Hypersensitivity of BRCA1 heterozygote lymphoblastoid cells to gamma radiation and PARP inhibitors

This article is made available through the Brunel Open Access Publishing Fund. Copyright @ 2013 Bourton EC, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.PARP inhibitors can be used to induce synthetic lethality in cells with bi-allelic BRCA1 and BRCA2 mutations. However the effect of PARP inhibitors in combination with radiation on cells with mono-allelic mutations of BRCA1 and BRCA2 is unknown. We have examined the cell survival response of lymphoblastoid cells derived from normal individuals and those derived from carriers of BRCA1 and BRCA2 mutations, following exposure to ionising radiation and the PARP inhibitor Olaparib. Two lymphoblastoid cell lines from normal individuals and three with mono-allelic mutations in BRCA1 and BRCA2 were exposed to increasing doses of gamma radiation either alone or in combination with 5 μM Olaparib. Cell survival was measured using the MTT assay. Exposure to increasing doses of gamma radiation caused a reduction in cell survival of all cell types. The combined exposure to gamma radiation and 5 μM Olaparib did not enhance cell kill in normal or BRCA2 heterozygote lymphoblastoid cells but significantly enhanced cell kill in cells derived from BRCA1 carriers (P = 0.02). The treatment of cancer patients carrying mutations in the BRCA1 gene with radiotherapy and the PARP inhibitor Olaparib may significantly enhance radiation induced normal tissue toxicity in these patients.Vidal Sassoon Foundation of America and “The Balls to Cancer” Charity, Coventry, U

Prolonged expression of the γ-H2AX DNA repair biomarker correlates with excess acute and chronic toxicity from radiotherapy treatment

The normal tissue tolerance levels to fractionated radiotherapy have been appreciated by a century of careful clinical observations and radiobiological studies in animals. During clinical fractionated radiotherapy, these normal tissue tolerance levels are respected, and severe sequelae of radiotherapy are avoided in the majority of patients. Notwithstanding, a minority of patients experience unexpectedly severe normal tissue reactions. The ability to predict which patients might form this minority would be important. We have conducted a study to develop a rapid and reliable diagnostic test to predict excessive normal tissue toxicity (NTT) in radiotherapy patients. A flow cytometric immunocytochemical assay was used to measure DNA damage in peripheral blood lymphocytes (PBL) from cancer patients exposed to 2-Gy gamma radiation. DNA damage and repair was measured by induction of cellular γ-H2AX in unirradiated and exposed cells at specific time points following exposure. In 12 cancer patients that experienced severe atypical NTT following radiotherapy, there was a failure to repair DNA double-strand breaks (DSB) as measured by γ-H2AX induction and persistence. In ten cancer patients that experienced little or no NTT and in seven normal (noncancer controls), efficient repair of DNA DSB was observed in the γ-H2AX assay. We conclude that a flow cytometric assay based on γ-H2AX induction in PBL of radiotherapy patients may represent a robust, rapid and reliable biomarker to predict NTT during radiotherapy. Further research is required with a larger patient cohort to validate this important study

The PARP-1 inhibitor Olaparib causes retention of γ-H2AX foci in BRCA1 heterozygote cells following exposure to gamma radiation

This article is made available through the Brunel Open Access Publishing Fund. Copyright © 2013 Emma C. Bourton et al. This is an open access article distributed under the Creative Commons Attribution Li-cense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.A novel treatment for cancer patients with homozygous deletions of BRCA1 and BRCA2 is to use drugs that inhibit the enzyme poly(ADP-ribose) polymerase (PARP). Specific inhibition of PARP-1 can induce synthetic lethality in irradi- ated cancer cells while theoretically leaving normal tissue unaffected. We recently demonstrated in a cell survival assay that lymphoblastoid cells with mono-allelic mutations of BRCA1 were hypersensitive to gamma radiation in the pres- ence of the PARP-1 inhibitor Olaparib compared to normal cells and mono-allelic BRCA2 cells. To determine if the enhanced radiation sensitivity was due to a persistence of DNA strand breaks, we performed γ-H2AX foci analysis in cells derived from two normal individuals, three heterozygous BRCA1 and three heterozygous BRCA2 cell lines. Cells were exposed to 2 Gy gamma radiation in the presence or absence of 5 μM Olaparib. Using immunofluorescence and imaging flow cytometry, foci were measured in untreated cells and at 0.5, 3, 5 and 24 hours post-irradiation. In all lymphoblastoid cells treated with 2 Gy gamma radiation, there was a predictable induction of DNA strand breaks, with a modest but significant retention of foci over 24 hours in irradiated cells treated with Olaparib (ANOVA P < 0.05). However, in mono-allelic BRCA1 cells, there was a failure to fully repair DNA double-strand breaks (DSB) in the pres- ence of Olaparib, evidenced by a significant retention of foci at 24 hours’ post irradiation (t-Test P < 0.05). These data show that the cellular hypersensitivity of mono-allelic BRCA1 lymphoblastoid cells to gamma radiation in the presence of the Olaparib is due to the retention of DNA DSB. These data may indicate that patients with inherited mutations in the BRCA1 gene treated with radiotherapy and PARP-1 inhibitors may experience elevated radiation-associated normal tissue toxicity.Vidal Sassoon Foundation of America

