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Biomedical subjects

D A Chow

Publications and source records attributed to D A Chow.

At least 19 recordsLinked to original sources
PubMed1992

Tumor progression in vivo: increased soybean agglutinin lectin binding, N-acetylgalactosamine-specific lectin expression, and liver metastasis potential.

Tumors which grew out from threshold s.c. inocula of L5178Y-F9 and SL2-5 murine T-cell lymphomas in syngeneic DBA/2 mice exhibited a unified natural defense-resistant phenotype including an increased tumorigenicity and correlating reductions in susceptibility to natural antibodies, natural killer cells, and activated macrophages in vitro. The metastatic potential and cell surface saccharide expression of these cells were determined to assess the impact of growth from a small tumor focus in vivo on subsequent metastatic ability and to determine whether there was any association with changes in cell surface carbohydrates, which have been implicated now for many years in tumor development. A significantly increased liver-colonizing ability was observed following i.v. injection. The most consistent change in cell surface saccharide expression detected in studies using five lectins was an increase in N-acetyl-D-galactosamine (D-GalNAc)-specific soybean agglutinin (SBA) binding. The log of experimental liver metastasis, SBA binding, and the percentage of hepatocyte rosetting of the parental and in vivo-selected cells exhibited significant direct correlations. While inhibition of rosetting with in vivo-selected lines by D-GalNAc and galactose was consistent with the involvement of the D-galactose/D-GalNAc-specific hepatocyte receptor, preincubation of the tumor cells but not hepatocytes with D-GalNAc inhibited hepatocyte rosetting and D-GalNAc inhibited homotypic tumor cell binding. These data suggest a role for a saccharide-specific, lectin-like receptor on tumor cells in both interactions and therefore in the increased experimental liver metastasis. Furthermore, the increased expression of D-GalNAc-inhibitable SBA binding sites on the in vivo-selected variants should increase the homotypic binding by the D-GalNAc-specific lectin-like receptors on the tumor cells providing a rationale for the direct relationship observed between increased SBA binding and i.v. metastatic potential.

Acetylgalactosamine↗
PubMed1992

Regulation of natural antibody binding and susceptibility to natural killer cells through Zn(++)-inducible ras oncogene expression.

Changes in the natural resistance phenotype were examined for the 2H1, 10T 1/2 cells expressing the activated human H-ras oncogene under the transcriptional regulation of the zinc-inducible mouse metallothionein-I promoter. Culture of the cells in 50 microM ZnSO4 induced an increase in ras protein p21 levels which were maximal within 1 day. Natural-antibody (NAb) binding was significantly increased following 2 days of cell culture in ZnSO4 and continued to increase up to 4 days. The increased NAb binding returned to uninduced levels within 2 days following the removal of added zinc ions from the culture medium. The cells also exhibited a significant increase in natural killer (NK) cell sensitivity following 2 days in ZnSO4. This was maintained as long as the zinc was in the medium, but returned to uninduced levels within 1 day following its removal. The results show that NAb binding and susceptibility to NK cells increased following ras oncogene expression in 10T 1/2 cells and that both parameters were regulated by p21 expression. Repeated i.v. administration of whole-serum NAb prior to tumor inoculation reduced the number of early tumors following s.c. injection of Zn(++)-induced 2Hl cells into Zn(++)-treated C3H/HeN mice, consistent with an in vivo role for NAb in the defense against ras-transformed cells. In contrast, small but statistically significant reductions in NAb binding were observed following v-H-ras transformation of NIH 3T3 cells or v-src transformation of 10T 1/2. The data argue for an NAb- and NK-cell-susceptible phase of ras-induced tumor development which is a prerequisite for these mediators to contribute to a first line of defense against incipient neoplasia, and suggest that characteristics of the recipient cell and the transforming oncogene are important in determining the natural resistance phenotype.

3T3 Cells↗
PubMed1992

Polyclonal natural antitumor antibody binding dynamics: preferential release of surface membrane molecules and increased metastasis.

