Relative Radioresistance Research Articles

Enhanced survival of lethally irradiated adenosine A3 receptor knockout mice. A role for hematopoietic growth factors?

Adenosine A3 receptor knockout (A3AR KO) mice and their wild-type (WT) counterparts were compared from the point of view of their abilities to survive exposures to lethal doses of γ-radiation belonging to the range of radiation doses inducing the bone marrow acute radiation syndrome. Parameters of cumulative 30-day survival (experiment using a midlethal radiation dose) or cumulative 11-day survival (experiment using an absolutely lethal radiation dose), and of mean survival time were evaluated. The values of A3AR KO mice always reflected their higher survival in comparison with WT ones, the P values being above the limit for statistical significance after the midlethal radiation dose and standing for statistical significance after the absolutely lethal radiation dose. This finding was considered surprising, taking into account the previously obtained findings on defects in numbers and functional properties of peripheral blood cells in A3AR KO mice. Therefore, previous hematological analyses of A3AR KO mice were supplemented in the present studies with determination of serum levels of the granulocyte colony-stimulating factor, erythropoietin, and thrombopoietin. Though distinct differences in these parameters were observed between A3AR KO and WT mice, none of them could explain the relatively high postirradiation survival of A3AR KO mice. Further studies on these mice comprising also those on other than hemopoietic tissues and organs can help to clarify their relative radioresistance.

Abstract 5438: Resistance to β1 integrin inhibition in HER2 amplified cancers is mediated by HER3

Abstract Our previous work focused on investigating β1 integrin as a target for BC, alone and with radiation therapy. It is well recognized that there is significant cross talk between the EGFR family of receptors and β1 integrin signaling, and a relative resistance of HER2+ BC to β1 integrin inhibitory agents. In 2006, we published our findings that β1 integrin inhibition enhanced the effect of trastuzumab in HER2+ BC. Subsequently, others and we reported that β1 integrin inhibition enhanced the cytostatic effect of multiple HER2-targeted therapies in HER2+ BC. However, the nature of cross talk between β1 integrins and HER2, and the role of β1 integrin in HER2+BC resistance remains unknown. In addition, HER2+BCs have higher rates of local recurrence after radiotherapy, consistent with previous work showing relative radioresistance in HER2+BC. The most potent mitogenic HER2 signaling in HER2+BC occurs upon heterodimerization with HER3. We hypothesized that HER3 could mediate significant resistance to β1 integrin targeting in HER2+BC. To test this, we correlated β1 integrin and HER3 expression levels in SKBR3 cells over several time points using WB. Inhibitions of β1 integrin activity or shRNA knockdown of HER3 lead to upregulation of HER3 and β1 integrin, respectively. To test whether HER3 knockdown enhanced β1 integrin inhibition, we estimated proliferation by quantitating Ki-67 expression in SKBR3 cells in response to treatment. β1 integrin inhibition lead to a ∼50% reduction in Ki-67 positive cells (48%-22%), which was further enhanced by 50% with HER3 knockdown (12%), p<0.05. In addition, HER3 knockdown enhanced the cytostatic effect of ionizing radiation (IR) by ∼50% (32% to 14%), p<0.05. Enhanced cytostasis was correlated with a significant down modulation of p-HER2 and p-473 Akt on WB. In conclusion, our data indicate that HER3 plays a role in mediating resistance to β1 integrin inhibition in HER2+BC. Further mechanistic and in vivo validation are on going. Citation Format: Catherine C. Park, Dhara Amin, Hui Zhang, Mark Moasser. Resistance to β1 integrin inhibition in HER2 amplified cancers is mediated by HER3. [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 5438. doi:10.1158/1538-7445.AM2014-5438

Emerging immune functions of non-hematopoietic stromal cells.

Emerging immune functions of non-hematopoietic stromal cells.