Multispectral imaging flow cytometry reveals distinct frequencies of γ-H2AX foci induction in DNA double strand break repair defective human cell lines

Copyright @ 2012 International Society for Advancement of Cytometry. The article can be accessed from the links below.This article has been made available through the Brunel Open Access Publishing Fund.The measurement of γ-H2AX foci induction in cells provides a sensitive and reliable method for the quantitation of DNA damage responses in a variety of cell types. Accurate and rapid methods to conduct such observations are desirable. In this study we have employed the novel technique of multispectral imaging flow cytometry to compare the induction and repair of γ-H2AX foci in three human cell types with different capacities for the repair of DNA double strand breaks (DSB). A repair normal fibroblast cell line MRC5-SV1, a DSB repair defective ataxia telangiectasia (AT5BIVA) cell line, and a DNA-PKcs deficient cell line XP14BRneo17 were exposed to 2 Gy gamma radiation from a 60Cobalt source. Thirty minutes following exposure we observed a dramatic induction of foci in the nuclei of these cells. After 24 hrs there was a predictable reduction on the number of foci in the MRC5-SV1 cells, consistent with the repair of DNA DSB. In the AT5BIVA cells, persistence of the foci over a 24 hour period was due to the failure in the repair of DNA DSB. However, in the DNA-PKcs defective cells (XP14BRneo17) we observed an intermediate retention of foci in the nuclei indicative of partial repair of DNA DSB. In summary, the application of imaging flow cytometry has permitted an evaluation of foci in a large number of cells (20,000) for each cell line at each time point. This provides a novel method to determine differences in repair kinetics between different cell types. We propose that imaging flow cytometry provides an alternative platform for accurate automated high through-put analysis of foci induction in a variety of cell types.This article is made available through the Brunel Open Access Publishing Fund

Radiosensitivity of human breast cancer cell lines expressing the breast tumor kinase (Brk)

The breast tumor kinase (Brk) is over-expressed in 80% of all breast cancers and we sought to determine the influence of this oncogene on radiation sensitivity in breast cancer cell lines. Since radiotherapy is a routinely used method of treatment for early and intermediate stage breast cancer, the alteration of clinical radiosensitivity in breast cancer by an oncogene over-expression would have important implications in radiotherapy management. To address this question, we conducted an in vitro study of radiation sensitivity in two breast cancer cell lines, MDA-MB-157 and MDA-MB-468 transfected with cDNA constructs to over-express the following genes: Brk wild type (WT); Brk with an inactivating mutation in the kinase domain (KM) and vector only. Gamma H2AX foci assays by imaging flow cytometry were used to measure DNA double strand break (DSB) repair after radiation exposure. Total ataxia telangiectasia (ATM) and activated phospho794-ATM protein was measured by imaging flow cytometry. In all cell lines tested there was a proportionate decline in cell survival following gamma radiation exposure. Radiation sensitivity of the cell lines in clonogenic assays and repair of DNA double strand breaks were similar and independent of Brk expression status. We conclude that over-expression of the Brk proto-oncogene in breast cancer cell lines does not appear to influence radiation sensitivity or affect DNA DSB repair.This work was supported by a grant from The Bart’s Charity (Grant Number: 419/2071), 12 Cock Lane, London EC1A 9BU

A novel splice variant of the DNA-PKcs gene is associated with clinical and cellular radiosensitvity in a xeroderma pigmentosum patient

This article has been made available through the Brunel Open Access Publishing Fund.Background: Radiotherapy-induced DNA double strand breaks (DSB) are critical cytotoxic lesions. Inherited defects in DSB DNA repair pathways lead to hypersensitivity to ionising radiation, immunodeficiency and increased cancer incidence. A patient with xeroderma pigmentosum complementation group C, with a scalp angiosarcoma exhibited dramatic clinical radiosensitivity following radiotherapy, resulting in death. A fibroblast cell line from non-affected skin (XP14BRneo17) was hypersensitive to ionising radiation and defective in DNA double strand break repair. Aim: To determine the genetic defect causing cellular radiation hypersensitivity in XP14BRneo17 cells. Methods: Functional genetic complementation whereby copies of human chromosomes containing genes involved in DNA DSB repair (chromosomes 2, 5, 8 10, 13 and 22) were individually transferred to XP14BRneo17 cells in an attempt to correct the radiation hypersensitivity. Clonogenic survival assays and γ-H2AX immunofluorescence were conducted to measure radiation sensitivity and repair of DNA DSBs. DNA sequencing of defective DNA repair genes was performed. Results: Transfer of chromosome 8 (location of DNA-PKcs gene), and transfection of a mammalian expression construct containing the DNA-PKcs cDNA restored normal ionising radiation sensitivity and repair of DNA DSBs in XP14BRneo17 cells. DNA sequencing of the DNA-PKcs coding region revealed a 249 bp deletion (between base pairs 3656-3904) encompassing exon 31 of the gene. Conclusion: We provide evidence of a novel splice variant of the DNA-PKcs gene associated with radiosensitivity in a xeroderma pigmentosum patient and report the first double mutant in distinct DNA repair pathways being consistent with viability.Brunel Open Access Publishing Fun

Primary intraocular lymphoma.

