Therapy of cancer metastasis by activation of the inducible nitric oxide synthase

The process of cancer metastasis consists of multiple sequential and highly selective steps. The vast majority of tumor cells that enter the circulation die rapidly; only a few survive to produce metastases. This survival is not random. Metastases are clonal in origin and are produced by specialized subpopulations of cells that preexist in a heterogeneous primary tumor. Experimental studies concluded that metastatic cells survive in the circulation whereas nonmetastatic cells do not. In part, this difference is due to an inverse correlation between expression of endogenous inducible nitric oxide synthase (iNOS) and production of nitric oxide (NO) and metastatic potential. Direct evidence for the role of iNOS in metastasis has been provided by our data on transfection of highly metastatic murine K-1735 clone 4 (C4.P) cells which express low levels of iNOS, with a functional iNOS (C4.L8), inactive mutated iNOS (C4.S2), or neomycin resistance (C4.Neo) genes in medium containing 3 mM of the specific iNOS inhibitor NG-L-methyl arginine (NMA). C4.P, C4.Neo, and C4.S2 cells were highly metastatic, whereas C4.L8 cells were not. Moreover, C4.L8 cells produced slow-growing subcutaneous tumors in nude mice, whereas the other 3 cell lines produced fast-growing tumors. In vitro studies indicated that the expression of iNOS in C4.L8.5 cells was associated with either cytostasis or cytolysis via apoptosis, depending upon NO output. The tumor cells producing high levels of NO underwent autocytolysis and produced cytolysis of bystander cells under both in vitro and in vivo conditions. Multiple i.v. injections of liposomes containing a synthetic lipopeptide upregulated iNOS expression in murine M5076 reticulum sarcoma cells growing as hepatic metastases. The induction of iNOS was associated with the complete regression of the lesions. Transfection of interferon-beta suppressed tumor formation and eradicated metastases, which was apparently linked to iNOS expression and NO production in host cells such as macrophage. Besides mediating cell death, NO produced tumor suppression by regulating expression of genes related to metastasis, e.g., survival, invasion, and angiogenesis. Suppression of metastasis can be achieved through use of immunomodulators that induce iNOS expression in tumor lesions or by the direct delivery of the iNOS gene to tumor cells or host cells through liposome and/or viral vectors.

Abrogation of tumorigenicity and metastasis of murine and human tumor cells by transfection with the murine IFN-beta gene: possible role of nitric oxide

The purpose of this study was to determine whether sustained local production of murine IFN-beta (mIFN-beta) could inhibit the tumorigenicity and metastasis of human and murine tumor cells implanted into nude mice. Human melanoma cells (A375SM), renal carcinoma cells (SN12PM6), and colon carcinoma cells (KM12SM) were transfected with mIFN-beta or a control neomycin resistance vector. All cell lines grew well in culture. Tumor cells were injected into the subcutis, kidney, spleen, or lateral tail vein of nude mice. Parental or control transfected cells produced local tumors and experimental or spontaneous lung metastases, whereas mIFN-beta-transfected cells did not. In vivo survival experiments using [125I]IdUdR-labeled cells showed that by day 7 after s.c. implantation, all IFN-beta-transfected cells died. IFN-beta transfection prevented the outgrowth of parental or control-transfected cells only when they were injected together with transfected cells into one site, suggesting that IFN-beta promoted a local lysis of the bystander cells. Similar indirect antitumor activity was demonstrated in various human (KM12SM and SN12PM6) and murine (CT-26 colon carcinoma, RENCA renal cell carcinoma, and 3LL Lewis lung carcinoma) tumors. The IFN-beta-transfected tumor cells stimulated a high level of nitric oxide production by murine macrophages under in vitro and in vivo conditions, which correlated with the vigorous nonspecific antitumor activity. Collectively, these results demonstrate that local production of IFN-beta can eradicate tumor cells of different histology by inducing inducible nitric oxide synthase expression in infiltrating cells.

Nitric oxide-mediated apoptosis of K-1735 melanoma cells is associated with downregulation of Bcl-2

Recent studies have shown that the treatment of nonmetastatic K-1735 murine melanoma cells with cytokines induces the production of nitric oxide (NO) and hence cell death. The purpose of this study was to determine the mechanism of this cytokine-induced NO-mediated apoptosis. Incubation of nonmetastatic K-1735 cells with interleukin-1 alpha (IL-1alpha) and interferon-gamma (IFN-gamma) induced high NO production, Bcl-2 downregulation, and apoptotic cell death. In contrast, incubation of metastatic K-1735 cells with IL-1alpha and IFN-gamma did not induce significant production of NO, downregulation of Bcl-2, or cell death. The exposure to exogenous NO derived from the NO donors, sodium nitroprusside (SNP), or GEA5024 produced a dose-dependent apoptotic cell death in both the metastatic and nonmetastatic K-1735 cells, which was associated with downregulation of Bcl-2 at the mRNA level and, to a lesser extent, at the protein level. Nonmetastatic and metastatic K-1735 cells transfected with the Bcl-2 gene were more resistant to apoptosis mediated by both endogenous and exogenous NO. Subsequent to intravenous injection, the tumor cells transfected with the Bcl-2 gene had an increased survival rate in the lungs of nude mice and produced a higher number of experimental lung metastases. These data suggest that NO-induced apoptosis in K-1735 melanoma cells is associated with downregulation of Bcl-2.

