Neoadjuvant Arterial Embolization of Spine Metastases Associated With Improved Local Control in Patients Receiving Surgical Decompression and Stereotactic Body Radiotherapy

BACKGROUND

Spine metastases often cause significant pain, instability, and/or neurological morbidity. Local control (LC) of spine metastases has been augmented with advances in systemic therapies, radiation, and surgical technique. Prior reports suggest an association between preoperative arterial embolization and improved LC and palliative pain control.

OBJECTIVE

To further elucidate the role of neoadjuvant embolization on LC of spine metastases and the potential for improved pain control in patients receiving surgery and stereotactic body radiotherapy (SBRT).

METHOD

A retrospective single-center review between 2012 and 2020 identified 117 patients with spinal metastases from various solid tumor malignancies managed with surgery and adjuvant SBRT with or without preoperative spinal arterial embolization. Demographic information, radiographic studies, treatment characteristics, Karnofsky Performance Score, Defensive Veterans Pain Rating Scale, and mean daily doses of analgesic medications were reviewed. LC was assessed using magnetic resonance imaging obtained at a median 3-month interval and defined as progression at the surgically treated vertebral level.

RESULTS

Of 117 patients, 47 (40.2%) underwent preoperative embolization, followed by surgery and SBRT and 70 (59.8%) underwent surgery and SBRT alone. Within the embolization cohort, the median LC was 14.2 months compared with 6.3 months among the nonembolization cohort ( P = .0434). Receiver operating characteristic analysis suggests ≥82.5% embolization predicted significantly improved LC (area under the curve = 0.808; P < .0001). Defensive Veterans Pain Rating Scale mean and maximum scores significantly decreased immediately after embolization ( P < .001).

CONCLUSION

Preoperative embolization was associated with improved LC and pain control suggesting a novel role for its use. Additional prospective study is warranted.

Feasibility, safety, and efficacy of circumferential spine stereotactic body radiotherapy

Background

With advances in systemic therapy translating to improved survival in metastatic malignancies, spine metastases have become an increasingly common source of morbidity. Achieving durable local control (LC) for patients with circumferential epidural disease can be particularly challenging. Circumferential stereotactic body radiotherapy (SBRT) may offer improved LC for circumferential vertebral and/or epidural metastatic spinal disease, but prospective (and retrospective) data are extremely limited. We sought to evaluate the feasibility, toxicity, and cancer control outcomes with this novel approach to circumferential spinal disease.

Methods

We retrospectively identified all circumferential SBRT courses delivered between 2013 and 2019 at a tertiary care institution for post-operative or intact spine metastases. Radiotherapy was delivered to 14-27.5 Gy in one to five fractions. Feasibility was assessed by determining the proportion of plans for which ≥95% planning target volume (PTV) was coverable by ≥95% prescription dose. The primary endpoint was 1-year LC. Factors associated with increased likelihood of local failure (LF) were explored. Acute and chronic toxicity were assessed. Detailed dosimetric data were collected.

Results

Fifty-eight patients receiving 64 circumferential SBRT courses were identified (median age 61, KPS ≥70, 57% men). With a median follow-up of 15 months, the 12-month local control was 85% (eight events). Five and three recurrences were in the epidural space and bone, respectively. On multivariate analysis, increased PTV and uncontrolled systemic disease were significantly associated with an increased likelihood of LF; ≥95% PTV was covered by ≥95% prescription dose in 94% of the cases. The rate of new or progressive vertebral compression fracture was 8%. There were no myelitis events or any grade 3+ acute or late toxicities.

Conclusions

For patients with circumferential disease, circumferential spine SBRT is feasible and may offer excellent LC without significant toxicity. A prospective evaluation of this approach is warranted.

RADT-12. PRE- AND POST-OPERATIVE RADIATION TREATMENT PLANNING FOR PATIENTS RECEIVING STEREOTACTIC RADIOSURGERY FOR BRAIN METASTASES: A VOLUMETRIC ANALYSIS

BACKGROUND

Pre-operative stereotactic radiosurgery (SRS) has emerged as a recent treatment option to treat large or symptomatic brain metastases. Compared to post-operative SRS, pre-operative treatment may reduce rates of radiation necrosis (RN) and meningeal disease through treating a smaller treatment volume and by preventing post-operative tumor seeding. We hypothesize that pre-operative radiation volumes will be smaller than post-operative volumes, which in turn may lead to a decreased treatment morbidity.

METHODS

A retrospective analysis was conducted and patients who had surgical resection and post-operative SRS or fractionated stereotactic radiosurgery (FSRT) for a posterior fossa brain metastasis were eligible for inclusion. Both pre-operative and post-operative MRIs were required to allow for accurate radiation target delineation. A pre-operative tumor volume was added for each patient, and the post-operative clinical treatment volume (CTV) used for radiation treatment was included. Pre-operative tumor and post-operative cavity volumes were compared using Wilcoxon signed rank test.

