Transitioning to Neoadjuvant Therapy for Resectable Non-Small Cell Lung Cancer: Trends and Surgical Outcomes in a Regionalized Pulmonary Oncology Network

BACKGROUND

Several regulatory agencies have approved the use of the neoadjuvant chemo-immunotherapy for resectable stage II and III of non-small cell lung cancer (NSCLC) and numerous trials investigating novel agents are underway. However, significant concerns exist around the feasibility and safety of offering curative surgery to patients treated within such pathways. The goal in this study was to evaluate the impact of a transition towards a large-scale neoadjuvant therapy program for NSCLC.

METHODS

Medical charts of patients with clinical stage II and III NSCLC who underwent resection from January 2015 to December 2020 were reviewed. The primary outcome was perioperative complication rate between neoadjuvant-treated versus upfront surgery patients. Multivariable logistic regression estimated occurrence of postoperative complications and overall survival was assessed as an exploratory secondary outcome by Kaplan-Meier and Cox-regression analyses.

RESULTS

Of the 428 patients included, 106 (24.8%) received neoadjuvant therapy and 322 (75.2%) upfront surgery. Frequency of minor and major postoperative complications was similar between groups (P = .22). Occurrence in postoperative complication was similar in both cohort (aOR = 1.31, 95% CI 0.73-2.34). Neoadjuvant therapy administration increased from 10% to 45% with a rise in targeted and immuno-therapies over time, accompanied by a reduced rate of preoperative radiation therapy use. 1-, 2-, and 5-year overall survival was higher in neoadjuvant therapy compared to upfront surgery patients (Log-Rank P = .017).

CONCLUSIONS

No significant differences in perioperative outcomes and survival were observed in resectable NSCLC patients treated by neoadjuvant therapy versus upfront surgery. Transition to neoadjuvant therapy among resectable NSCLC patients is safe and feasible from a surgical perspective.

Canagliflozin mediates tumor suppression alone and in combination with radiotherapy in non-small cell lung cancer (NSCLC) through inhibition of HIF-1α

Non-small cell lung cancer (NSCLC) has a poor prognosis, and effective therapeutic strategies are lacking. The diabetes drug canagliflozin inhibits NSCLC cell proliferation and the mammalian target of rapamycin (mTOR) pathway, which mediates cell growth and survival, but it is unclear whether this drug can enhance response rates when combined with cytotoxic therapy. Here, we evaluated the effects of canagliflozin on human NSCLC response to cytotoxic therapy in tissue cultures and xenografts. Ribonucleic acid sequencing (RNA-seq), real-time quantitative PCR (RT-qPCR), metabolic function, small interfering ribonucleic acid (siRNA) knockdown, and protein expression assays were used in mechanistic analyses. We found that canagliflozin inhibited proliferation and clonogenic survival of NSCLC cells and augmented the efficacy of radiotherapy to mediate these effects and inhibit NSCLC xenograft growth. Canagliflozin treatment alone moderately inhibited mitochondrial oxidative phosphorylation and exhibited greater antiproliferative capacity than specific mitochondrial complex-I inhibitors. The treatment downregulated genes mediating hypoxia-inducible factor (HIF)-1α stability, metabolism and survival, activated adenosine monophosphate-activated protein kinase (AMPK) and inhibited mTOR, a critical activator of hypoxia-inducible factor-1α (HIF-1α) signaling. HIF-1α knockdown and stabilization experiments suggested that canagliflozin mediates antiproliferative effects, in part, through suppression of HIF-1α. Transcriptional regulatory network analysis pinpointed histone deacetylase 2 (HDAC2), a gene suppressed by canagliflozin, as a key mediator of canagliflozin's transcriptional reprogramming. HDAC2 knockdown eliminated HIF-1α levels and enhanced the antiproliferative effects of canagliflozin. HDAC2-regulated genes suppressed by canagliflozin are associated with poor prognosis in several clinical NSCLC datasets. In addition, we include evidence that canagliflozin also improves NSCLC response to chemotherapy. In summary, canagliflozin may be a promising therapy to develop in combination with cytotoxic therapy in NSCLC.

Stereotactic ablative radiotherapy before resection to avoid delay for early-stage lung cancer or oligometastases during the COVID-19 pandemic: Pathologic outcomes from the SABR-BRIDGE protocol

BACKGROUND

During coronavirus disease 2019 (COVID-19)-related operating room closures, some multidisciplinary thoracic oncology teams adopted a paradigm of stereotactic ablative radiotherapy (SABR) as a bridge to surgery, an approach called SABR-BRIDGE. This study presents the preliminary surgical and pathological results.

METHODS

Eligible participants from four institutions (three in Canada and one in the United States) had early-stage presumed or biopsy-proven lung malignancy that would normally be surgically resected. SABR was delivered using standard institutional guidelines, with surgery >3 months following SABR with standardized pathologic assessment. Pathological complete response (pCR) was defined as absence of viable cancer. Major pathologic response (MPR) was defined as ≤10% viable tissue.

RESULTS

Seventy-two patients underwent SABR. Most common SABR regimens were 34 Gy/1 (29%, n = 21), 48 Gy/3-4 (26%, n = 19), and 50/55 Gy/5 (22%, n = 16). SABR was well-tolerated, with one grade 5 toxicity (death 10 days after SABR with COVID-19) and five grade 2-3 toxicities. Following SABR, 26 patients underwent resection thus far (13 pending surgery). Median time-to-surgery was 4.5 months post-SABR (range, 2-17.5 months). Surgery was reported as being more difficult because of SABR in 38% (n = 10) of cases. Thirteen patients (50%) had pCR and 19 (73%) had MPR. Rates of pCR trended higher in patients operated on at earlier time points (75% if within 3 months, 50% if 3-6 months, and 33% if ≥6 months; p = .069). In the exploratory best-case scenario analysis, pCR rate does not exceed 82%.

CONCLUSIONS

The SABR-BRIDGE approach allowed for delivery of treatment during a period of operating room closure and was well-tolerated. Even in the best-case scenario, pCR rate does not exceed 82%.

Targeted Intraoperative Radiation Therapy during Breast-Conserving Surgery for Patients with Early Stage Breast Cancer: A Phase II Single Center Prospective Trial

Purpose

Patients with early stage breast cancer (ESBC) are conventionally treated with breast-conserving surgery (BCS) followed by whole-breast external beam radiation therapy (EBRT). The emergence of targeted intraoperative radiation therapy (TARGIT) with Intrabeam has been used as a therapeutic alternative for patients with risk-adapted ESBC. Here we present our radiation therapy toxicities (RTT), postoperative complications (PC), and short-term outcomes of the prospective phase II trial at the McGill University Health Center.

Methods and Materials

Patients aged ≥50 years with biopsy-proven hormone receptor-positive, grade 1 or 2, invasive ductal carcinoma of the breast, cT1N0, were eligible for the study. Enrolled patients underwent BCS followed by immediate TARGIT of 20 Gy in 1 fraction. Upon final pathology, patients with low-risk breast cancer (LRBC) received no further EBRT, and those with high-risk breast cancer (HRBC) received further 15 to 16 fractions of whole breast EBRT. HRBC criteria included pathologic tumor size >2 cm, grade 3, positive lympho-vascular invasion, multifocal disease, close margins (<2 mm), or positive nodal disease.

Results

A total of 61 patients with ESBC were enrolled in the study; upon final pathology, 40 (65.6%) had LRBC, and 21 (34.4%) had HRBC. The median follow-up was 3.9 years. The most common HRBC criteria were close margins in 66.6% (n = 14) and lymphovascular invasion in 28.6% (n = 6). No grade 4 RTT were observed in either group. The most common PC were seroma and cellulitis for both groups. The rate of locoregional recurrence was 0% in both groups. The overall survival in LRBC was 97.5% and in HRBC 95.2% with no significant differences. Deaths were nonbreast cancer related.

Conclusions

In patients with ESBC undergoing BCS, the use of TARGIT shows low rates of RTT and PC complications. Moreover, our short-term outcomes show no significant difference at 3.9 years median follow-up for locoregional recurrence or overall survival between groups of patients receiving TARGIT alone or TARGIT followed by EBRT. Of all patients, 34.4% required further EBRT, most commonly due to close margins.

Use of radiation therapy among patients with Extensive-stage Small-cell lung cancer receiving Immunotherapy: Canadian consensus recommendations

OBJECTIVES

Thoracic radiation therapy (TRT) and prophylactic cranial irradiation (PCI) are commonly used in the management of extensive-stage small-cell lung cancer (ES-SCLC); however, Phase III trials of first-line immunotherapy often excluded these options. Guidance is needed regarding appropriate use of TRT, PCI, and magnetic resonance imaging (MRI) surveillance while new data are awaited.

MATERIALS AND METHODS

In two web-based meetings, a pan-Canadian expert working group of five radiation oncologists and four medical oncologists addressed eight clinical questions regarding use of radiation therapy (RT) and MRI surveillance among patients with ES-SCLC receiving immunotherapy. A targeted literature review was conducted using PubMed and conference proceedings to identify recent (January 2019-April 2022) publications in this setting. Fifteen recommendations were developed; online voting was conducted to gauge agreement with each recommendation.

RESULTS

After considering recently available evidence across lung cancer populations and clinical experience, the experts recommended that all patients with a response to chemo-immunotherapy, good performance status (PS), and limited metastases be considered for consolidation TRT (e.g., 30 Gy in 10 fractions). When considered appropriate after multidisciplinary team discussion, TRT can be initiated during maintenance immunotherapy. All patients who respond to concurrent chemo-immunotherapy should undergo restaging with brain MRI to guide decision-making regarding PCI versus MRI surveillance alone. MRI surveillance should be conducted for two years after response to initial therapy. PCI (e.g., 25 Gy in 10 fractions or 20 Gy in 5 fractions) can be considered for patients without central nervous system involvement who have a response to chemo-immunotherapy and good PS. Concurrent treatment with PCI and immunotherapy or with TRT, PCI, and immunotherapy is appropriate after completion of initial therapy. All recommendations were agreed upon unanimously.

CONCLUSIONS

These consensus recommendations provide practical guidance regarding appropriate use of RT and immunotherapy in ES-SCLC while awaiting new clinical trial data.

Phase II trial of concurrent sunitinib, temozolomide, and radiotherapy with adjuvant temozolomide for newly diagnosed MGMT unmethylated glioblastoma

Background

The overall prognosis of glioblastoma (GBM) remains dismal, particularly for patients with unmethylated O6-methylguanine-DNA-methyltransferase (MGMT) promoter. In this phase II trial, we tested the combination of the antiangiogenic agent sunitinib with radiotherapy and temozolomide (TMZ) for newly diagnosed unmethylated MGMT GBM patients.