Use of retroviral vectors encoding murine inducible nitric oxide synthase gene to suppress tumorigenicity and cancer metastasis of murine melanoma

The purpose of this study was to determine whether retrovirus-mediated transfer of murine macrophage inducible nitric oxide synthase (iNOS) can produce inhibition of tumorigenicity and metastasis. Retroviral vectors encoding macrophage iNOS constructed in pLXSN, a retroviral vector with the iNOS gene under the control of a long terminal repeat promoter, were stably transfected into PA317 cells. Medium harvested from confluent monolayers of the virus-producing cell lines was used for infection of the murine K-1735 melanoma cells. Expression of iNOS was confirmed by northern and Western blot analyses. Functional iNOS protein expression was confirmed by bioassay of nitrite accumulation in the culture supernatant. Cells infected by a control iNOS-negative retrovirus produced fast-growing subcutaneous tumors and many lung metastases in nude mice, whereas iNOS-transduced cells produced slow-growing tumors and few lung metastases, showing that the infection of murine tumor cells by retroviruses harboring the iNOS gene can suppress tumorigenicity and metastasis.

Activity-dependent expression of NT-3 in muscle cells in culture: implications in the development of neuromuscular junctions

Although activity-dependent expression of neurotrophins has been studied extensively in the CNS, its physiological role during synapse development is not well established. At the developing neuromuscular junction in culture, exogenous application of the neurotrophin BDNF or NT-3 has been shown to acutely potentiate synaptic transmission and chronically promote synapse maturation. Using the same cell culture model, we have investigated activity-dependent neurotrophin expression in muscle cells and its role in developing neuromuscular synapses. Membrane depolarization, elicited by either depolarizing agents or repetitive electric stimulation, rapidly and specifically increased the levels of NT-3 mRNA in developing Xenopus laevis muscle cells in culture. NT-3 gene expression also was enhanced by acetylcholine (ACh), the neurotransmitter that causes muscle membrane depolarization. The effects of depolarization were mediated by increasing intracellular calcium concentration. Moreover, factor(s) induced by membrane depolarization appeared to enhance synaptic transmission at the developing neuromuscular junction. The frequency of spontaneous synaptic currents (SSCs) recorded from neuromuscular synapses was increased significantly after treatment with conditioned medium from depolarized muscle cultures. The amplitude, rise time, and decay time of SSCs were not affected, indicating a presynaptic action of the conditioned medium. The effects of the conditioned medium were blocked, partially, by the NT-3 scavenger TrkC-IgG, suggesting that the potentiation of synaptic efficacy was attributable, at least in part, to elevated NT-3 as a consequence of muscle depolarization. Thus, activity-dependent expression of muscle NT-3 may contribute to the development of the neuromuscular synapse.

Destruction of bystander cells by tumor cells transfected with inducible nitric oxide (NO) synthase gene

BACKGROUND

The activation of an enzyme, inducible nitric oxide synthase (iNOS), catalyzes the production of endogenous nitric oxide (NO). NO, in turn, is associated with cell death, suppression of tumor development, and inhibition of metastasis of murine melanoma cells. Moreover, the in vivo induction of iNOS is associated with regression of established hepatic metastases. Whether this regression required the activation of the iNOS gene in every tumor cell or whether NO-producing tumor cells can also kill bystander (neighboring) cells has been previously unknown.

PURPOSE

The goal of this study was to determine whether cells producing NO and then undergoing autolysis can also kill bystander cells in vitro and in vivo.

METHODS

Murine K-1735 C4.parental (C4.P) melanoma cells were transfected with the functional iNOS gene (transfectant denoted as C4.L8) or with a control truncated-nonfunctional iNOS gene (transfectant denoted as C4.S2). NO-mediated cytolysis and bystander cell killing were determined in vitro and in vivo.

