Primary and metastatic tumors exhibit systems-level differences in dependence on mitochondrial respiratory function.

The Warburg effect, aerobic glycolysis, is a hallmark feature of cancer cells grown in culture. However, the relative roles of glycolysis and respiratory metabolism in supporting in vivo tumor growth and processes such as tumor dissemination and metastatic growth remain poorly understood, particularly on a systems level. Using a CRISPRi mini-library enriched for mitochondrial ribosomal protein and respiratory chain genes in multiple human lung cancer cell lines, we analyzed in vivo metabolic requirements in xenograft tumors grown in distinct anatomic contexts. While knockdown of mitochondrial ribosomal protein and respiratory chain genes (mito-respiratory genes) has little impact on growth in vitro, tumor cells depend heavily on these genes when grown in vivo as either flank or primary orthotopic lung tumor xenografts. In contrast, respiratory function is comparatively dispensable for metastatic tumor growth. RNA-Seq and metabolomics analysis of tumor cells expressing individual sgRNAs against mito-respiratory genes indicate overexpression of glycolytic genes and increased sensitivity of glycolytic inhibition compared to control when grown in vitro, but when grown in vivo as primary tumors these cells down-regulate glycolytic mechanisms. These studies demonstrate that discrete perturbations of mitochondrial respiratory chain function impact in vivo tumor growth in a context-specific manner with differential impacts on primary and metastatic tumors.

A high-throughput screen of real-time ATP levels in individual cells reveals mechanisms of energy failure.

Insufficient or dysregulated energy metabolism may underlie diverse inherited and degenerative diseases, cancer, and even aging itself. ATP is the central energy carrier in cells, but critical pathways for regulating ATP levels are not systematically understood. We combined a pooled clustered regularly interspaced short palindromic repeats interference (CRISPRi) library enriched for mitochondrial genes, a fluorescent biosensor, and fluorescence-activated cell sorting (FACS) in a high-throughput genetic screen to assay ATP concentrations in live human cells. We identified genes not known to be involved in energy metabolism. Most mitochondrial ribosomal proteins are essential in maintaining ATP levels under respiratory conditions, and impaired respiration predicts poor growth. We also identified genes for which coenzyme Q10 (CoQ10) supplementation rescued ATP deficits caused by knockdown. These included CoQ10 biosynthetic genes associated with human disease and a subset of genes not linked to CoQ10 biosynthesis, indicating that increasing CoQ10 can preserve ATP in specific genetic contexts. This screening paradigm reveals mechanisms of metabolic control and genetic defects responsive to energy-based therapies.

Germline MUTYH Mutation in a Pediatric Cancer Survivor Developing a Secondary Malignancy.

Radiotherapy-induced second malignant neoplasms (SMNs) are a severe late complication in pediatric cancer survivors. Germline mutations in tumor suppressor genes contribute to SMNs; however, the most relevant germline variants mediating susceptibility are not fully defined. The authors performed matched whole-exome sequencing analyses of germline and tumor DNA from 4 pediatric solid tumor survivors who subsequently developed radiation-associated SMNs. Pathogenic and predicted deleterious germline variants were identified for each patient and validated with Sanger sequencing. These germline variants were compared with germline variants in a cohort of 59 pediatric patients diagnosed with primary sarcomas. Pathway analysis was performed to test for similarities in the germline variant profiles between individuals diagnosed with SMNs or primary sarcomas. One index patient was found to have a pathogenic germline monoallelic mutation in the MUTYH gene, which encodes the base excision repair enzyme adenine DNA glycosylase. This specific germline mutation is associated with a form of familial adenomatous polyposis, a new diagnosis in the patient. Germline-level genetic similarity exists between SMN-developing patients and patients developing primary sarcomas, with relevant genes involved in signal transduction and DNA repair mechanisms. The authors identify a germline MUTYH mutation in a pediatric cancer survivor developing an SMN. Germline mutations involving specific pathways such as base excision repair may identify individuals at risk for developing SMNs. The composition of germline variants in individual patients may enable estimates of patient-specific risk for developing SMNs. The authors anticipate that further analyses of germline genomes and epigenomes will reveal diverse genes and mechanisms influencing cancer risk.

