Widening the therapeutic window for central and ultra-central thoracic oligometastatic disease with stereotactic MR-guided adaptive radiation therapy (SMART)

BACKGROUND/PURPOSE

Central/ultra-central thoracic tumors are challenging to treat with stereotactic radiotherapy due potential high-grade toxicity. Stereotactic MR-guided adaptive radiation therapy (SMART) may improve the therapeutic window through motion control with breath-hold gating and real-time MR-imaging as well as the option for daily online adaptive replanning to account for changes in target and/or organ-at-risk (OAR) location.

MATERIALS/METHODS

26 central (19 ultra-central) thoracic oligoprogressive/oligometastatic tumors treated with isotoxic (OAR constraints-driven) 5-fraction SMART (median 50 Gy, range 35-60) between 10/2019-10/2022 were reviewed. Central tumor was defined as tumor within or touching 2 cm around proximal tracheobronchial tree (PBT) or adjacent to mediastinal/pericardial pleura. Ultra-central was defined as tumor abutting the PBT, esophagus, or great vessel. Hard OAR constraints observed were ≤ 0.03 cc for PBT V40, great vessel V52.5, and esophagus V35. Local failure was defined as tumor progression/recurrence within the planning target volume.

RESULTS

Tumor abutted the PBT in 31 %, esophagus in 31 %, great vessel in 65 %, and heart in 42 % of cases. 96 % of fractions were treated with reoptimized plan, necessary to meet OAR constraints (80 %) and/or target coverage (20 %). Median follow-up was 19 months (27 months among surviving patients). Local control (LC) was 96 % at 1-year and 90 % at 2-years (total 2/26 local failure). 23 % had G2 acute toxicities (esophagitis, dysphagia, anorexia, nausea) and one (4 %) had G3 acute radiation dermatitis. There were no G4-5 acute toxicities. There was no symptomatic pneumonitis and no G2 + late toxicities.

CONCLUSION

Isotoxic 5-fraction SMART resulted in high rates of LC and minimal toxicity. This approach may widen the therapeutic window for high-risk oligoprogressive/oligometastatic thoracic tumors.

Association of Patient Experience of Care and Radiation Therapy Initiation Among Women With Early-Stage Breast Cancer

PURPOSE

For women diagnosed with early-stage breast cancer, lumpectomy followed by radiation therapy (RT) has been a guideline-recommended treatment. However, lumpectomy followed by hormonal therapy is also an approved treatment for certain women. It is unclear what patient-driven factors are related to decisions to receive RT. This study examined relationships between patient-reported experience of care, an important dimension of health care quality, and receipt of RT after lumpectomy.

METHODS AND MATERIALS

We used National Cancer Institute Surveillance, Epidemiology, and End Results data linked to the CMS Medicare Consumer Assessment of Healthcare Providers and Systems patient surveys (SEER-CAHPS) to examine experiences of care among women diagnosed with local/regional stage breast cancer 2000 to 2017 who received lumpectomy, were enrolled in fee-for-service Medicare, completed a CAHPS survey ≤18 months after diagnosis, and survived for this study period. Experience of care was assessed by patient-provided scores for physicians, doctor communication, care coordination, and other aspects of care. Multivariable logistic regression models assessed associations of receipt of external beam RT with care experience and patient sociodemographic and clinical characteristics.

RESULTS

The study population included 824 women; 655 (79%) received RT. Women with higher experience of care scores for their personal doctor were significantly more likely to have received any RT (odds ratio [OR], 1.18; P = .033). Nonsignificant trends were observed for associations of increased RT with higher CAHPS measures of doctor communications (OR, 1.15; P = .055) and care coordination (OR, 1.24; P = .051). In contrast, women reporting higher scores for Part D prescription drug plans were significantly less likely to have received RT (OR, 0.78; P = .030).

CONCLUSIONS

Patient experience of care was significantly associated with receipt of RT after lumpectomy among women with breast cancer. Health care organization leaders may want to consider incorporating experience of care into quality improvement initiatives and other activities that aim to improve patient decision-making, care, and outcomes.

Serum miRNA-based signature indicates radiation exposure and dose in humans: A multicenter diagnostic biomarker study

PURPOSE

Mouse and non-human primate models showed that serum miRNAs may be used to predict the biological impact of radiation doses. We hypothesized that these results can be translated to humans treated with total body irradiation (TBI), and that miRNAs may be used as clinically feasible biodosimeters.

METHODS

To test this hypothesis, serial serum samples were obtained from 25 patients (pediatric and adults) who underwent allogeneic stem-cell transplantation and profiled for miRNA expression using next-generation sequencing. miRNAs with diagnostic potential were quantified with qPCR and used to build logistic regression models with lasso penalty to reduce overfitting, identifying samples drawn from patients who underwent total body irradiation to a potentially lethal dose.

RESULTS

Differential expression results were consistent with previous studies in mice and non-human primates. miRNAs with detectable expression in this and two prior animal sets allowed for distinction of the irradiated from non-irradiated samples in mice, macaques and humans, validating the miRNAs as radiation-responsive through evolutionarily conserved transcriptional regulation mechanisms. Finally, we created a model based on the expression of miR-150-5p, miR-30b-5p and miR-320c normalized to two references and adjusted for patient age with an AUC of 0.9 (95%CI:0.83-0.97) for identifying samples drawn after irradiation; a separate model differentiating between high and low radiation dose achieved AUC of 0.85 (95%CI: 0.74-0.96).

CONCLUSIONS

We conclude that serum miRNAs reflect radiation exposure and dose for humans undergoing TBI and may be used as functional biodosimeters for precise identification of people exposed to clinically significant radiation doses.

Fate and Efficacy of Engineered Allogeneic Stem Cells Targeting Cell Death and Proliferation Pathways in Primary and Brain Metastatic Lung Cancer

Primary and metastatic lung cancer is a leading cause of cancer-related death and novel therapies are urgently needed. Epidermal growth factor receptor (EGFR) and death receptor (DR) 4/5 are both highly expressed in primary and metastatic non-small cell lung cancer (NSCLC); however, targeting these receptors individually has demonstrated limited therapeutic benefit in patients. In this study, we created and characterized diagnostic and therapeutic stem cells (SC), expressing EGFR-targeted nanobody (EV) fused to the extracellular domain of death DR4/5 ligand (DRL) (EVDRL) that simultaneously targets EGFR and DR4/5, in primary and metastatic NSCLC tumor models. We show that EVDRL targets both cell surface receptors, and induces caspase-mediated apoptosis in a broad spectrum of NSCLC cell lines. Utilizing real-time dual imaging and correlative immunohistochemistry, we show that allogeneic SCs home to tumors and when engineered to express EVDRL, alleviate tumor burden and significantly increase survival in primary and brain metastatic NSCLC. This study reports mechanistic insights into simultaneous targeting of EGFR- and DR4/5 in lung tumors and presents a promising approach for translation into the clinical setting.

Smart Radiotherapy Biomaterials for Image-Guided In Situ Cancer Vaccination

Recent studies have highlighted the potential of smart radiotherapy biomaterials (SRBs) for combining radiotherapy and immunotherapy. These SRBs include smart fiducial markers and smart nanoparticles made with high atomic number materials that can provide requisite image contrast during radiotherapy, increase tumor immunogenicity, and provide sustained local delivery of immunotherapy. Here, we review the state-of-the-art in this area of research, the challenges and opportunities, with a focus on in situ vaccination to expand the role of radiotherapy in the treatment of both local and metastatic disease. A roadmap for clinical translation is outlined with a focus on specific cancers where such an approach is readily translatable or will have the highest impact. The potential of FLASH radiotherapy to synergize with SRBs is discussed including prospects for using SRBs in place of currently used inert radiotherapy biomaterials such as fiducial markers, or spacers. While the bulk of this review focuses on the last decade, in some cases, relevant foundational work extends as far back as the last two and half decades.

Radiation-induced circulating microRNAs linked to echocardiography parameters after radiotherapy

Introduction

Patients treated with radiotherapy to the chest region are at risk of cardiac sequelae, however, identification of those with greatest risk of complications remains difficult. Here, we sought to determine whether short-term changes in circulating miRNA expression are related to measures of cardiac dysfunction in follow-up.

Materials and methods

Two parallel patient cohorts were enrolled and followed up for 3 years after completion of RT to treat left-sided breast cancer. In the primary group (N=28) we used a a panel of 752 miRNAs to identify miRNAs associated with radiation and cardiac indices at follow up. In the second, independent cohort (N=56) we validated those candidate miRNAs with a targeted qPCR panel. In both cohorts. serum samples were collected before RT, 24h after the last dose and 1 month after RT; cardiac echocardiography was performed 2.5-3 year after RT.