Flow cytometry revealed the dynamic nature of polyclonal whole serum naturally occurring IgG and IgM antibody binding to the syngeneic murine T cell lymphomas SL2-5, L5178Y-F9 and the in vitro selected high natural antibody binding variant L5178Y-F9 TPA/NAb+3. This was particularly evident at physiological conditions where the temperature was 37 degrees C and the concentration of reactive serum natural antibodies (NAb) was high. Lower binding was observed at 37 versus 4 degrees C, or after raising the temperature from 4 to 37 degrees C, a procedure which was associated with an augmented loss of 125I-surface-labelled material from cells incubated in NAb compared to cells exposed to growth media. Even at 4 degrees C, NAb binding exhibited biphasic kinetics suggesting a loss of surface-bound NAb and a subsequent cycle of NAb uptake. The increased intravenous liver metastasis potential of the high NAb binding L5178Y-F9 TPA/NAb+3 corresponded with its higher total loss of 125I-surface-labelled material when incubated in NAb at 37 degrees C, and with its extensive loss of NAb binding when the temperature was raised from 4 to 37 degrees C. These observations are consistent with the idea that molecules released from the cell may contribute to the higher metastasis. This thinking was supported by the increased metastasis of tumor cells injected intravenously, either with serum in which they had been preincubated at 37 degrees C or into mice treated with supernatants from tumor cells incubated in NAb.

Animals↗
PubMed1991

RNK granule extract cytolysis: increased tumor susceptibility and release of proteochondroitin sulphate inhibitor in high NaCl.

The insensitivity of the natural killer (NK)-resistant L5178Y-F9 murine T-cell lymphoma to granule extracts from a rat NK leukemia could be preferentially reversed in increased NaCl (0.25 M) compared with the NK- and granule extract-sensitive SL2-5. The high salt effect predominated in the binding rather than the lytic phase of the extract reaction similar to the activity of extract inhibitory supernates preferentially produced from L5178Y-F9 cells. Exposure of the L5178Y-F9 to 0.25 M NaCl was associated with an increased production of inhibitory supernate and an increased sensitivity of the cell as an extract target. Pretreatment of inhibitor-containing supernatant or inhibitor-producing L5178Y-F9 cells with pronase or chondroitinase AC reduced the inhibitory activity of the resultant supernates, and L5178Y-F9 supernates treated with anti-chondroitin sulphate AC antibodies exhibited reduced inhibitory activity. These observations and the previously reported molecular weight heterogeneity and protease sensitivity of the inhibitor argue that chondroitin sulphate AC-containing proteoglycans released from the tumor cell surface may inhibit cytolysin activity, contributing to the preferential resistance of the L5178Y-F9 to rat NK granule extract cytolysis.

Animals↗
PubMed1991

Natural antibody recognition of v-H-ras-induced 10T1/2 transformation.

An increasing body of evidence supports a role for natural antitumor antibodies acting against tumors in vivo. However, a role for natural antibodies (NAb) in tumor surveillance would imply that sensitivity to NAb should increase following events associated with cellular transformation. To test this prediction we examined by flow cytometry the effect on serum NAb binding of v-H-ras expression and integration in 10T1/2. The co-introduction of v-H-ras and the neomycin resistance (neor) gene into 10T1/2 followed by G418 selection resulted in a marked and heterogeneous increase in NAb binding. Clonal analysis of this population demonstrated that the increased NAb binding was associated with tumorigenic conversion and ras-p21 expression. The results provide the first evidence for a NAb-susceptible phase of ras-induced transformation.

Animals↗
PubMed1991

Inverse correlation between natural antitumor antibodies and tumor susceptibility in individual xid-bearing mice.