RESULTS

Only the functional iNOS-transfected C4.L8 cells produced NO and underwent autolysis. C4.L8 cells also produced statistically significant lysis of iNOS-negative C4.P cells. This lysis was suppressed by the specific iNOS inhibitor N(G)-methyl-L-arginine. NO-producing C4.L8 cells and control C4.P or C4.S2 cells were injected subcutaneously into syngeneic C3H/HeN mice. Control C4.P and C4.S2 cells produced rapidly growing subcutaneous tumors, whereas C4.L8 cells did not. The mixture of C4.P and C4.S2 cells (1:5 ratio) produced rapidly growing subcutaneous tumors, whereas the mixture of C4.P and C4.L8.5 cells (1:5 ratio) produced slow-growing tumors. The subcutaneous growth of C4.P cells was not affected by C4.L8.5 cells injected subcutaneously at a distant site. Mixtures of C4.P cells labeled with [(125)I]iododeoxyuridine and C4.L8 cells (NO producing) or C4.S2 cells (control) were injected subcutaneously. The survival rate of the radiolabeled cells indicated that the NO-producing C4.L8.5 cells lysed the bystander C4.P cells.

CONCLUSION

The production of high-level endogenous NO causes autolysis in tumor cells and lysis of bystander cells under in vitro and in vivo conditions.

IMPLICATIONS

NO-mediated cell killing does not require transfection of genes into every cell in a neoplasm.

Direct correlation between DNA repair capacity and metastatic potential of K-1735 murine melanoma cells

The purpose of this study was to determine whether the ability of K-1735 murine melanoma cells to repair DNA damage correlates with their metastatic potential. Three nonmetastatic clones, four metastatic clones, and three somatic-cell hybrids between metastatic and nonmetastatic clones were exposed to incident ultraviolet (UV) light (254 nm). Cell survival was determined by the microculture tetrazolium assay, which measures cell metabolic activity. DNA repair capacity was determined with a host-cell reactivation assay, which measures the activities of chloramphenicol acetyltransferase encoded by the reporter gene in both UV-damaged and undamaged plasmid (control) pCMV cat 40 h after transfection. No discernible differences in transfection efficiencies were found between K-1735 clones with low and high metastatic potential or between cells transfected with UV-damaged and control plasmids. DNA repair capacity directly correlated with cell survival (p < 0.05) and with metastatic potential in the K-1735 clones and somatic cell hybrids (p < 0.05). These data suggest that the intrinsic resistance of melanoma metastases to systemic chemotherapy may be due, in part, to the cells' enhanced DNA repair capacity.

Interleukin 10 suppresses tumor growth and metastasis of human melanoma cells: potential inhibition of angiogenesis

Interleukin 10 (IL-10) inhibits the production of a wide range of cytokines in various cell types. The purpose of this study was to determine whether the expression of the IL-10 gene can influence tumor growth and metastatic properties of human melanoma cells. The human melanoma cell line, A375P, which does not produce endogenous IL-10, was transfected with a hygromycin expression vector (control) or a vector containing full-length murine IL-10 cDNA. A375P parental cells, A375P-Hygro, and A375P-IL-10-positive cells were injected s.c. and i.v. into nude mice. A375P-IL-10 cells produced significantly slower growing s.c. tumors and fewer lung metastases than control cells. The tumorigenicity of the human melanoma A375SM and the murine melanoma B16-BL6 cells was also significantly inhibited when they were admixed with A375P-IL-10 but not with A375P-Hygro before s. c. injection into nude mice. The suppression of tumor growth and metastasis was directly correlated with a decrease in neovascularity determined by immunostaining with anti-factor VIII. Because tumor-associated macrophages are the major source of angiogenic molecules in melanoma, we used reverse transcription-PCR to demonstrate that IL-10 down-regulates the production of vascular endothelial growth factor, the most potent angiogenic factor in activated macrophages. Other factors involved in angiogenesis such as IL-1beta, tumor necrosis factor-alpha, IL-6, and the proteinase matrix metalloproteinase-9 were also inhibited in activated macrophages by supernatants from A375P-IL-10 cells. Collectively, these data suggest that the production of IL-10 by tumor cells inhibits macrophages-derived angiogenic factors, and hence, tumor growth and metastasis.

Regulation of carcinoembryonic antigen expression in human colon carcinoma cells by the organ microenvironment

The expression of carcinoembryonic antigen (CEA) is thought to be involved in homotypic adhesion and has been associated with the progression of human colon carcinomas (HCC) to the metastatic state. Three cell lines established from surgical specimens of Dukes' stage D (KM20) or Dukes' stage B (KM12C, KM12SM) with high and low preoperative CEA serum levels, respectively, were studied subsequent to growth in culture, in the subcutis (ectopic) or cecal wall (orthotopic) of nude mice. In all cell lines, CEA expression was higher in cecal tumors than in subcutaneous lesions. The degree of differentiation and CEA expression by HCC growing in the cecal wall of nude mice correlated with the pathological diagnosis and preoperative CEA level of the original patients. To better understand the regulation of CEA expression, the HCC cells were grown in culture as sparse and confluent monolayers or as multicell spheroids. The CEA expression level increased in all three cell lines growing as confluent monolayers and was highest in multicell spheroids. Treatment of sparse monolayer cultures of KM12SM cells with mitomycin-C inhibited cell division and was associated with higher production of CEA protein. Moreover, conditioned media from confluent monolayer cultures or from spheroids up-regulated CEA production in sparse monolayer cells. These data show that CEA expression in HCC cells may be regulated by cell density and by factors from the organ environment.

