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J H Hendry

Publications and source records attributed to J H Hendry.

At least 19 recordsLinked to original sources
PubMed2003

Intestinal crypt clonogens: a new interpretation of radiation survival curve shape and clonogenic cell number.

Estimates of the clonogen content (number of microcolony-forming cells) of murine intestinal crypts using microcolony assays show an apparent dependence on the radiation dose used in the assay of clonogen content. Crypt radiation survival curves often show increased curvature beyond that expected on the basis of the conventional linear-quadratic model. A novel form of crypt survival curve shape is proposed based on two contributory mechanisms of crypt killing. Six previously published sets of microcolony data were re-analysed using a dual-kill model, where target cells are killed by two contributory mechanisms, each described by a linear-quadratic function of dose. The data were analysed as two series--high-dose rate and low-dose rate irradiation. The data were fitted to the models using direct maximization of a quasi-likelihood, explicitly allowing for overdispersion. The dual-kill model can reproduce both the apparent dose-dependence of the clonogen estimates and the high-dose curvature of the dose-response curves. For both series of data the model was a significantly better fit to the data than the standard linear-quadratic model, with no evidence of any systematic lack of fit. The parameters of the clonogenic cell component of the model are consistent with other studies that suggest a low clonogen number (somewhat less than five) per crypt. The model implies that there is a secondary mechanism decreasing clonogen survival, and hence increasing clonogen number estimates, at high doses. The mechanisms underlying the modification of the dose-response are unclear, and the implied mechanisms of, for example, slow growth, induced either directly in the surviving cells or indirectly through stromal injury or bystander effects are only speculative. Nevertheless, the model fits the data well, demonstrating that there is greater kill at high doses in these experimental series than would be expected from the conventional linear-quadratic model. This alternative model, or another model with similar behaviour, needs to be considered when analysing in detail and interpreting microcolony data as a function of dose. The implied low number of < or = 5 of these regenerative and relatively radioresistant clonogenic cells is distinct from a similar number of much more radiosensitive precursor stem cells which undergo early apoptosis after doses around 1 Gy.

Animals↗
PubMed2002

Development of a novel rapid assay to assess the fidelity of DNA double-strand-break repair in human tumour cells.

Cellular survival following ionising radiation-mediated damage is primarily a function of the ability to successfully detect and repair DNA double-strand breaks (DSBs). Previous studies have demonstrated that radiosensitivity, determined as a reduction in colony forming ability in vitro, may be related to the incorrect repair (misrepair) of DSBs. The novel rapid dual fluorescence (RDF) assay is a plasmid-based reporter system that rapidly assesses the correct rejoining of a restriction-enzyme produced DSBs within transfected cells. We have utilised this novel assay to determine the fidelity of DSB repair in the prostate tumour cell line LNCaP, the bladder tumour cell line MGH-U1 and a radiosensitive subclone S40b. The two bladder cell lines have been shown in previous studies to differ in their ability to correctly repair plasmids containing a single DSB. Using the RDF assay we found that a substantial portion of LNCaP cells [80.4 +/- 5.3(standard error)%] failed to reconstitute reporter gene expression; however, there was little difference in this measure of DSB repair fidelity between the two bladder cell lines (48.3 +/- 3.5% for MGH-U1; 39.9 +/- 8.2% for S40b). The RDF assay has potential to be developed to study the relationship between DSB repair fidelity and radiosensitivity as well as the mechanisms associated with this type of repair defect.

Cell Survival↗
PubMed2002

Practical methods for compensating for missed treatment days in radiotherapy, with particular reference to head and neck schedules.

Unscheduled interruption of a radiotherapy treatment can lead to significant loss in local tumour control, particularly in tumours that repopulate rapidly. General guidelines for dealing with such treatment gaps have been issued by the Royal College of Radiologists and more specific advice on the use of compensation methods has been published previously [Hendry et al., Clin Oncol 1996;8:297-307; Slevin et al., Radiother Oncol 1992;24:215-220]. This article further elaborates on the practical application of these methods. It sets out the main considerations arising in the especially critical case of head and neck treatments and simple calculations are used to illustrate the approaches which may be adapted for particular situations. Radiobiological parameter values are suggested for use in the calculations, but these may require modification in the light of further research in this important area.

Appointments and Schedules↗
PubMed2002

Role of damage-sensing/processing genes in the radiation response of haemopoietic in vitro colony-forming cells.

