Radiation-resistant Tumors Research Articles

Maintenance of Tight Junction Integrity in the Absence of Vascular Dilation in the Brain of Mice Exposed to Ultra-High-Dose-Rate FLASH Irradiation.

Persistent vasculature abnormalities contribute to an altered CNS microenvironment that further compromises the integrity of the blood-brain barrier and exposes the brain to a host of neurotoxic conditions. Standard radiation therapy at conventional (CONV) dose rate elicits short-term damage to the blood-brain barrier by disrupting supportive cells, vasculature volume and tight junction proteins. While current clinical applications of cranial radiotherapy use dose fractionation to reduce normal tissue damage, these treatments still cause significant complications. While dose escalation enhances treatment of radiation-resistant tumors, methods to subvert normal tissue damage are clearly needed. In this regard, we have recently developed a new modality of irradiation based on the use of ultra-high-dose-rate FLASH that does not induce the classical pathogenic patterns caused by CONV irradiation. In previous work, we optimized the physical parameters required to minimize normal brain toxicity (i.e., FLASH, instantaneous intra-pulse dose rate, 6.9 · 106 Gy/s, at a mean dose rate of 2,500 Gy/s), which we then used in the current study to determine the effect of FLASH on the integrity of the vasculature and the blood-brain barrier. Both early (24 h, one week) and late (one month) timepoints postirradiation were investigated using C57Bl/6J female mice exposed to whole-brain irradiation delivered in single doses of 25 Gy and 10 Gy, respectively, using CONV (0.09 Gy/s) or FLASH (>106 Gy/s). While the majority of changes found one day postirradiation were minimal, FLASH was found to reduce levels of apoptosis in the neurogenic regions of the brain at this time. At one week and one month postirradiation, CONV was found to induce vascular dilation, a well described sign of vascular alteration, while FLASH minimized these effects. These results were positively correlated with and temporally coincident to changes in the immunostaining of the vasodilator eNOS colocalized to the vasculature, suggestive of possible dysregulation in blood flow at these latter times. Overall expression of the tight junction proteins, occludin and claudin-5, which was significantly reduced after CONV irradiation, remained unchanged in the FLASH-irradiated brains at one and four weeks postirradiation. Our data further confirm that, compared to isodoses of CONV irradiation known to elicit detrimental effects, FLASH does not damage the normal vasculature. These data now provide the first evidence that FLASH preserves microvasculature integrity in the brain, which may prove beneficial to cognition while allowing for better tumor control in the clinic.

Early Changes of Diffusion MRI Predict Radiation Therapy Effects in Esophageal Cancer

Concurrent chemoradiation (CRT) is the standard therapy for inoperable locally advanced esophageal cancer (LAEC). However, patients who are insensitive to CRT (20∼30%) may be harmed unnecessarily by the treatment toxicity without survival benefit. An early prediction of treatment response during therapy using non-invasive imaging could identify the patients at high-risk of poor response for individualized adaptive treatment. This study aimed to investigate physiological changes in LAEC using diffusion and perfusion MRI for early predicting treatment response to CRT. Sixty-seven LAEC patients (median age of 64 years) treated with CRT were enrolled in an IRB approved study. All patients received definite thoracic radiotherapy (RT) with a median dose of 60Gy and 30fx, and 73% received concurrent chemotherapy. MRI scans were performed pre-RT and at week 3 during RT (mid-RT), including diffusion weighed images to derive apparent diffusion coefficient (ADC) and dynamic contrast-enhanced images to quantify the fractional blood volume (BV). Gross tumor volume (GTV) was delineated on T2 weighted images. Within the GTV, the hypercellularity volume (VHC) was defined as ADC <1.86x10-3 mm2/s, and the high BV volume (VHBV) as BV >18.2 ml/(100g). ROC curve was applied to assess the prediction abilities of the imaging metrics for CRT outcomes. Associations of the imaging metrics pre-RT and mid-RT and their changes during RT with progression-free survival (PFS) of patients were analyzed by Cox proportional hazards regression analysis. With a median follow-up period of 35.1 months (range 20–41 months), median PFS was 10.1 months. For all patients, the median pre-RT GTV was 28cc±3.2cc, with decreasing of -32.5% ±7.2% to 16.5cc±2.2cc at mid RT. Respectively, VHC and VHBV decreased from 6cc±1.1cc and 4.5cc±1.1cc at pre-RT to 4.1cc±0.7cc and 3.2cc±0.7cc at mid-RT. Smaller VHC at mid-RT (AUC=0.65, p=0.03) and more decreasing in VHC at mid-RT (AUC=0.7, p=0.007) were associated with longer PFS (Table 1). No significant predictive effects were shown in GTV and VHBV. This study suggests that VHC may represent aggressive subvolumes in LAEC. Further analysis will be carried out to correlate the changes in image-phenotype subvolumes with local failure to determine the radiation-resistant tumor subvolumes, which may benefit from treatment intensification.Abstract 1033; Table 1Univariable and multivariable Cox proportional hazards regression analysisCut-off valuesHR95%CIP valueHR95%CIP valueGTVPre-RT33.1cc1.590.88-2.880.13GTVMid-RT13.3cc1.060.63-1.740.89GTVchange-54%1.090.55-2.160.80VHCPre-RT7.3cc1.470.81-2.680.21VHCMid-RT1.1cc2.281.10-4.770.03*2.020.95-4.280.66VHCchange-63%1.950.99-3.820.05*1.680.85-3.330.14VHBVPre-RT10.4cc1.470.94-2.740.14VHBVMid-RT3.3cc1.290.71-2.340.39VHBVchange-54%1.450.75-2.790.27* Statistically significant. Open table in a new tab

