Macrophage-mediated inhibition of melanoma cell growth in nude mice

The effects of macrophages or sera from tumor-transplanted or control syngeneic and allogeneic mice on the latency and growth rate of P51 murine melanoma cells were determined after transplantation into congenitally athymic (nude) mice (tumor neutralization test). Syngeneic macrophages from tumor-bearing mice (TBM) inhibited melanoma growth in the nude mouse more than control macrophages, additionally macrophages from sensitized allogeneic mice inhibited melanoma growth to a greater degree than did allogeneic control macrophages. Sera from TBM inhibited melanoma growth as compared to control cells alone. Macrophages obtained after 14 days were also cytolytic towards the melanoma target in vitro. Despite the growth of large local masses, no evidence of distant metastases was found. The nude mouse thus provides an appropriate model for this tumor to portray in vivo immunotherapy.     

Modulation of human neuroblastoma transplanted into nude mice by endogenous opioid systems

The role of endogenous opioid systems (endogenous opioids and opioid receptors) in human cancer was explored using an opioid antagonist paradigm and neuroblastoma cells (SK-N-MC) transplanted into nude mice. Mice inoculated with 2.5 X 10(6) neuroblastoma cells received daily injections of either 0.1 or 10 mg/kg naltrexone (=0.1 and 10 NTX groups) which blocked the opioid receptor for 6-8 hr/day or the entire 24 hr/day, respectively, or sterile water. The latency for appearance of a measurable tumor (5 mm diameter) in the 0.1 NTX group was 27% longer than controls (11 days), and the first death in this group occurred 33% later than controls (day 27). Mice inoculated with tumor cells in the 10 NTX group had an acceleration (18%) in the latency of tumor appearance and, 2 weeks after cell inoculation, 70% of the mice in this group had tumors, in contrast to 10% of the controls. At the termination of the experiment (day 45), only 33% of the 10 NTX group were alive, in contrast to 90% of the controls. Receptor binding assays using DAGO, DADLE, or EKC revealed specific saturable binding only for DADLE and EKC. NTX administration resulted in a 148-186% increase in density for both binding sites, but no changes in binding affinity. Measures of opioid levels showed that tumor tissue levels of both beta-endorphin and methionine-enkephalin were elevated 2.5 to 6.5 fold from control values in both NTX groups, whereas plasma beta-endorphin was subnormal by 4 to 6 fold. These results indicate that endogenous opioid systems regulate human neuro-oncogenesis, with opioids being active inhibitors of growth. Opioid antagonists up-regulate receptors and increase tissue levels of endogenous opioids and, under conditions in which the opioid antagonist is short-acting (e.g., 0.1 NTX), can have an exaggerated antitumor effect during the interval when the antagonist is no longer present.     

Enzymic composition and growth rate of human pleural mesothelioma transplants in nude mice.

The enzymic composition of 7 human mesothelioma lines propagated in nude mice was compared with 4 of the original and 15 additional mesotheliomas sampled during the patients' surgery. The xenografts exhibited several-fold higher thymidine kinase (TK), uridine kinase (UK), phosphoserine phosphatase (PSP) and peptidyl proline hydroxylase (PPH) concentrations than the fresh human samples, while their DNA, gamma-glutamyl transpeptidase (GGT) and beta-galactosidase (Bgal) contents remained similar. The volume growth rate of the xenografts (doubling time, DT = 9.23 +/- 1.25 days) was much faster than that of tumors in the human host, and the decline of this rate with increasing nodule size was accompanied by decreases in TK and PSP concentrations. This first quantitative biochemical study of xenografted human neoplasms indicates that 1) pleural mesotheliomas, though preserving their histological characteristics after heterotransplantation, show considerable increases of enzymes in nucleic acid, collagen, and nonessential amino acid synthesis, and that 2) the concentration of TK is a good indicator of the different growth properties of tumors in a mouse rather than in the human host.     