Bcl-2 protects cells from cytokine-induced nitric-oxide-dependent apoptosis

Cytokine-mediated cell death in tumor cells can be achieved through endogenous nitric oxide (NO) from within tumor cells or exogenous NO from either activated macrophages or endothelial cells. The purpose of this study was to determine the role of Bcl-2 in NO-mediated apoptosis. The incubation of murine L929 and NIH3T3 cells with interleukin-1 alpha (IL-1 alpha) and interferon gamma (IFN gamma) induced high endogenous NO production only in the L929 cells that also underwent apoptosis. NIH3T3 cells were not resistant to NO-mediated apoptosis. In fact, the incubation of L929 and NIH3T3 cells with exogenous NO derived from NO donors, sodium nitroprusside, or S-nitroso-N-acetyl-DL-penicillamine (SNAP) induced death, characterized by typical apoptotic morphology and DNA fragmentation, in both cell types, but to a higher degree in NIH3T3 cells than in the L929 cells. We then measured the effect of Bcl-2 expression on exogenous NO-induced apoptosis. At both the mRNA and protein levels, L929 fibroblasts expressed higher levels of endogenous mouse Bcl-2 than did NIH3T3 cells. At the same time, L929 cells were much more resistant to exogenous NO-induced cell death than were NIH3T3 cells. The inverse correlation between mouse Bcl-2 expression and sensitivity to exogenous NO-mediated cell death was also found in the murine K-1735 melanoma C-23 and X-21 clonal populations. Transfection of both NIH3T3 cells and L929 cells with the human bcl-2 gene led to resistance to both exogenous and endogenous NO-mediated apoptosis. These data demonstrate that NO-mediated apoptosis can be suppressed by expression of Bcl-2, suggesting that abnormal expression of Bcl-2 may influence the efficacy of tumor immunotherapy.

Activation of nitric oxide synthase gene for inhibition of cancer metastasis

The process of cancer metastasis consists of multiple sequential and highly selective steps. The vast majority of tumor cells that enter the circulation die rapidly and only a few survive and proliferate to form distant metastases. This survival is not random. Metastases are clonal in origin and are produced by specialized subpopulations of cells that preexist in a heterogeneous primary tumor. Metastatic cells of the murine K-1735 melanoma survive in the circulation to produce experimental lung metastases, whereas nonmetastatic cells do not. After incubation with different cytokines or LPS, nonmetastatic cells exhibit a high level of inducible nitric oxide synthase (iNOS) activity and nitric oxide (NO) production, whereas metastatic cells do not. To provide direct evidence for the inverse correlation between the production of endogenous NO and the ability of K-1735 cells to produce metastasis in syngeneic mice, highly metastatic clone 4 cells (C4.P), which express low levels of iNOS, were transfected with a functional iNOS (C4.L8), inactive mutated iNOS (C4.S2), or neomycin resistance (C4.Neo) genes in medium containing 3 mM NMA. C4.P, C4.Neo3, and C4.S2.3 cells were highly metastatic, whereas C4.L8.5 cells were not. Moreover, C4.L8.5 cells produced slow-growing subcutaneous tumors in nude mice, whereas the other three cell lines produced fast-growing tumors. In vitro studies indicated that the expression of iNOS in C4.L8.5 cells was associated with apoptosis. Multiple intravenous injections of liposomes containing a synthetic lipopeptide upregulated iNOS expression in murine M5076 reticulum sarcoma cells growing as hepatic metastases. The induction of iNOS was associated with the complete regression of the lesions. Collectively, these data demonstrate that the expression of iNOS in tumor cells is associated with apoptosis, suppression of tumorigenicity, abrogation of metastasis, and regression of established hepatic metastases.

A cysteine proteinase, which cleaves human C3, the third component of complement, is involved in tumorigenicity and metastasis of human melanoma

The DM-4 human melanoma cell line, which is highly metastatic in nude mice, expresses a C3-cleaving activity that proteolyzes labeled as well as unlabeled human C3. This C3-cleaving activity is a cysteine proteinase characterized by a M(r) 41,000. The p41 proteinase shares antigenic determinants with murine p39 procathepsin-L and human procathepsin-L. Preincubation of DM-4 cells with anti-p39 F(ab')2 induced up to 45% decrease in their complement resistance. Pretreatment of DM-4 cells with anti-p39 Ab strongly inhibited their tumorigenicity and significantly decreased their metastatic potential in nude mice. Thus, the p41 C3-cleaving proteinase contributes to tumorigenicity and metastasis of human melanoma DM-4 cells.

