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Although mesenchymal stem cells (MSCs) have been implicated as stromal components of several cancers, their ultimate contribution to tumorigenesis and their potential to drive cancer stem cells, particularly in the unique microenvironment of human brain tumors, remains largely undefined. Consequently, using established criteria, we isolated glioma-associated-human MSCs (GA-hMSCs) from fresh human glioma surgical specimens for the first time. We show that these GA-hMSCs are nontumorigenic stromal cells that are phenotypically similar to prototypical bone marrow-MSCs. Low-passage genomic sequencing analyses comparing GA-hMSCs with matched tumor-initiating glioma stem cells (GSCs) suggest that most GA-hMSCs (60%) are normal cells recruited to the tumor (Group 1 GA-hMSCs), although, rarely (10%), GA-hMSCs may differentiate directly from GSCs (Group 2 GA-hMSCs) or display genetic patterns intermediate between these groups (Group 3 GA-hMSCs). Importantly, GA-hMSCs increase proliferation and self-renewal of GSCs in vitro, and enhance GSC tumorigenicity and mesenchymal features in vivo, confirming their functional significance within the GSC niche. These effects are mediated by GA-hMSC-secreted interleukin-6, which activates STAT3 in GSCs. Our results establish GA-hMSCs as a potentially new stromal component of gliomas that drives the aggressiveness of GSCs, and point to GA-hMSCs as a novel therapeutic target within gliomas.

AbstractΔ24-RGD is an infectivity-augmented, conditionally replicative oncolytic adenovirus with significant antiglioma effects. Although intratumoral delivery of Δ24-RGD may be effective, intravascular delivery would improve successful application in humans. Due to their tumor tropic properties, we hypothesized that human mesenchymal stem cells (hMSC) could be harnessed as intravascular delivery vehicles of Δ24-RGD to human gliomas. To assess cellular events, green fluorescent protein-labeled hMSCs carrying Δ24-RGD (hMSC-Δ24) were injected into the carotid artery of mice harboring orthotopic U87MG or U251-V121 xenografts and brain sections were analyzed by immunofluorescence for green fluorescent protein and viral proteins (E1A and hexon) at increasing times. hMSC-Δ24 selectively localized to glioma xenografts and released Δ24-RGD, which subsequently infected glioma cells. To determine efficacy, mice were implanted with luciferaselabeled glioma xenografts, treated with hMSC-Δ24 or controls, and imaged weekly by bioluminescence imaging. Analysis of tumor size by bioluminescence imaging showed inhibition of glioma growth and eradication of tumors in hMSC-Δ24-treated animals compared with controls (P < 0.0001). There was an increase in median survival from 42 days in controls to 75.5 days in hMSC-Δ24-treated animals (P < 0.0001) and an increase in survival beyond 80 days from 0% to 37.5%, respectively. We conclude that intra-arterially delivered hMSC-Δ24 selectively localize to human gliomas and are capable of delivering and releasing Δ24-RGD into the tumor, resulting in improved survival and tumor eradication in subsets of mice.

The prognostic impact of TERT mutations has been controversial in IDH-wild tumors, particularly in glioblastomas (GBM). The controversy may be attributable to presence of potential confounding factors such as MGMT methylation status or patients’ treatment. This study aimed to evaluate the impact of TERT status on patient outcome in association with various factors in a large series of adult diffuse gliomas. We analyzed a total of 951 adult diffuse gliomas from two cohorts (Cohort 1, n = 758; Cohort 2, n = 193) for IDH1/2, 1p/19q, and TERT promoter status. The combined IDH/TERT classification divided Cohort 1 into four molecular groups with distinct outcomes. The overall survival (OS) was the shortest in IDH wild-type/TERT mutated groups, which mostly consisted of GBMs (P < 0.0001). To investigate the association between TERT mutations and MGMT methylation on survival of patients with GBM, samples from a combined cohort of 453 IDH-wild-type GBM cases treated with radiation and temozolomide were analyzed. A multivariate Cox regression model revealed that the interaction between TERT and MGMT was significant for OS (P = 0.0064). Compared with TERT mutant-MGMT unmethylated GBMs, the hazard ratio (HR) for OS incorporating the interaction was the lowest in the TERT mutant-MGMT methylated GBM (HR, 0.266), followed by the TERT wild-type-MGMT methylated (HR, 0.317) and the TERT wild-type-MGMT unmethylated GBMs (HR, 0.542). Thus, patients with TERT mutant-MGMT unmethylated GBM have the poorest prognosis. Our findings suggest that a combination of IDH, TERT, and MGMT refines the classification of grade II-IV diffuse gliomas.Electronic supplementary materialThe online version of this article (doi:10.1186/s40478-016-0351-2) contains supplementary material, which is available to authorized users.