A flavivirus protein M-derived peptide directly permeabilizes mitochondrial membranes, triggers cell death and reduces human tumor growth in nude mice

Dengue viruses belong to the Flavivirus family and are responsible for hemorrhagic fever in Human. Dengue virus infection triggers apoptosis especially through the expression of the small membrane (M) protein. Using isolated mitochondria, we found that synthetic peptides containing the C-terminus part of the M ectodomain caused apoptosis-related mitochondrial membrane permeabilization (MMP) events. These events include matrix swelling and the dissipation of the mitochondrial transmembrane potential (ΔΨ_m). Protein M Flavivirus sequence alignments and helical wheel projections reveal a conserved distribution of charged residues. Moreover, when combined to the cell penetrating HIV-1 Tat peptide transduction domain (Tat-PTD), this sequence triggers a caspase-dependent cell death associated with ΔΨ_m loss and cytochrome c release. Mutational approaches coupled to functional screening on isolated mitochondria resulted in the selection of a protein M derived sequence containing nine residues with potent MMP-inducing properties on isolated mitochondria. A chimeric peptide composed of a Tat-PTD linked to the 9-mer entity triggers MMP and cell death. Finally, local administration of this chimeric peptide induces growth inhibition of xenograft prostate PC3 tumors in immuno-compromised mice, and significantly enhances animal survival. Together, these findings support the notion of using viral genomes as valuable sources to discover mitochondria-targeted sequences that may lead to the development of new anticancer compounds.     

Intracranial growth of pulmonary small cell carcinoma cells in nude athymic mice

Pulmonary small cell carcinoma of the lung cells were inoculated intracranially and subdermally in nude athymic mice (Balb/c strain). There was a 100% intracranial tumor incidence in response to 1/10th the cell dose required to produce subdermal tumors in immunosuppressed nude mice. Tumors did not grow in the brains of Balb/c normal (haired) mice.     

Toxicity of anticancer agents, growth and chemosensitivity of human tumour xenografts in a segregating stock of AF nude mice.

An investigation of the usefulness of a segregating stock of nude mice [AF nude mice (AF-nu)] for screening anticancer agents was undertaken. The toxicity of anticancer agents, takes and growth rates of human tumour xenografts and chemosensitivities of xenografts in AF-nu were studied and compared with those in BALB/cA nude mice (BALB/cA-nu). The results showed differences in the pattern of mortalities of AF-nu and BALB/cA-nu administered a range of anticancer agents. Body weight changes in the two nude mouse strains differed in the case of 5-fluorouracil, but not for nimustine, adriamycin and vincristine. All tumours transplanted in AF-nu grew as in BALB/cA-nu. Growth rates of 2 xenografts (gastric cancer and glioblastoma) were not significantly different between the 2 nude mouse strains, but those of 2 lung tumour xenografts were significantly greater in AF-nu than those in BALB/cA-nu. There were no significant differences in chemosensitivities of human tumours in AF-nu and BALB/cA-nu (consistency rate as evaluated by our criteria was 88%). From these results, it is suggested that AF-nu are more suitable for anticancer agent screening and experimental chemotherapy of human tumour xenografts than BALB/cA-nu because of lower costs and high reproductive rate. Although they are genetically heterogeneous, sets of experimental animals sharing the same gene pool can be produced routinely.     

Nerve growth factor-induced differentiation of human neuroblastoma and neuroepithelioma cell lines

A series of neuroepithelioma and neuroblastoma cell lines were screened for nerve growth factor (NGF)-induced differentiation. All three neuroepithelioma cell lines and all nine neuroblastoma cell lines with amplified N-myc oncogene did not show any apparent NGF-induced differentiation. However, neurite extension was observed for three of six neuroblastoma cell lines with single-copy N-myc oncogene. The three responsive lines had a neuronal phenotype (short processes) which was enhanced by the addition of NGF. The three nonresponsive cell lines were flat without any processes. The addition of NGF to the responsive cell lines resulted in an up-regulation of neurofilament mRNA expression. Peripherin and synapsin, two markers of terminal neuronal differentiation, were not induced. There was little effect of NGF on the rate of cell growth or colony formation on soft agar. Binding of NGF to eight of the cell lines was analyzed by the method of Scatchard. Two responsive neuroblastoma cell lines and one nonresponsive neuroepithelioma cell line expressed both low- and high-affinity binding sites. Two nonresponsive neuroblastoma cell lines expressed only a small number of high-affinity binding sites, and two other nonresponsive neuroblastoma cell lines did not detectably bind NGF. Hence, NGF-induced differentiation is confined to a particular class of neural-related tumors, and, even for these cell lines, differentiation is incomplete.     