Methods

We enrolled 37 patients with unmethylated MGMT promoter GBM, age 18-70, and KPS ≥70. Patients received 12.5 mg of daily sunitinib for 7 days, followed by concurrent chemoradiation plus 12.5 mg sunitinib, then adjuvant TMZ. The primary endpoint was progression-free survival (PFS), and secondary endpoints were overall survival (OS), safety, and neutrophil-to-lymphocyte ratio (NLR) biomarker.

Results

At a median follow-up time of 15.3 months (range: 3.1-71.3 months), the median PFS was 7.15 months (95% CI: 5.4-10.5) and the 6-month PFS was 54.0%. Median OS was 15.0 months (95% CI: 13.8-19.4) and 2-year OS rate was 17.1%. Patients receiving >3 cycles of adjuvant TMZ, undergoing surgery at progression, and presenting a post-concurrent NLR ≤6 experienced a significant improved OS with hazard ratios of 0.197 (P = .001), 0.46 (P = .049), and 0.38 (P = .021), respectively, on multivariable analysis. Age >65 years predicted for worse OS with hazard ratio of 3.92 (P = .037). Grade ≥3 thrombocytopenia occurred in 22.9%, grade ≥3 neutropenia in 20%, and grade ≥3 thromboembolic events in 14.3% of patients. There were no grade 5 events.

Conclusion

Our findings suggest a potential benefit of combining sunitinib with chemoradiation in newly diagnosed GBM patients with unmethylated MGMT status and provide a strong rationale to test this combination in future studies.

EXTH-32. SEQUENTIAL SUNITINIB AND AURANOFIN TREATMENT INDUCEDCYTOTOXICITY THROUGH ROS-MEDIATED MECHANISM IN GLIOBLASTOMA

Glioblastoma (GBM) displays aberrant expression of several receptor tyrosine kinases (RTKs) leading to worse prognosis. Despite aggressive treatment including surgery, radiation and the alkylating agent temozolomide (TMZ), GBM tumors counteract deleterious effects of treatment-induced reactive oxygen species (ROS) leading to resistance to standard treatment. Likewise, expression of the DNA repair protein O6-methylguanine-DNA-methyltransferase (MGMT) plays a key role in resistance to TMZ.We previously reported a potential link between MGMT expression and decreased angiogenesis in GBM. The differential expression of MGMT affected response to sunitinib, a multitargeted RTK inhibitor with anti-angiogenic properties FDA-approved in different cancer types. Notably, TMZ-resistant GBM MGMT-positive cells were more vulnerable to sunitinib treatment compared to isogenic MGMT-negative cells. We further provided evidence for a positive relationship between MGMT and the antioxidant enzyme, thioredoxin reductase 1 (TrxR1) in GBM. The TrxR1-targeting drug Auranofin, FDA-approved for rheumatoid arthritis generated ROS and induced more cytotoxic effects in GBM cells displaying low expression of MGMT and TrXR1. We hypothesized that sunitinib-induced anti-proliferative effects might sensitize GBM cells to Auranofin. We showed that MGMT-negative GBM cells, which displayed lower levels of TrxR1, were more vulnerable to Auranofin than MGMT-positive cells. The ROS scavenger N-acetylcysteine (NAC) reverted the cytotoxicity of Auranofin suggesting ROS-mediated cytotoxic effects. Conversely, Sunitinib exhibited ROS-independent anti-proliferative effects in MGMT-positive cells. Remarkably, sequential treatment using sunitinib pre-treatment (2 hours) followed by Auranofin (24 hours) significantly decreased cell viability, clonogenicity, increased ROS, decreased TrXR1 and MGMT expression and sensitized MGMT-positive GBM cells resistant to Auranofin. NAC reverted these synergistic effects, suggesting ROS-mediated mechanism. Our study provides new insights into the modulation of the cellular redox homeostasis using sequential sunitinib and Auranofin. This will enable repurposing Auranofin and sunitinib, two drugs with a known safety profile for an effective therapeutic strategy for GBM patients.

Detection of Temozolomide-Induced Hypermutation and Response to PD-1 Checkpoint Inhibitor In Recurrent Glioblastoma

Background

Despite aggressive upfront treatment in glioblastoma (GBM), recurrence remains inevitable for most patients. Accumulating evidence has identified hypermutation induced by temozolomide (TMZ) as an emerging subtype of recurrent GBM. However, its biological and therapeutic significance has yet to be described.

Methods

We combined GBM patient and derive GBM stem cells (GSCs) from tumors following TMZ to explore response of hypermutant and non-hypermutant emergent phenotypes and explore the immune relevance of hypermutant and non-hypermutant states in vivo.

Results

Hypermutation emerges as one of two possible mutational subtypes following TMZ treatment in vivo and demonstrates distinct phenotypic features compared to non-hypermutant recurrent GBM. Hypermutant tumors elicited robust immune rejection in subcutaneous contexts which was accompanied by increased immune cell infiltration. In contrast, immune rejection of hypermutant tumors were stunted in orthotopic settings where we observe limited immune infiltration. Use of anti-PD-1 immunotherapy showed that immunosuppression in orthotopic contexts was independent from the PD-1/PD-L1 axis. Finally, we demonstrate that mutational burden can be estimated from DNA contained in extracellular vesicles (EVs).

Conclusion

Hypermutation post-TMZ are phenotypically distinct from non-hypermutant GBM and requires personalization for appropriate treatment. The brain microenvironment may be immunosuppressive and exploration of the mechanisms behind this may be key to improving immunotherapy response in this subtype of recurrent GBM.

SYST-08. A phase II trial of concurrent Sunitinib, Temozolomide and Radiation Therapy followed by adjuvant Temozolomide for newly diagnosed Glioblastoma patients with an unmethylated MGMT gene promoter (A01-M121-11A, McG1132)

INTRODUCTION

Despite advances in treatment modalities, the overall prognosis of GBM remains dismal, particularly for patients with unmethylated MGMT promoter. Thus, alternative treatment strategies are warranted. Our group has previously shown that addition of Sunitinib (SU11248) to standard therapy significantly improved the response of unmethylated MGMT cells through decreased angiogenicity and tumorigenicity. In this phase II trial, we tested for the first time the combination of Sunitinib with RT and Temozolomide in newly diagnosed MGMT unmethylated GBM patients.

METHODS

Patients with histologically confirmed WHO Grade IV GBM and MS-PCR confirmed unmethylated MGMT promoter, age 18-70, KPS ≥70, life expectancy ≥6 months were eligible. 41 patients treated between 2012 and 2017 were screened, 37 of which were eligible. Patients received 12.5 mg of daily Sunitinib for 7 days, followed by concurrent RT, Temozolomide and 12.5 mg Sunitinib for 6 weeks, then adjuvant Temozolomide x6 cycles. RT and Temozolomide doses were as per standard of care. Primary objective was PFS as assessed by RANO criteria, secondary objectives were OS and safety.

RESULTS

Median follow-up time was 15 months. Median PFS was 7 months (95%CI, 6.7-7.2) and 6-month PFS was 59.3%. Median OS was 13 months (95%CI, 12.62-13.37) and 2-year OS was 17.8%. Two patients had OS &gt;50 months, with one surviving 71 months. Having received &gt;3 cycles of adjuvant Temozolomide, surgery at progression or age ≤65 significantly predicted for better OS, with hazard ratios of 0.184 (p=0.001), 0.402 (p=0.026) and 10.017 (for age &gt;65, p=0.002) respectively. Grade ≥3 thrombocytopenia occurred in 18.9% of patients, grade ≥3 neutropenia in 10.8% and grade ≥3 thromboembolic events in 13.5%. There were no grade 5 evens.

CONCLUSION

Addition of Sunitinib to RT and Temozolomide was well tolerated and survival outcomes compared favorably to the current standard of care for GBM patients with unmethylated MGMT promoter status.

Metformin in Combination With Chemoradiotherapy in Locally Advanced Non-Small Cell Lung Cancer: The OCOG-ALMERA Randomized Clinical Trial

Importance

Unresected locally advanced non-small cell lung cancer (LA-NSCLC) shows poor survival outcomes even after aggressive concurrent chemoradiotherapy. Whether metformin, a diabetes agent that inhibits the mitochondria oxidative phosphorylation chain, could improve radiotherapy and chemotherapy response in LA-NSCLC remains to be studied.

Objective

To examine whether metformin, given concurrently with chemoradiotherapy and as consolidation treatment, could improve outcomes in patients with LA-NSCLC.

Design, Setting, and Participants

The Ontario Clinical Oncology Group Advanced Lung Cancer Treatment With Metformin and Chemoradiotherapy (OCOG-ALMERA) study was a multicenter phase 2 randomized clinical trial. Patients were stratified for stage IIIA vs IIIB LA-NSCLC and use of consolidation chemotherapy. The trial was designed to enroll 96 patients with unresected LA-NSCLC who did not have diabetes. The trial was conducted from September 24, 2014, to March 8, 2019.

Interventions

Patients were randomized to platinum-based chemotherapy, concurrent with chest radiotherapy (60-63 Gy), with or without consolidation chemotherapy or the same treatment plus metformin, 2000 mg/d, during chemoradiotherapy and afterward for up to 12 months.

Main Outcomes and Measures

The primary outcome was the proportion of patients who experienced a failure event (ie, locoregional disease progression, distant metastases, death, and discontinuation of trial treatment or planned evaluations for any reason within 12 months). Proportions were compared using a 2-sided Fisher exact test. Conventional progression-free and overall survival were estimated using the Kaplan-Meier method. Adverse events were graded with Common Terminology Criteria for Adverse Events, version 4.03. All randomized patients were included in an intention-to-treat analysis.

Results

The trial was stopped early due to slow accrual. Between 2014 and 2019, 54 patients were randomized (26 in experimental arm and 28 in control arm). Participants included 30 women (55.6%); mean (SD) age was 65.6 (7.6) years. Treatment failure was detected in 18 patients (69.2%) receiving metformin within 1 year vs 12 (42.9%) control patients (P = .05). The 1-year progression-free survival rate was 34.8% (95% CI, 16.6%-53.7%) in the metformin arm and 63.0% (95% CI, 42.1%-78.1%) in the control arm (hazard ratio, 2.42; 95% CI, 1.14-5.10) The overall survival rates were 47.4% (95% CI, 26.3%-65.9%) in the metformin arm and 85.2% (95% CI, 65.2%-94.2%) in the control arm (hazard ratio, 3.80; 95% CI, 1.49-9.73). More patients in the experimental arm vs control arm (53.8% vs 25.0%) reported at least 1 grade 3 or higher adverse event.

Conclusions and Relevance

In this randomized clinical trial, the addition of metformin to chemoradiotherapy was associated with worse treatment efficacy and increased toxic effects compared with combined modality therapy alone. Metformin is not recommended in patients with LA-NSCLC who are candidates for chemoradiotherapy.

