Cancer Patients Receive Radiation Therapy Research Articles

Abstract LB181: First disclosure of XRD-0394, a novel dual ATM/DNA-PK inhibitor, that potently radiosensitizes and potentiates PARP and topoisomerase inhibitors

Abstract A majority of cancer patients receive radiation therapy (RT) as part of their treatment regimens, whether using external beam therapy or locally-delivered radioisotopes. While often effective, RT may not be efficacious for some tumors while exerting significant short-term and long-term toxicities. Thus, enhancing therapeutic effectiveness of radiation therapy remains an important goal. ATM (ataxia-telangiectasia, mutated) and DNA-PKcs (deoxyribonucleic acid [DNA]-dependent protein kinase, catalytic subunit) are related protein kinases and both are critical regulators of cellular responses to ionizing radiation. We report here the identification and initial characterization of XRD-0394, a potent, specific dual inhibitor of both ATM and DNA-PKcs, whose chemical structure will be disclosed. A dual ATM/DNA-PK inhibitor has practical and theoretical advantages over compounds which inhibit just one of these kinases: 1) blunting both DNA damage response (DDR) pathways enhances radiation-induced tumor cell kill compared to single target inhibition; and 2) simultaneous inhibition of two DDR pathways should overcome intrinsic or acquired resistance of tumor cells to either target alone. Notably, transient inhibition of both kinases by XRD-0394 has little adverse effects on cells in the absence of irradiation. XRD-0394 is orally bioavailable, with excellent pharmacological profiles, demonstrating significant in vitro and in vivo sensitizing activity in combination with ionizing radiation and in combination with immunotherapy and radiation. In addition, a CRISPR screen identified alterations in the Fanconi A/BRCA pathway as an opportunity for synthetic lethality in tumor cells exposed to XRD-0394, an insight that was validated in multiple tumor cell types. In vitro studies demonstrated synergy of XRD-0394 in combination with PARP inhibitors, particularly in BRCA-mutant cells. XRD-0394 also potentiates the effectiveness of topoisomerase inhibitors in vitro. Single doses of XRD-0394 were well-tolerated in combination with palliative RT in subjects with advanced cancer in a Phase Ia clinical trial (NCT05002140). No DLTs were observed. At a dose of 160 mg, plasma concentrations were well above the preclinical target plasma level of 530 ng/mL (1 µM) for up to 15 h and inhibition of ATM kinase activity was demonstrated by inhibition of radiation-induced pKAP1 in tumor tissue. Importantly, this concentration of drug is sufficient to induce potent radiosensitization in numerous preclinical models. The median tmax (2.3 h) and mean terminal t½ (11.1 h) at the 160 mg dose in subjects support coadministration of XRD-0394 and RT within a clinically feasible time frame. These results provide a rationale for future clinical trials with XRD-0394 in combination with RT, RT and immunotherapy, PARP inhibitors and targeted delivery of topoisomerase inhibitors. Citation Format: Tona M. Gilmer, Chun-Hsiang Lai, Kexiao Guo, Katherine Deland, Kathleen A. Ashcraft, Amy E. Stewart, Yaode Wang, Jianmin Fu, Kris C. Wood, Deborah A. Smith, Jonathan T. Yang, Christopher T. Chen, Michael F. Gensheimer, Paul B. Romesser, Steven H. Lin, David G. Kirsch, Michael B. Kastan. First disclosure of XRD-0394, a novel dual ATM/DNA-PK inhibitor, that potently radiosensitizes and potentiates PARP and topoisomerase inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB181.

INDIVIDUAL ARTICLE: NECOM 3: A Practical Algorithm for the Management of Radiation Therapy-Related Acute Radiation Dermatitis.

In the Nordic European countries in 2020, cancer diagnoses accounted for 175,925 patients. About 50% of cancer patients receive radiation therapy (RT), which may lead to radiation dermatitis (RD). Notably, patients with breast, head, neck, and anal cancers may be prone to developing RD. However, few algorithms exist for the prevention and treatment of RD. The Nordic European Cutaneous Oncodermatology Management (NECOM) project aims to improve cancer patient outcomes by offering tools to prevent and treat cancer therapy-related cutaneous adverse events (cAEs). The first 2 NECOM papers presented various cAEs and skincare regimens involving hygiene, moisturization, sun protection, and camouflage products for preventing and managing cAEs. The NECOM 3 practical algorithm for preventing and managing acute RD (ARD) is intended to promote healthy skin and reduce RT-related ARD, improving cancer patient outcomes.  Results: The NECOM advisors discussed the results of a systematic literature review and obtained consensus on the evidence and opinion-based practical algorithm for ARD to support all stakeholders in the Nordic European healthcare setting. The algorithm starts with skin-preserving therapy, followed by skin condition assessment and patient-specific interventions based on the grade of RD present.  Conclusion: ARD may lead to symptoms of pruritus and pain, decreased QoL and morbidity, and treatment interruptions. Patient education on the prevention of RD and treatment recommendations given in the NECOM 3 algorithm may help prevent and manage RD and improve the overall care of patients receiving RT. J Drugs Dermatol. 2023;22:11(Suppl 2):s3-s10.

A review of bismuth-based nanoparticles and their applications in radiosensitising and dose enhancement for cancer radiation therapy.