198 - Genome-scale metabolic modeling identifies novel targets of redox metabolism in radiation-resistant tumors

Ionizing radiation results in the generation of reactive oxygen species, causing DNA damage and a depletion of the antioxidative capacities of cancer cells. Tumors that are resistant to radiation therapy rely on the production of reducing equivalents and maintenance of redox homeostasis to overcome the damaging effects of ionizing radiation. To identify components of redox metabolism that can be targeted to improve radiation sensitivity in individual patient tumors, we have developed personalized genome-scale metabolic models of 716 radiation-sensitive and 199 radiation-resistant tumors using genomic and transcriptomic data from The Cancer Genome Atlas. Through incorporation of multi-omic, kinetic, and thermodynamic information, these computational models can quantitatively predict maximum metabolite production and steady-state reaction fluxes within individual tumors. Metabolic models predict that radiation-resistant tumors show increased reduction of NAD+ to NADH (p = 4.5e-4) and NADP+ to NADPH (p = 8.5e-3), as well as increased reduction of glutathione (p = 4.5e-6). Enhanced NADPH production allows radiation-resistant tumors to produce greater levels of deoxyribonucleotides (p = 1.3e-10), which are needed for DNA damage repair after ionizing radiation. The increase in reduction of NADP+ to NADPH in radiation-resistant tumors is eliminated when simulating hypoxic conditions, demonstrating the importance of oxygen availability in radiation therapy response. By performing a simulated knockout screen of 3,268 genes throughout the human metabolic network, we identified 47 knockouts that caused a significantly greater decrease in NADP+ reduction in radiation-resistant tumors compared to radiation-sensitive tumors (adjusted p

Altering the response to radiation: radiosensitizers and targeted therapies in pancreatic ductal adenocarcinoma: preclinical and emerging clinical evidence.

Radiation therapy continues to have an evolving role in pancreatic ductal adenocarcinoma. While metastatic failure likely contributes to the majority of patient mortality, achieving local control through surgery and/or radiation appears to be important as certain studies suggest that mortality is contributed by local failure. Many studies support that pancreatic cancer is a relatively radiation resistant tumor type. In addition, the ability to further improve radiation through dose escalation strategies in the non-metastatic setting is hampered by closeness of normal organs, including small bowel and stomach, to the tumor. Thus subverting molecular pathways that promote radiation resistance will be critical to further success of radiation in this disease. There is a wealth of preclinical data supporting the targeting of various molecular pathways in combination with radiation therapy, including DNA repair, cell cycle checkpoint proteins, receptor tyrosine kinases, oncoproteins, stem cells, and immunomodulation. A number of clinical trials have been completed or are on-going with novel molecular inhibitors. In this review, we summarize existing preclinical and clinical molecular strategies for improving the efficacy of radiation in pancreatic cancer, and highlight recent and ongoing clinical trials combining radiation and various targeted therapies.

Quantitative diffuse reflectance spectroscopy of short-term changes in tumor oxygenation after radiation in a matched model of radiation resistance.

There is a critical need to identify patients with radiation-resistant tumors early after treatment commencement. In this study, we use diffuse reflectance spectroscopy (DRS) to investigate changes in vascular oxygenation and total hemoglobin concentration in A549 radiation-sensitive and resistant tumors treated with a clinically relevant dose fraction of 2 Gy. DRS spectra were acquired before, immediately after, 24, and 48 hours after radiation. Our data reveals a significantly higher reoxygenation (sO2) in the radiation-resistant tumors 24 and 48h after treatment, and provides promising evidence that DRS can discern between the reoxygenation trends of radiation-sensitive and resistant tumors.

