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J R Starkey

Publications and source records attributed to J R Starkey.

12 recordsLinked to original sources
PubMed1992

NMR constrained solution structures for laminin peptide 11. Analogs define structural requirements for inhibition of tumor cell invasion of basement membrane matrix.

Peptide 11, CDPGYIGSR-NH2, is a segment of laminin which blocks tumor cell invasion. A high affinity laminin receptor in tumor cells is thought to be blocked by the carboxyl-terminal YIGSR, and conformational energy calculations suggest that the glycine in YIGSR allows an important conformational bend. We replaced the YIGSR glycine residue in peptide 11 with either D-alanine or L-alanine to allow or disfavor the proposed glycine bend. We found the Gly7-->D-Ala7 analog to be equal to peptide 11 in inhibiting tumor cell invasion of basement membrane matrix. The Gly7-->L-Ala7 analog was much less capable of invasion inhibition. Two-dimensional 1H-1H NMR was used to study the solution conformations of the peptide 11 analogs. NOESY experiments revealed close NH-NH contacts in peptide 11 and the D-Ala7 analog, but not in the L-Ala7 analog. Molecular dynamics generated low energy structures with excellent NOE agreement for peptide 11 and its analogs. Both peptide 11 and the D-Ala7 analog, but not the less active L-Ala7 analog, were predicted to have similar bends around Gly7 or D-Ala7. These results suggest that a bend in the YIGSR region of peptide 11 may be important for the binding of laminin to its metastasis-associated receptor.

Amino Acid Sequence↗
PubMed1991

Introduction of antibody into viable cells using electroporation.

Conditions for labelling an intracellular antigen, p21ras, using electroporation to introduce a fluorescent antibody, are described. Following labelling, cells were evaluated for p21ras associated fluorescence by flow cytometry. Electroporation, sorting, and cell handling parameters were varied to determine optimal conditions for cell viability. Cells were best held in serum containing growth medium both before and after electroporation, while antibody introduction during the electroporation phase was most efficient when carried out in a balanced saline solution. For maximum efficiency of antibody internalization, the antibody needed to be present during electroporation, and medium needed to be replaced several times in the first few hours after electroporation to ensure good cell survival.

Animals↗
PubMed1990

Cell-matrix interactions during tumor invasion.

This manuscript reviews the molecular aspects of tumor cell invasion of extracellular matrix. The changes in cell:substrate and cell:cell receptors that characterize motile cells are discussed for their importance not only in mediating invasive cell behavior, but also as diagnostic markers for invasive potential. Autocrine motility and scatter factors probably have key roles in initiating migratory behavior, while specific and non-specific extracellular matrix alterations can facilitate cell locomotion. The manuscript reviews reported changes, such as induction of cell motility, matrix degrading enzymes, and invasive/metastatic potential, which can follow transfection with ras oncogenes, and details the key roles of metalloproteinases, heparanase, and plasminogen activator in matrix degradation. Enzymatic inhibitors of initial steps in extracellular matrix degradation, such as rTIMP, and synthetic blockers of adhesive steps in tumor cell invasion represent types of reagent with potential as anti-metastatic agents. Their potential usefulness may be increased if they can be incorporated into a novel, long-term, non-traditional delivery system.

Animals↗
PubMed1990

Tyrosine- and phenylalanine-restricted formula diet augments immunocompetence in healthy humans.

Previous studies indicate that limiting tyrosine and phenylalanine intake in the diet decreases tumor growth and metastasis. General health status, immune status, and platelet function were studied in nine healthy human subjects consuming low-protein foods supplemented with formula diets free of tyrosine and phenylalanine to maintain total daily intake of tyrosine at 2.4 mg/kg body wt and phenylalanine at 3.5 mg/kg body wt. This regimen decreased plasma tyrosine (p less than 0.05) but not phenylalanine. Blood indicators of protein status were not changed. Platelet aggregation decreased in response to adenosine diphosphate and platelet activating factor in seven of nine subjects. Natural killer, T-helper, and T-cytotoxic/suppressor lymphocyte numbers proportionally increased relative to neutrophils (p less than 0.05). Natural killer cell activity increased in six of nine subjects. Increased natural killer cell activity and decreased platelet aggregation are two indices associated with decreased tumor growth and metastasis.

Body Composition↗
PubMed1989

Isolation of viable tumor cells following introduction of labelled antibody to an intracellular oncogene product using electroporation.