Carbon ion beam is more effective to induce cell death in sphere-type A172 human glioblastoma cells compared with X-rays

Purpose: To obtain human glioblastoma cells A172 expressing stem cell-related protein and comparison of radiosensitivity in these cells with X-rays and carbon beam.Methods: Human monolayer-type A172 glioblastoma cells were maintained in normal medium with 10% bovine serum. In order to obtain sphere-type A172 cells the medium was replaced with serum-free medium supplemented with growth factors. Both types of A172 cells were irradiated with either X-rays or carbon ion beams and their radiosensitivity was evaluated.Results: Serum-free medium induced expression of stem cell-related proteins in A172 cells along with the neurosphere-like appearance. These sphere-type cells were found resistant to both X-rays and carbon ion beams. Phosphorylation of histone H2A family member X persisted for a longer period in the cells exposed to carbon ion beams than in those exposed to X-rays and it disappeared quicker in the sphere type than in the monolayer type. Relative radioresistance of the sphere type cells was smaller for carbon ion beams than for X-rays.Conclusions: We demonstrated that glioblastoma A172 cells with induced stem cell-related proteins turned resistant to irradiation. Accelerated heavy ion particles may have advantage over X-rays in overcoming the tumor resistance due to cell stemness.

Primary Extradural Tumors of the Spine - Case Review with Evidence-guided Management.

Background:Primary extradural tumors of the spine comprise only a small percentage of all spinal tumors. However, given their relative radioresistance and their typical malignant, invasive nature, surgery may be associated with fairly high morbidity and mortality rates. Furthermore, it may be especially difficult to achieve gross total resections with tumor-free margins.Case Descriptions:We present two cases and review the literature regarding the presentation, diagnosis, and evidence-based guidance/treatment of primary extradural spinal tumors. The first patient with an L1 chordoma presented with cauda equina syndrome. Following surgery, the second patient, with a giant cell tumor of the cervicothoracic junction, responded well to the novel drug denosumab, a monoclonal antibody to the RANK ligand.Conclusion:Primary extradural spine tumors pose significant challenges to surgeons as the aim is to achieve satisfactory surgical outcomes with clean tumor margins (e.g, thus avoid recurrence) while minimizing morbidity. Improvements in radiotherapy, chemotherapy, and novel molecular drugs may increase survival rates and improve overall outcomes.

Abstract C215: Sensitivity of PTEN-deficient prostate carcinoma xenografts to ionizing radiation through inhibition of treatment-induced CXCL8 signaling.

Abstract Background: CXCL8 signaling levels are elevated in localized high grade prostate cancer (CaP). We have shown exposure of CaP cells to chemical DNA-damaging agents potentiates CXCL8 signaling, which underpins an autocrine mode of therapeutic resistance. Data from in vitro and in vivo CaP models has shown loss of the tumor suppressor PTEN also increases expression of the pro-inflammatory chemokine CXCL8. Experiments were designed to determine whether exposure to ionising radiation (IR) selectively induced CXC-chemokine signaling in PTEN-deficient CaP cells, and to determine how CXCL8 signaling may modulate their radiosensitivity. Methods: shRNA-directed strategies were used to establish cell-based models of CaP with differential expression of PTEN. These clonal (DU145) and heterogeneous (22Rv1) populations were subjected to IR under normal or hypoxic culture conditions. PTEN was reconstituted in PC3 cells and was driven by tetracycline-regulated expression of the gene. Changes in chemokine expression were analyzed by RT-PCR, immunoblotting and ELISA. Autocrine CXCL8 signaling was attenuated using siRNA to down-regulate gene expression of its receptors, CXCR1 and CXCR2. The effects of modulating chemokine signaling on cell viability following exposure to clinically-relevant doses of IR were assessed by colony formation assays, cell proliferation assays, and analysis of apoptosis and cellular senescence. The effect of CXCL8 signaling inhibition in vivo was determined using a PC3 xenograft model in SCID mice. The cell penetrating pepducin, x1/2pal-i3, was used to attenuate both CXCR1 and CXCR2 and tumor growth was assessed via caliper measurements. Results: Exposure to IR (3 Gy) increased gene expression of CXCL8, CXCR1 and CXCR2 - with PTEN-deficiency enhancing this response. Loss of PTEN expression differentially modulated the radiosensitivty of CaP cell lines: PTEN-depletion conferred relative radioresistance in DU145 cells but made 22RV1 cells more radiosensitive. However, the inhibition of CXCL8 signaling in all PTEN-depleted models resulted in consistently increased radiosensitivity (SER 1.2, 1.13, and 1.39 in DU145, 22RV1, and PC3 CaP cells, respectively; p<0.05). Reconstitution of PTEN expression in PC3 cells abrogated the capacity of CXCL8 signaling blockade to confer radiosensitivity. The combination of IR and CXCL8 signaling-inhibition conferred increased apoptosis in DU145 cells (p53 mutant) but induced premature senescence in 22RV1 cells (p53 WT). In vivo, treatment of PC3 xenografts with x1/2pal-i3 combined with IR (3 Gy) resulted in a significant delay in tumor growth compared to control (median quadrupling time: 42 day x1/2pal-i3 & IR vs. 32 day control & IR; p<0.05). Subsequent analysis of gene expression in these tumors confirmed that CXCL8 signaling inhibition attenuated IR-induced expression of anti-apoptotic proteins Bcl-2 and C-FLIP. Conclusions: Our results demonstrate the role of treatment-induced CXCL8 signaling as a mechanism of resistance to IR in PTEN-depleted CaP cells. Inhibition of IR-induced CXCL8 signaling provides a novel therapeutic opportunity to enhance the radiosensitivity of PTEN-depleted CaP cells. However, mechanistic results indicate that other genetic factors including p53 status dictate the resultant induction of treatment-induced apoptosis. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C215. Citation Format: Chris WD Armstrong, Jonathan A. Coulter, Steven Walker, Richard D. Kennedy, Kevin M. Prise, Joe M. O'Sullivan, David JJ Waugh. Sensitivity of PTEN-deficient prostate carcinoma xenografts to ionizing radiation through inhibition of treatment-induced CXCL8 signaling. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C215.

