Biomedical subjects

N Howells

Publications and source records attributed to N Howells.

At least 19 recordsLinked to original sources

PubMed2001

Soluble CD44 inhibits melanoma tumor growth by blocking cell surface CD44 binding to hyaluronic acid.

Proteolytic cleavage of the extracellular domain of CD44 from the surface of cells has been observed recently in different cell types. In cell culture supernatants of human melanoma cell lines a 70 kDa soluble CD44 protein (solCD44) was detected at concentrations of 250-300 ng/ml. Protease inhibitor studies revealed that serine proteases and metalloproteases are involved in the cleavage of CD44 from the surface of melanoma cells. To analyse a possible function of soluble CD44 a human malignant melanoma cell line was stably transfected with cDNAs encoding either wild type soluble CD44s or mutated forms with defective HA binding properties (CD44sR41A and CD44sR150A/R154A). Soluble CD44s almost completely inhibited hyaluronic acid binding by melanoma cells, whereas soluble CD44 mutated in the HA binding domain had no effect. When cultivated on hyaluronic acid, melanoma cell proliferation was induced by 30% for both the parental and the control transfected cells. This increase in proliferation was blocked completely in solCD44s-secreting transfectants, whereas solCD44sR41A and solCD44sR150A/R154A-secreting cells again showed hyaluronic acid-induced cell proliferation. These cell lines were subcutaneously injected into MF1 nu/nu mice to compare their growth as tumors in vivo. Compared to tumors derived from parental and control transfected cells, we observed a dramatic reduction of primary tumor growth with solCD44s expressing MM cells. Transfectants expressing solCD44s mutated in the HA binding domain in contrast developed fast-growing primary tumors. These results provide strong evidence that direct solCD44 interactions with hyaluronic acid interfere competitively with processes induced by hyaluronic acid binding to surface CD44. Autocrine, or drug-induced secretion of solCD44 by human melanoma cells may thus exert potent antitumoral effects in vivo.

Animals↗

PubMed2000

CD44 expression and regulation during mammary gland development and function.

The CD44v6 epitope has been widely reported to be expressed in human mammary carcinomas, yet its prognostic significance is controversial and its function in mammary tumors and mammary glands is unknown. To begin to resolve these issues, we analysed in detail the normal postnatal expression patterns and regulation of the CD44v6 epitope in murine mammary glands. We demonstrate that significant CD44v6 epitope expression is first seen during puberty, and that after puberty CD44v6 epitope expression follows the estrous cycle. CD44v6 epitope expression is observed in the myoepithelium and also less widely in luminal epithelial cells. During lactation, CD44v6 epitope expression is turned off and reappears during involution. The CD44 variant isoform bearing the v6 epitope is CD44v1-v10. Using HC11, a mammary epithelial cell line with stem cell characteristics, and facilitated by the cloning of the murine CD44 promoter, we show that growth factors and hormones which regulate ductal growth and differentiation modulate CD44 transcription. Together our data suggest that the CD44v6 epitope is expressed in mammary epithelial stems cells and in lineages derived from these cells, and that CD44v6 expression is regulated in part by hormones and growth factors such as IGF-1 and EGF which regulate the growth and differentiation of the mammary epithelium. The function of these same growth factors and hormones is often perturbed in mammary carcinomas, and we suggest that CD44v6 expression in tumors reflects this perturbation. We conclude that the expression of the CD44v6 epitope observed in some mammary tumors reflects the stem cell origin of breast tumors, and that whether or not the CD44v6 epitope is expressed in a mammary tumor is determined by the differentiation status of the tumor cells.

Animals↗

PubMed1999

Inhibition of MT-450 rat mammary tumour growth by antibodies recognising subtypes of blood group antigen B.

Using subtractive immunization to identify cell surface epitopes expressed in a metastasis-specific fashion on cells of the rat MT-W9 mammary carcinoma model, we generated a monoclonal antibody called M-N#1. This antibody binds specifically to metastasizing cells of the MT-W9 series and also to certain other metastasizing rat mammary carcinoma cell lines. We demonstrate that the M-N#1 antibody recognizes a fucosylated N-glycosyl sugar modification, and furthermore show that the epitope specificity of the M-N#1 antibody is for blood group antigen B subtypes 2, 3 and 4 with slight cross-reactivity with blood group antigen A subtype 2. The expression of these carbohydrate epitopes on MT-450 cells is functionally important, because the M-N#1 antibody efficiently inhibits MT-450 tumour growth in spontaneous metastasis assays. These results suggest that expression of the subtypes of blood group antigen B recognized by the M-N#1 antibody does not directly participate in the metastatic cascade but rather confers a growth or survival advantage on the tumour cells.

