Differential hypersensitivity of xeroderma pigmentosum lymphoblastoid cell lines to ultraviolet light inutagenesis

Survival and mutation after u.v. light irradiation were examinedin four human lymphoblastoid cell lines; one cell line withnormal excision-repair capacity (HH4), two excision-repair-deficientxeroderma pigmentosum (XP) cell lines from patient XP3BE (complementationgroup C) and XP7NI (group A), and one cell line from an XP heterozygote(XPF7NI, father of XP7NI). Relative to HH4 and XPF7NI, bothXP3BE and XP7NI were more sensitive to the cytotoxic effectof u.v. by virtue of a diminished shoulder and a steeper slopein the survival curve determined by growth curve ex trapolations.The mutagenesis for 6-thioguanine resistance (TG^r) was measuredby the limiting dilution technique using 96 well microtiterplates. Even at non-cytotoxic fluences, u.v. light induced TG^rmutations in HH4 and XPF7NI with no apparent threshold, andthe mutagenic response of XPF7NI was no different than thatof HH4. Both XP cell lines were more sensitive than normal cellsto u.v.-induced mutation. However, XP7NI cells were extremelyhypermutable by u.v.; i.e. 3.3 J/m² induced an {small tilde}500-foldincrease of mutant fraction with the background of 2x10^–6.XP7NI cells remained much more mutable by u.v. even when plottedagainst survival, whereas the mutant fractions for XP3BE andHH4 followed the same line. These results imply that the mechanismof u.v.-induced mutation in XP7NI cells may in trinsically bedifferent from that in XP3BE, XP heterozygote or normal cells,or that potentially mutagenic lesions are repaired much lessefficiently in XP7NI cells than are potentially lethal lesions,as compared with XP3BE, XPF7NI and HH4 cells.     

Gap junction expression following UVC-induced neoplastic transformation in human hybrid cell lines

Decreased connexin gene expression and loss of the capacity for either homologous or heterologous intercellular communication has been associated with neoplastic transformation. We tested the hypothesis that loss of gap junctional intercellular communication (GJIC) correlates with tumorigenic potential in the HeLa x skin fibroblast human hybrid cell system. Connexin gene expression, gap junction function and tumorigenicity were determined for the non-tumorigenic somatic hybrid cell line (CGL1) and a series of UVC-induced tumorigenic cell lines derived from CGL1. CGL1 and the parental skin fibroblasts express connexin43 (alpha1 gap junction gene) mRNA and protein, form gap junctional plaques and have functional gap junctions. UVC- irradiation of CGL1 cells produced a cell line (UV12) with an aggressive tumorigenic phenotype, which lost connexin43 expression as well as both homologous and heterologous GJIC and was in this respect similar to HeLa cells. However, the phenotype of UV12 cells exhibited some instability and revertants to a less aggressive tumorigenic phenotype were isolated. These cells expressed connexin43 mRNA and protein, and demonstrated homologous GJIC. Furthermore, cells reconstituted from a tumor derived from this revertant cell line retained significant connexin43 expression and homologous GJIC, although they exhibited an aggressive tumorigenic phenotype. Thus, functional homologous GJIC cannot be dissociated from tumorigenicity in this system. However, heterologous GJIC between these same UVC-induced tumorigenic cell lines and normal human skin fibroblasts was reduced, whereas the non-tumorigenic hybrid cells showed extensive heterologous GJIC. In summary, re-acquisition of connexin43 expression and homologous GJIC does not restore the non-tumorigenic phenotype in UVC- induced tumorigenic HeLa skin fibroblast human hybrid cells. However, reduction of heterologous GJIC does correlate with tumorigenicity in this cell system.      