Radiosensitivity and effect of hypoxia in HPV positive head and neck cancer cells

Background and purposeHPV associated Head and Neck Squamous Cell Carcinoma (HNSCC) represents a distinct subgroup of HNSCC characterized by a favorable prognosis and a distinct molecular biology. Previous data from the randomized DAHANCA 5 trial indicated that HPV positive tumors did not benefit from hypoxic modifications by Nimorazole during radiotherapy, whereas a significant benefit was observed in the HPV negative tumors. However, more studies have demonstrated equal frequencies of hypoxic tumors among HPV-positive and HPV-negative tumors. The aim of the present study was to determine radiosensitivity, the impact of hypoxia and the effect of Nimorazole in HPV positive and HPV negative cell lines. Materials and methodThe used cell lines were: UDSCC2, UMSCC47 and UPCISCC90 (HPV positive) and FaDuDD, UTSCC33 and UTSCC5 (HPV negative). Cells were cultured under normoxic or hypoxic conditions, and gene expression levels of previously established hypoxia induced genes were assessed by qPCR. Cells were irradiated with various doses under normoxia, hypoxia or hypoxia +1mM Nimorazole, and the clonogenic survival was determined. ResultsThe HPV positive and HPV negative cell lines exhibited similar patterns of upregulation of hypoxia induced genes in response to hypoxia. The HPV positive cell lines were up to 2.4 times more radiation sensitive than HPV negative cell lines. However, all HPV positive cells displayed the same response to hypoxia in radiosensitivity, with an OER in the range 2.3–2.9, and a sensitizer effect of Nimorazole of 1.13–1.29, similar to HPV negative cells. ConclusionsAlthough HPV positive cells had a markedly higher radiosensitivity compared to HPV negative cells, they displayed the same relative radioresistance under hypoxia and the same relative sensitizer effect of Nimorazole. The clinical observation that HPV positive patients do not seem to benefit from Nimorazole treatment is not due to inherent differences in hypoxia sensitivity or response to Nimorazole, but can be accounted for by the overall higher radiosensitivity of HPV positive cells.

MO‐D‐WAB‐01: How OMICs Is Going to Impact Research Topics for Medical Physicists

The ongoing revolution in genomics provides many new research opportunities for physicists. Two crucial research areas to advance clinical oncology include the intersections between imaging and genomics, as well as the use of genomic analyses to improve patient management in radiation oncology. Confusingly, the term ‘radiogenomics’ is used for both applications. In the field of radiology, ‘radiogenomics’ refers to the underlying genomic correlates of image features, for example the correlation of tumor biopsies mRNA microarray signatures with image features. In radiation oncology and radiobiology, the term ‘radiogenomics’ refers to the impact of a patient's genotype on the relative radiosensitivity or radioresistance of normal tissues. Tumor biopsy mRNA signatures, for radiosensitivity, hypoxia, or proliferation, have been studied to predict response and to potentially individualize treatments. Blood proteomics has been applied to normal tissue responses such as radiation pneumonitis. Imaging radiogenomics can further be thought of as ‘radiomics’ + genomics, where radiomics is the extraction of quantitative image features that can be incorporated into disease classification schemes or predictive models. We will also touch on the general application of systems modeling that is so important to advancement in modern biology and response modeling. This session will emphasis new opportunities, as well as challenges and obstacles to progress. ‘Omic’ sciences will greatly impact the study and clinical use of tumor control probability and normal tissue complication probability models; the biological interpretation of image features; and the clinical implications of imaging and cancer screening.