Monoallelic loss of the imprinted gene Grb10 promotes tumor formation in irradiated Nf1+/- mice.

Imprinted genes are expressed from only one parental allele and heterozygous loss involving the expressed allele is sufficient to produce complete loss of protein expression. Genetic alterations are common in tumorigenesis but the role of imprinted genes in this process is not well understood. In earlier work we mutagenized mice heterozygous for the Neurofibromatosis I tumor suppressor gene (NF1) to model radiotherapy-associated second malignant neoplasms that arise in irradiated NF1 patients. Expression analysis of tumor cell lines established from our mouse models identified Grb10 expression as widely absent. Grb10 is an imprinted gene and polymorphism analysis of cell lines and primary tumors demonstrates that the expressed allele is commonly lost in diverse Nf1 mutant tumors arising in our mouse models. We performed functional studies to test whether Grb10 restoration or loss alter fundamental features of the tumor growth. Restoring Grb10 in Nf1 mutant tumors decreases proliferation, decreases soft agar colony formation and downregulates Ras signaling. Conversely, Grb10 silencing in untransformed mouse embryo fibroblasts significantly increased cell proliferation and increased Ras-GTP levels. Expression of a constitutively activated MEK rescued tumor cells from Grb10-mediated reduction in colony formation. These studies reveal that Grb10 loss can occur during in vivo tumorigenesis, with a functional consequence in untransformed primary cells. In tumors, Grb10 loss independently promotes Ras pathway hyperactivation, which promotes hyperproliferation, an early feature of tumor development. In the context of a robust Nf1 mutant mouse model of cancer this work identifies a novel role for an imprinted gene in tumorigenesis.

Parameters influencing local control of meningiomas treated with radiosurgery.

To identify parameters that influence local control after stereotactic radiosurgery (SRS) for meningiomas we retrospectively analyzed all meningiomas treated with Gamma Knife SRS at our institution from 1991 to 2007. Endpoints were measured from the date of SRS and estimated using the Kaplan-Meier method; subgroups were compared with log-rank tests. Sex, performance status, age, SRS setting, radiation dose, grade, volume and location were evaluated with univariate and multivariate Cox proportional hazards analyses. Of 280 patients with 438 tumors, 264 patients with clinical follow-up and 406 tumors with imaging follow-up were analyzed (median follow-up: 75.9 months). Thirty-seven percent of the tumors had no tissue diagnosis, 32 % were benign (grade I), 12 % atypical (grade II), and 19 % malignant (grade III). Five-year freedom from progression (FFP) was 97 % for presumed meningiomas, 87 % for grade I tumors, 56 % for grade II tumors, and 47 % for grade III tumors (p < 0.0001). Five-year FFP probabilities for upfront SRS versus SRS at recurrence after surgery versus SRS at recurrence after RT were 97, 86, and 38 %, respectively (p < 0.0001). Univariate analysis revealed that higher grade, larger target volume (median diameter: 2.4 cm) and SRS setting were associated with poorer FFP. Only target volume and SRS setting remained significant on multivariate analysis. Local control of presumed and grade I meningiomas is excellent with Gamma Knife SRS, but is suboptimal with high-grade tumors as well as for those treated at recurrence after RT or of large volume.

Investigating the clinical advantages of a robotic linac equipped with a multileaf collimator in the treatment of brain and prostate cancer patients.