Results

Seven miRNAs in the primary group showed marked changes in serum miRNAs immediately after RT compared to baseline and associations with cardiopulmonary dose-volume histogram metrics. Among those miRNAs: miR-15b-5p, miR-22-3p, miR-424-5p and miR-451a were confirmed to show significant decrease of expression 24 hours post-RT in the validation cohort. Moreover, miR-29c, miR-451 and miR-424 were correlated with the end-diastolic diameter of the left ventricle, which was also confirmed in multivariable analysis adjusting for RT-associated factors.

Conclusion

We identified a subset of circulating miRNAs predictive for cardiac function impairment in patients treated for left-sided breast cancer, although longer clinical observation could determine if these can be used to predict major clinical endpoints.

Lobar or Sublobar Resection for Peripheral Stage IA Non-Small-Cell Lung Cancer

BACKGROUND

The increased detection of small-sized peripheral non-small-cell lung cancer (NSCLC) has renewed interest in sublobar resection in lieu of lobectomy.

METHODS

We conducted a multicenter, noninferiority, phase 3 trial in which patients with NSCLC clinically staged as T1aN0 (tumor size, ≤2 cm) were randomly assigned to undergo sublobar resection or lobar resection after intraoperative confirmation of node-negative disease. The primary end point was disease-free survival, defined as the time between randomization and disease recurrence or death from any cause. Secondary end points were overall survival, locoregional and systemic recurrence, and pulmonary functions.

RESULTS

From June 2007 through March 2017, a total of 697 patients were assigned to undergo sublobar resection (340 patients) or lobar resection (357 patients). After a median follow-up of 7 years, sublobar resection was noninferior to lobar resection for disease-free survival (hazard ratio for disease recurrence or death, 1.01; 90% confidence interval [CI], 0.83 to 1.24). In addition, overall survival after sublobar resection was similar to that after lobar resection (hazard ratio for death, 0.95; 95% CI, 0.72 to 1.26). The 5-year disease-free survival was 63.6% (95% CI, 57.9 to 68.8) after sublobar resection and 64.1% (95% CI, 58.5 to 69.0) after lobar resection. The 5-year overall survival was 80.3% (95% CI, 75.5 to 84.3) after sublobar resection and 78.9% (95% CI, 74.1 to 82.9) after lobar resection. No substantial difference was seen between the two groups in the incidence of locoregional or distant recurrence. At 6 months postoperatively, a between-group difference of 2 percentage points was measured in the median percentage of predicted forced expiratory volume in 1 second, favoring the sublobar-resection group.

CONCLUSIONS

In patients with peripheral NSCLC with a tumor size of 2 cm or less and pathologically confirmed node-negative disease in the hilar and mediastinal lymph nodes, sublobar resection was not inferior to lobectomy with respect to disease-free survival. Overall survival was similar with the two procedures. (Funded by the National Cancer Institute and others; CALGB 140503 ClinicalTrials.gov number, NCT00499330.).

Targeting DNA repair with combined inhibition of NHEJ and MMEJ induces synthetic lethality in TP53-mutant cancers

DNA repair pathway inhibitors are a new class of anti-cancer drugs that are advancing in clinical trials. Peposertib is an inhibitor of DNA-dependent protein kinase (DNA-PK), which is a key driver of non-homologous end-joining (NHEJ). To identify regulators of response to peposertib, we performed a genome-wide CRISPR knockout screen and found that loss of POLQ (Polymerase Theta, POLθ) and other genes in the microhomology-mediated end-joining (MMEJ) pathway as key predictors of sensitivity to DNA-PK inhibition. Simultaneous disruption of two DNA repair pathways via combined treatment with peposertib plus a POLθ inhibitor novobiocin exhibited synergistic synthetic lethality resulting from accumulation of toxic levels of DNA double-strand break end resection. TP53-mutant tumor cells were resistant to peposertib but maintained elevated expression of POLQ and increased sensitivity to novobiocin. Consequently, the combination of peposertib plus novobiocin resulted in synthetic lethality in TP53-deficient tumor cell lines, organoid cultures, and patient-derived xenograft models. Thus, the combination of a targeted DNA-PK/NHEJ inhibitor with a targeted POLθ/MMEJ inhibitor may provide a rational treatment strategy for TP53-mutant solid tumors.

Abstract 796: Dual inhibition of NHEJ and MMEJ induces synthetic lethality in TP53 mutant cancers

DNA repair pathway inhibitors are a new class of anti-cancer drugs that are advancing in clinical trials. While inhibitors of targets in the Non-Homologous End Joining (NHEJ) DNA repair pathway, such as DNA-dependent protein kinase (DNA-PK), are available for clinical use, it remains unclear which cancers are vulnerable to these agents. In a genome-wide CRISPR knockout screen with the DNA-PK inhibitor M3814, we identify loss of POLQ, encoding polymerase theta, and other genes in the microhomology-mediated end-joining (MMEJ) pathway as key predictors of sensitivity to DNA-PK inhibition, whereas loss of TP53 conferred resistance to DNA-PK inhibition. Inhibition of DNA-PK led to increased DNA double strand break end-resection, increased expression of polymerase theta, and activation of MMEJ repair. Combined DNA-PK inhibition by M3814 and polymerase theta inhibition by novobiocin resulted in synthetic lethality mediated by the accumulation of resected DNA and apoptosis. Significantly, this drug combination efficiently killed TP53-deficient human patient-derived xenografts and the corresponding tumor organoids. Taken together, our results provide a rationale for the combination of an inhibitor of DNA-PK mediated NHEJ and an inhibitor of polymerase theta mediated MMEJ in an anti-cancer trial. If DNA-PK is inhibited, cancers develop a hyper-dependence on MMEJ and an upregulation of DNA double strand break end resection and polymerase theta expression. Similarly, P53-deficiency which confers resistance to DNA-PK inhibition, also leads to a hyper-dependence on MMEJ and an upregulation of polymerase theta expression. Thus, a combination of DNA-PK and polymerase theta inhibitors may provide a precision treatment strategy for TP53-mutant solid tumors, known to account for 50% of newly diagnosed cancers.

Citation Format: Jeffrey Patterson-Fortin, Arindam Bose, Wei-Chih Tsai, Carter Grochala, Huy Nguyen, Jia Zhou, Kalindi Parmar, Jean-Bernard Lazaro, Joyce Liu, Kelsey McQueen, Geoffrey I. Shapiro, David Kozono, Alan D. D'Andrea. Dual inhibition of NHEJ and MMEJ induces synthetic lethality in TP53 mutant cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 796.

Rates of Guideline-Concordant Surgery and Adjuvant Chemotherapy Among Patients With Early-Stage Lung Cancer in the US ALCHEMIST Study (Alliance A151216)

Importance

Standard treatment for resectable non-small cell lung cancer (NSCLC) includes anatomic resection with adequate lymph node dissection and adjuvant chemotherapy for appropriate patients. Historically, many patients with early-stage NSCLC have not received such treatment, which may affect the interpretation of the results of adjuvant therapy trials.

Objective

To ascertain patterns of guideline-concordant treatment among patients enrolled in a US-wide screening protocol for adjuvant treatment trials for resected NSCLC.

Design, Setting, and Participants

This retrospective cohort study included 2833 patients with stage IB to IIIA NSCLC (per American Joint Committee on Cancer 7th edition criteria) who enrolled in the Adjuvant Lung Cancer Enrichment Marker Identification and Sequencing Trial (ALCHEMIST) screening study (Alliance for Clinical Trials in Oncology A151216) from August 18, 2014, to April 1, 2019, and who did not enroll in a therapeutic adjuvant clinical trial; patients had tumors of at least 4 cm and/or with positive lymph nodes. Statistical analysis was conducted from June 1, 2020, through October 1, 2021.

Exposures

Care patterns were ascertained overall and by sociodemographic and clinical factors, including age, sex, race and ethnicity, educational level, marital status, geography, histologic characteristics, stage, genomic variant status, smoking history, and comorbidities.

Main Outcomes and Measures

Five outcomes are reported: whether patients (1) had anatomic surgical resection, (2) had adequate lymph node dissection (≥1 N1 nodal station plus ≥3 N2 nodal stations), (3) received any adjuvant chemotherapy, (4) received any cisplatin-based adjuvant chemotherapy, and (5) received at least 4 cycles of adjuvant chemotherapy.