Multidisciplinary Approach to Brain Metastasis from Melanoma; Local Therapies for Central Nervous System Metastases

The overall treatment paradigm for melanoma brain metastases continues to evolve and reflects the relative radioresistance of this histology, as well as the effect of emerging systemic therapies with central nervous system (CNS) activity. Local therapies, including surgery, whole brain radiotherapy (WBRT), and stereotactic radiosurgery (SRS), play an important role in the multidisciplinary management of melanoma brain metastases. Treatment selection for local therapies must consider many factors: (1) size, number, and location of lesions, (2) presence or absence of neurological symptoms, (3) extracranial disease status, expected survival, age, and performance status, (4) prior treatment history, (5) expected treatment toxicities, and (6) predicted response to systemic therapies. The choice of treatment modalities for brain metastases is among the most controversial areas in oncology. There has been a trend toward reduced use of WBRT and increased reliance on SRS and surgery for melanoma brain metastases. Although no prospective randomized data exist comparing local therapies for melanoma brain metastases, several large retrospective studies suggest aggressive local treatment with modalities including surgery and SRS are associated with favorable outcomes in select patients. Multidisciplinary collaboration is required to facilitate a treatment plan that balances reduction in risk of neurological death and symptomatic progression against the risk of treatment-related toxicity.

Abstract 4160: miR-34a as a radio sensitizer of triple negative breast cancer.

Abstract Introduction: Triple negative breast cancer (TNBC) is known to be relatively resistant to radiation therapy resulting in a comparatively higher rates of locoregional recurrence compared with non-TNBC patients. The mechanisms behind this relative radio resistance remain unknown. The goal of this study is to investigate the role of three miRNAs namely, miR-34a, miR-21, and miR-210, which are implicated in DNA damage-repair process, in the response of TNBC cell lines to radiation therapy. Methods: Seven TNBC breast cancer cell lines were used for the study. The levels of miR-34a, miR-21 and miR-210 were evaluated by taqman- based quantitative PCR assay. These cells were exposed to 2 Gy radiation dose and colonogenic survival was assessed after about 2 weeks. Survival fraction after 2 Gy (SF2), which is the ratio of number of cell colonies formed after 2 Gy radiation vs. the number of cell colonies with out radiation, was determined. The SF2 factor is a reliable index to measure radio sensitivity, greater the SF2 factor more radio resistant the cells are. Results: The SF2 value of the TNBC cells varied from 0.31 to 0.74 with MDA-MB-468, HCC-70 being the most radio sensitive cell lines and MDA-MB-436, BT-20 being the most radio resistant cell lines. MDA-MB- 231, BT-549 and Hs 578T were found to be moderately radio resistant breast cancer lines. The oncomiR -21 expression levels in these 7 TNBC cell lines varied from 0.85 to 4.18 fold with a very poor correlation with SF2 (r2=0.08). The oncomiR 210 levels varied from 0.49 to 9.19 fold and also did not exhibit any correlation with radio resistance in TNBC cells (r2= 0.141). Whereas the tumor suppressor miR, miR-34a expression showed an inverse correlation with radio resistance (r2=0.8) in TNBC cells. The radio resistant cell line (e.g., MDA-MB-436, SF2 = 0.74) expressed significantly low levels of miR-34a (0.016 fold) relative to miR -34a levels (set as 1) in HCC 70, which was found to be a radiosensitive cell line with SF2 of 0.309. Conclusions: Our preliminary data indicates that miR 34a may play a role in the response of TNBC cells to radiotherapy. Citation Format: Anjana Bhardwaj, Nivetha Ganesan, David Molkentine, Uma Raju, Isabelle Bedrosian. miR-34a as a radio sensitizer of triple negative breast cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4160. doi:10.1158/1538-7445.AM2013-4160

