Radiosensitivity Of Cell Lines Research Articles

Radiation Resistance of Double Knockout (DKO) Smad3-/- Fancd2-/- (129/Sv) Mouse Bone Marrow Stromal Cell Lines

Introduction: Bone marrow progenitor cells from Fanconi Anemia (FA) patients have a hyperactive TGF-β signaling pathway which may explain hematopoietic stem cell depletion leading to bone marrow failure (Zhang, et al, Cell Stem Cell, 18:668-681, 2016). To determine whether blockade of TGF-B signaling by knockout of Smad3 normalized hematopoiesis in Fancd2-/- mice, we bred two double knockout mouse strains. The first (DKO#1) was derived by crossing C57BL/6 Fancd2 +/- mice with 129/Sv Smad3 +/- mice. The second (DKO#2) was derived by mating 129/Sv Fancd2 +/- mice with the same 129/Sv Smad3 +/- mice.Materials and Methods: Long term bone marrow cultures (LTBMCs) were established from DKO#1, DKO#2, parental mouse strains and F1 (129/Sv X C57Bl/6) control mice for DKO#1, 129/Sv Smad3 -/-, and C57BL/6 Smad3 -/- mice . The cultures were scored for weekly numbers of cobblestone islands as an indicator of stem cells in the adherent layer, weekly production of nonadherent cells, and cells producing Day 7 and Day 14 CFU-GEMM .Bone marrow stromal cell lines were derived from the adherent layer of LTBMCs and radiosensitivity measured in clonogenic radiation survival curves. Cells were irradiated to doses of 0 to 8 Gy, plated in 4 well linbro plates, incubated for 7 days at 37oC, stained with crystal violet and colonies of greater than 50 cells counted. Western analysis of the cell lines quantitated expression levels of proteins involved in the TGF-β signaling pathway, and DNA double strand break repair by homologous recombination and nonhomologous end-joining.Results: Both DKO1 and DKO2 LTBMCs showed decreased duration and magnitude of hematopoiesis, thus being similar to that observed with both C57BL/6 Fancd2-/- and 129/Sv Fancd2-/- mouse marrow cultures. Both were significantly lower than that for control mouse or Smad3-/- (129/Sv) marrow cultures. As expected, radiation survival curves showed that both C57Bl/6 Fancd2-/- and 129/Sv Fancd2-/- marrow stromal cell lines were radiosensitive compared to control cell lines including: F1 control, C57BL/6 control, and 129/Sv control (Berhane, et al, Rad Res. 181:76-89, 2014, Berhane et.al, Rad Res 182:35-49, 2014). In contrast marrow stromal cell lines from Smad3-/- (129/Sv) marrow cultures were radioresistant (Epperly, et al, Rad Res 165:671-677, 2006). Fresh marrow CFU-GEMM from both DKO#1 and DKO#2 mice showed resistance to abrogation of colony formation by increasing concentrations of TGF-B, (similar to the 129/Sv Smad3-/- cell line). In contrast, cell lines from all controls and both Fancd2-/- mice showed clear TGF-B mediated inhibition of hemopoietic colony formation. In striking contrast to the above similarities between DKO#1 and DKO#2 mice, marrow stromal cell lines from DKO#1 were radiosensitive (like theirFancd2-/- parent) while those from DKO#2 were radioresistant (like their Smad3-/- parent). Thus, DKO#1 retained the C57Bl/6 Fancd2-/- genotype cell line radiosensitivity: Do of 1.41 ± 0.03 Gy and 1.45 ± 0.05 Gy respectively, and were more radiosensitive than the control F1 bone marrow stromal cell line (p = 0.0230 and 0.0418, respectively) and DKO#2 retained the 129/Sv Smad3-/- cell line genotype radioresistance (Do = 2.15 ± 0.13 Gy) compared to control 129/Sv stromal cells (Do = 1.86 ± 0.04, p = 0.0054). Western analysis revealed that p21 was elevated in DKO#2 but not DKO#1 marrow stromal cell lines.Conclusions: While marrow from both DKO#1 and DKO#2 mice showed resistance to TGF-B signaling consistent with their smad3-/- genotype, only DKO#1 stromal cells retained the radiosensitivity of their Fancd2-/- genotype. Reduced p21 in irradiated DKO#1 marrow stromal cells may have allowed procession through G to S phase causing reduced time for DNA repair and radiosensitivity. The irradiated DKO#2 cells may have been blocked by p21 from passing through the G1 checkpoint and may have allowed DNA strand break repair and radioresistance. These DKO mice and derived cell lines should be valuable for analysis of the interaction of TGF-B signaling and FA pathways.Supported by NIAID/NIH U19-AI068021 DisclosuresNo relevant conflicts of interest to declare.

Maternal Embryonic Leucine Zipper Kinase (MELK) as a Novel Mediator and Biomarker of Radioresistance in Human Breast Cancer.