Results

Of the 2833 patients (1505 women [53%]; mean [SD] age, 66.5 [9.2] years) included in this analysis, 2697 (95%) had anatomic surgical resection, 1513 (53%) had adequate lymph node dissection, 1617 (57%) received any adjuvant chemotherapy, 1237 (44%) received at least 4 cycles of adjuvant platinum-based chemotherapy, and 965 (34%) received any cisplatin-based adjuvant chemotherapy. Rates were similar across race and ethnicity.

Conclusions and Relevance

This cohort study found that among participants in a screening protocol for adjuvant clinical trials for resected early-stage NSCLC, just 53% underwent adequate lymph node dissection, and 57% received adjuvant chemotherapy, despite indications for such treatment. These results may affect the interpretation of adjuvant trials. Efforts are needed to optimize the use of proven therapies for early-stage NSCLC.

Trial Registration

ClinicalTrials.gov Identifier: NCT02194738.

The clinician's guide to radiotherapy complications

Radiotherapy is one of the oldest cancer treatment modalities, used for over 100 years. As its efficacy has been steadily increasing due to the introduction of novel treatment methods, adverse events (AEs) still pose a major obstacle limiting the therapeutic benefits in some patients and negatively impacting treatment outcomes. In light of the technological progress, the focus has been shifted from improving the efficacy to safeguarding patients from the most severe AEs through improvements of safety and accuracy of radiation delivery. Currently, with radiation therapy being an effective treatment associated with frequent therapeutic success and leading to increased and prolonged survival, the problem of treatment‑related AEs is growing as there are numerous survivors whose health and quality of life may be adversely affected. Due to the limited access to radiation oncologists, patients presenting with AEs are often referred to other professionals for advice, and as survivorship prolongs, the AEs may aggravate current patient comorbidities or reveal undiagnosed diseases. Thus, it is important that doctors other than oncologists be familiar with the fundamentals of radiation therapy-related AEs and their management. In this review, we present the most common and severe AEs of radiotherapy associated with damage to the nervous, respiratory, cardiovascular, gastrointestinal, and urogenital systems. We also describe the pathogenesis of these AEs, and provide guidelines for prevention, risk assessment, diagnosis, and treatment. Novel findings and future perspectives in this field are also elucidated, including examples of ongoing clinical trials aimed not only at improving treatment outcomes but also at reducing the risk of radiotherapy complications in cancer treatment survivors.

Radiation Induces Valvular Interstitial Cell Calcific Response in an in vitro Model of Calcific Aortic Valve Disease

Background: Mediastinal ionizing radiotherapy is associated with an increased risk of valvular disease, which demonstrates pathological hallmarks similar to calcific aortic valve disease (CAVD). Despite advances in radiotherapy techniques, the prevalence of comorbidities such as radiation-associated valvular disease is still increasing due to improved survival of patients receiving radiotherapy. However, the mechanisms of radiation-associated valvular disease are largely unknown. CAVD is considered to be an actively regulated disease process, mainly controlled by valvular interstitial cells (VICs). We hypothesize that radiation exposure catalyzes the calcific response of VICs and, therefore, contributes to the development of radiation-associated valvular disease.

Methods and Results: To delineate the relationship between radiation and VIC behavior (morphology, calcification, and matrix turnover), two different in vitro models were established: (1) VICs were cultured two-dimensional (2D) on coverslips in control medium (CM) or osteogenic medium (OM) and irradiated with 0, 2, 4, 8, or 16 Gray (Gy); and (2) three-dimensional (3D) hydrogel system was designed, loaded with VICs and exposed to 0, 4, or 16 Gy of radiation. In both models, a dose-dependent decrease in cell viability and proliferation was observed in CM and OM. Radiation exposure caused myofibroblast-like morphological changes and differentiation of VICs, as characterized by decreased αSMA expression. Calcification, as defined by increased alkaline phosphatase activity, was mostly present in the 2D irradiated VICs exposed to 4 Gy, while after exposure to higher doses VICs acquired a unique giant fibroblast-like cell morphology. Finally, matrix turnover was significantly affected by radiation exposure in the 3D irradiated VICs, as shown by decreased collagen staining and increased MMP-2 and MMP-9 activity.

Conclusions: The presented work demonstrates that radiation exposure enhances the calcific response in VICs, a hallmark of CAVD. In addition, high radiation exposure induces differentiation of VICs into a terminally differentiated giant-cell fibroblast. Further studies are essential to elucidate the underlying mechanisms of these radiation-induced valvular changes.

Integration of immunotherapy into adjuvant therapy for resected non-small-cell lung cancer: ALCHEMIST chemo-IO (ACCIO)

Non-small-cell lung cancer (NSCLC) causes significant mortality each year. After successful resection of disease stage IB (>4 cm) to IIIA (per AJCC 7), adjuvant platinum-based chemotherapy improves median overall survival and is the standard of care, but many patients still experience recurrence of disease. An adjuvant regimen with greater efficacy could substantially improve outcomes. Pembrolizumab, a programmed cell death-1 inhibitor, has become an important option in the treatment of metastatic NSCLC. ALCHEMIST is a clinical trial platform of the National Cancer Institute that includes biomarker analysis for resected NSCLC and supports therapeutic trials including A081801 (ACCIO), a three-arm study that will evaluate both concurrent chemotherapy plus pembrolizumab and sequential chemotherapy followed by pembrolizumab to standard of care adjuvant platinum-based chemotherapy.

Clinical trial registration: NCT04267848 (ClinicalTrials.gov)

Non-small-cell lung cancer adjuvant platinum-based therapy is standard of care (SOC). Including pembrolizumab may improve efficacy. A081801 (ACCIO) is a three-arm study: SOC versus sequential chemotherapy–pembrolizumab versus concurrent chemotherapy + pembrolizumab.

MMB-FOXM1-driven premature mitosis is required for CHK1 inhibitor sensitivity

To identify genes whose loss confers resistance to CHK1 inhibitors, we perform genome-wide CRISPR-Cas9 screens in non-small-cell lung cancer (NSCLC) cell lines treated with the CHK1 inhibitor prexasertib (CHK1i). Five of the top six hits of the screens, MYBL2 (B-MYB), LIN54, FOXM1, cyclin A2 (CCNA2), and CDC25B, are cell-cycle-regulated genes that contribute to entry into mitosis. Knockout of MMB-FOXM1 complex components LIN54 and FOXM1 reduce CHK1i-induced DNA replication stress markers and premature mitosis during Late S phase. Activation of a feedback loop between the MMB-FOXM1 complex and CDK1 is required for CHK1i-induced premature mitosis in Late S phase and subsequent replication catastrophe, indicating that dysregulation of the S to M transition is necessary for CHK1 inhibitor sensitivity. These findings provide mechanistic insights into small molecule inhibitors currently studied in clinical trials and provide rationale for combination therapies.

Branigan et al., by using genome-wide CRISPR screens, identify the MMB-FOXM1 complex as being required for CHK1 inhibitor (CHK1i) sensitivity. Their study shows that CHK1i-induced premature activation of the G2/M transcriptional program by this complex triggers a breakdown in the separation of DNA synthesis and mitosis, leading to replication catastrophe.

Phase I/II Study of Stereotactic Body Radiation Therapy for Pulmonary Metastases in Pediatric Patients

Purpose

Pulmonary metastases are common in many pediatric solid tumors; however, little is known about safety and efficacy of lung stereotactic body radiation therapy (SBRT) for pediatric patients. We conducted a phase I/II study to investigate the minimum effective dose level of SBRT with an acceptable safety profile in pediatric patients.

Methods and Materials

Patients with sarcoma and metastatic pulmonary lesions ≤3 cm in diameter and ≤21 years of age were enrolled. Dose levels 1, 2, and 3 were 24, 30, and 36 Gy in 3 fractions, respectively. Enrolled patients with metastases from primary renal tumors and sarcoma histologies were to begin at dose level 1 and 2, respectively. Exclusion criteria included receipt of whole-lung/hemi-thorax irradiation >12 Gy within 6 months of consent. Primary endpoints were tolerability and safety per Common Terminology Criteria for Adverse Events grading and disease response at 6 weeks post-SBRT per response evaluation criteria in solid tumors (RECIST) 1.1 criteria. Secondary endpoints included rates of local control and distant failure within the lung, but outside of the treatment volume.

Results

Five patients with median age of 13 years (range, 7-21) received SBRT at dose level 2. Primary tumor histologies included Ewing sarcoma (n = 3), anaplastic chordoma (n = 1), and osteosarcoma (n = 1). No grade ≥3 adverse events were observed. At 6 weeks after SBRT, 7/8 (87.5%) lesions achieved partial response. With median follow-up of 2.1 years (range, 1.4-2.5), 2-year local control and distant failure-free survival were 60% (n = 8) and 40% (n = 5), respectively. One patient developed widespread metastases and succumbed to disease 1.4 years after SBRT.