A potential role for resveratrol as a radiation sensitizer for melanoma treatment

BackgroundRadiotherapy (XRT) is used to improve local control of melanoma and for palliation of metastatic disease. Clinical use of XRT for melanoma is often limited by extent of disease and the relative radioresistance of melanoma may limit the effectiveness of XRT. Our group and others have previously shown that resveratrol (RSV) enhances radiation sensitivity in radioresistant prostate cancer cell lines. Material and MethodsIn this study, the effects of XRT in combination with RSV on radioresistant melanoma lines, SK-Mel-5 and HTB-65, were evaluated by assessment of proliferation and apoptosis. Clonogenic assay, comparison of proliferating cell nuclear antigen staining, Quick Cell Proliferation assay, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining and caspase-3 activity assay were used to assess proliferation and apoptosis, as appropriate. ResultsWe found that the percentage of colonies, proliferating cell nuclear antigen + cells and the optical density value of melanoma cells were decreased after addition of RSV to XRT (XRT/RSV). TUNEL + cells and the relative caspase-3 activity in melanoma cells were increased after addition of RSV to XRT (XRT/RSV). We investigated the possible molecular mechanisms of decreased proliferation and increased apoptosis by using reverse transcriptase-polymerase chain reaction and immunohistochemical staining. The anti-proliferative effect of XRT/RSV correlated with decreased expression of pro-proliferative molecule cyclin B, cyclin D, cdk2 and cdk4. The pro-apoptotic effect of XRT/RSV correlated with decreased expression of the anti-apoptotic molecule FLIP, Bcl-2, and survivin. ConclusionThese data suggest that RSV enhances radiation sensitivity of melanoma cells by inhibiting proliferation and promoting apoptosis. Resveratrol may have a potential role as a radiation sensitizer for melanoma treatment.

Multidisciplinary Approach to Brain Metastasis from Melanoma; Local Therapies for Central Nervous System Metastases

The overall treatment paradigm for melanoma brain metastases continues to evolve and reflects the relative radioresistance of this histology, as well as the effect of emerging systemic therapies with central nervous system (CNS) activity. Local therapies, including surgery, whole brain radiotherapy (WBRT), and stereotactic radiosurgery (SRS), play an important role in the multidisciplinary management of melanoma brain metastases. Treatment selection for local therapies must consider many factors: (1) size, number, and location of lesions, (2) presence or absence of neurological symptoms, (3) extracranial disease status, expected survival, age, and performance status, (4) prior treatment history, (5) expected treatment toxicities, and (6) predicted response to systemic therapies. The choice of treatment modalities for brain metastases is among the most controversial areas in oncology. There has been a trend toward reduced use of WBRT and increased reliance on SRS and surgery for melanoma brain metastases. Although no prospective randomized data exist comparing local therapies for melanoma brain metastases, several large retrospective studies suggest aggressive local treatment with modalities including surgery and SRS are associated with favorable outcomes in select patients. Multidisciplinary collaboration is required to facilitate a treatment plan that balances reduction in risk of neurological death and symptomatic progression against the risk of treatment-related toxicity.

PTEN Modulation of Androgen Receptor Response to External Beam Radiation in Murine Prostate Cancer Cell Lines

Loss of the phosphatase and tensin homolog (PTEN) tumor-suppressor function is a frequent event associated with malignancy in a number of disease sites, including glioblastoma, endometrial cancer, and prostate cancer (PCa). The major role of PTEN is to inhibit phosphatidylinositol 3,4,5-triphosphate (PIP3)-mediated signal transduction pathways, such as the phosphatidylinositol 3-kinase (PI3K)/Akt pathway. Our recent study showed that deletion of the PTEN gene is associated with relative radioresistance in PCa cells, compared with PTEN wild-type cells.

