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J T Kemshead

Publications and source records attributed to J T Kemshead.

At least 37 records · Page 2Linked to original sources
PubMed1993

A rapid and highly selective approach to cell separations using an immunomagnetic colloid.

Immunomagnetic colloids have the properties of solutions and, therefore, offer distinct advantages in their ability to bind to cells as compared to larger magnetic microspheres. B cells and T cells have been isolated with higher degrees of purity following incubation with monoclonal antibodies (MoAbs) and a goat anti-mouse Ig ferrofluid. This was demonstrated both with mixtures of cell lines and lines titrated into normal bone marrow. In all cases, low non-specific binding was observed. Maximal cell capture was obtained without washing out excess MoAb, resulting in cell separations that could be completed in under 30 min. The system permits not only the magnetic capture of cells onto pins in a high gradient separator, but also their recovery. Cells separated in this way appear to be highly viable and it is possible to manipulate them further as the immunocolloid is sufficiently small for it not to interfere with tests such as indirect immunofluorescence. The advantages and disadvantages of immunocolloids versus larger magnetic microspheres are discussed.

Antibodies, Monoclonal↗
PubMed1993

Vase mini-exon usage by NCAM is not restricted to tumours of neuroectodermal origin.

The neural cell adhesion molecule (NCAM) plays an important role in normal development. Many variants of NCAM are generated through post-transcriptional and post-translational modifications. These variants are tissue-specific and their expression is developmentally regulated. NCAM is also re-expressed in a number of human tumours, including neuroblastoma, rhabdomyosarcoma, Wilms' tumour and Ewing's sarcoma. We have characterized the NCAM variants associated with rhabdomyosarcoma. Polysialylated NCAMs are present in this tumour and, after neuraminidase treatment, they resolve into 2 bands of 140 and 120 kDa. These data were corroborated by Northern-blot analysis where mRNA species of 6.7 and 5.5 kb are detected. These mRNA code for the 140- and 120-kDa NCAM proteins respectively. PCR analysis shows that the previously described VASE mini-exon is also present in NCAM found in rhabdomyosarcoma. The VASE mini-exon, spliced at exon 7-8 junctions, has previously been detected in neural and heart NCAM, as well as in NCAMs found in human small-cell lung carcinoma (SCLC). DNA sequencing confirmed that the VASE mini-exon in rhabdomyosarcoma is identical to that found in neuroblastoma and SCLC.

Alternative Splicing↗
PubMed1993

Treatment of recurrent and cystic malignant gliomas by a single intracavity injection of 131I monoclonal antibody: feasibility, pharmacokinetics and dosimetry.

A pilot study was undertaken to determine the feasibility of infusing 131I labelled monoclonal antibodies (MoAbs) into either the cavity remaining after resection of malignant glioma or into glioma cysts. Of the seven patients recruited into the study, two had cystic lesions and five resection cavities. Six of the seven were treated after relapse from primary therapy. All patients apart from one, were given a single injection of 131I conjugated to a MoAb (ERIC-1) recognising the human neural cell adhesion molecule (NCAM). One patient received a further injection of 131I-MoAb after regrowth of their disease. Pharmacokinetic studies revealed that the MoAb remained predominantly in the tumour cavity with little leakage into the systemic compartment. This resulted in a high calculated dose of radiation being delivered to the tumour cells either lining or within close proximity to the cavity/cyst wall. In such a small study, it is not possible to determine accurately response rates, but individual patient responses were observed. This, along with the low toxicity noted, demonstrates the feasibility of using 131I-MoAbs in this way. With 131I, radiation dose is deposited in tissue to a depth of 1 mm from the source. The possibility of applying isotopes such as 90Yttrium which will irradiate tumour/tissue to a greater depth (6 mm) is discussed in context with the biology of glioma infiltration into normal brain parenchyma.

Adolescent↗
PubMed1993

Third L. H. Gray Workshop, Kelvin Conference Centre, University of Glasgow, Scotland, 24-25 March 1992: The radiobiology of targeted radiotherapy.

Thirty-five participants from eight countries attended the third workshop sponsored by the L. H. Gray Trust (with additional funding from the Cancer Research Campaign). The forum was a unique opportunity to bring together clinicians and scientists with a variety of backgrounds to discuss the biological targeting of therapeutic radiation.

Humans↗
PubMed1993

Progress review: intrathecal and intratumoral injection of radiolabelled monoclonal antibodies (MoAbs) for the treatment of central nervous system (CNS) malignancies.

The systemic administration of monoclonal antibodies (MoAbs) as delivery vehicles for targeted radiation therapy is associated with many problems. Most studies show that insufficient isotope is taken up into the tumour to elicit a tumoricidal effect. This has led several groups to explore the administration of radiolabelled MoAbs into body compartments, specifically for the treatment of minimal tumour deposits that present either as malignant ascites or small nodules on the lining of body cavities. The use of 131Iodine (131I) labelled MoAbs in the treatment of disseminated disease in the central nervous system (CNS) is described and the possibility of administering radiolabelled MoAbs to a cavity generated after debulking surgery for malignant glioma in order to overcome the problem of poor MoAb uptake into solid tumour deposits is discussed together with the rationale for substituting 90Yttrium (90Y) for 131I.