The purpose of this study was to evaluate the performance of a commercially avail-able CyberKnife system with a multileaf collimator (CK-MLC) for stereotactic body radiotherapy (SBRT) and standard fractionated intensity-modulated radiotherapy (IMRT) applications. Ten prostate and ten intracranial cases were planned for the CK-MLC. Half of these cases were compared with clinically approved SBRT plans generated for the CyberKnife with circular collimators, and the other half were compared with clinically approved standard fractionated IMRT plans generated for conventional linacs. The plans were compared on target coverage, conformity, homogeneity, dose to organs at risk (OAR), low dose to the surrounding tissue, total monitor units (MU), and treatment time. CK-MLC plans generated for the SBRT cases achieved more homogeneous dose to the target than the CK plans with the circular collimators, for equivalent coverage, conformity, and dose to OARs. Total monitor units were reduced by 40% to 70% and treatment time was reduced by half. The CK-MLC plans generated for the standard fractionated cases achieved prescription isodose lines between 86% and 93%, which was 2%-3% below the plans generated for conventional linacs. Compared to standard IMRT plans, the total MU were up to three times greater for the prostate (whole pelvis) plans and up to 1.4 times greater for the intracranial plans. Average treatment time was 25min for the whole pelvis plans and 19 min for the intracranial cases. The CK-MLC system provides significant improvements in treatment time and target homogeneity compared to the CK system with circular collimators, while main-taining high conformity and dose sparing to critical organs. Standard fractionated plans for large target volumes (> 100 cm3) were generated that achieved high prescription isodose levels. The CK-MLC system provides more efficient SRS and SBRT treatments and, in select clinical cases, might be a potential alternative for standard fractionated treatments.

Mutational Status and Clinical Outcomes Following Systemic Therapy with or without Focal Radiation for Resected Melanoma Brain Metastases.

BACKGROUND: Brain metastases occur frequently in advanced melanoma and traditionally require surgery and radiation therapy. New evidence demonstrates that systemic therapies are effective for controlling metastatic melanoma brain metastases. This study evaluated outcomes after resection of melanoma brain metastases treated with systemic therapy, with or without focal radiotherapy. METHODS: All patients received immunotherapy or BRAF/MEK inhibitors preoperatively or in the immediate 3 months postoperatively. Resection cavity failure, distant central nervous system progression, and adverse radiation effects were reported in the presence and absence of focal radiotherapy using the Kaplan-Meier method. RESULTS: Between 2011 and 2020, 37 resection cavities in 29 patients met criteria for analysis. Of lesions, 22 (59%) were treated with focal radiotherapy, and 15 (41%) were treated with targeted therapy or immunotherapy alone. The 12- and 24-month freedom from local recurrence was 64.8% (95% confidence interval [CI] 42.1%-99.8%) and 46.3% (95% CI 24.5%-87.5%), respectively, for systemic therapy alone and 93.3% (95% CI 81.5%-100%) at both time points for focal radiotherapy (P = 0.01). On univariate analysis, focal radiotherapy was the only significant factor associated with reduction of local recurrence risk (hazard ratio 0.10, 95% CI 0.01-0.85; P = 0.04). There were no significant differences in central nervous system progression-free survival or overall survival between patients who received systemic therapy plus focal radiotherapy compared with systemic therapy alone. BRAF mutation status was reviewed for either the brain metastasis (n = 9 patients, 31%) or the primary site (n = 20 patients, 69%), and patients harboring BRAFV600E mutations had worse progression-free survival (P = 0.043). CONCLUSIONS: Focal radiotherapy with systemic therapy for resected melanoma brain metastases significantly decreased resection cavity recurrence compared with systemic therapy alone. BRAF mutation status correlated with poorer outcomes.

Adverse radiation effect and freedom from progression following repeat stereotactic radiosurgery for brain metastases.