Resistance of Glioblastoma-Initiating Cells to Radiation Mediated by the Tumor Microenvironment Can Be Abolished by Inhibiting Transforming Growth Factor-β

The poor prognosis of glioblastoma (GBM) routinely treated with ionizing radiation (IR) has been attributed to the relative radioresistance of glioma-initiating cells (GIC). Other studies indicate that although GIC are sensitive, the response is mediated by undefined factors in the microenvironment. GBM produce abundant transforming growth factor-β (TGF-β), a pleotropic cytokine that promotes effective DNA damage response. Consistent with this, radiation sensitivity, as measured by clonogenic assay of cultured murine (GL261) and human (U251, U87MG) glioma cell lines, increased by approximately 25% when treated with LY364947, a small-molecule inhibitor of TGF-β type I receptor kinase, before irradiation. Mice bearing GL261 flank tumors treated with 1D11, a pan-isoform TGF-β neutralizing antibody, exhibited significantly increased tumor growth delay following IR. GL261 neurosphere cultures were used to evaluate GIC. LY364947 had no effect on the primary or secondary neurosphere-forming capacity. IR decreased primary neurosphere formation by 28%, but did not reduce secondary neurosphere formation. In contrast, LY364947 treatment before IR decreased primary neurosphere formation by 75% and secondary neurosphere formation by 68%. Notably, GL261 neurospheres produced 3.7-fold more TGF-β per cell compared with conventional culture, suggesting that TGF-β production by GIC promotes effective DNA damage response and self-renewal, which creates microenvironment-mediated resistance. Consistent with this, LY364947 treatment in irradiated GL261 neurosphere-derived cells decreased DNA damage responses, H2AX and p53 phosphorylation, and induction of self-renewal signals, Notch1 and CXCR4. These data motivate the use of TGF-β inhibitors with radiation to improve therapeutic response in patients with GBM.

Abstract 3457: Galectin-1 suppression enhances combined anti-EGFR and radiation-therapy of NSCLC

Abstract Lung cancer remains the leading cause of cancer related death worldwide and will account for nearly 160,000 deaths in the United States alone in 2010. Between 80-90% of all cases diagnosed are classified as non-small cell lung cancer (NSCLC). Recent studies have shown a significant subpopulation of patients diagnosed with NSCLC have an activation of the epidermal growth factor receptor (EGFR) domain resulting from gene amplification, overexpression, or kinse-domain activating mutations. EGFR inhibitors such as Erlotinib and Gefitnib have shown promising results in this subpopulation of patients however median overall survival remains poor. LSGAL1, Galectin-1 (GAL1), is a beta-galactoside-binding protein we recently identified to play an important role in the activation of the PI3-Kinase pathway located directly downstream of EGFR. Silencing Galectin-1 in combination with an EGFR-inhibitor and radiation therapy may be a promising therapeutic strategy for patients with NSCLC. Using a short-hairpin RNA strategy we silenced GAL1 expression in four different NCSLC cell lines and assessed their relative radioresistance via clonogenic survival assay in the presence and absence of an EGFR inhibitor. In order to elucidate the mechanism between GAL1 and EGFR, western blotting and QPRC analysis was performed on downstream pathway members, specifically the RAS/PI3-Kinase and RAS/ERK signaling cascades. Functional assays focusing on proliferation/survival were carried out to determine the effect silencing GAL1 had on the combination of EGFR inhibition and radiation therapy in our NSCLC cell lines. Our preliminary results suggest silencing GAL1 reduces the clonogenic survival of NSCLC cells when used in combination with an EGFR inhibitor following irradiation. In addition well known players within PI3-Kinase pathway such as pAKT S473 appear to be altered in the absence of GAL1. Our preliminary findings suggest GAL1 is a promising therapeutic target in NSCLC when used in combination with an EGFR inhibitor and radiation therapy and is worthy of further investigation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3457. doi:1538-7445.AM2012-3457

Resveratrol enhances radiation sensitivity in prostate cancer by inhibiting cell proliferation and promoting cell senescence and apoptosis

Radiation therapy (XRT) for treatment of localized prostate cancer (PCA) has outcomes similar to surgery and medical therapy. Toxicities of XRT and the relative radioresistance of PCA limit the effectiveness of this treatment method. Safe and effective radiosensitizing agents are lacking to enhance the effectiveness for XRT for PCA. In this study, the effect of XRT in combination with the radiosensitizing agent resveratrol (RSV) was investigated in a radioresistant PCA cell line, PC-3. Our results show the addition of RSV to XRT (XRT/RSV) synergistically enhanced XRT-induced apoptosis and inhibition of PC-3 proliferation. The antiproliferative effect of XRT/RSV treatment correlated with increased expression of p15, p21, and mutant p53 and decreased expression of cyclin B, cyclin D, and cdk2. Increased apoptosis correlated with increased expression of Fas and TRAILR1. Furthermore, XRT/RSV had little effect on the expression of p-AKT, whereas it increased the expression level of p-H2A.X, a marker for senescence. These data highlight the potential of RSV as a radiation sensitizer for PCA treatment and warrant further investigation.