Tumorigenicity of human HT1080 fibrosarcoma X normal fibroblast hybrids: chromosome dosage dependency

The tumorigenic capacity of hybrids formed by fusion of the highly tumorigenic HT1080 human fibrosarcoma cell line with nontumorigenic normal fibroblasts was examined. The HT1080 also contains an activated N-ras oncogene. Near-tetraploid hybrids which contained an approximately complete chromosomal complement from both parental cells were nontumorigenic when 1 X 10(7) cells were injected s.c. into athymic (nude) mice, whereas the parental HT1080 cells produced tumors in 100% of the animals with no latency period following injection of 2 X 10(6) cells. Tumorigenic variants were obtained from these hybrids which had lost only a few chromosomes compared to cells from the nontumorigenic mass cultures. In addition, several near-hexaploid hybrids were obtained which contained approximately a double chromosomal complement from the HT1080 parental line and a single chromosomal complement from the normal fibroblasts. All of these near-hexaploid hybrids produce tumors in 100% of nude mice with no latency period. Our results indicate that tumorigenicity of these particular human malignant cells of mesenchymal origin can be suppressed when fused with normal diploid fibroblasts. In addition, the results suggest that tumorigenicity in this system is chromosomal dosage dependent, since a diploid chromosomal complement from normal fibroblasts is capable of suppressing the tumorigenicity of a near-diploid but not a near-tetraploid chromosomal complement from the tumorigenic HT1080 parent. Finally, the loss of chromosome 1 (the chromosome to which the N-ras oncogene has been assigned) as well as chromosome 4 was correlated with the reappearance of tumorigenicity in the rare variant populations from otherwise nontumorigenic near-tetraploid hybrid cultures. Our results also suggest the possibility that tumorigenicity in these hybrids may be a gene dosage effect involving the number of activated N-ras genes in the hybrids compared to the gene(s) controlling the suppression of the activated N-ras genes.     

Over-expression of hsp70 confers tumorigenicity to mouse fibrosarcoma cells

Over-expression of the major heat-shock protein hsp70 in WEHI-S tumor cells renders them resistant to the cytotoxic effects of tumor necrosis factor (TNF). To study the significance of this resistance in vivo, the tumorigenic potential of WEHI-S cells transfected with human hsp70 in sense and anti-sense orientation was investigated in athymic and in normal syngenic mice. A striking correlation was observed between the level of hsp70 expression and tumorigenicity in athymic mice. Hsp70 expression rendered WEHI cells tumorigenic also in normal mice, but higher numbers of cells were required for tumor formation than in athymic mice. Over-expression of hsp70 in WEHI-S cells did not enhance their anchorage-dependent growth in vitro or their ability to form colonies in soft agar. The hsp70-transfected cells exhibited greatly increased resistance against killing by murine natural cytotoxic cells and macrophages in vitro. A similar tumorigenic phenotype could also be induced independently of hsp70 by prolonged culture of WEHI-S cells with TNF. These results suggest that over-expression of hsp70 increases the tumorigenic potential of WEHI-S cells in mice, by allowing these cells to escape from the early TNF-mediated anti-tumor immune surveillance.     

Induction of cells with acinar cell phenotype including presence of intracellular amylase. Treatment with 12-O-tetradecanoyl-phorbol-13-acetate in a neoplastic human salivary intercalated duct cell line grown in athymic nude mice

The adenocarcinoma produced by transplantation into nude mice of a neoplastic human salivary intercalated duct cell line was treated with 0.1 ml of minimal essential medium (MEM) containing 12-O-tetradecanoyl-phorbol-13-acetate (TPA) at a final concentration of 10(-7) mol/l daily for 28 days and examined morphologically and immunohistochemically. The TPA treatment resulted in an enhancement of tumor growth. In addition, tumor cells containing secretory granules positively reactive to antiamylase serum were observed in the treated tumors, but not in untreated controls. These findings lead us to suggest that neoplastic intercalated duct cells treated with TPA can be induced to differentiate into acinar cells in heterotransplanted athymic nude mice.     

Intracranial heterotransplantation of human hematopoietic cells in nude mice.

A panel of established cell lines and many primary cell specimens from lymphomas and leukemias as well as from normal lymphatic tissues were tested for tumorigenicity by intracranial heterotransplantation in nude mice. Not only lymphoma and leukemia cell lines, but also lymphoblastoid cell lines, lacking markers of malignancy, were tumorigenic in the brains of nude mice. These findings indicate that tumorigenicity following intracranial heterotransplantation in nude mice cannot be used as proof for the malignant nature of established cell lines. Heterotraplantation of primary cell specimens yielded only a few tumor takes. When primary cells were infected with exogenous Epstein-Barr virus prior to the transplantation procedure, tumorigenicity could be significantly increased. Cytogenetic evaluation of tumors growing after intracranial transplantation of human hematopoietic cells showed, in some cases, a selection of cytogenetically aberrant cell clones.     