RESULTS

28 patients who received post-operative SRS or FSRT from 1/1/2016-12/31/2020 were included in this analysis. The mean pre-operative tumor volume was 14.9 ccs, and the mean post-operative CTV was 21.0 ccs (p &lt; 0.01). 75% of patients had a smaller initial tumor size compared to the post-operative CTV used for radiation treatment planning. For patients with at least 4 follow up MRIs (n = 8), the size of the post-operative cavity progressively decreased with a mean initial cavity volume of 18.9 ccs and mean follow up volumes of 8.1, 7.1, 6.9, and 6.2 ccs.

CONCLUSIONS

In this study evaluating patients who received post-operative SRS, the pre-operative tumor volume was lower than the post-operative CTV for most patients. Previous studies including PROPS-BM have shown how pre-operative treatment may reduce the risk of RN because smaller radiation volumes are used. Pre-operative radiosurgery for patients with brain metastases requires prospective validation.

Comparing Pre-Operative Versus Post-Operative Single and Multi-Fraction Stereotactic Radiotherapy for Patients with Resectable Brain Metastases

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Pre-operative radiation therapy for brain metastases may reduce meningeal disease.

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Pre-operative radiation therapy for brain metastases may reduce radionecrosis.

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Fractionated radiation therapy for brain metastases may reduce local failure.

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Fractionated pre-operative radiation therapy requires prospective validation.

Background

The standard treatment for patients with large brain metastases and limited intracranial disease is surgical resection and post-operative stereotactic radiosurgery (SRS). However, post-operative SRS still has elevated rates of local failure (LF) and is complicated by radiation necrosis (RN), and meningeal disease (MD). Pre-operative SRS may reduce the risk of RN and MD, while fractionated therapy may improve local control through delivering a higher biological effective dose. We hypothesize that pre-operative fractionated stereotactic radiation therapy (FSRT) will have less toxicity compared to patients who receive post-operative SRS or FSRT.

Methods

A multi-institutional analysis was conducted and included patients who had surgical resection and stereotactic radiation therapy to treat at least one brain metastasis. Pertinent demographic, clinical, radiation, surgical, and follow up data were collected for each patient. The primary outcome was a composite endpoint defined as patients with one of the following adverse events: 1) LF, 2) MD, and/or 3) Grade 2 or higher (symptomatic) RN.

Results

279 patients were eligible for analysis. The median follow-up time was 9 months. 87 % of patients received fractionated treatment. 29 % of patients received pre-operative treatment. The composite endpoint incidences for post-operative SRS (n = 10), post-operative FSRT (n = 189), pre-operative SRS (n = 27), and pre-operative FSRT (n = 53) were 0 %, 17 %, 15 %, and 7.5 %, respectively.

Conclusions

In our study, the composite endpoint of 7.5% for pre-operative FSRT compares favorably to our post-operative FSRT rate of 17%. Pre-operative FSRT was observed to have low rates of LF, MD, and RN. Prospective validation is needed.

Spine Stereotactic Body Radiotherapy to Three or More Contiguous Vertebral Levels

Background

With survival improving in many metastatic malignancies, spine metastases have increasingly become a source of significant morbidity; achieving durable local control (LC) is critical. Stereotactic body radiotherapy (SBRT) may offer improved LC and/or symptom palliation. However, due to setup concerns, SBRT is infrequently offered to patients with ≥3 contiguous involved levels. Because data are limited, we sought to evaluate the feasibility, toxicity, and cancer control outcomes of spine SBRT delivered to ≥3 contiguous levels.

Methods

We retrospectively identified all SBRT courses delivered between 2013 and 2019 at a tertiary care institution for postoperative or intact spine metastases. Radiotherapy was delivered to 14-35 Gy in 1-5 fractions. Patients were stratified by whether they received SBRT to 1-2 or ≥3 contiguous levels. The primary endpoint was 1-year LC and was compared between groups. Factors associated with increased likelihood of local failure (LF) were explored. Acute and chronic toxicity was assessed. In-depth dosimetric data were collected.

Results

Overall, 165 patients with 194 SBRT courses were identified [54% were men, median age was 61 years, 93% had Karnofsky Performance Status (KPS) ≥70, and median follow-up was 15 months]. One hundred thirteen patients (68%) received treatment to 1-2 and 52 to 3-7 (32%) levels. The 1-year LC was 88% (89% for 1-2 levels vs. 84% for ≥3 levels, p = 0.747). On multivariate analysis, uncontrolled systemic disease was associated with inferior LC for patients with ≥3 treated levels. No other demographic, disease, treatment, or dosimetric variables achieved significance. Rates of new/progressive fracture were equivalent (8% vs. 9.5%, p = 0.839). There were no radiation-induced myelopathy or grade 3+ acute or late toxicities in either group. Coverage of ≥95% of the planning target volume with ≥95% prescription dose was similar between groups (96% 1-2 levels vs. 89% ≥3 levels, p = 0.078).

