ASTRO Resident/Fellows Seed Grant

  • Applications for the 2018 Resident Seed Grant are now open!

    Applications must be submitted through Proposal Central: ASTRO Seed Grant Application

    Applications are due on April 8, 2018, at 11:59 p.m. Eastern time.

    What is the goal of the ASTRO Residents/Fellows in Radiation Oncology Seed Grant?

    This grant is designed to support residents or fellows who are planning a career focusing primarily on basic science or clinical research. It is designed for the exceptional trainee and implies dedication to a career in research.

    Previous Award Winners and Abstracts

  • Investigating the immunomodulatory effects of radiation with and without immune checkpoint inhibition in squamous cell carcinoma of the head and neck

    Devarati Mitra, 2017 Resident Seed Grant Winner

    Head and neck cancer is the sixth most common cancer worldwide. While patients with early stage disease are often cured with a combination of radiation, surgery and chemotherapy, more advanced disease, particularly in the context of tobacco use, is associated with high rates of disease recurrence and death. Patients with advanced head and neck cancer need new treatment options.

    The immune system is known to play an important role in surveillance of “foreign” material in the body including infectious agents and cancer cells. For years, investigators have sought to harness the power of the immune system to attack tumor cells, but the last decade has provided revolutionary new insight. The driving force of this advance is a new class of drug called immune checkpoint inhibitors that take the brakes off the immune system and allow improved recognition of cancer cells. These drugs have shown impressive, long-lasting efficacy in controlling a wide variety of advanced malignancies, including cancers of the head and neck. Unfortunately, most patients do not respond to immune checkpoint inhibitors alone. A recent large study of the immune checkpoint inhibitor nivolumab in patients with recurrent or metastatic head and neck cancer found that nivolumab significantly improved overall survival but had only a 13% response rate.

    In parallel, the last decade has demonstrated the power of more traditional therapeutic modalities, such as radiation therapy, to have profound effects on the ability of the immune system to successfully fight cancer. Shorter radiation treatment courses that deliver high doses of radiation per treatment, known as hypofractionated radiation, seem to be particularly effective at activating the local tumor immune environment. 

    The goal of the proposed studies is to investigate how hypofractionated radiation, either alone or in conjunction with immune checkpoint inhibition, alters tumor specific immune responses in head and neck cancer in patients and in 3 parallel mouse models of carcinogen-associated oral cancer that have known variable response to immune checkpoint inhibition. By characterizing the immunologic effects and disease progression of head and neck patients enrolled on early-phase prospective clinical trials in parallel with this spectrum of mouse models I will be able to pursue a truly bench-to-bedside approach. Ultimately, I hope to help illustrate that immune endpoints are relevant to disease outcomes and can be used to optimize the design of future clinical trials. In addition, I hope these studies will inform how best to combine radiation and immunotherapy with the goal of maximizing long-term disease response.

    microRNA-15a regulation of endothelial radiation sensitivity

    Shushan Rana, 2017 Resident Seed Grant Winner

    In recent years, safer delivery of higher doses of toxic radiation to cancer has been achieved by advancements in treatment techniques in the form of stereotactic body radiation therapy (SBRT) or stereotactic radiosurgery (SRS). However, certain disease sites do not permit these modalities due to extent of radiation coverage needed for optimal disease control and corresponding increased risk of damage to closely adjacent critical organs unaffected by cancer. The molecular response of cancer cells to escalating doses of radiation has revealed higher doses of radiation works beyond DNA damage and activates responses among the vasculature, immune cells, and architectural stromal cells adjacent to cancer cells collectively known as the tumor microenvironment (TME). A common regulatory element in the TME and radiation response are microRNA’s, which are small non-coding RNAs that inhibit the expression of a number of functionally related protein coding genes. With a focus on the vasculature, we focused our attention on acid sphingomyelinase, or sphingomyelin phosphodiesterase (SMPD1), which has been shown to enhance endothelial cell death via apoptosis. However, this phenomenon is observed only after administering higher doses of radiation. Recent work in our lab has revealed that the magnitude of radiation dose elicits distinct miRNA expression profiles. Among miRNAs which target SMPD1, miR-15a expressed the greatest magnitude difference between standard and ablative dose radiation with substantially lower miR-15a levels at higher doses. Initial mechanistic studies have demonstrated inhibition of miR-15a using an exogenous miR-15a inhibitor resembles cellular damage observed at ablative doses of radiation. In this context, we hypothesize inhibition of miR-15a will enhance radiation-induced endothelial apoptosis via preservation of SMPD1. The specific aims of this proposal are to 1) ascertain the functional mechanism by which miR-15a regulates SMPD1 and radiosensitivity in endothelial cells and 2) characterize the effects of vascular targeted in vivo delivery of miR-15a inhibitor on radiation inducible SMPD1-mediated apoptosis. Through methodical dissection of the miR-15a pathway, our long-term derivation of these data is to identify regulatory nodes amenable to modulation by pre-existing therapeutic agents or facilitate formulation of alternative therapies to enhance treatment of disease sites limited to lower dose radiation.