About 50% of cancer patients receive radiation therapy. Despite the therapeutic benefits of this method, the toxicity of radiation in the normal tissues is unavoidable To improve the quality of radiation therapy, in addition to other methods such as IMRT, IGRT, and high radiation dose, nanoparticles have shown excellent potential when ionising radiation is applied to the target volume. Recently, bismuth-based nanoparticles (BiNPs) have become particularly popular in radiation therapy due to their high atomic numbers (Z), high X-ray attenuation coefficient, low toxicity, and low cost. Moreover, it is easy to synthesise in a variety of sizes and shapes. This study aimed to review the effects of the bismuth-based NP and its combination with other compounds, and their potential synergies in radiotherapy, discussed based on their physical, chemical, and biological interactions. Targeted and non-targeted bismuth-based NPs used in radiotherapy as radiosensitizers and dose enhancement effects are described. The results reported in the literature were categorised into various groups. Also, this review has highlighted theimportance of bismuth-based NPs in different forms of cancer treatment to find the highest efficiency for applying them as a suitable candidate for various cancer therapy and future clinical applications.

Abstract 3209: Metabolic characterization of radiation-induced cardiotoxicity

Abstract Background: Approximately 50% of all cancer patients receive radiation therapy as a component of their cancer care. While radiation therapy has demonstrable benefit in improving survival in patients, radiation-induced heart disease (RIHD) is a major contributor to morbidity and mortality in cancer survivors with history of thoracic radiation. Understanding metabolic changes underlying RIHD may enable development of novel diagnostic and therapeutic approaches for early detection and treatment of RIHD. The high energetic demands of the heart require properly functioning mitochondria to meet the ATP production needs. Fatty acids are the primary metabolic substrates for energy production in a healthy heart. However, under conditions of stress, the cardiac metabolism shifts towards increased glucose utilization. In this study, we characterize the impact of radiation of cardiac substrate utilization and energy production. Methods: Pre-clinical RIHD models were established by administering whole heart radiation (8Gy x 5) in mice and rats followed by structural and biochemical characterization. Transmission electron microscopy and western blot analyses were used to characterize structural and biochemical changes in the heart in response to radiation. Spectrophotometric assays and Western blot analyses were used to characterize changes in pyruvate dehydrogenase (PDH) activity and function in the heart in response to radiation. Results: Our studies identified myocardial mitochondrial dysfunction as an early event following exposure of heart to radiation. Cardiac irradiation resulted in increased mitochondrial fusion and higher expression of MFN1, a key protein that mediates mitochondrial fusion. The pathological structural and biochemical changes in the myocardial mitochondria are associated with reduced glucose metabolism due to impaired PDH activity. This decline was mediated by increased phosphorylation of PDH in irradiated hearts, which inhibits its activity. Conclusion: Cardiac irradiation results in early metabolic dysregulation, especially in glucose metabolism, which may be exploited for early detection and mitigation of radiation-induced cardiotoxicity. Citation Format: Sarah C. Elliott, Jayesh Sharma, Elizabeth R. Zhang-Velten, Abdallah Elnwasany, Chantal Vidal, Luke Szweda, Prasanna Alluri. Metabolic characterization of radiation-induced cardiotoxicity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3209.

Application of individualized multimodal radiotherapy combined with immunotherapy in metastatic tumors.

Radiotherapy is one of the mainstays of cancer treatment. More than half of cancer patients receive radiation therapy. In addition to the well-known direct tumoricidal effect, radiotherapy has immunomodulatory properties. When combined with immunotherapy, radiotherapy, especially high-dose radiotherapy (HDRT), exert superior systemic effects on distal and unirradiated tumors, which is called abscopal effect. However, these effects are not always effective for cancer patients. Therefore, many studies have focused on exploring the optimized radiotherapy regimens to further enhance the antitumor immunity of HDRT and reduce its immunosuppressive effect. Several studies have shown that low-dose radiotherapy (LDRT) can effectively reprogram the tumor microenvironment, thereby potentially overcoming the immunosuppressive stroma induced by HDRT. However, bridging the gap between preclinical commitment and effective clinical delivery is challenging. In this review, we summarized the existing studies supporting the combined use of HDRT and LDRT to synergistically enhance antitumor immunity, and provided ideas for the individualized clinical application of multimodal radiotherapy (HDRT+LDRT) combined with immunotherapy.

Adipose-Derived Stromal Cell-Based Therapies for Radiation-Induced Fibrosis.

Significance: Half of all cancer patients receive radiation therapy as a component of their treatment regimen, and the most common resulting complication is radiation-induced fibrosis (RIF) of the skin and soft tissue. This thickening of the dermis paired with decreased vascularity results in functional limitations and esthetic concerns and poses unique challenges when considering surgical exploration or reconstruction. Existing therapeutic options for RIF of the skin are limited both in scope and efficacy. Cell-based therapies have emerged as a promising means of utilizing regenerative cell populations to improve both functional and esthetic outcomes, and even as prophylaxis for RIF. Recent Advances: As one of the leading areas of cell-based therapy research, adipose-derived stromal cells (ADSCs) demonstrate significant therapeutic potential in the treatment of RIF. The introduction of the ADSC-augmented fat graft has shown clinical utility. Recent research dedicated to characterizing specific ADSC subpopulations points toward further granularity in understanding of the mechanisms driving the well-established clinical outcomes seen with fat grafting therapy. Critical Issues: Various animal models of RIF demonstrated improved clinical outcomes following treatment with cell-based therapies, but the cellular and molecular basis underlying these effects remains poorly understood. Future Directions: Recent literature has focused on improving the efficacy of cell-based therapies, most notably through (1) augmentation of fat grafts with platelet-rich plasma and (2) the modification of expressed RNA through epitranscriptomics. For the latter, new and promising gene targets continue to be identified which have the potential to reverse the effects of fibrosis by increasing angiogenesis, decreasing inflammation, and promoting adipogenesis.

