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Bo Stenerlöw

Publications and source records attributed to Bo Stenerlöw.

14 recordsLinked to original sources
PubMed2006

Requirements regarding dose rate and exposure time for killing of tumour cells in beta particle radionuclide therapy.

PURPOSE: The purpose of this study was to identify combinations of dose rate and exposure time that have the potential to provide curative treatment with targeted radionuclide therapy applying low dose rate beta irradiation. METHODS: Five tumour cell lines, U-373MG and U-118MG gliomas, HT-29 colon carcinoma, A-431 cervical squamous carcinoma and SKBR-3 breast cancer, were used. An experimental model with 10(5) tumour cells in each sample was irradiated with low dose rate beta particles. The criterion for successful treatment was absence of recovery of cells during a follow-up period of 3 months. The initial dose rates were in the range 0.1-0.8 Gy/h, and the cells were continuously exposed for 1, 3 or 7 days. These combinations covered dose rates and doses achievable in targeted radionuclide therapy. RESULTS: Continuous irradiation with dose rates of 0.2-0.3 and 0.4-0.6 Gy/h for 7 and 3 days, respectively, could kill all cells in each tumour cell sample. These treatments gave total radiation doses of 30-40 Gy. However, when exposed for just 24 h with about 0.8 Gy/h, only the SKBR-3 cells were successfully treated; all the other cell types recovered. There were large cell type-dependent variations in the growth delay patterns for the cultures that recovered. The U-118MG cells were most resistant and the U-373MG and SKBR-3 cells most sensitive to the treatments. The HT-29 and A-431 cells were intermediate. CONCLUSION: The results serve as a guideline for the combinations of dose rate and exposure time necessary to kill tumour cells when applying low dose rate beta irradiation. The shift from recovery to "cure" fell within a narrow range of dose rate and exposure time combinations.

Apoptosis↗
PubMed2006

p53 is involved in clearance of ionizing radiation-induced RAD51 foci in a human colon cancer cell line.

We have investigated p53-related differences in cellular response to DNA damaging agents, focusing on p53s effects on RAD51 protein level and sub-cellular localization post exposure to ionizing radiation. In a human colon cancer cell line, HCT116 and its isogenic p53-/- subcell line we show here p53-independent RAD51 foci formation but interestingly the resolution of RAD51 foci showed clear p53 dependence. In p53 wt cells, but not in p53-/- cells, RAD51 protein level decreased 48 h post irradiation and fluorescence immunostaining showed resolution of RAD51 foci and relocalization of RAD51 to nucleoli at time points corresponding to the decrease in RAD51 protein level. Both cell lines rejoined DNA double strand breaks efficiently with similar kinetics and p53 status did not influence sensitivity to DNA damaging agents. We suggest that p53 has a role in RAD51 clearance post DSB repair and that nucleoli might be sites of RAD51 protein degradation.

Cell Line, Tumor↗
PubMed2006

Clusters of DNA double-strand breaks induced by different doses of nitrogen ions for various LETs: experimental measurements and theoretical analyses.

The yields and clustering of DNA double-strand breaks (DSBs) were investigated in normal human skin fibroblasts exposed to gamma rays or to a wide range of doses of nitrogen ions with various linear energy transfers (LETs). Data obtained by pulsed-field gel electrophoresis on the dose and LET dependence of DNA fragmentation were analyzed with the randomly located clusters (RLC) formalism. The formalism considers stochastic clustering of DSBs along a chromosome due to chromatin structure, particle track structure, and multitrack action. The relative biological effectiveness (RBE) for the total DSB yield did not depend strongly on LET, but particles with higher LET produced higher fractions of small DNA fragments, corresponding in the formalism to an increase in the average number of DSBs per DSB cluster. The results are consistent with the idea that DSB clustering along chromosomes is what leads to large RBEs of high-LET radiations for major biological end points. At a given dose, large fragments are less affected by the variability in LET than small fragments, suggesting that the two free ends in large fragments are often produced by two different tracks. The formalism successfully described an extra increase in small DNA fragments as dose increases and a related decrease in large fragments, mainly due to interlacing of DSB clusters produced along a chromosome by different tracks, since interlacing cuts larger DNA fragments into smaller ones.