Trial Registration

ClinicalTrials.gov Identifier: NCT02115464.

EXTH-09. NEO-ADJUVANT TEMOZOLOMIDE INCREASES THE EFFICACY OF SUBSEQUENT CONCURRENT CHEMORADIATION IN A TRANSGLUTAMINASE-2 DEPENDENT MANNER

Glioblastoma (GBM) is invariably fatal due to failure of current chemoradiation (Stupp) regimes. Biomarkers such as MGMT have proven to predict response to Temozolomide (TMZ). An equivalent biomarker for radiation (RT) has not yet been identified. Transglutaminase-2 (TGM2) has been implicated in driving radiation resistance; but the mechanism is poorly understood. We have investigated how exposure to neoadjuvant TMZ in glioma stem cells (GSCs) with different levels of TGM2 would affect the response to RT. MATERIALS/METHODS: Primary GSCs lines with different TGM2 levels (high: 1123, 83; low: 528, OPK49) were used to explore the role of TGM2 in RT response and modulation of expression by TMZ in vitro and in-vivo. RESULTS: We showed that TGM2 drives radioresistance in GSCs through restriction of p53 mediated repression of RAD51 expression. We demonstrate that exposure of GSCs to TMZ drives rapid downregulation of TGM2 in vitro and this phenomenon is recapitulated in vivo. Interestingly, we confirm that RT is able to drive reciprocal changes in TGM2 and promotes reactivation of TGM2 in TGM2-high tumours but not TGM2-low tumours. Given these observations, we hypothesized that exposure to neoadjuvant TMZ in TGM2-low tumours would increase the efficacy of subsequent RT in these tumours. Comparison of the effect of standard treatment consisting of 3 weeks of concurrent TMZ and RT (Stupp) to a novel regime (neo-Stupp) consisting of 1 week of neoadjuvant TMZ followed by two weeks of TMZ and hypofractionated RT revealed a superior survival benefit of this novel regime in TGM2-low tumours but not in TGM2-high tumours. Utilization of the TGM2 inhibitor GK921 in combination with neo-Stupp prevented rapid relapse previously observed in TGM2-high tumours. CONCLUSION: We provide evidence that TGM2 is a biomarker of RT response and can be used to tailor chemoradiation protocols to the unique biology of each individual GBM patient.

EXTH-35. SYNERGISTIC EFFECT OF TARGETING THIOREDOXIN REDUCTASE (TRX1) AND DEPLETION OF GLUTATHIONE SYSTEM (GSH) IN GLIOBLASTOMA STEM CELLS

Glioblastoma (GBM), the most common and advanced malignant primary brain tumor in adults remains incurable. GBM tumor recurrence occurs within a short time reflecting the failure to eradicate chemo-radioresistant GBM stem cells (GSCs). GSCs alter the redox system including Thioredoxin (Trx) and glutathione (GSH) systems to counteract increased reactive oxygen species (ROS). We previously showed the role of O6-methylguanine-DNA methyltransferase (MGMT) in response to PRIMAMET, a drug that targets the TP53 tumor suppressor gene and decrease Thioredoxin reductase1 (TRxR1) levels and further identified a positive relationship between MGMT and TrxR1 in established GBM cell lines isogenic for MGMT. Auranofin (Au), an orally available ROS-inducing FDA-approved drug is a potent irreversible inhibitor of TrxR1. The effect of Au on GSCs and the potential relationship between TrXR1, MGMT and p53 specifically in GSCs remain unknown. We hypothesized that increased ROS levels in GSCs might affect their drug resistant phenotype. we investigated the cytotoxic effects of Au on GSCs with known MGMT and P53 status and the mechanisms underlying these effects. Our results suggest that Au exerts strong cytotoxic effects in GSCs within a micromolar range. These effects were associated with increased ROS levels, decreased TrXR1, MGMT, phosphorylation of ERk1/2, activation of p53 and increased apoptosis, we also used a knockdown strategy to assess the role of p53 and showed that increased sensitivity to Au for p53-knockdown. We showed the role of ROS in response to Au using ROS inducer L-Buthionine Sulfoxamine (L-BSO), a GSH inhibitor, and ROS scavenger N-Acetylcysteine (NAc). L-BSO combined with Au drastically decreased the IC50 within a nanomolar range suggesting the crucial role of both Trx and GSH systems in GSCs redox balance. Increased ROS with concomitant GSH depletion using L-BSO might circumvent drug-induced oxidative stress and overcome drug resistance in MGMT-positive and negative GSCs

SABR-BRIDGE: Stereotactic ABlative Radiotherapy Before Resection to AvoId Delay for Early-Stage LunG Cancer or OligomEts During the COVID-19 Pandemic

Surgical resection is the standard-of-care approach for early-stage non-small cell lung cancer (NSCLC). Surgery is also considered an acceptable standard infit patients with oligometastatic lesions in the lungs. The COVID-19 pandemic has led to worldwide issues with access to operating room time, with patients and physicians facing uncertainty as to when surgical resection will be available, with likely delays of months. Further compounding this are concerns about increased risks of respiratory complications with lung cancer surgery during active phases of the pandemic. In this setting, many thoracic oncology teams are embracing a paradigm where stereotactic ablative radiotherapy (SABR) is used as a bridge, to provide radical-intent treatment based on a combination of immediate SABR followed by planned surgery in 3–6 months. This pragmatic approach to treatment has been named SABR-BRIDGE (Stereotactic ABlative Radiotherapy Before Resection to avoId Delay for early-stage lunG cancer or oligomEts). This term has also been applied to the pragmatic study of the outcomes of this approach. In this paper, we discuss the standards of care in treatment of early-stage (NSCLC) and pulmonary oligometastases, the impetus for the SABR-BRIDGE approach, and the controversies surrounding assessment of pathological response to neo-adjuvant radiation therapy.

Skin Toxicity in Early Breast Cancer Patients Treated with Field-In-Field Breast Intensity-Modulated Radiotherapy versus Helical Inverse Breast Intensity-Modulated Radiotherapy: Results of a Phase III Randomised Controlled Trial

AIMS

Skin toxicity is a common adverse effect of breast radiotherapy. We investigated whether inverse-planned intensity-modulated radiotherapy (IMRT) would reduce the incidence of skin toxicity compared with forward field-in-field breast IMRT (FiF-IMRT) in early stage breast cancer.

MATERIALS AND METHODS

This phase III randomised controlled trial compared whole-breast irradiation with either FiF-IMRT or helical tomotherapy IMRT (HT-IMRT), with skin toxicity as the primary end point. Patients received 50 Gy in 25 fractions and were assessed to compare skin toxicity between treatment arms.

RESULTS

In total, 177 patients were available for assessment and the median follow-up was 73.1 months. Inverse IMRT achieved more homogeneous coverage than FiF-IMRT; erythema and moist desquamation were higher with FiF-IMRT compared with HT-IMRT (61% versus 34%; P < 0.001; 33% versus 11%; P < 0.001, respectively). Multivariate analysis showed large breast volume, FiF-IMRT and chemotherapy were independent factors associated with worse acute toxicity. There was no difference between treatment arms in the incidence of late toxicities. The 5-year recurrence-free survival was 96.3% for both FiF-IMRT and HT-IMRT and the 5-year overall survival was 96.3% for FiF-IMRT and 97.4% for HT-IMRT.

CONCLUSIONS

Our study showed significant reduction in acute skin toxicity using HT-IMRT compared with FiF-IMRT, without significant reduction in late skin toxicities. On the basis of these findings, inverse-planned IMRT could be used in routine practice for whole-breast irradiation with careful plan optimisation to achieve the required dose constraints for organs at risk.

EXTH-50. THIOREDOXIN REDUCTASE1 AND MGMT SYNTHETIC LETHALITY ENHANCES CYTOTOXICITY OF PRIMA-1MET(APR-246) AND AURANOFIN IN GLIOBLASTOMA

Glioblastoma multiforme (GBM), the most common and advanced primary brain malignancy in adults remains an incurable disease, despite aggressive treatment with surgery, radiation therapy and chemoradiation using the alkylating agent, Temozolomide (TMZ). PRIMA-1MET (APR-246), a small molecule designed to restore mutant (mut)p53 function has been shown to affect cellular redox status through targeting thioredoxin reductase 1 (TrxR1) in wild-type (wt)p53 cancer cells. We have recently shown that PRIMA-1MET exerts cytotoxic effects status preferentially in GBM cell lines expressing low levels of the DNA repair protein O6-methylguanine-DNA-methyltransferase (MGMT), known for its role in resistance to TMZ. We hypothesized that PRIMA-1MET mediates its growth inhibitory effects by modulating the redox balance and investigated the potential relationship between MGMT, redox balance and TrxR1. We show that PRIMA-1MET decreased TrxR1 expression levels preferentially in MGMT-low expressing isogenic GBM cell lines. Using pharmacological agents that modulate reactive oxygen species (ROS) levels i.e., ROS scavenger, N-acetylcysteine and ROS inducer, L-Buthionine-Sulfoximine, we show that PRIMA-1MET exerts its growth-inhibitory effects through increased ROS. Strikingly, we identified a novel positive relationship between MGMT and TrxR1, wherein high MGMT expression is associated with high expression of TrxR1 and low levels of ROS. Treatment with the MGMT inhibitor, O6-Benzylguanine, or the TrxR1-targeting FDA-approved drug Auranofin validated our findings. Interestingly, the latter exerted significantly more pronounced cytotoxic effects compared to PRIMA-1MET in GBM cell lines. Additional studies are warranted to assess PRIMA-1MET in combination with TrxR1-targeting therapies and propose repurposing of Auranofin as a novel strategy to improve the dismal outcome of patients with GBM.

DRES-10. TEMOZOLOMIDE-ASSOCIATED HYPERMUTATION DETECTED WITH A GENE PANEL SIGNATURE IMPROVES IMMUNE RESPONSE IN GLIOBLASTOMA

Glioblastoma (GBM) is the most common and deadly type of malignant brain cancer in adults. While current standard of care which combines resection, radiation therapy (RT) and Temozolomide (TMZ) effectively eliminates primary disease, recurrence is inevitable, occurs rapidly following treatment and is ultimately lethal due to limited therapeutic opportunities of recurrent GBM. Hypermutation has been reported to occur in a subset of both low and high-grade gliomas and emerges after exposure to TMZ. Mutational inactivation and loss of mismatch repair (MMR) gene expression lead to the accumulation of single nucleotide polymorphisms throughout the genome. To date, the gain of hypermutation and subsequent therapeutic responses are still largely unknown. We hypothesized that hypermutant (HM) and non-hypermutant (NH) tumors represent two recurrent GBM subtypes, which has distinct therapeutic vulnerabilities. In addition, given the lack of concordance between microsatellite instability (MSI) and occurrence of hypermutation in GBM, we sought to derive a limited gene panel which can be used as surrogate biomarker for hypermutation following TMZ to replace whole exome sequencing (WES). Using public datasets, we demonstrated that recurrent GBM can be clustered into two subtypes: HM and NH. We used matched primary and recurrent GBM datasets to derive a gene panel signature, which is uniquely mutated at recurrence in HM GBM and confirmed the specificity of this panel in an independent dataset. Furthermore, we utilized patient derived xenograft (PDX) models to generate pre-clinical models and demonstrated that HM recurrent GBM are more immune responsive while NH recurrent GBM maintained sensitivity to a range of alternate chemotherapies such as cisplatin and RT. Finally, we demonstrated that this signature is represented in exosomes and can be enriched by use of tumor specific antibody capture methods to improve the sensitivity of hypermutation detection in liquid biopsy.

