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Biomedical subjects

K Sikora

Publications and source records attributed to K Sikora.

At least 37 records · Page 2Linked to original sources
PubMed1998

Generation of a monoclonal antibody to P-glycoprotein peptides using tuberculin-PPD as a carrier.

A novel immunization protocol together with stringent selection criteria have been employed to generate a new murine monoclonal antibody ("D8", isotype IgG1, kappa) which specifically recognizes the human p170 drug resistance glycoprotein. This antibody is directed towards a defined peptide sequence located in the -COOH terminal region of the first external loop of the molecule. It is reactive with its epitope within the intact native glycoprotein in formalin-fixed and conventionally processed histological tissues, in flow-cytometric preparations and by Western blotting. The antibody precipitates its target peptide sequence from solution, and thus may be a useful reagent with which to establish an ELISA, RIMA or other similar assay. The peptide epitope recognized by this monoclonal antibody is restricted to the human MDR1 gene product and is not contained within the rodent homologue of the P-170 molecule. Immunohistochemistry has consistently failed to detect this epitope in rodent tissues, thus confirming that it does not exhibit the cross-reactivity of other currently available anti-P-glycoprotein monoclonal antibodies. The experience of this study emphasizes the value of the tuberculin-PPD (purified protein derivative) immunization protocol as a powerful strategy when generating monoclonal antibodies to small synthetic peptides. The resulting monoclonal antibody (D8) will be an invaluable reagent with which to analyse P-170 glycoprotein expression when assessing the role of multidrug resistance in human cancers.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

Rapid adenoviral transduction of freshly resected tumour explants with therapeutically useful genes provides a rationale for genetic immunotherapy for colorectal cancer.

To develop protocols for the molecular immunotherapy of colorectal cancer, we compared the efficacy of three separate classes of therapeutic genes to induce antitumour responses in a murine colorectal cell model. Thus, the effects of two cytokines (IL-2 and GM-CSF) were compared with those of a costimulatory gene (B7.1) and a suicide gene (HSVtk). The rank order of efficacy against primary tumour growth was HSVtk[GCV], B7.1 > puro, IL-2 > GM-CSF, neo whereas the order of efficacy in inducing antitumour immunity was GM-CSF, IL-2, > B7.1, HSVtk[GCV] > puro, neo in a prophylactic vaccination model. To exploit these data in a clinically relevant and realistic way, we also demonstrated that colorectal tumours can reproducibly be explanted and established in short-term culture. Finally, a rapid transduction protocol has been developed by which, using adenoviral vectors, as many as 90% of the cells in these fresh tumour explants can be engineered to express high levels of the clinically relevant genes (GM-CSF or IL-2) within 1-2 weeks of surgery. Adenovirus-mediated gene delivery was reproducibly and significantly more efficient than retroviral transduction using the MFG-beta-Gal retroviral vector over the time-frame of importance for vaccination. Hence, combination of the animal model data with the ex vivo modification protocol suggests that vaccination of colorectal patients of the appropriate stage will be possible and effective.

Adenoviridae↗
PubMed1997

Genetic prodrug activation therapy.

Genetic prodrug activation therapy shows promise as a therapeutic option for the treatment of cancer as well as a variety of other diseases. It involves the insertion of a gene encoding a drug-metabolizing enzyme into cells and the systemic administration of a prodrug. The prodrug is converted to a cytotoxic agent by the action of the expressed enzyme. To ensure that the enzyme is only expressed in the targeted subset of cells, the transcriptional apparatus of a gene that is unique to this subset is used to regulate the gene encoding the drug-metabolizing enzyme. As with all types of gene therapy, one of the major obstacles to successful clinical treatment is the development of safe and effective gene delivery systems.

Autolysis↗
PubMed1997

Rhabdomyosarcoma. Morphologic, immunohistochemical, and DNA study.