Conclusions

For patients with ≥3 contiguous involved levels, spine SBRT is feasible and may offer excellent LC without significant toxicity. Prospective evaluation is warranted.

Disruption of DNA Repair and Survival Pathways through Heat Shock Protein inhibition by Onalespib to Sensitize Malignant Gliomas to Chemoradiation therapy

PURPOSE

Proficient DNA repair by homologous recombination (HR) facilitates resistance to chemo-radiation in glioma stem cells (GSCs). We evaluated whether compromising HR by targeting HSP90, a molecular chaperone required for the function of key HR proteins, using onalespib, a long-acting, brain-penetrant HSP90 inhibitor, would sensitize high-grade gliomas to chemo-radiation in vitro and in vivo Experimental Design: The ability of onalespib to deplete HR client proteins, impair HR repair capacity, and sensitize GBM to chemo-radiation was evaluated in vitro in GSCs, and in vivo using zebrafish and mouse intracranial glioma xenograft models. The effects of HSP90 inhibition on the transcriptome and cytoplasmic proteins was assessed in GSCs and in ex vivo organotypic human glioma slice cultures.

RESULTS

Treatment with onalespib depleted CHK1 and RAD51, two key proteins of the HR pathway, and attenuated HR repair, sensitizing GSCs to the combination of radiation and temozolomide (TMZ). HSP90 inhibition reprogrammed the transcriptome of GSCs and broadly altered expression of cytoplasmic proteins including known and novel client proteins relevant to GSCs. The combination of onalespib with radiation and TMZ extended survival in a zebra fish and a mouse xenograft model of GBM compared to the standard of care (radiation and TMZ) or onalespib with radiation.

CONCLUSIONS

The results of this study demonstrate that targeting HR by HSP90 inhibition sensitizes GSCs to radiation and chemotherapy and extends survival in zebrafish and mouse intracranial models of GBM. These results provide a preclinical rationale for assessment of HSP90 inhibitors in combination with chemoradiation in GBM patients.

Dose-escalated accelerated hypofractionation for elderly or frail patients with a newly diagnosed glioblastoma

BACKGROUND

The standard of care for elderly glioblastoma patients is 40 Gy in 15 fraction radiotherapy with temozolomide (TMZ). However, this regimen has a lower biologic equivalent dose (BED) compared to the Stupp regimen of 60 Gy in 30 fractions. We hypothesize that accelerated hypofractionated radiation of 52.5 Gy in 15 fractions (BED equivalent to Stupp) will have superior survival compared to 40 Gy in 15 fractions.

METHODS

Elderly patients (≥ 65 years old) who received hypofractionated radiation with TMZ from 2010 to 2020 were included in this analysis. Overall survival (OS) and progression free survival were defined as the time elapsed between surgery/biopsy and death from any cause or progression. Baseline characteristics were compared between patients who received 40 and 52.5 Gy. Univariable and multivariable analyses were performed.

RESULTS

Sixty-six newly diagnosed patients were eligible for analysis. Thirty-nine patients were treated with 40 Gy in 15 fractions while twenty-seven were treated with 52.5 Gy in 15 fractions. Patients had no significant differences in age, sex, methylation status, or performance status. OS was superior in the 52.5 Gy group (14.1 months) when compared to the 40 Gy group (7.9 months, p = 0.011). Isoeffective dosing to 52.5 Gy was shown to be an independent prognostic factor for improved OS on multivariable analysis.

CONCLUSIONS

Isoeffective dosing to 52.5 Gy in 15 fractions was associated with superior OS compared to standard of care 40 Gy in 15 fractions. These hypothesis generating data support accelerated hypofractionation in future prospective trials.

Inhibition of nicotinamide phosphoribosyltransferase, the rate-limiting enzyme of the nicotinamide adenine dinucleotide salvage pathway, to target glioma heterogeneity through mitochondrial oxidative stress

BACKGROUND

Tumor-specific metabolic processes essential for cell survival are promising targets to potentially circumvent intratumoral heterogeneity, a major resistance factor in gliomas. Tumor cells preferentially using nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in the salvage pathway for synthesis of NAD, a critical cofactor for diverse biological processes including cellular redox reactions, energy metabolism and biosynthesis. NAMPT is overexpressed in most malignancies, including gliomas, and can serve as a tumor-specific target.