Cell Line↗
PubMed2005

Cellular internalization of cytolethal distending toxin: a new end to a known pathway.

The cytolethal distending toxins (CDTs) are unique in their ability to induce DNA damage, activate checkpoint responses and cause cell cycle arrest or apoptosis in intoxicated cells. However, little is known about their cellular internalization pathway. We demonstrate that binding of the Haemophilus ducreyi CDT (HdCDT) on the plasma membrane of sensitive cells was abolished by cholesterol extraction with methyl-beta-cyclodextrin. The toxin was internalized via the Golgi complex, and retrogradely transported to the endoplasmic reticulum (ER), as assessed by N-linked glycosylation. Further translocation from the ER did not require the ER-associated degradation (ERAD) pathway, and was Derlin-1 independent. The genotoxic activity of HdCDT was dependent on its internalization and its DNase activity, as induction of DNA double-stranded breaks was prevented in Brefeldin A-treated cells and in cells exposed to a catalytically inactive toxin. Our data contribute to a better understanding of the CDT mode of action and highlight two important aspects of the biology of this bacterial toxin family: (i) HdCDT translocation from the ER to the nucleus does not involve the classical pathways followed by other retrogradely transported toxins and (ii) toxin internalization is crucial for execution of its genotoxic activity.

Animals↗
PubMed2005

DNA-incorporated 125I induces more than one double-strand break per decay in mammalian cells.

The Auger-electron emitter 125I releases cascades of 20 electrons per decay that deposit a great amount of local energy, and for DNA-incorporated 125I, approximately one DNA double-strand break (DSB) is produced close to the decay site. To investigate the potential of 125I to induce additional DSBs within adjacent chromatin structures in mammalian cells, we applied DNA fragment-size analysis based on pulsed-field gel electrophoresis (PFGE) of hamster V79-379A cells exposed to DNA-incorporated 125IdU. After accumulation of decays at -70 degrees C in the presence of 10% DMSO, there was a non-random distribution of DNA fragments with an excess of fragments <0.5 Mbp and the measured yield was 1.6 DSBs/decay. However, since these experiments were performed under high scavenging conditions (DMSO) that reduce indirect effects, the yield in cells exposed to 125IdU under physiological conditions would most likely be even higher. In contrast, using a conventional low-resolution assay without measurement of smaller DNA fragments, the yield was close to one DSB/decay. We conclude that a large fraction of the DSBs induced by DNA-incorporated 125I are nonrandomly distributed and that significantly more than one DSB/decay is induced in an intact cell. Thus, in addition to DSBs produced close to the decay site, DSBs may also be induced within neighboring chromatin fibers, releasing smaller DNA fragments that are not detected by conventional DSB assays.

Animals↗
PubMed2005

An aminoacridine derivative for radionuclide therapy: DNA binding properties studied in a novel cell-free in vitro assay.

Radiolabelled DNA-binding compounds can be used to increase the efficiency of radionuclide cancer therapy of disseminated disease. In this work, the aminoacridine compound N-[3-(acridine-9-ylamino)-propyl]-3-iodobenzamide (A3) labelled with the Auger-emitting nuclide 125I using Chloramine-T was studied. Optimal labelling conditions of 125I-A3 were investigated and the interaction with DNA was studied using a novel cell-free in vitro assay with naked human genomic DNA in agarose plugs. This novel assay showed to be simple and reliable. The results verify that 125I-A3 specifically binds DNA with low dissociation and is potent in causing double-strand breaks, yielding 1.0-1.4 breaks per decay. In conclusion, 125I-A3 is a most suitable DNA-binding compound for future therapeutic studies of Auger-electron emitters like 125I.

Acridines↗
PubMed2004

Chromatin organization contributes to non-randomly distributed double-strand breaks after exposure to high-LET radiation.