Animals↗
PubMed1992

Immunoreactivity, pharmacokinetics and bone marrow dosimetry of intrathecal radioimmunoconjugates.

Ten patients with neoplastic meningitis were treated with a variety of 131I-monoclonal antibody (MAb) conjugates, chosen to bind to their particular malignancy. Pharmacokinetic studies revealed that MAbs leave the ventricular compartment, enter the sub-arachnoid space and then pass into the blood. Once the MAbs enter the blood compartment, their clearance is determined by factors such as circulating anti-mouse Ig and circulating antigens. These lead to complex formations and the clearance of the conjugate by the reticuloendothelial system. In one individual, the anti-mouse Ig response observed systemically was not mirrored within the CSF, which has implications for planning future therapy of this type. In other patients, formation of immune complexes was due to binding to circulating antigen within the blood. The major toxicity associated with the intrathecal administration of 131I-MAbs was bone-marrow suppression. The doses to the bone marrow, resulting from the form of therapy, were calculated but showed no direct correlation with WHO grade 3/4 toxicity. Doses to the ventricular lining were also calculated, but due to the complex geometry of the compartment, calculation of potential tumour doses was not practicable.

Adult↗
PubMed1992

A discordance between the human muscle NCAM sequence and those seen in other NCAM cDNA clones.

A cDNA clone, designated NC7, has been isolated from human foetal kidney that partially codes for the 140 kDa isoform of human NCAM. This clone contains a 6 bp insert that is not present in the human muscle cDNA clone lambda 4.4. This same sequence has also been found in both a cDNA clone obtained from a human Small Cell Lung Carcinoma (SCLC) line and in human genomic DNA. Furthermore, an equivalent sequence to the 6 bp region identified in the above samples is present in mouse, rat and chicken NCAM. The 6 bp insertion does not lie at a predicted intron/exon boundary as extrapolated by homology studies with the chicken and, therefore, the mechanism by which the sequence is deleted from the human muscle clone lambda 4.4 remains unclear.

Amino Acid Sequence↗
PubMed1992

Splicing of the VASE exon of neural cell adhesion molecule (NCAM) in human small-cell lung carcinoma (SCLC).

Expression of the neural cell adhesion molecule (NCAM) on small-cell lung carcinoma (SCLC) cell lines and tumour tissue has been investigated. Cell lines were found to express highly sialylated NCAM. Neuraminidase treatment revealed the presence of the 140- and 120-kDa isoforms with differential expression of a 95-kDa protein. Similar data were obtained with SCLC tumour tissues. These results were corroborated by Northern blotting where mRNA of 6.7 and 5.5 kb coding for the 140- and 120-kDa isoforms, respectively, were identified. In a few tumours, a weaker band of 7.4-kb mRNA coding for the 180-kDa NCAM was also identified. This result could not be confirmed biochemically due to shortage of material. Finally, a 5-kb transcript was identified in all SCLC samples examined. The NCAM isoform coded by this mRNA remains unknown. Using the polymerase chain reaction (PCR), we have demonstrated the presence of the VASE mini-exon in some isoforms of SCLC NCAM. The VASE mini-exon sequence in human SCLC differs from the published murine sequence by only one base change. This substitution does not result in altered amino-acid sequence.

Amino Acid Sequence↗
PubMed1992

The cytotoxic action of lymphokine activated killer cells upon the human glioma cell line U251 is stimulated by bispecific monoclonal antibody (MoAb) constructs.

The ability of IL-2 stimulated mononuclear cells to kill the human glioblastoma cell line U251 has been investigated. Highest cytotoxic activity was generated in low cell density cultures incubated for 15 days with 250-1000 U/ml IL-2. Sub-optimal killing was noted, with cells only exposed to IL-2 for three days. Under the latter conditions, bispecific monoclonal antibodies (MoAbs) of either anti-CD3 or anti-CD16 and an anti-NCAM MoAb stimulated LAK cell activity markedly. Anti-CD16 conjugates were found more effective than anti-CD3 and (Fab')2 constructs more efficacious than those made with whole Ig molecules. Maximal stimulation of LAK cell activity was noted with bispecific MoAbs. Little effect was observed with either single or mixtures of monomeric MoAbs. Furthermore, no effect of bispecific MoAbs was observed when target cells lacked expression of NCAM. These results could be of clinical importance as it is not always feasible to screen LAK cells for optimal activity before administration to patients. Whilst bispecific MoAbs have no effect on optimally stimulated LAK cells, they are not inhibitory and can stimulate killing under sub-optimal IL-2 stimulation.

Antibodies, Monoclonal↗
PubMed1992

Immunomagnetic manipulation of hematopoietic cells: a review of current technology.