Mechanisms and Antitumor Activity of a Binary EGFR/DNA-Targeting Strategy Overcomes Resistance of Glioblastoma Stem Cells to Temozolomide

PURPOSE

Glioblastoma (GBM) is a fatal primary malignant brain tumor. GBM stem cells (GSC) contribute to resistance to the DNA-damaging chemotherapy, temozolomide. The epidermal growth factor receptor (EGFR) displays genomic alterations enabling DNA repair mechanisms in half of GBMs. We aimed to investigate EGFR/DNA combi-targeting in GBM.

EXPERIMENTAL DESIGN

ZR2002 is a "combi-molecule" designed to inflict DNA damage through its chlorethyl moiety and induce irreversible EGFR tyrosine kinase inhibition. We assessed its in vitro efficacy in temozolomide-resistant patient-derived GSCs, mesenchymal temozolomide-sensitive and resistant in vivo-derived GSC sublines, and U87/EGFR isogenic cell lines stably expressing EGFR/wild-type or variant III (EGFRvIII). We evaluated its antitumor activity in mice harboring orthotopic EGFRvIII or mesenchymal TMZ-resistant GSC tumors.

RESULTS

ZR2002 induced submicromolar antiproliferative effects and inhibited neurosphere formation of all GSCs with marginal effects on normal human astrocytes. ZR2002 inhibited EGF-induced autophosphorylation of EGFR, downstream Erk1/2 phosphorylation, increased DNA strand breaks, and induced activation of wild-type p53; the latter was required for its cytotoxicity through p53-dependent mechanism. ZR2002 induced similar effects on U87/EGFR cell lines and its oral administration significantly increased survival in an orthotopic EGFRvIII mouse model. ZR2002 improved survival of mice harboring intracranial mesenchymal temozolomide-resistant GSC line, decreased EGFR, Erk1/2, and AKT phosphorylation and was detected in tumor brain tissue by MALDI imaging mass spectrometry.

CONCLUSIONS

These findings provide the molecular basis of binary EGFR/DNA targeting and uncover the oral bioavailability, blood-brain barrier permeability, and antitumor activity of ZR2002 supporting potential evaluation of this first-in-class drug in recurrent GBM.

PTHrP, A Biomarker for CNS Metastasis in Triple-Negative Breast Cancer and Selection for Adjuvant Chemotherapy in Node-Negative Disease

Background

Triple-negative breast cancer (TNBC) is characterized by poor prognosis and lack of targeted therapies and biomarkers to guide decisions on adjuvant chemotherapy. Parathyroid hormone-related protein (PTHrP) is frequently overexpressed in breast cancer and involved in proliferation and metastasis, two hallmarks of poor prognosis for node-negative breast cancer. We investigated the prognostic value of PTHrP with respect to organ-specific metastasis and nodal status in TNBC.

Methods

We assessed PTHrP expression using immunohistochemistry in a clinically annotated tissue microarray for a population-based study of 314 patients newly diagnosed with TNBC, then analyzed its correlation to progression and survival using Kaplan-Meier and Cox regression analyses. The Cancer Genome Atlas (TCGA) validation analysis was performed through Bioconductor. All statistical tests were two-sided.

Results

PTHrP overexpression (160 of 290 scorable cases, 55.2%) was statistically significantly associated in univariate analysis with decreased overall survival (OS) in our cohort (P = .0055) and The Cancer Genome Atlas (P = .0018) and decreased central nervous system (CNS)-progression-free survival (P = .0029). In multivariate analysis, PTHrP was a statistically significant independent prognostic factor for CNS-progression-free survival in TNBC (hazard ratio [HR] = 5.014, 95% confidence interval [CI] = 1.421 to 17.692, P = .0122) and for OS selectively in node-negative TNBC (HR = 2.423, 95% CI = 1.129 to 5.197, P = .0231). Strikingly, PTHrP emerged as the only statistically significant prognostic factor (HR = 2.576, 95% CI = 1.019 to 6.513, P = .0456) for OS of low-clinical risk node-negative patients who did not receive adjuvant chemotherapy.

Conclusions

PTHrP is a novel independent prognostic factor for CNS metastasis and adjuvant chemotherapy selection of low-clinical risk node-negative TNBC. Its predictive value needs to be prospectively assessed in clinical trials.

Integration of Radiomic and Multi-omic Analyses Predicts Survival of Newly Diagnosed IDH1 Wild-Type Glioblastoma

Predictors of patient outcome derived from gene methylation, mutation, or expression are severely limited in IDH1 wild-type glioblastoma (GBM). Radiomics offers an alternative insight into tumor characteristics which can provide complementary information for predictive models. The study aimed to evaluate whether predictive models which integrate radiomic, gene, and clinical (multi-omic) features together offer an increased capacity to predict patient outcome. A dataset comprising 200 IDH1 wild-type GBM patients, derived from The Cancer Imaging Archive (TCIA) (n = 71) and the McGill University Health Centre (n = 129), was used in this study. Radiomic features (n = 45) were extracted from tumor volumes then correlated to biological variables and clinical outcomes. By performing 10-fold cross-validation (n = 200) and utilizing independent training/testing datasets (n = 100/100), an integrative model was derived from multi-omic features and evaluated for predictive strength. Integrative models using a limited panel of radiomic (sum of squares variance, large zone/low gray emphasis, autocorrelation), clinical (therapy type, age), genetic (CIC, PIK3R1, FUBP1) and protein expression (p53, vimentin) yielded a maximal AUC of 78.24% (p = 2.9 × 10⁻⁵). We posit that multi-omic models using the limited set of ‘omic’ features outlined above can improve capacity to predict the outcome for IDH1 wild-type GBM patients.

Radiomics in Glioblastoma: Current Status and Challenges Facing Clinical Implementation

Radiomics analysis has had remarkable progress along with advances in medical imaging, most notability in central nervous system malignancies. Radiomics refers to the extraction of a large number of quantitative features that describe the intensity, texture and geometrical characteristics attributed to the tumor radiographic data. These features have been used to build predictive models for diagnosis, prognosis, and therapeutic response. Such models are being combined with clinical, biological, genetics and proteomic features to enhance reproducibility. Broadly, the four steps necessary for radiomic analysis are: (1) image acquisition, (2) segmentation or labeling, (3) feature extraction, and (4) statistical analysis. Major methodological challenges remain prior to clinical implementation. Essential steps include: adoption of an optimized standard imaging process, establishing a common criterion for performing segmentation, fully automated extraction of radiomic features without redundancy, and robust statistical modeling validated in the prospective setting. This review walks through these steps in detail, as it pertains to high grade gliomas. The impact on precision medicine will be discussed, as well as the challenges facing clinical implementation of radiomic in the current management of glioblastoma.

An integrated stress response via PKR suppresses HER2+ cancers and improves trastuzumab therapy

Trastuzumab is integral to HER2+ cancer treatment, but its therapeutic index is narrowed by the development of resistance. Phosphorylation of the translation initiation factor eIF2α (eIF2α-P) is the nodal point of the integrated stress response, which promotes survival or death in a context-dependent manner. Here, we show an anti-tumor function of the protein kinase PKR and its substrate eIF2α in a mouse HER2+ breast cancer model. The anti-tumor function depends on the transcription factor ATF4, which upregulates the CDK inhibitor P21^CIP1 and activates JNK1/2. The PKR/eIF2α-P arm is induced by Trastuzumab in sensitive but not resistant HER2+ breast tumors. Also, eIF2α-P stimulation by the phosphatase inhibitor SAL003 substantially increases Trastuzumab potency in resistant HER2+ breast and gastric tumors. Increased eIF2α-P prognosticates a better response of HER2+ metastatic breast cancer patients to Trastuzumab therapy. Hence, the PKR/eIF2α-P arm antagonizes HER2 tumorigenesis whereas its pharmacological stimulation improves the efficacy of Trastuzumab therapy.

The HER2 monoclonal antibody, Trastuzumab, is the current standard treatment for HER2+ cancers but resistance to therapy occurs. Here, the authors show that activation of the PKR/eIF2α-P pathway exhibits anti-tumor effects in HER2+ cancer and is required for the response to Trastuzumab.

Divergent evolution of temozolomide resistance in glioblastoma stem cells is reflected in extracellular vesicles and coupled with radiosensitization

Background

Glioblastoma (GBM) is almost invariably fatal due to failure of standard therapy. The relapse of GBM following surgery, radiation, and systemic temozolomide (TMZ) is attributed to the ability of glioma stem cells (GSCs) to survive, evolve, and repopulate the tumor mass, events on which therapy exerts a poorly understood influence.

Methods

Here we explore the molecular and cellular evolution of TMZ resistance as it emerges in vivo (xenograft models) in a series of human GSCs with either proneural (PN) or mesenchymal (MES) molecular characteristics.

Results

We observed that the initial response of GSC-initiated intracranial xenografts to TMZ is eventually replaced by refractory growth pattern. Individual tumors derived from the same isogenic GSC line expressed divergent and complex profiles of TMZ resistance markers, with a minor representation of O6-methylguanine DNA methyltransferase (MGMT) upregulation. In several independent TMZ-resistant tumors originating from MES GSCs we observed a consistent diminution of mesenchymal features, which persisted in cell culture and correlated with increased expression of Nestin, decline in transglutaminase 2 and sensitivity to radiation. The corresponding mRNA expression profiles reflective of TMZ resistance and stem cell phenotype were recapitulated in the transcriptome of exosome-like extracellular vesicles (EVs) released by GSCs into the culture medium.

Conclusions

Intrinsic changes in the tumor-initiating cell compartment may include loss of subtype characteristics and reciprocal alterations in sensitivity to chemo- and radiation therapy. These observations suggest that exploiting therapy-induced changes in the GSC phenotype and alternating cycles of therapy may be explored to improve GBM outcomes.

CUX1 stimulates APE1 enzymatic activity and increases the resistance of glioblastoma cells to the mono-alkylating agent temozolomide

Background

Cut Like homeobox 1 (CUX1), which encodes an auxiliary factor in base excision repair, resides on 7q22.1, the most frequently and highly amplified chromosomal region in glioblastomas. The resistance of glioblastoma cells to the mono-alkylating agent temozolomide is determined to some extent by the activity of apurinic/apyrimidinic endonuclease 1 (APE1).