Establishment of human colon carcinoma lines in nude mice.

After subcutaneous inoculation into nude mice of 24 human colon adenocarcinomas, growth, defined as histopathologically confirmed tumor growth which has been passed, was observed in 13 cases (54%). Tumors from metastatic sites showed higher take rates (58%) than tumors from primary sites or recurrent tumors (50%). Nine continuous tumor lines were established (69% of growing tumors) with metastatic tumors establishing more readily (100% of growing tumors) than primary tumors (40%). The average period in primary transplant was shorter for metastasis (8.3 weeks), than for primary tumors (18.5 weeks); total material 10.6 weeks. Average periods between passages were shorter than primary transplant times; these periods were shorter for metastases (6.6 weeks) than for primary tumors (9.4 weeks); total material 7.4 weeks. Of four growing tumors not established as continuous lines, three were primary and one a recurrent tumor, and the loss of tumor growth occurred in very early passages, not later than passage 3. All nude mouse-grown colon tumors were moderately well differentiated.     

Effect of melphalan on growth curves and cell cycle distribution of four human small cell carcinomas of the lung grown in nude mice

Four human small cell carcinomas of the lung grown in nude mice were exposed to melphalan. Two of the tumors were derived from subpopulations isolated by in vitro cloning from the same tumor biopsy. The chemosensitivity of the tumors was determined by calculating the specific growth delay. Drug-induced changes in the cell cycle were detected by flow cytometric DNA analysis. The specific growth delay of the tumors was very different with the greatest differences between the two subpopulations originating from the same tumor. Melphalan induced a dose-related S phase accumulation in three sensitive tumors, whereas no changes were seen in a resistant tumor. Furthermore, the amount of S phase accumulation reflected the sensitivity to melphalan. The results suggest that heterogeneity in chemosensitivity is an important reason for chemotherapy failures.     

Cellular tumorigenicity in nude mice: correlation with cell growth in semi-solid medium

Cultured cells derived from either normal or malignant tissues of several species have been tested by injection into the immune-deficient nude mouse in order to determine the cellular properties which are associated with tumorigenicity in vivo. Results show that one in vitro property consistently correlated with neoplastic growth in nude mice is the ability of the cell to form spherical colonies in a semi-solid growth medium such as methyl cellulose suspension. Cellular tumorigenicity is not determined solely by the malignancy of the tissue of origin, since cells derived from nonmalignant tissues become tumorigenic when they are no longer anchorage dependent for growth. In addition, acquisition of infinite growth potential in heteropioid cell lines is not in itself sufficient to confer tumorigenic capacity on the cells. These results suggest that the degree of cell growth in methyl cellulose is a useful parameter in vitro for predicting tumorigenicity in the animal, and also demonstrate the potential usefulness of the nude mouse for analysis of cellular malignancy irrespective of the tissue or species of origin.     

Down-regulation of IGF-IR using small, interfering, hairpin RNA (siRNA) inhibits growth of human lung cancer cell line A549 in vitro and in nude mice

Type I insulin-like growth factor receptor (IGF-IR), which is frequently overexpressed in a variety of human cancers including lung cancer, mediates cancer cell proliferation and tumor growth. In this study, we used a human U6 promoter-driven DNA-template approach to induce hairpin RNA (hpRNA)-triggered RNAi to silence IGF-IR gene expression in the human lung cancer cell line A549, and then evaluate its effects on apoptosis, apoptosis-related gene expression, and the growth of tumor cells in vitro and in nude mice. IGF-IR expression levels were found to markedly decrease in cells transfected with a plasmid expressing hairpin siRNA for IGF-IR (by more than 78.9%). Down-regulation of IGR-IR concomitantly accompanied reduction of bcl-2 as well as pERK and pAkt levels, activation of caspase-3, apoptosis and growth inhibition of A549 cells in vitro. Direct intratumoral injections of plasmid DNA expressing hpRNA for IGF-IR significantly regressed pre-established tumors in nude mice. Our results support the therapeutic potential of RNAi as a method for gene therapy in treating lung cancer.     