Conclusions

SBRT for pulmonary metastases produces responses in pediatric patients with sarcoma at 6 weeks with acceptable toxicity; however, patients remain at risk of local and distant failure within the lung. Future prospective studies are needed to investigate whether higher doses of SBRT, possibly in combination with other therapies, are safe and provide more durable response.

CHK1 Inhibitor Blocks Phosphorylation of FAM122A and Promotes Replication Stress

While effective anti-cancer drugs targeting the CHK1 kinase are advancing in the clinic, drug resistance is rapidly emerging. Here, we demonstrate that CRISPR-mediated knockout of the little-known gene FAM122A/PABIR1 confers cellular resistance to CHK1 inhibitors (CHK1is) and cross-resistance to ATR inhibitors. Knockout of FAM122A results in activation of PP2A-B55α, a phosphatase that dephosphorylates the WEE1 protein and rescues WEE1 from ubiquitin-mediated degradation. The resulting increase in WEE1 protein expression reduces replication stress, activates the G2/M checkpoint, and confers cellular resistance to CHK1is. Interestingly, in tumor cells with oncogene-driven replication stress, CHK1 can directly phosphorylate FAM122A, leading to activation of the PP2A-B55α phosphatase and increased WEE1 expression. A combination of a CHK1i plus a WEE1 inhibitor can overcome CHK1i resistance of these tumor cells, thereby enhancing anti-cancer activity. The FAM122A expression level in a tumor cell can serve as a useful biomarker for predicting CHK1i sensitivity or resistance.

Increased carcinoembryonic antigen expression on the surface of lung cancer cells using gold nanoparticles during radiotherapy

PURPOSE

Tumor-associated antigens are a promising target of immunotherapy approaches for cancer treatments but rely on sufficient expression of the target antigen. This study investigates the expression of the carcinoembryonic antigen (CEA) on the surface of irradiated lung cancer cells in vitro using gold nanoparticles as radio-enhancer.

METHODS

Human lung carcinoma cells A549 were irradiated and expression of CEA on the cell surface measured by flow cytometry 3 h, 24 h, and 72 h after irradiation to doses of 2 Gy, 6 Gy, 10 Gy, and 20 Gy in the presence or absence of 0.1 mg/ml or 0.5 mg/ml gold nanoparticles. CEA expression was measured as median fluorescent intensity and percentage of CEA-positive cells.

RESULTS

An increase in CEA expression was observed with both increasing radiation dose and time. There was doubling in median fluorescent intensity 24 h after 20 Gy irradiation and 72 h after 6 Gy irradiation. Use of gold nanoparticles resulted in additional significant increase in CEA expression. Change in cell morphology included swelling of cells and increased internal complexity in accordance with change in CEA expression.

CONCLUSIONS

This study showed an increase in CEA expression on human lung carcinoma cells following irradiation. Increase in expression was observed with increasing radiation dose and in a time dependent manner up to 72 h post irradiation. The results further showed that gold nanoparticles can significantly increase CEA expression following radiotherapy.

Author Correction: Image-guided radiotherapy platform using single nodule conditional lung cancer mouse models

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The impact of quantitative CT-based tumor volumetric features on the outcomes of patients with limited stage small cell lung cancer

INTRODUCTION

Limited stage small cell lung cancer (LS-SCLC) has a poor prognosis. Additional prognostic markers are needed for risk-stratification and treatment intensification. This study compares quantitative CT-based volumetric tumor measurements versus International Association for the Study of Lung Cancer (IASLC) TNM staging to predict outcomes.

MATERIALS & METHODS

A cohort of 105 patients diagnosed with LS-SCLC and treated with chemoradiation (CRT) from 2000 to 2013 were analyzed retrospectively. Patients were staged by the Union for International Cancer Control (UICC) TNM Classification, 8th edition. Tumor volumes and diameters were extracted from radiation planning CT imaging. Univariable and multivariable models were used to analyze relationships between CT features and overall survival (OS), locoregional recurrence (LRR), in-field LRR, any progression, and distant metastasis (DM).

RESULTS

Median follow-up was 21.3 months. Two-year outcomes were as follows: 38% LRR, 31% in-field LRR, 52% DM, 62% any progression, and 47% OS (median survival 16.5 months). On univariable analysis, UICC T-stage and N-stage were not associated with any clinical outcome. UICC overall stage was only statistically associated with in-field LRR. One imaging feature (3D maximum tumor diameter) was found to be significantly associated with LRR (HR 1.10, p = 0.003), in-field LRR (HR 1.10, p = 0.007), DM (HR 1.10, p = 0.02), any progression (HR 1.10, p = 0.008), and OS (HR 1.10, p = 0.03). On multivariable analysis, this feature remained significantly associated with all outcomes.

CONCLUSION

For LS-SCLC, quantitative CT-based volumetric tumor measurements were significantly associated with outcomes after CRT and may be better predictors of outcome than TNM stage.

Lipopolysaccharide-Binding Protein Is an Early Biomarker of Cardiac Function After Radiation Therapy for Breast Cancer

PURPOSE

To evaluate the prognostic potential of lipopolysaccharide-binding protein (LBP) levels after breast cancer radiation therapy (RT) for incipient cardiac dysfunction.

METHODS AND MATERIALS

In this single-centered study, we prospectively enrolled female patients treated for left breast cancer. Healthy age- and sex-matched participants were recruited as controls. LBP levels, cardiac troponin T, N-terminal propeptide of the brain natriuretic peptide, fatty acid binding protein, and C-reactive protein were assessed at three timepoints-before RT, after the last RT fraction, and 1 month after the last fraction. Echocardiographic evaluation was done 3 to 3.75 years after RT.

RESULTS

We recruited 51 patients and 78 controls. Baseline LBP concentrations in the study group were significantly higher than in controls at baseline (P < .001), at 24 hours, and at 1 month after RT (P = .003 and P < .001, respectively). Other biomarkers (cardiac troponin T, N-terminal propeptide of the brain natriuretic peptide, fatty acid binding protein, and C-reactive protein) did not differ in any of the timepoints. Posttreatment LBP concentrations were significantly and positively correlated with heart- and lung-associated dose-volume histogram variables. Posttreatment and follow-up LBP levels correlated positively with the E/E' echocardiographic index reflective of the diastolic function. After adjustment for left anterior descending artery mean dose, left ventricle mean dose, mean heart dose, and type of surgery, LBP remained significantly correlated with E/E' when measured 24 hours after RT (beta = 0.41, P = .032) and 1 month after RT (beta = 0.43, P = .028).

CONCLUSIONS

Serum LBP concentrations correlate with diastolic function evaluated 3 years after the completion of RT, making LBP a potentially useful prognostic parameter.

USP1 Is Required for Replication Fork Protection in BRCA1-Deficient Tumors

BRCA1-deficient tumor cells have defects in homologous-recombination repair and replication fork stability, resulting in PARP inhibitor sensitivity. Here, we demonstrate that a deubiquitinase, USP1, is upregulated in tumors with mutations in BRCA1. Knockdown or inhibition of USP1 resulted in replication fork destabilization and decreased viability of BRCA1-deficient cells, revealing a synthetic lethal relationship. USP1 binds to and is stimulated by fork DNA. A truncated form of USP1, lacking its DNA-binding region, was not stimulated by DNA and failed to localize and protect replication forks. Persistence of monoubiquitinated PCNA at the replication fork was the mechanism of cell death in the absence of USP1. Taken together, USP1 exhibits DNA-mediated activation at the replication fork, protects the fork, and promotes survival in BRCA1-deficient cells. Inhibition of USP1 may be a useful treatment for a subset of PARP-inhibitor-resistant BRCA1-deficient tumors with acquired replication fork stabilization.

Outcomes by EGFR, KRAS, and ALK Genotype After Combined Modality Therapy for Locally Advanced Non–Small-Cell Lung Cancer

Purpose

In 699 patients with locally advanced non–small-cell lung cancer (NSCLC) treated with radiation therapy as part of combined modality therapy, we compared outcomes among genotyped and ungenotyped patients and by tumor genotype status ( EGFR, KRAS, and ALK).

Patients and Methods

Genotyping was performed in 250 patients: EGFR+ (19%), KRAS+ (32%), ALK+ (9%), and wild type (WT−/−/−; 40%). Outcomes were analyzed using the Kaplan-Meier method and Cox regression.