OBJECTIVE: The authors previously evaluated risk and time course of adverse radiation effects (AREs) following stereotactic radiosurgery (SRS) for brain metastases, excluding lesions treated after prior SRS. In the present analysis they focus specifically on single-fraction salvage SRS to brain metastases previously treated with SRS or hypofractionated SRS (HFSRS), evaluating freedom from progression (FFP) and the risk and time course of AREs. METHODS: Brain metastases treated from September 1998 to May 2019 with single-fraction SRS after prior SRS or HFSRS were analyzed. Serial follow-up magnetic resonance imaging (MRI) and surgical pathology reports were reviewed to score local treatment failure and AREs. The Kaplan-Meier method was used to estimate FFP and risk of ARE measured from the date of repeat SRS with censoring at the last brain MRI. RESULTS: A total of 229 retreated brain metastases in 124 patients were evaluable. The most common primary cancers were breast, lung, and melanoma. The median interval from prior SRS/HFSRS to repeat SRS was 15.4 months, the median prescription dose was 18 Gy, and the median duration of follow-up imaging was 14.5 months. At 1 year after repeat SRS, FFP was 80% and the risk of symptomatic ARE was 11%. The 1-year risk of imaging changes, including asymptomatic RE and symptomatic ARE, was 30%. Among lesions that demonstrated RE, the median time to onset was 6.7 months (IQR 4.7-9.9 months) and the median time to peak imaging changes was 10.1 months (IQR 5.6-13.6 months). Lesion size by quadratic mean diameter (QMD) showed similar results for QMDs ranging from 0.75 to 2.0 cm (1-year FFP 82%, 1-year risk of symptomatic ARE 11%). For QMD < 0.75 cm, the 1-year FFP was 86% and the 1-year risk of symptomatic ARE was only 2%. Outcomes were worse for QMDs 2.01-3.0 cm (1-year FFP 65%, 1-year risk of symptomatic ARE 24%). The risk of symptomatic ARE was not increased with tyrosine kinase inhibitors or immunotherapy before or after repeat SRS. CONCLUSIONS: RE on imaging was common after repeat SRS (30% at 1 year), but the risk of a symptomatic ARE was much less (11% at 1 year). The results of repeat single-fraction SRS were good for brain metastases ≤ 2 cm. The authors recommend an interval ≥ 6 months from prior SRS and a prescription dose ≥ 18 Gy. Alternatives such as HFSRS, laser interstitial thermal therapy, or resection with adjuvant radiation should be considered for recurrent brain metastases > 2 cm.

Molecular Features of Resected Melanoma Brain Metastases, Clinical Outcomes, and Responses to Immunotherapy.

Importance: Central nervous system (CNS)-penetrant systemic therapies have significantly advanced care for patients with melanoma brain metastases. However, improved understanding of the molecular landscape and microenvironment of these lesions is needed to both optimize patient selection and advance treatment approaches. Objective: To evaluate how bulk and single-cell genomic features of melanoma brain metastases are associated with clinical outcome and treatment response. Design, Setting, and Participants: This cohort study analyzed bulk DNA sequencing and single nuclear RNA-sequencing data from resected melanoma brain metastases and included 94 consecutive patients with a histopathologically confirmed diagnosis of melanoma brain metastasis who underwent surgical resection at a single National Comprehensive Cancer Network cancer center in San Francisco, California, from January 1, 2009, to December 31, 2022. Exposure: A Clinical Laboratory Improvement Amendments-certified targeted sequencing assay was used to analyze tumor resection specimens, with a focus on BRAF V600E alteration. For frozen pathologic specimens from CNS treatment-naive patients undergoing surgical resection, commercial single nuclear RNA sequencing approaches were used. Main Outcomes and Measures: The primary outcome was overall survival (OS). Secondary outcomes included CNS progression-free survival (PFS), microenvironmental composition with decreased T-cell and macrophage populations, and responses to immunotherapy. Results: To correlate molecular status with clinical outcome, Kaplan-Meier survival analysis of 94 consecutive patients (median age, 64 years [range, 24-82 years]; 70 men [74%]) with targeted BRAF alteration testing showed worse median intracranial PFS (BRAF variant: 3.6 months [IQR, 0.1-30.6 months]; BRAF wildtype: 11.0 months [IQR, 0.8-81.5 months]; P < .001) and OS (BRAF variant: 9.8 months [IQR, 2.5-69.4 months]; BRAF wildtype: 23.2 months [IQR, 1.1-102.5 months]; P = .005; log-rank test) in BRAF V600E variant tumors. Multivariable Cox proportional hazards regression analysis revealed that BRAF V600E status was an independent variable significantly associated with both PFS (hazard ratio [HR], 2.65; 95% CI, 1.54-4.57; P < .001) and OS (HR, 1.96; 95% CI, 1.08-3.55; P = .03). For the 45 patients with resected melanoma brain metastases undergoing targeted DNA sequencing, molecular classification recapitulated The Cancer Genome Atlas groups (NRAS variant, BRAF variant, NF1 variant, and triple wildtype) with no subtype enrichment within the brain metastasis cohort. On a molecular level, BRAF V600E variant lesions were found to have a significantly decreased tumor mutation burden. Moreover, single nuclear RNA sequencing of treatment-naive BRAF V600E variant (n = 3) brain metastases compared with BRAF wildtype (n = 3) brain metastases revealed increased immune cell populations in BRAF wildtype tumors (mean [SD], 11% [4.1%] vs 3% [1.6%] CD45-positive cells; P = .04). Survival analysis of postoperative immunotherapy responses by BRAF status revealed that BRAF wildtype lesions were associated with a response to checkpoint inhibition (median OS: with immunotherapy, undefined; without immunotherapy, 13.0 months [range, 1.1-61.7 months]; P = .001; log-rank test) while BRAF variant lesions (median OS: with immunotherapy, 9.8 months [range, 2.9-39.8 months]; without immunotherapy, 9.5 months [range, 2.5-67.2 months]; P = .81; log-rank test) were not. Conclusions and Relevance: This molecular analysis of patients with resected melanoma brain metastases found that BRAF V600E alteration is an important translational biomarker associated with worse clinical outcomes, differential microenvironmental composition, and benefit from immunotherapy. Patients with BRAF V600E variant melanoma brain metastases may thus benefit from alternative CNS-penetrant systemic regimens.