METHODS

Effects of pharmacological inhibition of NAMPT on cellular oxygen consumption rate, extracellular acidification, mitochondrial respiration, cell proliferation, invasion and survival were assessed through in vitro and ex vivo studies on genetically heterogeneous glioma cell lines, glioma stem-like cells (GSCs) and mouse and human ex vivo organotypic glioma slice culture models.

RESULTS

Pharmacological inhibition of the NAD salvage biosynthesis pathway using a highly specific inhibitor, KPT-9274, resulted in reduction of NAD levels and related downstream metabolites, inhibited proliferation, and induced apoptosis in vitro in cell lines and ex vivo in human glioma tissue. These effects were mediated by mitochondrial dysfunction, DNA damage and increased oxidative stress leading to apoptosis in GSCs independent of genotype, IDH status or MGMT promoter methylation status. Conversely, NAMPT inhibition had minimal in vitro effects on normal human astrocytes (NHA) and no apparent in vivo toxicity in non-tumor-bearing mice.

CONCLUSIONS

Pharmacological NAMPT inhibition by KPT9274 potently targeted genetically heterogeneous gliomas by activating mitochondrial dysfunction. Our preclinical results provide a rationale for targeting the NAMPT-dependent alternative NAD biosynthesis pathway as a novel clinical strategy against gliomas.

Postoperative Stereotactic Body Radiotherapy for Spinal Metastasis and Predictors of Local Control

BACKGROUND

Spine surgery is indicated for select patients with mechanical instability, pain, and/or malignant epidural spinal cord compression, with or without neurological compromise. Stereotactic body radiotherapy (SBRT) is an option for durable local control (LC) for metastatic spine disease.

OBJECTIVE

To determine factors associated with LC and progression-free survival (PFS) for patients receiving postoperative stereotactic spine radiosurgery.

METHODS

We analyzed consecutive patients from 2013 to 2019 treated with surgical intervention followed by SBRT. Surgical interventions included laminectomy and vertebrectomy. SBRT included patients treated with 1 to 5 fractions of radiosurgery. We analyzed LC, PFS, overall survival (OS), and toxicity. Univariate and multivariate analyses were performed.

RESULTS

A total of 63 patients were treated with a median follow-up of 12.5 mo. Approximately 75% of patients underwent vertebrectomy and 25% underwent laminectomy. One-year cumulative incidence of local failure was 19%. LC was significantly improved for patients receiving radiosurgery ≤40 d from surgery compared to that for patients receiving radiosurgery ≥40 d from surgery, 94% vs 75%, respectively, at 1 yr (P = .03). Patients who received preoperative embolization had improved LC with 1-yr LC of 88% vs 76% for those who did not receive preoperative embolization (P = .037). Significant predictors for LC on multivariate analysis were time from surgery to radiosurgery, higher radiotherapy dose, and preoperative embolization. The 1-yr PFS and OS was 56% and 60%, respectively.

CONCLUSION

Postoperative radiosurgery has excellent and durable LC for spine metastasis. An important consideration when planning postoperative radiosurgery is minimizing delay from surgery to radiosurgery. Preoperative embolization and higher radiotherapy dose were associated with improved LC warranting further study.

NCOG-07. FEATURES OF EPILEPTOGENIC BRAIN METASTASES AND THEIR TREATMENT

Patients with brain metastases (BM) may experience seizures at diagnosis or during their treatment. Seizures are associated with decreased overall survival (OS) and poorer quality of life. Therapeutic options may include surgical resection of epileptogenic BM. This study evaluated features of epileptogenic BM and whether surgical resection of these tumors improved seizure control and OS. A retrospective single-center review between 2006-2016 identified 1581 patients with BM. Data analyzed included demographics, primary cancer, systemic treatments, radiographic features of BM, BM treatment modalities, anti-epileptic drugs (AEDs), and seizure characteristics before and after intervention for BM. Chi-squared tests were used for categorical variables. Kaplan-Meier curves and Breslow values were used to assess OS following seizure. Of 1581 patients with BM, 136 (9%) experienced one or more seizures. Seizure was the presenting symptom of BM in 74 (54.4%) patients. Melanoma metastases were most epileptogenic, causing seizure in 38 of 216 (17.6%) patients (p&lt; 0.001). Frontal lobe metastases were most common in patients with seizures (100, 73.5% p=0.033). After median follow-up of 23 months, 48 of 80 (60%) surgical patients were seizure free compared with 27 of 56 (48.2%) non-surgical patients. OS from first seizure was improved in surgical patients versus non-surgical patients (735±133 vs 447±74 days, p=0.043). Frontal lobe tumor resection (n=61) conferred improved survival compared with non-frontal lobe tumor resections (n=19) (698±323 vs 344±132 days, p=0.044). Variables such as demographics, number of BM, tumor histology, and dose of AED were not significantly different between surgical and non-surgical groups. Seizures due to BM cause significant morbidity and mortality. Frontal lobe location and melanoma histology increase seizure risk. Resection of BM was associated with improved seizure control and prolonged OS from the time of first seizure. Further studies should delineate the impact of surgery and determine if a specific constellation of variables warrants prophylactic AEDs.