Natural antibodies (NAb), natural killer (NK) cells and activated macrophages have all been implicated in the rejection of threshold syngeneic tumor inocula. Previous analysis of tumor susceptibility in normal versus inbred and F1 mice bearing the B cell deficiency associated with the xid mutation of CBA/N mice demonstrated an inverse relationship between the tumorigenicity of the RI-28, a radiation-induced leukemia of the CBA/H strain, and the pooled anti-RI-28 serum NAb levels in mice with the same genetic origins. No relationship with tumor susceptibility was seen with NK cell or in vivo activated macrophage cytolysis. Flow-cytometric determination of antitumor serum NAb bled from individual male and female (CBA/N X CBA/J)F1 mice 1 week prior to the threshold tumor inoculation has revealed extensive heterogeneity within the NAb levels of each sex. A comparative analysis of tumor fate with NAb activity revealed that tumors appeared in only 26.3% of animals with a mean fluorescence channel binding above 60 channels in contrast with 77.3% of animals with lower NAb levels. These data extend to the level of individual hosts the support for an inverse relationship between host NAb activity and tumor susceptibility. In addition, subsequent analysis of serum antitumor NAb levels, splenic NK cytolysis and in vitro lymphokine-activated macrophage activity with all three mediators originating from the same individual F1 mice showed no consistent correlations between these natural resistance activities, arguing for the exclusion of deficiencies in NK cell or macrophage function as the basis for the differential tumor susceptibility in individual F1 mice.

Animals↗
PubMed1990

RNK granule extract cytolysis: differential inhibitor production by an NK-resistant vs an NK-sensitive murine lymphoma.

Natural killer (NK) cell-resistant tumors exist despite their ability to bind cells from the effector population. Tumor sensitivity to NK activity was therefore examined at the level of susceptibility to cytolysin-containing NK cell cytotoxic granule extracts. The NK-sensitive SL2-5 murine lymphoma was markedly more susceptible than the NK-resistant L5178Y-F9 to solubilized granule preparations from the rat NK tumor cell line RNK-16, and this corresponded also with tumor sensitivity to hypotonic lysis. However, the resistant L5178Y-F9 was better able to inhibit the extract activity than the SL2-5. Dissociation of the binding and lysis phases of the cytolysin reaction based on their differential temperature requirements, 4 degrees C for binding and 37 degrees C for lysis, permitted an examination of the cytolysin/tumor interaction prior to lysis. The residual cytotoxic activity was lower after extract exposure to the L5178Y-F9 compared with the SL2-5 consistent with possible inhibitor production. Finally, supernatant material collected from the L5178Y-F9 was a better inhibitor of granule extract lysis and acted preferentially in the extract-binding phase. The inhibitor appears to be protein in nature, relatively stable, and exhibits molecular weight heterogeneity ranging from 2000 to greater than 300,000.

Animals↗
PubMed1989

Low natural antibody and low in vivo tumor resistance, in xid-bearing B-cell deficient mice.

Evidence from correlative studies and Winn-type assays in syngeneic murine models has suggested that natural antibodies contribute to resistance against tumors in vivo. The B cell deficit associated with the X-linked immunodeficiency of CBA/N strain mice provided a genetic model in which to further test this question. RI-28, a radiation-induced T cell leukemia of the CBA/H strain acquired reduced levels of fluorescence-detected natural antibodies from the serum of X-linked immunodeficiency-bearing CBA/N and male (CBA/N x CBA/J) F1 mice compared with the serum from normals. Threshold s.c. inocula of the RI-28 appeared sooner and produced higher tumor frequencies in the X-linked immunodeficiency-bearing animals. This data coupled with the lack of correlating deficiencies in natural killer cell or activated macrophage activity provide the first genetic evidence for the hypothesis.

Animals↗
PubMed1988

Tumorigenicity of murine lymphomas selected through fluorescence-detected natural antibody binding.

