A Prospective Phase I/II Clinical Trial of High-Dose Proton Therapy for Chordomas and Chondrosarcomas

Purpose

The purpose of this study was to evaluate the feasibility and safety of dose-escalated proton beam therapy for treating chordomas and chondrosarcomas of the skull base and spine. Methods: A prospective cohort of 54 patients (42 with chordomas and 12 with chondrosarcomas) was enrolled between 2010 and 2018. The primary endpoints were feasibility and <20% rate of acute grade ≥3 toxicity, and secondary endpoints included cancer-specific outcomes and toxicities. Patients were followed with magnetic resonance imaging or computed tomography at 3-month intervals. Proton beam therapy was delivered with doses up to 79.2 Gy using protons only, combination protons/intensity modulated radiation therapy (IMRT), or IMRT only.

Results

Feasibility endpoints were met, with only 2 out of 54 patient radiation therapy plans failing to meet dosimetric constraints with protons, and 4 out of 54 experiencing a delay or treatment break >5 days, none for toxicities related to treatment. There were no grade 4 acute toxicities and 1 grade 3 acute toxicity (sensory neuropathy). The only 2 grade 3 late toxicities recorded, osteoradionecrosis and intranasal carotid blowout (mild and not emergently treated), occurred in a single patient. We report overall survival as 83% at 5 years, with local failure-free survival and progression-free survival rates of 72% and 68%, respectively. Five patients developed distant disease, and among the 9/54 patients who died, 4 deaths were not attributed to treatment or recurrence.

Conclusions

Our findings suggest that high-dose proton therapy alone or in combination with IMRT is a safe and effective treatment option for chordomas and chondrosarcomas of the skull base and spine.

Spatial analysis of tissue immunity and vascularity by light sheet fluorescence microscopy

The pathogenesis of cancer and cardiovascular diseases is subjected to spatiotemporal regulation by the tissue microenvironment. Multiplex visualization of the microenvironmental components, including immune cells, vasculature and tissue hypoxia, provides critical information underlying the disease progression and therapy resistance, which is often limited by imaging depth and resolution in large-volume tissues. To this end, light sheet fluorescence microscopy, following tissue clarification and immunostaining, may generate three-dimensional high-resolution images at a whole-organ level. Here we provide a detailed description of light sheet fluorescence microscopy imaging analysis of immune cell composition, vascularization, tissue perfusion and hypoxia in mouse normal brains and hearts, as well as brain tumors. We describe a procedure for visualizing tissue vascularization, perfusion and hypoxia with a transgenic vascular labeling system. We provide the procedures for tissue collection, tissue semi-clearing and immunostaining. We further describe standard methods for analyzing tissue immunity and vascularity. We anticipate that this method will facilitate the spatial illustration of structure and function of the tissue microenvironmental components in cancer and cardiovascular diseases. The procedure requires 1-2 weeks and can be performed by users with expertise in general molecular biology.

An immunosuppressive vascular niche drives macrophage polarization and immunotherapy resistance in glioblastoma

Cancer immunity is subjected to spatiotemporal regulation by leukocyte interaction with neoplastic and stromal cells, contributing to immune evasion and immunotherapy resistance. Here, we identify a distinct mesenchymal-like population of endothelial cells (ECs) that form an immunosuppressive vascular niche in glioblastoma (GBM). We reveal a spatially restricted, Twist1/SATB1-mediated sequential transcriptional activation mechanism, through which tumor ECs produce osteopontin to promote immunosuppressive macrophage (Mφ) phenotypes. Genetic or pharmacological ablation of Twist1 reverses Mφ-mediated immunosuppression and enhances T cell infiltration and activation, leading to reduced GBM growth and extended mouse survival, and sensitizing tumor to chimeric antigen receptor T immunotherapy. Thus, these findings uncover a spatially restricted mechanism controlling tumor immunity and suggest that targeting endothelial Twist1 may offer attractive opportunities for optimizing cancer immunotherapy.

Cell plasticity, senescence, and quiescence in cancer stem cells: Biological and therapeutic implications

Cancer stem cells (CSCs) are a distinct population of cells within tumors with capabilities of self-renewal and tumorigenicity. CSCs play a pivotal role in cancer progression, metastasis, and relapse and tumor resistance to cytotoxic therapy. Emerging scientific evidence indicates that CSCs adopt several mechanisms, driven by cellular plasticity, senescence and quiescence, to maintain their self-renewal capability and to resist tumor microenvironmental stress and treatments. These pose major hindrances for CSC-targeting anti-cancer therapies: cell plasticity maintains stemness in CSCs and renders tumor cells to acquire stem-like phenotypes, contributing to tumor heterogeneity and CSC generation; cellular senescence induces genetic reprogramming and stemness activation, leading to CSC-mediated tumor progression and metastasis; cell quienscence facilitates CSC to overcome their intrinsic vulnerabilities and therapeutic stress, inducing tumor relapse and therapy resistance. These mechanisms are subjected to spatiotemporal regulation by hypoxia, CSC niche, and extracellular matrix in the tumor microenvironment. Here we integrate the recent advances and current knowledge to elucidate the mechanisms involved in the regulation of plasticity, senescence and quiescence of CSCs and the potential therapeutic implications for the future.

Gamma Knife radiosurgery for trigeminal neuralgia provides greater pain relief at higher dose rates

In Gamma Knife (GK) radiosurgery, dose rate decreases during the life cycle of its radiation source, extending treatment times. Prolonged treatments influence the amount of sublethal radiation injury that is repaired during exposure, and is associated with decreased biologically-equivalent dose (BED). We assessed the impact of treatment times on clinical outcomes following GK of the trigeminal nerve - a rare clinical model to isolate the effects of treatment times. This is a retrospective analysis of 192 patients with facial pain treated across three source exchanges. All patients were treated to 80 Gy with a single isocenter. Treatment time was analyzed in terms of patient anatomy-specific dose rate, as well as BED calculated from individual patient beam-on times. An outcome tool measuring pain in three distinct domains (pain intensity, interference with general and oro-facial activities of daily living), was administered before and after intervention. Multivariate linear regression was performed with dose rate/BED, brainstem dose, sex, age, diagnosis, and prior intervention as predictors. BED was an independent predictor of the degree of improvement in all three dimensions of pain severity. A decrease in dose rate by 1.5 Gy/min corresponded to 31.8% less improvement in the overall severity of pain. Post-radiosurgery incidence of facial numbness was increased for BEDs in the highest quartile. Treatment time is an independent predictor of pain outcomes, suggesting that prescription dose should be customized to ensure iso-effective treatments, while accounting for the possible increase in adverse effects at the highest BEDs.

Multiblock Discriminant Analysis of Integrative 18F-FDG-PET/CT Radiomics for Predicting Circulating Tumor Cells in Early-Stage Non-small Cell Lung Cancer Treated With Stereotactic Body Radiation Therapy

PURPOSE

The main objective of the present study was to integrate 18F-FDG-PET/CT radiomics with multiblock discriminant analysis for predicting circulating tumor cells (CTCs) in early-stage non-small cell lung cancer (ES-NSCLC) treated with stereotactic body radiation therapy (SBRT).

METHODS

Fifty-six patients with stage I NSCLC treated with SBRT underwent 18F-FDG-PET/CT imaging pre-SBRT and post-SBRT (median, 5 months; range, 3-10 months). CTCs were assessed via a telomerase-based assay before and within 3 months after SBRT and dichotomized at 5 and 1.3 CTCs/mL. Pre-SBRT, post-SBRT, and delta PET/CT radiomics features (n = 1548 × 3/1562 × 3) were extracted from gross tumor volume. Seven feature blocks were constructed including clinical parameters (n = 12). Multiblock data integration was performed using block sparse partial least squares-discriminant analysis (sPLS-DA) referred to as Data Integration Analysis for Biomarker Discovery Using Latent Components (DIABLO) for identifying key signatures by maximizing common information between different feature blocks while discriminating CTC levels. Optimal input blocks were identified using a pairwise combination method. DIABLO performance for predicting pre-SBRT and post-SBRT CTCs was evaluated using combined AUC (area under the curve, averaged across different blocks) analysis with 20 × 5-fold cross-validation (CV) and compared with that of concatenation-based sPLS-DA that consisted of combining all features into 1 block. CV prediction scores between 1 class versus the other were compared using the Wilcoxon rank sum test.