Data-driven evolution of neurosurgical gene therapy delivery in Parkinson's disease

Loss of nigrostriatal dopaminergic projection neurons is a key pathology in Parkinson's disease, leading to abnormal function of basal ganglia motor circuits and the accompanying characteristic motor features. A number of intraparenchymally delivered gene therapies designed to modify underlying disease and/or improve clinical symptoms have shown promise in preclinical studies and subsequently were evaluated in clinical trials. Here we review the challenges with surgical delivery of gene therapy vectors that limited therapeutic outcomes in these trials, particularly the lack of real-time monitoring of vector administration. These challenges have recently been addressed during the evolution of novel techniques for vector delivery that include the use of intraoperative MRI. The preclinical development of these techniques are described in relation to recent clinical translation in an adeno-associated virus serotype 2-mediated human aromatic L-amino acid decarboxylase gene therapy development programme. This new paradigm allows visualisation of the accuracy and adequacy of viral vector delivery within target structures, enabling intertrial modifications in surgical approaches, cannula design, vector volumes and dosing. The rapid, data-driven evolution of these procedures is unique and has led to improved vector delivery.

Linear accelerator-based radiosurgery is associated with lower incidence of radionecrosis compared with gamma knife for treatment of multiple brain metastases

BACKGROUND

Gamma knife (GK) and linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) both offer excellent local control in the management of multiple brain metastases. The efficacy and toxicity of LINAC and GK SRS have not been directly compared in the modern era. We studied outcomes in patients treated with LINAC SRS and GK at two separate institutions.

METHODS

We identified patients treated with either LINAC or GK who were treated to ≥2 lesions and had available follow up. LINAC patients were treated using single-isocenter multitarget technique. We used Cox regression, Fine and Gray competing risks regression, and nearest neighbor propensity score matching to account for confounders and imbalance between cohorts. Kaplan-Meier curves were used to estimate overall survival and rates of radionecrosis.

RESULTS

We identified 391 patients who were treated in 537 courses to a total 2699 lesions (LINAC: 1014, GK: 1685). After propensity score matching, GK was associated with similar overall survival (HR = 0.86; 95% CI 0.59-1.24; p = 0.41) and higher rate of radionecrosis (HR = 3.83; 95% CI 1.66-8.84; p = 0.002) compared to LINAC. In a secondary propensity score matched analysis comparing radionecrosis in single-fraction LINAC and GK, GK remained associated with higher incidence of radionecrosis (HR = 4.42; 95% CI 1.28-15.29; p = 0.019).

CONCLUSIONS

In this multi-institutional study, we found similar overall survival with lower incidence of radionecrosis in patients treated with LINAC compared to GK SRS. These findings are hypothesis generating and should be validated in an independent cohort.

Single-Isocenter Multitarget Stereotactic Radiosurgery Is Safe and Effective in the Treatment of Multiple Brain Metastases

Purpose

Multiple studies have reported favorable outcomes for stereotactic radiosurgery (SRS) in the treatment of limited brain metastases. An obstacle of SRS in the management of numerous metastases is the longer treatment time using traditional radiosurgery. Single-isocenter multitarget (SIMT) SRS is a novel technique that permits rapid therapy delivery to multiple metastases. There is a lack of clinical evidence regarding its efficacy and safety. We report the outcomes of patients treated with this technique.

Methods and Materials

We reviewed the records of patients with intact or resected brain metastases treated with SRS in 1 to 5 fractions using SIMT technique at our institution, with at least 1 available follow-up brain magnetic resonance imaging. Survival, disease control, and toxicity were evaluated using Cox regression, logistic regression, and Kaplan-Meier analysis.

Results

We identified 173 patients with 1014 brain metastases. Median follow up was 12.7 months. Median beam-on time was 4.1 minutes. The median dose to the brain was 219.4 cGy. Median overall survival and freedom from intracranial progression were 13.2 and 6.3 months, respectively. Overall survival did not differ between patients treated with greater than or less than 4 lesions (hazard ratio, 1.03; 95% confidence interval 0.66-1.61; P = .91). Actuarial 1- and 2-year local control were 99.0% and 95.1%, respectively. Rates of grade 2 and grade 3 or higher radionecrosis were 1.4% and 0.9%, respectively.