Methods

To monitor the effect of CUX1 and its CUT domains on APE1 activity, DNA repair assays were performed with purified proteins and cell extracts. CUX1 protein expression was analyzed by immunohistochemistry using a tumor microarray of 150 glioblastoma samples. The effect of CUX1 knockdown and overexpression on the resistance of glioblastoma cell lines to temozolomide was investigated.

Results

We show that CUT domains stimulate APE1 activity. In agreement with these findings, CUX1 knockdown causes an increase in the number of abasic sites in genomic DNA and a decrease in APE1 activity as measured in cell extracts. Conversely, ectopic CUX1 expression increases APE1 activity and lowers the number of abasic sites. Having established that CUX1 is expressed at high levels in most glioblastomas, we next show that the resistance of glioblastoma cells to temozolomide and to a combined treatment of temozolomide and ionizing radiation is reduced following CUX1 knockdown, but increased by overexpression of CUX1 or a short protein containing only 2 CUT domains, which is active in DNA repair but devoid of transcriptional activity.

Conclusion

These findings indicate that CUX1 expression level impacts on the response of glioblastoma cells to treatment and identifies the CUT domains as potential therapeutic targets.

Cleavage of the extracellular domain of junctional adhesion molecule-A is associated with resistance to anti-HER2 therapies in breast cancer settings

BACKGROUND

Junctional adhesion molecule-A (JAM-A) is an adhesion molecule whose overexpression on breast tumor tissue has been associated with aggressive cancer phenotypes, including human epidermal growth factor receptor-2 (HER2)-positive disease. Since JAM-A has been described to regulate HER2 expression in breast cancer cells, we hypothesized that JAM-dependent stabilization of HER2 could participate in resistance to HER2-targeted therapies.

METHODS

Using breast cancer cell line models resistant to anti-HER2 drugs, we investigated JAM-A expression and the effect of JAM-A silencing on biochemical/functional parameters. We also tested whether altered JAM-A expression/processing underpinned differences between drug-sensitive and -resistant cells and acted as a biomarker of patients who developed resistance to HER2-targeted therapies.

RESULTS

Silencing JAM-A enhanced the anti-proliferative effects of anti-HER2 treatments in trastuzumab- and lapatinib-resistant breast cancer cells and further reduced HER2 protein expression and Akt phosphorylation in drug-treated cells. Increased epidermal growth factor receptor expression observed in drug-resistant models was normalized upon JAM-A silencing. JAM-A was highly expressed in all of a small cohort of HER2-positive patients whose disease recurred following anti-HER2 therapy. High JAM-A expression also correlated with metastatic disease at the time of diagnosis in another patient cohort resistant to trastuzumab therapy. Importantly, cleavage of JAM-A was increased in drug-resistant cell lines in conjunction with increased expression of ADAM-10 and -17 metalloproteases. Pharmacological inhibition or genetic silencing studies suggested a particular role for ADAM-10 in reducing JAM-A cleavage and partially re-sensitizing drug-resistant cells to the anti-proliferative effects of HER2-targeted drugs. Functionally, recombinant cleaved JAM-A enhanced breast cancer cell invasion in vitro and both invasion and proliferation in a semi-in vivo model. Finally, cleaved JAM-A was detectable in the serum of a small cohort of HER2-positive patients and correlated significantly with resistance to HER2-targeted therapy.

CONCLUSIONS

Collectively, our data suggest a novel model whereby increased expression and cleavage of JAM-A drive tumorigenic behavior and act as a biomarker and potential therapeutic target for resistance to HER2-targeted therapies.

Prognostic factors for progression in atypical meningioma

OBJECTIVE

The optimal adjuvant management for atypical meningiomas remains controversial. The aim of this study was to review long-term outcomes to identify potential prognostic factors for disease progression.

METHODS

From August 1992 to August 2013, 70 patients with atypical meningioma were treated at the authors’ institution. Pathology revision was performed based on WHO 2007 criteria. Patients with multiple tumors, neurofibromatosis Type 2, or inadequate imaging follow-up were not eligible. The authors performed pre- and postoperative serial measurements of tumor volume from MRI. Age, sex, tumor location, bone involvement, brain invasion, mitotic figures, preoperative disease volume, extent of resection, tumor growth rates, use of adjuvant postoperative radiation therapy (PORT), and residual tumor volume at the time of radiation therapy (RT) were assessed by univariate and multivariate analysis to determine their potential impact on disease progression.

RESULTS

Forty patients (57%) underwent gross-total resection (GTR) and 30 (43%) underwent subtotal resection (STR). PORT was delivered to 12 patients (30%) with a GTR and in only 4 (13%) with an STR. The 5-year progression-free survival (PFS) rate for patients in the GTR group with or without PORT was 100% and 54.1%, respectively (p = 0.0058). PFS for patients in the STR group with or without PORT was 75% and 0%, respectively (p = 0.0026). On multivariate analysis, STR and PORT were the only independent significant prognostic factors for disease progression with hazard ratios of 5.4873 (95% CI 2.19–13.72, p = 0.0003) and 0.0464 (95% CI 0.0059–0.364, p = 0.0035), respectively. Based on Youden’s index statistic, a cutoff residual tumor volume of more than 8.76 cm3 at the time of RT was associated with worse PFS (13.6% vs 56%, p = 0.0079). Before receiving RT, the median relative and absolute growth rates and tumor doubling time for patients were 124.2%/year, 4.8 cm3/year, and 1.67 years, respectively. These indices changed after RT to 0.245%/year, −0.09 cm3/year, and −0.005 year, respectively (p < 0.05).

CONCLUSIONS

In atypical meningioma, the use of PORT is associated with improved PFS even in patients who undergo GTR. Patients with residual tumor volume larger than 8.76 cm3 have an increased risk of disease progression and should be considered for early RT.

Abstract 4699: Identification of novel potential biomarkers of response to sunitinib in glioblastoma

Introduction: Glioblastoma multiforme (GBM) is the most advanced and aggressive form of primary malignant brain tumors in adults. O6-Methylguanine methyltransferase (MGMT) is a DNA repair protein well known for its role in resistance to temozolomide used in standard treatment of patients newly diagnosed with GBM. Sunitinib is an oral multitargeting receptor tyrosine kinase (RTK) inhibitor with antiangiogenic and antiproliferative activities targeting several RTKs. Our group has previously shown the role of MGMT as a negative regulator of angiogenesis and invasion and the differential antiproliferative effect of sunitinib based on expression of MGMT in GBM. Recent gene expression profiling (GEP) studies showed that besides its effects on RTKs, sunitinib affects the expression level of other genes at the transcriptional level in different cancer types. We hypothesized that: (i) the mechanism of action of sunitinib may not be limited to direct inhibition of its known targets (RTKs) in GBM and (ii) expression of MGMT may affect response of GBM tumor cells to sunitinib. We performed GEP analysis to identify genes that could be potentially modulated in response to sunitinib in GBM cell lines isogenic for MGMT. Empty vector (EV)-transfected T98/EV cells with constitutive expression of MGMT and its knockdown counterpart T98/MGMT-shRNA were treated with sunitinib or vehicle control. Treatment of T98/EV and T98/MGMT-shRNA cell lines with sunitinib significantly changed the expression of over 2,000 gene transcripts (analysis performed at Genome Quebec Innovation center, McGill University). Lists of significant genes were fitted into previously known biochemical pathways, available among the canonical pathways from various databases provided by ConsensusPathDB (CPDB). Strikingly, immune system was among the top significantly enriched pathways (p-value&lt;10-3), with some immune pathways not previously reported for response to sunitinib.

Conclusion: Our study opens new avenues to further understand the mechanisms of action of sunitinib, investigate its immunomodulatory effects, and identify biomarkers for selection of patients who might benefit from the combination of antiangiogenic and immunebased strategies in GBM.

Funding Acknowledgment: Cancer Research Society Operating Grant Competition #22716, and Higher Education Quality Enhancement Project (HEQEP)- Window -4 (Grant Id. CP-4023), University Grant Commission (UGC), Bangladesh.

Citation Format: Abu Shadat Mohammod Noman, Bassam Abdulkarim, Siham Sabri. Identification of novel potential biomarkers of response to sunitinib in glioblastoma [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 4699.

Abstract 2632: Identification of PTHrP as a biomarker of short survival & brain metastasis in a tissue microarray retrospective analysis of triple-negative breast cancer

Triple-negative breast cancer (TNBC) represents 10-20% of all BC cases, and is characterized by aggressive clinical course, frequent relapse, poor patient outcome, and lack of targeted therapy due to the lack of expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER-2). Identifying TNBC molecular drivers and biomarkers would thus be highly beneficial to develop efficient targeted therapies. The parathyroid hormone-related protein (PTHrP) is known for its role in mammary gland and bone development, in addition to breast cancer progression. The aim of this study is to investigate the role of PTHrP as a potential prognostic biomarker in human TNBC.

We assessed PTHrP expression using immunohistochemical analysis of a tissue microarray (TMA) constructed for 523 patients newly diagnosed with TNBC between January 1998 and December 2008 in a single-center series with centralized ER, PR and HER-2 testing and standardized treatment and follow-up. We evaluated the correlation between PTHrP expression and TNBC patients' clinico-pathological features as well as progression and survival outcomes for a subset of 314 patients with available clinical data.

We show that PTHrP is overexpressed in 55.2% of TNBC tumors and high PTHrP expression is significantly associated with higher propensity for brain progression compared to other sites of distal progression (p=0.0458). Univariate analysis revealed that high PTHrP expression is significantly associated with decreased overall survival (OS) (p=0.0055), but not with progression-free survival (PFS) (p=0.1270). To further investigate the prognostic value of PTHrP with respect to different TNBC molecular subtypes, we analysed expression of markers known to stratify different TNBC subtypes. Multivariate analysis of PTHrP as an independent prognostic factor of survival with respect to different TNBC molecular subtypes is currently underway.

In conclusion, we provide for the first time evidence that increased PTHrP expression is significantly associated with shorter OS and higher propensity of brain progression in patients diagnosed with TNBC. Consequently, stratification of this disease based on PTHrP expression might identify patients with relatively higher risk of aggressive disease with brain progression. Additional studies investigating the role of PTHrP in organ-specific metastasis and using PTHrP-targeting strategies are warranted to improve the therapeutic outcome for patients diagnosed with TNBC.

Funding: Alberta Cancer Research Institute (ACRI) grant and Department of Defense (DoD, USA) Award No. W81XWH-15-1-0723

Citation Format: Gloria Assaker, Anne Camirand, Bassam Abdulkarim, Atilla Omeroglu, Jean Deschenes, Leon Van Kempen, Richard Kremer, Siham Sabri. Identification of PTHrP as a biomarker of short survival & brain metastasis in a tissue microarray retrospective analysis of triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2632.