Extrathymic T cell maturation. Phenotypic analysis of T cell subsets in nude mice as a function of age.

T cell maturation in an extrathymic environment has been studied using as a model the congenitally athymic nude mouse. Phenotypic analyses as a function of age were conducted on lymphocytes obtained from the spleens and lymph nodes of nude mice through use of mAb recognizing T cell surface markers and multiparameter flow cytometry. The data show that nude mice accumulate increasing numbers of lymphocytes bearing Thy-1, CD3, CD4, and CD8 with age characterized by a progression from heterogeneous dim to more homogeneous bright expression. In contrast, the expression of heat-stable Ag (HSA), a marker of immature thymocytes, decreases with age. By analogy to intrathymic maturation, spleens and lymph nodes in nude mice contain T cells defined as immature, transitional, and mature based on the expression of these markers. Although the proportion of CD4+ and CD8+ T cells associated with bright CD3 expression increases with age, at no age are significant numbers of CD4+8+ cells observed, in contrast to intrathymic T cell maturation. In addition to the frequently observed inversion in the ratio of CD4 to CD8, the CD8 T cell subpopulation in older nude mice contains mainly mature cells (CD8+, CD3+, HSA-) whereas only 50% of CD4+ T cells express the mature (CD4+, CD3+, HSA-) phenotype. At any age, the spectrum of phenotypes observed indicates that lymph nodes contain more mature T cells than spleen, suggesting a role for environmental Ag in driving extrathymic maturation, a process occurring most efficiently among CD8+ T cells. Because extrathymic maturation mirrors some but not all aspects of the intrathymic pathway, we propose that the nude mouse may be a useful model for further dissecting those interactions crucial to establishing the T cell repertoire in euthymic individuals as well as elucidating the contribution of extrathymically derived T cells to the peripheral immune system.     

Secretion of ceruloplasmin by a human clear cell carcinoma maintained in nude mice

Ceruloplasmin is the best known but least understood copper protein. Studies preliminary to investigating the control of ceruloplasmin synthesis have utilized a human renal cell carcinoma maintained in nude mice for 73 passages over a 5-year period. In vitro cultures of these cells were accomplished and the mRNAs were extracted prior to microinjection into Xenopus oocytes. The media examined by SE-HPLC and immunological techniques demonstrated that (1) after in vitro culture, ceruloplasmin was secreted as an uncleaved polypeptide chain with a MW of 135,000; (2) the translational product of ceruloplasmin mRNA injected into Xenopus oocytes was cleaved into fragments with MWs of 110,000, 67,000, and 50,000. The results indicate that mRNA for human ceruloplasmin can be obtained to serve as a template for the synthesis of a cDNA probe to investigate the control of human ceruloplasmin's synthesis.     

Isatin, an endogenous monoamine oxidase inhibitor, triggers a dose- and time-dependent switch from apoptosis to necrosis in human neuroblastoma cells