The influence of higher-order chromatin structure on the non-random distribution of DNA double-strand breaks induced by high-LET radiation was investigated. Five different chromatin structures (intact cells, condensed and decondensed chromatin, nucleoids and naked genomic DNA) from GM5758 cells or K562 cells were irradiated with (137)Cs gamma-ray photons and 125 keV/microm nitrogen ions (16-25 MeV/nucleon). DNA was purified with a modified lysis procedure to avoid release of heat-labile sites, and fragment size distributions and double-strand break yields were analyzed by different pulsed-field gel electrophoresis protocols. Whereas double-strand breaks in photon-irradiated cells were randomly distributed, irradiation of intact K562 cells with high-LET nitrogen ions produced an excess of non-randomly distributed DNA fragments 10 kb-1 Mbp in size. Complete removal of proteins eliminated this non-random component. There was a gradual increase in the yield of double-strand breaks for each chromatin decondensation step, and compared to intact cells, the yields for naked DNA (in buffer without scavengers) increased 83 and 25 times after photon and nitrogen-ion irradiation, respectively. The corresponding relative biological effectiveness decreased from 1.6-1.8 for intact cells to 0.49 for the naked DNA. We conclude that the organization of DNA into chromatin fiber and higher-order structures is responsible for the majority of non-randomly distributed double-strand breaks induced by high-LET radiation. However, our data suggest a complex interaction between track structure and chromatin organization over several levels.

Chromatin↗
PubMed2004

Focus formation of DNA repair proteins in normal and repair-deficient cells irradiated with high-LET ions.

To investigate the repair of clustered lesions within the DNA/chromatin, the focus formation and persistence of foci of the phosphorylated histone protein H2AX and the repair protein MRE11 were studied in normal cells and in cells lacking DNA-PKcs (M059J) or ATM (GM2052D) after irradiation with high-LET nitrogen ions or low-LET photons. There was a rapid formation of MRE11 and gamma-H2AX foci, and 0.5 h after high-LET irradiation, the number of foci in normal cells correlated well with the number of particle hits per cell nucleus. After 8 h of repair, there were significantly more gamma-H2AX foci than MRE11 foci remaining in the normal cells, independent of radiation quality. The difficulty in repairing clustered breaks was detected as slower rejoining of DSBs (measured by DNA fragmentation analysis), as quantification of the amount of gamma-H2AX over time, and as a larger fraction of repair foci remaining after 24 h in cells irradiated with high- LET ions. These data indicate that clustered lesions are repaired by a pathway involving the same proteins that repair sparsely distributed breaks. Further, for both low- and high- LET radiation, no reduction of the initial number of gamma-H2AX and MRE11 foci was detected in M059J cells up to 21 h after irradiation, which was in accordance with a complete absence of DSB rejoining in these cells. In the GM2052D cells there was also a higher level of foci remaining after 21 h; however, this was not accompanied by unrejoined DSBs, indicating that these foci not only represent DSBs but also may be a sign of persistent problems even when breaks are rejoined.

Ataxia Telangiectasia Mutated Proteins↗
PubMed2003

The Haemophilus ducreyi cytolethal distending toxin induces DNA double-strand breaks and promotes ATM-dependent activation of RhoA.

Among bacterial protein toxins, the cytolethal distending toxins (CDTs) are unique in their ability to activate the DNA damage checkpoint responses, causing cell cycle arrest or apoptosis in intoxicated cells. We provide direct evidence that natural intoxication of cells with the Haemophilus ducreyi CDT (HdCDT) holotoxin induces DNA double-strand breaks similarly to ionizing radiation. Upon DNA damage, epithelial cells and fibroblasts promote the formation of actin stress fibres via activation of the small GTPase RhoA. This phenomenon is not toxin specific, but is part of the ATM-induced cellular responses to genotoxic stresses, including ionizing radiation. Activation of RhoA is associated with prolonged cell survival, as HdCDT-treated epithelial cells expressing a dominant-negative form of RhoA detach and consequently die faster than cells expressing a functional RhoA. Our data highlight several novel aspects of CDT biology: (i) we show that a member of the CDT family causes DNA double-strand breaks in naturally intoxicated cells, acting as a true genotoxic agent; and (ii) we disclose the existence of a novel signalling pathway for intracellularly triggered activation of the RhoA GTPase via the ATM kinase in response to DNA damage, possibly required to prolong cell survival.

Actins↗
PubMed2003

Biological response to radiation therapy.