Modeling Patient-Reported Swallowing Outcomes With Dose to the Epiglottis

Swallowing is a complex physiologic function and care is needed for its preservation when head and neck (HN) cancer patients receive radiation therapy. The larynx, and especially the epiglottis, is one involved organ. This study's purpose was to investigate whether radiation dose to the epiglottis is more predictive of acute swallowing toxicity than dose to the rest of the larynx or the total larynx.A cohort of 91 HN patients with no prior HN radiation treated at a single institution form 2013-2020 with either protons or photons was studied retrospectively. Patients were selected based on primary-site diagnosis code (nasopharynx, oropharynx, tonsil, and base of tongue) and prescription dose (≥60 Gy). Swallowing outcomes were assessed with patient-reported outcomes (PROs), using the EORTC QLQ H&N35 survey, that were collected prior to (baseline) and following treatment (within 2 weeks of finishing). The post-treatment swallowing-specific PRO scores were used to evaluate acute swallowing toxicity, and patients were stratified into those with high (score > 50) and low (score≤50) responses. The epiglottis, the arytenoid cartilages, and the non-epiglottic larynx were contoured by a single individual (SA); the three substructures were then combined for a total larynx structure. 16 patients with either a larynx disfigured by their disease or high baseline swallowing score were removed from the analysis. A univariate analysis was first performed using a Wilcoxon rank-sum test on the mean doses to the epiglottis, total larynx, and non-epiglottic larynx structures. Next, a random-forest (RF) machine-learning model was trained using 29 patient-specific features with demographic and clinical information (including primary site, chemotherapy, smoking, bi-/unilateral, and HPV/p16), baseline PRO scores, and dose metrics to the total larynx and epiglottis. The model was trained on a 60-patient training set using nested 10-fold cross-validation and then assessed on a 15-patient test set using the area under the receiver-operator curve (AUC).The univariate analyses for the total and non-epiglottic larynx mean doses showed no statistical differences between the two groups (P = 0.56 and 0.86, respectively). That of the epiglottic mean dose, however, showed a significant difference (P = 0.026) with 39.2 [32.7-52.9] Gy and 47.2 [41.1-57.2] Gy for the low- and high-response groups, respectively. The RF had AUC = 0.71 ± 0.22 and 0.70 on the training and test sets, respectively, with the epiglottis volume receiving 30 Gy identified as the most important feature.The univariate analysis and RF model indicate that the dose to the epiglottis is more sensitive for predicting patient-reported acute swallowing toxicity than either the doses to the rest of the larynx or the full larynx. These results suggest that consideration be given to the epiglottic dose during treatment planning.

Abstract 1558: Radiation therapy and immune checkpoint inhibitor combinations in the E0771 medullary breast adenocarcinoma

Abstract Greater than 50% of all cancer patients receive radiation therapy at some point during their cancer treatment to control solid tumor growth (Harrington 2011). In addition to the direct action of radiation on tumor cell proliferation, radiation also has the potential to stimulate an anti-tumor immune response (Weichselbaum 2017). The success of immune checkpoint therapies such as anti-PD-1, anti-PD-L1, and anti-CTLA-4 inhibitory antibodies has driven large investment into the discovery of novel immune-oncology therapies. While the clinical response to immune checkpoint inhibitors can be profound for those patients that respond, there still exists a large percentage of patients that do not see benefit. In order to expand the number of patients that may respond to immune checkpoint inhibition, combination with radiation therapy needs to be tested and in fact a large number of preclinical and clinical studies are being conducted (for review see Asna 2019). Preclinical syngeneic tumor models are a critical means to assess new immunotherapies and drive preclinical programs. E0771 is a medullary breast adenocarcinoma cell line originally isolated from a spontaneous tumor and can be implanted subcutaneously in C57BL/6 mice (Ewens 2005). In order to characterize the E0771 syngeneic breast tumor model for future studies with radiation and immunotherapy, we assessed the efficacy changes in response to various schedules of radiation doses with and without either anti-PD-1 or anti-CTLA-4 antibody therapies. In addition, we analyzed the tumor infiltrating immune cell populations following radiation therapy. E0771 is sensitive to radiation therapy with a clear dose response. Radiation administered either as a single dose, hypofractionated, or hyperfractionated gave similar tumor responses. Flow cytometry analysis shows a higher infiltration of T regulatory cells compared with CD8+ T cells at baseline, which is exacerbated by irradiation. The CD8/Treg ratio is reversed with the addition of anti-CTLA-4 treatment to radiation and resulted in curative responses for 9 of 10 mice in the combination group. Citation Format: Patrick Fadden, Thi Bui, Kelli Davis, David Hurtado, Emily Sugg, Abigail Svancarek, Ian Belle, Chassidy Hall. Radiation therapy and immune checkpoint inhibitor combinations in the E0771 medullary breast adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1558.