Results

With a median follow-up of 48.2 months among genotyped patients, median overall survival (OS) was significantly longer for EGFR+ and ALK+ compared with KRAS+ and WT−/−/− (55.8 months v not reached v 28.0 v 33.2 months; P = .02). There was no difference in progression-free survival (median, 15.3 v 13.7 v 13.0 v 14.5 months; P = .47) or in freedom from distant metastases by genotype (3-year estimates: 42% v 49% v 27% v 25%; P = .25). There was higher freedom from locoregional recurrence (LRR) for EGFR+ tumors and lower freedom from LRR in ALK+ tumors, compared with KRAS+ and WT−/−/− tumors (3-year: 77% v 38% v 49% v 46%). In multivariable analysis, ALK+ remained associated with increased OS (HR, 0.32; 95% CI, 0.12 to 0.87; P = .03), and EGFR+ was associated with decreased LRR (HR, 0.47; 95% CI, 0.24 to 0.92; P = .03). Analysis of post-recurrence survival demonstrated that EGFR+/ ALK+ patients treated with appropriate tyrosine kinase inhibitors had higher OS compared with other groups.

Conclusion

In this series of locally advanced NSCLC treated with combined modality therapy, EGFR+ and ALK+ were associated with higher OS, whereas LRR was lower in EGFR+ patients, and the risk of distant metastases was high in all subgroups. The outcomes and patterns of failure in genotypic subgroups of NSCLC from this study can inform the design of future trials integrating targeted therapies.

Abstract 4287: Whole-genome CRISPR/Cas9 screen of the CHK1 inhibitor prexasertib implicates FAM122A loss as a potential resistance mechanism

Introduction: Phase I clinical trials of the CHK1 inhibitor prexasertib have been completed in non-small cell lung cancer (NSCLC) and other cancers and several Phase I-II trials are currently recruiting. By inhibiting the G2/M and S-phase checkpoints, prexasertib has been shown to cause increased replication stress, DNA damage and premature entry into mitosis, resulting in mitotic catastrophe and cell death. While the inhibitor is showing therapeutic promise, acquired resistance is of concern. Little is known about how cancer cells may become resistant to CHK1 inhibitors. Understanding potential resistance mechanisms may help predict patient responses, design CHK1 therapy combinations and implement means of re-sensitization.

Materials and Methods: NSCLC cell lines A549 and NCI-H460 stably expressing the Cas9 endonuclease were obtained from the Genetic Perturbation Platform at the Broad Institute. Cells were infected with the Brunello v2 lentiviral sgRNA library and grown for 15 days in prexasertib-treated media. Cells were collected pre- and post-drug selection, genomic DNA was extracted, and sgRNA sequences were PCR amplified and Illumina sequenced. Top hits among knockouts that conferred drug resistance were identified by the STARS gene-ranking algorithm. Hit validation was performed with sgRNAs and pooled siRNAs (Qiagen). Prexasertib IC50s were assessed by colony formation and CellTiter-Glo cell viability assays. Cell cycle analysis was performed by propidium iodide flow cytometry. PP2A activity was measured using Ser/Thr phosphatase assay kits (Upstate Biotechnology). Dinaciclib and LB-100 were obtained from Selleck and Apexbio, respectively.

Results: CRISPR knockouts of several individual genes were found to promote resistance of both cell lines to prexasertib with false discovery rates &lt; 0.01%. One top hit codes for a little-known but highly conserved protein FAM122A, which has been shown to inhibit PP2A, which dephosphorylates the Chk1 target protein CDC25C. SiRNA knockdown or sgRNA knockout of FAM122A conferred prexasertib resistance. Similarly, prexasertib-mediated G2/M accumulation was inhibited by FAM122A knockdown. FAM122A silencing increased PP2A activity. FAM122A knockdown mediated resistance was reversed with PP2A B subunit α siRNA knockdown or the PP2A inhibitor LB-100. Dinaciclib, an inhibitor of the CDC25C kinase CDK2, increased prexasertib resistance.

Conclusion: Although CHK1 inhibitors like prexasertib show promise, one mechanism of resistance may be through other cell-cycle regulating compensatory pathways. Identification of FAM122A loss as a potential mechanism for resistance suggests a predictive biomarker and means for re-sensitization of cancer cells to CHK1 inhibitors.

Citation Format: Peter Deraska, Hunter Reavis, Shelby Labe, Alan D'Andrea, David Kozono. Whole-genome CRISPR/Cas9 screen of the CHK1 inhibitor prexasertib implicates FAM122A loss as a potential resistance mechanism [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 4287.

Dual HDAC and PI3K Inhibition Abrogates NFκB- and FOXM1-Mediated DNA Damage Response to Radiosensitize Pediatric High-Grade Gliomas

Aberrant chromatin remodeling and activation of the PI3K pathway have been identified as important mediators of pediatric high-grade glioma (pHGG) and diffuse intrinsic pontine glioma (DIPG) pathogenesis. As inhibition of these pathways are promising therapeutic avenues and radiation is the only modality to prolong survival of patients with DIPG, we sought to explore radiosensitizing functions of such inhibition and to explore mechanisms of action of such agents. Here, we demonstrate that combined treatment with radiotherapy and CUDC-907, a novel first-in-class dual inhibitor of histone deacetylases (HDAC) and PI3K, evokes a potent cytotoxic response in pHGG and DIPG models. CUDC-907 modulated DNA damage response by inhibiting radiation-induced DNA repair pathways including homologous recombination and nonhomologous end joining. The radiosensitizing effects of CUDC-907 were mediated by decreased NFκB/Forkhead box M1 (FOXM1) recruitment to promoters of genes involved in the DNA damage response; exogenous expression of NFκB/FOXM1 protected from CUDC-907-induced cytotoxicity. Together, these findings reveal CUDC-907 as a novel radiosensitizer with potent antitumor activity in pHGG and DIPG and provide a preclinical rationale for the combination of CUDC-907 with radiotherapy as a novel therapeutic strategy against pHGG and DIPG. More globally, we have identified NFκB and FOXM1 and their downstream transcriptional elements as critical targets for new treatments for pHGG and DIPG.Significance: These findings describe the radiosensitizing effect of a novel agent in pediatric high-grade gliomas, addressing a critical unmet need of increasing the radiation sensitivity of these highly aggressive tumors. Cancer Res; 78(14); 4007-21. ©2018 AACR.

NF-κB inhibition by dimethylaminoparthenolide radiosensitizes non-small-cell lung carcinoma by blocking DNA double-strand break repair

Despite optimal chemotherapy, radiotherapy (RT), and/or surgery, non-small-cell lung carcinoma (NSCLC) remains the leading cause of cancer-related death in the US and worldwide. Thoracic RT, a mainstay in the treatment of locally advanced NSCLC, is often restricted in efficacy by a therapeutic index limited by sensitivity of tissues surrounding the malignancy. Therefore, radiosensitizers that can improve the therapeutic index are a vital unmet need. Inhibition of the NF-κB pathway is a proposed mechanism of radiosensitization. Here we demonstrate that inhibition of the canonical NF-κB pathway by dimethylaminoparthenolide (DMAPT) radiosensitizes NSCLC by blocking DNA double-strand break (DSB) repair. NF-κB inhibition results in significant impairment of both homologous recombination (HR) and non-homologous end joining (NHEJ), as well as reductions in ionizing radiation (IR)-induced DNA repair biomarkers. NF-κB inhibition by DMAPT shows preclinical potential for further investigation as a NSCLC radiosensitizer.

Use of frailty to predict survival in elderly patients with early stage non-small-cell lung cancer treated with stereotactic body radiation therapy

OBJECTIVES

Frailty has been shown to increase morbidity and mortality independent of age, but studies are lacking in radiation oncology. This study evaluates a modified frailty index (mFI) in predicting overall survival (OS) and non-cancer death for Stage I/II [N0M0] Non-Small-Cell Lung Cancer (NSCLC) patients treated with Stereotactic Body Radiation Therapy (SBRT).

MATERIALS AND METHODS

Medical records for all patients with Stage I/II NSCLC treated at our institution with SBRT from 2009 to 2014 were reviewed. A validated mFI score, consisting of 11 variables was calculated, classifying patients as non-frail (0-1) or frail (≥2). Primary endpoint (OS) was analyzed using Kaplan-Meier method and log-rank. Secondary endpoint, non-cancer death, was analyzed using Fine-Gray's method, with death from lung cancer as a competing risk.