Fluorescence-activated cell sorting was used to isolate high and low IgM natural antibody (NAb) binding populations from a heterogeneous line of the L5178Y-F9 murine lymphoma. The ranking of NAb binding and complement-dependent NAb lysis of the selected and starting lines were the same and opposite to that of their tumorigenicity in syngeneic DBA/2 mice. L5178Y-F9 and SL2-5 clones repeatedly treated with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate and selected by fluorescence-activated cell sorting for high NAb binding exhibited increases in NAb binding and sensitivity to complement-dependent NAb lysis which corresponded with reduced tumor frequencies of threshold inocula. Although the high NAb binding SL2-5 line was slightly more sensitive to natural killer (NK) cell cytolysis, changes in susceptibility to activated macrophages or hypotonic lysis were not consistent with the observed reductions in tumor frequency so that the selected alterations in NAb binding corresponded best with tumorigenicity. These data confirm the same inverse relationship exhibited previously by in vivo and in vitro selected tumor variants and provide more precise evidence supporting a role for NAb in host resistance against tumor foci.

Animals↗
PubMed1988

Tumor progression in vitro: tumor-promoter-induced reversible decrease in natural immune susceptibility.

Growth of established murine tumor lines in media containing the phorbol ester tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA), was associated with reversible reductions in sensitivity to in vitro and in vivo parameters of natural resistance. L5178Y-F9 cells exposed to 100 ng TPA/ml for 2 days and returned to culture without TPA for 0-2 days, exhibited reductions in sensitivity to complement-mediated lysis by natural antibodies (Nab), activated macrophages and hypotonic lysis. The natural killer (NK) cell sensitive SL2-5 lymphoma was less sensitive to NK cells, complement-dependent NAb and hypotonic lysis after 2 days growth in 2 or 3 micrograms TPA/ml. Although TPA-treated L5178Y-F9 cells could acquire higher levels of serum NAb in vitro, this was complicated by the instability of the binding at 37 degrees C resulting in an effectively reduced capacity to bind NAb which was also demonstrated by TPA-treated SL2-5 cells. The tumor frequency of threshold s.c. inocula and the i.v. metastatic potential of the TPA-treated tumors was increased in syngeneic DBA/2 mice revealing possible correlations between reductions in the cellular characteristics assayed in vitro and decreased susceptibility to host-mediated defenses in vivo. Continued growth of the TPA-treated cells for a total of 2-8 days without TPA produced a reversal in the in vitro parameters, in the tumor frequency and in the metastatic potential, indicating the requirement for TPA to maintain the resistant phenotype. These data are consistent with the initial reversible nature of the promotion phase of multistage carcinogenesis. The reversible TPA-induced reductions in sensitivity to mediators of natural resistance may be an integral component of promotion, contributing to tumor survival in vivo and increasing the probability that the tumor will progress to a more malignant phenotype.

Animals↗
PubMed1987

Regulation of tumor development: the biphasic effects of silica and of lipopolysaccharide on natural resistance.

The impact on tumor development of the BRM silica and LPS was assessed through analysis of changes in NR parameters in vivo and in vitro. Although injection of the fumed silica Cab-o-sil 3 days before a threshold s.c. inoculum of L5178Y-F9 cells increased the tumor frequency in syngeneic DBA/2 mice, tumors recovered from silica-treated animals exhibited an augmented resistance to NAb and to in vivo NR. Cab-o-sil increased in vivo NR and induced a biphasic modulation of anti-tumor NAb and NK activities. The appearance of more autonomous tumors in Cab-o-sil-treated mice corresponding with a stimulation of NR parameters, suggests that the adjuvant activity of silica also contributes to its co-carcinogenic effect by accelerating tumor development. While injection of LPS 2-3 days before a threshold tumor inoculum lowered the tumor incidence, the survival of tumor cells injected within 1 day of LPS was increased. A corresponding early decrease in NAb activity occurred, in contrast with increases in NK cell and NAb levels previously observed after 5 days. This biphasic effect of LPS on NR effectors assayed in vitro was also seen on in vivo NR. Although their frequency was higher, tumors initiated during the period of LPS-induced NR abrogation exhibited greater reductions in NAb binding and sensitivity to NR than tumors from control mice. These data extend the support for NAb acting against tumor cells in vivo and reveal the dual nature of NR in tumor development, defending against small tumor foci and driving the progression of the surviving neoplasm.