Cardiac Magnetic Resonance for Early Detection of Radiation Therapy-Induced Cardiotoxicity in a Small Animal Model

BackgroundOver one-half of all cancer patients receive radiation therapy (RT). However, radiation exposure to the heart can cause cardiotoxicity. Nevertheless, there is a paucity of data on RT-induced cardiac damage, with limited understanding of safe regional RT doses, early detection, prevention, and management. A common initial feature of cardiotoxicity is asymptomatic dysfunction, which, if left untreated, may progress to heart failure. The current paradigm for cardiotoxicity detection and management relies primarily upon assessment of ejection fraction. However, cardiac injury can occur without a clear change in ejection fraction. ObjectivesWe sought to identify cardiac magnetic resonance (CMR) imaging markers of early RT-induced cardiac dysfunction. MethodsWe investigated the effect of RT on global and regional cardiac function and myocardial T1/T2 values at 2 time points post-RT using CMR in a rat model of localized cardiac RT. Rats who received image-guided whole-heart radiation of 24 Gy were compared with sham-treated rats. ResultsThe rats maintained normal global cardiac function post-RT. However, a deterioration in strain was particularly notable at 10 weeks post-RT, and changes in circumferential strain were larger than changes in radial or longitudinal strain. Compared with sham treatment, circumferential strain changes occurred at the basal, mid-ventricular, and apical levels (p < 0.05 for all at both 8 weeks and 10 weeks post-RT), most of the radial strain changes occurred at the mid-ventricular (p = 0.044 at 8 weeks post-RT) and basal (p = 0.018 at 10 weeks post-RT) levels, and most of the longitudinal strain changes occurred at the apical (p = 0.002 at 8 weeks post-RT) and basal (p = 0.035 at 10 weeks post-RT) levels. Regionally, lateral myocardial segments showed the greatest worsening in strain measurements, and histological changes supported these findings. Despite worsened myocardial strain post-RT, myocardial tissue displacement measures were maintained, or even increased. T1/T2 measurements showed small nonsignificant changes post-RT compared with values in nonirradiated rats. ConclusionsOur findings suggest MRI regional myocardial strain is a sensitive imaging biomarker for detecting RT-induced subclinical cardiac dysfunction before compromise of global cardiac function.

Supporting Patients Through Their Radiation Therapy: Lung Cancer, Brain Metastases, and Bone Metastases (FR406)

•Describe common evidence-based indications for radiation therapy for lung cancer, brain metastases, and bone metastases.•Identify common acute and late adverse effects associated with radiation therapy for lung cancer, brain metastases, and bone metastases, and describe ways to mitigate them.•Recognize opportunities for integrating palliative medicine into the care of patients receiving radiation therapy. Approximately 60% of cancer patients receive radiation therapy during the course of their illness, and nearly half of all patients referred to radiation oncology are treated with palliative intent. However, many palliative care specialists are unfamiliar with the indications, expected outcomes, and toxicities of radiation therapy. Palliative care providers can benefit from a greater understanding of how to support patients and their families through this process. This session will follow a patient with lung cancer from the time of diagnosis, through curative-intent treatment and subsequent recurrence with brain and bone metastases, to death. A multidisciplinary panel will discuss the indications for and adverse effects of radiation therapy at each stage of the patient's illness. We will highlight key points regarding palliative radiation therapy for brain and bone metastases. As palliative care continues to move upstream in the cancer trajectory, it is essential that palliative care providers understand the important role of both definitive and palliative radiation therapy and are comfortable with managing the acute and late side effects of treatment. This session will reinforce what hospice and palliative medicine providers need to know when caring for patients receiving radiation therapy and will highlight ways to advance the integration of radiation oncology and palliative care.

Risk of subsequent cancer diagnosis in patients treated with 3D conformal, intensity modulated, or proton beam radiation therapy.

1503 Background: Approximately half of cancer patients receive radiation therapy (RT). Modern RT modalities (3D conformal [3DCRT], intensity modulated [IMRT], proton beam [PBRT]) have been theorized to pose different risks of second cancers, but the relationship between RT modality and subsequent cancers has been unclear due to their rarity. Methods: Pediatric and adult patients with a first cancer diagnosis who received 3DCRT, IMRT, or PBRT were identified in the National Cancer Database. To analyze a more uniform population, cases were required to be non-metastatic and have at least 2 years of follow-up time. Ten cancer types were included: head/neck, upper gastrointestinal (GI), lower GI, gynecological, lymphoma, non-small cell lung, prostate, breast, bone/soft tissue, and brain/central nervous system. Diagnosis of a subsequent cancer was determined using a variable denoting the sequence of malignant neoplasms over the lifetime of the patient. The risk of subsequent cancer diagnosis was modeled using multivariable logistic regression adjusting for age, follow-up time, cancer type, RT dose, chemotherapy, and other factors. Propensity score matching was additionally used to balance baseline characteristics. Results: In total, 430,866 patients were included (33.4% 3DCRT, 65.1% IMRT, 1.5% PBRT) with median follow-up of 5.0 years and total follow-up period of 2.35 million person-years. In the comparison of IMRT relative to 3DCRT, there was no difference in the risk of subsequent cancer diagnosis (adjusted odds ratio [OR] 1.01; 95% confidence interval [CI] 0.98-1.03; p = 0.62). In contrast, recipients of PBRT had significantly lower risk of subsequent cancer diagnosis relative to IMRT (adjusted OR 0.31; 95% CI 0.26-0.37; p &lt; 0.0001). The benefit associated with PBRT persisted in sensitivity analyses that excluded patients with prostate cancer (71.6% of the PBRT cases), receipt of chemotherapy, and/or follow-up time less than 5 years. Conclusions: Risk of subsequent cancer diagnosis was similar between IMRT and 3DCRT and significantly lower for PBRT. PBRT may be preferred in situations where avoidance of second cancers is paramount, such as pediatrics and young adults.