Editorial: Chordoma model

Patients suffering from chordoma, a mesenchymal cancer thought to arise from the notochord, face limited treatment options.1,5 Although this bone tumor can on occasion metastasize to distant sites, a major clinical challenge is imposed by infiltration of the tumor cells into surrounding structures that can limit the extent of resection. Irradiation prolongs survival, but the relative radioresistance demands delivery of a high dose to sensitive regions. To date, there are no approved medical treatments for chordoma, and efforts to identify effective drugs face barriers. First, there are only few established chordoma cell lines. This limitation presents a challenge to broadening our understanding of signaling pathways that can be targeted, and to verifying the significance of chordoma genomic alterations. Second, consistently reproducible in vivo models are lacking. The list of promising agents obtained from high throughput in vitro screening methods can be strategically shortened prior to human trials by testing in animal models. Presence of such barriers restricts progress and contributes to the poor outcome of patients with recurrent disease. In their article in the Journal of Neurosurgery, Siu and colleagues6 describe a primary human chordoma xenograft model. The authors report that 1 of the 2 chordoma tumors implanted into athymic nude mice produced a serially transplantable xenograft that retains high genomic fidelity to the parental tumor. Additional comparative characterization of the tumors provides compelling evidence for successful establishment of a primary chordoma xenograft in that physaliphorous morphology and brachyury expression are maintained. Although this report describes successful implantation and propagation of a single specimen, the achievement is nevertheless important. Rather than dissociating the chordoma tumor tissue into single cells, culturing with animal serum on a plastic dish, and transplanting it into an in vivo environment, the investigators developed a primary xenograft that can be serially passaged. A primary xenograft better mirrors the original tumor compared with xenograft established from in vitro expanded tumor cells, and likely explains the greater than 99.9% genomic concordance observed by the investigators. UCH-1, an established chordoma cell line, can be xenografted, but it appears to require a highly immunodeficient background lacking natural killer cell activity (NOD-SCID IL-2 Receptor Gamma Receptor Null).4 The tumor reported by Siu and colleagues was derived from a patient with a clival chordoma. Most chordoma research is performed with tissues and cells derived from sacral chordomas, presumably because of the availability of a greater quantity of material. However, balanced representation will be important, considering that the development of the notochord demonstrates distinct regional morphogenetic origins, suggesting a histogenic basis for intertumoral heterogeneity.7 Modeling human diseases in animals allows for greater appreciation for pathogenesis, in addition to proving a platform to test potential drugs. The study investigators report that brachyury expression was higher in the xenograft than the primary tumor. Determining the mechanism responsible for upregulation of this important transcription factor would be of interest, and to see if it may be associated with enhanced proliferative index. Also, subsets of chordomas demonstrate loss of critical tumor suppressors PTEN or CDKN2A, disruptions potentially capable of altering the tumorigenicity of the chordoma cells.2,3 Molecular profiling of the parental tumor and xenograft may be worthwhile. Lastly, although chordomas can grow in a subcutaneous environment by direct invasion or metastasis, they are primary bone neoplasms. Establishing an orthotopic model by tumor implantation into trabecular bone would represent further progress in understanding this challenging disease. (http://thejns.org/doi/abs/10.3171/2011.10.JNS111716)