Isatin is an endogenous indole that is increased in stress, inhibits monoamine oxidase (MAO) B and improves bradykinesia and striatal dopamine levels in rat models of Parkinson's disease. Consequently, it has been suggested that isatin might be a possible treatment for Parkinson's disease although little is known about its effects on neural cell growth and survival. The aim of this study was to investigate the survival of dopaminergic human neuroblastoma (SH-SY5Y) cells following treatment with increasing concentrations of isatin. SH-SY5Y cells were exposed to isatin for defined time points, after which cell survival was determined by MTT assay. A combination of Annexin V binding and propidium iodide (PI) exclusion was used to distinguish apoptosis from necrosis in flow cytometry experiments and FACS profiles of permeabilised PI-labelled cells were employed for the assessment of cell cycle distribution. Isatin treatment (1-400 microM) for 24h induced a significant dose-dependent increase in MTT metabolism by SH-SY5Y cells in culture, but this was not due to an increase in cell division. At the higher concentrations (200-400 microm) isatin triggered cell death, although MTT metabolism was still increased in the culture, suggesting that surviving cells were hypermetabolic. Following a longer (48 h) exposure, isatin was found to cause cell death in a dose-dependent manner; at lower concentrations (50 microM), the predominant mode of cell death was apoptosis while at the highest concentration (400 microm) increasing numbers of necrotic cells were also evident. Thus, in dopaminergic SH-SY5Y cells isatin induces cell death in dose- and time-dependent manner. This death occurred as a continuum of survival, apoptosis and necrosis. Our results re-emphasise that caution should be exercised when considering high doses of isatin as a putative anti-Parkinson's disease therapeutic.     

Down-regulation of endothelial cell growth inhibitors by enhanced MYCN oncogene expression in human neuroblastoma cells.

Recent evidence indicates that the genetic alterations of the multistage process of malignant transformation appear to activate tumor neovascularization by altering the balance between stimulators and inhibitors of angiogenesis. In the present study, we have attempted to define the effect of enhanced MYCN oncogene expression on the profile of endothelial cell growth modulators in neuroblastoma cells. We report here that conditioned medium of human neuroblastoma cells with normal MYCN expression contains three inhibitors of endothelial cell proliferation, which appear to be novel proteins as judged by their physicochemical, immunological and biological properties. All three inhibitors are diminished or become undetectable upon experimental increase of MYCN expression. Our results suggest that enhanced MYCN expression in human neuroblastoma cells alters the angiogenic balance by down-regulating endothelial cell growth inhibitors but leaving the expression of the stimulators unaffected. These data shed light on the molecular mechanisms linking the genetic changes of malignant transformation with initiation of tumor angiogenesis. Moreover, our observations might explain the poor prognosis of human neuroblastomas following MYCN oncogene amplification through initiation of angiogenesis and subsequent tumor growth and spread.     

Induction of lymphomas on implantation of human oral squamous cell carcinomas in nude mice

Cancer cells from five oral cancer patients and pleomorphic adenoma cells from one individual were inoculated as single cell suspension into subcutis of 30 Swiss nude mice and tail vein of additional 30 mice. Further, tumor tissue pieces from three oral cancer patients were xenografted s.c. in 18 nude mice, and 10 mice were kept as controls. In animals implanted with tumor pieces, 7/18 (39%) mice, developed squamous cell carcinoma at the site of inoculation within 8-15 days, while tumors were not observed in mice inoculated with single cell suspension, up to 60/90 days. In 8/68 (12%) mice, white foci were observed in several tissues, with hepatomegaly and splenomegaly noted in 27/68 (39%) mice. Histopathological examination of various tissues revealed presence of large cell lymphoma in several organs in 14/68 (21%) mice. No regional or distant metastasis of the implanted oral tumor cells was detected. Mice injected with cells from pleomorphic adenoma, also demonstrated large cell lymphoma in 2/10 (20%) mice, whereas none of the 10 control animals showed any gross abnormalities or microscopic abnormalities in several organs. 2/16 (12%) lymphomas exhibited positive reaction with mouse B cell antibodies illustrating the murine origin of the lymphomas, and these were immunophenotyed as B cell lymphomas. The lymphomas were also examined with mouse T cell antibodies and none reacted positively with the mouse T cell antibodies. The lymphomas also failed to react with human T cell, B cell and human Leucocyte common antigen (LCA) antibodies, indicating that the induced lymphomas were not of human origin. The tumor specimens from seven of eight oral cancer patients and the pleomorphic adenoma patient induced lymphomas in nude mice. Thus it appears that xenografting oral tumor cells into nude mice may cause induction of the murine lymphomas, and this needs further investigation.