Radiation resistance of the lung adenocarcinoma is related to the AKT-Onzin-POU5F1 axis

Non-small cell lung carcinoma is the predominant type of lung cancer, and shows an easily developable tolerance to radiotherapy. Cancer stem cells are suggested to be involved in the resistance against therapies. Onzin might be accumulated during the process tumor overcoming the radiation stress. To address the relationship between Onzin, stemness and radiation resistance, we treated the lung cancer tumor bearing mice with radiaotherapy and observed the differences between radiation sensitive (RS) and resistant (RR) tumors. Immunohistochemistry and HE staining were used to observe Onzin and POU5F1 expression in tumor tissues. Quantitative realtime-PCR and Western blot were applied for Onzin and POU5F1 in tumors and cells. In-vitro cellular viability was assessed by CCK8 methods for tumor derived cells. The stably transfected A549 cell lines overexpressing Onzin were generated through lentivirus transfection. After radiotherapy, those RR adenocarcinoma tumors and cells derived from them showed an increased Onzin expression. Further, RR cells were found upregulated stemness, indicated by increased sphericity and proliferation, as well as POU5F1 expression. Next, we overexpressed Onzin in the A549 cells and found an elevated POU5F1 expression, increased proliferation, and enhanced sphericity. Moreover, this could be suppressed by the AKT inhibitor MK-2260. In vivo, the A549 cells overexpressing Onzin showed not only higher tumor formation capability and growth, but also a significant resistance to radiation. Taken together, RR tumors have upregulated Onzin and POU5F1 expression. Ectopic expression of Onzin promotes the POU5F1 expression as well as stemness functions, and confers adenocarcinomas the resistance to radiotherapy.

Toll-like receptor 3 signal augments radiation-induced tumor growth retardation in a murine model.

Radiotherapy induces anti‐tumor immunity by induction of tumor antigens and damage‐associated molecular patterns (DAMP). DNA, a representative DAMP in radiotherapy, activates the stimulator of interferon genes (STING) pathway which enhances the immune response. However, the immune response does not always parallel the inflammation associated with radiotherapy. This lack of correspondence may, in part, explain the radiation‐resistance of tumors. Additive immunotherapy is expected to revive tumor‐specific CTL facilitating radiation‐resistant tumor shrinkage. Herein pre‐administration of the double‐stranded RNA, polyinosinic‐polycytidylic acid (polyI:C), in conjunction with radiotherapy, was shown to foster tumor suppression in mice bearing radioresistant, ovalbumin‐expressing Lewis lung carcinoma (LLC). Extrinsic injection of tumor antigen was not required for tumor suppression. No STING‐ and CTL‐response was induced by radiation in the implant tumor. PolyI:C was more effective for induction of tumor growth retardation at 1 day before radiation than at post‐treatment. PolyI:C targeted Toll‐like receptor 3 with minimal effect on the mitochondrial antiviral‐signaling protein pathway. Likewise, the STING pathway barely contributed to LLC tumor suppression. PolyI:C primed antigen‐presenting dendritic cells in draining lymph nodes to induce proliferation of antigen‐specific CTL. By combination therapy, CTL efficiently infiltrated into tumors with upregulation of relevant chemokine transcripts. Batf3‐positive DC and CD8+ T cells were essential for therapeutic efficacy. Furthermore, polyI:C was shown to stimulate tumor‐associated macrophages and release tumor necrosis factor alpha, which acted on tumor cells and increased sensitivity to radiation. Hence, polyI:C treatment prior to radiotherapy potentially induces tumor suppression by boosting CTL‐dependent and macrophage‐mediated anti‐tumor responses. Eventually, polyI:C and radiotherapy in combination would be a promising therapeutic strategy for radiation‐resistant tumors.