Activation of inducible nitric oxide synthase gene in murine macrophages requires protein phosphatases 1 and 2A activities

The purpose of these studies was to identify phosphatase activities required for the production of nitric oxide in murine macrophages exposed to lipopolysaccharide (LPS), synthetic lipopeptide (LPP), and mouse interferon-gamma (IFN-gamma). The in vitro treatment of macrophages with IFN-gamma and LPS or IFN-gamma and LPP resulted in production of NO, which was inhibited by addition of the specific phosphatase 1 and 2A (PP1/2A) inhibitors okadaic acid (OA), calyculin A, and cantharidin (but not the nonactive analogues okadaic acid tetraacetate and 1,4-dimethylendothall). OA suppressed the accumulation of steady-state inducible NO synthase (iNOS) mRNA and iNOS protein (without alteration of their stability). The cytosol and nuclei of control macrophages contained large amounts of PP1/2A activities that were inhibited by OA in a dose-dependent manner. Taken together, these data indicate that PP1/2A activities are involved in the regulation of iNOS gene expression in murine macrophages.

Direct correlation between expression of endogenous inducible nitric oxide synthase and regression of M5076 reticulum cell sarcoma hepatic metastases in mice treated with liposomes containing lipopeptide CGP 31362

The purpose of this study was to determine whether the activation of inducible nitric oxide synthase (iNOS) can serve as a target for immunotherapeutic agents for treatment of murine reticulum cell sarcoma metastases. Liver metastases were established by the i.v. injection of M5076 cells into syngeneic C57BL/6 mice. Multiple systemic administrations of multilamellar vesicle-liposomes (MLV) containing the lipopeptide CGP 31362 (MLV-31362) or MLV-31362 combined with murine IFN-gamma eradicated the metastases. Tumor regression correlated with iNOS expression within the tumor lesions detected by Northern blot and immunohistochemistry techniques and with increased production of nitric oxide (NO). The administration of a specific iNOS inhibitor, NG-methyl-L-arginine, significantly decreased NO production and diminished the antitumor activities of the immunomodulators. Consistent with the regression of hepatic metastases, the combination of MLV-31362 and IFN-gamma synergistically induced iNOS gene expression, NO production, and apoptosis in the tumor cells under in vitro and in vivo conditions. The addition of NMA prevented the production of NO and apoptosis. These data imply that multiple systemic administrations of MLV-31362 plus IFN-gamma activate endogenous iNOS in sarcoma cells, which then undergo apoptosis, leading in turn to the regression of M5076 sarcoma hepatic metastases.

Neurotrophins promote maturation of developing neuromuscular synapses

Although the effects of neurotrophins on survival and differentiation of various neuronal populations have been well studied, little is known about their role in synaptic development and function. We have investigated the long-term effects of neurotrophins in the maturation of neuromuscular synapses in Xenopus nerve-muscle cocultures. BDNF and NT-3, but not NGF, elicited significant changes in several properties of spontaneous synaptic currents (SSCs), indicative of more mature synapses. Most synapses treated by the neurotrophins exhibited a bell-shaped distribution of SSC amplitudes, which reflects mature quantal secretion. The neurotrophins also potentiated the efficacy and reliability of stimulus-induced synaptic transmission. Moreover, BDNF and NT-3 increased the levels of the synaptic vesicle proteins, synaptophysin, and synapsin 1 in the spinal neurons. The number of varicosities per neuron also showed a significant increase after neurotrophin treatment. The effects of the neurotrophins appear to be mediated by the Trk family of receptor tyrosine kinases, primarily through a presynaptic mechanism. These results suggest that BDNF and NT-3 promote functional maturation of synapses.

Suppression of tumor growth and metastasis of murine renal adenocarcinoma by syngeneic fibroblasts genetically engineered to secrete the JE/MCP-1 cytokine

The murine monocyte chemoattractant protein 1, JE/MCP-1, like its human counterpart monocyte chemotactic and activating factor (MCAF), attracts monocytes-macrophages to tumor tissues. In previous studies we reported that expression of the JE/MCP-1 gene in murine colon carcinoma cells reduced their tumorigenicity and suppressed their metastatic potential. We now demonstrate that the growth and metastasis of the renal adenocarcinoma cell line RENCA are reduced when it was admixed with syngeneic fibroblasts engineered to secrete the JE/MCP-1 cytokine before injection. Culture supernatants of JE/MCP-1-expressing cells plus lipopolysaccharide (LPS) synergistically activated tumoricidal properties in syngeneic macrophages against RENCA cells. This activity was blocked by anti-JE/MCP-1 antibody, indicating that JE/MCP-1 was involved in priming the macrophages to respond to LPS. Moreover, alveolar macrophages isolated shortly after iv injections of JE/MCP-1 transfected cells were cytotoxic to RENCA cells in vitro. Collectively, these data suggest that in addition to its chemotactic properties, JE/MCP-1 can synergize with bacterial endotoxins to activate macrophages, thus providing a rationale for the use of the JE/MCP-1 protein as a modality for treatment of metastasis.