Considerations for carcinogenesis countermeasure development using mouse models.

Activities in space will expose humans to profoundly new environments, challenging human performance and will require innovative supportive technologies. Among these environmental variables, exposure to ionizing radiation is a major concern for astronauts, as the long-term effects of exposure on diverse tissues are poorly understood. This need however creates opportunities for novel approaches, particularly in the development of countermeasures against the effects of ionizing radiation exposure. Carcinogenesis presents a unique challenge as a disease process, due to the inherent complexities of the process and the challenges of obtaining a large volume of clinical evidence. Thus, developing the countermeasures to address potential effects of ionizing radiation exposure will require understanding biological underpinnings to design countermeasures effectively in conjunction with highly robust modeling approaches to test and examine in vivo. This review will highlight specific considerations for accelerated development of space radiation countermeasures against carcinogenesis.

Resection with intraoperative cesium-131 brachytherapy as salvage therapy for recurrent brain tumors.

OBJECTIVE: The authors' objective was to examine the safety and efficacy of salvage intracranial cesium-131 brachytherapy in combination with resection of recurrent brain tumors. METHODS: The authors conducted a retrospective chart review of consecutive patients treated with intraoperative intracranial cesium-131 brachytherapy at a single institution. Permanent suture-stranded cesium-131 seeds were implanted in the resection cavity after maximal safe tumor resection. The primary outcomes of interest were local, locoregional (within 1 cm), and intracranial control, as well as rates of overall survival (OS), neurological death, symptomatic adverse radiation effects (AREs), and surgical complication rate graded according to Common Terminology Criteria for Adverse Events version 5.0. RESULTS: Between 2016 and 2020, 36 patients received 40 consecutive cesium-131 implants for 42 recurrent brain tumors and received imaging follow-up for a median (interquartile range [IQR]) of 17.0 (12.7-25.9) months. Twenty patients (55.6%) with 22 implants were treated for recurrent brain metastasis, 12 patients (33.3%) with 16 implants were treated for recurrent atypical (n = 7) or anaplastic (n = 5) meningioma, and 4 patients (11.1%) were treated for other recurrent primary brain neoplasms. All except 1 tumor (97.6%) had received prior radiotherapy, including 20 (47.6%) that underwent 2 or more prior radiotherapy treatments and 23 (54.8%) that underwent prior resection. The median (IQR) tumor size was 3.0 (2.3-3.7) cm, and 17 lesions (40.5%) had radiographic evidence of ARE prior to salvage therapy. Actuarial 1-year local/locoregional/intracranial control rates for the whole cohort and patients with metastases and meningiomas were 91.6%/83.4%/47.9%, 88.8%/84.4%/45.4%, and 100%/83.9%/46.4%, respectively. No cases of local recurrence of any histology (0 of 27) occurred after gross-total resection (p = 0.012, log-rank test). The 1-year OS rates for the whole cohort and patients with metastases and meningiomas were 82.7%, 79.1%, and 91.7%, respectively, and the median (IQR) survival of all patients was 26.7 (15.6-36.4) months. Seven patients (19.4%) experienced neurological death from progressive intracranial disease (7 of 14 total deaths [50%]), 5 (13.9%) of whom died of leptomeningeal disease. Symptomatic AREs were observed in 9.5% of resection cavities (n = 4), of which 1 (2.4%) was grade 3 in severity. The surgical complication rate was 16.7% (n = 7); 4 (9.5%) of these patients had grade 3 or higher complications, including 1 patient (2.4%) who died perioperatively. CONCLUSIONS: Cesium-131 brachytherapy resulted in good local control and acceptable rates of symptomatic AREs and surgical complications in this heavily pretreated cohort, and it may be a reasonable salvage adjuvant treatment for this patient population.