Photoacoustic tomography in a clinical linear accelerator for quantitative radiation dosimetry

Cancer is the second leading cause of death in the United States. Approximately half of all cancer patients receive radiation therapy, in which linear accelerators are used to deliver high doses of x-ray radiation to tumors, inducing cell death. X-ray energy deposition causes pressure changes that produce acoustic signals due to the photoacoustic effect. Here, clinical x-ray beams were directed at test objects made of antimonial lead and other metallic materials within a water tank. Photoacoustic signals were measured using a calibrated broadband hydrophone and validated using simulations in k-Wave. Linear and two-dimensional synthetic apertures were formed by mechanically scanning the x-ray source and test object within a single plane. Tomographic images of test objects, reconstructed from measured photoacoustic signals, show good agreement with object geometry. X-ray doses incurred by the test objects are mapped based on the reconstructed acoustic pressure sources and Gruneisen parameter of the material employed. Potential applications to in vivo dosimetry for x-ray and proton therapy, potentially enabling safer and more effective treatments, are discussed.Cancer is the second leading cause of death in the United States. Approximately half of all cancer patients receive radiation therapy, in which linear accelerators are used to deliver high doses of x-ray radiation to tumors, inducing cell death. X-ray energy deposition causes pressure changes that produce acoustic signals due to the photoacoustic effect. Here, clinical x-ray beams were directed at test objects made of antimonial lead and other metallic materials within a water tank. Photoacoustic signals were measured using a calibrated broadband hydrophone and validated using simulations in k-Wave. Linear and two-dimensional synthetic apertures were formed by mechanically scanning the x-ray source and test object within a single plane. Tomographic images of test objects, reconstructed from measured photoacoustic signals, show good agreement with object geometry. X-ray doses incurred by the test objects are mapped based on the reconstructed acoustic pressure sources and Gruneisen parameter of the material...

3506 PRMT5 is a novel therapeutic target to enhance radiation therapy for cancer treatment

OBJECTIVES/SPECIFIC AIMS: Prostate cancer is the second leading cause of cancer-related death among men in the U.S. and over half of all prostate cancer patients receive radiation therapy (RT). RT induces double-strand breaks (DSBs) in DNA which are lethal to cells if not repaired. While potentially curative, 10% of low-risk patients and 50% of high-risk patients treated with RT still experience tumor recurrence. Thus, identification of novel therapeutic targets to enhance RT will likely reduce prostate cancer mortality. The only clinical approach to enhance RT is androgen deprivation therapy, which targets androgen receptor (AR) signaling; however, its use is limited due to systemic side effects. We recently reported that PRMT5 epigenetically activates AR which led us to investigate if targeting PRMT5 sensitizes prostate cancer to RT. The goal of this project is to determine if PRMT5 is a therapeutic target for prostate cancer radiosensitization and analyze its mechanistic role in response to radiation. METHODS/STUDY POPULATION: To evaluate if targeting PRMT5 may sensitize prostate cancer cells to radiation, we performed a clonogenic assay of irradiated cells. To determine if PRMT5 is required for repair of radiation-induced DSBs, we performed foci analysis via immunocytochemistry. We then used RNA-seq, qPCR, western blot, and ChIP to evaluate a potential epigenetic role of PRMT5 in activating the expression of genes critical to DSB repair. To extend our findings, we analyzed clinical data from around 18,000 of cancer patients encompassing 43 cancer types to assess if PRMT5 expression correlates with the expression of its putative target genes. RESULTS/ANTICIPATED RESULTS: Targeting PRMT5 sensitizes prostate cancer cells to radiation independently of AR status. RNA-seq analysis revealed putative PRMT5 target genes including several involved in DSB repair and G2 arrest. Mechanistically, PRMT5 functions as a master epigenetic activator of DNA damage response (DDR) genes: PRMT5 maintains the basal expression of several DDR genes including BRCA1, BRCA2, and RAD51 and is recruited upon radiation to DDR gene promoters to activate their expression via histone methylation. Targeting PRMT5 decreases expression of these genes at the protein level and hinders repair of radiation-induced DSBs in multiple cancer and non-cancer cell types. Clinically, PRMT5 expression positively correlates with the expression of these DDR genes across all 43 cancer types analyzed. DISCUSSION/SIGNIFICANCE OF IMPACT: PRMT5 acts as a master epigenetic activator of genes involved in DDR and is critical for cells to survive radiation treatment. Importantly, PRMT5 epigenetically activates multiple genes that encode for well-characterized core repair proteins involved in HR (RAD51, RAD51AP1, RAD51D, BRCA1 and BRCA2) and NHEJ (NHEJ1, Ku80, XRCC4, and DNAPKcs), which may explain why PRMT5 is essential to repair IR-induced DSBs in several cell lines. As PRMT5 is overexpressed in many human cancers and its overexpression correlates with poor prognosis, our findings suggest that more efficient DSB repair via PRMT5 overexpression in these cancers may confer survival advantages particularly following DNA damaging treatments. Lastly, because targeting DSB repair is a clinically validated therapeutic approach for cancer treatment, our findings also suggest that PRMT5 targeting may be explored as a monotherapy or in combination therapy with radiation therapy or chemotherapy for cancer treatment.