Conclusions

SIMT radiosurgery delivered in 1 to 5 fractions offers excellent local control and acceptable toxicity in the treatment of multiple intact and postoperative brain metastases. This technique should be evaluated prospectively.

National Football League Head, Neck and Spine Committee’s Concussion Diagnosis and Management Protocol: 2017-18 season

One of the National Football League’s (NFL) Head, Neck and Spine Committee’s principal goals is to create a ‘best practice’ protocol for concussion diagnosis and management for its players. The science related to concussion diagnosis and management continues to evolve, thus the protocol has evolved contemporaneously. The Fifth International Conference on Concussion in Sport was held in Berlin in 2016, and guidelines for sports concussion diagnosis and management were revised and refined. The NFL Head, Neck and Spine Committee has synthesised the most recent empirical evidence for sports concussion diagnosis and management including the Berlin consensus statement and tailored it to the game played in the NFL. One of the goals of the Committee is to provide a standardised, reliable, efficient and evidence-based protocol for concussion diagnosis and management that can be applied in this professional sport during practice and game day. In this article, the end-of-season version of the 2017–18 NFL Concussion Diagnosis and Management Protocol is described along with its clinical rationale. Immediate actions for concussion programme enhancement and research are reviewed. It is the Committee’s expectation that the protocol will undergo refinement and revision over time as the science and clinical practice related to concussion in sports crystallise

Abstract 4220: Beta-catenin signaling initiates the activation of astrocytes and contributes to the pathogenesis of astrocytomas

Astrocytes are the most abundant cell in the central nervous system (CNS). Following injury to the nervous system, astrocytes respond through a repair process known as astrocyte activation. While the molecular mechanisms of astrocyte activation are not completely established, understanding the dynamic changes that occur in response to injury could help identify critical signaling pathways involved in the pathogenesis of brain tumors. To determine the mechanisms underlying astrocyte activation, including the initiating events and regulatory mediators of this process, we analyzed the molecular signaling changes after scratch injury of astrocytes. We discovered that the interruption and destabilization of cadherin-catenin complexes plays a critical role in the initiation and regulation of astrocyte activation. We further found that similar expression changes and signaling pathways are also featured in gliomas, but were found to exist in a dysregulated manner. Inhibition of β-catenin signaling was also found to diminish both the astrocyte response to injury and the malignant phenotype of gliomas. These findings provide a unique mechanism of normal astrocyte activation and shed light on the pathogenic mechanism of glioma, which may help to develop the diagnostic and therapeutic targets for gliomas.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4220. doi:1538-7445.AM2012-4220

Abstract 5497: An inhibitor of phosphatase PP2A enhances in vivo anticancer activity of a phospho (ADP-ribosyl) polymerase inhibitor (PARPi) combined with temozolomide (TMZ)

We previously showed that a novel inhibitor of PP2A enhances the in vivo activity of TMZ against human glioblastoma xenografts (Lu et al, PNAS 2009;104:11697-11702). Several mechanisms underlie this effect of PP2A inhibition and include an increased rate of cancer cell entry into DNA synthesis, inhibition of cell cycle arrest at G1 and G2/M, and a marked reduction in p53. Because inhibitors of PARP1 have been shown to enhance the activity of cytotoxic cancer drugs by inhibiting repair of single-strand breaks in cells with impaired mechanisms for double-stranded DNA repair (BrCa mutants, triple negative breast cancer cells), we reasoned that blocking other types of DNA-damage defense mechanisms by PP2A inhibition might further enhance the activity of a PARPi combined with TMZ in cancers, not necessarily already deficient in DNA repair. We treated mice bearing xenografts of human melanoma, line A2058, with single agent LB-100, a novel water soluble PP2A inhibitor (Lixte Biotechnology Holdings, Inc., East Setauket, NY; Lu et al, J Neurosurg 2010; 113: 225-233) at 1.5mg/kg by continuous intraperitoneal (i.p.) infusion for 21 days and TMZ at 80mg/kg i.p. days 3,6,9,12,15,18. LB-100 and TMZ were given alone and in combination with each other and in 2-drug combinations with the PARPi, ABT-888 (Sigma), at 6.25 mg/kg i.p. on days 3,6,9,12,15,18, and all three drugs were given together at the same doses and schedules as when used alone or in 2-drug combinations. (ABT-888 was inactive as a single agent and was not used alone). The combination of LB-100 + TMZ was more inhibitory to the xenografts at 21 days than ABT-888 + TMZ, but the 3-drug regimen was most effective and no more toxic than any of the 2-drug regimens. Histologic analysis of xenografts 24 hours after treatment of animals with each of the single agents, each 2-drug regimen, and the 3-drug regimen showed increased apoptosis and necrosis by the 3-drug combination compared to the two-drug regimens, which in turn were more effective that the single agents. Similar results were found in vitro by flow cytometric analysis of A2058 cells 24 hours after exposure to the single agent and 2- and 3-drug regimens. Inclusion of a PP2A inhibitor may increase and extend the effectiveness of cytotoxic regimens containing a PARPi to cancers without acquired mutations in DNA repair.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5497. doi:10.1158/1538-7445.AM2011-5497