Abstract 4174: Differential response of non-small cell lung cancer harboring different epidermal growth factor receptor mutations to ablative radiation therapy

Background: ablative radiation therapy (ABR) serves as the treatment of choice for early stage non-small cell lung cancer (NSCLC) patients who are not surgical candidates. NSCLC patients with mutations in the tyrosine kinase domain (TKD) of the epidermal growth factor receptor (EGFR) had a significant response to tyrosine kinase inhibitors (TYIs). The most common mutations of EGFR in NSCLC are present in the TKD domain and include: deletion (DEL) in the exon 19 and a missense mutation (L858R) in the exon 21. The role of extracellular vesicles (EVs) has been under extensive investigation due to its contribution in preparing the distant site through a process named pre-metastatic niche formation. Release of irradiation-induced EVs in EGFR mutated NSCLC and their responses to ABR have not been well investigated. We aim to assess EVs release and tumor growth of NSCLC harboring different EGFR mutations post- ABR. Materials and methods: We used A549 that were transduced with different EGFR status: EGFR-WT (WT), EGFR-DEL (DEL) or EGFR-L858R (L858R) and irradiated them at 0, 12 or 34Gy. The condition media were then collected at 24hrs post-irradiation and used to measure release of extracellular vesicles (EVs) using nanosight. We transduced the cells with lentivirus expressing luciferase. Cells were irradiated at 0Gy (Ctrl group) or 34Gy (IR group) and injected subcutaneously in yellow fluorescent protein -severe combined immunodeficiency (YFP-SCID) mice. Tumor volume and animal weight were measured regularly and bioluminescence imaging (BLI) was used to evaluate tumor growth and metastasis. Results: L858R-expressing cells had an increase in EVs release post-ABR (12 and 34Gy), compared to WT-expressing cells which did not have difference in EVs release following ABR. DEL-expressing cells had an increase in EVs release only at 34Gy. Furthermore, in vivo data revels that ABR caused a decrease in tumor growth of IR-WT and IR-DEL groups when compared to Ctrl-WT and Ctrl-DEL, respectively. Interestingly, both Ctrl-L858R and IR-L858R groups presented similar tumor growth. Further investigations are undergoing assessing the EVs release and their function in the occurrence of distant metastasis post-ABR. Conclusion: in our study, we report a differential response of non-small cell lung cancer to ABR that could be caused by the differences in EGFR status. As a result, the standard use of ABR should not only be based on the patients' comorbidity status, but should also be based on his/her genetic background in order to determine the optimal treatment.

Citation Format: Areej Al Rabea, Brian Meehan, Paul Daniel, Siham Sabri, Chaitanya Nirodi, Janusz Rak, Bassam Abdulkarim. Differential response of non-small cell lung cancer harboring different epidermal growth factor receptor mutations to ablative radiation therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4174.

Novel Radiomic Features Based on Joint Intensity Matrices for Predicting Glioblastoma Patient Survival Time

This paper presents a novel set of image texture features generalizing standard grey-level co-occurrence matrices (GLCM) to multimodal image data through joint intensity matrices (JIMs). These are used to predict the survival of glioblastoma multiforme (GBM) patients from multimodal MRI data. The scans of 73 GBM patients from the Cancer Imaging Archive are used in our study. Necrosis, active tumor, and edema/invasion subregions of GBM phenotypes are segmented using the coregistration of contrast-enhanced T1-weighted (CE-T1) images and its corresponding fluid-attenuated inversion recovery (FLAIR) images. Texture features are then computed from the JIM of these GBM subregions and a random forest model is employed to classify patients into short or long survival groups. Our survival analysis identified JIM features in necrotic (e.g., entropy and inverse-variance) and edema (e.g., entropy and contrast) subregions that are moderately correlated with survival time (i.e., Spearman rank correlation of 0.35). Moreover, nine features were found to be associated with GBM survival with a Hazard-ratio range of 0.38-2.1 and a significance level of p < 0.05 following Holm-Bonferroni correction. These features also led to the highest accuracy in a univariate analysis for predicting the survival group of patients, with AUC values in the range of 68-70%. Considering multiple features for this task, JIM features led to significantly higher AUC values than those based on standard GLCMs and gene expression. Furthermore, an AUC of 77.56% with p = 0.003 was achieved when combining JIM, GLCM, and gene expression features into a single radiogenomic signature. In summary, our study demonstrated the usefulness of modeling the joint intensity characteristics of CE-T1 and FLAIR images for predicting the prognosis of patients with GBM.

Predicting survival time of lung cancer patients using radiomic analysis

OBJECTIVES

This study investigates the prediction of Non-small cell lung cancer (NSCLC) patient survival outcomes based on radiomic texture and shape features automatically extracted from tumor image data.

MATERIALS AND METHODS

Retrospective analysis involves CT scans of 315 NSCLC patients from The Cancer Imaging Archive (TCIA). A total of 24 image features are computed from labeled tumor volumes of patients within groups defined using NSCLC subtype and TNM staging information. Spearman's rank correlation, Kaplan-Meier estimation and log-rank tests were used to identify features related to long/short NSCLC patient survival groups. Automatic random forest classification was used to predict patient survival group from multivariate feature data. Significance is assessed at P < 0.05 following Holm-Bonferroni correction for multiple comparisons.

RESULTS

Significant correlations between radiomic features and survival were observed for four clinical groups: (group, [absolute correlation range]): (large cell carcinoma (LCC) [0.35, 0.43]), (tumor size T2, [0.31, 0.39]), (non lymph node metastasis N0, [0.3, 0.33]), (TNM stage I, [0.39, 0.48]). Significant log-rank relationships between features and survival time were observed for three clinical groups: (group, hazard ratio): (LCC, 3.0), (LCC, 3.9), (T2, 2.5) and (stage I, 2.9). Automatic survival prediction performance (i.e. below/above median) is superior for combined radiomic features with age-TNM in comparison to standard TNM clinical staging information (clinical group, mean area-under-the-ROC-curve (AUC)): (LCC, 75.73%), (N0, 70.33%), (T2, 70.28%) and (TNM-I, 76.17%).

CONCLUSION

Quantitative lung CT imaging features can be used as indicators of survival, in particular for patients with large-cell-carcinoma (LCC), primary-tumor-sizes (T2) and no lymph-node-metastasis (N0).

Differential response to ablative ionizing radiation in genetically distinct non-small cell lung cancer cells

Stereotactic ablative radiotherapy (SABR) has emerged as a highly promising treatment for medically inoperable early-stage non-small cell lung cancer patients. Treatment outcomes after SABR have been excellent compared to conventional fractionated radiotherapy (CFRT). However, the biological determinants of the response to ablative doses of radiation remain poorly characterized. Furthermore, there's little data on the cellular and molecular response of genetically distinct NSCLC subtypes to radiation. We assessed the response of 3 genetically distinct lung adenocarcinoma cell lines to ablative and fractionated ionizing radiation (AIR and FIR). We studied clonogenic survival, cell proliferation, migration, invasion, apoptosis and senescence. We also investigated the effect of AIR and FIR on the expression of pro-invasive proteins, epithelial-to-mesenchymal transition (EMT), extracellular signal-regulated kinases (ERK1/2) and the transmembrane receptor cMET. Our findings reveal that AIR significantly reduced cell proliferation and clonogenic survival compared to FIR in A549 cells only. This differential response was not observed in HCC827 or H1975 cells. AIR significantly enhanced the invasiveness of A549 cells, but not HCC827 or H1975 cells compared to FIR. Molecular analysis of pathways involved in cell proliferation and invasion revealed that AIR significantly reduced phosphorylation of ERK1/2 and upregulated cMET expression in A549 cells. Our results show a differential proliferative and invasive response to AIR that is dependent on genetic subtype and independent of intrinsic radioresistance. Further examination of these findings in a larger panel of NSCLC cell lines and in pre-clinical models is warranted for identification of biomarkers of tumor response to AIR.

A Phase 2 Trial of Neoadjuvant Temozolomide Followed by Hypofractionated Accelerated Radiation Therapy With Concurrent and Adjuvant Temozolomide for Patients With Glioblastoma

PURPOSE

We performed a phase 2 trial of neoadjuvant temozolomide (TMZ), followed by hypofractionated accelerated radiation therapy (HART) with concurrent TMZ, and adjuvant TMZ in patients with newly diagnosed glioblastoma to determine whether neoadjuvant TMZ would safely improve outcomes in this group of patients prior to subsequent cytotoxic therapy.

METHODS AND MATERIALS

Adult patients with newly diagnosed glioblastoma and a Karnofsky Performance Status >60 were eligible. Neoadjuvant TMZ administration started 2 to 3 weeks from surgery at a daily dose of 75 mg/m² for 2 weeks prior to delivery of HART (60 Gy in 20 daily fractions) with concurrent and adjuvant TMZ. The primary endpoints were feasibility and toxicity. The secondary endpoints included overall survival (OS) and progression-free survival.

RESULTS

Fifty patients were accrued. The median follow-up period was 44.0 months for patients at risk and 22.3 months for all 50 patients. Except for 1 patient in whom infection developed and another patient with progression during HART, all patients completed protocol therapy as planned. The median OS and progression-free survival were 22.3 months (95% confidence interval, 14.6-42.7 months) and 13.7 months (95% confidence interval, 8.0-33.3 months), respectively. The 4-year OS rates were 30.4% for the entire cohort and 53.3% and 14.0% for patients with methylated (n=21) and unmethylated (n=27) MGMT gene promoter tumors, respectively. One patient had grade 5 pancytopenia during HART, and another patient had transient grade 4 hepatotoxicity. A second surgical procedure was performed in 13 patients: 2 had intracranial infection, 3 had recurrences, 4 had recurrences and radiation-induced damage, and 4 had only radiation-induced damage.

CONCLUSIONS

This novel approach of neoadjuvant TMZ is associated with an encouraging favorable long-term survival with acceptable toxicity. A future comparative trial of the efficacy of this regimen is warranted.