RESULTS

For predicting pre-SBRT CTCs, DIABLO achieved the best performance with combined pre-SBRT PET radiomics and clinical feature blocks, showing CV AUC of 0.875 (P = .009). For predicting post-SBRT CTCs, DIABLO achieved the best performance with combined post-SBRT CT and delta CT radiomics feature blocks, showing CV AUCs of 0.883 (P = .001). In contrast, all single-block sPLS-DA models could not attain CV AUCs higher than 0.7.

CONCLUSIONS

Multiblock integration with discriminant analysis of 18F-FDG-PET/CT radiomics has the potential for predicting pre-SBRT and post-SBRT CTCs. Radiomics and CTC analysis may complement and together help guide the subsequent management of patients with ES-NSCLC.

Synergistic immunotherapy of glioblastoma by dual targeting of IL-6 and CD40

Immunologically-cold tumors including glioblastoma (GBM) are refractory to checkpoint blockade therapy, largely due to extensive infiltration of immunosuppressive macrophages (Mϕs). Consistent with a pro-tumor role of IL-6 in alternative Mϕs polarization, we here show that targeting IL-6 by genetic ablation or pharmacological inhibition moderately improves T-cell infiltration into GBM and enhances mouse survival; however, IL-6 inhibition does not synergize PD-1 and CTLA-4 checkpoint blockade. Interestingly, anti-IL-6 therapy reduces CD40 expression in GBM-associated Mϕs. We identify a Stat3/HIF-1α-mediated axis, through which IL-6 executes an anti-tumor role to induce CD40 expression in Mϕs. Combination of IL-6 inhibition with CD40 stimulation reverses Mϕ-mediated tumor immunosuppression, sensitizes tumors to checkpoint blockade, and extends animal survival in two syngeneic GBM models, particularly inducing complete regression of GL261 tumors after checkpoint blockade. Thus, antibody cocktail-based immunotherapy that combines checkpoint blockade with dual-targeting of IL-6 and CD40 may offer exciting opportunities for GBM and other solid tumors.

Personal and Prognostic: Tissue and Liquid Biomarkers of Radiotherapeutic Response in Non-Small Cell Lung Cancer

Recent treatment advances have improved outcomes for patients with non-small cell lung cancer (NSCLC), often utilizing tumor molecular characterization to identify targetable mutations. This is further enhanced by advancements in "liquid biopsies", using peripheral blood for noninvasive, serial sampling of tumor biology. While tumor genomic alterations have established therapeutic implications in metastatic NSCLC, research is also ongoing to develop applications for tissue and liquid biomarkers in earlier stage disease, such as patients treated with radiation for early stage or locoregional NSCLC.

Targeting PAK4 to reprogram the vascular microenvironment and improve CAR-T immunotherapy for glioblastoma

Malignant solid tumors are characterized by aberrant vascularity that fuels the formation of an immune-hostile microenvironment and induces resistance to immunotherapy. Vascular abnormalities may be driven by pro-angiogenic pathway activation and genetic reprogramming in tumor endothelial cells (ECs). Here, our kinome-wide screening of mesenchymal-like transcriptional activation in human glioblastoma (GBM)-derived ECs identifies p21-activated kinase 4 (PAK4) as a selective regulator of genetic reprogramming and aberrant vascularization. PAK4 knockout induces adhesion protein re-expression in ECs, reduces vascular abnormalities, improves T cell infiltration and inhibits GBM growth in mice. Moreover, PAK4 inhibition normalizes the tumor vascular microenvironment and sensitizes GBM to chimeric antigen receptor-T cell immunotherapy. Finally, we reveal a MEF2D/ZEB1- and SLUG-mediated mechanism by which PAK4 reprograms the EC transcriptome and downregulates claudin-14 and VCAM-1 expression, enhancing vessel permeability and reducing T cell adhesion to the endothelium. Thus, targeting PAK4-mediated EC plasticity may offer a unique opportunity to recondition the vascular microenvironment and strengthen cancer immunotherapy.

Combined fluorescence-guided surgery and photodynamic therapy for glioblastoma multiforme using cyanine and chlorin nanocluster

INTRODUCTION

Glioblastoma multiforme (GBM) is the most common primary intracranial malignancy; survival can be improved by maximizing the extent-of-resection.

METHODS

A near-infrared fluorophore (Indocyanine-Green, ICG) was combined with a photosensitizer (Chlorin-e6, Ce6) on the surface of superparamagnetic-iron-oxide-nanoparticles (SPIONs), all FDA-approved for clinical use, yielding a nanocluster (ICS) using a microemulsion. The physical-chemical properties of the ICS were systematically evaluated. Efficacy of photodynamic therapy (PDT) was evaluated in vitro with GL261 cells and in vivo in a subtotal resection trial using a syngeneic flank tumor model. NIR imaging properties of ICS were evaluated in both a flank and an intracranial GBM model.

RESULTS

ICS demonstrated high ICG and Ce6 encapsulation efficiency, high payload capacity, and chemical stability in physiologic conditions. In vitro cell studies demonstrated significant PDT-induced cytotoxicity using ICS. Preclinical animal studies demonstrated that the nanoclusters can be detected through NIR imaging in both flank and intracranial GBM tumors (ex: 745 nm, em: 800 nm; mean signal-to-background 8.5 ± 0.6). In the flank residual tumor PDT trial, subjects treated with PDT demonstrated significantly enhanced local control of recurrent neoplasm starting on postoperative day 8 (23.1 mm3 vs 150.5 mm3, p = 0.045), and the treatment effect amplified to final mean volumes of 220.4 mm3 vs 806.1 mm3 on day 23 (p = 0.0055).

CONCLUSION

A multimodal theragnostic agent comprised solely of FDA-approved components was developed to couple optical imaging and PDT. The findings demonstrated evidence for the potential theragnostic benefit of ICS in surgical oncology that is conducive to clinical integration.

Circulating Tumor Cells Are Associated with Recurrent Disease in Patients with Early-Stage Non-Small Cell Lung Cancer Treated with Stereotactic Body Radiotherapy

PURPOSE

Although stereotactic body radiotherapy (SBRT) is effective in early-stage non-small cell lung cancer (NSCLC), approximately 10%-15% of patients will fail regionally and 20%-25% distantly. We evaluate a novel circulating tumor cell (CTC) assay as a prognostic marker for increased risk of recurrence following SBRT.

EXPERIMENTAL DESIGN

Ninety-two subjects (median age, 71 years) with T1a (64%), T1b (23%), or T2a (13%) stage I NSCLC treated with SBRT were prospectively enrolled. CTCs were enumerated by utilizing a GFP-expressing adenoviral probe that detects elevated telomerase activity in cancer cells. Samples were obtained before, during, and serially up to 24 months after treatment. SBRT was delivered to a median dose of 50 Gy (range, 40-60 Gy), mostly commonly in four to five fractions (92%).

RESULTS

Thirty-eight of 92 subjects (41%) had a positive CTC test prior to SBRT. A cutoff of ≥5 CTCs/mL before treatment defined favorable (n = 78) and unfavorable (n = 14) prognostic groups. Increased risk of nodal (P = 0.04) and distant (P = 0.03) failure was observed in the unfavorable group. Within 3 months following SBRT, CTCs continued to be detected in 10 of 35 (29%) subjects. Persistent detection of CTCs was associated with increased risk of distant failure (P = 0.04) and trended toward increased regional (P = 0.08) and local failure (P = 0.16).

CONCLUSIONS

Higher pretreatment CTCs and persistence of CTCs posttreatment is significantly associated with increased risk of recurrence outside the targeted treatment site. This suggests that CTC analysis may potentially identify patients at higher risk for regional or distant recurrences and who may benefit from either systemic therapy and/or timely locoregional salvage treatment.