In an investigation by the Swedish Cancer Society, the present status, critical issues and future aspects and potentials were described by an expert group for each of nine major areas of radiation therapy research. This article deals with biological response to radiation. Separate sections deal with molecular responses to radiation, the stem cell and clonogenic cell concepts and the importance of cell proliferation, cell and tissue responses to doses above and below 1 Gy, respectively, the potential role of intercellular signalling pathways, the so-called bystander effect and radiation biology-based therapy planning and treatment optimization.

Bystander Effect↗
PubMed2003

Measurement of prompt DNA double-strand breaks in mammalian cells without including heat-labile sites: results for cells deficient in nonhomologous end joining.

Ionizing radiation induces prompt single-strand breaks and double-strand breaks in DNA. In addition, labile sites are induced that can be converted to breaks by heat or mild alkali. When such labile lesions are present within multiply damaged sites, additional double-strand breaks can form. Current protocols for measurement of DNA double-strand breaks involve a lysis step at an elevated temperature, and consequently breaks from heat-labile sites will be generated during lysis and will be included in the measurement. However, such sites may not develop into breaks within the cell and therefore may not need DNA double-strand break repair processes for elimination. We present here a new lysis and pulsed-field gel electrophoresis protocol that is carried out entirely at 0-4 degrees C and thus avoids inclusion of heat-labile sites in the measurement. The new recommended lysis procedure involves two steps: The first step includes proteinase K, which has sufficient activity at 0 degrees C to support lysis, and the second step includes a high-salt buffer to further free the DNA from proteins and other cellular structures. Using various tests, we conclude that lysis is sufficient with this procedure to allow accurate determination of double-strand breaks by pulsed-field gel electrophoresis. Using the new protocol, it was found that heat-labile sites account for 30% of the initial number of double-strand breaks measured by conventional protocols after exposure to low-LET radiation. In addition, we show that heat-labile sites that can be converted to double-strand breaks are repaired with fast kinetics and are almost completely eliminated after 1 h at 37 degrees C. A study of cells deficient in nonhomologous end joining reveals that the residual fast repair response typically seen in such cells is solely due to repair at heat-labile sites and is not due to repair of prompt DSBs.

Agar↗
PubMed2002

Rejoining of double-stranded DNA-fragments studied in different size-intervals.

PURPOSE: To measure rejoining of radiation-induced doublestranded DNA-fragments of different sizes and to evaluate the effects of size-resolution in the analysis of rejoining. MATERIAL AND METHODS: Normal human fibroblasts (GM5758) were irradiated with photons or accelerated nitrogen ions (linear energy transfer, LET = 125 keV microm(-1)) and incubated for repair for 0-22 h. Double-stranded DNA-fragments from the irradiated cells were separated by pulsed-field gel electrophoresis in the range approximately 5 kbp to 5.7 Mbp. RESULTS: For cells irradiated with high LET nitrogen ions, there was an increase in the fast half-time from approximately 5 min for fragments < 400 kbp to 10 min when all fragments < 5.7 Mbp were measured. Further, the fraction of fragments rejoined by the slow-rejoining phase increased significantly for increased threshold sizes. The fraction of unrejoined fragments after 22 h and the half-time for the slow-rejoining phase remained constant for all threshold sizes. For cells irradiated with lower doses of low LET radiation the rejoining was shifted towards a slower kinetics when fragments up to 10 Mbp were excluded in the analysis. CONCLUSION: DNA exclusion-size and resolution may affect the estimates of DNA double-strand break rejoining. Using a low-resolution technique that does not detect small fragments will result in an underestimation, or even disappearance of the fast-rejoining phase. This is due to substantial rejoining of fragments taking place before the fragments are of sufficient size to be monitored.

Cell Line↗
PubMed2002

Swedish Cancer Society radiation therapy research investigation.

In an investigation by the Swedish Cancer Society, the present status, critical issues and future aspects and prospects were described by an expert group for each of nine major areas of radiation research. A summary of the investigation is presented in this report. A more extensive summary (in Swedish) can be found at www.Cancerfonden.se. It is concluded that radiation therapy plays an increasingly important role in curative and palliative tumour treatment and presents a considerable challenge to research. Several suggestions are made that could improve the possibilities for high-quality radiation therapy research in Sweden.

Humans↗