    The role of miR-34 in the DNA damage response and cancer cell immune evasion via regulation of PD-L1 after ionizing radiation

    Ye Yuan, 2017 Resident Seed Grant Winner

    Radiation kills cancer by damaging the DNA of cancer cells and causing an immune reaction within tumors. However, cancer cells can adapt by repairing areas of DNA damage and by expressing a protein called PD-L1 that can help them evade the immune system. We have found that a small RNA called microRNA-34, which is involved in DNA repair, is activated in some cancer cells shortly after radiation. There is also evidence that microRNA-34 can decrease the expression of PD-L1. Our goal is to determine if activation of microRNA-34 alters the sensitivity of cancer cells to radiation while simultaneously making cancer cells less able to evade the immune system.

    Redox imaging in cervical cancer as a predictive biomarker for traditional and novel therapeutics

    John Floberg, 2016 Resident Seed Grant Awardee

    Many women with cervical cancer relapse following definitive chemo-radiation therapy. One potential strategy to improve outcomes is to target redox pathways. Cervical cancer cells in an over-reduced state may be more resistant to oxidative stress. Novel therapeutics that shift cancer cells to a more oxidative state may therefore be beneficial. It may also be possible to image redox state (i.e. the oxidizing and reducing potential of cells) using [Cu-64]-copper(II)-diacetyl-bis(4- methylthiosemicarbazonato) ([Cu-64]-ATSM) positron emission tomography (PET), potentially combined with 2-deoxy-2-[F-18]-fluoro-D-glucose ([F-18]-FDG PET) and magnetic resonance imaging (MRI). Imaging biomarkers representative of redox state might therefore be predictive of response to therapy, and identify patients who will benefit from novel therapeutic strategies.

    The proposed study aims to characterize redox state of cervical cancer using multi-modality imaging, including [Cu-64]-ATSM PET, [F-18]-FDG PET, and diffusion weighted MRI (DWI), and to show that these metrics are predictive of response to traditional therapy, and novel therapies targeting redox pathways. This will be done in both in vitro and in vivo models of cervical cancer. 

    Targeting Glutamine Metabolism to Overcome Radioresistance in Non-Small Cell Lung Cancer

    Chirayu Patel, 2016 Resident Seed Grant Awardee

    Survival in advanced NSCLC remains limited despite targeted therapeutics and immune checkpoint inhibitors. Targeting cellular metabolism via inhibition of glutamine (Gln) uptake transport and metabolism is a novel treatment strategy: First, the hypoxic cancer microenvironment leads cancer to metabolically depend on glutamine (Gln) rather than glucose. Second, the resultant shift to Gln metabolism contributes to radioresistance as radiotherapy thrives on oxygen-related injury for DNA damage and apoptosis via reactive oxygen species (ROS) production. Glutamine is metabolized by glutaminase to glutamate, which is then used to synthesize glutathione, a scavenger for reactive oxygen species (ROS). Thus, targeting Gln transport and metabolism may render cells more sensitive to apoptosis. Third, to facilitate the translation of basic science discoveries regarding glutamine metabolism to impact patients, our laboratory is developing small molecule inhibitors (SMI) of clinically relevant amino acid transporters and has been authorized by Calithera Biosciences to conduct in vitro and in vivo studies using CB-839, a first-in-class selective, reversible, and orally bioavailable glutaminase inhibitor, which has undergone phase I clinical trials with a favorable safety profile. We hypothesize that upregulated glutamine metabolism in NSCLC leads to radioresistance via a ROS-dependent mechanism - targeting glutamine metabolism will radiosensitize NSCLC, both in lung cancer cell lines and a xenograft model. In aim 1, I will test the hypothesis that SLC1A5 overexpression supports lung cancer cells’ addiction to glutamine and renders them resistant to radiation therapy, which can be overcome with genetic or pharmacologic inhibition of SLC1A5 or glutaminase inhibition. In aim 2, I will determine the feasibility and efficacy of targeting glutamine metabolism using CB-839 in a xenograft mouse model of a lung cancer cell line overexpressing SLC1A5, with and without radiotherapy. Glutaminase targeting will be confirmed through metabolite analysis and in vivo ROS levels will be determined. With this experience, I expect to generate preliminary data to conduct an investigator-initiated clinical trial to examine the synergy between pharmacologic glutamine pathway inhibition and radiation therapy in NSCLC. Through the skills I will develop, I hope to complete a post-doctoral fellowship after residency and compete for a physician-scientist junior faculty position in radiation oncology.