Abstract 4235: Anti-proliferative effects of ZR2002, a novel combi-molecule with EGFR/DNA binary targeting properties compared to Gefitinib in glioblastoma cell lines and brain tumor stem cells

Glioblastoma multiforme (GBM) is the most aggressive form of primary brain tumor in adults with a survival of only 12-15 months. Brain tumor stem cells (BTSCs) contribute to tumor initiation, progression, chemo- and radioresistance, which accounts for tumor recurrence and treatment failure. Amplification of epidermal growth factor receptor (EGFR) is one of the most common genetic alterations associated with GBM aggressiveness. EGFR variant III (EGFRvIII) is an activating mutation that accounts for 60% of EGFR mutations in patients whose tumors show amplification of wild type EGFR. Despite the evidence that EGFR-induced pathway represents an attractive therapeutic target in GBM, gefitinib (Iressa™, ZD1839), an orally active, selective EGFR-tyrosine kinase inhibitor showed only a limited potency in clinical trials. ZR2002, a prototype of ‘combi-molecule’ capable of generating the binary EGFR/DNA targeting activity without requirement for hydrolytic cleavage has not been tested against BTSC. Given the ability of ZR2002 to concomitantly induce DNA damage and block EGFR-mediated signaling, we hypothesized that it would exert greater anti-proliferative activity than gefitinib in GBM tumor cell lines and BTSCs. To investigate our hypothesis, we used isogenic cell lines: U87EGFR wild-type (wt) and U87EGFRvIII (over-expressing EGFRvIII), U87MG (parental cell line) in addition to T98G, a GBM cell line known to express high levels of EGFR and BTSCs derived from patients newly diagnosed with GBM. BTSCs were cultured as neurospheres in stem cell media supplemented with growth factors (EGF, FGF), heparin and proliferation supplement. We examined the half maximal inhibitory concentration (IC50) of ZR2002 compared to gefitinib using MTT proliferation assay. Our results show that all cell lines tested were resistant to gefitinib when compared to ZR2002, which showed sub-micromolar potency in all tested cell lines following a short 2 h drug exposure. IC50s for T98G, U87-MG and U87-EGFRIII treated with ZR2002 were 0.019 μM, 0.048 μM and 0.073 μM, respectively. We further investigated the effect of ZR2002 in four different BTSC cell lines 48EF, OPK111, OPK164 and OPK161 and showed that the IC50s were in a similar range 0.027 μM, 0.014 μM, 0.089 μM and 0.019 μM, respectively. While GBM cell lines and BTSCs are highly resistant to gefitinib, they showed a greater sensitivity to ZR2002 (IC50 is less than 0.1 μM). These findings pave the way for developing single molecules with dual therapeutic modalities as a new strategy for GBM treatment. Additional pre-clinical studies are ongoing to evaluate the ability of ZR2002 to cross the blood brain barrier and its efficacy in an orthotopic tumor brain model. This research is funded by the Canadian Cancer Society grant #70217.

Citation Format: Zeinab Sharifi, Jean-Claude Bertrand, Kevin Petrecca, Elliot Goodfellow, Bassam Abdulkarim, Siham Sabri. Anti-proliferative effects of ZR2002, a novel combi-molecule with EGFR/DNA binary targeting properties compared to Gefitinib in glioblastoma cell lines and brain tumor stem cells. [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 4235. doi:10.1158/1538-7445.AM2015-4235

Comparison of radiation regimens in the treatment of Glioblastoma multiforme: results from a single institution

Background

The optimal fractionation schedule of radiotherapy (RT) for Glioblastoma multiforme (GBM) is yet to be determined. We aim to compare different fractionation regimens and identify prognostic factors to better tailor RT for newly diagnosed GBM patients.

Methods

All data for patients who underwent surgery for GBM between January 2005 and December 2012 were compiled. Clinical information was collected using patient charts and government registry. Cox analysis was used to identify variables affecting survival and treatment outcome.

Results

The median follow-up time was 13.2 months. Two hundred and seventy-six patients met the inclusion criteria, including 147 patients in the 60 Gy in 30 fractions (ConvRT) group, 86 patients in the 60 Gy in 20 fractions (HF60) group, and 43 patients in the 40 Gy in 15 fractions (HF40) group. Median survival (MS) was 16.0 months with a median progression-free survival (PFS) of 9.23 months in the ConvRT group. This was comparable to outcome in the HF60 group with MS 15.0 months and a median PFS of 9.1 months. Patients in the HF40 group had MS of 8 months, with a median PFS 5.4 months. Cox analysis showed no significant difference in OS between the ConvRT and HF60 groups but worse outcome in the HF40 group (HR 2.22, P = 0.04). MGMT methylation, extent of resection, use of chemotherapy, and repeat surgery were found to be significant independent prognostic factors for survival.

Conclusions

HF60 constitutes a safe RT approach that shows survival comparable to standard RT while allowing for a shorter treatment time.

Abstract 865: Evolving biological and clinical concepts of radiation delivery in NSCLC: response to ablative versus fractionated radiotherapy

Non-small cell lung cancer (NSCLC) patients account for over 80% of all lung cancer cases and have a poor outcome with current radiotherapy regimens. NSCLC has been the subject of many studies characterizing mechanisms of initiation, proliferation, invasion and treatment response. Recent trends in radiotherapy show an increase in the use of ablative radiotherapy (ART) in inoperable small size tumors. Clinical studies have shown response rates up to 90% in NSCLC patients treated with ART compared to 15-20% in patients treated with conventional fractionated radiotherapy (FRT). However, the biological determinants of this response have not been investigated and recent analysis of patterns of failure in patients treated with ART show an increased tendency towards distant metastatic recurrence.

We investigated the biological response of NSCLC cell lines with different molecular subtypes including, A549, H1975 and HCC827 to ART and FRT. Radiation doses of 8Gy and 12Gy were delivered in multiple fractions or single fraction. The response to radiation was investigated using several cellular assays including clonogenic survival, cell proliferation, matrigel invasion, wound-healing, morphological characterization and senescence-associated beta-galactosidase.

ART significantly reduced cell proliferation and clonogenic survival compared to FRT in A549 cells. In addition, a significant increase in the number of senescent cells as well as large, polynucleated cells was observed in the ART-treated group compared to the FRT-treated group. This differential response to delivery approach (ART vs FRT) was not observed in HCC827 or H1975 cells which harbor EGFR mutations. Both ART and FRT inhibited cell proliferation and clonogenic survival to similar levels in HCC827 and H1975 cells.

In contrast to reduced cell proliferation and clonogenicity, ART significantly increased the invasive phenotype of A549 cells, but not HCC827 or H1975 cells compared to FRT. Western blot analysis of several markers of invasion, including cMET, AKT, ERK, SPARC and FAK revealed a significant down regulation of SPARC in A549 cells exposed to ART, but not FRT. Further analysis of cells in Boyden chambers showed that ART-induced senescent cells are capable of migration/invasion.

Our results unequivocally demonstrate that response to ART is cell-line dependent. A549 cells, which harbor wild-type EGFR have a differential response to radiotherapy based on delivery approach. Furthermore, A549 cell exposed to ART have significantly increased invasive and migratory capacity compared to FRT. Our findings suggest that the extracellular matrix glycoprotein, SPARC is involved in the modulation of radiation-induced invasion/migration. These findings can have significant implications for NSCLC patients undergoing ART and underscore the importance of understanding the underlying biology for effective disease management.

Citation Format: Ayman J. Oweida, Zeinab Sherifi, Yaoxian Xu, Siham Sabri, Bassam Abdulkarim. Evolving biological and clinical concepts of radiation delivery in NSCLC: response to ablative versus fractionated radiotherapy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 865. doi:10.1158/1538-7445.AM2014-865

Abstract 2740: Identification of new binding partners of the DNA repair protein MGMT using a proteomic discovery-based approach in glioblastoma

Background: Glioblastoma multiforme (GBM) is characterized by aberrant angiogenesis and widespread invasion through the brain parenchyma. The DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) has been extensively characterized for its role in resistance to alkylating agents used in treatment of GBM. Our team discovered an inverse relationship between expression of MGMT and GBM angiogenesis and invasion. To gain new insights into how MGMT affects angiogenesis and invasion, we used a proteomic-based approach integrated with bioinformatics analysis to identify potential MGMT-binding partners (BPs) for the first time in GBM.

Methods: We used T98G, a human GBM cell line with constitutive expression of MGMT and performed direct immunoprecipitation (IP) of endogenous MGMT using an anti-MGMT antibody or the isotype control. Following elution of the antibody, proteins were resolved by SDS-PAGE, stained, excised from the gel then subjected to trypsin digestion and identified by liquid chromatography-tandem mass spectrometry using the LTQ-Orbitrap Elite mass analyzer. The resulting tryptic peptides were purified and identified by LC-tandem mass spectrometry (MS/MS). The resultant MS/MS spectra were searched against a proteome database for peptide matching and protein identification. Proteins identified with high confidence (Scaffold software) were used to construct the biological network of MGMT-BPs in GBM using the Build Network tool provided by MetaCore.

Results: We identified a total of 186 MGMT-BPs, which were not identified in the elution from the isotype control. Using gene ontology (GO) database, we determined the function and biological role of identified proteins (mitochondrial metabolism, DNA repair and replication, ubiquitin pathway, transcription regulators, RNA post-transcriptional processing, transcriptional splicing, protein biosynthesis and trafficking, cellular metabolism, cell cycle and division, response to stress and cell death, cell migration and invasion). The list of new BPs was uploaded to MetaCore and the most relevant biological process was enriched based on public GO databases. Among the top proteins identified with a very high confidence, we found newly identified MGMT-BPs, which may underlie the role of MGMT in angiogenesis and invasion, namely the splicing factor heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1), known for its role in the packaging of pre-mRNA into hnRNP particles and alternative splicing of angiogenic factors (VEGF-A and the fibroblast growth factor 2) and annexin A2. Knockdown of annexin A2 decreased invasion, angiogenesis and proliferation in vivo.

Conclusion: Our study provides new mechanistic insights into how MGMT affects angiogenesis and invasion in GBM, which may ultimately lead to the identification of new therapeutic targets to improve the poor outcome of this devastating disease.

Note: This abstract was not presented at the meeting.

Citation Format: Siham Sabri, Yaoxian Xu, Bassam Abdulkarim. Identification of new binding partners of the DNA repair protein MGMT using a proteomic discovery-based approach in glioblastoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2740. doi:10.1158/1538-7445.AM2014-2740

Adjuvant treatment of anaplastic oligodendrogliomas and oligoastrocytomas

BACKGROUND

Standard care of adjuvant treatment for anaplastic oligodendrogliomas (AO) and anaplastic oligoastrocytomas (AOA) is not yet well defined. The benefit of adjuvant chemotherapy and radiotherapy (RT), given as single modalities or sequentially, is still unclear. Furthermore, insight into the predictive and prognostic impact of various biomarkers is surging.

OBJECTIVES

To compare postoperative sequential RT and chemotherapy to RT alone in adults with newly diagnosed AO or mixed AOA. To evaluate the predictive and prognostic impact of the following biomarkers: codeletion of chromosomes 1p and 19q, O(6)-methylguanine-DNA methyltransferase (MGMT) promotor methylation and isocitrate dehydrogenase (IDH)-1 and -2 mutations.