Abstract 861: Angiopoietin-2 blocking antibodies improve tumor growth inhibition and survival in mice treated with low doses of radiation

Abstract Almost 50 % of all cancer patients receive radiation therapy during their treatment, yet several tumor types show radiation therapy resistance that compromises treatment efficacy. Many radiation sensitizers have been tested for improvement of the outcome of radiation therapy. For example, inhibitors of VEGF and VEGF receptors were tested in attempt to normalize the tumor vasculature and to improve the outcome of radiation therapy. Here, we have analysed if antibodies blocking the angiogenic factor angiopoietin-2 could improve radiation therapy of mouse tumor isografts and human tumor xenografts in mice. To test if the anti-tumor effect of small doses of radiation can be increased by Ang2 blocking antibodies, we analysed the radiation sensitivity of subcutaneous tumor isografts in C57bl/6JRj mice, and human xenografts in NOD scid gamma mice. In several models, the combination treatment with anti-Ang2 plus radiation was superior to the monotherapies in decreasing tumor growth and increasing the lifespan of the tumor-bearing mice both in immunocompetent and immunocompromised mice. Based on our results, the anti-Ang2 blocking antibody treatment could be tested in the clinics to improve the effect of radiation therapy, especially in those cases in which an optimal radiation dose cannot be given because of the radiation sensitivity of the surrounding tissues. Citation Format: Pauliina Kallio, Elina Jokinen, Suvendu Das, Jenny Högström, Sarika Heino, Marianne Lähde, Kari Alitalo. Angiopoietin-2 blocking antibodies improve tumor growth inhibition and survival in mice treated with low doses of radiation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 861.

Abstract 3710: Nanoparticle-mediated concomitant radiation dose amplification and PARP inhibition in lung cancer

Abstract Introduction: More than 50% of cancer patients receive radiation therapy at some point during their care. Gold nanoparticles (GNPs) can amplify the radiation dose by facilitating the ejection of low-energy photoelectrons, resulting in increased DNA damage. One of the main challenges of radiation therapy in cancer is to sustain this damage for longer durations. DNA single-strand breaks (SSBs) are repaired by base excision repair, which utilizes Poly(ADP-ribose) polymerase (PARP). PARP inhibition during radiotherapy provides an attractive alternative in maximizing treatment outcomes. Here, we explore a strategy to combine the radiosensitizing effect of GNPs with the DNA-repair inhibiting ability of NanoTalazoparib (nTLZ), a liposomal formulation of the PARP inhibitor, talazoparib (TLZ). Methods: GNPs were synthesized by reducing AuCl4 using Tetrakis(hydroxymethyl)phosphonium chloride and further PEGylating using heterobifunctional PEGs. A liposomal formulation of TLZ was synthesized using the Nanoassemblr, a microfluidics-based device. Physicochemical characterization of GNPs and nTLZ was carried out using TEM, DLS and release kinetics studies. In vitro studies were carried out to assess the toxicity of the GNPs using MTT assay in non-small cell lung cancer (NSCLC) cell line Calu-6. The therapeutic efficacy of combination treatment using GNPs, nTLZ and radiation was done using clonogenic survival assays. Clonogenic assay was carried out using Calu 6 cells, which were sequentially treated with GNPs (1mg/mL), TLZ (0.5 uM) and nTLZ (0.5 uM) with and without radiation. The radiation doses varied from 0-10Gy for each set of treatments. Results: PEGylated GNP's showed a hydrodynamic diameter of ~10-12 nm with a spherical morphology whereas nTLZ size was 70 nm encapsulating TLZ at a concentration of ~200 ug/ml. MTT assay showed no toxicity for PEGylated GNPs treated upto a concentration of 3.0 mg/mL. Cells treated with either GNPs, TLZ or nTLZ did not show significant reduction in colony formation, but were reduced with increasing doses of radiation. The survival plots showed a highly additive antiproliferative effect for the GNP + nTLZ combination at all radiation doses, while the free TLZ + GNPs combination was not as effective at inhibiting colony formation. In vivo experiments assessing the combination therapy in a subcutaneous xenograft mice model using Calu 6 are currently under way. Conclusions: The preliminary in vitro results indicate that the combination of radiosensitizing GNPs with a potent DNA repair enzyme inhibitor, TLZ, has an immense potential as a complimentary combination therapy in conjunction with radiation therapy in treatment of lung cancer. This work is supported by the CaNCURE program (grant #1CA174650-02), American Lung Association, Dana-Farber Cancer Institute and Brigham and Women's Hospital. Citation Format: Ana G. Vazquez-Pagan, Paige Baldwin, Ravina M. Ashtaputre, Sijumon Kunjachan, Srinivas Sridhar, Rajiv Kumar, Ross Berbeco. Nanoparticle-mediated concomitant radiation dose amplification and PARP inhibition in lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3710.

