A Simplified Approach for the Molecular Classification of Glioblastomas

Glioblastoma (GBM) is the most common malignant primary brain tumors in adults and exhibit striking aggressiveness. Although GBM constitute a single histological entity, they exhibit considerable variability in biological behavior, resulting in significant differences in terms of prognosis and response to treatment. In an attempt to better understand the biology of GBM, many groups have performed high-scale profiling studies based on gene or protein expression. These studies have revealed the existence of several GBM subtypes. Although there remains to be a clear consensus, two to four major subtypes have been identified. Interestingly, these different subtypes are associated with both differential prognoses and responses to therapy. In the present study, we investigated an alternative immunohistochemistry (IHC)-based approach to achieve a molecular classification for GBM. For this purpose, a cohort of 100 surgical GBM samples was retrospectively evaluated by immunohistochemical analysis of EGFR, PDGFRA and p53. The quantitative analysis of these immunostainings allowed us to identify the following two GBM subtypes: the “Classical-like” (CL) subtype, characterized by EGFR-positive and p53- and PDGFRA-negative staining and the “Proneural-like” (PNL) subtype, characterized by p53- and/or PDGFRA-positive staining. This classification represents an independent prognostic factor in terms of overall survival compared to age, extent of resection and adjuvant treatment, with a significantly longer survival associated with the PNL subtype. Moreover, these two GBM subtypes exhibited different responses to chemotherapy. The addition of temozolomide to conventional radiotherapy significantly improved the survival of patients belonging to the CL subtype, but it did not affect the survival of patients belonging to the PNL subtype. We have thus shown that it is possible to differentiate between different clinically relevant subtypes of GBM by using IHC-based profiling, a method that is advantageous in its ease of daily implementation and in large-scale clinical application.     

Contrasting Responses of Saproxylic Insects to Focal Habitat Resources: The Example of Longhorn Beetles and Hoverflies in Belgian Deciduous Forests

Although both saproxylic longhorn beetles and hoverflies benefit from the presence of woody substrates for reproduction, they differ in their requirements for floral resources and for microbiotopes of overmature and senescent trees. This led us to expect contrasting responses between the two species groups in relation to these essential resources. We examined this prediction in 22 mature oak- and beech-dominated stands of southern Belgium by relating their species assemblages to local vegetation structure and composition, altitude and landscape composition. Stands were organised in pairs as a function of their overall dead wood supply. Free-hanging window traps, stump emergence traps and Malaise traps produced 30 longhorn beetle species (1637 individuals) and 106 hoverfly species (3020 individuals). Paired-comparisons controlling for annual variation in captures showed that, unlike saproxylic hoverflies, stands with dead wood hosted more species and individuals of longhorn beetles. Accordingly, the two species groups were found to be independent on ordination axes, responding to different sets of environmental conditions. While stands dominated by oaks with a high snag volume were highly favoured by longhorn beetles, saproxylic and threatened syrphids were limited to open-stands with large trees and a well-developed, species rich herb layer providing the floral resources required for their reproduction. Our results suggest that, when defining criteria to identify or restore important habitats for saproxylic insect conservation, variables related to different aspects of dead wood supply should not be the only criteria taken into account.