SEARCH METHODS

We searched the Cochrane Central Register for Controlled Trials (CENTRAL, Issue 1, 2014), MEDLINE (2006 to March week 2, 2014) and EMBASE (2006 to week 11, 2014). We scanned reference lists from relevant studies for any additional articles.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) of adults with AO, AOA or anaplastic astrocytoma (AA) comparing adjuvant treatment of chemotherapy, RT, or sequential chemotherapy and RT. We excluded no specific chemotherapy regimens.

DATA COLLECTION AND ANALYSIS

We critically appraised and extracted data from relevant studies. Based on the differences in participant selection with respect to the definition of AO (two versus three high-risk anaplastic features), the inclusion of AA and sequence of treatment (RT and chemotherapy), we could not consider the results from the three RCTs for meta-analysis.

MAIN RESULTS

Three RCTs, with 931 participants, tested different neoadjuvant treatments: RT alone; sequential RT and procarbazine, lomustine and vincristine (PCV) chemotherapy; PCV chemotherapy alone; and temozolomide chemotherapy alone. None of the studies blinded participants or personnel, and, therefore, are considered at high risk of performance and detection bias. The studies were otherwise at low risk of bias. One study, the European Organisation for Research and Treatment of Cancer (EORTC) trial, demonstrated a statistically significant overall survival (OS) benefit for RT plus PCV, with a median OS of 3.5 years compared with 2.6 years in the RT alone arm (P value = 0.018). This result was reported 10 years after the conclusion of the enrolment, and was not apparent in the original 2008 Cochrane review. Furthermore, with retrospective evaluation of biomarkers, codeletion of complete chromosome arms 1p and 19q and IDH-1 or -2 mutation were independent prognostic factors for OS in two of the RCTs (Radiation Therapy Oncology Group (RTOG) and EORTC), and were predictive for OS in one trial (RTOG). The third trial (NOA-04) evaluated these biomarkers prospectively and found them prognostic for progression-free survival.

AUTHORS' CONCLUSIONS

Early PCV, either before or after RT, appears to improve OS of participants with AO or AOA. Use of biomarkers including codeletion of chromosomes 1p and 19q with or without IDH-1 or -2 mutation identify a subset of people with increased sensitivity to combined PCV and RT. The important role of biomarkers was supported in all of the RCTs examined, and prospective evaluation should be undertaken in future studies. However, PCV was associated with significant grade 3 and 4 toxicities, and whether temozolomide can be substituted for this remains unclear.

Abstract A192: Role of O(6)-Methylguanine-DNA Methyltransferase in the Proliferation/Invasion Dichotomy and Differential Effect of FAK inhibitor Y11 based on expression of MGMT in Glioblastoma

Introduction: Glioblastoma multiforme (GBM) is the most frequent and aggressive form of malignant primary brain tumors in adults. Prognosis for patinets diagnosed with GBM remains poor, with 90% of patients recurring within 2 years. Increased proliferation and invasion are the major hallmarks of GBM. Previous studies reported an inverse correlation between proliferation and invasion in GBM, a phenomenon termed the migration/proliferation dichotomy.

Our laboratory has established for the first time the role of MGMT The DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) as a potential negative regulator of GBM angiogenesis and invasion in GBM. SPARC (secreted protein acidic and rich in cysteine) is known for its pro-invasive and anti-proliferative effects in GBM. SPARC interacts with β1 integrin and activates focal adhesion kinase (FAK), a key regulator of migration and proliferation. FAK is overexpressed in patients diagnosed with GBM and has been proposed as a molecular target in GBM. Y11, a novel specific small molecule inhibitor highly selective for Tyr-397, the main autophosphorylation site of FAK has not been tested in GBM.

Methods: We used U87/Empty vector (U87/EV) negative for MGMT and its counterpart overexpressing MGMT (U87/MGMT), T98/EV with constitutive expression of MGMT and its knockdown counterpart T98/MGMT-shRNA in addition to GBM cell lines with different levels of MGMT expression (U251, U138, LN18 and A172). The effect of Y11 was investigated using MTT proliferation assay (inhibiting concentration at 50%) and western blotting to assess p-FAK- Tyr-397, Total FAK and SPARC levels.

Results: Using isogenic overexpression (U87/EV, U87MGMT) and knockdown (T98/EV, T98/shRNA) models of MGMT in GBM, we showed that expression of MGMT was associated with increased proliferation and decreased invasion. Western blotting (WB) analysis in isogenic cell lines for MGMT and other cell lines with different levels of MGMT expression (U251, U138, LN18 and A172) revealed a striking inverse relationship between expression of MGMT and SPARC. Importantly, we showed that treatment with the small molecule inhibitor Y11, which specifically inhibits FAK Tyr397 induced a dose dependent decrease of pFAK in all cell lines, while total FAK levels were unchanged. This decrease was accompanied by decreased proliferation in all cell lines.

Conclusion: Our study reveals that MGMT regulates the proliferation/invasion dichotomy through regulation of SPARC and FAK and highlights the differential effect of Y11 on proliferation and invasion based on expression of MGMT. This will lead to the identification of new biomarkers of invasion and proliferation and prospective therapies targeting molecular effectors involved in invasion and proliferation.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A192.

Citation Format: Kenny Chatoor, Siham Sabri, Bassam Abdulkarim. Role of O(6)-Methylguanine-DNA Methyltransferase in the Proliferation/Invasion Dichotomy and Differential Effect of FAK inhibitor Y11 based on expression of MGMT in Glioblastoma. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A192.

Abstract A66: Ablative radiotherapy increases invasion potential in EGFR-wildtype non-small cell lung cancer cells compared to fractionated radiotherapy

Introduction: Non-small cell lung cancer (NSCLC) accounts for over 80% of all lung cancer cases. Nearly 70% of lung cancer patients will undergo radiotherapy (RT). Recent trends in RT have shown an increase in the use of ablative radiotherapy (ART) in inoperable small tumors with response rates of 80-90% in NSCLC patients. However, despite the high rate of local control, early clinical data shows no advantage in survival due to distant metastasis after ART compared to conventional fractionated radiotherapy (FRT). In addition, patient selection for ART is independent of the status of the epidermal growth factor receptor (EGFR) which has been shown to play a role in radiation response. We investigated the effect of ART compared to FRT on cell invasion, proliferation, senescence and clonogenic survival of NSCLC cell lines harboring wild type and mutated EGFR.

Methods: The cell lines used were A549, H1975 and HCC827. Cell irradiation was performed using a Faxitron X-Ray machine. Radiation doses of 8Gy and12Gy were delivered in fractionated or single sessions. The effect of radiation on cells was investigated using the clonogenic assay, MTT proliferation assay, matrigel invasion assay and senescence-associated beta-galactosidase.

Results: ART significantly suppressed the proliferative and clonogenic potential of wild-type EGFR A549 cells compared to FRT. In addition, a significant increase in the number of senescent as well as large, polynucleated cells was observed in the ART-treated group compared to the FRT-treated group. Analysis of the invasive potential of the cells revealed a 2-fold increase in invasion 5 days after exposure to ART of 12Gy compared to control. The FRT group showed a 1.4-fold increase in invasion compared to control. Contrary to A549 cells, EGFR-mutated NSCLC HCC827 and H1975 cells, showed no significant difference after exposure to ART compared to FRT. In addition, both ART and FRT-treated groups showed a similar increase in the number of senescent, large and polynucleated cells. A significant reduction in the number of invading cells after exposure to either FRT or ART was observed compared to the control.

Conclusion: ART significantly reduces cell proliferation and clonogenic survival compared to FRT in wild-type EGFR A549 cells. This differential response between the type of treatment (ART vs FRT) was not seen in NSCLC cell lines harboring EGFR mutations. In contrast to reduced cell proliferation, there was a significant increase in the invasive capacity of cells after ART compared to FRT in A549 cells only. These results can have significant consequences in the selection and treatment of NSCLC patients for ART.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A66.

Citation Format: Ayman J. Oweida, Jack Xu, Siham Sabri, Bassam Abdulkarim. Ablative radiotherapy increases invasion potential in EGFR-wildtype non-small cell lung cancer cells compared to fractionated radiotherapy. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A66.

Abstract C2: Cross-talk between the O(6)-Methylguanine-DNA methyltransferase (MGMT) and p53 in glioblastoma multiforme

Background. Glioblastoma multiforme (GBM) is a fatal malignant primary brain tumor in adults with a median survival time of approximately 14.6 months, despite treatment with surgery, concurrent radiation therapy (RT) and the alkylating agent temozolomide (TMZ). O(6)-Methylguanine-DNA methyltransferase (MGMT) is a DNA repair protein involved in resistance to TMZ in GBM. Our group showed that MGMT is a critical regulator of GBM angiogenesis, invasion and response to antiangiogenic treatment (sunitinib). While sunitinib treatment significantly decreased invasion in MGMT-positive cell lines, it led to a significant increase of invasion in MGMT-negative cell lines. Our group launched the first phase II clinical trial of concurrent sunitinib with RT and TMZ for selected patients with MGMT-positive tumors. The p53 tumor suppressor protein is involved in proliferation, angiogenesis and response to RT. Previous studies showed the effect of p53 in regulating MGMT levels. The role of MGMT and p53 in response to RT and sunitinib is unknown. We hypothesize that MGMT may affect levels of p53 and response to RT and sunitinib treatment.

Results. We used isogenic human GBM cell lines isogenic for MGMT and assessed p53 levels by Western blotting and immunofluorescence. We showed for the first time that stable transfection of GBM cell line negative for MGMT (U87MG) and harboring wild type TP53 with a vector encoding for MGMT (U87MGMT) led to significant increase of p53 expression and its nuclear localization. Strikingly, increased p53 in U87MGMT cells did not lead to increased p21 protein, one of the main targets of p53. As shown by western blotting analysis, ionizing radiation (6 and 10 Gy) did not increase p21 levels compared to sham control. Interestingly, it was previously shown that irradiation does not lead to p21 activation in GBM cells with basal overexpression of p21 mRNA and can even lead to its repression as a mechanism of resistance to RT. We suggest that MGMT could be an upstream regulator of this resistance.

Conclusion. Our study revealed a novel mechanism for regulation of p53 through MGMT, which may affect response to RT in GBM. We will further establish the relationship between MGMT/p53 status and response to combined RT and sunitinib in GBM cell lines and samples from patients enrolled in our clinical trial. This will lead to more efficient strategies of treatment for patients with tumors unresponsive to combined RT and sunitinib.

Grant acknowledgments. This work has been funded by the Cedar Cancer Foundation, Research Institute of McGill University Health Center and the McGill-CIHR Drug Development Training Program (DDTP).

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C2.

Citation Format: Mariia Patyka, Bassam Abdulkarim, Yaoxian Xu, Siham Sabri. Cross-talk between the O(6)-Methylguanine-DNA methyltransferase (MGMT) and p53 in glioblastoma multiforme. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C2.