Abstract 2933: Synergistic antitumor effect of ONC201 in combination with radiation therapy

Abstract Radiation therapy is used as the main treatment when surgery is not feasible, before/after surgery, and to palliate symptoms in advanced stage. About 50% of cancer patients receive radiation therapy. 40% of the cure is achieved by radiation therapy. First-in-class small-molecule imipridone ONC201 can cause dual inactivation of ERK and AKT and induce an integrated stress response, proapoptotic TRAIL receptor DR5 activation, cancer stem cell depletion, and cell cycle arrest. ONC201 could synergize with radiation therapy because of its proapoptotic and antimetastasis effects. We tested this hypothesis in colorectal cancer, non-small cell lung cancer and glioblastoma cell lines (HCT116, RKO, LS513, H460, A549 and SNB19). Firstly, CellTiter-Glo® luminescent cell viability assays were performed with single treatment or combination of radiation therapy (0 to 4 Gy) and ONC201 (0 to 20 μM). For combination treatment, cancer cells were pretreated with ONC201 for 24 hours followed by radiation therapy. Next, colony formation assays with single treatment or combination were used to evaluate the effective dose range from cell viability assays. Flow cytometry and Western blot analysis were used for determination of apoptosis. We observed synergism between ONC201 and radiation therapy in several colorectal cancer, non-small cell lung cancer and glioblastoma cell lines. Combination indices are 0.53, 0.59 and 0.68 when non-small cell lung cancer cell line H460 was treated with ONC201 at 5 μM and radiation therapy at 1, 2 and 4 Gy. We are currently pursuing this promising combinational therapy in vivo, using the H460 xenograft model and potential syngeneic lung tumor models with wild-type p53. We plan to pursue the mechanism of this combination from in vivo samples. Our results indicate that the combination of radiation therapy and ONC201 could be an important approach in the application of ONC201 in clinical practice. Citation Format: Lanlan Zhou, Jessica Wagner, Wafik S. El-Deiry. Synergistic antitumor effect of ONC201 in combination with radiation therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2933.

Abstract 4165: Novel genetic rat models to identify factors that modulate cardiac and tumor radiation sensitivity

Abstract Purpose/Objectives: Over 50% of breast cancer patients receive radiation therapy, but radiation doses can be limited by normal tissue toxicity. Radiation therapy can improve breast cancer-specific survival, but cardiac morbidity can be increased in patients with left-sided tumors. We used rat genetic models to identify targets to improve the therapeutic ratio of radiation. We assessed the radiation responsiveness of mammary tumors and the heart in genetically similar consomic rats conducive to genetic mapping. Materials/Methods: Female SS rats and SS.BN3 consomic rats, which are genetically identical to SS rats except that chromosome 3 is inherited from the BN strain, have previously been shown to exhibit different vascular dynamics and breast tumor growth. Human MDA-MD-231 cells or syngeneic mammary tumor cells developed from DMBA-induced mammary tumors were implanted orthotopically into immunodeficient or immunocompetent SS and SS.BN3 rats, respectively, and tumors were treated locally with mock or 5x4 Gy. To examine cardiac toxicity, adult female SS and SS.BN3 rats received image-guided localized whole-heart radiation to a dose of 24 Gy or 9 Gy x 5 (AP and 2 lateral fields, weighted 1:1:1). Echocardiograms with strain analysis were performed at baseline, 3 months and 5 months. The Student's t-test was used to compare values. Results: The BN strain-derived genetic variant(s) on rat chromosome 3 is important for tumor radiation sensitivity. Tumors in SS.BN3 rats were significantly more radiosensitive than tumors in the parental SS strain. A supra-additive effect was seen with both tumor cell lines, with recurrence-free survival of 30% vs. 67% at 137 days in SS vs SS.BN3 rats (p=0.02) in xenografts, and recurrence-free survival of 9% vs. 100% at 141 days in SS vs. SS.BN3 rats (p&amp;lt;0.0001) in syngeneic tumors. The SS female rats that received 24 Gy exhibited enhanced cardiac toxicity compared to SS.BN3 rats, with larger pericardial effusions in SS vs SS.BN3 rats (p&amp;lt;0.05), significantly elevated end diastolic volume (EDV) and end systolic volume (ESV) at 5 months (EDV: 0.62 vs. 0.49 mL, p&amp;lt;0.01; ESV: 0.12 vs. 0.03 mL, p&amp;lt;0.01), and increased cardiac mortality (5/11 SS vs. 0/7 SS.BN3 rats). Fractionated heart radiation yielded similar results. Taken together, the SS.BN3 tumors are more sensitive to radiation, while the hearts of SS.BN3 rats are protected against radiation toxicity, when compared to the SS strain. Conclusions: These results demonstrate that genetic variants on rat chromosome 3 alter the sensitivity to radiation therapy, enhancing tumor responses to radiation and protecting the heart, thus improving the therapeutic ratio. Gene expression analysis and genetic mapping will be performed to identify the causative target(s). This project has the potential to enhance the effectiveness and toxicity profile of radiation therapy in breast cancer. Citation Format: Rachel A. Schlaak, Anne Frei, Aronne M. Schottstaedt, Brian L. Fish, Leanne Harmann, Tracy Gasperetti, Michael J. Flister, Meetha Medhora, Jennifer L. Strande, Carmen R. Bergom. Novel genetic rat models to identify factors that modulate cardiac and tumor radiation sensitivity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4165.