Primary intraocular lymphoma (PIOL) is an ocular malignancy that is a subset of primary central system lymphoma (PCNSL). Approximately one-third of PIOL patients will have concurrent PCNSL at presentation, and 42-92% will develop PCNSL within a mean of 8-29 months. Although rare, the incidence has been rising in both immunocompromised and immunocompetent populations. The majority of PIOL is diffuse large B-cell lymphoma, though rare T-cell variants are described. Recently, PIOL has been classified by main site of involvement in the eye, with vitreoretinal lymphoma as the most common type of ocular lymphoma related to PCNSL. Diagnosis remains challenging for ophthalmologists and pathologists. PIOL can masquerade as noninfectious or infectious uveitis, white dot syndromes, or occasionally as other neoplasms such as metastatic cancers. Laboratory diagnosis by cytology has been much aided by the use of immunocytochemistry, flow cytometry, biochemical finding of interleukin changes (IL10:IL6 ratio > 1), and cellular microdissection with polymerase chain reaction amplification for clonality. Use of several tests improves the diagnostic yield. Approaches to treatment have centered on systemic methotrexate-based chemotherapy, often with cytarabine (Ara-C) and radiotherapy. Use of intravitreal chemotherapy with methotrexate (0.4 mg/0.1 mL) is promising in controlling ocular disease, and intravitreal rituximab (anti-CD20 monoclonal antibody) has also been tried. Despite these advances, prognosis remains poor

Outcomes of intravitreal methotrexate to salvage eyes with relapsed primary intraocular lymphoma

PURPOSE: To report the outcomes of intravitreal methotrexate (MTX) injections to rescue eyes with relapsed primary intraocular lymphoma (PIOL). METHODS: Retrospective case series of patients with ocular relapse of PIOL who had initially received systemic chemotherapy (all five cases) and external beam radiotherapy (EBRT) to brain and orbits (two cases). Injections of MTX (400 µg/0.1 mL) were given one time per week for 1 month, every other week for 4 months, followed by a maintenance phase of one injection one time per month for 8 months (total of 20 injections in a year). RESULTS: From April 2008 to February 2016, there were nine eyes of five patients (three men; average age at first presentation 62 years) treated with our rescue protocol of intravitreal MTX injections. Ocular relapse occurred at a mean interval of 15 months (range 5-34 months) after the completion of initial systemic treatment. At mean follow-up of 31 months (range 5-104 months), tumour control was achieved in eight out of nine eyes (89%); one eye failed, with persistent retinal infiltrates despite increasing the frequency of injections, resulting in severe keratopathy. The only other complication occurred in one eye, developing cystoid macular oedema from MTX injections that resolved with topical anti-inflammatory medications and reduced frequency of MTX. There were no cases of reduced vision or ocular relapse, but two patients died (one of central nervous system lymphoma). CONCLUSIONS: Intravitreal MTX was a safe and effective treatment modality for relapsed PIOL after systemic chemotherapy and radiotherapy, achieving local tumour control in 89%, and hence represents an optimal choice. However, given the rare nature of PIOL, larger collaborative studies with longer follow-up are needed to corroborate this

Adjuvant External Beam Radiotherapy Following Enucleation of Eyes With Extraocular Extension From Uveal Melanoma

PURPOSE: To report local disease control and all-cause mortality in patients with extraocular extension (EOE) of uveal melanoma undergoing enucleation followed by observation or external beam radiotherapy (EBRT). METHODS: Charts of patients enucleated between January 1, 1997 and December 31, 2019, with histopathological evidence of EOE of uveal melanoma were reviewed. RESULTS: The cohort comprised 51 patients with a mean age of 67 ± 15 years, 22 (43%) of whom underwent adjuvant postenucleation EBRT. Risk factors for metastasis included presence of epithelioid cells (29/45; 88%), closed loops (20/43; 47%), monosomy 3 (16/25; 64%), and gain of 8q (20/22; 91%). Patients undergoing EBRT had more extensive EOE (median: 5.1 mm vs. 2.6 mm, p = 0.008) and surgical excision was less likely to be histologically complete (2/20; 10% vs. 14/25; 56%, p = 0.002). Local side effects following EBRT were seen in 64% (14/22). At latest follow up, 59% of patients (30/51) were alive, with a median follow up of 1.8 years (interquartile range: 2.9; range: 0.1-6.5]. By Kaplan-Meier survival analysis, the 5- and 10-year overall survival rates were 56% and 12%, respectively. There was no difference in all-cause mortality between those receiving adjuvant EBRT and those who were observed (log rank, p = 0.273). No cases of orbital recurrence were documented. CONCLUSIONS: Orbital EBRT causes significant morbidity. Cases with relatively small EOE undergoing enucleation can be safely observed, without adjuvant EBRT. Multicenter studies are required to better assess the role of EBRT when EOE is more extensive