Neuro-Oncology Practice Clinical Debate: Early treatment or observation for patients with newly diagnosed oligodendroglioma and small-volume residual disease.

Advances in treatment of oligodendroglioma represent arguably the most significant recent development in the treatment of brain tumors, with multiple clinical trials demonstrating that median survival is approximately doubled in patients with World Health Organization grade II and III 1p/19q codeleted gliomas (ie, oligodendrogliomas) treated with procarbazine, lomustine, vincristine chemotherapy and radiation vs radiation alone. However, chemoradiotherapy itself is not without morbidity, including both short-term toxicities primarily related to chemotherapy and longer-term cognitive issues likely due to radiation. Patients and physicians both desire maximally effective therapy with minimal toxicity, and it remains unclear whether some patients with macroscopic residual disease after surgery can safely delay therapy, to avoid or delay toxicity, while simultaneously preserving the full benefits of treatment. In this article, experts in the field discuss the rationale for the approaches of up-front treatment with chemoradiotherapy and initial observation, respectively.

Irradiation of Nf1 mutant mouse models of spinal plexiform neurofibromas drives pathologic progression and decreases survival.

BACKGROUND: Genetically susceptible individuals can develop malignancies after irradiation of normal tissues. In the context of therapeutic irradiation, it is not known whether irradiating benign neoplasms in susceptible individuals promotes neoplastic transformation and worse clinical outcomes. Individuals with Neurofibromatosis 1 (NF1) are susceptible to both radiation-induced second malignancies and spontaneous progression of plexiform neurofibromas (PNs) to malignant peripheral nerve sheath tumors (MPNSTs). The role of radiotherapy in the treatment of benign neoplasms such as PNs is unclear. METHODS: To test whether radiotherapy promotes neoplastic progression of PNs and reduces overall survival, we administered spinal irradiation (SI) to conditional knockout mouse models of NF1-associated PNs in 2 germline contexts: Nf1 fllfl ; PostnCre + and Nf1 fl/- ; PostnCre + . Both genotypes develop extensive Nf1 null spinal PNs, modeling PNs in NF1 patients. A total of 101 mice were randomized to 0 Gy, 15 Gy (3 Gy × 5), or 30 Gy (3 Gy × 10) of spine-focused, fractionated SI and aged until signs of illness. RESULTS: SI decreased survival in both Nf1 fllfl mice and Nf1 fl/- mice, with the worst overall survival occurring in Nf1 fl/- mice receiving 30 Gy. SI was also associated with increasing worrisome histologic features along the PN-MPNST continuum in PNs irradiated to higher radiation doses. CONCLUSIONS: This preclinical study provides experimental evidence that irradiation of pre-existing PNs reduces survival and may shift PNs to higher grade neoplasms.

Differentiating Radiation Necrosis from Brain Tumor Using Hyperpolarized Carbon-13 MR Metabolic Imaging.

