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  • 1
    Electronic Resource
    Electronic Resource
    A nontoxicPseudomonas exotoxin a induces active immunity and passive protective antibody againstPseudomonas exotoxin a intoxication (1999)
    Springer
    Journal of biomedical science 6 (1999), S. 357-363 
    Details
    ISSN: 1423-0127
    Keywords: Pseudomonas exotoxin A ; Vaccination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Pseudomonas exotoxin A (PE) is one of the most potent cytotoxic agents produced byPseudomonas aeruginosa. In this study, we examined the possibility of using PE with a deletion of 38 carboxyl-terminal amino acid residues, designated PE(Δ576–613), for active immunization against PE-mediated disease. We first examined the toxic effects of PE and PE(Δ576–613) on 5- and 9-week-old ICR mice. The results show that the subcutaneous administration of PE(Δ576–613) at a dose of 250 µg was still nontoxic to 5- and 9-week-old ICR mice, while native PE was lethal at a dose of 0.5 and 1 µg, respectively. PE(Δ576–613) was then used to immunize ICR mice. The minimum dose of PE(Δ576–613) that could effectively induce anti-PE antibodies in 5- and 9-week-old ICR mice was found to be 250 ng. However, immunization with 250 ng PE(Δ576–613) failed to protect the immunized mice from a lethal dose of PE. The effective immunization dose of PE(Δ576–613) that could protect mice against a 2 µg PE challenge was found to be 15 µg. In addition, sera obtained from PE(Δ576–613)-immunized ICR mice were able to neutralize PE intoxication and effectively protect mice from PE. Thus, PE(Δ576–613) may be used as an alternative route to new PE vaccine development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02253525
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  • 2
    Electronic Resource
    Electronic Resource
    p53 gene status modulates the chemosensitivity of non-small cell lung cancer cells (2000)
    Springer
    Journal of biomedical science 7 (2000), S. 64-70 
    Details
    ISSN: 1423-0127
    Keywords: p53 ; Chemosensitivity ; Cell cycle ; Apoptosis ; Non-small cell lung cancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract This study examined the effects of p53 gene status on DNA damage-induced cell death and chemosensitivity to various chemotherapeutic agents in non-small cell lung cancer (NSCLC) cells. A mutant p53 gene was introduced into cells carrying the wild-type p53 gene and also vice versa to introduce the wild-type p53 gene into cells carrying the mutant p53 gene. Chemosensitivity and DNA damage-induced apoptosis in these cells were then examined. This study included five cell lines, NCI-H1437, NCI-H727, NCI-H441 and NCI-H1299 which carry a mutant p53 gene and NCI-H460 which carries a wild-type p53 gene. Mutant p53-carrying cells were transfected with the wild-type p53 gene, while mutant p53 genes were introduced into NCI-H460 cells. These p53 genes were individually mutated at amino acid residues 143, 175, 248 and 273. The representative cell line NCI-H1437 cells transfected with wild-type p53 gene (H1437/wtp53) showed a dramatic increase in susceptibility to three anticancer agents (7-fold to cisplatin, 21-fold to etoposide, and 20-fold to camptothecin) compared to untransfected or neotransfected H1437 cells. An increase in chemosensitivity was also observed in wild-type p53 transfectants of H727, H441, H1299 cells. The results of chemosensitivity were consistent with the observations on apoptotic cell death. H1437/wtp53 cells, but not H1437 parental cells, exhibited a characteristic feature of apoptotic cell death that generated oligonucleosomal-sized DNA fragments. In contrast, loss of chemosensitivity and lack of p53-mediated DNA degradation in response to anticancer agents were observed in H460 cells transfected with mutant p53. These observations suggest that the increase in chemosensitivity was attributable to wild-type p53 mediation of the process of apoptosis. In addition, our results also suggest that p53 gene status modulates the extent of chemosensitivity and the induction of apoptosis by different anticancer agents in NSCLC cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02255920
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  • 3
    Electronic Resource
    Electronic Resource