Regulation of interleukin-8 expression in human melanoma cells by the organ environment

The in vitro expression level of interleukin-8 (IL-8) correlates with the metastatic potential of human melanoma cells. The purpose of this study was to determine whether the expression level of IL-8 in human melanoma cells is influenced by the organ microenvironment. A375P cells, a low metastatic human melanoma, and A375SM cells, a highly metastatic variant, were injected into the subcutis (s.c.), spleen (to produce liver metastases), and lateral tail vein (to produce lung metastases) of athymic nude mice. Northern blot and immunohistochemical analyses determined that s.c. tumors, lung lesions, and liver lesions expressed high, intermediate, and low IL-8, mRNA, and protein, respectively. This differential regulation of IL-8 was not due to the size or density of the lesions or to selection of subpopulations of cells. We based this conclusion on the results of three experiments: (a) melanoma cell lines established in culture from in vivo-growing tumors exhibited similar levels of IL-8 mRNA transcripts; (b) in a crossover experiment, the level of IL-8 mRNA was always high in A375 tumors reestablished in the skin and low in the tumors reestablished in the liver, regardless of whether the melanoma cells had been first harvested from s.c. or liver tumors; and (c) A375 melanoma cells cocultured with human keratinocytes produced high levels of IL-8 protein, whereas A375 cells cocultured with highly differentiated human hepatoma cells produced decreased levels. When A375P cells were then incubated with cytokines associated with keratinocytes (IL-1 and interferon beta) or hepatocytes (transforming growth factor alpha or beta), IL-1 enhanced the production of IL-8 protein, whereas TGF-beta decreased its production. These data show that IL-8 expression in melanoma cells is modulated by local host factors.

Transfection with the inducible nitric oxide synthase gene suppresses tumorigenicity and abrogates metastasis by K-1735 murine melanoma cells

Previous studies from our laboratory demonstrated an inverse relationship between the expression level of inducible nitric oxide synthase (iNOS) and the metastatic potential of murine K-1735 melanoma cells. The purpose of this study was to provide direct evidence that the expression of iNOS suppresses metastatic potential of melanoma cells. Highly metastatic K-1735 clone 4 cells (C4.P), which express low levels of iNOS, were transfected with a functional iNOS (C4.L8), inactive-mutated iNOS (C4.S2), or neomycin-resistance (C4.Neo) genes in medium containing 3 mM NG-methyl-L-arginine (NMA). Positive transfectants were identified by Southern and Northern blot analyses and homogeneous staining with a specific anti-iNOS monoclonal antibody. Semiconfluent cultures of C4.P (parental), C4.Neo.3 (control transfection), C4.S2.3 (inactive iNOS), and C4.L8.5 (functional iNOS) were harvested, and viable cells were injected intravenously into syngeneic C3H/HeN mice and allogeneic BALB/c nude mice. C4.P, C4.Neo.3, and C4.S2.3 cells were highly metastatic whereas C4.L8.5 cells were not metastatic. Experiments with [125I]dUrd-labeled tumor cells demonstrated that the initial arrest in the lung microvasculature did not differ among the lines, but that C4.L8.5 cells died by 48-72 h after injection. Enhanced survival of all K-1735 C4 cells (including C4.L8.5) was found in mice given twice daily injections of 20 mg NMA. The C4.L8.5 cells produced slow growing subcutaneous tumors in nude mice, whereas the other three lines produced fast growing tumors. In vitro studies confirmed that in the absence of NMA the expression of iNOS in C4.L8.5 cells induced apoptosis. Collectively, these data demonstrate that the expression of recombinant iNOS in melanoma cells is associated with apoptosis, suppression of tumorigenicity, and abrogation of metastasis.

[Diagnosis and treatment of primary ureteral carcinoma--a report of 12 cases]

Twelve cases with primary ureteral carcinoma are reported with a review of literatures. Urography was the main method of diagnosis, and retrograde uretero-pyelography was more helpful. Cystoscopy was mandatory before operation. CT was useful for diagnosis and staging. If needed, ureteroscopy could be used to increase diagnostic accuracy. The traditional total nephroureterectomy with a cuff excision of the urinary bladder was the first and basic choice of treatment. Regular cystoscopy, excretory urography and adjuvant intravesical therapy should be carried out after operation.