RESULTS

Patient cohort consisted of 38 (27.3%) non-frail and 101 (72.7%) frail [median total mFI score 3.0 (range 0-7)]. Median age and pack-year history was 74 and 46years, respectively. Median follow-up among survivors was 38.5months (range 4.0-74.1months). Frailty was associated with a lower 3-year OS (37.3% vs. 74.7%; p=0.003) and 3-year cumulative incidence of non-cancer death (36.7% vs. 12.5%; p=0.02). Frailty remained significant in the multivariate model [OS HR for mFI ≥2: 2.25 (1.14-4.44); p=0.02].

CONCLUSION

Frailty is associated with lower OS in older patients with early stage NSCLC treated with SBRT, yet frail patients survived a median 2.5years, and were more likely to die of causes unrelated to the primary lung cancer, suggesting SBRT should be considered even in older patients deemed unfit for surgery.

Abstract 4189: Homologous recombination pathway-based biomarkers for treatment of non-small cell lung cancer with PARP inhibitors

Introduction: Clinical trials examining the addition of PARP inhibitors (PARPi) to treatment regimens for non-small cell lung cancer (NSCLC) are underway. Of note, these trials are not biomarker driven, and so any benefit may be obscured due to heterogeneity of tumor responses. The first FDA approved PARPi, olaparib, was approved specifically for ovarian cancer patients with germline mutations in BRCA1 or 2. These patients have tumors that show homologous recombination deficiency (HRD), a DNA damage repair pathway defect that confers synthetic lethality in the setting of PARPi therapy. Whether HRD may serve a biomarker for PARPi sensitivity in NSCLC, however, is unclear.

Materials and Methods: Based on prior studies, NSCLC cell lines were classified as 1) HR proficient (A549, NCI-H23, NCI-H460, NCI-H522, NCI-H1299), 2) HR deficient due to early defects in the pathway as evidenced by decreased cisplatin-induced RAD51 focus formation (NCI-H1563, NCI-H1915, NCI-H2087, NCI-H2126) or 3) HR deficient due to late defects in the pathway as evidenced by impaired resolution of ionizing radiation (IR) induced RAD51 and γ-H2AX foci (Calu-1, Calu-6, HCC827, NCI-H520, SK-LU-1). NSCLC cells expressing doxycycline-inducible BRCA1 or 2 shRNA were generated by Tet-pLKO-puro lentiviral transduction. Cell viability assays to determine olaparib IC50 values were performed using CellTiter-Glo and MTS. Gene expression data were extracted from published datasets including CCLE, GSE32665 and TCGA, and expression levels of select genes were assayed by RT-qPCR.

Results: BRCA1/2 shRNA knockdown inhibited IR-induced RAD51 focus formation in HR proficient NSCLC cells. This also induced PARPi sensitivity (A549 olaparib IC50 63 µM -&gt; 1.2 µM with BRCA1 and 18 µM -&gt; 3.4 µM with BRCA2 knockdown). Because BRCA alterations are uncommon in NSCLC, however, other HRD biomarkers were explored. There was no statistically significant difference in PARPi sensitivity among cell lines grouped by cisplatin-induced RAD51 focus formation or resolution of IR-induced RAD51 or γ-H2AX foci. BRCA deficient breast and ovarian cancers overexpress POLQ, which drives DNA repair toward non-HR-dependent pathways including alternative end joining. Like these cancers, NSCLC tumors overexpressed POLQ and RAD54L compared to normal lung, p &lt; 0.001. Expression of these two genes correlated highly in multiple datasets, e.g., r² = 0.69 and p &lt; 0.001 in TCGA adenocarcinomas. High RAD54L expression tended to correlate with low olaparib IC50 values, r = -0.56, p = 0.059. NCI-H1299 and SK-LU-1, which showed the highest RAD54L expression, also showed the highest olaparib sensitivity.

Conclusion: Although certain HRD biomarkers including RAD51 focus formation and impaired resolution did not predict NSCLC olaparib sensitivity, other potential biomarkers, such as BRCA1/2 loss of function and elevated RAD54L expression, may serve as potential HRD-related biomarkers.

Citation Format: Peter V. Deraska, Hunter D. Reavis, Shelby Labe, Alan D. D'Andrea, David Kozono. Homologous recombination pathway-based biomarkers for treatment of non-small cell lung cancer with PARP inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4189. doi:10.1158/1538-7445.AM2017-4189

Abstract 3100: Nanoformulated Talazoparib and Olaparib for enhanced delivery

Introduction: PARP inhibitors such as Talazoparib and Olaparib exploit deficiencies in DNA repair pathways, making them attractive candidates for treatment of a number of different cancers. These drugs are particularly effective when used in combination with other DNA damaging agents such as chemotherapeutics and radiation therapy. Combination trials, however, have resulted in severe toxicities, necessitating either dose reduction or delay. Dose reduction leads to suboptimal dosing and provides little therapeutic benefit compared to monotherapy. Systemically administered nanoparticles offer a more effective way to selectively accumulate drugs in tumors and bypass toxicities associated with oral delivery. We have developed nanoparticle delivery systems for both Olaparib and Talazoparib in order to improve tumor accumulation while bypassing the toxicity associated with oral administration.

Methods: Lipid nanoformulations of Olaparib and Talazoparib have been developed and characterized in regard to size, surface charge, drug loading, release, and stability. NanoTalazoparib has been tested in vitro in breast cancer cell lines including W0069, W780, and HCC1937 which exhibit BRCA1 and 2 mutations, and NanoOlaparib in the lung cancer cell line Calu-6 which also has a defective FA-BRCA pathway. Mice have been treated with NanoOlaparib and NanoTalazoparib alone and in combination with radiation or temozolomide in order to evaluate toxicity. Therapeutic efficacy studies are currently underway.

Results: The nanoformulations have been formulated to encapsulate a clinically relevant dose of either Talazoparib or Olaparib and release at 37°C over a period of days, while remaining stable during storage at 4°C. In vitro, both nanoformulations show the same activity as free drug with IC50s in the nanomolar range for these cell lines with varying deficiencies in the BRCA pathway. Mice have shown no appreciable weight loss during treatment with either nanoformulation alone or in combination with other treatment modalities.

Conclusion: Nanoformulations of Talazoparib and Olaparib have been developed and characterized to demonstrate activity in vitro and tolerable doses in vivo. We have found that mice tolerate NanoTalazoparib at higher doses when combined with Temozolomide than when given oral Talazoparib. The sustained release from the nanoparticles allows for the nanoformulation to be administered less often than the daily administration for oral drug and the improved tolerability opens the door for combination therapy with both chemotherapeutics and radiation therapy. Therapeutic efficacy studies are underway and we expect that as a monotherapy NanoTalazoparib will be more effective at lower doses than oral Talazoparib, based on the longer circulation time and more selective accumulation in tumors. We also anticipate that combination therapy will be more effective with the nanoformulation, as the maximum tolerated dose is higher than that of the oral drug.

Citation Format: Paige Baldwin, Rajiv Kumar, Edward Favours, Karen Liby, Raushan Kurmasheva, David Kozono, Srinivas Sridhar. Nanoformulated Talazoparib and Olaparib for enhanced delivery [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3100. doi:10.1158/1538-7445.AM2017-3100

Lymph node volume predicts survival but not nodal clearance in Stage IIIA-IIIB NSCLC

BACKGROUND

Locally advanced non-small cell lung cancer (LA-NSCLC) patients have poorer survival and local control with mediastinal node (N2) tumor involvement at resection. Earlier assessment of nodal burden could inform clinical decision-making prior to surgery. This study evaluated the association between clinical outcomes and lymph node volume before and after neoadjuvant therapy.

MATERIALS AND METHODS

CT imaging of patients with operable LA-NSCLC treated with chemoradiation and surgical resection was assessed. Clinically involved lymph node stations were identified by FDG-PET or mediastinoscopy. Locoregional recurrence (LRR), distant metastasis (DM), progression free survival (PFS) and overall survival (OS) were analyzed by the Kaplan Meier method, concordance index and Cox regression.

RESULTS

73 patients with Stage IIIA-IIIB NSCLC treated with neoadjuvant chemoradiation and surgical resection were identified. The median RT dose was 54 Gy and all patients received concurrent chemotherapy. Involved lymph node volume was significantly associated with LRR and OS but not DM on univariate analysis. Additionally, lymph node volume greater than 10.6 cm3 after the completion of preoperative chemoradiation was associated with increased LRR (p<0.001) and decreased OS (p = 0.04). There was no association between nodal volumes and nodal clearance.