While effective targeted therapies exist for estrogen receptor-positive and HER2-positive breast cancer, no such effective therapies exist for triple-negative breast cancer (TNBC); thus, it is clear that additional targets for radiosensitization and treatment are critically needed. Expression microarrays, qRT-PCR, and Western blotting were used to assess MELK RNA and protein expression levels. Clonogenic survival assays were used to quantitate the radiosensitivity of cell lines at baseline and after MELK inhibition. The effect of MELK knockdown on DNA damage repair kinetics was determined using γH2AX staining. The in vivo effect of MELK knockdown on radiosensitivity was performed using mouse xenograft models. Kaplan-Meier analysis was used to estimate local control and survival information, and a Cox proportional hazards model was constructed to identify potential factors impacting local recurrence-free survival. MELK expression is significantly elevated in breast cancer tissues compared with normal tissue as well as in TNBC compared with non-TNBC. MELK RNA and protein expression is significantly correlated with radioresistance in breast cancer cell lines. Inhibition of MELK (genetically and pharmacologically) induces radiation sensitivity in vitro and significantly delayed tumor growth in vivo in multiple models. Kaplan-Meier survival and multivariable analyses identify increasing MELK expression as being the strongest predictor of radioresistance and increased local recurrence in multiple independent datasets. Here, we identify MELK as a potential biomarker of radioresistance and target for radiosensitization in TNBC. Our results support the rationale for developing clinical strategies to inhibit MELK as a novel target in TNBC. Clin Cancer Res; 22(23); 5864-75. ©2016 AACR.

Identification of biomarker microRNAs for predicting the response of colorectal cancer to neoadjuvant chemoradiotherapy based on microRNA regulatory network.

Preoperative radiotherapy or chemoradiotherapy has become a standard procedure for treatment of patients with locally advanced colorectal cancer (CRC). However, patients’ responses to treatment are different and personalized. MicroRNAs (miRNAs) are promising biomarkers for predicting personalized responses. In this study, we collected 30 publicly reported miRNAs associated with chemoradiotherapy of CRC. We extracted 46 differentially expressed miRNAs from samples of responders and non-responders to preoperative radiotherapy from the Gene Expression Omnibus dataset (Student's t test, p-value < 0.05 and |fold-change| > 2). We performed a systematic and integrative bioinformatics analysis to identify biomarker miRNAs for prediction of CRC responses to chemoradiotherapy. Using the bioinformatics model, miR-198, miR-765, miR-671-5p, miR-630, miR-371-5p, miR-575, miR-202, miR-483-5p and miR-513a-5p were screened as putative biomarkers for treatment response. Literature validation and functional enrichment analysis were exploited to confirm the reliability of the predicted miRNAs. Quantitative polymerase chain reaction showed that seven of the candidates were significantly differentially expressed between radiosensitive and insensitive CRC cell lines. The unique target genes of miR-198 and miR-765 were altered significantly upon transfection of specific miRNA mimics in the radiosensitive cell line. These results demonstrated the predictive power of our model and suggested that miR-198, miR-765, miR-630, miR-371-5p, miR-575, miR-202 and miR-513a-5p could be used for predicting the response of CRC to preoperative chemoradiotherapy.

Ku70, Ku80, and sClusterin: A Cluster of Predicting Factors for Response to Neoadjuvant Chemoradiation Therapy in Patients With Locally Advanced Rectal Cancer

The identification of predictive biomarkers for neoadjuvant chemoradiation therapy (CRT) is a current clinical need. The heterodimer Ku70/80 plays a critical role in DNA repair and cell death induction after damage. The aberrant expression and localization of these proteins fail to control DNA repair and apoptosis. sClusterin is the Ku70 partner that sterically inhibits Bax-dependent cell death after damage in some pathologic conditions. This study sought to evaluate the molecular relevance of Ku70-Ku80-Clu as a molecular cluster predicting the response to neoadjuvant CRT in patients with locally advanced rectal cancer (LARC). Patients enrolled in this study underwent preoperative CRT followed by surgical excision. A retrospective study based on individual response, evaluated by computed tomography and diffusion-weighted magnetic resonance imaging, identified responder (56%) and no-responder patients (44%). Ku70/80 and Clu expression were observed in biopsy specimens obtained before and after treatment with neoadjuvant CRT from the same LARC patients. Invitro studies before and after irradiation were also performed on radioresistant (SW480) and radiosensitive (SW620) colorectal cancer cell lines, mimicking sensitive or resistant tumor behavior. We found a conventional nuclear localization of Ku70/80 in pretherapeutic tumor biopsies of responder patients, in agreement with their role in DNA repair and regulating apoptosis. By contrast, in the no-responder population we observed an unconventional overexpression of Ku70 in the cytoplasm (P<.001). In this context we also overexpression of sClu in the cytoplasm, which accorded with its role in stabilizing of Bax-Ku70 complex, inhibiting Bax-dependent apoptosis. Strikingly, Ku80 in these tumor tissues was lost (P<.005). Invitro testing of colon cancer cells finally confirmed the results observed in tumor biopsy specimens, proving that Ku70/80-Clu deregulation is extensively involved in the resistance mechanism. These results strongly suggest a potential role of these proteins as a new prognostic tool to predict the response to chemoradiation in LARC.