During the last decade, immunomagnetic separation of cells has become popular due to the simplicity and speed of the technology. A variety of magnetic materials have been developed that have fundamentally different characteristics. Some of these act as true colloids and have the properties of solutions, while others are larger and are based on the polymerization of materials, such as styrene, in the presence of magnetite. In this article, the different magnetic matrices are discussed and reviewed with respect to their use for the separation of cells of the hematopoietic system. Additionally, a brief introduction into the field of immunomagnetic separation of nucleic acids is presented, as this technology may be used to perform investigations at the molecular level on hematopoietic cells.

Erythrocytes↗
PubMed1992

Phase I/II study of iodine 131 metaiodobenzylguanidine in chemoresistant neuroblastoma: a United Kingdom Children's Cancer Study Group investigation.

PURPOSE: The goal of this study was to evaluate the toxicity of iodine 131 metaiodobenzylguanidine (mIBG) in metastatic neuroblastoma. PATIENTS AND METHODS: A multicenter phase I study of 131I mIBG has been undertaken by the United Kingdom Children's Cancer Study Group (UKCCSG) in children with advanced chemoresistant neuroblastoma. Activity prescription was based on a prescribed whole-body radiation dose, which was established for individual patients by performing an initial tracer investigation with 75 MBq of 131I mIBG. An activity was derived from this pharmacokinetic study that would deliver an initial whole-body-absorbed radiation dose of 1 Gy. Subsequent dose escalations were based on observed toxicity. RESULTS: Twenty-five patients, aged 1 to 10 years, were treated with prescribed whole-body dose levels of 1.0 Gy (n = 2), 2.0 Gy (n = 13), and 2.5 Gy (n = 10). This necessitated administration of 2.4 to 12.1 GBq of activity. Hematologic, hepatic, kidney, and adrenal toxicity were observed, with bone marrow suppression being the principal dose-limiting toxicity. Bone marrow toxicity increased with prescribed whole-body-absorbed radiation dose, with 80% of patients developing grade 3 or 4 thrombocytopenia at a prescribed whole-body radiation dose of 2.5 Gy. Objective evidence of tumor response was seen in soft tissue (primary or nodal disease), bone, and bone marrow, with an overall response rate of 33% (partial response, n = 8; static disease, n = 9; progressive disease, n = 7). CONCLUSIONS: This study has established an effective method of activity prescription that predicts subsequent toxicity, with the maximally tolerated dose being sufficient activity to deliver a whole-body-absorbed radiation dose of 2.5 Gy. The objective response rate is comparable to other single agents in chemoresistant neuroblastoma and suggests that 131I mIBG may be a useful method for targeting radiotherapy in metastatic neuroblastoma.

3-Iodobenzylguanidine↗
PubMed1992

Neuroblastoma in the very young child: biological considerations.

Neuroblastoma is one of the childhood malignancies that frustrates both the clinical and scientist. Clearly, some forms of the disease are relatively benign and the patient can expect to be cured. However, even today, Stage 4 neuroblastoma is one of the childhood malignancies where the overall prognosis remains very poor. Despite extensive investigations into the biology of the disease, little has been gleaned about the underlying causes of the tumour and what truly separates good and poor risk disease. Fortunately, patients under the age of one with neuroblastoma often fall into the good risk group. Many people now believe that neuroblastoma is not just one disease, but several. Some forms of the tumours may, in fact, not be truly malignant. The data that has led to this conclusion and the biological characteristics that are associated with the different forms of the neuroblastoma will be reviewed. In addition, a brief outline of new studies which may identify some of the factors associated with the neuroblasts ability to metastasise will be discussed.

Biomarkers, Tumor↗
PubMed1991

Alpha-smooth-muscle actin and desmin expressions in human neuroblastoma cell lines.

The neural crest gives rise to a variety of tissues, including peripheral neurons, Schwann cells, melanocytes and ectomesenchymal cells, which include the smooth-muscle cells of large arteries. Cell lines derived from neuroblastoma (a neural-crest tumor) exhibit at least 2 distinct morphological cell types, a neuroblastic phenotype (N-type) and an epithelial-like phenotype (S-type) with characteristics of substrate-adhesiveness. We have analyzed 17 human neuroblastoma cell lines using a panel of monoclonal antibodies (MAbs) against cytoskeletal proteins. Three neuroblastoma cell lines (KP-N-SI, KP-N-YN and SMS-KCN) bound an alpha-smooth-muscle actin antibody. In addition, one of these lines (KP-N-SI) bound anti-desmin MAbs as determined by indirect immunofluorescence. A total of 8 cloned cell lines were obtained from the above parent cell lines. These were composed of either N- or S-type cells and were confirmed to have the same neuroblastoma origin as each parent cell line by chromosomal analysis. Alpha-smooth-muscle actin and desmin were demonstrated in the S-type cloned cells by indirect immunofluorescence, as well as by 2-dimensional Western blot analysis. These results were confirmed by Northern blot analysis using a specific probe (pSH alpha SMA-3' UT) to human alpha-smooth-muscle actin mRNA. These ascertain the presence of alpha-smooth-muscle actin and desmin in neuroblastoma cell lines. These data show that, in addition to giving rise to cells with neural, Schwann-cell and melanocyte markers, neuroblastoma can also give rise to the cells expressing smooth-muscle cell markers.

Actins↗