Abstract
Abstract
BACKGROUND
Meningioma, a most common brain tumour, has a high rate of recurrence. Tumour-associated macrophages (TAMs) are the most abundant immune cell type in meningioma. TAMs display functional phenotypic diversity and may establish either an inflammatory and anti-tumoural or an immunosuppressive and pro-tumoural microenvironment. TAM subtypes present in meningioma and potential contribution to growth and recurrence is unknown.
METHODS
Fluorescence immunohistochemistry was used to evaluate the distribution and quantify M1 and M2 TAM populations in 30 meningioma tissues. Association between quantified M1 and M2 cells and M1/M2 ratio to tumour characteristics including WHO grade, tumour recurrence, size, location, peri-tumoural edema and patient demographics such as age and sex was examined.
RESULTS
TAM cells accounted for ~17% of all cells in tumour tissues. Importantly, greater than 80% of infiltrating TAMs were discovered to be of a polarized pro-tumoural M2 phenotype which positively associated with tumour size. TAM subtype profiles differed significantly between non-recurrent (n=18) and recurrent meningioma (n=12) (P=0.044). Specifically, the M1/M2 cell ratio was decreased by ~250% in recurrent tumours.
CONCLUSION
This study is the first to confirm existence of pro-tumoural M2 TAMs in the meningioma microenvironment and a potential role in tumour growth and recurrence.