Relative biological effectiveness in canine osteosarcoma cells irradiated with accelerated charged particles.

Heavy ions, characterized by high linear energy transfer (LET) radiation, have advantages compared with low LET protons and photons in their biological effects. The application of heavy ions within veterinary clinics requires additional background information to determine heavy ion efficacy. In the present study, comparison of the cell-killing effects of photons, protons and heavy ions was investigated in canine osteosarcoma (OSA) cells in vitro. A total of four canine OSA cell lines with various radiosensitivities were irradiated with 137Cs gamma-rays, monoenergetic proton beams, 50 keV/µm carbon ion spread out Bragg peak beams and 200 keV/µm iron ion monoenergetic beams. Clonogenic survival was examined using colony-forming as says, and relative biological effectiveness (RBE) values were calculated relative to gamma-rays using the D10 value, which is determined as the dose (Gy) resulting in 10% survival. For proton irradiation, the RBE values for all four cell lines were 1.0-1.1. For all four cell lines, exposure to carbon ions yielded a decreased cell survival compared with gamma-rays, with the RBE values ranging from 1.56-2.10. Iron ions yielded the lowest cell survival among tested radiation types, with RBE values ranging from 3.51-3.69 observed in the three radioresistant cell lines. The radiosensitive cell line investigated demonstrated similar cell survival for carbon and iron ion irradiation. The results of the present study suggest that heavy ions are more effective for killing radioresistant canine OSA cells when compared with gamma-rays and protons. This markedly increased efficiency of cell killing is an attractive reason for utilizing heavy ions for radioresistant canine OSA.

Intrinsic Radiosensitivity and Cellular Characterization of 27 Canine Cancer Cell Lines.

Canine cancer cell lines have progressively been developed, but are still underused resources for radiation biology research. Measurement of the cellular intrinsic radiosensitivity is important because understanding the difference may provide a framework for further elucidating profiles for prediction of radiation therapy response. Our studies have focused on characterizing diverse canine cancer cell lines in vitro and understanding parameters that might contribute to intrinsic radiosensitivity. First, intrinsic radiosensitivity of 27 canine cancer cell lines derived from ten tumor types was determined using a clonogenic assay. The 27 cell lines had varying radiosensitivities regardless tumor type (survival fraction at 2 Gy, SF2 = 0.19–0.93). In order to understand parameters that might contribute to intrinsic radiosensitivity, we evaluated the relationships of cellular radiosensitivity with basic cellular characteristics of the cell lines. There was no significant correlation of SF2 with S-phase fraction, doubling time, chromosome number, ploidy, or number of metacentric chromosomes, while there was a statistically significant correlation between SF2 and plating efficiency. Next, we selected the five most radiosensitive cell lines as the radiosensitive group and the five most radioresistant cell lines as the radioresistant group. Then, we evaluated known parameters for cell killing by ionizing radiation, including radiation-induced DNA double strand break (DSB) repair and apoptosis, in the radiosensitive group as compared to the radioresistant group. High levels of residual γ-H2AX foci at the sites of DSBs were present in the four out of the five radiosensitive canine cancer cell lines. Our studies suggested that substantial differences in intrinsic radiosensitivity exist in canine cancer cell lines, and radiation-induced DSB repair was related to radiosensitivity, which is consistent with previous human studies. These data may assist further investigations focusing on the detection of DSB for predicting individual response to radiation therapy for dogs, regardless of tumor type.

Differences in DNA Repair Capacity, Cell Death and Transcriptional Response after Irradiation between a Radiosensitive and a Radioresistant Cell Line.

Normal tissue toxicity after radiotherapy shows variability between patients, indicating inter-individual differences in radiosensitivity. Genetic variation probably contributes to these differences. The aim of the present study was to determine if two cell lines, one radiosensitive (RS) and another radioresistant (RR), showed differences in DNA repair capacity, cell viability, cell cycle progression and, in turn, if this response could be characterised by a differential gene expression profile at different post-irradiation times. After irradiation, the RS cell line showed a slower rate of γ-H2AX foci disappearance, a higher frequency of incomplete chromosomal aberrations, a reduced cell viability and a longer disturbance of the cell cycle when compared to the RR cell line. Moreover, a greater and prolonged transcriptional response after irradiation was induced in the RS cell line. Functional analysis showed that 24 h after irradiation genes involved in “DNA damage response”, “direct p53 effectors” and apoptosis were still differentially up-regulated in the RS cell line but not in the RR cell line. The two cell lines showed different response to IR and can be distinguished with cell-based assays and differential gene expression analysis. The results emphasise the importance to identify biomarkers of radiosensitivity for tailoring individualized radiotherapy protocols.