ABO Blood-Group System↗

PubMed1998

Complementary therapists and cancer patient care: developing a regional network to promote co-operation, collaboration, education and patient choice.

Complementary therapies, particularly aromatherapy, reflexology and relaxation techniques are increasingly valued by cancer patients. However, many health professionals doubt their value, and often question whether therapists claim inappropriate benefits, lack understanding of cancer-related issues and pose a potential danger to patients. The Lynda Jackson Macmillan Centre for Cancer Support and Information, which has provided therapies since 1993, explored some of these issues and attempted to identify common areas of interest, possible collaboration, and an additional source of meeting patient needs. Two hundred and fifty questionnaires were sent to aromatherapists and reflexologists within the region served by the hospital to: (1) identify and profile interested therapists; (2) assess the need for cancer-related educational programmes; and (3) address some of the professionals' concerns. One hundred and four responses described work patterns, qualifications, cancer-related experience, the contribution of therapies to cancer care and interest in cancer-related training. A lack of information on cancer was identified. Therapists appeared to be working sensitively, even over-cautiously, and misgivings concerning this group appeared to be unfounded. Subsequent workshops resulted in a therapists' network, whose members collaborate with the centre in various ways. Patients and carers appreciate access to therapists informed about cancer, treatments and related issues.

Community Networks↗

PubMed1998

Development of an aromatherapy service at a Cancer Centre.

The aromatherapy service at the Cancer Support and Information Centre (CSIC) of this regional Cancer Centre has been continually assessed since its inception in 1993. New methods of assessing complementary therapies, based on the 'therapy-as-practised', have been explored. The present study evaluates the service following changes made after an initial pilot. The professional aromatherapist developed an evaluation tool, and formal questionnaires were limited to the Hospital Anxiety and Depression Scale (HADS). HADS was completed before and after a course of six aromatherapy sessions. Of 89 patients referred, 58 patients completed the six sessions. Referrals were made by health professionals working in the Cancer Centre and in the CSIC. The majority of patients were female with breast cancer and were receiving radical oncological treatment. Tension, stress and anxiety/fear were the most common reasons for referral, and this was reflected in high initial HADS scores. There were significant improvements in HADS scores in the 58 patients completing the course (mean anxiety, depression, and combined scores dropped from 8.9 to 6.2 6.1 to 4.0 and 15.0 to 10.2, respectively, P < 0.001). Fifty per cent or more of the sample reported a significant improvement in the eight most commonly assessed symptoms. The therapist was initially cautious about using questionnaires, but she gained confidence in using HADS as an assessment tool. The areas covered by her own evaluation tools were broadly comparable to established instruments such as the EORTC QLQ-C30. We conclude that aromatherapy massage has a role in reducing psychological distress, and improving symptom control in cancer patients. Further service evaluation is needed to promote appropriate referral and effective planning of treatment, and to justify cost. Given the multifaceted nature of complementary therapies, the need to develop new research methodologies is acknowledged.

Adult↗

PubMed1998

Identification of IHABP, a 95 kDa intracellular hyaluronate binding protein.

The extracellular matrix component hyaluronan is believed to play important roles in various processes of organogenesis, cell migration and cancer. Recognition of and binding to hyaluronan is mediated by cell surface receptors. Three of them, CD44, ICAM-1 and RHAMM (receptor for hyaluronic acid mediated motility), have been identified. A cDNA clone designated RHAMM turned out to possess transforming capacity. Based on this published sequence, we isolated the complete cDNA of the murine gene. The cDNA comprises an open reading frame of 2.3 kb and encodes a 95 kDa protein. The protein carries a hyaluronan binding motif which binds to hyaluronan in vitro but not to heparin or chondroitin sulphate. It is ubiquitously expressed in normal cells and in all tumour cell lines irrespective of their metastatic properties. One tumour cell line, the metastatic Lewis lung carcinoma, expresses a larger 105 kDa variant form of the protein due to a genomic rearrangement. Antibodies raised against the 95 kDa protein were used for subcellular localization studies. The hyaluronan binding protein is not detectable at the cell surface but is rather localized exclusively intracellularly. Clearly, the sequence we have identified encodes a protein with properties substantially different to the RHAMM protein. We tentatively name the protein intracellular hyaluronic acid binding protein, IHABP.

3T3 Cells↗

PubMed1998

CD44 variant isoforms are essential for the function of epidermal Langerhans cells and dendritic cells.

