Cellular Density in Adult Glioma, Estimated with MR Imaging Data and a Machine Learning Algorithm, Has Prognostic Power Approaching World Health Organization Histologic Grading in a Cohort of 1181 Patients

BACKGROUND AND PURPOSE

Recent advances in machine learning have enabled image-based prediction of local tissue pathology in gliomas, but the clinical usefulness of these predictions is unknown. We aimed to evaluate the prognostic ability of imaging-based estimates of cellular density for patients with gliomas, with comparison to the gold standard reference of World Health Organization grading.

MATERIALS AND METHODS

Data from 1181 (207 grade II, 246 grade III, 728 grade IV) previously untreated patients with gliomas from a single institution were analyzed. A pretrained random forest model estimated voxelwise tumor cellularity using MR imaging data. Maximum cellular density was correlated with the World Health Organization grade and actual survival, correcting for covariates of age and performance status.

RESULTS

A maximum estimated cellular density of >7681 nuclei/mm2 was associated with a worse prognosis and a univariate hazard ratio of 4.21 (P < .001); the multivariate hazard ratio after adjusting for covariates of age and performance status was 2.91 (P < .001). The concordance index between maximum cellular density (adjusted for covariates) and survival was 0.734. The hazard ratio for a high World Health Organization grade (IV) was 7.57 univariate (P < .001) and 5.25 multivariate (P < .001). The concordance index for World Health Organization grading (adjusted for covariates) was 0.761. The maximum cellular density was an independent predictor of overall survival, and a Cox model using World Health Organization grade, maximum cellular density, age, and Karnofsky performance status had a higher concordance (C = 0.764; range 0.748-0.781) than the component predictors.

CONCLUSIONS

Image-based estimation of glioma cellularity is a promising biomarker for predicting survival, approaching the prognostic power of World Health Organization grading, with added values of early availability, low risk, and low cost.

Suppressed immune microenvironment and repertoire in brain metastases from patients with resected non-small-cell lung cancer

BACKGROUND

The tumor immune microenvironment (TIME) of lung cancer brain metastasis is largely unexplored. We carried out immune profiling and sequencing analysis of paired resected primary tumors and brain metastases of non-small-cell lung carcinoma (NSCLC).

PATIENTS AND METHODS

TIME profiling of archival formalin-fixed and paraffin-embedded specimens of paired primary tumors and brain metastases from 39 patients with surgically resected NSCLCs was carried out using a 770 immune gene expression panel and by T-cell receptor beta repertoire (TCRβ) sequencing. Immunohistochemistry was carried out for validation. Targeted sequencing was carried out to catalog hot spot mutations in cancer genes.

RESULTS

Somatic hot spot mutations were mostly shared between both tumor sites (28/39 patients; 71%). We identified 161 differentially expressed genes, indicating inhibition of dendritic cell maturation, Th1, and leukocyte extravasation signaling pathways, in brain metastases compared with primary tumors (P < 0.01). The proinflammatory cell adhesion molecule vascular cell adhesion protein 1 was significantly suppressed in brain metastases compared with primary tumors. Brain metastases exhibited lower T cell and elevated macrophage infiltration compared with primary tumors (P < 0.001). T-cell clones were expanded in 64% of brain metastases compared with their corresponding primary tumors. Furthermore, while TCR repertoires were largely shared between paired brain metastases and primary tumors, T-cell densities were sparse in the metastases.

CONCLUSION

We present findings that suggest that the TIME in brain metastases from NSCLC is immunosuppressed and comprises immune phenotypes (e.g. immunosuppressive tumor-associated macrophages) that may help guide immunotherapeutic strategies for NSCLC brain metastases.

Inhibition of colony stimulating factor-1 receptor abrogates microenvironment-mediated therapeutic resistance in gliomas