CONCLUSION

For patients with LA-NSCLC, large volume nodal disease post-chemoradiation is associated with increased risk of locoregional recurrence and decreased survival. Nodal volume can thus be used to further stratify patients within the heterogeneous Stage IIIA-IIIB population and potentially guide clinical decision-making.

Abstract 1650: Whole-genome RNAi screen identified BCAS1 as a novel modifier of non-small cell lung carcinoma radioresistance

Introduction: Despite optimal chemotherapy, radiotherapy and/or surgery, non-small cell lung carcinoma (NSCLC) remains the leading cause of cancer-related death in the United States. Therefore, there is a need for agents, such as radiosensitizers, that can improve the efficacy of current therapies. Using a whole-genome shRNA screen, we sought to identify and characterize novel gene products that may be involved in NSCLC radioresistance. We hypothesize that these proteins may represent novel targets for NSCLC radiosensitization.

Materials and Methods: A whole-genome pooled retroviral shRNA screen was performed using the Hannon-Elledge library of 74,705 distinct shRNAs directed against over 18,000 genes, to identify gene knockdowns that showed cytotoxicity only in cells treated with fractionated radiation given daily Monday-Friday. To confirm targets identified in the whole-genome screen, we treated A549 and NCI-H460 NSCLC cells with siRNAs targeted against the genes of interest and assessed cell viability following irradiation using the CellTiter-Glo assay and clonogenic survival assays.

Results: We identified six novel genes (BCAS1, c7orf24, CDC45L, KIAA0101, TCN1 and TNC) whose knockdown sensitized NSCLC cells to radiation. Of the six genes, siRNA knockdown of BCAS1 showed the most consistent increases in sensitivity to ionizing radiation. Analysis of cell viability following radiation revealed that BCAS1 knockdown resulted in a 50% additional decrease in cell viability in A549 and NCI-H460 cells following 8 and 4 Gy of ionizing radiation, respectively. We confirmed these results by clonogenic survival assays. To assess for tumor-specific expression in NSCLC, we compared expression data between matched normal tissue and NSCLC biopsy samples and found that BCAS1 is substantially more highly expressed in tumor tissues. Examination of affinity capture-mass spectroscopy data suggested that BCAS1 interacts with RUVBL2, a RuvB-like AAA ATPase, which has known functions in DNA damage and repair.

Conclusions: BCAS1 emerged from a whole-genome RNAi screen as a potential target for improving the efficacy of radiotherapy in NSCLC. We demonstrated that BCAS1 is overexpressed in tumor tissues compared to normal lung, and that its knockdown consistently sensitizes NSCLC cell lines to radiation, validating the screen hit. Ongoing work suggests that BCAS1 may modulate DNA damage repair. Further studies to understand the mechanism by which BCAS1 is involved in radioresistance are necessary.

Citation Format: Colin O’Leary, Peter Deraska, Alan D’Andrea, David Kozono. Whole-genome RNAi screen identified BCAS1 as a novel modifier of non-small cell lung carcinoma radioresistance. [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 1650.

Abstract 1644: NF-κB inhibitor DMAPT blocks non-homologous end-joining repair of radiation-induced DSBs in NSCLC

Background: Despite optimal multimodality therapy, non-small cell lung carcinoma (NSCLC) remains the leading cause of cancer-related death in the United States. A common limitation is our inability to provide sufficient radiotherapy (RT) to eradicate tumor due to risk of toxicities in surrounding tissues. There is thus an unmet need for radiosensitizers that can improve the therapeutic index. Dimethylaminoparthenolide (DMAPT), an orally bioavailable small molecule NF-κB inhibitor, inhibits repair of ionizing radiation (IR)-induced DNA double strand breaks (DSBs) and increases control of subcutaneous mouse NSCLC xenografts. While our prior work focused on inhibition of homologous recombination as a mechanism for radiosensitization, we sought to characterize the effect of DMAPT on a second major DSB repair pathway, non-homologous end-joining (NHEJ).

Methods: NHEJ was assessed in NSCLC lines using the pEJ reporter and flow cytometry. The NF-κB super repressor (IκBαS32A,S36A) was used as a control. Immunofluorescence and Western blotting were used to assess NHEJ biomarkers including 53BP1, DNA-PKS2056, Ku70/80 and XRCC4. Cell fractionation was performed to assess Ku chromatin binding. Quantitative RT-PCR was performed to assess gene transcription. Ku complexes were purified to identify binding partners.

Results: NSCLC cells treated with IR-sensitizing doses of DMAPT (5-15 μM) or the NF-κB super repressor showed significant decreases in NHEJ. DMAPT increased the persistence of 53BP1 foci, indicating a failure to complete NHEJ. Regardless of exogenous DNA damage, there was reduced Ku70 chromatin binding following DMAPT treatment. DMAPT-treated cells produced fewer distinct IR-induced DNA-PKS2056 foci. Further, there was decreased IR-induced XRCC4 chromatin recruitment, suggesting that repair was impaired prior to ligation. There was no change in Ku70/80 transcription following DMAPT and/or IR. However, Western blotting of purified Ku complexes showed that DMAPT treatment decreased Ku association with RNA binding partners including RPL19. We also observed decreased recruitment of DNA-PKcs to the Ku complex, suggesting decreased Ku affinity for DSBs.

Conclusions: These results indicate that DMAPT radiosensitizes NSCLC by perturbing the binding affinity of Ku to RNA, DNA and its complex binding partners, thus blocking NHEJ. Further mechanistic investigation and analysis of NHEJ biomarkers in vivo is needed to identify the precise mechanism.

Citation Format: Peter V. Deraska, Colin O’Leary, Jean-Bernard Lazaro, Christopher J. Sweeney, Alan D. D’Andrea, David Kozono. NF-κB inhibitor DMAPT blocks non-homologous end-joining repair of radiation-induced DSBs in NSCLC. [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 1644.

FANCD2 Maintains Fork Stability in BRCA1/2-Deficient Tumors and Promotes Alternative End-Joining DNA Repair

BRCA1/2 proteins function in homologous recombination (HR)-mediated DNA repair and cooperate with Fanconi anemia (FA) proteins to maintain genomic integrity through replication fork stabilization. Loss of BRCA1/2 proteins results in DNA repair deficiency and replicative stress, leading to genomic instability and enhanced sensitivity to DNA-damaging agents. Recent studies have shown that BRCA1/2-deficient tumors upregulate Polθ-mediated alternative end-joining (alt-EJ) repair as a survival mechanism. Whether other mechanisms maintain genomic integrity upon loss of BRCA1/2 proteins is currently unknown. Here we show that BRCA1/2-deficient tumors also upregulate FANCD2 activity. FANCD2 is required for fork protection and fork restart in BRCA1/2-deficient tumors. Moreover, FANCD2 promotes Polθ recruitment at sites of damage and alt-EJ repair. Finally, loss of FANCD2 in BRCA1/2-deficient tumors enhances cell death. These results reveal a synthetic lethal relationship between FANCD2 and BRCA1/2, and they identify FANCD2 as a central player orchestrating DNA repair pathway choice at the replication fork.

Circulating miR-29a and miR-150 correlate with delivered dose during thoracic radiation therapy for non-small cell lung cancer

Background

Risk of normal tissue toxicity limits the amount of thoracic radiation therapy (RT) that can be routinely prescribed to treat non-small cell lung cancer (NSCLC). An early biomarker of response to thoracic RT may provide a way to predict eventual toxicities—such as radiation pneumonitis—during treatment, thereby enabling dose adjustment before the symptomatic onset of late effects. MicroRNAs (miRNAs) were studied as potential serological biomarkers for thoracic RT. As a first step, we sought to identify miRNAs that correlate with delivered dose and standard dosimetric factors.

Methods

We performed miRNA profiling of plasma samples obtained from five patients with Stage IIIA NSCLC at five dose-points each during radical thoracic RT. Candidate miRNAs were then assessed in samples from a separate cohort of 21 NSCLC patients receiving radical thoracic RT. To identify a cellular source of circulating miRNAs, we quantified in vitro miRNA expression intracellularly and within secreted exosomes in five NSCLC and stromal cell lines.

Results

miRNA profiling of the discovery cohort identified ten circulating miRNAs that correlated with delivered RT dose as well as other dosimetric parameters such as lung V20. In the validation cohort, miR-29a-3p and miR-150-5p were reproducibly shown to decrease with increasing radiation dose. Expression of miR-29a-3p and miR-150-5p in secreted exosomes decreased with radiation. This was concomitant with an increase in intracellular levels, suggesting that exosomal export of these miRNAs may be downregulated in both NSCLC and stromal cells in response to radiation.