Paris Saponins enhance radiosensitivity in a gefitinib-resistant lung adenocarcinoma cell line by inducing apoptosis and G2/M cell cycle phase arrest.

Acquired resistance to epidermal growth factor inhibitors has been reported to be associated with cross‑resistance to radiation. Paris Saponins (PSs) exert a wide range of pharmacological activities, including cell apoptosis induction, multidrug resistance inhibition, angiogenesis inhibition and tumor cell migration by modulating various signaling pathways. The present study aimed to investigate the radiosensitization effects of PSII, PSVI and PSVII in a gefitinib‑resistant PC‑9‑ZD lung adenocarcinoma cell line, and the possible mechanism underlying their function. A clonogenic assay was performed to determine the effects of PS radiosensitization on the PC‑9‑ZD cell line. The cell cycle was analyzed by flow cytometry, and cell apoptosis was analyzed with Annexin V/propidium iodide and Hoechst staining. Protein expression levels were detected by western blotting. The results of the present study revealed a significant increase in PC‑9‑ZD cell line radiosensitivity following treatment with PSs. PSs induced G2/M cell cycle phase arrest and apoptosis of the irradiated PC‑9‑ZD cells. Notably, the expression levels of B cell lymphoma 2 (Bcl‑2) were downregulated, and those of caspase‑3, Bcl‑2‑associated X protein (Bax) and p21/Waf1/Cip1 were upregulated following treatment with PSs. The present results demonstrated that PSs induced radiosensitivity in gefitinib‑resistant cells by inducing G2/M phase arrest and by enhancing the apoptotic response via the modulation of caspase‑3, Bax, Bcl‑2 and p21/Waf1/Cip1 expression.

Comparison of methods to quantify histone H2AX phosphorylation and its usefulness for prediction of radiosensitivity

Purpose: The number of radio-induced double-strand breaks is correlated with the number of histone gamma-H2AX (γ-H2AX) foci. For this reason, foci quantification is a useful tool to measure radiation-induced DNA damage and the number of foci has been suggested as a predictive biomarker of radiosensitivity. The aim of the present study was to evaluate the reproducibility of different microscopic methodologies and flow cytometry analysis to score γ-H2AX induction, and its suitability to distinguish a radiosensitive (RS) cell line from a radioresistant (RR) one.Materials and methods: γ-H2AX analyses were performed by semi-automated and automated microscopic methods and by flow cytometry before and after irradiation in two human lymphoblastoid cell lines and in lymphocytes from three healthy donors.Results: Reproducible results were obtained by all the methodologies tested, although not all showed the same sensitivity. The RS cell line always showed higher foci counts and higher levels of immunofluorescence intensity after irradiation than the RR cell line.Conclusions: Our results suggest that microscopic methodologies with z-stage capacity give the most accurate results after 1 Gy irradiation. However, for high doses of ionizing radiation, flow cytometry gives reliable results. Further studies will be necessary to determine the usefulness of γ-H2AX analysis to predict adverse side reactions in radiotherapy patients.

Abstract LB-011: Arginine deprivation using ADI-PEG20 leads to regression of an ASS1-ve intracranial GBM tumor in mice and potentiates gamma irradiation of ASS1+ve GBM in vitro

Abstract Patients with Gliobastoma Multiforme (GBM) have an extremely poor overall survival rate. Novel molecular targeted therapies have failed to provide further improvements in these rates and as such the standard of care for GBM patients remains unchanged, consisting of radical surgery followed by chemo and radiotherapy. In light of this, novel therapeutic approaches have to be tested in combination with current protocols for their efficacy. We have previously demonstrated the metabolic dependency of ∼30% of de novo GBM to extracellular arginine. Using ADI-PEG20 to deplete arginine, we showed a marked reduction in the proliferation of primary GBM explants that exhibited methylation in their ASS1 gene, the rate-limiting enzyme in the arginine biosynthetic pathway. We have validated these findings in an animal model where we have demonstrated that ADI-PEG20 treatment induces a profound delay in the growth of ASS1-ve intracranial human GBM tumors in mice. In cell culture models, we show that ADI-PEG20 has comparable cell growth inhibition efficiencies as conventional chemotherapies namely temozolomide, lomustine and chloroquine. Moreover, these agents exhibited inhibitory effects on proliferation in hypoxic conditions (1% O2) representing activity in a more physiological environment. Importantly, combination with ADI-PEG20 did not reduce efficiency of these conventional drugs. Although no synergistic effects of ADI-PEG20 with these chemotherapeutic agents was observed, synergy was detected in combination with irradiation. Here, we showed the ADI-PEG20 radio-sensitized GBM cell lines to photon irradiation regardless of their ASS1 methylation status: In clonogenic assays, there was a 50% enhanced decrease in colony formation with pre-treatment of ADI-PEG20 and subsequent photon irradiation when compared to irradiation alone. These results suggest arginine deprivation therapy as a novel therapeutic strategy for ASS1-ve GBM. Moreover, we show that when combined with irradiation, ADI-PEG20 can be used to treat GBM irrespective of their ASS1 status. Citation Format: Fernando Abaitua, Justyna Przystal, Amin Hajitou, Nelofer Syed. Arginine deprivation using ADI-PEG20 leads to regression of an ASS1-ve intracranial GBM tumor in mice and potentiates gamma irradiation of ASS1+ve GBM in vitro. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-011. doi:10.1158/1538-7445.AM2015-LB-011