A Patient-Derived Glioblastoma Organoid Model and Biobank Recapitulates Inter- and Intra-tumoral Heterogeneity

Glioblastomas exhibit vast inter- and intra-tumoral heterogeneity, complicating the development of effective therapeutic strategies. Current in vitro models are limited in preserving the cellular and mutational diversity of parental tumors and require a prolonged generation time. Here, we report methods for generating and biobanking patient-derived glioblastoma organoids (GBOs) that recapitulate the histological features, cellular diversity, gene expression, and mutational profiles of their corresponding parental tumors. GBOs can be generated quickly with high reliability and exhibit rapid, aggressive infiltration when transplanted into adult rodent brains. We further demonstrate the utility of GBOs to test personalized therapies by correlating GBO mutational profiles with responses to specific drugs and by modeling chimeric antigen receptor T cell immunotherapy. Our studies show that GBOs maintain many key features of glioblastomas and can be rapidly deployed to investigate patient-specific treatment strategies. Additionally, our live biobank establishes a rich resource for basic and translational glioblastoma research.

Rapid and ultrasensitive digital PCR (dPCR) profiling of EGFRvIII in tumor cells and tissues

Background

Amplification of the epidermal growth factor receptor (EGFR) gene is commonly found in glioblastoma (GBM). About 57% GBM overexpresses EGFR and are associated with tumor progression, poor prognosis, and shorter life expectancy. Molecular profiling of solid tumors usually takes several weeks and may be biased by intrinsic tumor heterogeneity.

Methods

The unique sequence created by the fusion of exon 1 and exon 8 in EGFRvIII was used to guide the design of primers and a Minor Groove Binder (MGB) probe. Extracted total RNA was reverse transcribed and pre-amplified by PCR, followed by detection of the EGFRvIII mutation by dPCR.

Results

The lowest limit of quantification of our EGFRvIII assay was 0.003%. The EGFRvIII variant was identified in patient-derived glioma neurosphere cell lines, xenograft mouse model, and patient-derived tumor specimens. The overall workflow can be accomplished within 24 hours. In certain samples, EGFRvIII was detected when next-generation sequencing was unable to identify the variant. This finding highlights the ability of the dPCR assay to identify EGFRvIII mutations in heterogeneous solid tumors such as GBM in a rapid fashion by profiling samples from spatially distinct areas of tumors from the same patient.

Conclusions

In this study, we developed a highly sensitive digital PCR (dPCR) platform and leveraged our assay to detect the variant III alteration of EGFR (EGFRvIII) and amplified EGFR in patient-derived glioma neurosphere cell lines, orthotopic xenograft GBM mouse models, and patient-derived tumor specimens in less than 24 hours from minute quantities of starting material.

Clinical activity of the EGFR tyrosine kinase inhibitor osimertinib in EGFR-mutant glioblastoma

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults and carries a dismal prognosis. The EGFR gene is among the most commonly deranged genes in GBM and thus an important therapeutic target. We report the case of a young female with heavily pretreated EGFR-mutated GBM, for whom we initiated osimertinib, an oral, third-generation tyrosine kinase inhibitor that irreversibly inhibits EGFR and has significant brain penetration. We then review some of the main challenges in targeting EGFR, including lack of central nervous system penetration with most tyrosine kinase inhibitors, molecular heterogeneity of GBM and the need for enhanced specificity for the EGFR mutations relevant in GBM.

Early Detection of Recurrence in Patients With Locally Advanced Non-Small-Cell Lung Cancer via Circulating Tumor Cell Analysis

BACKGROUND

Assays to identify circulating tumor cells (CTCs) might allow for noninvasive and sequential monitoring of lung cancer. We investigated whether serial CTC analysis could complement conventional imaging for detecting recurrences after treatment in patients with locally advanced non-small-cell lung cancer (LA-NSCLC).

PATIENTS AND METHODS

Patients with LA-NSCLC (stage II-III) who definitively received concurrent chemoradiation were prospectively enrolled, with CTCs from peripheral blood samples identified using an adenoviral probe that detects elevated telomerase activity present in nearly all lung cancer cells. A "detectable" CTC level was defined as 1.3 green flourescent protein-positive cells per milliliter of collected blood. Samples were obtained before, during (at weeks 2, 4, and 6), and after treatment (post-radiation therapy [RT]; at months 1, 3, 6, 12, 18, and 24).

RESULTS

Forty-eight patients were enrolled. At a median follow-up of 10.9 months, 22 (46%) patients had disease recurrence at a median time of 7.6 months post-RT (range, 1.3-32.0 months). Of the 20 of 22 patients for whom post-RT samples were obtained, 15 (75%) had an increase in CTC counts post-RT. In 10 of these 15 patients, CTCs were undetectable on initial post-RT draw but were then detected again before radiographic detection of recurrence, with a median lead time of 6.2 months and mean lead time of 6.1 months (range, 0.1-12.0 months) between CTC count increase and radiographic evidence of recurrence. One patient with an early recurrence (4.7 months) had persistently elevated detectable CTC levels during and after treatment.

CONCLUSION

These results indicate that longitudinal CTC monitoring in patients with LA-NSCLC treated with chemoradiation is feasible, and that detectable CTC levels in many patients meaningfully precede radiologic evidence of disease recurrence.

A prospective clinical trial of proton therapy for chordoma and chondrosarcoma: Feasibility assessment

BACKGROUND/OBJECTIVES

Proton therapy (PRT) has emerged as a treatment option for chordomas/chondrosarcomas to escalate radiation dose more safely. We report results of a phase I/II trial of PRT in patients with chordoma/chondrosarcoma.

METHODS

Twenty adult patients with pathologically confirmed, nonmetastatic chordoma or chondrosarcoma were enrolled in a single-institution prospective trial of PRT from 2010 to 2014. Seventeen patients received adjuvant PRT and three received definitive PRT. Median dose was 73.8 Gy(RBE; range 68.4-79.2 Gy) using PRT-only (n = 6) or combination PRT/intensity-modulated radiotherapy (IMRT) (n = 14). Quality-of-life (QOL) and fatigue were assessed weekly and every 3 months posttreatment with the Functional Assessment of Cancer Therapy - Brain (FACTBr) and Brief Fatigue Inventory. Primary endpoint was feasibility (90% completing treatment with < 10 day treatment delay and ≤ 20% unexpected acute grade ≥ 3 toxicity).

RESULTS

Tumors included chordomas of the skull base (n = 10), sacrum (n = 5), and cervical spine (n = 3), and skull base chondrosarcomas (n = 2). Median age was 57. The 80% had positive margins/gross disease. Median follow-up was 37 months. Feasibility endpoints were met. The 3-year local control and progression-free survival was 86% and 81%. There were no deaths. Two patients had acute grade 3 toxicity (both fatigue). One had late grade 3 toxicity (epistaxis and osteoradionecrosis). There were no significant differences in patient reported fatigue or QOL from baseline to the end-of-treatment.

CONCLUSIONS

We report favorable local control, survival, and toxicity following PRT.

Circulating Glioma Cells Exhibit Stem Cell-like Properties

: Circulating tumor cells (CTC) are known to be present in the blood of patients with glioblastoma (GBM). Here we report that GBM-derived CTC possess a cancer stem cell (CSC)-like phenotype and contribute to local tumorigenesis and recurrence by the process of self-seeding. Genetic probes showed that mouse GBM-derived CTC exhibited Sox2/ETn transcriptional activation and expressed glioma CSC markers, consistent with robust expression of stemness-associated genes including SOX2, OCT4, and NANOG in human GBM patient-derived samples containing CTC. A transgenic mouse model demonstrated that CTC returned to the primary tumor and generated new tumors with enhanced tumorigenic capacity. These CTCs were resistant to radiotherapy and chemotherapy and to circulation stress-induced cell apoptosis. Single-cell RNA-seq analysis revealed that Wnt activation induced stemness and chemoresistance in CTC. Collectively, these findings identify GBM-derived CTC as CSC-like cells and suggest that targeting Wnt may offer therapeutic opportunities for eliminating these treatment-refractory cells in GBM. SIGNIFICANCE: These findings identify CTCs as an alternative source for in situ tumor invasion and recurrence through local micrometastasis, warranting eradication of systemic "out-of-tumor" CTCs as a promising new therapeutic opportunity for GBM.