Effect of differentiation inducers on growth characteristics of human glioma cell lines

Summary The effect of dimethylsulfoxide (DMSO) and iododeoxyuridine (IUdR) on the growth characteristics of two established human glioblastoma cell lines (FG and HMCN-1) was studied. The FG cell line has been characterized. The HMCN-1 cell line, established in our laboratory, consisted of fibroblastoid and polygonal cells that grew without contact inhibition. Subcutaneous injection of these cells into weanling athymic nude mice induced slowly growing, solid tumors that were histologically spindly with areas that were similar to the original tumor. Chromosomal analyses revealed a human heteroploid pattern with a modal number of 69. The cells of the original human glioma contained S-100 protein and glial fibrillary acidic protein (GFA protein), whereas the established cells failed to express markers. Prolonged treatment of glioma cells with DMSO generated a more adherent, normal human fibroblastoid phenotype that grew with contact inhibition. The new phenotype and proliferative restriction of these cells was evident as late as 50 days after discontinuation of treatment. The chemical induction of cell differentiation resulted in decreased tumorigenic potential in athymic nude mice.     

Interleukin 8 expression regulates tumorigenicity and metastasis in human bladder cancer

Interleukin 8 (IL-8) is mitogenic and chemotactic for endothelial cells. Within a neoplasm, IL-8 is secreted by inflammatory and neoplastic cells. The highly tumorigenic and highly metastatic human transitional cell carcinoma (TCC) cell line 253J B-V overexpresses IL-8 relative to the nontumorigenic and nometastatic 253J-P cell line. To determine whether IL-8 expression regulates tumorigenicity and metastasis in human TCC, 253J B-V cells were transfected with the full-sequence antisense (AS) cDNA for IL-8, whereas 253J-P cells were transfected with the full-length IL-8 cDNA, and control cells for each were transfected with the neomycin resistance (Neo) gene. In vitro, sense-transfected 253J-P cells overexpressed IL-8-specific mRNA and protein, whereas both of these were markedly reduced in AS-IL-8-transfected 253J B-V cells relative to controls. Moreover, sense-transfected cells showed up-regulation in matrix metalloproteinase type 9 mRNA, collagenase activity, and increased invasiveness through Matrigel-coated filters, whereas these measures were lower in AS-transfected cells relative to controls. After implantation into the bladders of athymic nude mice, the sense-transfected 253J-P cells acquired increased tumorigenicity and metastasis, whereas the AS-transfected cells significantly inhibited tumorigenicity and metastases in the 253J B-V cell lines. This effect was accompanied by reduced IL-8 expression and microvessel density. These studies demonstrate that IL-8 expression enhances angiogenic activity through the induction of matrix metalloproteinase type 9 and subsequently regulates the tumorigenesis and production of spontaneous metastases of human TCC.     

Anti-tumor surveillance of non-contact-inhibited transformed cell lines

In order to determine if the correlated expression of transformation and tumorigenicity is affected by the agents used to induce transformants or by the immune status of the host used to test the tumorigenicity of transformants, we derived a series of cloned cell lines from foci of transformed cells induced by treatment of the contact-inhibited mouse cell line B/C-N7.ICI with the DNA demethylating agent 5-azacytidine (5-AZC) or the DNA demethylating and mutating agent benzo(a)pyrene dihydrodiol epoxide (BPDE). The transformed cell lines were injected into syngeneic nude and normal mice to determine their tumorigenicity. The results of this analysis showed that 93% of the transformants induced by 5-AZC treatment grew as tumors when injected into nude mice. Of those lines capable of growing as tumors in nude mice, 86% were also tumorigenic when injected into normal mice. In contrast, only 64% of BPDE-induced transformants grew as tumors in nude mice, and of those, only 44% were also tumorigenic in normal mice. The existence of non-contact-inhibited transformants that are tumorigenic only in nude mice indicates that host anti-tumor immune surveillance mechanisms are operative in normal mice. Further, the difference in both the percentage of transformed cell lines that are tumorigenic and the percentage of tumorigenic transformants that are susceptible to immune surveillance when transformants are induced by BPDE as compared to 5-AZC indicates that the transforming agent can affect both the correlation between the expression of transformation and tumorigenicity, and the interaction between the immune system and tumorigenic transformants.     