Glioblastomas represent the most aggressive glioma grade and are associated with a poor patient prognosis. The current standard of care, consisting of surgery, radiation and chemotherapy, only results in a median survival of 14 months, underscoring the importance of developing effective new therapeutic strategies. Among the challenges in treating glioblastomas are primary resistance and the rapid emergence of recurrent disease, which can result from tumor cell-intrinsic mechanisms in addition to tumor microenvironment (TME)-mediated extrinsic resistance. Using a PDGF-B-driven proneural glioma mouse model, we assessed a panel of tyrosine kinase inhibitors with different selectivity profiles. We found that PLX3397, an inhibitor of colony stimulating factor-1 receptor (CSF-1R), blocks glioma progression, markedly suppresses tumor cell proliferation and reduces tumor grade. By contrast, the multi-targeted tyrosine kinase inhibitors dovitinib and vatalanib, which directly target tumor cells, exert minimal anti-tumoral effects in vivo, despite killing glioma cells in vitro, suggesting a TME-mediated resistance mechanism may be involved. Interestingly, PLX3397 interferes with tumor-mediated education of macrophages and consequently restores the sensitivity of glioma cells to tyrosine kinase inhibitors in vivo in preclinical combination trials. Our findings thus demonstrate that microenvironmental alteration by CSF-1R blockade renders tumor cells more susceptible to receptor tyrosine kinase inhibition in a preclinical glioblastoma model, which may have important translational relevance.

Neurotoxic traffic: uncovering the mechanics of amyloid production in Alzheimer's disease

Alzheimer's disease (AD) is thought by many to result from the accumulation of the neurotoxic amyloid-beta (A beta) peptide in brain parenchyma. The process by which A beta is proteolytically derived from the larger amyloid precursor protein (APP) has been the focus of much attention in the AD research field over the past decade. Recently, several of the proteins directly involved in the generation of A beta have been identified and characterized providing a number of viable therapeutic targets for the treatment of AD. However, the cellular mechanisms by which these proteins interact in the proteolytic processing of APP have not been well defined, nor are they readily apparent when one considers what is known about the intracellular localization and trafficking of the various participants. This article will review the underlying cell biology of A beta production and discuss the mechanistic options for APP processing given the current knowledge of the proteases involved.

Maturation and endosomal targeting of beta-site amyloid precursor protein-cleaving enzyme. The Alzheimer's disease beta-secretase

The amyloidogenic Abeta peptide is liberated from the amyloid precursor protein (APP) by two proteolytic activities, beta-secretase and gamma-secretase. Recently, a type I membrane protein termed BACE (beta-site APP cleaving enzyme) with characteristics of an aspartyl protease has been identified as the beta-secretase. We undertook a series of biochemical and morphological investigations designed to characterize the basic properties of this protein. Initial studies indicated that BACE undergoes N-linked glycosylation at three of four potential sites. Metabolic pulse-chase experiments revealed that after core glycosylation, BACE is rapidly and efficiently transported to the Golgi apparatus and distal secretory pathway. BACE was also found to be quite stable, being turned over with a t(12) of approximately 16 h. Retention of BACE in the endoplasmic reticulum by introduction of a C-terminal dilysine motif prevented complex carbohydrate processing and demonstrated that propeptide cleavage occurs after exit from this organelle. BACE exhibited intramolecular disulfide bonding but did not form oligomeric structures by standard SDS-polyacrylamide gel electrophoresis analysis and sedimented as a monomer in sucrose velocity gradients. Immunofluorescence studies showed a largely vesicular staining pattern for BACE that colocalized well with endosomal, but not lysosomal, markers. Measurable levels of BACE were also detected on the plasma membrane by both immunostaining and cell surface biotinylation, and cycling of the protein between the cell membrane and the endosomes was documented. A cytoplasmic dileucine motif was found to be necessary for normal targeting of BACE to the endosomal system and accumulation of the protein in this intracellular site.

Closing in on the amyloid cascade: recent insights into the cell biology of Alzheimer's disease

Accumulation of the amyloid-beta (A beta) peptide in the central nervous system (CNS) is considered by many to be the crucial pathological insult that ultimately leads to the development of Alzheimer's disease (AD). Regulating the production and/or aggregation of A beta could therefore be of considerable benefit to patients afflicted with AD. It has long been known that A beta is derived from the proteolytic processing of the amyloid precursor protein (APP) by two enzymatic activities, beta-secretase and gamma-secretase. Recent breakthroughs have led to the identification of the aspartyl protease BACE (beta-site APP-cleaving enzyme) as beta-secretase and the probable identification of the presenilin proteins as gamma-secretases. This review discusses what is know about BACE and the presenilins, focusing on their capacity as secretases, as well as the options for therapeutic advancement the careful characterization of these proteins will provide. These findings are presented in the context of the "amyloid cascade hypothesis" and its physiological relevance in AD pathogenesis.