PURPOSE: Differentiation between radiation-induced necrosis and tumor recurrence is crucial to determine proper management strategies but continues to be one of the central challenges in neuro-oncology. We hypothesized that hyperpolarized 13C MRI, a unique technique to measure real-time in vivo metabolism, would distinguish radiation necrosis from tumor on the basis of cell-intrinsic metabolic differences. The purpose of this study was to explore the feasibility of using hyperpolarized [1-13C]pyruvate for differentiating radiation necrosis from brain tumors. PROCEDURES: Radiation necrosis was initiated by employing a CT-guided 80-Gy single-dose irradiation of a half cerebrum in mice (n = 7). Intracerebral tumor was modeled with two orthotopic mouse models: GL261 glioma (n = 6) and Lewis lung carcinoma (LLC) metastasis (n = 7). 13C 3D MR spectroscopic imaging data were acquired following hyperpolarized [1-13C]pyruvate injection approximately 89 and 14 days after treatment for irradiated and tumor-bearing mice, respectively. The ratio of lactate to pyruvate (Lac/Pyr), normalized lactate, and pyruvate in contrast-enhancing lesion was compared between the radiation-induced necrosis and brain tumors. Histopathological analysis was performed from resected brains. RESULTS: Conventional MRI exhibited typical radiographic features of radiation necrosis and brain tumor with large areas of contrast enhancement and T2 hyperintensity in all animals. Normalized lactate in radiation necrosis (0.10) was significantly lower than that in glioma (0.26, P = .004) and LLC metastatic tissue (0.25, P = .00007). Similarly, Lac/Pyr in radiation necrosis (0.18) was significantly lower than that in glioma (0.55, P = .00008) and LLC metastasis (0.46, P = .000008). These results were consistent with histological findings where tumor-bearing brains were highly cellular, while irradiated brains exhibited pathological markers consistent with reparative changes from radiation necrosis. CONCLUSION: Hyperpolarized 13C MR metabolic imaging of pyruvate is a noninvasive imaging method that differentiates between radiation necrosis and brain tumors, providing a groundwork for further clinical investigation and translation for the improved management of patients with brain tumors.

Stereotactic Radiosurgery to More Than 10 Brain Metastases: Evidence to Support the Role of Radiosurgery for Ideal Hippocampal Sparing in the Treatment of Multiple Brain Metastases.

BACKGROUND: Brain metastases are a common occurrence, with literature supporting the treatment of a limited number of brain metastases with stereotactic radiosurgery (SRS), as opposed to whole brain radiotherapy (WBRT). Less well understood is the role of SRS in patients with ≥10 brain metastases. METHODS: Patients treated with SRS to ≥10 brain metastases without concurrent WBRT between March 1999 and December 2016 were reviewed. Analysis was performed for overall survival, treated lesion freedom from progression (FFP), freedom from new metastases (FFNMs), and adverse radiation effect. Hippocampal volumes were retrospectively generated in patients treated with up-front SRS for evaluation of dose volume metrics. RESULTS: A total of 143 patients were identified with 75 patients having up-front SRS and 68 patients being treated as salvage therapy after prior WBRT. The median number of lesions per patient was 13 (interquartile range [IQR], 11-17). Median total volume of treatment was 4.1 cm3 (IQR, 2.0-9.9 cm3). The median 12-month FFP for up-front and salvage treatment was 96.8% (95% confidence interval [CI], 95.5-98.1) and 83.6% (95% CI, 79.9-87.5), respectively (P < 0.001). Twelve-month FFNMs for up-front and salvage SRS was 18.8% (95% CI, 10.9-32.3) versus 19.2% (95% CI, 9.7-37.8), respectively (P = 0.90). The mean hippocampal dose was 150 cGy (IQR, 100-202 cGy). CONCLUSIONS: Excellent rates of local control can be achieved when treating patients with >10 intracranial metastases either in the up-front or salvage setting. Hippocampal sparing is readily achievable with expected high rates of new metastatic lesions in treated patients.

Nf1-Mutant Tumors Undergo Transcriptome and Kinome Remodeling after Inhibition of either mTOR or MEK.

Loss of the tumor suppressor NF1 leads to activation of RAS effector pathways, which are therapeutically targeted by inhibition of mTOR (mTORi) or MEK (MEKi). However, therapeutic inhibition of RAS effectors leads to the development of drug resistance and ultimately disease progression. To investigate molecular signatures in the context of NF1 loss and subsequent acquired drug resistance, we analyzed the exomes, transcriptomes, and kinomes of Nf1-mutant mouse tumor cell lines and derivatives of these lines that acquired resistance to either MEKi or mTORi. Biochemical comparisons of this unique panel of tumor cells, all of which arose in Nf1+/- mice, indicate that loss of heterozygosity of Nf1 as an initial genetic event does not confer a common biochemical signature or response to kinase inhibition. Although acquired drug resistance by Nf1-mutant tumor cells was accompanied by altered kinomes and irreversibly altered transcriptomes, functionally in multiple Nf1-mutant tumor cell lines, MEKi resistance was a stable phenotype, in contrast to mTORi resistance, which was reversible. Collectively, these findings demonstrate that Nf1-mutant tumors represent a heterogeneous group biochemically and undergo broader remodeling of kinome activity and gene expression in response to targeted kinase inhibition.