In this study 80 cases of predominantly adult rhabdomyosarcoma are presented as follows: 20 cases of the embryonal type, 32 cases of the alveolar and 8 cases of the pleomorphic type. Additional histologic classification was performed in each type. In myotube stage the histologic picture of fetal muscles cannot be compared to the alveolar type of rhabdomyosarcoma. Desmin and sarcomeric actin are observed in 47.7% of all cases, and myoglobin and myosin in only 23.1%. The reactions were diffuse, disperse, or focal. Electron microscopic study subdivides desmin positive tumors into three groups of differentiation. DNA analysis shows that most desmin positive cells are diploid in comparison to all the tumor cells that are hyperdiploid and tetraploid.

Adult↗
PubMed1996

Assessment of brain changes with registered MR before and after bone marrow transplantation for chronic myeloid leukemia.

PURPOSE: To determine the frequency and nature of changes to the brain resulting from chemotherapy, radiation therapy, and bone marrow transplantation for chronic myeloid leukemia and to compare the sensitivity of conventional and registered MR scans for detecting these changes. METHODS: In 15 patients, conventional T1-weighted, T2-weighted, and fluid-attenuated inversion recovery MR sequences, as well as T1-weighted radio frequency spoiled 3-D volume MR scans were performed before, 4 to 6 days after, and up to 339 days after transplantation (13 allografts, two autografts). A subvoxel registration program was used to match the volume images precisely so that small changes could be detected after subtraction of scans. Five healthy adult control subjects were also studied on two occasions 1 month apart. RESULTS: Studies performed 4 to 339 days after transplantation showed ventricular enlargement and cortical atrophy in all 13 patients who had allografts. The changes were evident at 4 to 6 days after transplantation and became more obvious during later follow-up examinations. Similar changes were seen in one patient with an autograft but no significant change was seen in the other patient with an autograft or in the five control subjects. Accurately registered volume scans were more sensitive than unregistered conventional scans in detecting early (9/10 versus 0/10), intermediate (12/13 versus 3/12), and late (10/10 versus 4/9) ventricular enlargement on follow-up examinations. The same applied to cortical atrophy (9/10 versus 0/10, 12/13 versus 0/12, and 10/10 versus 0/9). CONCLUSION: The specific cause and clinical significance of these changes are uncertain. Subvoxel registration of serial MR images may reveal changes that are poorly seen or not apparent on conventional scans.

Adolescent↗
PubMed1994

Establishment and in vivo characterization of multidrug-resistant dunning R3327 rat prostate-carcinoma cell-lines.

We describe the selection of 3 new multidrug-resistant cell lines derived from tumor cells of different metastatic phenotypes within the Dunning R3327 model of rat prostatic carcinoma. Cell lines of weak (AT2) and strong (AT3 and MAT-LyLu) metastatic behavior were cultured in vitro and challenged with doxorubicin at progressively increasing concentrations. Chemosensitivity was determined colorimetrically by release of precipitated formazan pigment (MTT assay). Expression of the multidrug-resistance glycoprotein (P-170) was monitored immunocytochemically and by Western blotting using monoclonal antibody C219. The behavior of the parental and resultant drug-resistant cells was assessed by their growth in syngeneic rats. Doxorubicin challenge of the initially drug-sensitive parental prostatic carcinoma cell lines resulted in the rapid development of multidrug resistance together with simultaneous expression of P-glycoprotein. While lung and lymph-node metastases developed in host animals inoculated with parental AT3 and MAT-LyLu cells, no metastases developed in the multidrug-resistant progeny of these cell lines. This study has shown that Dunning rat prostate-carcinoma cell lines, previously sensitive to different cytotoxic agents, rapidly become multidrug-resistant and express P-glycoprotein following exposure to doxorubicin. Furthermore, development of multidrug resistance is associated with a less aggressive tumor phenotype and loss of metastatic potential. Nevertheless, it is unlikely that the non-metastatic phenotype of Dunning rat prostatic carcinoma cells is solely associated with expression of P-glycoprotein. These new multidrug-resistant cell lines exhibiting an altered behavioral phenotype will provide a valuable model with which to analyze the relationship between expression of P-glycoprotein and the metastatic phenotype of prostatic carcinoma cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