    Focused Ultrasound-induced blood brain barrier disruption in checkpoint blockade immunotherapy and the abscopal effect

    Cheng-Chia Wu, 2016 Resident Seed Grant Awardee

    Cancer immunotherapy is a growing field for the treatment of melanoma.  Since the seminal studies examining the role of CTLA-4 (Cytotoxic T-Lymphocyte Antigen-4) in metastatic melanoma, immunotherapy targeting checkpoint inhibitors CTLA-4 and PD-1 (Programmed Death-1) have been recommended as accepted treatment for metastatic or unresectable disease.   Furthermore, initial case reports by Postow and colleagues, preclinical models, and retrospective studies have shown that the addition of radiation therapy can further promote this effect through the abscopal effect.  Historically, the central nervous system (CNS) was thought to be an immune privileged site protected by the blood brain barrier (BBB).  Clinical scenarios such as infectious encephalitis and autoimmune demyelinating disease suggest there is a degree of immune surveillance in the CNS in which lymphatic drainage, CNS antigen presentation niche, and the BBB may play a role.  Our hypothesis is that the integrity of the blood brain barrier may limit cross talk between the CNS and systemic immune system to checkpoint inhibitor targeted therapy and abscopal effect for intracranial metastatic melanoma.  Disruption of the blood brain barrier with focused ultrasound (FUS) can enhance the immune response and the abscopal effect in the brain.  The use of FUS to disrupt the BBB in the setting of checkpoint blockade immunotherapy and radiation induced abscopal effect has not been explored.  This is a novel project with clinical implications as the first patient treated with FUS to disrupt the BBB was recently performed in November 2015.  The proposed study will assist the applicant in pursuing an academic career with a focus in technology, neuroimmunology, and radiation oncology.

    Immuno-PET as a non-invasive biomarker to characterize the tumor microenvironment.

    Ariel Marciscano, 2015 Resident Seed Grant Awardee

    Over the past two decades the development of therapeutic monoclonal antibodies (mAbs) has led to considerable progress in the goal of achieving personalized cancer medicine. More recently, cancer immunotherapies, specifically immune checkpoint blockade mAbs have demonstrated significant efficacy and durable clinical responses in a proportion of patients across multiple cancer subtypes. There is now an expanding body of evidence that combining radiotherapy (RT) with immune checkpoint blockade can enhance anti-tumor immune responses and increase the therapeutic efficacy of RT. 

    Due to the rapidity at which immune checkpoint mAbs have been translated into clinical practice there is currently a paucity of prognostic or predictive biomarkers. High pre-treatment levels of Programmed Death-Ligand 1 (PD-L1) expression within the tumor microenvironment (TME) have correlated with response to anti-programmed death-1 (anti-PD-1) and anti-PD-L1 blockade. Data from our laboratory and others has suggested that stereotactic RT and anti-PD-1 treatment synergistically promotes anti-tumor immunity and enriches tumor-specific effector T-cell function. However, the mechanism of synergy between RT and anti-PD-1 is poorly understood and the impact of RT upon the tumor microenvironment and PD-L1 expression is yet to be defined.