    Characterization of an unusual mutant of human melanoma cells resistant to anticancer drugs that inhibit topoisomerase II (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 155 (1993), S. 414-425 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The topoisomerase II inhibitor, VP-16 (etoposide), is an important component in many chemotherapeutic regimens. To cahracterize resistance to this drug, the human melanoma cell line, FEM-X, was selected in multiple steps with VP-16. To prevent the development of typical multidrug resistance, an inhibitor of P-glycoprotein, the tiapamil analog, RO-11-2933, was added to the selections. The resultant clone FVP3 is 56-fold resistant to VP-16 and cross-resistant to doxorubicin (Adriamycin) (9-fold) and VM-26 (27-fold). These cells are also two- to fourfold resistant to m-AMSA, daunorubicin, and mitoxantrone. FVP3 is not resistant to the P-glycoprotein substrate vinblastine, does not express the MDR1 gene at detectable levels, and does not show reduced 3H-VP-16 accumulation. Unlike other cell lines that exhibit resistance to inhibitors of topoisomerase II, FVP3 has the same level of topoisomerase II expression and activity as FEM-X. Using live cells treated with VP-16, band depeletion assays and KCI/SDS precipitation assays show that topoisomerase II from FVP3 is much less susceptible to drug-induced cleavable complex formation than is that from FEM-X. This difference in sensitivity to VP-16 is also detected using lysates from disrupted cells, but not with isolated nuclei devoid of cytoplasmic and membrane components. In addijtion, the topoisomerase li present in nuclear edtracts from FVP3 is not resistant to the effects of VP-16 as measured by: (1)inhibition of strand passing activity during decatenation of kinetoplast DNA, (2) drug-induced linearization of plasmid DNA, and (3) immunodepletion by VP-16. These results suggest that some component of the cytoplasm or cellular membranes, or a factor depleted from nuclei during their isolation, is responsible for the resistance to VP-16 in FVP3. © 1993 Wiley-Liss, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041550224
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  • 4
    Electronic Resource
    Electronic Resource
    Genetic mapping of the mouse topoisomerase IIα gene to Chromosome 11 (1993)
    Springer
    Mammalian genome 4 (1993), S. 288-289 
    Details
    ISSN: 1432-1777
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00417440
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  • 5
    Electronic Resource
    Electronic Resource
    Mutant KB cells with decreased EGF receptor expression: Biochemical characterization (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 133 (1987), S. 127-134 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Mutants of the human KB carcinoma cell line resistant to a cytotoxic conjugate of epidermal growth factor and Pseudomonas exotoxin (EGF-PE) express a pleiotropic phenotype, which includes reduced levels of 125I-EGF binding, without altered affinity for EGF (Lyall et al., 1987). Here, the EGF-toxin (ET) resistant mutants were further characterized with respect to the amount and size of the EGF receptor and the level of EGF receptor RNA. These data indicate that decreased binding of 125I-EGF in the mutants is due to reduced amounts of EGF receptor, which is associated with decreased mRNA levels. Changes in other proteins in the ET mutants were also examined. Five of the six ET mutants had a decrease in a 78,000 Mr- membrane glycoprotein. In addition, an increase in a protein with a Mr- of 40,000 and a pl = 8.0 was found in all the mutants, and an increase in a series of proteins with a Mr- of 36,000 and a pl of 6.3-6.5 was found in some of the mutants. These results confirm the pleiotropic nature of the EGF-PE resistant mutants and show that reduced EGF binding is due to altered expression of the EGF receptor gene in the mutants.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041330116
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  • 6
    Electronic Resource
    Electronic Resource
    The role of intracellular pH in ligand internalization (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 128 (1986), S. 18-22 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Internalization of EGF and transferrin measured as the rate of uptake of 125l-labeled ligands was compared in the cell line CCL39 and a mutant derivative, PS120, lacking the Na+/H+ antiport system. No significant alteration was detected between the two cell lines. In contrast, pretreatment of the mutant cells PS-120 with 20 mM NH4Cl for 30 min to decrease persistently intracellular pH resulted in an increase in 125I-EGF and 125I-transferrin uptake by 60% and 25%, respectively. However, similar NH4Cl pretreatment of the parental cell line, CCL-39, which only affected intracellular pH very transiently did not cause an increase of ligand uptake. The binding of 125I-EGF to CCL-39 and PS-120 cells with or without NH4Cl pretreatment showed that NH4Cl pretreatment did not affect EGF binding in either CCL-39 or PS-120 cells. Since cells regulate intracellular pH by ion transport systems, we also examined the role of Na+, K+-ATPase. Ouabain, an inhibitor of Na+, K+-ATPases, showed no effect on 125I-EGF uptake in either of the cell types with or without NH4Cl pretreatment. Taken together, these results suggest that the plasma membrane-bound Na+/H+ antiport, a major pHi-regulating system in vertebrates, indirectly plays a role in ligand internalization through regulation of intracellular pH.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041280104
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