Two short autoepitopes on the nuclear dot antigen are similar to epitopes encoded by the Epstein-Barr virus

To understand the relationship between antibodies present in patients with anti-nuclear dot (ND) autoimmune disease and the proteins they recognize, epitopes that react with the autoantibodies were mapped. A panel of fusion proteins containing different portions of the ND protein were overproduced in Escherichia coli. Immunoblot analysis with anti-ND antibodies revealed that most (10 of 12) sera recognize two major autoepitopes that are each a maximum of 8 amino acids long. The other two sera recognize one of the two epitopes. In addition to the short linear autoepitopes, a conformational epitope appears to be present on the ND antigen. Each of the two linear epitope sequences shares sequence similarities with those of several viral proteins found in the databases. Furthermore, two fusion proteins containing short Epstein-Barr virus (EBV) protein sequences that are similar to the ND epitopes were recognized by the human autoimmune sera, indicating that the autoepitopes are present in EBV protein sequences. Our results are consistent with the hypothesis that ND autoimmune disease might be associated with EBV infections.

Expression of the JE/MCP-1 gene suppresses metastatic potential in murine colon carcinoma cells

The purpose of this study was to determine whether the expression of the JE/MCP-1 gene encoding for the monocyte chemottractant protein, MCP-1 (also known as monocyte chemotactic and activating factor MCAF, TDCF, and SMC-CF) can influence the metastatic properties of tumor cells. The highly metastatic murine colon carcinoma CT-26 cells, syngeneic to BALB/c mice that do not produce endogenous JE/MCP-1 protein, were transfected with a BCMGS-Neo expression vector (control) or a vector containing full-length JE cDNA. CT-26 parental cells, CT-26 Neo, and CT-26 JE/MCP-1-positive cells were injected into syngeneic or nude mice. The CT-26 JE/MCP-1-positive cells produced significantly fewer lung metastases. The decrease in incidence of metastasis was not due to the inability of the transfected cells to arrest in the lung vasculature or to differences in cell cycle time. CT-26 cells producing JE/MCP-1 were highly susceptible to lysis by syngeneic macrophages treated with subthreshold concentrations of lipopolysaccharide. In addition, culture supernatants of JE/MCP-1-expressing cells plus lipopolysaccharide synergistically activated tumoricidal properties in syngeneic macrophages. This activity was blocked by anti-JE/MCP-1 antibodies, indicating the involvement of the JE/MCP-1 molecule in this process. Moreover, purified JE/MCP-1 added to lipopolysaccharide-containing medium resulted in significant activation of macrophages against parental CT-26 cells. These data suggest that, in addition to its chemotactic properties, JE/MCP-1 can synergize with bacterial endotoxins to activate macrophages to become tumoricidal and, hence, could suppress metastasis.

In vivo measurements of frequency-dependent attenuation in tumors of the liver

Ultrasonic frequency-dependent attenuation (FDA) coefficients of the liver obtained from selected regions of interest within the liver were determined in 106 individuals, 40 cases presumed normal based on medical histories and 66 with malignant tumors (hepatocellular carcinoma [HCC] or metastatic liver tumor) or benign tumors (hepatic hemangioma, hepatic adenoma, or focal nodular hyperplasia of the liver). All liver tumors were confirmed histopathologically by ultrasonically guided fine-needle biopsy and/or operation. Mean attenuation of normal liver was 0.53 +/- 0.03 dB/cm/MHz, 0.29 +/- 0.05 dB/cm/MHz in hepatic hemangioma, 0.43 +/- 0.05 dB/cm/MHz in HCC, and 0.41 +/- 0.12 dB/cm/MHz in metastatic liver tumor. Hepatic adenoma and focal nodular hyperplasia of the liver produced higher values, averaging 0.66 +/- 0.09 dB/cm/MHz. This difference between malignant and benign tumors was statistically significant. There was some correlation between the FDA for the hepatic tumor and the histopathology that merits further investigation.

Inverse correlation between expression of inducible nitric oxide synthase activity and production of metastasis in K-1735 murine melanoma cells

The purpose of these studies was to determine whether the induction of NO synthase activity in murine K-1735 melanoma cells correlated with their metastatic potential. Nonmetastatic, metastatic, and somatic cell hybrids (produced by fusion of nonmetastatic and metastatic cells) were injected i.v. into syngeneic C3H/HeN mice. Metastatic cells survived to produce experimental lung metastases, whereas nonmetastatic cells did not. The various clones and somatic cell hybrids were incubated in vitro with combinations of tumor necrosis factor, interleukin 1, gamma-interferon, and lipopolysaccharide. Nonmetastatic cells exhibited high levels of inducible NO synthase activity and NO, whereas metastatic cells did not. Both the cytotoxic effects of the cytokines and NO production were inhibited by the addition of NG-monomethyl-L-arginine, a specific inhibitor of NO synthase. These data demonstrate an inverse correlation between production of endogenous NO and the ability of K-1735 cells to survive in syngeneic mice to produce lung metastases.