Animals↗
PubMed1987

Tumor progression in vitro: the paradoxical natural antibody and complement-selected phenotype.

An in vitro model of tumor progression was employed to investigate the contribution of natural antibody (NAb) to antitumor resistance in vivo. Repeated cycles of L5178Y-F9 and SL2-5 tumor growth in the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) followed by the selective elimination of sensitive variants through complement-dependent syngeneic NAb lysis yielded tumors with a reduced sensitivity to NAb and complement, natural killer (NK) cells and the rapid elimination assay of natural resistance (NR). A dissection of the resistant phenotype revealed a reduction in the binding capacity of complement-fixing NAb and NK cells, a reduced susceptibility to hypotonic lysis and, paradoxically, increased fluorescence-detected NAb binding that correlated inversely with a reduced tumor frequency of threshold subcutaneous tumor inocula. The data distinguish tumor binding of NAb that leads to complement activation from other NAb binding and expose a difference between NR measured as the tumor frequency of threshold tumor inocula versus the rapid radiolabelled tumor elimination assay. Complement-dependent NAb lysis may not contribute significantly to the defense against small tumor foci; however, NAb-mediated processes associated with high fluorescence-detected NAb binding likely provide resistance.

Animals↗
PubMed1986

Phenotypic alterations in tumors that developed from threshold subcutaneous inocula. I. Reduced binding of natural antibodies and sensitivity to hypotonic lysis.

Tumors obtained from the injection site of threshold subcutaneous inocula of L5178Y-F9 or SL2-5 lymphomas in syngeneic mice exhibited increased tumor frequencies and reduced sensitivities to other parameters of natural immune resistance in vivo and in vitro. An examination of the resistant phenotype of cells derived through this model of tumor progression revealed that the more aggressive in vivo grown cells were less able to inhibit natural killer (NK) cell cytolysis and to bind natural antibodies (NAb) measured through fluorescence analysis, although they could not be distinguished from the starting clones by absorption of NAb for complement-mediated lysis. The in vivo grown cells also exhibited a reduced sensitivity to hypotonic lysis, which was not detectable after preincubation at 4 degrees C or upon exposure to sodium azide, procedures that reduced the lysis of the starting clones. The differential susceptibility of the in vivo grown cells was increased to control levels by treatment with cycloheximide or colchicine. These studies suggest that a decreased sensitivity to lysis associated with a reduced autolytic process and an increased counterlytic mechanism, in addition to a reduced antigen expression for binding of NK cells and certain NAb contribute to this resistant phenotype, which may characterize tumors that arise under the selective pressure of natural resistance mechanisms in the natural course of neoplastic development.

Absorption↗
PubMed1985

Characterization of tumor progression from threshold tumor inocula: evidence for natural resistance.

An examination of the variant generation and selection hypothesis of tumor progression was undertaken using the NK-sensitive, NAb-sensitive SL2-5 lymphoma in the threshold inoculum model of tumor progression. Tumor cells obtained from the i.p. injection site expressed increased heterogeneity for sensitivity to syngeneic NAb and to NR measured in the 131IUdR-labelled tumor elimination assay. Cells retrieved from the s.c. injection site exhibited reductions in sensitivity to NR which correlated with decreases in sensitivity to syngeneic NAb and NK cells in vitro. These data confirm and extend our previous observations with the NK-resistant L5178Y-F9 lymphoma and further substantiate the evidence for the participation of NAb and NK cells in host-mediated anti-tumor resistance. Characterization of the model revealed that the selection for reduced sensitivity to NR in thymus-depleted AT x BM mice and normal animals could not be distinguished, suggesting that thymus-independent mechanisms may be major contributors to the surveillance of nascent tumors. The decreases in susceptibility to NR occurred in a stepwise and time-dependent manner in accord with the sequential multistage concept of progression. Furthermore, the selection for tumor cells which exhibited reductions in sensitivity to NR correlated with selection for increased tumorigenicity, in keeping with the idea that progression is associated with development towards an increasingly autonomous tumor.