Abstract A063: Identification of an integrated stress response-inducing agent (NH125) that modulates DR5-dependent TRAIL synergy and ATF3-driven cell death in gliomaspheres

Purpose: The high incidence of glioblastoma recurrence necessitates additional therapeutic strategies to improve outcomes. One potential strategy targets treatment resistant cells via the integrated stress response (ISR) pathway as a means of sensitizing these cells to TNF-related apoptosis-inducing ligand (TRAIL). Methods: We generated a novel cell-based death receptor assay and used this assay to screen compounds from three commercially available libraries (total of 223 compounds) at 2 or 10 μM (Z prime = 0.64). A single hit was identified that was further characterized by immunoblotting and immunofluorescence. A compound dilution series was applied to a panel of cell lines including patient-derived glioma stem cells (GSC). IC50 values were calculated by fitting normalized viability data to a modified Hill Equation. TRAIL synergy was assessed using the combination index method following treatment with compound and TRAIL. Knockout of C/EBP Homologous Protein (CHOP) was used to determine the role of integrated stress in TRAIL synergy. GSC were also treated with temozolomide followed by assessment of cell viability. RNA-seq analysis was performed on compound treated GSC, U251, and Normal Human Astrocytes. Short hairpin RNAs were used to establish the role of ATF3 in compound-treated GSC. Results: Using a novel cell-based death receptor we identified 1-Benzyl-3-cetyl-2-methylimidazolium iodide (NH125) as a potent inducer of DR5 expression. NH125 signals through the EIF2α-ATF4-CHOP axis, culminating in DR5 expression at low micromolar doses. CHOP is required for NH125-mediated TRAIL synergy. Compared to other cancer cell lines, GSC demonstrate an increased sensitivity to NH125 treatment, and synergize with TRAIL at lower doses than U251. NH125 produced a significant decrease in GSC viability when compared to temozolomide treatment (p &lt; 0.05). This enhanced sensitivity of GSC is partially due to increased expression of ATF3 following NH125 treatment. Conclusions: NH125 generates an integrated stress response leading to CHOP-mediated TRAIL synergy. Patient-derived glioma stem cells demonstrate increased sensitivity to NH125 treatment that is partially driven by increased ATF3 expression. Engaging the ISR to enhance the efficacy of TRAIL represents a promising strategy to target the treatment refractory GSC that have been implicated in glioblastoma recurrence. IC50 valuesCell LineIC50 (μM)Adj R2T4213-GSC0.89 ± 0.110.99NS039-GSC1.95 ± 0.350.99HK2962.51 ± 0.410.97U2513.30 ± 0.160.99Ovcar34.68 ± 0.340.97A5496.06 ± 0.230.99GL2616.20 ± 0.400.97U87-MG7.15 ± 0.160.98H129911.02 ± 0.430.99

Citation Format: Saad Sheikh, Xiaobing Tian, Deeksha Saxena, Xiangsheng Xu, Gary Kao, Jay F. Dorsey. Identification of an integrated stress response-inducing agent (NH125) that modulates DR5-dependent TRAIL synergy and ATF3-driven cell death in gliomaspheres [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A063.

Alpha Particle Enhanced Blood Brain/Tumor Barrier Permeabilization in Glioblastomas Using Integrin Alpha-v Beta-3-Targeted Liposomes

Glioblastoma (GBM) is the most common primary malignant astrocytoma characterized by extensive invasion, angiogenesis, hypoxia, and micrometastasis. Despite the relatively leaky nature of GBM blood vessels, effective delivery of antitumor therapeutics has been a major challenge due to the complications caused by the blood-brain barrier (BBB) and the highly torturous nature of newly formed tumor vasculature (blood tumor barrier-BTB). External beam radiotherapy was previously shown to be an effective means of permeabilizing central nervous system (CNS) barriers. By using targeted short-ranged radionuclides, we show for the first time that our targeted actinium-225-labeled α_vβ₃-specific liposomes (²²⁵Ac-IA-TLs) caused catastrophic double stranded DNA breaks and significantly enhanced the permeability of BBB and BTB in mice bearing orthotopic GBMs. Histologic studies revealed characteristic α-particle induced double strand breaks within tumors but was not significantly present in normal brain regions away from the tumor where BBB permeability was observed. These findings indicate that the enhanced vascular permeability in these distal regions did not result from direct α-particle-induced DNA damage. On the basis of these results, in addition to their direct antitumor effects, ²²⁵Ac-IA-TLs can potentially be used to enhance the permeability of BBB and BTB for effective delivery of systemically administered antitumor therapeutics. Mol Cancer Ther; 16(10); 2191-200. ©2017 AACR.

Theranostic Application of Mixed Gold and Superparamagnetic Iron Oxide Nanoparticle Micelles in Glioblastoma Multiforme

The treatment of glioblastoma multiforme, the most prevalent and lethal form of brain cancer in humans, has been limited in part by poor delivery of drugs through the blood-brain barrier and by unclear delineation of the extent of infiltrating tumor margins. Nanoparticles, which selectively accumulate in tumor tissue due to their leaky vasculature and the enhanced permeability and retention effect, have shown promise as both therapeutic and diagnostic agents for brain tumors. In particular, superparamagnetic iron oxide nanoparticles (SPIONs) have been leveraged as T2-weighted MRI contrast agents for tumor detection and imaging; and gold nanoparticles (AuNP) have been demonstrated as radiosensitizers capable of propagating electron and free radical-induced radiation damage to tumor cells. In this study, we investigated the potential applications of novel gold and SPION-loaded micelles (GSMs) coated by polyethylene glycol-polycaprolactone (PEG-PCL) polymer. By quantifying gh2ax DNA damage foci in glioblastoma cell lines, we tested the radiosensitizing efficacy of these GSMs, and found that GSM administration in conjunction with radiation therapy (RT) led to ~2-fold increase in density of double-stranded DNA breaks. For imaging, we used GSMs as a contrast agent for both computed tomography (CT) and magnetic resonance imaging (MRI) studies of stereotactically implanted GBM tumors in a mouse model, and found that MRI but not CT was sufficiently sensitive to detect and delineate tumor borders after administration and accumulation of GSMs. These results suggest that with further development and testing, GSMs may potentially be integrated into both imaging and treatment of brain tumors, serving a theranostic purpose as both an MRI-based contrast agent and a radiosensitizer.

Novel risk scores for survival and intracranial failure in patients treated with radiosurgery alone to melanoma brain metastases

Purpose

Stereotactic radiosurgery (SRS) alone is an increasingly common treatment strategy for brain metastases. However, existing prognostic tools for overall survival (OS) were developed using cohorts of patients treated predominantly with approaches other than SRS alone. Therefore, we devised novel risk scores for OS and distant brain failure (DF) for melanoma brain metastases (MBM) treated with SRS alone.

Methods and materials

We retrospectively reviewed 86 patients treated with SRS alone for MBM from 2009-2014. OS and DF were estimated using the Kaplan-Meier method. Cox proportional hazards modeling identified clinical risk factors. Risk scores were created based on weighted regression coefficients. OS scores range from 0-10 (0 representing best OS), and DF risk scores range from 0-5 (0 representing lowest risk of DF). Predictive power was evaluated using c-index statistics. Bootstrapping with 200 resamples tested model stability.

Results

The median OS was 8.1 months from SRS, and 54 (70.1 %) patients had DF at a median of 3.3 months. Risk scores for OS were predicated on performance status, extracranial disease (ED) status, number of lesions, and gender. Median OS for the low-risk group (0-3 points) was not reached. For the moderate-risk (4-6 points) and high-risk (6.5-10) groups, median OS was 7.6 months and 2.4 months, respectively (p < .0001). Scores for DF were predicated on performance status, ED status, and number of lesions. Median time to DF for the low-risk group (0 points) was not reached. For the moderate-risk (1-2 points) and high-risk (3-5 points) groups, time to DF was 4.8 and 2.0 months, respectively (p < .0001). The novel scores were more predictive (c-index = 0.72) than melanoma-specific graded prognostic assessment or RTOG recursive partitioning analysis tools (c-index = 0.66 and 0.57, respectively).

Conclusions

We devised novel risk scores for MBM treated with SRS alone. These scores have implications for prognosis and treatment strategy selection (SRS versus whole-brain radiotherapy).

Circulating Tumor Cells, DNA, and mRNA: Potential for Clinical Utility in Patients With Melanoma

: Circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), and messenger RNA (mRNA), collectively termed circulating tumor products (CTPs), represent areas of immense interest from scientists' and clinicians' perspectives. In melanoma, CTP analysis may have clinical utility in many areas, from screening and diagnosis to clinical decision-making aids, as surveillance biomarkers or sources of real-time genetic or molecular characterization. In addition, CTP analysis can be useful in the discovery of new biomarkers, patterns of treatment resistance, and mechanisms of metastasis development. Here, we compare and contrast CTCs, ctDNA, and mRNA, review the extent of translational evidence to date, and discuss how future studies involving both scientists and clinicians can help to further develop this tool for the benefit of melanoma patients.