    The aims of this study are to use immuno-Positron Emission Tomography (immuno-PET) in order to:

    1. Characterize the TME with respect to 89Zr-anti-PD-L1 targeting
    2. To assess the impact of stereotactic RT, anti-PD-1 mAb blockade and their combination upon the biodistribution of 89Zr-anti-PD-L1 within the TME
    3. To correlate 89Zr-anti-PD-L1 TME biodistribution with outcomes in murine models

    Immuno-PET is an emerging oncologic molecular imaging modality that utilizes radiolabeled mAbs directed at TME targets. The advent of immune checkpoint blockade provides a highly relevant and unique opportunity to apply immuno-PET to anti-PD-L1 mAbs. In vivo quantitative assessment of 89Zr-anti-PD-L1 over several time points can describe RT and anti-PD-1 blockade modulation of the TME thereby elucidating potential mechanisms of synergy. To our knowledge, this is a novel application of immuno-PET and the development of 89Zr-anti-PD-L1 as a non-invasive imaging biomarker would have tremendous clinical implications for both RT and immunotherapies moving forward.

    As we enter a potential paradigm shift in the era of cancer immunotherapy, improving our understanding of the host immune system and TME will be critical. Immuno-PET is a non-invasive tool that has the potential to help optimize the combination of stereotactic RT and immune checkpoint blockade and identify subsets of patients that will benefit from these therapies.

    Non-canonical mRNA translation in breast cancer progression and resistance

    David Mayhew, 2015 Resident Seed Grant Awardee

    The regulation of mRNA translation/protein synthesis is rapidly gaining interest in the field of cancer biology. Due to its fundamental dysregulation in cancer and its adaptive alterations in response to existing therapies, mRNA translation is increasingly recognized as a viable yet underutilized therapeutic target. Alternative mRNA translation strategies that do not use the canonical 5’-cap of the mRNA to engage the ribosome, such as those utilizing internal ribosome entry site (IRES) dependent mechanisms, may indeed play an important role in cancer progression. IRES translation is poorly understood, yet many oncogene and proto-oncogenes utilize IRES translation to regulate their expression, suggesting that IRES-regulated proteins may be involved in cancer treatment response and resistance. We will study the role of IRES translation in the cellular stress response and its subsequent impact on treatment resistance in multiple breast cancer cell lines in vitro as well as tumor xenografts in vivo. Identification and characterization of IRES-regulated proteins will lead to potential therapeutic targets to combat treatment resistance in breast cancer.

    A pilot study of perfusion CT for lung tumors treated with stereotactic ablative radiation therapy (SABR) 

    Jennifer Shah 

    2015 Resident Seed Grant Awardee 
    Standard treatment for medically inoperable early-stage lung cancer is stereotactic ablative radiotherapy (SABR), which yields tumor control rates similar to those of surgery. Still, 30% of patients develop disease recurrence. Early detection of recurrence is limited by standard imaging techniques due to radiographic pneumonitis, and no serum biomarkers are available. Perfusion CT characterizes the quality of tumor vasculature and potentially predicts recurrence and the need for adjuvant systemic therapy. Early vascular changes immediately following SABR may also suggest optimal timing for systemic therapy.
    This proposal is for a pilot study to investigate the feasibility of performing serial perfusion CT scans in patients undergoing lung tumor SABR with the long-term goal of characterizing the post-SABR vascular changes and correlating these changes with tumor response. Patients will undergo perfusion CT at three time points: at baseline (with the radiation treatment planning CT), within 6 hours of the first fraction of SABR, and at the time of the first post-treatment follow-up visit 3 months after treatment. Tumor perfusion parameters will be correlated with levels of circulating tumor DNA assayed by our novel individualized deep sequencing approach (CAPP-Seq), radiologic response, and disease recurrence at one year.
    Perfusion CT is non-invasive, relatively inexpensive, and widely available for implementation into clinical practice. As this is emerging technology, there are currently no reports in the literature of Perfusion CT following SABR treatment. Stanford is one of only a few institutions with the facilities to perform Perfusion CT as early as within less than one hour of SABR treatment.
    Results of this pilot study will be used to design subsequent trials during a research fellowship to investigate perfusion CT as a predictive imaging biomarker for therapeutic response, and to identify candidate patients for and the optimal timing of adjuvant systemic therapy.