Upon antigen encounter epidermal Langerhans cells (LC) and dendritic cells (DC) emigrate from peripheral organs and invade lymph nodes through the afferent lymphatic vessels and then assemble in the paracortical T cell zone and present antigen to T lymphocytes. Part of this process is mimicked by metastasizing tumor cells. Since splice variants of CD44 promote metastasis to lymph nodes we explored the expression of CD44 proteins on migrating LC and DC. We show that following antigen contact, LC and DC upregulate pan CD44 epitopes and epitopes encoded by variant exons v4, v5, v6 and v9. Antibodies against CD44 epitopes arrest LC in the epidermis, prevent the binding of activated LC and DC to the T cell zones of lymph nodes, and severely inhibit their capacity to induce a delayed type hypersensitivity reaction to a skin hapten in vivo. Our results demonstrate that CD44 splice variant expression is obligatory for the migration and function of LC and DC.

Cell Movement↗

PubMed1997

Interdomain binding mediates tumor growth suppression by the NF2 gene product.

The neurofibromatosis 2 (NF2) tumor suppressor gene encodes an intracellular membrane-associated protein, called merlin (or schwannomin), that belongs to the band 4.1 family of cytoskeleton-associated proteins. Inactivating NF2 mutations occur in several sporadic tumor types and have been linked to the NF2 disease, whose hallmark is the development of bilateral Schwann cell tumors (schwannomas) of the eighth cranial nerve. Two major alternatively spliced NF2 variants are expressed in normal tissues: 'NF2-17' lacking exon 16 and 'NF2-16' that contains exon 16 and encodes a merlin protein truncated at the C-terminus. We report that overexpression of NF2-17 in rat schwannoma cells inhibits their growth in vitro and in vivo, while NF2-16 fails to influence schwannoma growth. Tumor growth inhibition by merlin depends on an interdomain association occurring either in cis or in trans between the N- and C-termini. This association does not occur in the truncated NF2-16 protein nor in a mutant NF2-17 protein lacking C-terminal sequences. These data indicate that merlin has a unique mechanism of tumor suppression, inhibiting cell proliferation via self-association.

Animals↗

PubMed1997

An essential role for CD44 variant isoforms in epidermal Langerhans cell and blood dendritic cell function.

Upon antigen contact, epidermal Langerhans cells (LC) and dendritic cells (DC) leave peripheral organs and home to lymph nodes via the afferent lymphatic vessels and then assemble in the paracortical T cell zone and present antigen to T lymphocytes. Since splice variants of CD44 promote metastasis of certain tumors to lymph nodes, we explored the expression of CD44 proteins on migrating LC and DC. We show that upon antigen contact, LC and DC upregulate pan CD44 epitopes and epitopes encoded by variant exons v4, v5, v6, and v9. Antibodies against CD44 epitopes inhibit the emigration of LC from the epidermis, prevent binding of activated LC and DC to the T cell zones of lymph nodes, and severely inhibit their capacity to induce a delayed type hypersensitivity reaction to a skin hapten in vivo. Our results demonstrate that CD44 splice variant expression is obligatory for the migration and function of LC and DC.

Animals↗

PubMed1994

Degeneration of neural cells in the central nervous system of mice deficient in the gene for the adhesion molecule on Glia, the beta 2 subunit of murine Na,K-ATPase.

We generated mice, null mutant in the adhesion molecule on glia (AMOG), the beta 2 subunit of the murine Na,K-ATPase gene. These mice exhibit motor incoordination at 15 d of age, subsequently tremor and paralysis of extremities, and die at 17-18 d after birth. At these ages, the mutants have enlarged ventricles, degenerating photoreceptor cells, and swelling and degeneration of astrocytic endfeet, leading to vacuoles adjoining capillaries of brain stem, thalamus, striatum, and spinal cord. In tissue homogenates from entire brains of 16-17-d-old mutants, Na,K-ATPase activity and expression of the beta 1 subunit of the Na,K-ATPase and of the neural adhesion molecules L1, N-CAM, and MAG appear normal. We suggest that the mutant phenotype can be related primarily to reduced pump activity, with neural degeneration as a possible consequence of osmotic imbalance.

Adenosine Triphosphatases↗

PubMed1993

c-jun is essential for normal mouse development and hepatogenesis.