Inhibition of tumorigenicity and metastasis of human bladder cancer growing in athymic mice by interferon-beta gene therapy results partially from various antiangiogenic effects including endothelial cell apoptosis.

We determined whether the IFN-beta gene could suppress angiogenesis, tumor growth, and metastasis of human bladder transitional cell carcinoma. The highly tumorigenic and metastatic 253J B-V(R) human bladder transitional cell carcinoma (TCC) cell line (resistant to the antiproliferative effects of IFN-beta) was infected in vitro with adenoviral beta-galactosidase (Ad-LacZ), murine adenoviral IFN-beta (Ad-mIFN-beta), or human adenoviral IFN-beta (Ad-hIFN-beta) and implanted into the bladders of athymic nude mice. Ad-mIFN-beta and Ad-hIFN-beta were used because of the species specificity of IFN-beta. The transient production of mIFN-beta and hIFN-beta from the infected 253JB-V(R) tumor cells significantly inhibited tumorigenicity and spontaneous lymph node metastasis. Subsequently, the 253J B-V(R) cells were implanted into the subcutis of athymic nude mice, and established tumors were treated by direct intratumoral injection with Ad-mIFN-beta, Ad-hIFN-beta, Ad-LacZ, or PBS. By in situ hybridization (ISH) and immunohistochemical analysis (IHC), expression of hIFN-beta and mIFN-beta mRNA and protein within the tumors was demonstrated after Ad-hIFN-beta and Ad-mIFN-beta gene therapy, respectively. The therapy also induced necrosis in both the Ad-mIFN-beta- and Ad-hIFN-beta-treated tumors. IHC revealed decreased tumor cell proliferation and the sequestration of activated macrophages within the tumors after Ad-mIFN-beta therapy. In addition, the expression of the proangiogenic factors bFGF, and MMP-9 protein (by IHC) was significantly down-regulated by Ad-hIFN-beta gene therapy. Double-immunofluorescent IHC for terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL) and CD-31 demonstrated tumor and endothelial cell apoptosis in those tumors treated with Ad-hIFN-beta gene therapy. Tumor-induced angiogenesis, as determined by the microvessel density, was decreased in tumors treated with both Ad-mIFN-beta and Ad-hIFN-beta. These data suggest that the inhibition of tumorigenicity and the metastasis of the 253J B-V(R) cells after infection with Ad-IFN-beta is caused by the inhibition of angiogenesis and the activation of host effector cells.     

Tumorigenicity of the cyc- variant of the S49 murine lymphoma deficient in the Gs-alpha subunit of adenylate cyclase

S49 cyc- lymphoma cells contain a mutation resulting in loss of a functional guanine nucleotide regulatory protein rendering their adenylate cyclase refractory to most stimuli. S49 wild-type and cyc- clones were used in the present study to investigate the possible association of altered cAMP metabolism with tumorigenicity and metastatic potential. The S49 clones were implanted i.v., i.p., and intracerebrally in both athymic nude mice and syngeneic, immunocompetent BALB/c mice. Both S49 clones gave rise to tumors when inoculated into athymic mice, and no differences were observed in the tumorigenicity or metastatic potential of S49 wild-type and cyc- cells. Implantation of S49 clones in syngeneic BALB/c mice gave rise to few tumors except when administered intracerebrally, where wild-type cells were more tumorigenic than cyc- cells. This raises the possibility of differences in immunogenicity between the S49 clones. Analysis of cell lines derived from tumors grown in athymic mice showed that they retained the phenotype of the S49 clones used for inoculations. The results indicate that, despite differences in adenylate cyclase responsiveness, S49 wild-type and cyc- cells are both highly tumorigenic and metastatic.     

Homogeneously staining regions and tumorigenicity

A homogeneously staining region (HSR), a chromosome abnormality associated with gene amplification, was found to increase in length coincident with an enhancement in tumorigenicity when cells from a human retinoblastoma cell line were serially passaged in athymic (nu/nu) mice.     