    The role of radiation in adaptive immune resistance and de novo antitumor immune response 

    Todd Aguilera, 2014 Resident Seed Grant Awardee 

    In recent years much has been learned about tumor associated antigens that the immune system uses to distinguish tumor cells and how the immune system can be activated to respond to cancer. Immune checkpoint inhibitors are a class of cancer therapeutics that arose from blocking inhibitory receptors that prevent a cancer immune response and have enabled dramatic antitumor responses in specific cases. Though there have been notable breakthroughs with this class of agents they are considered to be active primarily in immunogenic tumors. This project aims to investigate reasons why in the setting of checkpoint blockade tumor immunity often does not occur. It is hypothesized that radiation can play an important synergistic role in the setting of checkpoint blockade to enhance responses through increasing antigen presentation and altering immunosuppressive tumor lymphocytes. This study will also evaluate the ‘abscopal effect’ of radiation that when combined with immune checkpoint blockade can lead to immune responses to untreated tumors. There is need to validate the mechanistic hypotheses for these phenomena and apply them to poorly immunogenic tumors with the goal of developing a therapeutic regimen that can impact a broader number of cancers than currently capable with mono therapy. This study will evaluate how PD-1 inhibition synergizes with radiation. It will explore methodologies that exploit the emerging hypotheses of adaptive immune resistance and de novo antitumor response. Tumors that respond to checkpoint inhibition alone by expressing tumor antigen will be compared with poorly immunogenic tumors, and new combination approaches that include radiation will be explored. This proposal aims to unveil important aspects of tumor immunity allowing a greater impact of immune checkpoint targeted therapeutics.

    The role of miR-21 in breast cancer progression and sensitivity to cytotoxic therapy

    Tu Dan, 2014 Resident Seed Grant Awardee 

    Breast cancer is known to be a heterogeneous disease entity. While the majority of women have favorable outcomes, there is a subset of women with disease resistant to standard treatments. These tumors are often associated with basal-like gene expression and triple negative receptor status. Triple negative breast cancers (TNBC) have been found to have similar features as BRCA-defective tumors, leading to similar use of targeted therapies exploiting existing DNA-repair defects in this population. However, although successful in BRCA-mutated cancers, clinical studies targeting DNA repair pathways have been equivocal in TNBCs, leading some to believe that these cancers may be more resistant to DNA damage than previously thought.

    Recent data has implicated the role of oncogenic microRNAs in driving treatment resistance. miR-21, in particular, has been found to be up-regulated in over 18 major cancer types and has been linked to radiation and chemotherapy resistance. It is associated with genes involved in DNA repair, cell cycle redistribution, tumor hypoxia, and has been experimentally found to target known tumor suppressors. Our laboratory has previously shown that miR-21 plays a role in the stress response induced by radiation-linked to DNA damage. We have demonstrated increased radiosensitivity in vitro when knocking down miR-21 in multiple radioresistant breast cancer cell lines. We have also generated a miR-21 knock out mouse demonstrating more than 2-fold increase in radiosensitivity than its wild type counterparts. Radiated tissue from these mice also reveal more double strand breaks than those of radiated wild type mice. In silico analysis indicates multiple targets of miR-21 involved in DNA repair mechanisms such as homologous recombination, particularly with targets in the cohesin complex, a highly conserved protein complex involved in DNA repair and replication.

    We hypothesize that miR-21 up-regulation drives radiation resistance in breast cancers via alterations in the cohesin complex. Inhibition of miR-21 may be a novel approach to overcome treatment resistance and sensitize tumors to DNA-damaging agents. These findings would further elucidate mechanisms regarding treatment resistance and potentially augment existing therapeutics in a population of patients with poor prognosis and limited treatment options.

    Engaging antibody-dependent cell-mediated cytotoxicity to augment the synergy of radiation and T cell checkpoint inhibition

    Zachary Morris, 2014 Resident Seed Grant Awardee

    Evasion of immune detection is essential to the progression of malignancy. Immunotherapies elicit an anti-tumor response by engaging the immune system to recognize and eliminate tumor cells. A growing body of evidence suggests radiation may compliment immunotherapies by enhancing the immune susceptibility of tumor cells and generating tumor-specific antigens. We have been investigating the synergy of radiation and antibody-dependent cell-mediated cytotoxicity (ADCC) in a syngeneic murine model of melanoma. In these studies we have observed therapeutic cooperation of radiation and ADCC with respect to local tumor control without clear evidence of a systemic or memory T cell response. This is consistent with prior studies, which indicate that cells of the innate immune system principally mediate ADCC. Prior studies from other labs have demonstrated cooperation and modest rates of systemic T cell response when combining radiation and T cell checkpoint inhibitors, which enhance T cell activation. Given the complementary roles of the innate and adaptive immune system as well as the critical role of innate immune cells in priming adaptive immune response, we hypothesize that a therapeutic approach combining radiation, tumor-specific ADCC, and a T cell checkpoint inhibitor may synergize to augment local, systemic, and memory anti-tumor immune responses. Using a syngeneic mouse model of melanoma, we will test this hypothesis in vivo by comparing the efficacy of combinations of radiation, a tumor specific antibody that elicits ADCC, and a checkpoint inhibitor with respect to the control of local, distant (non-radiated), and re-introduced sites of disease. Using flow cytometry and immunofluorescence microscopy we will quantitatively and

    qualitatively evaluate the immune response generated by these treatments. Results from this translational study will inform our understanding of the interactions between radiotherapy and the innate and adaptive immune system and will guide future clinical investigation.  

