture did not alter this characteristic. When MEK and HEK cultures were treated with TPA for 3 h, less than 30% of the control level of PKC activity was detected, indicating that TPA-induced downregulation of PKC was similar in MEKs and HEKs. After treatment with TPA, MEK cultures produced a large induction of both c-jun and c-fos mRNA by 60 min, as determined by northern blot analysis, and a large induction of ODC mRNA and enzyme activity by 6 h. TPA treatment of cultured HEKs, however, did not induce ODC activity; in fact, less activity, compared with that of control cultures, was observed. Northern blot analysis also revealed no increase in c-jun, c-fos, and ODC mRNA in HEKs. However, c-jun and c-fos mRNA and both ODC mRNA and enzyme activity were induced in HEKs fed growth factors after several days of deprivation. This suggests that the lack of ODC induction by TPA in HEKs is probably due to species differences in downstream steps in PKC signal transduction.     

Erythropoietin/Erythropoietin-receptor system as an angiogenic factor in chemically induced murine hepatic tumors

Background To clarify the role of erythropoietin (Epo) in hepatic tumor angiogenesis, expression of Epo and its receptor (Epo-R) and content of Epo were investigated in murine chemically induced hepatic tumors.Methods To induce hepatic tumors and cirrhosis, diaminobenzidine was administered to Wistar rats for 5 months. In total, 30 hepatic tumors of greater than 3mm in diameter were induced in 12 rats. The 30 hepatic tumors were resected with the surrounding hepatic tissues. The Epo content was measured by a radioimmunoassay (RIA) method. The number of tumor vessels in a definite area was counted in 100 areas of each tumor. To demonstrate the expression of Epo-R in tumors or surrounding liver tissues, immunohistochemial staining for Epo-R was performed.Results The Epo content of tumors ranged from 6.1 to 97.8mU/ml, with a median of 21.8mU/ml, which was significantly higher than that of the cirrhotic tissues adjacent to the tumors. Epo was not detectable in the normal or cirrhotic liver tissues without tumors. A significant correlation between Epo content and vascular density was noted in the 30 hepatic tumors (correlation coefficient, 0.480; P = 0.01). Immunoreactive Epo-R was detectable in the endothelium of intervening vessels of all hepatic tumors examined.Conclusion The Epo/Epo-R system is related to the angiogenesis of murine hepatic tumors.     

Comparative mutagenicity of aflatoxins using a Salmonella/trout hepatic enzyme activation system

A modification of the Ames assay using rainbow trout (Salmogairdneri) liver postmitochondrial fraction (PMF) was developedto investigate the relative mutagenic potential of a seriesof aflatoxins (AFs). Preliminary experiments revealed that the20 000 x g (S20) liver fraction contained a higher metabolicactivity than either the S9 or S30 fractions, and that 5 mgof S20 protein/plate gave the highest mutagenic response. A9–24 h preincubation period at 25°C was also required.The results from comparative mutagenicity experiments showedthe following relative potencies: AFB₁ > AFL > AFG₁ >AFM₁ > AFB₂ > AFP₁ > AFQ₁. The relative potencies observedwith this in vitro system qualitatively correlated with thein vivo carcinogenic activity seen in trout, indicating thatthis assay is of value in predicting the carcinogenic potentialof mycotoxins in this species.     

In vivo effects of recombinant interferon alpha A/D incorporated in gelatin microspheres on murine tumor cell growth

Intraperitoneal (ip) injections of gelatin microspheres containing a very small amount of recombinant human interferon alpha A/D (A/D-IFN) (IFN-microspheres) plus free A/D-IFN improved the survival of mice bearing ascitic Meth A-R1 cells which we had isolated as IFN-resistant cells under in vitro conditions. The dose of free A/D-IFN in one injection was 10,000 IU, which was insufficient by itself for manifesting in vivo antitumor activity. In these mice, in vivo R1 cell growth was suppressed and macrophage recruitment was enhanced in comparison with mice receiving other control agents. Administration of IFN-microspheres alone was also effective but less than that of IFN-microspheres plus free A/D-IFN. Peritoneal macrophages obtained from normal or R1-bearing mice receiving ip injection of IFN-microspheres with or without free A/D-IFN were activated to inhibit the in vitro growth of R1 cells. The intratumoral injection of IFN-microspheres strongly inhibited the growth of solid R1 tumors. Intravenous injection of IFN-microspheres was effective in preventing the pulmonary metastasis of B16 melanoma cells. These results indicate that the IFN-microsphere is much more effective against tumors than free A/D-IFN.     

