Integration of epidemiology, immunobiology, and translational research for brain tumors

Abstract

We recently identified a pivotal role for the host type I interferon (IFN) pathway in immunosurveillance against de novo mouse glioma development, especially through the regulation of immature myeloid cells (IMCs) in the glioma microenvironment. The present paper summarizes our published work in a number of areas. We have identified single-nucleotide polymorphisms (SNPs) in human IFN genes that dictate altered prognosis of patients with glioma. One of these SNPs (rs12553612) is located in the promoter of IFNA8 and influences its activity. Conversely, recent epidemiologic data show that chronic use of nonsteroidal anti-inflammatory drugs lowers the risk of glioma. We translated these findings back to our de novo glioma model and found that cyclooxygenase-2 inhibition enhances antiglioma immunosurveillance by reducing glioma-associated IMCs. Taken together, these findings suggest that alterations in myeloid cell function condition the brain for glioma development. Finally, in preliminary work, we have begun applying novel immunotherapeutic approaches to patients with low-grade glioma with the aim of preventing malignant transformation. Future research will hopefully better integrate epidemiological, immunobiological, and translational techniques to develop novel, preventive approaches for malignant gliomas.

Figure 1

Effects of IFN-α gene alterations on glioma development in mice and humans. (A, B), Gliomas were induced in C57BL/6 background Ifnar1^−/− (red lines) or wild-type (WT; black lines) neonatal mice by intraventricular transfection of plasmids: pT2/C-Luc//PGK-SB1.a3 (0.2 µg), pT/CAG-NRas (0.4 µg), and pT/shp53 (0.4 µg). (A) Tumor growth was monitored. (B) The mice bearing SB-induced tumors were sacrificed at days 50–60, and brain infiltrating leukocytes (BILs) were isolated based on similar tumor size observed by bioluminescence imaging (BLI). BILs obtained from three mice in a given group were pooled and evaluated by flow cytometry for CD11b⁺Ly6G⁺ IMCs. Absolute IMC numbers in three independent experiments are depicted in the bottom panels. P values are based on Student's t-test. (C) Overall survival was evaluated among 291 glioma patients with WHO grade 2–3 gliomas by genotype for SNPs in IFNA8 rs12553612. Patients with AC genotype (red line) exhibited a significantly shorter survival than those with the AA genotype (black line). Reproduced, with permission, from Fujita et al.

Figure 2

Interferon (IFN)-A8 promoter activity with the A-genotype at −335 is superior to that with the C-genotype. (A) THP-1 cells (1×10⁵) were co-transfected with 0.02 µg of pGL4 vector encoding Renilla luciferase (Rluc) as internal control and 0.18 µg of pGL4 vector encoding Firefly luciferase downstream of IFNA8 promoter with A- or C-genotype (A-Fluc and C-Fluc). Twenty-four hours after the co-transfection, luc activity was measured from triplicate cell-lysates, and relative luciferase was calculated (Fluc/Rluc). (B) THP-1 cells were transfected with the A-genotype Fluc-reporter plasmid and the internal control Rluc plasmid as well as an expression plasmid encoding ELK-1, OCT-1, or IRF-7 as a positive control. Relative luciferase was calculated as Fluc/Rluc. Results are from one of two experiments with similar results. *Indicates that the values were statistically different (P < 0.05) from the control samples with the empty vector by unpaired two-tailed Student’s t-test. Error bars indicate standard deviation among triplicate sample. OCT-1 transfection did not enhance the activity of the C-genotype Fluc-reporter (shown in the full paper). (C) Schematic demonstrating the OCT-1 binding ability to the IFNA8 promoter region containing the rs12553612 SNP. Reproduced, with permission, from Kohanbash et al.