Targeting the endoplasmic reticulum mediates radiation sensitivity in colorectal cancer

BackgroundRadiotherapy is an established treatment modality for early and locally advanced rectal cancer as part of short course radiotherapy and long course chemoradiotherapy. The unfolded protein response (UPR) is a cellular stress response pathway often activated in human solid tumours which has been implicated in resistance to both chemotherapy and radiotherapy. This research has investigated whether the UPR pathway is upregulated in ex-vivo samples of human colorectal cancer and characterised the interaction between radiotherapy and UPR activation in two human colorectal cancer cell lines in vitro. MethodsIn vitro UPR expression was determined in response to clinical doses of radiotherapy in both the human colorectal adenocarcinoma (HT-29) cell line and a radio-resistant clone (HT-29R) using western blotting and quantitative polymerase chain reaction. The UPR was induced using a glucose deprivation culture technique before irradiation and radiosensitivity assessed using a clonogenic assay. Ex-vivo human colorectal cancer tissue was immuno-histochemically analysed for expression of the UPR marker glucose regulated protein 78 (GRP-78). ResultsThe UPR was strongly up regulated in ex-vivo human colorectal tumours with 36 of 50 (72.0%) specimens demonstrating moderate to strong staining for the classic UPR marker GRP-78. In vitro, therapeutic doses of radiotherapy did not induce UPR activation in either radiosensitive or radioresistant cell lines. UPR induction caused significant radiosensitisation of the radioresistant cell line (HT-29R SF2Gy=0.90 S.E.M. +/−0.08; HT-29RLG SF2Gy=0.69 S.E.M. +/−0.050). ConclusionThis suggests that UPR induction agents may be potentially useful response modifying agents in patients undergoing therapy for colorectal cancer.

Combined TP53 mutation/3p loss correlates with decreased radiosensitivity and increased matrix-metalloproteinase activity in head and neck carcinoma

Patients with head and neck squamous cell carcinoma (HNSCC) containing TP53 mutation and 3p deletion ("double-hit") have poorer prognosis compared to patients with either event alone ("single-hit"). The etiology for worse clinical outcomes in patients with "double-hit" cancers is unclear. We compared radiosensitivity of cell lines containing both TP53 mutations and deletion of Fragile Histidine Triad (FHIT, the gene most commonly associated with 3p deletion) to "single-hit" lines with only TP53 mutation. We compared radiosensitivity in a "single-hit" cell line with TP53 mutation converted to "double-hit" using RNA interference targeting FHIT. Finally, we compared matrixmetalloproteinase-2/9 (MMP-2/9) activity, a previously-established biomarker for tumor aggressiveness, in xenograft tumors derived from these cell lines. TP53 mutation and FHIT deletion profiles of HNSCC lines were established using Cancer Cell Line Encyclopedia (CCLE). We used RNA-interference to convert a "single-hit" cell line (SCC4) to "double-hit". Cultured cells were examined for radiosensitivity and cisplatin sensitivity. MMP-2/9 activity was evaluated in "double-hit" versus "single-hit" tumors using ratiometric activatable cell-penetrating peptide (RACPP) in tongue (n=17) and flank xenografts (n=4). Radiotherapy caused greater double-stranded DNA breaks in "single-hit" vs naturally occurring and engineered "double-hit" cells. In-vivo, "double-hit" xenografts demonstrated higher MMP-2/9 activity compared to "single-hit" xenografts (p<0.01). There was no difference in cisplatin sensitivity between the cell lines. TP53 mutation combined with FHIT deletion correlates with decreased radiosensitivity in HNC cell lines. Xenograft from "double-hit" cells exhibit increased MMP-2/9 activity. These findings may in part account for the worse clinical outcome seen in patients with HNSCC "double-hit" tumors.

Enhancement of viability of radiosensitive (PBMC) and resistant (MDA-MB-231) clones in low-dose-rate cobalt-60 radiation therapy.