Genome-scale Modeling of NADPH Metabolism in Radiation-resistant Head and Neck Squamous Cell Carcinoma Patients

Tumor resistance to radiation therapy remains a significant obstacle to long-term cancer patient survival, especially for head and neck squamous cell carcinoma (HNSCC), a cancer type with poor long-term outcomes. NADPH metabolism is a viable target for personalized radiation-sensitizing chemotherapies due to the reliance of tumors on NADPH for DNA repair, antioxidation, and cell survival following ionizing radiation. We have previously shown that genome-scale metabolic models that incorporate transcriptomic, kinetic, thermodynamic, and metabolite concentration data can make accurate predictions of NADPH production and sensitivity to redox-cycling chemotherapeutics such as β-lapachone in radiation-sensitive and -resistant HNSCC cell lines. Through the incorporation of transcriptomic data from the Cancer Genome Atlas, we have extended our modeling approach to develop personalized flux balance analysis-based metabolic models of HNSCC patient tumors. This collection of 132 models predicts that radiation-resistant tumors display greater conversion of NADP+ to NADPH than radiation-sensitive tumors, consistent with our prior work in matched HNSCC cell lines. Differences in NADPH production are manifested by the re-routing of metabolic flux through alternate NADPH-producing pathways in the human metabolic network. In addition, simulated gene knockdown of isocitrate dehydrogenase (IDH) isoforms has a more pronounced effect on NADPH production in radiation-resistant tumors, supporting prior evidence of IDH as a promising chemotherapeutic target for multiple cancer types. Finally, we discovered a subset of radiation-sensitive patients that displayed significantly lower NADPH-producing flux throughout the metabolic network as well as greater sensitivity to knockdown of NADPH production genes. Almost all of these TCGA patients with lower fluxes had tumors of the larynx as opposed to other head and neck cancer regions, indicating that NADPH metabolism in HNSCC tumors may depend greatly on the tumor’s anatomical location. This modeling approach can be extended to investigate the synergistic action of redox-based chemotherapeutics and radiation therapy to treat radiation-resistant HNSCC patients.

Nanoformulation of Olaparib Amplifies PARP Inhibition and Sensitizes PTEN/TP53-Deficient Prostate Cancer to Radiation.

The use of PARP inhibitors in combination with radiotherapy is a promising strategy to locally enhance DNA damage in tumors. Here we show that radiation-resistant cells and tumors derived from a Pten/Trp53-deficient mouse model of advanced prostate cancer are rendered radiation sensitive following treatment with NanoOlaparib, a lipid-based injectable nanoformulation of olaparib. This enhancement in radiosensitivity is accompanied by radiation dose-dependent changes in γ-H2AX expression and is specific to NanoOlaparib alone. In animals, twice-weekly intravenous administration of NanoOlaparib results in significant tumor growth inhibition, whereas previous studies of oral olaparib as monotherapy have shown no therapeutic efficacy. When NanoOlaparib is administered prior to radiation, a single dose of radiation is sufficient to triple the median mouse survival time compared to radiation only controls. Half of mice treated with NanoOlaparib + radiation achieved a complete response over the 13-week study duration. Using ferumoxytol as a surrogate nanoparticle, MRI studies revealed that NanoOlaparib enhances the intratumoral accumulation of systemically administered nanoparticles. NanoOlaparib-treated tumors showed up to 19-fold higher nanoparticle accumulation compared to untreated and radiation-only controls, suggesting that the in vivo efficacy of NanoOlaparib may be potentiated by its ability to enhance its own accumulation. Together, these data suggest that NanoOlaparib may be a promising new strategy for enhancing the radiosensitivity of radiation-resistant tumors lacking BRCA mutations, such as those with PTEN and TP53 deletions. Mol Cancer Ther; 16(7); 1279-89. ©2017 AACR.

Subtype-Specific Radiation Response and Therapeutic Effect of FAS Death Receptor Modulation in Human Breast Cancer.

Breast cancer is the most common malignancy diagnosed among women and represents a heterogeneous group of subtypes. Radiation therapy is a critical component of treatment for breast cancer patients. However, little is known about radiation response among these intrinsic subtypes. In previous studies, we identified a significant induction of FAS after irradiation in biologically favorable breast cancer patients and breast cancer cell lines. Here, we expanded our study and investigated radiation response in a mouse model of breast cancer. MCF7 (luminal), HCC1954 (HER2+) or SUM159 (basal) cells were implanted orthotopically into the dorsal mammary fat pad of nude mice. These mice were then treated with different doses of radiation to assess tumor growth control. We further investigated the therapeutic effect of FAS modulation by silencing FAS in radiation-responsive tumors and injecting FAS agonist antibody into radiation-resistant tumors. Exposure to radiation inhibited MCF7, and to a lesser extent HCC1954 tumor growth in a dose-dependent manner. In contrast, SUM159 tumors were resistant to radiation. The estimated TCD50 values were 19.3 Gy for MCF7 and 44.9 Gy for SUM159. Radiation induced FAS expression in MCF7 tumors, but not SUM159 tumors. We found that silencing of FAS did not negatively impact radiation response in MCF7 tumors, possibly due to compensation by other apoptotic pathways. On the other hand, FAS activating antibody in combination with radiation treatment delayed SUM159 and HCC1954 tumor growth. However, it did not reach statistical significance compared to radiation treatment alone. Our results suggest that there is intrinsic variation in radiation response among breast cancer subtypes. FAS activation concurrent with radiation slows tumor growth in the radiation-resistant subtypes, but the effect was not significant. Alternative subtype-specific modulators of radiation response are under investigation.