Potent in situ activation of murine lung macrophages and therapy of melanoma metastases by systemic administration of liposomes containing muramyltripeptide phosphatidylethanolamine and interferon gamma

Mouse alveolar macrophages (AM) were rendered tumoricidal after the intravenous administration of liposomes containing muramyl tripeptide phosphatidylethanolamine (MTP-PE), a lipophilic derivative of muramyl dipeptide. The addition of recombinant mouse interferon gamma (r-IFN-gamma) to the liposomes significantly potentiated this effect. This potentiation was also observed in therapeutic studies of mice bearing well-established spontaneous lung melanoma metastases. Multiple intravenous injections of liposomes containing both MTP-PE and r-IFN-gamma resulted in 70% survival in one group treated for small lung metastases and 50% in another group treated for large lung metastases. These data demonstrate that the presentation of r-IFN-gamma and MTP-PE in liposomes is more efficient in inducing the destruction of metastases than either agent administered alone.     

Immunomodulation of natural killer cell activity by flavone acetic acid: occurrence via induction of interferon alpha/beta

The investigational drug flavone acetic acid (FAA) systemically augments natural killer (NK) cell activity in normal and tumor-bearing mice and in human cancer patients. The results from the present investigation demonstrate that in vivo administration of FAA induces in a dose-dependent manner high levels of serum interferon (IFN) within 4 hours in BALB/c, C57BL/6, and BALB/c nude mice. Antibody neutralization studies indicated that FAA induced IFN of the alpha/beta type, while molecular hybridization studies demonstrated that FAA rapidly stimulated the production of IFN alpha mRNA in splenic leukocytes. In vivo administration of anti-IFN alpha/beta antibodies to FAA-treated mice inhibited the FAA-induced augmentation of splenic NK cell activity at 4 hours. These results suggest that FAA mediates its anti-tumor effects indirectly by immunomodulation as well as directly by antiproliferative or cytotoxic activity.     

Preferential induction of apoptosis by interferon (IFN)-beta compared with IFN-alpha2: correlation with TRAIL/Apo2L induction in melanoma cell lines.

On the basis of in vitro inhibition of tumor cell growth, IFNs have been generally considered to be antiproliferative proteins. To probe further the potential mechanisms of the antitumor effects of IFNs, we have assessed apoptosis in response to IFN-alpha2 and IFN-beta in cell lines of varied histologies, with a focus on melanomas. Many of the cell lines tested underwent apoptosis in response to IFN-beta, as assessed both by Annexin V and terminal deoxynucleotidyl transferase-mediated nick end labeling staining. In general, IFN-beta had greater growth inhibitory and proapoptotic effects than IFN-alpha2 on all cell lines. The melanoma cell line WM9, sensitive to growth inhibition by IFNs, had a greater degree of apoptosis than A375 melanoma cells, which were largely resistant to antigrowth effects of IFNs. IFN-beta-induced apoptosis was dependent on activation of the caspase cascade with cleavage of caspases 3, 8, and 9 and of the caspase 3 substrate, poly(ADP-ribose) polymerase. Caspase inhibitors benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl keton or benzyloxycarbonyl-Asp-Glu-Val-Asp-fluoromethyl keton, inhibited IFN-beta-induced apoptosis. Other changes associated with apoptosis, including the movement of cytochrome c from mitochondria to cytoplasm and DNA fragmentation, were also identified in response to IFN-beta. Apo2L ligand [tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)] was one of the early genes induced by IFN-beta in apoptosis-sensitive WM9 cells. Other sensitive melanoma cell lines had a similar IFN-beta-specific induction of TRAIL. Neutralizing antibody to TRAIL inhibited IFN-beta-induced apoptosis in WM9 cells. In resistant A375 cells, IFN-beta did not induce TRAIL/Apo2L expression. Thus, induction of TRAIL by IFNs in some tumor types may initiate the apoptotic cascade. This study offers another mechanism for the antitumor effects of IFNs.     

The role of VCAM-l/VLA-4 in the activation of allogenic T cells by murine macrophages