408P - Radiation-induced lung toxicity and tumor progression in patients with non-small-cell lung cancer

Background: Lung cancer is the leading cause of cancer death worldwide, and non-small cell lung cancer (NSCLC) accounts for 85% of all lung cancer cases. Radiotherapy is an important treatment modality, approximately two-thirds of lung cancer patients receive radiation therapy (RT) during the course of treatment with either definitive or palliative intent. However, radiation-induced lung toxicity, including radiation pneumonitis (RP) and subsequent lung fibrosis limits the therapeutic ratio and can also complicate quality of life for survivors. Meanwhile, most treated individuals develop disease recurrence that affects disease prognosis. Here we investigate the relationship between the radiation-induced lung toxicity and tumor progression in patients with non-small-cell lung cancer. Methods: From Jan. 2009 to Dec. 2014, patients who received definitive radiation therapy (RT) for stages I-III lung cancer and who were diagnosed with radiation-induced lung toxicity (RILT) were retrospectively analyzed. The primary endpoint was tumor progression (local progress and distant metastasis). The effect of RILT on overall survival (OS) and progression-free survival (PFS) of patients with different clinico-pathological factors were evaluated with Kaplan-Meier method and log-rank test. Results: Among 91 patients, tumor progression was observed in 73 (80%). RILT effect on the OS between no tumor progression and tumor progression (median OS 40.6 months versus 36.3 months, P < 0.01), and the PFS indicates that the patients with no tumor progression have a longer median progression-free survival (median PFS 26.7 versus 22.7 months, P < 0.01). Then RILT was divided into two grades, the severe RILT (60%) and mild RILT (40%), and stratified analysis revealed that the mild RILTs resulted in a favorable prognosis compared with the severe RILT (median PFS 39.5 v 22.7 months, P = 0.022). Meanwhile, through further analysis we found a close connection between the degrees of RILT and tumor progression (local progress and distant metastasis) (P < 0.001). Conclusions: Radiation-induced lung toxicity (RILT) is linked to tumor progression in patients with non-small-cell lung cancer received definitive radiation therapy (RT). Legal entity responsible for the study: Nannan Wang Funding: None Disclosure: All authors have declared no conflicts of interest.

The Next Hurdle for Personalized Medicine-Radiation Therapy.

Testing for somatic mutations in cancer is currently a widely accepted and often used tool. The molecular profile obtained from such testing helps to make decisions regarding chemotherapy regimens or targeted therapeutics. However, there is no use of such testing in radiation oncology where a wide range of patients get identical therapy regardless of genetic information. At the most recent annual meeting of the American Society for Radiation Oncology, multiple researchers presented data focused on incorporating genetic data into treatment decisions for radiation therapy (1). Areas of research included tumor profiling to determine radiation susceptibility and germline sequencing to determine the likelihood and severity of side effects of radiotherapy. Such research has the potential to greatly impact outcomes, since almost two-thirds of cancer patients receive radiation therapy of some form. While technologies …

Nanoparticle-Mediated Tumor Vascular Disruption: A Novel Strategy in Radiation Therapy

More than half of all cancer patients receive radiation therapy. Despite recent innovations, clinical delivery of curative radiation dose is severely restricted by proximal healthy tissues. Chemical and biological agents to augment the radiosensitization of cancer cells exhibit high off-target toxicity. We propose a dual-targeting strategy using vessel-targeted-radiosensitizing gold nanoparticles and conformal-image guided radiation therapy to specifically amplify damage in the tumor neoendothelium. Subsequent tumor vascular damage considerably improved the therapeutic outcome and subsidized the radiation and/or nanoparticle toxicity. This is a unique concept with clear translational path. (Arg-Gly-Asp)- and (PEG)-functionalized gold nanoparticles (RGD:AuNP) were designed and administered to mice pancreatic tumor xenografts (1.25 mg/mL equiv. Au) and angiogenic tumor blood vessels (expressing integrins) were targeted. In 24 h- post-administration, the mice were subjected to targeted irradiation (IR) to induce tumor vascular disruption. RGD:AuNP formulation (∼3 nm) is non-toxic and stable for more than 6 months. High-res.-TEM, LIBS/STEM imaging confirmed its preferential tumor endothelial uptake. By specifically targeting the early angiogenic neoendothelium, RGD:AuNP circumvent the dense stromal diffusion pathways that often limit the penetration and permeation of anti-cancer drugs and nanoparticles to the tumor cells - a limitation of current radiosensitization approaches. The sub- mm accuracy of image-guided radiation therapy facilitated increased radio-therapeutic efficacy (95-100% tumor-dose distribution) and less off-target toxicity. More than 2.5-fold differences in the specific tumor vascular damage was observed in +RGD:AuNP/+IR (compared to controls) when assessed by γH2AX, 3D-(confocal) vessel imaging, and IHC analysis. Targeted irradiation at 24 h following RGD:AuNP administration showed significant reduction in the tumor size and improved overall animal survival by >140 days (P< 0.0001, Mantel-Cox test), compared to non-treated IR controls (∼95 days). For the first time, our study demonstrates a catastrophic in vivo induction of “tumor vascular disruption” using targeted-gold nanoparticles and targeted-irradiation. The study was structured based on current clinical practices optimized for high therapeutic efficacy and minimal patient risk. This strategy may also be extended to other intransigent or non-resectable tumors for which radiation delivery is limited by adjacent organs, augmenting its potential clinical impact.