PURPOSE: To characterize the role of various cellular damagesensing, processing and survival genes in the in-vitro radiosensitivity of haemopoietic colony-forming cells. MATERIALS AND METHODS: Bone marrow cells from a range of different gene-knockout mice were irradiated in vitro with graded radiation doses and assayed for colony-forming efficiency. RESULTS: Colony-forming efficiency in the nulls was often lower by up to threefold compared with the wild-types. This was noticeable in particular for the atm, bax and p21 nulls. Radiosensitivity was markedly increased in the scid mouse (about 2.3-fold), more than in the atm null mouse (about 1.7-fold). There was resistance in the p53 nulls compared with the wild-types, using two different background strains, that gave similar results. There was slight sensitization in the p21 nulls. In the bcl-2 nulls, there was sensitization at low dose, but not at high dose. In contrast, in the bax nulls, there was protection at low dose, but again not at high dose. The heterozygotes for p53, bcl-2 and bax responded similarly to the wild types, so that no gene dosage effects were identified. CONCLUSIONS: These studies are the first to elucidate the role of as many as six relevant genes in the radiosensitivity of a single cell type. They show the greater importance of 'survival' genes at lower cytotoxic doses of radiation compared with the greater importance of 'damage-sensing' genes at higher doses.

Animals↗
PubMed2001

Increased levels of comet-detected spermatozoa DNA damage following in vivo isotopic- or X-irradiation of spermatogonia.

To investigate whether DNA damage arising in spermatogenic germ cells can be detected in resultant sperm, we have irradiated murine testis and collected spermatozoa from the vas deferens 45 days later. These cells were derived from spermatogonia present at the time of irradiation. Two forms of irradiation were used, external X-rays (4Gy) and internal auger electrons from contamination of the male mouse with the isotope Indium-114m (1.85MBq), which was localised in the testis. Both forms of irradiation produced a profound fall in vas deferens sperm count and testis weight, Indium-114m being more effective. Using the neutral Comet assay for double strand break detection, significant increases in sperm comet tail length and moment were observed. The levels of damage were similar for both treatments. Care had to be taken during the assay to distinguish between sperm and somatic cells as the proportion of the latter increased after irradiation. We conclude that the comet assay can detect DNA damage in spermatozoa after the in vivo exposure of male germ cells to a known testicular genotoxic agent. The assay may be useful for the assessment of sperm DNA damage (double stranded) associated with male infertility and post-fertilization developmental abnormalities in the offspring.

Animals↗
PubMed2001

Ribozyme minigene-mediated RAD51 down-regulation increases radiosensitivity of human prostate cancer cells.

The strand transferase RAD51 is a component of the homologous recombination repair pathway. To examine the contribution of RAD51 to the genotoxic effects of ionising radiation, we have used a novel ribozyme strategy. A reporter gene vector was constructed so that expression of an inserted synthetic double-stranded ribozyme-encoding oligonucleotide would be under the control of the cytomegalovirus immediate-early gene enhancer/promoter system. The prostate tumour cell line LNCaP was transfected with this vector or a control vector, and a neomycin resistance gene on the vector was used to create geneticin-resistant stable cell lines. Three stable cell lines were shown by western blot analysis to have significant down-regulation of RAD51 to 20-50% of the levels expressed in control cell lines. All three cell lines had a similar increased sensitivity to gamma-irradiation by 70 and 40%, respectively, compared to normal and empty vector-transfected cells, corresponding to dose-modifying factors of approximately 2.0 and 1.5 in the mid-range of the dose-response curves. The amount of RAD51 protein in transfected cell lines was shown to strongly correlate with the alpha parameter obtained from fitted survival curves. These results highlight the importance of RAD51 in cellular responses to radiation and are the first to indicate the potential use of RAD51-targeted ribozyme minigenes in tumour radiosensitisation.

Base Sequence↗
PubMed2001

Normal tissue radiobiology: from the laboratory to the clinic.

This manuscript is in four parts, presenting the four talks given in a symposium on normal tissue radiobiology. The first part addresses the general concept of the role of parenchymal cell radiosensitivity vs. other factors, highlighting research over the last decade that has altered our understanding of factors underlying normal tissue response. The other three parts expand on specific themes raised in the first part dealing in particular with (1) modifications of fibroblast response to irradiation in relation to the induction of tissue fibrosis, (2) the use of the linear-quadratic equation to model the potential benefits of using different means (both physical and biologic) of modifying normal tissue response, and (3) the specific role of the growth factor TFG-beta1 in normal tissue response to irradiation. The symposium highlights the complexities of the radiobiology of late normal tissue responses, yet provides evidence and ideas about how the clinical problem of such responses may be modified or alleviated.

Animals↗
PubMed2001

Anti-8-oxo-2'-deoxyguanosine phage antibodies: isolation, characterization, and relationship to disease states.