    Analysis of radiation induced antigen specific immune responses

    Andrew Sharabi, 2013 Resident Seed Grant Awardee

    One of the most desirable attributes of the immune system is the ability to develop highly specific and systemic responses to antigens. In the past, cytotoxic therapies such as chemotherapy and radiation were thought to suppress the immune system. However, recent data have shown that radiation can induce changes in tumor cells which promote immune responses and increase tumor susceptibility to immune-mediated cell death. Additionally, monoclonal antibodies which block negative regulators or checkpoints of the immune system such as CTLA-4 and PD-1 are gaining recognition as immunotherapy agents which can enhance immune responses in multiple different tumor types. Interestingly, when radiation is used in combination with these monoclonal antibodies there is preclinical data and case reports of robust immune responses and long term systemic tumor control. Furthermore, recent provocative evidence in breast cancer, colorectal cancer, and melanoma suggests that focused radiation can in fact stimulate an anti-tumor immune response which can act at distant sites outside of the radiation field, termed the Abscopal effect. 

    Our hypothesis is that the strategic use of radiation combined with novel immunotherapy agents will lead to synergistic effects and improved clinical outcomes due to radiation induced antigen specific immune responses (abscopal effect). We propose to investigate many fundamental questions regarding the abscopal effect with the following specific aims:

    Specific Aim 1: Determine the optimal dose and fractionation for generation of radiation induced antigen specific immune responses.  We will generate antigen-specific in vivo mouse models of the abscopal effect based on the previously described MCA38 cancer cell line. Our small animal radiation research platform (SARRP) will be used to deliver stereotactic image-guided radiotherapy with clinically relevant doses and fractionation. We will then systematically quantify the effects of total dose, dose per fraction, number of fractions, and biologically equivalent dose to optimize radiation induced antigen specific immune responses.

    Specific Aim 2: Characterize the pre-clinical effects of anti-PD1 antibody on the magnitude and duration of radiation induced antigen specific immune responses (abscopal effect). We will characterize the role anti-PD1 Ab in augmenting abscopal responses when given concurrently with radiation. The effect of varied timing and frequency of anti-PD1 Ab on the magnitude of immune and memory T-cell responses will also be characterized. 

    Overall, these Specific Aims will answer critical fundamental questions regarding radiation induced immune responses. Specific Aim 1 has the potential to identify the optimal radiation dose and fractionation for induction of immune responses. Specific Aim 2 would provide pre-clinical evidence for a novel treatment paradigm of combining stereotactic radiotherapy with anti-PD1 Ab for improved loco-regional and distant control.

    The Hedgehog pathway modulates radiotherapy resistance in head and neck cancer

    Gregory Gan, 2013 Resident Seed Grant Awardee 

    Background: The epidermal growth factor receptor (EGFR) is preferentially expressed in HPV negative (HPV-) head/neck squamous cell carcinomas (HNSCC) and is associated with a more aggressive phenotype. Resistance to EGFR blockade and radiotherapy (RT) remains a significant problem for both locoregional and distant tumor control due to accelerated repopulation mediated by the Hedgehog Pathway (HhP) and the Epithelial to Mesenchymal Transition (EMT). Our lab has demonstrated that the HhP is upregulated in response to RT both acutely and in chronically irradiated cell lines and this can be suppressed with the HhP inhibitor, cyclopamine. Preliminary mouse xenograft studies have shown that dual therapy with RT and cyclopamine is associated with improved tumor control. However, the molecular mechanism for GLI1 nuclear translocation following RT and what role GLI1 plays on the tumor microenvironment remain unknown.

    Specific Aims: (1) Determine whether the DNA damage response pathway effects GLI1 translocation into the nucleus following RT and (2) Determine whether HhP inhibition of tumor stroma/microenvironment contributes to enhanced tumor control following RT in vivo. 

