In our exploratory study of risk of adult meningioma with common tagging SNPs in 148 innate immune genes and their surrounding regions, we identified seven genetic regions of particular interest within four innate immune pathways: TNFSRF18, FCER1G and VCAM1 (integrins/cell surface receptors), NFKB1 and CD14 (pattern recognition and antimicrobials), C1D (complement) and CCR6 (chemokines).
The gene regions for
NFKB1 and
FCER1G were particularly intriguing given the relationship between T-cell regulation and chronic inflammation (
NFKB1), and IgE and allergic reactions (
FCER1G). Three statistically significant SNPs were observed in each of these regions at the p<0.01 level.
NFKB1 encodes the subunit p50/p105 for a pleiotropic transcription regulator activated by a variety of intra- and extra-cellular stimuli. The transcription inhibitor is part of the DNA-binding subunit of the NFKB protein complex involved with T cell regulation and chronic inflammation (
15). Epidemiologic studies have observed associations between
NFKB1 polymorphisms and risk of some cancers, including glioma, non-Hodgkin lymphoma and Hodgkin’s lymphoma (
5,
16–
17), and inflammatory diseases (
18), but not for other cancers such as breast, colorectal, or renal cell cancers (
19–
20). The
NFKB pathway has also been associated with inflammatory conditions in the brain, such as Alzheimer’s disease (
7–
8). Less is known about
FCER1G and its relevance to the etiology of meningiomas. The
FCER1G is a subunit of the high-affinity IgE receptor mediating allergic reactions. Functional polymorphisms in
FCER1A, which also codes for a subunit of the IgE receptor, were strongly associated with serum IgE levels in a genome-wide association study (
21).
Several additional SNPs of interest lay within gene regions coding for integrin/cell surface receptors, including
TNFSRF18, FCER1G and
VCAM1. This pathway is of particular interest given that changes in integrin pattern expression have been observed in a variety of meningiomas (
9–
10) and may influence their invasive biological behavior.
The few existing studies of common genetic variation and risk of meningioma have reported statistically significant associations in genes in the DNA repair, apoptosis/cell cycle, IGF, folate metabolism, p53, and oxidative response pathways (
22). To our knowledge, this is the first study of meningioma to explore a large number of genetic variants in the innate immunity pathway. Comparing our results for innate immunity genes and risk of meningioma with a previous examination of the same SNPs for glioma risk (
5), we found that among the top ten hits,
NFKB1 was significant in both studies (p<0.01). However, gene region-based hits (p<0.05) differed between glioma (
ALOX5,
SELP and
SOD) and meningioma (
TNFSRF18,
FCER1G,
VCAM1,
NFKB1,
CD14,
C1D, and
CCR6).
Although our results provide interesting clues, they are subject to some caveats. While the hospital-based design of this study allowed accrual of incident meningiomas, and we imposed strict quality control criteria for blood collection and genotyping of DNA samples, the sample size for this study remains small. The SNPs in this study were chosen as tagging markers for the genetic region and not based on known function, thus the observed associations could be due to linkage disequilibrium with the true unobserved causal SNPs. Replication of these findings with increased coverage of the identified genes of interest and larger sample size (for example, in multicenter studies of meningioma) is required to rule out the possibility of chance findings.