IMPLICATIONS FOR PRACTICE

Scientific advancement has enabled the rapid development of tools to analyze circulating tumor cells, tumor DNA, and messenger RNA, collectively termed circulating tumor products (CTPs). A variety of techniques have emerged to detect and characterize melanoma CTPs; however, only a fraction has been applied to human subjects. This review summarizes the available human data that investigate clinical utility of CTP in cancer screening, melanoma diagnosis, prognosis, prediction, and genetic or molecular characterization. It provides a rationale for how CTPs may be useful for future research and discusses how clinicians can be involved in developing this exciting new technology.

Higher dose rate Gamma Knife radiosurgery may provide earlier and longer-lasting pain relief for patients with trigeminal neuralgia

OBJECT

Gamma Knife radiosurgery (GKRS) utilizes cobalt-60 as its radiation source, and thus dose rate varies as the fixed source decays over its half-life of approximately 5.26 years. This natural decay results in increasing treatment times when delivering the same cumulative dose. It is also possible, however, that the biological effective dose may change based on this dose rate even if the total dose is kept constant. Because patients are generally treated in a uniform manner, radiosurgery for trigeminal neuralgia (TN) represents a clinical model whereby biological efficacy can be tested. The authors hypothesized that higher dose rates would result in earlier and more complete pain relief but only if measured with a sensitive pain assessment tool.

METHODS

One hundred thirty-three patients were treated with the Gamma Knife Model 4C unit at a single center by a single neurosurgeon during a single cobalt life cycle from January 2006 to May 2012. All patients were treated with 80 Gy with a single 4-mm isocenter without blocking. Using an output factor of 0.87, dose rates ranged from 1.28 to 2.95 Gy/min. The Brief Pain Inventory (BPI)-Facial was administered before the procedure and at the first follow-up office visit 1 month from the procedure (mean 1.3 months). Phone calls were made to evaluate patients after their procedures as part of a retrospective study. Univariate and multivariate linear regression was performed on several independent variables, including sex, age in deciles, diagnosis, follow-up duration, prior surgery, and dose rate.

RESULTS

In the short-term analysis (mean 1.3 months), patients’ self-reported pain intensity at its worst was significantly correlated with dose rate on multivariate analysis (p = 0.028). Similarly, patients’ self-reported interference with activities of daily living was closely correlated with dose rate on multivariate analysis (p = 0.067). A 1 Gy/min decrease in dose rate resulted in a 17% decrease in pain intensity at its worst and a 22% decrease in pain interference with activities of daily living. In longer-term follow-up (mean 1.9 years), GKRS with higher dose rates (> 2.0 Gy/min; p = 0.007) and older age in deciles (p = 0.012) were associated with a lower likelihood of recurrence of pain.

DISCUSSION

Prior studies investigating the role of dose rate in Gamma Knife radiosurgical ablation for TN have not used validated outcome tools to measure pain preoperatively. Consequently, differences in pain outcomes have been difficult to measure. By administering pain scales both preoperatively as well as postoperatively, the authors have identified statistically significant differences in pain intensity and pain interference with activities of daily living when comparing higher versus lower dose rates. Radiosurgery with a higher dose rate results in more pain relief at the early follow-up evaluation, and it may result in a lower recurrence rate at later follow-up.

Additional data in the debate on stage I non-small cell lung cancer: surgery versus stereotactic ablative radiotherapy

Lobectomy has been the standard of care for patients with early stage non-small cell lung cancer (NSCLC), resulting in nearly universal local control and excellent overall survival. However, up to one-quarter of early stage patients are unable to undergo or refuse definitive resection. With the increasing adoption of stereotactic ablative radiotherapy (SABR) over conventionally fractionated radiotherapy among medical inoperable patients, tumor control and overall survival rates in this population have significantly improved. Trials demonstrating excellent outcomes among both medically inoperable and medical operable patients with stage I NSCLC have spurred interest in comparisons between surgery and SABR. The recent publication of the randomized STARS and ROSEL trials demonstrated fewer toxicities and an improvement in overall survival among patients treated with SABR compared with surgery. Based on these trials and retrospective comparisons between the modalities, definitive SABR now more firmly appears to be a viable first-line option for treating patients with operable stage I NSCLC.

A multifunctional nanoplatform for imaging, radiotherapy, and the prediction of therapeutic response

Gold nanoparticles have garnered interest as both radiosensitzers and computed tomography (CT) contrast agents. However, the extremely high concentrations of gold required to generate CT contrast is far beyond that needed for meaningful radiosensitization, which limits their use as combined therapeutic-diagnostic (theranostic) agents. To establish a theranostic nanoplatform with well-aligned radiotherapeutic and diagnostic properties for better integration into standard radiation therapy practice, a gold- and superparamagnetic iron oxide nanoparticle (SPION)-loaded micelle (GSM) is developed. Intravenous injection of GSMs into tumor-bearing mice led to selective tumoral accumulation, enabling magnetic resonance (MR) imaging of tumor margins. Subsequent irradiation leads to a 90-day survival of 71% in GSM-treated mice, compared with 25% for irradiation-only mice. Furthermore, measurements of the GSM-enhanced MR contrast are highly predictive of tumor response. Therefore, GSMs may not only guide and enhance the efficacy of radiation therapy, but may allow patients to be managed more effectively.

Stereotactic radiosurgery to the resection bed for intracranial metastases and risk of leptomeningeal carcinomatosis

OBJECT

Following resection of a brain metastasis, stereotactic radiosurgery (SRS) to the cavity is an emerging alternative to postoperative whole-brain radiation therapy (WBRT). This approach attempts to achieve local control without the neurocognitive risks associated with WBRT. The authors aimed to report the outcomes of a large patient cohort treated with this strategy.

METHODS

A retrospective review identified 91 patients without a history of WBRT who received Gamma Knife (GK) SRS to 96 metastasis resection cavities between 2007 and 2013. Patterns of intracranial control were examined in the 86 cases with post-GK imaging. Survival, local failure, and distant failure were estimated by the Kaplan-Meier method. Prognostic factors were tested by univariate (log-rank test) and multivariate (Cox proportional hazards model) analyses.

RESULTS

Common primary tumors were non-small cell lung (43%), melanoma (14%), and breast (13%). The cases were predominantly recursive partitioning analysis Class I (25%) or II (70%). Median preoperative metastasis diameter was 2.8 cm, and 82% of patients underwent gross-total resection. A median dose of 16 Gy was delivered to the 50% isodose line, encompassing a median treatment volume of 9.2 cm(3). Synchronous intact metastases were treated in addition to the resection bed in 43% of cases. Patients survived a median of 22.3 months from the time of GK. Local failure developed in 16 cavities, for a crude rate of 18% and 1-year actuarial local control of 81%. Preoperative metastasis diameter ≥ 3 cm and residual or recurrent tumor at the time of GK were associated with local failure (p = 0.04 and 0.008, respectively). Distant intracranial failure occurred in 55 cases (64%) at a median of 7.3 months from GK. Salvage therapies included WBRT and additional SRS in 33% and 31% of patients, respectively. Leptomeningeal carcinomatosis developed in 12 cases (14%) and was associated with breast histology and infratentorial cavities (p = 0.024 and 0.012, respectively).

CONCLUSIONS

This study bolsters the existing evidence for SRS to the resection bed. Local control rates are high, but patients with larger preoperative metastases or residual/recurrent tumor at the time of SRS are more likely to fail at the cavity. While most patients develop distant intracranial failure, an SRS approach spared or delayed WBRT in the majority of cases. The risk of leptomeningeal carcinomatosis does not appear to be elevated with this strategy.