A method for labelling the intracellular ras oncogene product, p21, with a monoclonal antibody, in B16BL6 mouse melanoma cells for subsequent flow cytometric analysis and viable cell sorting is described. Permeabilization of the cells for introduction of labelled antibody was attempted using (1) lysolecithin treatment, and (2) electroporation, a much more highly controllable technique. Permeabilization was assessed using propidium iodide or calcofluor white M2R staining, while short-term cellular viability was determined using fluorescein diacetate staining and long-term viability by reculturing the sorted cells. We successfully introduced labelled antibody into the cells with both permeabilization techniques. Insufficient numbers of viable permeabilized cells were obtained lysolecithin treatment to warrant an attempt at viable cell sorting. On the other hand, good numbers of viable, permeabilized cells were obtained using electroporation and we successfully sorted viable tumor cell populations based on the intensity of their anti-p21ras staining. These sorted tumor cells retained their characteristic anti-p21ras staining intensity for at least 2 weeks of propagation in culture.

Animals↗
PubMed1989

Tumor cell invasion of three-dimensional matrices of defined composition: evidence for a specific role for heparan sulfate in rodent cell lines.

The abilities of rodent tumor cell lines; B16BL6, ND and LT dietary variants of B16BL6, +SA, RT7-4bs and RT7-4bLs to invade composite collagen I gels containing heparin, chemically modified heparins, heparan sulfate, chondroitin sulfate, hyaluronic acid, dextran, dextran sulfate, laminin and collagen IV were investigated, and compared to the invasion of plain collagen I gels. The presence of heparin or heparan sulfate most generally promoted tumor cell invasion of the gels, with more aggressive invasion being noted for the more metastatic variants examined. Of the chemically modified heparins tested, carboxyl-reduced heparin promoted matrix invasion by B16BL6 and +SA cells to the greatest degree. Hyaluronic acid marginally promoted invasion by +SA and RT7-4bs primary cells while, in these collagen I based gels laminin only promoted matrix invasion by primary +SA cells to a very limited degree. The tumor cell lines attached relatively poorly to heparan sulfate substrates compared to the other glycosaminoglycans tested, and the primary tumor cell lines also attached relatively poorly to collagen I. As expected, highly metastatic variants showed greater attachment to laminin than did their less metastatic counterparts. Apart from the negative correlation of cellular attachment to heparan sulfate substrates with invasiveness towards heparan sulfate containing gels, no other relationships emerged linking attachment rates with invasive activities for particular complex gel compositions. Our results suggest an important role for heparan sulfate, and possibly also tissue heparin, in promoting tumor cell invasion of extracellular matrices. Results from complex gels containing dextran or dextran sulfate failed to support the hypothesis that GAG sulfation is important to cellular invasion. The activity of the chemically modified heparins in promoting invasion, when present as components of these model matrices, suggests that part of the anti-metastatic activity of these compounds, when preincubated with tumor cells prior to intravenous inoculation, could result from interference with tumor cell extravasation.

Animals↗
PubMed1989

Growth factor interactions between mouse mammary cell lines cocultured in collagen gels.

Three related mouse mammary cell lines were cultured in collagen gels and assayed for growth factor responsiveness and interaction via soluble factors. The CL-S1 cell line is nontumorigenic and grows poorly in collagen gel culture. The +SA and -SA cell lines exhibit different degrees of malignant behavior in vivo and have different growth properties in vitro. In collagen gel culture, +SA growth was stimulated by serum but not by epidermal growth factor (EGF), whereas both serum and EGF were required for optimal growth of -SA cells of early passage number as well as CL-S1 cells. -SA cells of later passage repeatedly exhibited a change so as to no longer require serum while retaining EGF responsiveness. [125I]EGF binding analyses indicated that CL-S1 cells bound EGF with less affinity than did -SA cells whereas +SA cells bound almost no ligand. When cell lines were maintained in separate collagen gels but shared the same culture medium, growth of +SA or -SA cells was slightly enhanced in the presence of CL-S1 cells and -SA cell growth was enhanced by the presence of +SA cells. Using the normal rat kidney fibroblast line NRK (clone 49F) as an indicator, serum-containing conditioned media from each cell line and from each pair of cell lines cultured in collagen gels were tested for transforming growth factor (TGF) activity. Both the -SA and CL-S1 lines tested positive for TGF-alpha production and possibly released a TGF-beta activity. These results suggest mechanisms by which cell populations in and around tumors can modify one another's growth characteristics.

Animals↗
PubMed1988

Mast-cell-deficient W/Wv mice exhibit a decreased rate of tumor angiogenesis.