Therapeutic benefits in grid irradiation on Tomotherapy for bulky, radiation-resistant tumors

Introduction: Spatially fractionated radiation therapy (SFRT or grid therapy) has proven to be effective in management of bulky tumors. The aim of this project is to study the therapeutic ratio (TR) of helical Tomotherapy (HT)-based grid therapy using linear–quadratic cell survival model.Material and Methods: HT-based grid (or HT-GRID) plan was generated using a patient-specific virtual grid pattern of high-dose cylindrical regions using MLCs. TR was defined as the ratio of normal tissue surviving fraction (SF) under HT-GRID irradiation to an open debulking field of an equivalent dose that result in the same tumor cell SF. TR was estimated from DVH data on ten HT-GRID patient plans with deep seated, bulky tumor. Dependence of the TR values on radiosensitivity of the tumor cells and prescription dose was analyzed.Results: The mean ± standard deviation (SD) of TR was 4.0 ± 0.7 (range: 3.1–5.5) for the 10 patients with single fraction maximum dose of 20 Gy to GTV assuming a tumor cell SF at 2 Gy (SF2t) value of 0·5. In addition, the mean ± SD of TR values for SF2t values of 0.3 and 0.7 were found to be 1 ± 0.1 and 18.0 ± 5.1, respectively. Reducing the prescription dose to 15 and 10 Gy lowered the respective TR values to 2.0 ± 0.2 and 1.2 ± 0.04 for a SF2t value of 0.5.Conclusion: HT-GRID therapy demonstrates a significant therapeutic advantage over uniform dose from an open field irradiation for the same tumor cell kill. TR increases with the radioresistance of the tumor cells and with prescription dose.

Abstract B48: Prostate cancer pre-treatment with nanoformulated Olaparib overcomes radiation resistance

Abstract Prostate cancers with PTEN deletions are promising candidates for DNA repair inhibitors such as olaparib and talazoparib. Here we show that radiation-resistant cells and tumors derived from Ptenpc-/-;Trp53pc-/- mice are rendered radiation-sensitive following pre-treatment with liposomal nanoOlaparib. This enhancement in radiosensitivity is accompanied by radiation dose-dependent changes in γ-H2AX expression and is specific to nanoformulated Olaparib alone. In animals, twice-weekly intravenous administration of nanoOlaparib alone results in significant tumor growth inhibition. When nanoOlaparib is administered prior to radiation, we find that a single dose of radiation is sufficient to increase mouse survival time by as much as 10 weeks (study duration = 13 weeks). Using ferumoxytol as a surrogate nanoparticle, magnetic resonance imaging (MRI) studies revealed that nanoOlaparib administration enhances the ability of nanoparticles to accumulate in tumors. Compared to untreated and radiation-only controls, nanoOlaparib-treated tumors showed 18-fold higher nanoparticle accumulation, suggesting that the in vivo efficacy of nanoOlaparib may be potentiated by its ability to enhance its own accumulation in tumors. Citation Format: Anne L. van de Ven, Shifalika Tangutoori, Paige Baldwin, Ju Qiao, Codi Gharagouzloo, Nina Seitzer, John Clohessy, Houari Korideck, G. Mike Makrigiorgos, Robert Cormack, Pier Paolo Pandolfi, Srinivas Sridhar. Prostate cancer pre-treatment with nanoformulated Olaparib overcomes radiation resistance. [abstract]. In: Proceedings of the AACR Special Conference on Engineering and Physical Sciences in Oncology; 2016 Jun 25-28; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2017;77(2 Suppl):Abstract nr B48.