Replication Stress, Defective S-phase Checkpoint and Increased Death in Plk2-Deficient Human Cancer Cells

We previously reported that the Polo-like Kinase 2 gene (Plk2/Snk) is a direct target for transcriptional regulation by p53 and that silencing Plk2 sensitizes cancer cells to Taxol-induced apoptosis. Our goals have been to better understand why Plk2 is regulated by p53 and how Plk2 signals protection from cell death through checkpoint activation. We found that following knock-down of Plk2 in wild-type p53 expressing H460 human non-small cell lung cancer cells there was a significant increase in cell death observed in aphidicolin-treated cells and a further increase after release from aphidicolin-block. The highest levels of cell death were observed when Plk2-deficient cells were released from both aphidicolin and etoposide treatment. These results suggested that a defective S-phase checkpoint may contribute to enhanced sensitivity of Plk2-deficient cells to replication stress. Consistent with this hypothesis, we observed higher levels of Serine 139 H2AX phosphorylation in Plk2-deficient as compared to control cells before and after aphidicolin treatment indicating that there is more DNA damage when Plk2 is depleted. We also observed higher levels of Chk1 protein in Plk2-deficient cells that were associated with reduced levels of Serine 317-phosphorylated Chk1. In aphidicolin-treated cells, there were lower levels of Serine 317-phosphorylated Chk1 when Plk2 was knocked-down. Plk2 was demonstrated to interact with Chk2, Chk1, Serine 317-phosphorylated Chk1 and p53. Thus, increased cell death observed after aphidicolin treatment and release in Plk2-deficient cells may result from both higher levels of replication stress-induced DNA damage and a dysfunctional S-phase checkpoint.

Tracking viable circulating tumor cells (CTCs) in the peripheral blood of non-small cell lung cancer (NSCLC) patients undergoing definitive radiation therapy: pilot study results

BACKGROUND

Assays identifying circulating tumor cells (CTCs) allow noninvasive and sequential monitoring of the status of primary or metastatic tumors, potentially yielding clinically useful information. However, to the authors' knowledge, the effect of radiation therapy (RT) on CTCs in patients with non-small cell lung cancer (NSCLC) has not been previously explored.

METHODS

This report describes results from a pilot study of 30 patients with NSCLC who received RT. Peripheral blood samples obtained from these patients were assayed for CTCs using an assay that identified live cells using an adenoviral probe that detected the elevated telomerase activity present in almost all cancer cells, but not in normal cells, and the validity of the assay was confirmed with secondary tumor-specific markers. Patients were assayed before initiation of RT (pre-RT), during the RT course, and/or after the completion of RT (post-RT).

RESULTS

The assay successfully detected CTCs in the majority of patients, including 65% of patients before the start of RT, and in patients with both epidermal growth factor receptor wild-type and mutation-positive tumors. The median CTC counts in patients before RT was 9.1 CTCs per mL (range, undetectable to 571 CTCs per mL) and was significantly higher than the average post-RT count of 0.6 CTCs per mL (range, undetectable to 1.8 CTCs per mL; P<.001). Sequential CTC counts were available in a subset of patients and demonstrated decreases after RT, except for 1 patient who subsequently developed distant failure.

CONCLUSIONS

The current pilot data suggest that CTC counts appear to reflect response to RT in patients with localized NSCLC. On the basis of these promising results, the authors have launched a more comprehensive and detailed clinical trial.

Application of a telomerase-based circulating tumor cell (CTC) assay in bladder cancer patients receiving postoperative radiation therapy: a case study

BACKGROUND

Muscle invasive bladder carcinoma is an often lethal disease that requires aggressive treatment. Improved assays would contribute to better risk prediction and clinical management of this disease. A telomerase-based assay to detect circulating tumor cells (CTCs) may usefully fulfill this role.

METHODS

Two patients (C1 and C2) were enrolled onto an IRB-approved bladder biomarker study before initiating post-operative radiation therapy (RT) for muscle invasive bladder carcinoma. Blood samples were taken at predefined intervals: before, during, and after RT and then retrospectively correlated with imaging studies and disease course.

RESULTS

C1 began RT for positive resection margins on surgical pathology, at which time CTCs were undetectable and pelvic imaging demonstrated no evidence of disease. However, following the completion of treatment, the patient's CTC count was found to have increased to 202 CTCs/mL, and MRI demonstrated new abdominal and pelvic masses consistent with progressive disease. C1 ultimately died of disease with distant and local failure. Conversely, C2 was found to have 632 CTCs/mL before the initiation of RT for positive surgical margins, although imaging demonstrated no visible masses. At the conclusion of RT, repeat imaging showed changes that were indeterminate for either tumor recurrence or post-radiation effects. However, the patient's CTC count had dropped to 184 CTCs/mL. Furthermore, a second follow-up assay performed 6 months later revealed no detectable CTCs and repeat imaging showed complete resolution of worrisome imaging changes, thus excluding tumor progression.

CONCLUSIONS

To our knowledge this is the first report of a telomerase-based assay to identify CTCs in bladder cancer patients. Further studies are required to fully determine the ultimate clinical utility of this assay. However, the two patient vignettes described here illustrate how serial CTC assays may track the disease course and inform the management of bladder cancer patients undergoing adjuvant RT and potentially chemotherapy.

Detection of brain tumor cells in the peripheral blood by a telomerase promoter-based assay

Blood tests to detect circulating tumor cells (CTC) offer great potential to monitor disease status, gauge prognosis, and guide treatment decisions for patients with cancer. For patients with brain tumors, such as aggressive glioblastoma multiforme, CTC assays are needed that do not rely on expression of cancer cell surface biomarkers like epithelial cell adhesion molecules that brain tumors tend to lack. Here, we describe a strategy to detect CTC based on telomerase activity, which is elevated in nearly all tumor cells but not normal cells. This strategy uses an adenoviral detection system that is shown to successfully detect CTC in patients with brain tumors. Clinical data suggest that this assay might assist interpretation of treatment response in patients receiving radiotherapy, for example, to differentiate pseudoprogression from true tumor progression. These results support further development of this assay as a generalized method to detect CTC in patients with cancer.

Gamma Knife radiosurgery to four or more brain metastases in patients without prior intracranial radiation or surgery

Data on stereotactic radiosurgery (SRS) for four or more metastases are limited. Existing studies are confounded by significant proportions of patients receiving prior whole-brain radiation therapy (WBRT) or concurrent WBRT with SRS. Furthermore, published results disagree about the impact of tumor volume on overall survival. A retrospective review identified 38 patients without prior intracranial radiation or surgery who received Gamma Knife (GK) as sole treatment to ≥4 brain metastases in a single session. Twenty-eight cases with follow-up imaging were analyzed for intracranial progression. Prognostic factors were examined by univariate (log-rank test) and multivariate (Cox proportional hazards model) analyses. Common primary tumors were non-small cell lung (45%), melanoma (37%), and breast (8%). Cases were recursive partitioning analysis class II (94%) or III (6%). Patients harbored a median five tumors (range 4–12) with median total tumor volume of 1.2 cc. A median dose of 21 Gy was prescribed to the 50% isodose line. Patients survived a median 6.7 months from GK. Local treatment failure occurred in one case (4%) and distant failure in 22 (79%). On multivariate analysis, total tumor volume ≥3 cc was significantly associated with distant failure and worsened overall survival (P = 0.042 and 0.040). Fourteen patients (37%) underwent salvage WBRT at a median 10.3 months from GK and seven patients received repeat GK. GK as sole initial treatment for four or more simultaneous metastases spares some patients WBRT and delays it for others. Increased total tumor volume (≥3 cc) is significantly associated with worsened overall survival.

Distinctive effects of the cellular inhibitor of apoptosis protein c-IAP2 through stabilization by XIAP in glioblastoma multiforme cells

Inhibitor of apoptosis proteins (IAPs) are extensively involved in NFκB signaling pathways. Regulation of c-IAP2 turnover by other proteins was investigated in glioblastoma multiforme (GBM) cells in the present study. When overexpressed, X-linked IAP (XIAP) enhanced expression of ectopic c-IAP2, but not c-IAP1, and endogenous c-IAP2 levels were reduced once XIAP expression was silenced. TNFα stimulation substantially increased c-IAP2 expression, and this upregulation was impaired by suppression of XIAP. Similarly, when XIAP was limiting due to severe hypoxic conditions, c-IAP2 levels were downregulated. These data together indicate that XIAP is an important regulator responsible for stabilization of c-IAP2 levels under different conditions. Protein interactions occur through binding of BIR2 and BIR3 domains of c-IAP2 with the RING finger of XIAP. XIAP inhibition of c-IAP2 auto-degradation was dependent on this physical interaction, and it was independent of XIAP E3 ligase activity. Global c-IAP2 ubiquitination was not affected by XIAP, although c-IAP2 levels were significantly increased. A CARD-RING-containing fragment of c-IAP2 was found to target XIAP for proteasome-independent degradation, but it was unable to sensitize GBM cells to chemo-reagents. The XIAP-stabilized c-IAP2 was found to enhance IκB-α phosphorylation on serines 32 and 36, and to antagonize XIAP-induced increase in mature Smac and Bcl10. Taken together, our data identify a distinctive role of c-IAP2 as stabilizer of XIAP, which is likely involved in regulation of NFκB activation and apoptosis in GBM cells.