Pharmacologic modulation of serine/threonine phosphorylation highly sensitizes PHEO in a MPC cell and mouse model to conventional chemotherapy

Background

The failure of cytotoxic cancer regimens to cure the most drug-resistant, well-differentiated solid tumors has been attributed to the heterogeneity of cell types that differ in their capacities for growth, differentiation, and metastases. We investigated the effect of LB1, a small molecule inhibitor of serine/threonine protein phosphatase 2A (PP2A), on its ability to inhibit a low growth fraction and highly drug-resistant solid neuroendocrine tumor, such as metastatic pheochromocytoma (PHEO). Subsequently, we evaluated the increased efficacy of chemotherapy combined with LB1.

Methodology/Principal Findings

The effect of LB1 and temozolomide (TMZ), a standard chemotherapeutic agent that alone only transiently suppressed the growth and regression of metastatic PHEO, was evaluated in vitro on a single PHEO cell line and in vivo on mouse model of metastatic PHEO. In the present study, we show that metastatic PHEO, for which there is currently no cure, can be eliminated by combining LB1, thereby inhibiting PP2A, with TMZ. This new treatment approach resulted in long term, disease-free survival of up to 40% of animals bearing multiple intrahepatic metastases, a disease state that the majority of patients die from. Inhibition of PP2A was associated with prevention of G1/S phase arrest by p53 and of mitotic arrest mediated by polo-like kinase 1 (Plk-1).

Conclusions/Significance

The elimination of DNA damage-induced defense mechanisms, through transient pharmacologic inhibition of PP2A, is proposed as a new approach for enhancing the efficacy of non-specific cancer chemotherapy regimens against a broad spectrum of low growth fraction tumors very commonly resistant to cytotoxic drugs.

Enhancement of cancer chemotherapy by simultaneously altering cell cycle progression and DNA-damage defenses through global modification of the serine/threonine phospho-proteome

Despite improvements in the therapeutic efficacy of rationally designed cancer treatment regimens, most cancers remain incurable once spread beyond their sites of origin. Failure to achieve sustained control or eradication of cancers arises in large part because a subpopulation of quiescent "cancer stem cells" is insensitive to drugs targeting cell growth and replication and because defense mechanisms critical to survival of the normal cell also protect the cancer cell from cytotoxic injury. Global alteration of signal transduction by inhibition of serine/threonine dephosphorylation has recently been shown to markedly potentiate cancer cell killing by the DNA-methylating drug, temozolomide. Inhibition of the multifunctional protein phosphatase 2A appears to drive quiescent cancer cells into cycle and simultaneously inhibits cycle arrest, permitting cancer cell entry into mitosis despite the presence of chemotherapy induced DNA-damage. Absence of toxicity in animal models suggests that multi-site mutations in pathways regulating cell cycle in cancer cells make them more vulnerable than normal cells to large changes in the balance of phosphorylation-regulated signaling. Global modulation of the serine-threonine phospho-proteome may be a general method for enhancing the effectiveness of cytotoxic cancer therapy.

Inhibition of serine/threonine phosphatase PP2A enhances cancer chemotherapy by blocking DNA damage induced defense mechanisms

A variety of mechanisms maintain the integrity of the genome in the face of cell stress. Cancer cell response to chemotherapeutic and radiation-induced DNA damage is mediated by multiple defense mechanisms including polo-like kinase 1 (Plk-1), protein kinase B (Akt-1), and/or p53 pathways leading to either apoptosis or cell cycle arrest. Subsequently, a subpopulation of arrested viable cancer cells may remain and recur despite aggressive and repetitive therapy. Here, we show that modulation (activation of Akt-1 and Plk-1 and repression of p53) of these pathways simultaneously results in paradoxical enhancement of the effectiveness of cytotoxic chemotherapy. We demonstrate that a small molecule inhibitor, LB-1.2, of protein phosphatase 2A (PP2A) activates Plk-1 and Akt-1 and decreases p53 abundance in tumor cells. Combined with temozolomide (TMZ; a DNA-methylating chemotherapeutic drug), LB-1.2 causes complete regression of glioblastoma multiforme (GBM) xenografts without recurrence in 50% of animals (up to 28 weeks) and complete inhibition of growth of neuroblastoma (NB) xenografts. Treatment with either drug alone results in only short-term inhibition/regression with all xenografts resuming rapid growth. Combined with another widely used anticancer drug, Doxorubicin (DOX, a DNA intercalating agent), LB-1.2 also causes marked GBM xenograft regression, whereas DOX alone only slows growth. Inhibition of PP2A by LB-1.2 blocks cell-cycle arrest and increases progression of cell cycle in the presence of TMZ or DOX. Pharmacologic inhibition of PP2A may be a general method for enhancing the effectiveness of cancer treatments that damage DNA or disrupt components of cell replication.