We have used human single chain Fv (scFv) phage display antibody libraries to isolate recombinant antibodies against the DNA adduct 8-oxo-2'-deoxyguanosine (8-oxodG). One of these scFvs (175G) bound to several 8-oxodG-containing oligonucleotides whilst demonstrating no cross-reactivity with G-containing control oligonucleotides, and bound to 8-oxodG lesions introduced into DNA by treatment with methylene blue and white light. In addition, 175G inhibited the cleavage of an 8-oxodG-containing oligonucleotide by the Escherichia coli enzyme formamidopyrimidine-DNA glycosylase (Fpg). The nucleotide sequence of the 175G V(H) gene segment was 98% homologous to the published V(H) sequence of a human hybridoma derived from a patient with systemic lupus erythematosus (SLE). Sera from two SLE patients bound to damaged DNA, and this binding could be inhibited by 175G. The use of human scFv phage display libraries has thus produced a unique reagent with specificity for 8-oxodG, which may have a role in damage detection and quantitation and in modifying DNA repair activity. 175G also offers support to the hypothesis that SLE might be associated with oxidative damage to DNA.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2001

Genomic instability: potential contributions to tumour and normal tissue response, and second tumours, after radiotherapy.

PURPOSE: Induced genomic instability generally refers to a type of damage which is transmissible down cell generations, and which results in a persistently enhanced frequency of de novo mutations, chromosomal abnormalities or lethality in a significant fraction of the descendant cell population. The potential contribution of induced genomic instability to tumour and normal tissue response, and second tumours, after radiotherapy, is explored. RESULTS: The phenomenon of spontaneous genomic instability is well known in some rare genetic diseases (e.g. Gorlin's syndrome), and there is evidence in such cases that it can lead to a greater propensity for carcinogenesis (with shortened latency) which is enhanced after irradiation. It is unclear what role induced genomic instability plays in the response of normal individuals, but persistent chromosomal instability has been detected in vivo in lymphocytes and keratinocytes from irradiated normal individuals. Such induced genomic instability might play some role in tumour response in a subset of tumours with specific defects in damage response genes, but again its contribution to radiocurability in the majority of cancer patients is unclear. In normal tissues, genomic instability induced in wild-type cells leading to delayed cell death might contribute to more severe or prolonged early reactions as a consequence of increased cell loss, a longer time required for recovery, and greater residual injury. In tumours, induced genomic instability reflected in delayed reductions in clonogenic capacity might contribute to the radiosensitivity of primary tumours, and also to a lower incidence, longer latency and slower growth rate of recurrences and metastases. CONCLUSIONS: The evidence which is reviewed shows that there is little information at present to support these propositions, but what exists is consistent with their expectations. Also, it is not yet clear to what extent mutations associated with genomic instability, particularly gene polymorphisms, or other low penetrant gene mutations, contribute to the recognized spectrum of normal tissue radiosensitivity amongst cancer patients, or in the general population. Tests for such genetic modifications may help in the search for more accurate prognostic markers of response, which hopefully could be used in addition to other strategies to further improve the outcome for cancer patients given radiotherapy.

Cell Division↗
PubMed2001

Consequential late effects in normal tissues.

Unconventional, more aggressive irradiation protocols are usually associated with aggravation of acute reactions. In recent clinical studies, this has resulted in modulation of late effects in the same organ. This phenomenon has been termed consequential late effect (CLE). Correlations between acute and late effects have been reported in a number of tissues. Moreover, some radiobiological parameters may be used to differentiate between consequential and generic late effects: Dose fractionation and overall treatment time have a similar effect on acute and consequential responses, but opposing effects on generic late effects. Modulation of acute effects will affect the consequential component of late sequelae. Similarly, it will be influenced by the irradiated volume if a volume effect exists for the acute response. Moreover, markers for the acute response should be predictive for consequential effects. The present review gives preclinical and clinical evidence for CLE. These are predominantly found in organ systems where the acute response (of the epithelial lining) is associated with an impairment of the barrier against mechanical or chemical stress, which may cause additional trauma to the underlying tissues. Therefore, CLE are mainly found in the urinary and intestinal system, in mucosa and, to some extent, in skin. In these tissues with a consequential component of the late sequelae, amelioration of the acute response to irradiation may be a useful approach to minimize late side effects of effective radiation therapy.

Digestive System↗
PubMed2001

The required number of treatment imaging days for an effective off-line correction of systematic errors in conformal radiotherapy of prostate cancer--a radiobiological analysis.