Enhancing the efficacy of drug-loaded nanocarriers against brain tumors by targeted radiation therapy

Glioblastoma multiforme (GBM) is a common, usually lethal disease with a median survival of only ~15 months. It has proven resistant in clinical trials to chemotherapeutic agents such as paclitaxel that are highly effective in vitro, presumably because of impaired drug delivery across the tumor's blood-brain barrier (BBB). In an effort to increase paclitaxel delivery across the tumor BBB, we linked the drug to a novel filomicelle nanocarrier made with biodegradable poly(ethylene-glycol)-block-poly(ε-caprolactone-r-D,L-lactide) and used precisely collimated radiation therapy (RT) to disrupt the tumor BBB's permeability in an orthotopic mouse model of GBM. Using a non-invasive bioluminescent imaging technique to assess tumor burden and response to therapy in our model, we demonstrated that the drug-loaded nanocarrier (DLN) alone was ineffective against stereotactically implanted intracranial tumors yet was highly effective against GBM cells in culture and in tumors implanted into the flanks of mice. When targeted cranial RT was used to modulate the tumor BBB, the paclitaxel-loaded nanocarriers became effective against the intracranial tumors. Focused cranial RT improved DLN delivery into the intracranial tumors, significantly improving therapeutic outcomes. Tumor growth was delayed or halted, and survival was extended by &gt;50% (p<0.05) compared to the results obtained with either RT or the DLN alone. Combinations of RT and chemotherapeutic agents linked to nanocarriers would appear to be an area for future investigations that could enhance outcomes in the treatment of human GBM.

Selective targeting of brain tumors with gold nanoparticle-induced radiosensitization

Successful treatment of brain tumors such as glioblastoma multiforme (GBM) is limited in large part by the cumulative dose of Radiation Therapy (RT) that can be safely given and the blood-brain barrier (BBB), which limits the delivery of systemic anticancer agents into tumor tissue. Consequently, the overall prognosis remains grim. Herein, we report our pilot studies in cell culture experiments and in an animal model of GBM in which RT is complemented by PEGylated-gold nanoparticles (GNPs). GNPs significantly increased cellular DNA damage inflicted by ionizing radiation in human GBM-derived cell lines and resulted in reduced clonogenic survival (with dose-enhancement ratio of ∼1.3). Intriguingly, combined GNP and RT also resulted in markedly increased DNA damage to brain blood vessels. Follow-up in vitro experiments confirmed that the combination of GNP and RT resulted in considerably increased DNA damage in brain-derived endothelial cells. Finally, the combination of GNP and RT increased survival of mice with orthotopic GBM tumors. Prior treatment of mice with brain tumors resulted in increased extravasation and in-tumor deposition of GNP, suggesting that RT-induced BBB disruption can be leveraged to improve the tumor-tissue targeting of GNP and thus further optimize the radiosensitization of brain tumors by GNP. These exciting results together suggest that GNP may be usefully integrated into the RT treatment of brain tumors, with potential benefits resulting from increased tumor cell radiosensitization to preferential targeting of tumor-associated vasculature.

Stereotactic intracranial implantation and in vivo bioluminescent imaging of tumor xenografts in a mouse model system of glioblastoma multiforme

Glioblastoma multiforme (GBM) is a high-grade primary brain cancer with a median survival of only 14.6 months in humans despite standard tri-modality treatment consisting of surgical resection, post-operative radiation therapy and temozolomide chemotherapy. New therapeutic approaches are clearly needed to improve patient survival and quality of life. The development of more effective treatment strategies would be aided by animal models of GBM that recapitulate human disease yet allow serial imaging to monitor tumor growth and treatment response. In this paper, we describe our technique for the precise stereotactic implantation of bio-imageable GBM cancer cells into the brains of nude mice resulting in tumor xenografts that recapitulate key clinical features of GBM. This method yields tumors that are reproducible and are located in precise anatomic locations while allowing in vivo bioluminescent imaging to serially monitor intracranial xenograft growth and response to treatments. This method is also well-tolerated by the animals with low perioperative morbidity and mortality.

Dissecting the complex regulation of Mad4 in glioblastoma multiforme cells

Among proteins in the c-Myc/Max/Mad/Sin3 regulatory complex, Mad4 and Sin3B are routinely detected in human glioblastoma multiforme (GBM) cell lines. In response to gamma radiation, the expression of Sin3B and Mad4 in GBM cells was upregulated in parallel over time, suggesting that Sin3B may play a role in the regulation of Mad4 stability. In agreement with this hypothesis, exogenously expressed Sin3B significantly stabilized co-transfected Mad4 and, to a lesser extent, endogenous Mad4. In addition, siRNA silencing of Sin3B induced an increase in the expression of c-Myc and Sin3A, which contributed to increased expression of Mad4. Simultaneous silencing of Sin3B, Sin3A and c-Myc decreased Mad4 stability to a greater extent than silencing of Sin3B alone. Although Mad1 was reported to be a target of c-IAP1 E3 ligase activity for degradation, the E3 ligase activity of c-IAP1 was not required for downregulation of Mad4 expression. The association of c-IAP1 with Sin3B or Mad4 suggested that Sin3B might interfere with the binding of c-IAP1 to Mad4; however, overexpression of Sin3B did not affect the interaction between Mad4 and c-IAP1. Instead, direct binding of Sin3B to c-IAP1 may protect Mad4 from degradation by c-IAP1, leading to enhanced stability of Mad4. Exogenous expression of Sin3B also inhibited c-IAP1-mediated degradation of Mad1, TRAF2, c-IAP2 and ASK1, known targets of c-IAP1 E3 ligase activity. These results indicate that Sin3B, together with other c-Myc regulatory members, maintain the steady-state level of Mad4, in part through inhibition of c-IAP1-mediated degradation of Mad4.

Modulation of the anti-cancer efficacy of microtubule-targeting agents by cellular growth conditions

Mitotic spindle-disrupting agents target and disrupt microtubule dynamics. These agents include clinically important chemotherapies, including taxanes (paclitaxel (Taxol), docetaxel (Taxotere)) and vinca alkaloids (vincristine (Oncovin), vinblastine). Taxanes are a standard component of treatment for many malignancies, often in conjunction with other cytotoxic agents. However, the optimal sequencing of these treatments and whether efficacy may be influenced by in vitro cellular growth conditions remain incompletely investigated. Yet such preclinical investigations may guide clinical decision making. We therefore studied the effect of cell density on rapid killing by paclitaxel and vincristine. Breast, ovarian and prostate cancer cells were sensitive to rapid killing by either agent when grown at low density, but were markedly resistant when grown at high density, i.e. nearly confluent. The resistance of densely growing cells to rapid killing by these drugs translated to increased clonogenic survival. Pretreatment of densely growing cancer cells with cisplatin followed by paclitaxel, partially reversed the treatment resistance. Gene ontology associations from microarray analyses of cells grown at low and high density, suggested roles for membrane signal transduction and adhesion, but potentially also DNA damage repair and metabolism. Taken together, the treatment resistance at higher cell density may be associated with a lower proportion of active cycling in cells growing at high density as well as transduction of survival signals induced by increased cell-cell adhesion. Collectively these findings suggest mechanisms by which growth conditions may contribute to resistance to rapid killing by microtubule-disrupting drugs.

