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.