The proto-oncogene c-jun is the cellular homologue of v-jun, the transforming oncogene of the avian sarcoma virus 17 (ref. 1). c-jun encodes one major component of the AP-1 transcription factor complex and is expressed in many organs during mouse development and in the adult. Because of its rapid induction in cells following growth stimulation and the presence of AP-1 binding sites in the promoter regions of many genes, the c-Jun protein is thought to have important functions in cell proliferation and differentiation. But embryonic stem (ES) cells lacking c-Jun are viable and have a normal in vitro differentiation capacity, although c-Jun appears to be important for growth of teratocarcinomas in vivo. To define the function of c-jun better, targeted ES cells were used to generate mice lacking c-Jun. Here we report that heterozygous mutant mice appear normal, but embryos lacking c-Jun die at mid- to late-gestation and exhibit impaired hepatogenesis, altered fetal liver erythropoiesis and generalized oedema. Interestingly, c-jun-/- ES cells can participate efficiently in the development of all somatic cells in chimaeric mice except liver cells, further suggesting an essential function of c-Jun in hepatogenesis.

Animals↗

PubMed1993

Flavone acetic acid (FAA) with recombinant interleukin-2 (rIL-2) in advanced malignant melanoma. IV: Pharmacokinetics and toxicity of flavone acetic acid and its metabolites.

Flavone acetic acid (FAA) was administered at a dose of 4.8 g m-2 over 1 h to patients with advanced malignant disease in combination with Interleukin II. A new high performance liquid chromatography method is described to determine both the parent compound and eight drug-related products, and the conditions required to determine these components in plasma are discussed. The half-life over the first 8 h was 2.3 h, but the terminal clearance of the drug was extremely slow. Severe (WHO Grade 4) hypotension was observed in some patients. However, incidence of this did not appear to be associated with any differences in FAA plasma concentrations, nor were there differences in FAA clearance between those patients whose tumour responded to the drug combination and those who did not.

Antineoplastic Agents↗

PubMed1992

Phase I study of intravenous 4-hydroxyanisole.

4-Hydroxyanisole is a depigmenting agent which has been shown to have activity against malignant melanoma when given intra-arterially in man. An intravenous dose escalation study has been carried out with the aim of obtaining maximum plasma concentrations in a 5 day schedule. 8 patients entered this study which was stopped because of drug toxicity after 3 patients had been treated at the third dose escalation of 15 g/m2. 2 patients had WHO grade 4 liver and one also grade 4 renal toxicity and another had grade 4 haemoglobin toxicity. Extrapolated plateau plasma levels between 112 and 860 mumol/l were obtained, which in vitro studies suggested would be cytotoxic. Hopefully, newer analogues will have a greater specificity for the melanin pathway with less toxicity.

Anisoles↗

PubMed1991

Comparison of ondansetron and ondansetron plus dexamethasone as antiemetic prophylaxis during cisplatin-containing chemotherapy.

Ondansetron, a serotonin antagonist, is effective in controlling the emesis associated with cancer chemotherapy; however, emesis in patients receiving high-dose cisplatin is poorly controlled by ondansetron alone. Dexamethasone is an effective antiemetic with no known interaction with serotonin receptors and was thus chosen for study in combination with ondansetron. 31 patients (30 male, 1 female; median age 28.5 years, range 18-49) receiving a 4-day course of a chemotherapy regimen containing cisplatin (100-120 mg/m2) for metastatic germ-cell tumours were entered in a randomised, double-blind, cross-over trial comparing oral ondansetron plus placebo with oral ondansetron plus dexamethasone as antiemetic prophylaxis. Ondansetron (8 mg every 8 h) was given to all patients for 8 days from the start of chemotherapy. Patients were given 8 mg of dexamethasone or placebo every 8 h starting 2 h before cisplatin (on day 4) and continuing for six doses (ie, for 2 days only). A second course of chemotherapy began 14 days after the start of the first, during which patients crossed over to the alternative antiemetic regimen. Results were available from 27 patients. In the 24-48 h after cisplatin 78% of patients taking ondansetron plus dexamethasone reported complete or major control of emesis compared with 30% of those taking ondansetron plus placebo (p = 0.001). Cross-over analysis showed a significant advantage for ondansetron plus dexamethasone in the control of nausea (p = 0.013) and emesis (p less than 0.001) over the 8-day study. 24 of 26 patients expressed a preference for the combination therapy (p less than 0.001). Ondansetron plus dexamethasone is effective antiemetic prophylaxis for high-dose cisplatin chemotherapy, has few side effects, and is active when given orally.

Administration, Oral↗

PubMed1991

A phase II study of ondansetron as antiemetic prophylaxis in patients receiving carboplatin for advanced ovarian cancer. The North Thames Ovary Group.