Neutron medical treatment of tumours — a survey of facilities

Neutron therapy has two branches: Fast Neutron Therapy (FNT) and Boron Neutron Capture Therapy (BNCT). The mean neutron energies used for FNT range from 2 MeV to 25 MeV whereas the maximum energy for BNCT is about 10 keV. Neutron generators for FNT have been cyclotrons, accelerators and reactors, whereas BNCT is so far bound to reactors. Both therapies use the effects of high-LET radiation (secondary recoil protons and alpha particles, respectively) and can attack otherwise radioresistant tumours, however, with the hazard of adverse effects for irradiated healthy tissue.FNT has been administered to about 30,000 patients world-wide. From formerly 40 facilities, only eight are operational or stand-by today. The reasons for this development have been, on the one hand, related to technical and economical conditions; on the other hand, strong side effects and insufficient proof of clinical results in the early years as well as increasing competition with new clinical methods have reduced patient numbers. In fact, strict observations of indications, appropriate therapy-planning including low-LET radiation, and consequent treatment of side effects have lead to remarkable results in the meantime.BNCT initially was developed for the treatment of extremely aggressive forms of brain tumour, taking advantage of the action of the blood-brain-barrier which allows for a boronated compound to be selectively enriched in tumour cells. Meanwhile, also malignant melanoma (MM) and Head-and-Neck (H&T) tumours are treated because of their relative radioresistance. At present, epithermal beams with sufficient flux are available only at two facilities. Existing research reactors were indispensable in the development of BNCT, but are to be replaced by hospital-based epithermal neutron sources. Clinical results indicate significantly increased survival times, but the number of patients ever treated is still below 1,000.3D-dose calculation systems have been developed at several facilities and guarantee a high safety for both therapies, FNT and BNCT.

Non-Cytotoxic Radiosensitizers in Brain Radiotherapy: Journey Till the First Decade of this Millennium

Brain tumors, primary and metastatic, are a cause of significant mortality and morbidity. Radiotherapy (RT) forms an integral part of the treatment of brain tumors. Intrinsic relative tumor radio-resistance, normal tissue tolerance and impact on neurocognitive function, all limit the efficacy of RT. Radiosensitizers can potentially increase efficacy on tumors while maintaining normal tissue toxicity, with or without inherent cytotoxicity. This article reviews the evolution of evidence with use of non-cytotoxic radiosensitizers in brain radiotherapy and their status at the end of the first decade of this millennium. Considering, the era of development and mechanism of action, these agents are classified as first, second and third-generation non-cytotoxic radiosensitizers. The last millennium involved elaboration of first-generation compounds including halogenated pyrimidines, hypoxic cell sensitizers (e.g. imidazoles) and glycolytic inhibitors (e.g. lonidamine). The first decade of this millennium has highlighted redox modulators like motexafin gadolinium and newer hypoxic cell sensitizers like efaproxiral, which have shown promise. However, phase III trials and meta-analyses have not identified a clear winner though the second-generation has shown some rays of hope. Recent research has focused on expanding the horizon by studying modulation of newer molecular pathways like DNA repair, microtubule stabilization, cytokine function and nuclear factor-kappa beta (NF-KB) in order to increase RT efficacy. The review concludes by summarizing the class of evidence and the level of recommendation available for use of non-cytotoxic radiosensitizers in brain RT.

Radioresistance of human glioma spheroids and expression of HSP70, p53 and EGFr.

BackgroundRadiation therapy is routinely prescribed for high-grade malignant gliomas. However, the efficacy of this therapeutic modality is often limited by the occurrence of radioresistance, reflected as a diminished susceptibility of the irradiated cells to undergo cell death. Thus, cells have evolved an elegant system in response to ionizing radiation induced DNA damage, where p53, Hsp70 and/or EGFr may play an important role in the process. In the present study, we investigated whether the content of p53, Hsp70 and EGFr are associated to glioblastoma (GBM) cell radioresistance.MethodsSpheroids from U-87MG and MO59J cell lines as well as spheroids derived from primary culture of tumor tissue of one GBM patient (UGBM1) were irradiated (5, 10 and 20 Gy), their relative radioresistance were established and the p53, Hsp70 and EGFr contents were immunohistochemically determined. Moreover, we investigated whether EGFr-phospho-Akt and EGFr-MEK-ERK pathways can induce GBM radioresistance using inhibitors of activation of ERK (PD098059) and Akt (wortmannin).ResultsAt 5 Gy irradiation UGBM1 and U-87MG spheroids showed growth inhibition whereas the MO59J spheroid was relatively radioresistant. Overall, no significant changes in p53 and Hsp70 expression were found following 5 Gy irradiation treatment in all spheroids studied. The only difference observed in Hsp70 content was the periphery distribution in MO59J spheroids. However, 5 Gy treatment induced a significant increase on the EGFr levels in MO59J spheroids. Furthermore, treatment with inhibitors of activation of ERK (PD098059) and Akt (wortmannin) leads to radiosensitization of MO59J spheroids.ConclusionsThese results indicate that the PI3K-Akt and MEK-ERK pathways triggered by EGFr confer GBM radioresistance.