A dual CT-MR dendrimer contrast agent as a surrogate marker for convection-enhanced delivery of intracerebral macromolecular therapeutic agents

The feasibility of using Gd dendrimer-based macromolecules (Gd-G8 dendrimer) as a dual CT and MR contrast agent for monitoring convection-enhanced delivery of therapy in the brain is evaluated both in vitro and in vivo with optimal dosing established. In vitro CT attenuation values of the Gd-based agents ( approximately 6.0 HU mM(-1)) were approximately 1.6 times greater than iodine-based agents and the attenuation of the Gd-DTPA was comparable to Gd-G8 dendrimer. Visible enhancement was observed on both CT and MR using Gd-G8 dendrimer over a range of 23-78 mM; however, a concentration of at least 47 mM in Gd was required for adequate delineation of the injection site on both CT and MR. MR offers greater sensitivity than CT in estimating the volume of distribution (V(d)) and effectively quantified the agent's concentration and diffusion using T(1) mapping at much lower concentrations of Gd (<10 mM in [Gd]).

Endoscopic procedures for resection of arteriovenous malformations

BACKGROUND

Resection of arteriovenous malformations (AVMs), particularly those located in functional areas, requires precision. To enhance that precision, endoscope-assisted microsurgery has been employed at Loma Linda University.

METHODS

Twenty-five consecutive cases of AVM were treated microsurgically with endoscopic assistance. Patients were divided into two groups: (1) those having AVMs in functional areas, and (2) those whose AVMs extended into the ventricle, either in the trigonal area or the capsulocaudatothalamic area. The endoscope was inserted into the subarachnoid space to interrupt communicating venules around the major draining vein and into the cleavage developed between the AVM venous loops and surrounding brain tissue as shunting arterioles and communicating venules were interrupted. For surgery of intraventricular AVMs, the curved endoscope was inserted into the ventricle, providing visualization of the AVM core, which was dissected from the ventricular side.

RESULTS

AVMs were totally resected in all cases except for two patients with capsulocaudatothalamic AVMs, which were decreased in size sufficiently to receive radiosurgery.

CONCLUSION

Endoscope-assisted microsurgery enhances magnification, illumination, and technical precision while the surgeon is dissecting the AVM core vessels and while operating on AVMs extending into the ventricle.

The safety of intraoperative autologous blood collection and autotransfusion during cesarean section

OBJECTIVE

We evaluated the safety of intraoperative autologous blood collection and autotransfusion during cesarean section.

STUDY DESIGN

A multicenter historical cohort study identified 139 patients in whom autologous blood collection autotransfusion during cesarean section was performed. We also identified 87 control patients who underwent similar surgical procedures at the same centers without autotransfusion. The outcome variables we compared were acute respiratory distress syndrome, amniotic fluid embolism, disseminated intravascular coagulation, need for ventilatory support, infectious morbidity, and the length of postpartum hospitalization.

RESULTS

Demographic and obstetric characteristics were similar in both groups. The ranges of autotransfused volumes were 200 to 11,250 mL at Yale, 225 to 1160 mL at Good Samaritan, and 125 to 4750 mL at Hinsdale. No statistically significant differences existed between the two groups in any of the outcome variables analyzed. No case of acute respiratory distress syndrome or amniotic fluid embolism was identified in either group.

CONCLUSIONS

Our multicenter experience reveals no demonstrably increased risk of complications in patients receiving autologous blood collection autotransfusion during cesarean section.

Hb Hinsdale [beta 139 (H17)Asn----Lys]: a variant in the central cavity showing reduced affinity for oxygen and 2,3-diphosphoglycerate

Hb Hinsdale was detected in two sisters and in a son and daughter of one of them as a band migrating in the Hb F position on cellulose acetate, pH 8.5. On citrate agar (pH 6.3) the variant hemoglobin has a mobility like that of Hb S. Hematologic data from these individuals appear normal except for mild anemia. Oxygen affinity studies show that the variant has low affinity for oxygen and reduced cooperativity. Results of tests for instability were negative. The mutation involves a site that lies in the central cavity close to the 2,3-diphosphoglycerate pocket, so it is not surprising that the variant shows a reduced ability to react with this effector molecule.