Vascular cell adhesion molecule 1 (VCAM-1) is a member of immunoglobulin superfamily. The principal ligand for VCAM-1 is integrin α4β/VLA-4 (very late antigen 4). It was reported that VCAM-1 was expressed on macrophages and dendritic cells, but little is known about its function on these professional antigen presenting cells (APC). The present study was performed to investigate the expression of VCAM-1 on macrophages and the role of VCAM-l/VLA-4 in the activation of allogenic T cells by murine macrophages. We analyzed VCAM-1 expression on peritoneal macrophages and macrophage cell line J774A.1 by fluorescence-activated cell sorting (FACS). Using neutralizing antibodies, we further analyzed the role of VCAM-l/VLA-4 interaction in macrophage and allogenic T cell mixed lymphocyte reaction (MLR). We found that VCAM-1 was constitutively expressed on macrophages and its expression level was upregulated by soluble tumor associated antigen (freeze-thaw lysates of FBL-3 leukemia cells) and TNF-a. In MLR assays, we observed that blocking VCAM-l/VLA-4 interaction with anti-VCAM-1 or anti-VLA-4 mAbs caused significant inhibition of the proliferative response and IL-2 production. These results suggest that VCAM-lon macrophages not only facilitates the cell-to-cell contact through adhesive interaction but also plays a role in the costimulation of T cells via its interaction with VLA-4 on the T cells. This work was supported by grants from the National Natural Science Foundation of China.No. (39730420). This is one of papers of the special issue on gene therapy research (Chin J Cancer Res Vol. 9 No. 4 December, 1997).     

Type I interferon prolongs cell cycle progression via p21WAF1/CIP1 induction in human colon cancer cells

Type I interferon (IFN) was originally identified as an immunomodulatory cytokine because of its antiviral activity. Further characterization of its biological effects revealed a prominent role in the direct control of cell growth and potent immunomodulatory and antiangiogenic actions. IFN-alpha and IFN-beta had both been classified as type I IFN, but differences in their antitumor activities were reported. We confirmed the difference in the antiproliferative activities of IFN-alpha2b and IFN-beta toward HT29 and SW480 cells. IFN treatment was observed to prolong cell cycle progression; in particular, the accumulation of S-phase population was one of the most characteristic changes. The prolongation of S-phase progression and transition into G2/M-phase was suggested to be a crucial action of type I IFN on colon cancer. Additionally, IFN activated the p21 promoter gene and induced p21WAF1/CIP1 expression. Furthermore, the cell cycle prolongation effect of IFN was suppressed when p21 expression was downregulated. Therefore, we confirmed that p21WAF1/CIP1 was a crucial target molecule for the effects of IFN on the cell cycle. Additionally, the ability of p21 induction differed between IFN-alpha2b and IFN-beta and correlated with their inhibitory activities toward cell growth. We conclude that type I IFN prolongs cell cycle progression by p21WAF1/CIP1 induction in human colon cancer cells.     

Paracrine activation of hepatic stellate cells in platelet‐derived growth factor C transgenic mice: Evidence for stromal induction of hepatocellular carcinoma

Cirrhosis is the primary risk factor for the development of hepatocellular carcinoma (HCC), yet the mechanisms by which cirrhosis predisposes to carcinogenesis are poorly understood. Using a mouse model that recapitulates many aspects of the pathophysiology of human liver disease, we explored the mechanisms by which changes in the liver microenvironment induce dysplasia and HCC. Hepatic expression of platelet‐derived growth factor C (PDGF‐C) induces progressive fibrosis, chronic inflammation, neoangiogenesis and sinusoidal congestion, as well as global changes in gene expression. Using reporter mice, immunofluorescence, immunohistochemistry and liver cell isolation, we demonstrate that receptors for PDGF‐CC are localized on hepatic stellate cells (HSCs), which proliferate, and transform into myofibroblast‐like cells that deposit extracellular matrix and lead to production of growth factors and cytokines. We demonstrate induction of cytokine genes at 2 months, and stromal cell‐derived hepatocyte growth factors that coincide with the onset of dysplasia at 4 months. Our results support a paracrine signaling model wherein hepatocyte‐derived PDGF‐C stimulates widespread HSC activation throughout the liver leading to chronic inflammation, liver injury and architectural changes. These complex changes to the liver microenvironment precede the development of HCC. Further, increased PDGF‐CC levels were observed in livers of patients with nonalcoholic fatty steatohepatitis and correlate with the stage of disease, suggesting a role for this growth factor in chronic liver disease in humans. PDGF‐C transgenic mice provide a unique model for the in vivo study of tumor–stromal interactions in the liver.     

Carcinoembryonic antigen induction of IL-10 and IL-6 inhibits hepatic ischemic/reperfusion injury to colorectal carcinoma cells