Thirty four patients who were receiving carboplatin 400 mg/m2 for advanced epithelial ovarian cancer were treated with ondansetron antiemetic prophylaxis. Ondansetron was given as 4 mg oral +4 mg iv 30 minutes prior to carboplatin followed by 8 mg oral tds for 5 days. Of the evaluable patients complete or major control of emesis on day one was achieved in 94% of previously untreated patients and 81% of patients refractory to conventional antiemetic therapy. For the 5 day period as a whole 88% of untreated patients and 69% of those with refractory emesis reported complete or major control of nausea and vomiting. Fifteen patients noted no side effects with mild headache (30%) and constipation (21%) the most frequent problems in the remainder. Ondansetron is effective antiemetic prophylaxis for carboplatin chemotherapy and should allow the majority of these patients to be managed on an out-patient basis.

Adult↗

PubMed1989

Induction of tumour hypoxia by a vasoactive agent. A combined NMR and radiobiological study.

The effect of hydralazine treatment on 3 murine tumours (RIF-1, KHT and 16/C) was monitored using 31P-NMR. Changes in the 31P-NMR spectrum are compared with measurements of radiobiological hypoxic fraction (RHF) in the RIF-1 and KHT. Hydralazine is known to reduce temporarily blood flow in experimental tumours, and thus cause a transient increase in the RHF to 100% (in RIF-1 and KHT). This correlates with a decline in energy status as measured by 31P-NMR (i.e. there was an increase in Pi in all three tumours). Time-course data from the RIF-1 and KHT tumours show that maintenance of anaesthesia prolongs the hypoxia induced by hydralazine.

Animals↗

PubMed1989

Enhancement of the anti-tumor effect of melphalan in experimental mice by some vaso-active agents.

A comparison is made between the vaso-active agents hydralazine, nifedipine, and verapamil for their ability to increase the anti-tumor effectiveness of melphalan. Treatment of mice with hydralazine (5 mg/kg) 15 mins after melphalan increases by a factor of approximately 2.5 melphalan-induced delay in growth of either the RIF-1 or KHT tumors. Similar enhancements are obtained when measurement is made of the surviving fraction of tumor cells in vitro following treatment in vivo with hydralazine and melphalan. Further, tumor cell kill is also increased when nifedipine is administered with melphalan compared with the effect of melphalan alone. These enhanced effects are observed if the vaso-active agents are given before or after melphalan. Hydralazine (5 mg/kg) induces close to 100% radiobiological hypoxia in the RIF-1 and KHT tumors. In contrast, Nifedipine has no effect on tumor hypoxic fraction at a dose of 10 mg/kg although the anti-tumor effectiveness of melphalan is substantially increased. However, a higher dose of 50 mg/kg nifedipine causes a large increase in tumor hypoxic fraction, an effect that persists for several hours. Verapamil causes no change in the fraction of hypoxic cells in the KHT tumor and increases, only slightly, the anti-tumor effect of melphalan.

Animals↗

PubMed1989

Induction of tumour hypoxia post-irradiation: a method for increasing the sensitizing efficiency of misonidazole and RSU 1069 in vivo.

It is known that hydralazine can decrease blood flow to experimental murine tumours. A consequence of this, in the KHT sarcoma, is the induction of close to 100 per cent radiobiological hypoxia, which lasts for nearly 2 h following i.v. injection of 5 mg/kg hydralazine to the mouse. This phenomenon is exploitable in order to increase the apparent sensitizing efficiency of the nitroheterocyclic radiosensitizers, misonidazole and RSU 1069, and is demonstrated using the treatment schedule: sensitizer----60 min----X-rays----1 min----hydralazine. Such a strategy will first take advantage of the radiosensitizing properties of the nitroimidazole, then after irradiation the hydralazine should allow expression of the differential toxicity towards hypoxic cells known to occur with misonidazole and RSU 1069. Misonidazole gives an enhancement ratio (ER) of 1.3 at 100 mg/kg, rising to 2.0 at 1000 mg/kg. Where hydralazine is given after irradiation, no additional cell kill is observed with 1000 mg/kg. In contrast, at lower doses of misonidazole, hydralazine induces a substantial increase in cell killing such that the ER obtained with 100 mg/kg is the same as that achieved with 1000 mg/kg misonidazole when used alone with radiation. Similarly, 20 mg/kg RSU 1069 with radiation followed by hydralazine is equivalent to the radiosensitizing effect of 80 mg/kg RSU 1069 without hydralazine. In addition, doses of RSU 1069 that normally give no radiosensitization (5 or 10 mg/kg) produce substantial increases in cell killing when combined with hydralazine.

Animals↗