Abstract 1647: Radiation response genome-wide analysis using paired pre and post-radiation FFPE human breast tumor samples

Abstract Background: Breast cancer is the most common female malignancy in the US, and radiotherapy is a routine part of multi-disciplinary breast cancer care. Radiation treatment (RT) tailored to target radiation response pathways could maximize treatment benefit in radiation resistant tumors, while minimizing unnecessary toxicity and cost in more radiation responsive breast tumor subtypes. Here we report on genome-wide analysis, gene expression profiles and biological pathways associated with RT response in breast cancer patients. Methods: Between 2010-2013, a total of 32 breast cancer patients were enrolled at Duke University Medical Center on an IRB approved Phase I clinical trial testing preoperative radiotherapy. Paired pre and post-RT FFPE biopsy samples were available for N = 26. Genome wide-analysis was performed using two distinct techniques: i) Microarray analysis using the Affymetrix GeneChip ® Human Transcriptome Array 2.0 (HTA 2.0); ii) RNA-Seq using TruSeq ®RNA Access Library kit (Illumina). All libraries were sequenced on the Illumina HiSeq 2000 generating 50 bp single reads at a sequencing depth of 40 million reads. The RNA-Seq data was processed using the TrimGalore toolkit. For the paired pre and post-RT differential gene expression analysis we used the linear model. Genes that had an FDR ≤ 5% in the RNA-Seq experiment were compared with all microarray probesets that had an FDR ≤ 5%. If at least one probeset that belonged to a gene in the RNA-Seq list was significant and showed the same direction of change between pre and post-RT samples, they were identified as consistent. Gene Set Enrichment Analysis (GSEA) and Database for Annotation, Visualization and Integrated Discovery (DAVID) were used to identify significant pathways and gene ontologies that were differentially regulated between the conditions. Results: 2648 genes showed the same significant results in response to RT in microarray and RNA-Seq including: i) a total of 1401 genes that had significantly higher expression levels, and ii) a total of 1247 genes that had significantly lower expression levels following RT. Principal Components Analysis (PCA) demonstrated distinct separation of pre and post-RT gene expression signatures. Differentially expressed genes were involved in major biological pathways such as cell cycle checkpoint, DNA replication and DNA repair pathways. A subset of these genes also demonstrated differential expression in radiation responsive vs. non-responsive breast cancer cell lines. Conclusion: New laboratory techniques have become available which provide the opportunity to use FFPE samples for microarray and RNA-seq analysis. Using these new techniques and our rare pre and post-RT FFPE breast tumor samples, we have been able to demonstrate distinct differences in gene expression profiles and modulation of biological pathways in response to RT in human breast tumors. Citation Format: Sharareh Siamakpour-Reihani, Wei Chen, David Corcoran, Chen-Ting Lee, Ying Zhou, Mark W. Dewhirst, Jen-Tsan A. Chi, Janet K. Horton. Radiation response genome-wide analysis using paired pre and post-radiation FFPE human breast tumor samples. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1647.

Stress Response Leading to Resistance in Glioblastoma-The Need for Innovative Radiotherapy (iRT) Concepts.

Glioblastoma (GBM) is the most common and most aggressive malignant primary brain tumor in adults. In spite of multimodal therapy concepts, consisting of surgery, radiotherapy and chemotherapy, the median survival, merely 15–18 months, is still poor. Mechanisms for resistance of GBM to radio(chemo)therapy are not fully understood yet and due to the genetic heterogeneity within the tumor including radiation-resistant tumor stem cells, there are several factors leading to therapy failure. Recent research revealed that, hypoxia during radiation and miRNAs may adversely affect the therapeutic response to radiotherapy. Further molecular alterations and prognostic markers like the DNA-repair protein O6-methylguanine-DNA methyltransferase (MGMT), anti-apoptotic molecular chaperones, and/or the activity of aldehyde dehydrogenase 1 (ALDH1) have also been identified to play a role in the sensitivity to cytostatic agents. Latest approaches in the field of radiotherapy to use particle irradiation or dose escalation strategies including modern molecular imaging, however, need further evaluation with regard to long-term outcome. In this review we focus on current information about the mechanisms and markers that mediate resistance to radio(chemo)therapy, and discuss the opportunities of Innovative Radiotherapy (iRT) concepts to improve treatment options for GBM patients.