Defining the ATPome reveals cross-optimization of metabolic pathways.

Disrupted energy metabolism drives cell dysfunction and disease, but approaches to increase or preserve ATP are lacking. To generate a comprehensive metabolic map of genes and pathways that regulate cellular ATP-the ATPome-we conducted a genome-wide CRISPR interference/activation screen integrated with an ATP biosensor. We show that ATP level is modulated by distinct mechanisms that promote energy production or inhibit consumption. In our system HK2 is the greatest ATP consumer, indicating energy failure may not be a general deficiency in producing ATP, but rather failure to recoup the ATP cost of glycolysis and diversion of glucose metabolites to the pentose phosphate pathway. We identify systems-level reciprocal inhibition between the HIF1 pathway and mitochondria; glycolysis-promoting enzymes inhibit respiration even when there is no glycolytic ATP production, and vice versa. Consequently, suppressing alternative metabolism modes paradoxically increases energy levels under substrate restriction. This work reveals mechanisms of metabolic control, and identifies therapeutic targets to correct energy failure.

A Prognostic Gene-Expression Signature and Risk Score for Meningioma Recurrence After Resection.

BACKGROUND: Prognostic markers for meningioma are needed to risk-stratify patients and guide postoperative surveillance and adjuvant therapy. OBJECTIVE: To identify a prognostic gene signature for meningioma recurrence and mortality after resection using targeted gene-expression analysis. METHODS: Targeted gene-expression analysis was used to interrogate a discovery cohort of 96 meningiomas and an independent validation cohort of 56 meningiomas with comprehensive clinical follow-up data from separate institutions. Bioinformatic analysis was used to identify prognostic genes and generate a gene-signature risk score between 0 and 1 for local recurrence. RESULTS: We identified a 36-gene signature of meningioma recurrence after resection that achieved an area under the curve of 0.86 in identifying tumors at risk for adverse clinical outcomes. The gene-signature risk score compared favorably to World Health Organization (WHO) grade in stratifying cases by local freedom from recurrence (LFFR, P < .001 vs .09, log-rank test), shorter time to failure (TTF, F-test, P < .0001), and overall survival (OS, P < .0001 vs .07) and was independently associated with worse LFFR (relative risk [RR] 1.56, 95% CI 1.30-1.90) and OS (RR 1.32, 95% CI 1.07-1.64), after adjusting for clinical covariates. When tested on an independent validation cohort, the gene-signature risk score remained associated with shorter TTF (F-test, P = .002), compared favorably to WHO grade in stratifying cases by OS (P = .003 vs P = .10), and was significantly associated with worse OS (RR 1.86, 95% CI 1.19-2.88) on multivariate analysis. CONCLUSION: The prognostic meningioma gene-expression signature and risk score presented may be useful for identifying patients at risk for recurrence.

mTOR-independent translational control of the extrinsic cell death pathway by RalA.

Oncogenic potential is associated with translational regulation, and the prevailing view is that oncogenes use mTOR-dependent pathways to up-regulate the synthesis of proteins critical for transformation. In this study, we show that RalA, a key mediator of Ras transformation, is also linked to the translational machinery. At least part of this linkage, however, is independent of mTOR and acts through RalBP1 to suppress cdc42-mediated activation of S6 kinase and the translation of the antiapoptotic protein FLIP(S). This action, rather than contributing to transformation, opens a latent tumor-suppressive mechanism that can be activated by tumor necrosis factor-related apoptosis-inducing ligand. These results show that the translational machinery is linked to tumor suppression as well as cell-proliferative pathways and that the reestablishment of cell death pathways by activation of the Ral oncogenic program provides a means for selective therapeutic targeting of Ral-driven malignancies.