ObjectiveIn the present study, the authors investigated the in vitro behavior of radio-resistant breast adenocarcinoma (MDA-MB-231) cells line and radiosensitive peripheral blood mononuclear cells (PBMC), as a function of different radiation doses, dose rates and postirradiation time kinetics, with a view to the interest of clinical radiotherapy.Materials and MethodsThe cells were irradiated with Co-60, at 2 and 10 Gy and two different exposure rates, 339.56 cGy.min–1 and the other corresponding to one fourth of the standard dose rates, present over a 10-year period of cobalt therapy. Post-irradiation sampling was performed at pre-established kinetics of 24, 48 and 72 hours. The optical density response in viability assay was evaluated and a morphological analysis was performed.ResultsRadiosensitive PBMC showed decrease in viability at 2 Gy, and a more significant decrease at 10 Gy for both dose rates. MDAMB- 231 cells presented viability decrease only at higher dose and dose rate. The results showed MDA-MB-231 clone expansion at low dose rate after 48–72 hours post-radiation.ConclusionLow dose rate shows a possible potential clinical impact involving decrease in management of radio-resistant and radiosensitive tumor cell lines in cobalt therapy for breast cancer.

AKT and MET signalling mediates antiapoptotic radioresistance in head neck cancer cell lines

Induction of apoptosis is a major mechanism of radiosensitivity in different types of cancer. In contrast, EGFR/PI3K/AKT signalling and recently the presence of so-called cancer stem cells are discussed as reasons for radioresistance. The study investigates mechanisms of apoptosis, key oncogenes of the PI3K/AKT pathway and the presence of cancer cells with stem cell properties during irradiation in two cell lines (PCI-9A, and PCI-15) of head and neck squamous cell carcinoma. WST-1-tests, qRT-PCR, western blots and FACS analysis were performed for analysis. The two cell lines presented different degrees of cell death upon irradiation. The radiosensitive cell line PCI-9A showed increased apoptosis after irradiation measured by expressed cleaved caspases 3 and 7 while the radioresistant cell line PCI-15 upregulated antiapoptotic Survivin and BCL2A1 mRNA. Besides, increased PI3K/AKT- and ERK1/2-signalling was associated with radioresistance accompanied by loss of PTEN function through phosphorylation on S380. Blockade of pAKT increased radiation-induced cell death, and moreover, led to an upregulation of pMET in the radioresistant cell line. The percentage of ALDH-positive tumour cells was markedly decreased after irradiation in the radiosensitive cell line. Functional apoptosis is mandatory for sensitivity to irradiation in head neck cancer cells. Upregulation of the AKT-pathway seems to be one reason for poor radioresponse. Activated MET may also predict radioresistance, possibly through ERK1/2 signalling. Moreover MET may indicate the presence of cancer stem cells facilitating radioresistance as shown by increased ALDH expression.

RNA-seq profiling of a radiation resistant and radiation sensitive prostate cancer cell line highlights opposing regulation of DNA repair and targets for radiosensitization.

BackgroundRadiotherapy is a chosen treatment option for prostate cancer patients and while some tumours respond well, up to 50% of patients may experience tumour recurrence. Identification of functionally relevant predictive biomarkers for radioresponse in prostate cancer would enable radioresistant patients to be directed to more appropriate treatment options, avoiding the side-effects of radiotherapy.MethodsUsing an in vitro model to screen for novel biomarkers of radioresistance, transcriptome analysis of a radioresistant (PC-3) and radiosensitive (LNCaP) prostate cancer cell line was performed. Following pathway analysis candidate genes were validated using qRT-PCR. The DNA repair pathway in radioresistant PC-3 cells was then targeted for radiation sensitization using the PARP inhibitor, niacinimide.ResultsOpposing regulation of a DNA repair and replication pathway was observed between PC-3 and LNCaP cells from RNA-seq analysis. Candidate genes BRCA1, RAD51, FANCG, MCM7, CDC6 and ORC1 were identified as being significantly differentially regulated post-irradiation. qRT-PCR validation confirmed BRCA1, RAD51 and FANCG as being significantly differentially regulated at 24 hours post radiotherapy (p-value =0.003, 0.045 and 0.003 respectively). While the radiosensitive LNCaP cells down-regulated BRCA1, FANCG and RAD51, the radioresistant PC-3 cell line up-regulated these candidates to promote cell survival post-radiotherapy and a similar trend was observed for MCM7, CDC6 and ORC1. Inhibition of DNA repair using niacinamide sensitised the radioresistant cells to irradiation, reducing cell survival at 2 Gy from 66% to 44.3% (p-value =0.02).ConclusionsThese findings suggest that the DNA repair candidates identified via RNA-seq hold potential as both targets for radiation sensitization and predictive biomarkers in prostate cancer.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2407-14-808) contains supplementary material, which is available to authorized users.