The role of host mast cells in tumor-associated angiogenesis was investigated by comparing the angiogenic response of genetically mast-cell-deficient W/Wv mice and mast-cell-sufficient +/+ littermate mice to s.c. growing B16-BL6 tumors. The angiogenic response was found to be slower and initially less intense in W/Wv mice than in +/+ mice. Fewer W/Wv mice than +/+ mice developed spontaneous lung metastases and W/Wv mice exhibited fewer lung metastases per mouse. Bone-marrow repair of the mast-cell deficiency restored the angiogenic response of W/Wv mice and also restored the incidence of hematogenous metastases to approach that of +/+ mice. Differences in lymphatic metastasis were not detected between W/Wv and +/+ mice. These results demonstrate a role for mast cells in vivo during tumor angiogenesis, and suggest a role also for host mast cells in hematogenous metastasis.

Animals↗
PubMed1988

Response of natural killer cells from dietary tyrosine- and phenylalanine-restricted mice to biological response modifiers.

The effect of dietary tyrosine and phenylalanine restriction on splenic natural killer (NK) cell activity was studied in tumor-free B6D2F1 and NIH nude mice and in B16 bladder-6 (BL6) melanoma-bearing B6D2F1 mice. This dietary restriction was found to suppress the naturally elevated NK-cell activity of nude mice and to induce a specific lymphocytopenia in B6D2F1 mice fed the restricted diet for a prolonged period. Baseline NK-cell activity was significantly lower in tumor-free B6D2F1 mice fed a diet restricted in tyrosine and phenylalanine (restricted diet) than in tumor-free mice fed a basal diet. Similar kinetics of activation after a single i.p. injection of 100 micrograms of polyinosinic:polycytidylic acid (poly I:C) were observed in mice fed both diets. NK-cell activity was not significantly augmented after i.v. inoculation of BL6 melanoma, irrespective of the diet fed; however, it was enhanced in tumor-bearing mice after poly I:C injection. This augmentation was similar to that observed in tumor-free mice. Spleen cells from mice fed either diet were responsive to stimulation of NK-cell activity after in vitro incubation with interleukin-2. These results indicate that dietary restriction of tyrosine and phenylalanine, a potentially useful therapeutic adjunct known to lower NK-cell activity, does not significantly interfere with poly I:C or interleukin-2 induction of NK cells. Our results also demonstrate that, while this dietary restriction causes lymphocytopenia, no effect of the diet could be found on total serum IgG or circulating immune complex levels.

Animals↗
PubMed1979

Introduction of metastatic heterogeneity by short-term in vivo passage of a cloned transformed cell line.

An experimental system for the study of metastasis has been developed using an epithelioid cell line of hepatic origin which had previously been chemically transformed in vitro. These metastatic cells were studied in the syngeneic rat strain. The cloned parent cell line metastasizes only to the lungs following intravenous, subcutaneous, or intraperitoneal injection. The metastatic phenotype is stable during in vitro passage, and subclones from the parent clone have a metastatic capacity statistically similar to that of the parent clone. Following ascites passage of the parent cell line, the cell population obtained exhibits the same metastatic ability as the parent clone. However, subclones obtained from the ascites-passaged population exhibit metastatic heterogeneity. This heterogeneity is introduced by the host passage and not by in vitro culture or subcloning. In the case of the two metastatic variants examined, the difference in the metastatic phenotype is found not to be due to differences in arrest or trapping of the cells but appears to be related to long-term survival and proliferation of the tumor cells following their arrest in the lungs. Morphologically the variants are very similar, and growth of the metastatic foci provokes a vigorous inflammatory response by the host.

Animals↗
PubMed1977

Clonal behavior of a rat liver cell line and its modification by repeated treatments with a carcinogenic polycyclic hydrocarbon.

A rat liver cell line, Lew A1, was isolated from W/LEW rats. It had the normal female karyotype in the lower passage numbers, but in the higher passages it was aneuploid. This line was passaged 65 times, produced rat serum albumin, and consisted of an apparently homogeneous population of typical epithelial cells. The cells also had high levels of the inducible aryl hydrocarbon hydroxylase enzyme complex. A series of experiments described here defined the normal clonal behavior of this line and its modification by repeated treatments with a carcinogenic polycyclic hydrocarbon, 7,12-dimethylbenz[a]anthracene. The results were discussed with particular reference to metastasis, preneoplastic changes, and neoplastic progression.

9,10-Dimethyl-1,2-benzanthracene↗