Tumor cells cause ischemia/reperfusion (I/R) injury as they arrest within the hepatic microvasculature with the production of nitric oxide (NO) and reactive oxygen species (ROS) that kill both host liver and implanting tumor cells. Carcinoembryonic antigen (CEA) both facilitates the survival of experimental metastasis to nude mouse liver by weakly metastatic human colorectal carcinomas (CRCs) and induces the release of the proinflammatory cytokine IL-6. We hypothesized that CEA also stimulates the release of the antiinflammatory cytokine IL-10 causing inhibition of the toxicity of hepatic I/R injury and indirect stimulation of tumor cell colonization of the liver. Intravenous injection of CEA produced more than 1 ng/ml of IL-10 in the systemic circulation within 1 hr which subsided by 8 hr. The IL-10 response is specific to CEA since the pentapeptide sequence in CEA that binds to the CEA receptor stimulated isolated Kupffer cells to produce IL-10. IL-10, but not IL-6, increased the survival of weakly metastatic CRC cocultured with ischemic-reoxygenated liver fragments but did not affect the survival of CRC exposed to oxidative stress in the absence of any host cells. CEA, IL-6 and IL-10 pretreatment reduced expression of iNOS but only CEA and IL-10 strongly inhibited NO and total reactive species production by ischemic-rexoygenated liver. IL-6 was toxic to CRC exposed to oxidative stress while IL-10 did not have a direct effect on CRC. Thus, CEA stimulates production of IL-10 that may enhance metastasis by promoting the ability of circulating CRC cells to survive the I/R injury of implantation.     

In vivo anti-tumor activity of combinations of interferon alpha and interleukin-2 in a murine model. Correlation of efficacy with the induction of cytotoxic cells resembling natural killer cells

The in vivo anti-tumor activity of 2 recombinant cytokines, interleukin-2 (rIL-2) and human hybrid interferon alpha (rHuIFN-alpha A/D), were tested using the murine reticulum cell sarcoma M5076. Experimental hepatic metastases, following i.v. injection of tumor cells, and tumor growth and spontaneous metastases, following s.c. injection of tumor cells, were inhibited to a greater extent in mice treated with a combination of these cytokines than in animals treated with either one alone. When used in conjunction with surgical removal of the s.c. tumor, treatment of mice with both cytokines significantly prolonged survival of tumor-bearing animals. Injection of normal mice with a combination of cytokines, but not with either cytokine alone, resulted in a marked increase in cytotoxic activity of hepatic effector cells. The effector cells in these mice appeared to be NK cells since this enhanced cytotoxicity was markedly reduced in animals treated in vivo with anti-asialo GM1 or in NK-deficient beige mice. Furthermore, no in vivo efficacy was observed in M5076-bearing beige mice treated with these cytokines. Thus, injection of mice with rIL-2 and rHuIFN-alpha A/D results in the induction of an NK-cell-like population in the liver with enhanced cytotoxic activity that correlates with the observed anti-tumor activity in vivo in this murine model. These results suggest that combinations of cytokines, in particular IFN-alpha and IL-2, can be effectively used in combination for the treatment of tumors and/or metastases.     

Purification and identification of chemokines potentially involved in kidney-specific metastasis by a murine lymphoma variant: induction of migration and NFκB activation

The ESb-MP cell line is the subclone of a highly malignant variant of murine methylcholanthrene-induced T lymphoma, ESb. When injected in vivo, ESb-MP cells metastasize to the kidney with high frequency, whereas a non-adherent variant, ESb cells, rarely form metastatic foci in the kidney. Our previous results showed that ESb-MP, but not ESb, cells were able to migrate in response to murine kidney-conditioned media (KCM). In an effort to characterize the tumor cell chemoattractant(s) produced by kidney cells, we found that the murine kidney mesangial cell line MES-13 released more chemotactic activity for ESb-MP cells than present in KCM. A major heparin-binding chemotactic activity was purified to homogeneity by sequential fast-performance liquid chromatography and reversed phase high-performance liquid chromatography. Amino acid sequencing of the formic acid-digested active fractions revealed that the purified protein was identical to murine MCP-1(JE) and its activity was neutralized by an anti-MCP-1(JE) antibody. Another chemokine, RANTES, was also purified from MES-13 cell supernatant. The chemotactic activity contained in the MES-13 cell supernatant and in murine KCM was neutralized in part by a combination of anti-MCP-1(JE) and anti-RANTES antibodies. We further examined the differences in the ESb-MP and ESb cells. Binding studies using a variety of radio-iodinated chemokines showed that although both ESb-MP and ESb cells expressed substantial levels of high-affinity binding sites for CC chemokines, only ESb-MP cells migrated in response to CC chemokines and these cells constitutively expressed higher levels of β2 integrin adhesion protein CD11b than their parental ESb cells. CC chemokines also activated NFκB in ESb-MP but not in ESb cells. Our results indicate that CC chemokines selectively chemoattract and activate ESb-MP cells. Thus, locally produced chemokines, MCP-1(JE) and RANTES in particular, may contribute to the preferential metastasis of ESb-MP cells to the kidneys. Int. J. Cancer75:900–907, 1998. Published 1998 Wiley-Liss, Inc.