BACKGROUND AND PURPOSE: To use radiobiological modelling to estimate the number of initial days of treatment imaging required to gain most of the benefit from off-line correction of systematic errors in the conformal radiation therapy of prostate cancer. MATERIALS AND METHODS: Treatment plans based on the anatomical information of a representative patient were generated assuming that the patient is treated with a multi leaf collimator (MLC) four-field technique and a total isocentre dose of 72 Gy delivered in 36 daily fractions. Target position variations between fractions were simulated from standard deviations of measured data found in the literature. Off-line correction of systematic errors was assumed to be performed only once based on the measured errors during the initial days of treatment. The tumour control probability (TCP) was calculated using the Webb and Nahum model. RESULTS: Simulation of daily variations in the target position predicted a marked reduction in TCP if the planning target volume (PTV) margin was smaller than 4 mm (TCP decreased by 3.4% for 2 mm margin). The systematic components of target position variations had greater effect on the TCP than the random components. Off-line correction of estimated systematic errors reduced the decrease in TCP due to target daily displacements, nevertheless, the resulting TCP levels for small margins were still less than the TCP level obtained with the use of an adequate PTV margin of approximately 10 mm. The magnitude of gain in TCP expected from the correction depended on the number of treatment imaging days used for the correction and the PTV margin applied. Gains of 2.5% in TCP were estimated from correction of systematic errors performed after 6 initial days of treatment imaging for a 2 mm PTV margin. The effect of various possible magnitudes of systematic and random components on the gain in TCP expected from correction and on the number of imaging days required was also investigated. CONCLUSIONS: Daily variations of target position markedly reduced the TCP if small margins were used. Off-line correction of systematic errors can only partly compensate for these TCP reductions. The adequate number of treatment imaging days required for systematic error correction depends on the magnitude of the random component compared with the systematic component, and on the size of PTV margin used. For random components equal to or smaller than the systematic component, 3 consecutive treatment imaging days are estimated to be sufficient to gain most of the benefit from correction for current clinically used margins (6-10 mm); otherwise more days are required.

Humans↗
PubMed2001

Transgenerational effects of preconception paternal contamination with (55)Fe.

The conjecture that germline mutations induced by radiation exposure before conception may predispose subsequent offspring to cancer remains contentious. Previous experimental studies have shown that preconception paternal irradiation with (239)Pu induces perturbations in the hemopoietic systems of offspring and influences sensitivity to a secondary carcinogen. In the present study, male DBA2 mice were injected intravenously with the Auger electron emitter (55)Fe (4 kBq g(-1)) 18 or 84 days before mating with normal females. Comet analysis showed an increased incidence of DNA strand breaks in sperm from contaminated animals after 84 days, but not after 18 days, indicating spermatogonial rather than spermatid damage. Offspring were either assayed for changes in bone marrow stem cells and committed progenitors or challenged with the chemical carcinogen methyl nitrosourea (MNU, 50 mg/kg) at 10 weeks of age and monitored for the onset of malignancy. Offspring from irradiated fathers had normal peripheral blood profiles, although the stem cell population was amplified in offspring arising from those exposed to (55)Fe at 84 days before conception. Exposure to MNU significantly increased the incidence of lympho-hemopoietic malignancies in offspring from the 84-day group, but not in those from the 18-day group. These findings support the hypothesis that aberrations that are potentially leukemogenic may be transmitted to offspring after radiation damage to the paternal germline.

Animals↗
PubMed2001

Differential radiosensitivity of hypothalamo-pituitary function in the young adult rat.

Cranial irradiation in children and adults often results in irreversible hypopituitarism. The earliest and most common endocrine abnormality is GH deficiency, often followed by other pituitary hormone deficits. We investigated whether a similar pattern of progressive hypopituitarism could be reproduced in an animal model. Different doses of cranial irradiation were delivered to the hypothalamo-pituitary region of normal adult male rats, and the effects on their subsequent growth, pituitary weight and hormone contents were studied. Animals received cranial irradiation with 300 kV X-rays at doses of 0, 20, 22 or 24 Gy (n=15 per group) and five animals from each group were killed at 8, 14 or 20 weeks after irradiation. Their anterior pituitary glands were weighed and assayed for GH, LH, TSH, ACTH and prolactin (PRL) content. All three doses of irradiation reduced body weight compared with that in non-irradiated controls and compromised growth between 8 and 20 weeks. Pituitary weight increased between 8 and 20 weeks in control rats, whereas it decreased significantly in the irradiated animals. Irradiation induced time- and dose-dependent changes in pituitary hormone contents. GH and PRL were most sensitive and decreased by more than 90% after irradiation; TSH contents were unaffected 8 weeks after the lowest dose of irradiation, but were reduced at 14 and 20 weeks. LH and ACTH were the slowest to be affected, and only at the greater doses of radiation. Thus progressive multiple pituitary endocrine deficits can be induced differentially in rats by increasing doses of cranial irradiation. This model should prove useful for defining the sites and mechanisms by which cranial irradiation induces neuroendocrine dysfunction.