Leukocyte-induced angiogenesis and subcutaneous growth of B16 melanoma

We investigated the mechanism(s) by which systemic administration of doxorubicin (DXR) produced growth retardation of B16 melanomas in the subcutis of syngeneic mice. DXR or saline was injected intravenously (i.v.) into C57BL/6 mice, and B16-BL6 cells were implanted subcutaneously (s.c.) on day 3, 7, or 21 after DXR treatment. In the DXR-pretreated mice, the tumors grew at a slower rate than in control (saline-treated) mice. The experiments were repeated with a B16 variant resistant to DXR with similar results. Tumor growth retardation correlated with extent of myelosuppression monitored by counting bone marrow cells, circulating leukocytes and peritoneal macrophages. In DXR-pretreated mice reconstituted with 1 x 10(7) viable syngeneic spleen cells, the s.c. tumors grew at a rate similar to that in control mice. DXR treatment and spleen cell reconstitution experiments were repeated in BALB/c athymic nude mice. The results were very similar. The growth of s.c. tumors was directly correlated with the degree of peritumoral vascularity. These data indicate that in addition to its well-documented direct antitumor effects, DXR may produce retardation of tumor growth by producing myelosuppression and, hence, inhibition of host cell-induced tumor angiogenesis.

Nuclear dot antigens may specify transcriptional domains in the nucleus

A bank of 892 human autoimmune serum samples was screened by indirect immunofluorescence on human tissue culture HT-29 cells. Seven serum samples that stain 4 to 10 bright dots in cell lines of several different mammals, including humans, monkeys, rats, and pigs, were identified. Immunofluorescence experiments indicate that these antigens, called nuclear dot (ND) antigens, are distinct from splicing complexes, kinetochores, and other known nuclear structures. An ND antigen recognized by these sera was cloned by immunoscreening a human lambda gt11 expression library. Analysis of seven cDNA clones for the ND antigen indicates that several mRNAs exist, perhaps derived through alternative splicing mechanisms. One major form of the message has an open reading frame of 1,440 bp capable of encoding a 53,000-M(r) protein. Treatment of cells with detergent, salt, or RNase A fails to remove the ND antigen from the nucleus. However, incubation with DNase I obliterates ND staining, indicating that the ND protein directly or indirectly associates with nuclear DNA. Fusion of the ND protein to a LexA DNA binding domain activates transcription in Saccharomyces cerevisiae. A 75-amino-acid domain that activates transcription in both yeast and primate cells has been identified. We suggest that ND antigens may participate in the activation of transcription of specific regions of the genome.

Protein tyrosine kinase inhibitors decrease induction of nitric oxide synthase activity in lipopolysaccharide-responsive and lipopolysaccharide-nonresponsive murine macrophages

We investigated tumoricidal activation and induction of nitric oxide synthase (NOS) activity in macrophages from LPS-responsive (C3H/HeN) and -unresponsive mice (C3H/HeJ). Macrophages were incubated in vitro with a synthetic lipopeptide or with LPS and IFN-gamma. LPS and IFN-gamma activated C3H/HeN but not C3H/HeJ macrophages to lyse B16 melanoma cells. In contrast, lipopeptide and IFN-gamma activated macrophages from both strains of mice. Genistein, a specific inhibitor of protein tyrosine kinase, significantly blocked tumoricidal activation of macrophages from both strains of mice. Genistein did not affect tumor cell binding but significantly inhibited the production of nitric oxide. Genistein, herbimycin A, and tyrphostin inhibited the induction of NOS activity in macrophages from both strains of mice. These data suggest that protein tyrosine kinase activity is involved in the signal transduction pathway of LPS and other synthetic bacterial-related immunomodulators at a point preceding triggering of macrophage tumoricidal activation and expression of inducible NOS activity.

Protein tyrosine kinase inhibitors decrease induction of nitric oxide synthase activity in lipopolysaccharide-responsive and lipopolysaccharide-nonresponsive murine macrophages

We investigated tumoricidal activation and induction of nitric oxide synthase (NOS) activity in macrophages from LPS-responsive (C3H/HeN) and -unresponsive mice (C3H/HeJ). Macrophages were incubated in vitro with a synthetic lipopeptide or with LPS and IFN-gamma. LPS and IFN-gamma activated C3H/HeN but not C3H/HeJ macrophages to lyse B16 melanoma cells. In contrast, lipopeptide and IFN-gamma activated macrophages from both strains of mice. Genistein, a specific inhibitor of protein tyrosine kinase, significantly blocked tumoricidal activation of macrophages from both strains of mice. Genistein did not affect tumor cell binding but significantly inhibited the production of nitric oxide. Genistein, herbimycin A, and tyrphostin inhibited the induction of NOS activity in macrophages from both strains of mice. These data suggest that protein tyrosine kinase activity is involved in the signal transduction pathway of LPS and other synthetic bacterial-related immunomodulators at a point preceding triggering of macrophage tumoricidal activation and expression of inducible NOS activity.