Animals↗
PubMed1984

Variant generation and selection: an in vitro model of tumor progression.

Evidence for a new in vitro model of tumor progression was sought on the basis of the variant generation and selection hypothesis. The stability of a cloned murine tumor was examined during growth in standard tissue culture or in media containing the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Analysis of subclones from the appropriate tumor populations revealed that growth of the L5178Y-F9 clone in 100 ng/ml TPA and 0.1% dimethyl sulphoxide (DMSO) for 2 days yielded a tumor which exhibited increased cellular heterogeneity for susceptibility to both syngeneic and allogeneic natural antibodies (NAb). Subsequent exposure of TPA- and DMSO-treated cells to two cycles of syngeneic NAb-mediated cytolysis resulted in tumor populations which expressed a reduced sensitivity to syngeneic NAb. Thus the elements of tumor variant generation and selection were demonstrated by means of this approach, and repeated cycles of the TPA treatment and NAb cytolysis produced tumor cells with a reduced susceptibility not only to NAb in vitro but also to anti-tumor natural resistance (NR) measured in a tumor elimination assay in vivo. These observations extend the support for the notion that tumor progression can proceed through variant generation and selection. Furthermore, the association of tumor variant generation with exposure to the combination of TPA and DMSO, both non-mutagens, offers a model for studying non-mutagenic mechanisms of tumor development.

Animals↗
PubMed1984

Tumor selection in vivo for reduced sensitivity to natural resistance and natural antibodies.

The contribution of natural antibodies (NAb) to the selective elimination of tumor variants in vivo was studied to further support the hypothesis that NAb participate in host-mediated natural resistance (NR) against neoplasia. Tumors obtained after the sc, ip, or iv inoculation of the natural killer cell-resistant, natural antibody-sensitive L5178Y-F9 tumor clone into syngeneic DBA/2 mice were tested for their sensitivity to NR in the [131I]5-iodo-2'-deoxyuridine elimination assay and to serum NAb in the presence of complement. Cells removed from the ip or sc sites of tumor inoculation exhibited a reduced susceptibility to syngeneic NR and to syngeneic but not to allogeneic NAb. Tumors recovered from the spleen, brain, and lungs after iv inoculation also expressed a decreased sensitivity to both syngeneic NR and NAb. These data suggest that NR against tumors is widely disseminated and support the hypothesis that NAb participate in this antitumor defense, including the control of metastatic spread of disease. Tumors previously selected in vivo also exhibited reduced sensitivity to complement-mediated lysis by NAb acquired in the peritoneum. The correlation observed between this sensitivity to complement and the recovery of tumor cells after the ip injection of L5178Y-F9 contribute to the evidence that NAb acts in vivo.

Animals↗
PubMed1983

In vivo generation and selection of variants with altered sensitivity to natural resistance (NR): a model of tumor progression.

The stability of a cloned murine tumor for sensitivity to NR was examined following growth in vivo in order to test the hypothesis that tumor progression proceeds through the generation and selection of variants. Clonal sensitivity to the [131I]-dUrd elimination assay of NR was assessed for the L5178Y-F9 tumor grown in syngeneic DBA/2 mice or maintained solely in tissue culture. Subclones derived from a tumor obtained from the injection site 3 1/2 weeks after the s.c. inoculation of 25 cells were less sensitive to NR in comparison with subclones derived from cells grown only in vitro. Subclones from the cells grown in vivo exhibited increased heterogeneity in sensitivity to NR in addition to their expanded range of susceptibility to complement-mediated lysis by CBA serum natural antibodies. The extent of the heterogeneity argues against tumor "adaptation" forming the basis for the phenotypic alteration while chromosomal studies eliminate the possibility that a new tumor was induced. These data support the hypothesis that tumor progression proceeds through the random generation of variants and host-mediated selection for the proliferation of clones with an increased ability to survive.

Animals↗