Abstract 4897: Genetic variants and expression of AEG-1 in relation to clinical outcome and radiotherapy response in colorectal cancer patients and cell lines

Abstract Background: Colorectal cancer (CRC) is the third most common cancer in men and the second in woman worldwide. The therapy of CRC has been critically improved during the past two decades, but the treatment response varies significantly between different treatments and patients. Therefore it is of need to search for biomarkers for more suitable prognosis and treatment. The aim of this study was to investigate genetic variants of the astrocyte elevated gene-1 (AEG-1), its expression in CRC patient samples and colon cancer cell lines and the potential correlation to clinicopathological variables and treatment response. Materials and Methods: We analysed genetic variants and the mRNA and protein expression of AEG-1 in 593 CRC patient samples by direct Sanger sequencing, qPCR and immunohistochemistry. Of the patients, 158 rectal cancer patients were enrolled in the Swedish clinical trial of preoperative radiotherapy (RT). AEG-1 expression in response to γ-irradiation was analysed by Western blot in 5 colon cancer cell lines. We inhibited the AEG-1 expression by siRNA in the cell lines, and their survival was analysed after γ-irradiation. Results: By direct sequencing we found 29 variants, of which 12 were novel. Six of the variants were exonic and 23 intronic. The variant c.1353G&amp;gt;A, rs2331652 was found only in 4 samples and the variant c.1679-6 T&amp;gt;C in only one sample. In the cell lines KM12C, KM12SM and KM12L4a we found a deletion in exon 4 (c.595_598delAGAG). AEG-1 mRNA and protein expression revealed a significant increased AEG-1 expression in the primary tumors and metastases compared to the normal mucosa in all patient cohorts (p&amp;lt;0.006) and on the mRNA level a higher expression in tumors located in the rectum compared to tumors in the colon (p=0.047). In the rectal cancer patients from the Swedish trail of preoperative RT, a high AEG-1 expression correlated with a higher risk of distant recurrence and disease free survival (p=0.001 respectively) independently of the tumor stage, only in patients receiving preoperative RT. AEG-1 knock-down in the radioresistant cell lines KM12L4a, SW480 and SW620 resulted in reduction of the survival after radiation, but not in the radiosensitive cell lines KM12C and HCT116. The AEG-1 expression was up-regulated shortly after 2 Gy γ-radiation in KM12C, KM12L4a and SW480, but not in SW620 and HCT116. Conclusion: We found several novel AEG-1 variants. The AEG-1 expression at the mRNA and/or protein level was up-regulated in the primary tumour and metastases compared to the normal mucosa. Furthermore we showed for the first time that the AEG-1 expression is an independent prognostic factor for distant recurrence and disease-free survival in rectal cancer patients after treatment with preoperative RT. The cell line studies suggest AEG-1 as a promising radiosensitizing target for rectal cancer. Citation Format: Sebastian Gnosa, Veronika Patcha Brodin, Ivana Ticha, Gunnar Adell, Gunnar Arbman, Hong Zhang, Xiao-Feng Sun. Genetic variants and expression of AEG-1 in relation to clinical outcome and radiotherapy response in colorectal cancer patients and cell lines. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4897. doi:10.1158/1538-7445.AM2014-4897

Radioprotective effects of Antrodia cinnamomea are enhanced on immune cells and inhibited on cancer cells

Purpose: The radioprotective effects of Antrodia cinnamomea (AC) were investigated for understanding the potential usefulness of AC as an adjunct treatment for reducing radiation side-effects.Materials and methods: In this study, we determined the ability of AC extracts (AC539) to reduce radiation side-effects by analyzing cellular viability in normal mouse spleen immune cells and human cancer cells with different radiosensitivity. We further detected the effect of AC on radiation-induced changes in cytokine- and inflammatory-related gene expressions. Furthermore, apoptosis assay was performed to determine whether AC could inhibit radiation-induced cytotoxicity.Results: We found that an AC dose of 100–150 μg/ml in a time-dependent manner was the most effective in blocking radiation-induced cytotoxicity, in vitro. Radiation-induced cytotoxicity was inhibited in spleen immune cells by 37–56%; however, pretreatment of human colorectal cancer cell line HT-29 with AC did not have any effect on radiation-induced cytotoxicity, while pretreatment of radiosensitive human breast cancer cell lines BT-474 with AC caused a moderate enhancement of radiation-induced damage. Furthermore, AC pretreatment differentially regulated the mRNA expression of several important immunomodulatory genes in response to irradiation in normal and cancer cells.Conclusions: Our data indicate that AC may inhibit important immunoregulatory signaling which could be vital in the avoidance of an over-activated cytotoxic and inflammatory response of the immune system caused by radiation-induced tissue damage. Additionally, AC does not provide a radioprotective effect to tumor cells but instead enhances radiation-induced inflammation and cytotoxicity in cancer.

