Tumor-associated macrophage infiltration in meningioma

Dustin T Proctor; Jordan Huang; Sanju Lama; Abdulrahman Albakr; Guido Van Marle; Garnette R Sutherland

doi:10.1093/noajnl/vdz018

Tumor-associated macrophage infiltration in meningioma

Neurooncol Adv. 2019 Sep 19;1(1):vdz018. doi: 10.1093/noajnl/vdz018. eCollection 2019 May-Dec.

Authors

Dustin T Proctor¹, Jordan Huang^{1

2

3}, Sanju Lama^{1

2

3}, Abdulrahman Albakr^{1

4}, Guido Van Marle⁵, Garnette R Sutherland^{1

2

3}

Affiliations

¹ Project neuroArm, Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
² Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.
³ Arnie Charbonneau Cancer Institute, University of Calgary, Calgary, Alberta, Canada.
⁴ Department of Neurosurgery, King Saud University, Riyadh, Saudi Arabia.
⁵ Department of Microbiology, Immunology and Infectious Diseases, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.

Abstract

Background: Meningioma, a most common brain tumor, has a high rate of recurrence. Tumor-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-tumoral or an immunosuppressive and pro-tumoral microenvironment. TAM subtypes present in meningioma and potential contribution to growth and recurrence is unknown.

Methods: Immunofluorescence staining was used to quantify M1 and M2 TAM populations in tissues obtained from 30 meningioma patients. Associations between M1 and M2 cells, M1:M2 cell ratio to tumor characteristics, WHO grade, recurrence, size, location, peri-tumoral edema, and patient demographics such as age and sex were examined.

Results: TAM cells accounted for ~18% of all cells in meningioma tissues. More than 80% of infiltrating TAMs were found to be of pro-tumoral M2 phenotype and correlated to tumor size (P = .0409). M1:M2 cell ratio was significantly decreased in WHO grade II, compared to grade I tumors (P = .009). Furthermore, a 2.3-fold difference in M1:M2 ratio between primary (0.14) and recurrent (0.06) tumors was observed (n = 18 and 12 respectively, P = .044).

Conclusion: This study is the first to confirm existence of pro-tumoral M2 TAMs in the meningioma microenvironment, emphasizing its potential role in tumor growth and recurrence.

Keywords: M1:M2 TAM ratio; macrophage; meningioma; microenvironment; tumor recurrence.