Relationship between tumorigenicity,in vitro invasiveness,and plasminogen activator production of human breast cell lines

Two human breast epithelial cell lines (HBL-100, HMT-3522) of non-malignant origin and six (MCF-7, T47-D, ZR-75-1, CAMA-1, BT-20, HMT-3909) of malignant origin have been studied to evaluate whether in vitro invasion and/or secretion of urokinase-type plasminogen activator are related to tumorigenicity in athymic nude mice. Only the six cell lines of malignant origin were tumorigenic. Two of these were invasive in the in vitro assay. These two cell lines were oestrogen receptor negative. Three of the other four cell lines of malignant origin contained oestrogen receptors. The two cell lines of non-malignant origin were neither tumorigenic nor invasive. Thus tumorigenicity was correlated to malignant origin of the cell line whereas invasiveness in vitro was a property of the most undifferentiated cell lines of tumor origin. Secretion of urokinase-type plasminogen activator was neither correlated to tumorigenicity nor to invasion in vitro nor to malignancy of tissue origin.     

Co-inoculation of tumorigenic rat prostate mesenchymal cells with non-tumorigenic epithelial cells results in the development of carcinosarcoma in syngeneic and athymic animals

Co-inoculation of NbF-I and NbE-I s.c. into either adult male syngeneic rats or athymic nude mice induced the development of tumors that resembled carcinosarcoma on histopathologic evaluation. These tumors were composed of a mixture of adenocarcinoma and fibrosarcoma and were induced by the mixtures of NbF-I and NbE-I cells at a ratio ranging from 0.001 to 3.2; inoculation of NbF-I alone resulted in the development of fibrosarcoma. Flow-cytometric analysis showed that the epithelial cells subcloned from the carcinosarcoma had a DNA profile like that of their parental cell line and remained non-tumorigenic. When co-inoculated with the tumorigenic fibroblasts in syngeneic hosts, however, the subcloned epithelial cells again formed carcinosarcomas. Our results indicate that cell fusion between epithelial cells and fibroblasts is an unlikely explanation for tumorigenicity. We propose that prostatic fibroblasts exert a directive influence on their adjacent epithelial cells through a paracrine mechanism that determines epithelial growth and tumorigenicity in vivo.     

Clonal variation of tumorigenic potential in v-Ha-ras-transformed human bronchial epithelial cells: Relationship to ras oncogene expression and CAD gene amplification

Infection of an SV40 large-T antigen-“immortalized” human bronchial epithelial cell line with a Zip-v-Ha-ras retroviral vector resulted in a mass culture that was tumorigenic in athymic nude mice. A tumor cell line derived from passage of the mass culture in vivo, however, exhibited increased tumorigenicity and v-Ha-ras expression. To examine and compare the molecular events involving the ras oncogene during cell transformation in vitro and subsequent tumor formation in vivo, clonal cell populations were isolated from the v-Ha-ras-transformed mass culture. While the clonal cell lines exhibited diverse tumorigenic profiles, these differences did not correlate with v-Ha-ras expression. However, the expression of the activated ras gene, while not necessary for growth in vitro, did appear to be associated with a selective growth advantage in vivo. In addition, the modulation of gene amplification ability in these cells was not associated with the induction of tumorigenicity or v-Ha-ras expression. ©1994 Wiley-Liss, Inc.     

Selection and characterization of an erythroeosinophilic subclone (LAMA-87) and an eosinophilic subclone (LAMA-88) from the multipotential cell line LAMA-84

The human leukemic cell line LAMA-84 was established and characterized as an erythromegakaryocytic cell line. In the present study we show that these cells can differentiate in estrone-treated athymic mice and give rise to an erythroeosinophilic cell line (LAMA-87). This new cell line expressed glycophorin A, β and γ globin chain mRNA but also eosinophilic peroxidase. Hemin slightly increased the total hemoglobin production of the cells and phorbol diester (TPA), dimethyl sulfoxide (DMSO) and sodium butyrate (SB) increased the expression of megakaryocytic markers (gpllb/IIIa complex). When inoculated into non-treated athymic mice, LAMA-87 cells can differentiate to give rise to eosinomonocytic cells (LAMA-88). This new cell line expresses eosinophilic peroxidase, Luxol fast blue stain and synthesizes lysozyme. Depending on the inducer used, LAMA-88 can differentiate along a monocytic lineage (TPA, DMSO, SB and vitamin D3).

These three LAMA cell lines should be useful in further studies of the molecular regulation of the pluripotent cell commitment and may provide a model for the understanding of human hematopoiesis.     