Modulation of CCAAT/enhancer binding protein homologous protein (CHOP)-dependent DR5 expression by nelfinavir sensitizes glioblastoma multiforme cells to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)

Human glioblastoma multiforme cells demonstrate varying levels of sensitivity to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis. Endoplasmic reticulum (ER) stress has been shown to trigger cell death through apoptosis. We therefore pursued a strategy of integrating clinically relevant investigational agents that cooperate mechanistically through the regulation of ER stress and apoptosis pathways. Nelfinavir belongs to the protease inhibitor class of drugs currently used to treat patients with HIV and is in clinical trials as an anti-tumor agent. We found that Nelfinavir treatment led to ER stress-induced up-regulation of the DR5 receptor. This transactivation was mediated by the transcription factor CCAAT/enhancer binding protein homologous protein (CHOP). We also determined that ER stress-induced ATF4 up-regulation was responsible for modulation of CHOP. In contrast, DR4 receptor expression was unchanged by Nelfinavir treatment. Combining Nelfinavir with TRAIL led to a significantly enhanced level of apoptosis that was abrogated by siRNA silencing of DR5. We provide evidence that Nelfinavir-induced ER stress modulates DR5 expression in human glioblastoma multiforme cells and can enhance TRAIL efficacy. These studies provide a potential mechanistic rationale for the use of the Food and Drug Administration-approved agent Nelfinavir in combination with DR5 agonists to induce apoptosis in human malignancies.

Overcoming hypoxia-induced apoptotic resistance through combinatorial inhibition of GSK-3β and CDK1

Tumor hypoxia is an inherent impediment to cancer treatment that is both clinically significant and problematic. In this study, we conducted a cell-based screen to identify small molecules that could reverse the apoptotic resistance of hypoxic cancer cells. Among the compounds, we identified were a structurally related group that sensitized hypoxic cancer cells to apoptosis by inhibiting the kinases GSK-3β and cyclin-dependent kinase (CDK) 1. Combinatorial inhibition of these proteins in hypoxic cancer cells and tumors increased levels of c-Myc and decreased expression of c-IAP2 and the central hypoxia response regulator hypoxia-inducible factor (HIF) 1α. In mice, these compounds augmented the hypoxic tumor cell death induced by cytotoxic chemotherapy, blocking angiogenesis and tumor growth. Taken together, our findings suggest that combinatorial inhibition of GSK-3β and CDK1 augment the apoptotic sensitivity of hypoxic tumors, and they offer preclinical validation of a novel and readily translatable strategy to improve cancer therapy.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and paclitaxel have cooperative in vivo effects against glioblastoma multiforme cells

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in conjunction with microtubule-targeting agents may be a promising novel anticancer treatment strategy. In vitro studies have suggested that relatively low concentrations of TRAIL enhance the lethality of paclitaxel (Taxol) against human cancer cells. The increased efficacy may be due to the triggering of caspase activation, resulting in mitotic checkpoint abrogation and catastrophe. We show here that wild-type p53 protects cells from caspase-dependent death induced by this therapeutic combination in vitro. We have now also developed an imaging-based model system to test the in vivo efficacy of combined TRAIL and Taxol, in which tumor growth and treatment response can be monitored noninvasively and in real-time. We further utilize bioluminescence, F18-fluorodeoxyglucose-positron emission tomography, and microscale computed tomography imaging to confirm the effects of combined treatment on tumors. These studies together provide the first in vivo confirmation that combined TRAIL plus paclitaxel results in better tumor control compared with either TRAIL or paclitaxel alone, and with no discernable increased normal tissue toxicity in the mouse. Interestingly, the in vivo antitumor response elicited by combined treatment was not affected by the p53 status of the tumor cells. These preclinical observations together suggest the therapeutic potential of combining TRAIL plus paclitaxel in cancer treatment, and support further preclinical and future clinical testing.

Role of PI3K/Akt signaling in TRAIL- and radiation-induced gastrointestinal apoptosis

Activation of the PI3K/Akt pathway is associated with tumorigenesis and resistance to apoptosis and ionizing radiation (IR). We sought to characterize the effects of physiologic and genetic manipulation of Akt signaling on IR-induced gastrointestinal (GI) apoptosis in mice. PI3K/Akt signaling is stimulated by insulin. We evaluated the time course of Akt stimulation by insulin and found it overlapped with protection from apoptosis induced by TRAIL (TNFalpha Related Apoptosis Inducing Ligand) in cell lines. Mice were treated with insulin and glucose and the kinetics of in vivo Akt stimulation were determined by phospho-Akt (S473) (P-Akt) immunofluorescence in the gut. Irradiation of mice by five Gy at 30 minutes after insulin/glucose administration induced apoptosis in the crypts of the ileum and colon after six hours, but induced little apoptosis in the liver or esophagus. Pre-treatment with insulin and glucose did not significantly alter levels of IR-induced apoptosis in the gut. IR alone led to sustained increases in P-Akt in the gut at six hours, a protective response that may have precluded additional protection from insulin/glucose. In Akt1-/- mice, there was significantly more apoptosis in ileum crypts of irradiated mice compared to Akt1+/+ mice, suggesting a role for the pathway in the GI tract in response to IR. Taken together, modulation of the PI3K/Akt pathway may sensitize or protect against cancer therapies in both tumor and normal tissues.

SRC directly phosphorylates Bif-1 and prevents its interaction with Bax and the initiation of anoikis

Bif-1 interacts with Bax and enhances its conformational rearrangement, resulting in apoptosis. However, the molecular mechanism governing the interaction between Bif-1 and Bax is poorly defined. Here we provide evidence that Bif-1 is phosphorylated, an event that can be repressed by apoptotic stimuli. The protein kinase c-Src binds to and directly phosphorylates Bif-1 on tyrosine 80. Moreover, Src phosphorylation of Bif-1 suppresses the interaction between Bif-1 and Bax, resulting in the inhibition of Bax activation during anoikis. Together, these results suggest that phosphorylation of Bif-1 impairs its binding to Bax and represses apoptosis, providing another mechanism by which Src oncogenic signaling can prevent cell death.

Cell cycle dependent and schedule-dependent antitumor effects of sorafenib combined with radiation

The antineoplastic drug sorafenib (BAY 43-9006) is a multikinase inhibitor that targets the serine-threonine kinase B-Raf as well as several tyrosine kinases. Given the numerous molecular targets of sorafenib, there are several potential anticancer mechanisms of action, including induction of apoptosis, cytostasis, and antiangiogenesis. We observed that sorafenib has broad activity in viability assays in several human tumor cell lines but selectively induces apoptosis in only some lines. Sorafenib was found to decrease Mcl-1 levels in most cell lines tested, but this decrease did not correlate with apoptotic sensitivity. Sorafenib slows cell cycle progression and prevents irradiated cells from reaching and accumulating at G2-M. In synchronized cells, sorafenib causes a reversible G1 delay, which is associated with decreased levels of cyclin D1, Rb, and phosphorylation of Rb. Although sorafenib does not affect intrinsic radiosensitivity using in vitro colony formation assays, it significantly reduces colony size. In HCT116 xenograft tumor growth delay experiments in mice, sorafenib alters radiation response in a schedule-dependent manner. Radiation treatment followed sequentially by sorafenib was found to be associated with the greatest tumor growth delay. This study establishes a foundation for clinical testing of sequential fractionated radiation followed by sorafenib in gastrointestinal and other malignancies.

Multimodality optical imaging and 18F-FDG uptake in wild-type p53-containing and p53-null human colon tumor xenografts

During tumor development a switch to glycolytic metabolism known as the Warburg effect may provide cancer cells with a survival advantage and may also provide a therapeutic opportunity. A number of signals contribute to aerobic glycolysis including those mediated by HIF-1, c-Myc, Akt and Hexokinase. Recent studies have implicated the p53 tumor suppressor as a negative regulator of this switch. Using inducible p53 gene silencing in bioluminescent tumor xenografts we initially observed qualitatively similar levels of FDG uptake by PET small animal imaging in wild-type p53-expressing tumor xenografts and p53 gene-silenced xenografts. We further evaluated glucose uptake using FDG-PET/CT fusion imaging of green and red fluorescently-labeled wild-type and p53-null human colon tumor xenografts. Our results demonstrate that the wild-type p53-expressing tumor xenografts exhibit high levels of glucose uptake, similar to those observed in p53-null tumor xenografts, by quantitative PET imaging indicative of the glycolytic switch. Thus p53 function is not sufficient to suppress glucose uptake in cells and tumors that could theoretically support aerobic glycolysis.