Animals↗
PubMed2000

Development of synthetic promoters for radiation-mediated gene therapy.

Exposure of cells to ionising radiation results in the activation of specific transcriptional control (CArG) elements within the early growth response 1 (Egr1) gene promoter, leading to increased gene expression. As part of a study investigating the potential use of these elements in radiation-controlled gene therapy vectors, we have incorporated their sequences into a synthetic gene promoter and assayed for the ability to induce expression of a downstream reporter gene following irradiation. In vector-transfected MCF-7 breast adenocarcinoma cells, the synthetic promoter was more effective than the wild-type Egr1 counterpart in up-regulating expression of the reporter gene after exposure to a single 5 Gy dose, and equally effective as the wild-type in U87-MG glioma cells. The level of gene expression achieved using the synthetic promoter was dependent on the inducing radiation dose for both U87-MG and MCF-7 cells, being maximal at 3 Gy and decreasing at 5 and 10 Gy. Furthermore, induction could be repeated by additional radiation treatments. The latter indicates that up-regulation should be additive during fractionated radiotherapy schedules. To demonstrate the potential clinical benefit of such an approach, the synthetic promoters were also shown to drive expression of the herpes simplex virus thymidine kinase gene, leading to enhanced cell killing in the presence of the prodrug ganciclovir (GCV) when compared with cells treated with radiation alone. Our results demonstrate that the synthetic promoter is responsive to low doses of ionising radiation and therefore isolated CArG elements function as radiation-mediated transcriptional enhancers outside their normal sequence context. The continued development and optimisation of such radiation-responsive synthetic promoters is expected to make a valuable contribution to the development of future radiation-responsive vectors for cancer gene therapy.

Adenocarcinoma↗
PubMed2000

A radiation-controlled molecular switch for use in gene therapy of cancer.

Ionising radiation induces the expression of a number of radiation-responsive genes and there is current interest in exploiting this to regulate the expression of exogenous therapeutic genes in gene therapy strategies for cancer. However, the radiation-responsive promoters used in these approaches are often associated with low and transient levels of therapeutic gene expression. We describe here a novel radiation-triggered molecular switching device based on promoter elements from the radiation-responsive Egr-1 gene and the cre-LoxP site-specific recombination system of the P1 bacteriophage. Using this system, a single, minimally toxic dose of radiation induced cre-mediated excision of a lox-P flanked stop cassette in a silenced expression vector and this resulted in amplified levels of CMV-promoter-driven expression of the exogenous tumour-sensitising gene, HSV-tk. This strategy could be used in combination with targeted delivery and tumour-specific promoters to elicit the tumour-targeted and prolonged expression of a variety of tumour-sensitising genes and provide an unprecedented level of control and tumour selectivity.

Antiviral Agents↗
PubMed2000

Expression of Ku70 correlates with survival in carcinoma of the cervix.

Cervical carcinoma affects around 3400 women in the UK each year and advanced disease is routinely treated with radiation. As part of a programme to establish rapid and convenient methods of predicting tumour and patient responses to radiotherapy, we have examined the relationship between the pre-treatment expression of the Ku components of the DNA damage recognition complex DNA-PK and patient survival in cervical carcinoma. Using immunohistochemistry of formalin-fixed sections of tumour biopsies, antibodies to Ku70 and Ku80 stained identical regions of tumour and there was a high degree of correlation between the mean number of cells stained positive for the two components in 77 tumours (r = 0.82, P<0.001). In 53 tumours there was a borderline significant correlation between measurements of tumour radiosensitivity (surviving fraction at 2 gray: SF2) and Ku70 expression (r = 0.26, P = 0.057) and no correlation for Ku80 (r = 0.18, P = 0.19). However, all tumours with a low number of Ku70 or Ku80 positive cells were radiosensitive. Furthermore, using log-rank analysis there was significantly higher survival in the patients whose tumours had a low Ku70 expression (P = 0.046). This difference was also reflected with Ku80, but did not reach statistical significance (P = 0.087). The study suggests that lack of Ku protein leads to radiosensitivity in some tumours and that other factors are responsible for radiosensitive tumours with high Ku expression. It is likely that the most accurate prediction of treatment outcome will lie in assessing the expression of several proteins involved in the recognition and repair of DNA damage, one of which will be Ku.

Antigens, Nuclear↗