Enhancement of gastric cancer MKN28 cell line radiosensitivity induced by β-elemene

To study radiation-enhancing effects on human gastric cancer MKN28 cell line and underlying mechanisms of β-elemene. Inhibition of MKN28 cell proliferation at different concentrations of β-elemene was assessed using the methyl thiazolyl blue colorimetric method (MTT method), with calculation of IC50 value and choice of 20% of the IC50 as the experimental drug concentration. Irradiation group and β-elemene+irradiation group were established, and the cell survival fraction (SF) was calculated from flat panel colony forming analysis, and fitted by the 'multitarget click mathematical model'. Draw the survival curve and get the radiobiological parameters D0, Dq, SF2, N and SER. Flow cytometry (FCM) was used to detect changes in the cell cycle and cell apoptosis rates was detected by Annexin-V/PI assay. β-elemene exerted inhibitory effects on proliferation of gastric cancer MKN28 cells, with an IC50 of 45.6 mg/L and we chose 8 mg/L as the experimental concentration. The cell survival fraction of MKN28 cells with irradiation decreased significantly after treated with β-elemene; D0, Dq decreased, SER = 1.3. After combined treatment of β-elemene+irradiation, the results of FCM showed that cells could be arrested in the G2/M phase and the cell apoptosis increased significantly. β-elemene can enhance the radiosensitivity of gastric cancer MKN28 cell line. Mechanistically, β-elemene mainly influences the cell cycle distribution of MKN28 cells by inducing G2/M phase arrest, inhibits the repair of sublethal damage and induces cell apoptosis to enhance the killing effects of radioactive rays.

SU‐E‐T‐272: Radiation Damage Comparison Between Intensity Modulated Radiotherapy and Field‐In‐Field Technique in Breast Cancer Treatments

Purpose:To compare normal tissue complications between IMRT and FIF treatment in breast cancer.Methods:16 patients treated with IMRT plan and 20 patients treated with FIF plan were evaluated in this study. Both kinds of plans were generated using Eclipse treatment planning system by dosimetrist following clinical radiotherapy treatment guidelines. The plans were reviewed and approved by radiation oncologist. The average survival fraction (SF) for three different normal tissue cells of each concerned structure can be calculated from differential dose volume histogram (DVH) using linear quadratic model. The three types of normal tissues include radiosensitive, moderately radiosensitive and radio‐resistant that represents 70%, 50% and 30% survival fractions, respectively, for a 2‐Gy open field. Equivalent uniform doses (EUD) for corresponding normal tissues of each structure were calculated.Results:The EUDs of the lungs, heart, healthy breast and spinal cord with both IMRT and FIF treatments were calculated. Considering the average value of all IMRT plans, the lung of treated side absorbed 16.0% of dosage prescribed to the tumor if the radiosensitivity of the lung is similar to the radiosensitive cell line. For moderately radiosensitive and radio‐resistant lung tissue, the average EUDs can be 18.9% and 22.4% of prescription. In contrast, patients treated with FIF plans were delivered 6.0%, 7.5% and 10.3% of prescribed dose for radiosensitive, moderately radiosensitive and radio‐resistant lung tissue, respectively. Comparing heart EUDs between IMRT and FIF plans, average absorbed doses in IMRT treatment were 7.7%, 8.7% and 9.7% of prescription for three types of heart normal tissue cell lines while FIF treatments delivered only 1.3%, 1.5% and 1.6% of prescription dose. For the other organs, the results were similar.Conclusion:The results indicated that breast cancer treatment using IMRT technique had more normal tissue damage than FIF treatment. FIF demonstrated more effective normal tissue dose reduction in breast cancer treatment.

Reprint of "The clinical impact of deficiency in DNA non-homologous end-joining".

DNA non-homologous end-joining (NHEJ) is the major DNA double strand break (DSB) repair pathway in mammalian cells. Defects in NHEJ proteins confer marked radiosensitivity in cell lines and mice models, since radiation potently induces DSBs. The process of V(D)J recombination functions during the development of the immune response, and involves the introduction and rejoining of programmed DSBs to generate an array of diverse T and B cells. NHEJ rejoins these programmed DSBs. Consequently, NHEJ deficiency confers (severe) combined immunodeficiency - (S)CID - due to a failure to carry out V(D)J recombination efficiently. NHEJ also functions in class switch recombination, another step enhancing T and B cell diversity. Prompted by these findings, a search for radiosensitivity amongst (S)CID patients revealed a radiosensitive sub-class, defined as RS-SCID. Mutations in NHEJ genes, defining human syndromes deficient in DNA ligase IV (LIG4 Syndrome), XLF-Cernunnos, Artemis or DNA-PKcs, have been identified in such patients. Mutations in XRCC4 or Ku70,80 in patients have not been identified. RS-SCID patients frequently display additional characteristics including microcephaly, dysmorphic facial features and growth delay. Here, we overview the clinical spectrum of RS-SCID patients and discuss our current understanding of the underlying biology.