Combined Ablation and Radiation Therapy of Spinal Metastases: A Novel Multimodality Treatment Approach

Background: Radiation therapy (RT) is the current gold standard for palliation of painful vertebral metastases. However, other percutaneous modalities such as radiofrequency ablation (RFA), cryoablation, and vertebral augmentation have also been shown to be effective in alleviating symptoms. Combined RT and ablation may be more effective than either therapy alone in palliating painful metastatic disease to the spine. Objective: To evaluate the safety and efficacy of combined ablation, either RFA or cryoablation, and RT in the treatment of spinal metastases. Study Design: Retrospective study. Setting: This is a retrospective study at a single institution. Methods: Medical records of all patients who underwent ablation of spine lesions at a single institution between March 2012 and June 2014 were reviewed; patients treated with both RT and either RFA or cryoablation concurrently were identified. Pain scores before and after RFA were measured with the numerical rating scale (NRS) (0 – 10 point scale) and compared. Procedural complications, changes in general activity level, and pain medication usage after ablation were also recorded. When available, follow-up imaging was evaluated for evidence of residual or recurrent disease. Results: Twenty-one patients with 36 spine metastases were treated with RT and percutaneous ablation concurrently; either RFA (21/22) or cryoablation (1/22). One patient received 2 separate RFA treatments. Overall, mean worst pain score (8.0, SD = 2.3) significantly decreased at both one week (4.3, SD = 3.1; P &lt; .02) and 4 weeks (2.9, SD = 3.3; P &lt; .0003). Temporary postprocedural radicular pain occurred after one RFA treatment (4.5%; 1/22). Seven patients had radiation resistant tumors (renal cell, melanoma, or sarcoma). Post-procedural imaging (median 6 months; range 2 – 27 months) showed stable treated disease in 12/13 treatments at 3 months and 10/10 at 6 months. Limitations: The therapeutic effect of vertebral augmentation versus percutaneous ablation cannot be separated in this retrospective study. Radiation treatment protocols were variable and included both stereotactic body and conventional RT which may have different safety and efficacy profiles. Conclusion: Percutaneous ablation and concurrent RT is safe and effective in palliating painful spinal metastases and can be effective in those who have radiation resistant tumor histology. Key words: Interventional spine oncology, pain, percuataneous ablation, radiofrequency ablation, cryoablation, radiation therapy, spine metastases, vertebroplasty

Abstract 3302: Subtype-specific radiation response in a mouse model of human breast cancer

Abstract Radiation therapy is an important component of multimodal treatment for women with breast cancer. However, breast radiotherapy is currently delivered uniformly, regardless of breast cancer subtype. Recent clinical data have suggested that different subtypes of breast cancer may respond differently to radiation. Understanding the intrinsic variation of radiation response in breast cancer subtypes would lay the foundation for individualized radiotherapy designed to limit toxicity in those with radiation responsive cancers. Furthermore, identification of molecular targets can be used to modulate treatment outcomes in patients with radiation resistant tumors. Our previous in vitro studies have identified an association between breast cancer subtype and gene expression profiles in response to radiation in breast tumor cell lines. Cell lines with the greatest response to radiation were luminal subtype and exhibited preferential induction of genes involved in programmed cell death, such as FAS. In this study, we investigated tumor growth and FAS induction in response to radiation in a mouse model of breast cancer. MCF7 (luminal) or SUM159 (basal) cells were implanted orthotopically into the dorsal mammary fat pad of athymic nude mice. These mice were then treated with different doses of radiation. Our results showed that radiation treatment inhibited MCF7 tumor growth in a dose-dependent manner, while radiation treatment had little effect on SUM159 tumor growth. In addition, FAS was induced in MCF7 tumors 24 hour after radiation, but there was no change in FAS expression in SUM159 tumors. However, injection of FAS-stimulating antibody intratumorally led to downstream caspase 8 and PARP activation, suggesting that the FAS signaling pathway remains intact and can be used to modulate radiation response in the resistant SUM159 cells. In conclusion, these results suggest that there is intrinsic variation in radiation response among breast cancer subtypes and that stimulation of FAS may have the potential to modulate radiation response. Citation Format: Chen-Ting Lee, Yingchun Zhou, Sharareh Siamakpour-Reihani, Kingshuk R. Choudhury, Mark W. Dewhirst, Janet K. Horton. Subtype-specific radiation response in a mouse model of human breast cancer. [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 3302. doi:10.1158/1538-7445.AM2015-3302

A 3D-microtissue-based phenotypic screening of radiation resistant tumor cells with synchronized chemotherapeutic treatment.