    Study Design: (1) We will evaluate GLI1 translocation into the nucleus using immunoblot and immunohistochemistry (IHC) following RT using commercial HNSCC cell lines and a GLI1 overexpressing cell line. Using a combination of siRNA and kinase specific inhibitors, we will determine whether ATM, ATR or DNA-PK pathways and whether the downstream effectors AKT and S6K1 are associated with GLI1 translocation. (2) We will implant HNSCC cell lines or patient-derived HNSCC tumor xenografts using a floor of mouth model; these animals will be treated with either RT, cyclopamine, or both and their tumors excised during and at the termination of treatment. Tumor and surrounding stroma will be evaluated using IHC and laser-capture microdissection/quantititative RT-PCR for GLI1 expression in addition to evaluating apoptosis via cleaved caspase 3 through IHC. We will also evaluate the long-term tumor control rates associated with monotherapy versus dual therapy. In a parallel pharmacodynamic study using the same 4 groups, we will flow sort stromal and tumor cells derived from these 4 groups and mix them 1:1 with untreated tumor cells and evaluate tumor regrowth kinetics in newly implanted mice.

    Significance: Elucidating GLI1 nuclear translocation and its expression in the microenvironment of head/neck cancer following RT will provide a better molecular understanding of GLI1 regulation and whether stromal GLI1 expression in vivo is associated with tumor survival following genotoxic stress. This knowledge could then be used to more intelligently combine targeted agents that synergize with RT and HhP inhibitors.  

    Epithelial to mesenchymal transition as a therapeutic target in prostate cancer

    Darrion Mitchell, 2013 Resident Seed Grant Awardee

    Metastasis is an underlying cause of cancer mortality. Although improved treatments have increased overall survival and improved quality of life for cancer patients, there is much progress to be made in developing treatments for advanced metastatic cancer, including prostate cancer. Epithelial to mesenchymal transition (EMT) is a well-documented phenomenon important for both embryonic development in mammals and metastatic invasion in malignancies. EMT also serves as a mechanism enabling metastatic foci to develop resistance to radio- and chemotherapy. Published data indicate autophagy may be partly responsible for therapeutic resistance. Autophagy is a cellular process that removes damaged organelles, such as mitochondria and intracellular molecules, from cells enabling them to sustain metabolism and function. However, whether autophagy is linked to EMT-like states is unknown. Preliminary data from our lab show elevated autophagy in prostate cancer cells in an EMT-like state. Genetic inhibition of autophagy via knock down of the autophagy-mediating protein ATG5 in TEM 4-18 cells led to decreased cell survival under conditions of energetic stress. Our lab has also shown pharmacological inhibition via chloroquine leads to decreased autophagy and subsequent cell death. Chloroquine inhibits autophagy in breast, pharyngeal, and cervical cancer cell lines. Data from our lab shows it inhibits autophagy in prostate cancer cells as well. Our first aim will determine if inhibiting autophagy by chloroquine leads to radiosensitization of prostate cancer cells in the EMT-like state by increasing oxidative stress. Our second aim focuses on identifying novel small molecules that are selectively cytotoxic to prostate cancer cells in the EMT-like state via the development of a high-throughput assay. We will investigate fifteen novel chloroquine analogs and many other compounds via the Microsource 2300 library. Our long term goal is that this work will substantially improve our current management of metastatic disease, contributing to the advancement of targeted therapy for not only prostate cancer metastasis but other cancers as well.

  • Am I Eligible?

    You are eligible if:

    • You show a commitment to a career that focuses primarily on radiation oncology sciences.
    • Your institution has a well-established research and clinical career development program and qualified faculty in radiation oncology sciences to serve as mentors.
    • You have identified a mentor with extensive research experience to support your project. Both the mentor and applicant should be an ASTRO member.

    What are the Terms of the Grant?

    Two grants of up to $25,000 each will be awarded. Each project is for one year. The recipients are expected to devote 75 percent of their professional effort toward the goals of this award.

    How Do I Apply?

    Complete the application online. Paper applications are not accepted. View the award requirements and obligations.

    When is the Application Deadline?

    The application site will be open from Monday, January 15, 2018 through Sunday, April 8, 2018.

    When Does the Grant Begin?

    The start date for the 2018 awards was be July 1. For any questions please email the Scientific Affairs Department.