Conclusions

miR-29a-3p and miR-150-5p were identified as circulating biomarkers that correlated with delivered RT dose. miR-150 has been reported to decrease in the circulation of mammals exposed to radiation while miR-29a has been associated with fibrosis in the human heart, lungs, and kidneys. One may therefore hypothesize that outlier levels of circulating miR-29a-3p and miR-150-5p may eventually help predict unexpected responses to radiation therapy, such as toxicity.

Electronic supplementary material

The online version of this article (doi:10.1186/s13014-016-0636-4) contains supplementary material, which is available to authorized users.

USP9X inhibition promotes radiation-induced apoptosis in non-small cell lung cancer cells expressing mid-to-high MCL1

BACKGROUND AND PURPOSE

Radiotherapy (RT) is vital for the treatment of locally advanced non-small cell lung cancer (NSCLC), yet its delivery is limited by tolerances of adjacent organs. We sought therefore to identify and characterize gene targets whose inhibition may improve RT.

MATERIALS AND METHODS

Whole genome pooled shRNA cytotoxicity screens were performed in A549 and NCI-H460 using a retroviral library of 74,705 sequences. Cells were propagated with or without daily radiation Monday-Friday. Radiosensitization by top differential dropout hits was assessed by clonogenic assays. Apoptosis was assessed using a caspase 3/7 cell-based activity assay and by annexin V-FITC and PI staining. MCL1 expression was assessed by qPCR and Western blotting.

RESULTS

USP9X, a deubiquitinase, was a top hit among druggable gene products. WP1130, a small molecule USP9X inhibitor, showed synergistic cytotoxicity with IR. MCL1, an anti-apoptotic protein deubiquitinated by USP9X, decreased with USP9X inhibition and IR. This was accompanied by increases in caspase 3/7 activity and apoptosis. In a panel of NSCLC lines, MCL1 and USP9X protein and gene expression levels were highly correlated. Lines showing high levels of MCL1 expression were the most sensitive to USP9X inhibition.

CONCLUSIONS

These data support the use of MCL1 expression as a predictive biomarker for USP9X inhibitors in NSCLC therapy.

Systemic Immune Response to Vaccination on FDG-PET/CT

A patient with newly diagnosed right lung cancer had transient ¹⁸F-fluorodeoxyglucose (FDG)-avid left axillary lymph nodes and intense splenic FDG uptake on positron emission tomography (PET)/computed tomography (CT). History revealed that the patient received a left-sided influenza vaccine 2-3 days before the examination. Although inflammatory FDG uptake in ipsilateral axillary nodes is reported, to our knowledge, this is the first report of visualization of the systemic immune response in the spleen related to the influenza vaccination on FDG-PET/CT. The history, splenic uptake and time course on serial FDG-PET/CT helped to avoid a false-positive interpretation for progressing lung cancer and alteration of the radiation therapy plan.

Abstract PR02: Dynamic epigenetic regulation of glioblastoma tumorigenicity through a LSD1-MYC-OLIG2 axis

Glioblastoma is one of the most devastating of human cancers, with near-uniform fatality within two years of diagnosis. Therapeutic failure is thought to be related to small subpopulation of cells that exhibit the properties of self-renewal and tumorigenicity. Understanding how such subpopulations attain and retain these properties remains a central question in oncology. One fundamental issue is whether tumorigenicity exists within a static population of elite cells or whether the capacity is stochastically acquired. To test these models, we assayed the tumorigenicity of single-cell subclones derived from long-terms passaged and primary patient-derived xenograft (PDX) glioblastoma lines. Our findings were best described by a hybrid model that is largely deterministic (elite) but with opportunities for dynamic (stochastic) interchange between non-tumorigenic and tumorigenic states. To identify molecular determinants of tumorigenicity, we performed gene expression profiling of the subclones. Analysis of the data suggested that tumorigenicity in glioblastoma is a dynamic property driven by variation in MYC expression, which in turn regulates Olig2 expression, a neural stem cell marker. Ectopic expression of MYC conferred tumorigenicty and MYC silencing abolished tumorigenicity in vitro and in vivo for multiple PDX and GEMM models. Transition between tumorigenic and non-tumorigenic cell states was associated with changes in histone modification at the MYC locus mediated by expression of lysine-specific demethylase 1 (LSD1). The model suggests a critical LSD1-MYC-OLIG2 axis that regulates the dynamic transition between glioblastoma cell states of differing tumorigenicity and unveils a novel framework for glioblastoma therapeutic development.

Citation Format: Clark Chen, David Kozono, Jie Li, Masayuki Nitta, Oltea Sampetrean, Kimberly Ng, David Gonda, Deepa S. Kushwaha, Dmitry Merzon, Valya Ramakrishnan, Shan Zhu, Kaya Zhu, Hiroko Matsui, Olivier Harismendy, Wei Hua, Ying Mao, Chang-Hyuk Kwon, Keith L. Ligon, Hideyuki Saya, Bob S. Carter, Donald P. Pizzo, Scott R. VandenBerg, Frank Furnari, Webster Cavenee. Dynamic epigenetic regulation of glioblastoma tumorigenicity through a LSD1-MYC-OLIG2 axis. [abstract]. In: Proceedings of the AACR Special Conference on Myc: From Biology to Therapy; Jan 7-10, 2015; La Jolla, CA. Philadelphia (PA): AACR; Mol Cancer Res 2015;13(10 Suppl):Abstract nr PR02.

Abstract 3336: NF-κB inhibition by DMAPT radiosensitizes non-small cell lung carcinoma by impairing DNA double strand break repair

Background: Despite optimal radiation therapy (RT), chemotherapy and/or surgery, non-small cell lung carcinoma (NSCLC) remains the leading cause of cancer-related death in the United States. Previously, we demonstrated that proteasome inhibition blocks the expression of Fanconi anemia/homologous recombination (FA/HR) genes via inhibition of the NF-κB pathway. Dimethylaminoparthenolide (DMAPT) is a water-soluble analog of parthenolide that has been shown to decrease p65/p50 heterodimer DNA binding. We hypothesized that DMAPT may radiosensitize NSCLC cells by impairing NF-κB-mediated expression of DNA double strand break (DSB) repair genes.

Materials and Methods: Cytotoxicity and radiosensitivity were assessed using clonogenic assays. IκB kinase (IKK) activity was measured using a substrate phosphorylation assay. HR and canonical non-homologous end joining (cNHEJ) were measured using A549 cells stably expressing reporter constructs that express GFP upon repair of I-SceI-induced DNA DSBs. DNA damage and DSB repair biomarker foci were assessed by immunofluorescence. For in vivo studies, 1×106 A549 cells were injected subcutaneously into the flanks of NCr nude mice. Once tumors reached an average size of 200 mm3, mice were treated concurrently with vehicle or DMAPT (100 mg/kg) ± focal ionizing radiation (4 Gy x 5) using a small animal radiation research platform (SAARP). Tumor growth was followed for three months following treatment.

Results: Radiation and NF-κB inhibition with DMAPT showed synergistic cytotoxicity. Treatment of A549 cells with DMAPT resulted in a decrease in constitutive IκBα phosphorylation by IKK. NF-κB inhibition via DMAPT resulted in a 60-70% decrease in HR. In addition, treatment with DMAPT resulted in ≥80% loss of IR-induced BRCA1, FANCD2, and RAD51 foci. NF-κB inhibition with either DMAPT or overexpression of the NF-κB super-repressor IκBα(S32A, S36A) resulted in a 50-70% decrease in cNHEJ. Treatment with DMAPT resulted in the loss of IR-induced phosphoDNA-PKS2056 foci. Further, treatment with DMAPT resulted in the persistence of radiation-induced γH2AX foci over a 24 hour period (100% of DMAPT treated cells showing foci compared to 30% of vehicle treated cells). Compared to either single agent DMAPT or IR alone, combined treatment of A549 xenografts with DMAPT and IR prevented tumor growth over three months (p &lt; 0.0001).

Conclusions: DMAPT inhibits NF-κB signaling by inhibiting IKK. This in turn inhibits HR and cNHEJ by preventing the recruitment of DNA repair proteins to sites of IR-induced DNA damage. Both in vitro and in vivo experiments show support for further evaluation of DMAPT as a NSCLC radiosensitizer.

Citation Format: Colin O'Leary, Peter Deraska, Christopher Sweeney, Alan D'Andrea, David Kozono. NF-κB inhibition by DMAPT radiosensitizes non-small cell lung carcinoma by impairing DNA double strand break repair. [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 3336. doi:10.1158/1538-7445.AM2015-3336