BackgroundRadiation resistance presents a challenge to the effective treatment of cancer. If therapeutic compounds were capable of resensitizing resistant tumours then a concurrent chemo-radiation treatment could be used to overcome radiation resistance.MethodsWe have developed a phenotypic assay to investigate the response of radiation resistant breast cancer cells grown in 3D-microtissue spheroids to combinations of radiation and established chemotherapeutic drugs. The effects were quantified by real time high content imaging of GFP detection area over 14 days. Ten established chemotherapeutic drugs were tested for their ability to enhance the effects of radiation.ResultsOf ten analysed chemotherapeutics, vinblastine was the most effective compound, with docetaxel and doxorubicine being less effective in combination with radiation. To investigate the response in a model closer to the in vivo situation we investigated the response of heterotypic 3D microtissues containing both fibroblasts and breast cancer cells. Drug treatment of these heterotypic 3D cultures confirmed treatment with radiation plus vinblastine to be additive in causing breast cancer growth inhibition. We have validated the screen by comparing radiation sensitizing effects of known chemotherapeutic agents. In both monotypic and heterotypic models the concurrent treatment of vinblastine and radiation proved more effective inhibitors of mammary cancer cell growth. The effective concentration range of both vinblastine and radiation are within the range used in treatment, suggesting the 3D model will offer a highly relevant screen for novel compounds.ConclusionsFor the first time comfortable 3D cell-based phenotypic assay is available, that allows high throughput screening of compounds with radiation therapy modulating capacity, opening the field to drug discovery.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-015-1481-9) contains supplementary material, which is available to authorized users.

Carbon-ion cancer therapy shows promise

Radiation-resistant tumors are targets for heavy-ion particles. But high capital costs have prevented construction of treatment facilities in the US.

Analysis of DNA methylation and gene expression in radiation-resistant head and neck tumors

Resistance to radiation therapy constitutes a significant challenge in the treatment of head and neck squamous cell cancer (HNSCC). Alteration in DNA methylation is thought to play a role in this resistance. Here, we analyzed DNA methylation changes in a matched model of radiation resistance for HNSCC using the Illumina HumanMethylation450 BeadChip. Our results show that compared to radiation-sensitive cells (SCC-61), radiation-resistant cells (rSCC-61) had a significant increase in DNA methylation. After combining these results with microarray gene expression data, we identified 84 differentially methylated and expressed genes between these 2 cell lines. Ingenuity Pathway Analysis revealed ILK signaling, glucocorticoid receptor signaling, fatty acid α-oxidation, and cell cycle regulation as top canonical pathways associated with radiation resistance. Validation studies focused on CCND2, a protein involved in cell cycle regulation, which was identified as hypermethylated in the promoter region and downregulated in rSCC-61 relative to SCC-61 cells. Treatment of rSCC-61 and SCC-61 with the DNA hypomethylating agent 5-aza-2'deoxycitidine increased CCND2 levels only in rSCC-61 cells, while treatment with the control reagent cytosine arabinoside did not influence the expression of this gene. Further analysis of HNSCC data from The Cancer Genome Atlas found increased methylation in radiation-resistant tumors, consistent with the cell culture data. Our findings point to global DNA methylation status as a biomarker of radiation resistance in HNSCC, and suggest a need for targeted manipulation of DNA methylation to increase radiation response in HNSCC.

Risk factors associated with secondary enucleation after fractionated stereotactic radiotherapy in uveal melanoma.

To evaluate risk factors for secondary enucleation after fractionated stereotactic radiotherapy (fSRT) in uveal melanoma. In this retrospective study, clinical data of 118 consecutive patients who had initially been treated with fSRT between 1999 and 2009 were collected and analysed. The patients who had undergone secondary enucleation were identified and examined for clinical, histopathological and cytogenetical (fluorescence in situ hybridization determined) data. Also, the reasons for secondary enucleation, such as treatment failure (progressive tumour growth or tumour recurrence) or complications following fSRT (painful blind eye), were recorded and examined. The secondary enucleation rate was 16% after a median follow-up of 4.7 years, with 5% due to treatment failure and 11% due to complications. In the univariate analysis, large tumour diameter (p = 0.019) and large tumour height (p = 0.001) were associated with secondary enucleation, tumour involvement of the optic disc showed borderline significance (p = 0.068). Cox regression multivariate analysis displayed large tumour height as independent prognostic factor (HR 1.42, 95% CI 1.12-1.81, p = 0.004). Following secondary enucleation, mitotic figures were present in five of 18 tumours, and gain of chromosome 8q was also present in five tumours. Within the subgroup of patients who required secondary enucleation due to failed tumour control by fSRT (N = 6), mitotic figures were present in four of six tumours while gain of 8q was present in three of six tumours. Secondary enucleation after previous fSRT was associated with large tumour height. High mitotic counts and gain of chromosome 8q were frequently found in secondary enucleations and possibly indicate a more aggressive or radiation-resistant tumour.