Cell aggregation assay: a rapid means of evaluating and selecting in vitro transformed cells

A cell aggregation assay for evaluating in vitro transformation has recently been reported. Transformed cells formed larger cell aggregates than counterpart normal cells when suspended in liquid media above an agar base, a property which correlates with growth in soft agar and tumorigenicity. Using a human osteosarcoma cell line transformed by viruses and chemicals, we found increased cell growth of the transformed aggregates over untransformed cells. Moreover, certain aggregation properties (size/survival of aggregates) of transformed rat, mouse, hamster, human, dog, cat, chimpanzee, and sheep cell lines were found to be correlated with tumor potential, regardless of the method of transformation (spontaneous, chemical, or virus induced). Certain lines derived from cell aggregates growing in liquid medium above an agar layer were tumorigenic in nude mice, whereas the parent transformed line was not. Therefore, this assay can be utilized not only to evaluate tumorigenic potential, but also for selection of cells, which have undergone malignant transformation.     

Acquisition of a growth-inhibitory response to phorbol ester involves DNA damage.

TPA (12-O-tetradecanoylphorbol-13-acetate), a potent tumor promoter, has been shown to stimulate or inhibit cell growth depending on the cell type investigated. We recently found that RT101 cells, a transformed mouse JB6 epidermal cell line, acquired a greater growth inhibition response to TPA during conventional subcultivation. The growth of low-passage RT101 cells was slightly inhibited by TPA in monolayer culture but stimulated in soft agar. In contrast, the growth of high-passage cells was greatly inhibited by TPA in both monolayer culture and in soft agar. Inhibition was dose dependent, directly correlated with protein kinase C-activating activities of tumor promoters, and was found to be reversible. TPA-treated high-passage cells were greatly reduced in volume, showed extensive abnormal mitoses, and were more susceptible to detachment. High-passage cells were also found to be less tumorigenic as indicated by in vivo tumorigenicity assay in nude mice. TPA treatment rendered cells still less tumorigenic in the case of both cell lines. The mechanism for acquisition of increased sensitivity to TPA of RT101 cells during subculture was investigated; it involved nonrandom DNA damage and detachment of nonviable cells. The results suggest the possibility that early-passage RT101 cells contained two subpopulations, one TPA-sensitive and one TPA-resistant population. Conventional subcultivation may have selected for the former subpopulation. The sensitive subpopulation may have been irreversibly inhibited as a result of TPA-induced cell killing, possibly apoptosis.     

Characterization and comparison of two newly established Epstein-Barr virus (EBV)-negative and EBV-positive Burkitt's lymphoma cell lines. EBV-negative cell line with a low level of expression of ICAM-1 molecule and EBV-positive cell line with a high level of expression of ICAM-1 molecule.

Two human Burkitt's lymphoma cell lines (HBL-4 and HBL-5) were established individually from two patients with small noncleaved cell lymphoma (Burkitt's type). The HBL-4 cell line is Epstein-Barr virus (EBV)-negative, and the HBL-5 cell line is EBV-positive. Cytogenetically, both cell lines had the same chromosomal translocation, t(8;14)(q24;q32) as those observed in the primary malignant cells from individual patients. Morphologic, immunophenotypic, cytogenetic, and molecular studies confirmed that both cell lines were derived from the primary lymphoma cells in vivo. HBL-4 cells lacked CD23(H107), CD11a(LFA-1), and latent membrane protein (LMP) but expressed CD54(ICAM-1) at low levels, whereas HBL-5 cells showed the high level of expression of CD54 and faint expression of LMP but lacked CD11a. In addition, the EBV-positive lymphoblastoid cell line (LCL) expressed CD11a, CD23, CD54, and LMP at high levels. Therefore, an HBL-5 phenotype with expression of CD54 and LMP tends toward an LCL phenotype, and the augmentation of CD54 on the HBL-5 cells in comparison with primary lymphoma cells is likely to be upregulated by LMP, probably resulting from the EBV infection. There was little difference in the BrdUrd uptake in vivo and in vitro, doubling time, tumorigenicity, and dynamics of tumor growth in athymic nude mice between both cell lines. These findings indicate that the potentiality of cell growth and tumorigenicity of these two cell lines are unlikely to be related with EBV.