Expression of the hypoxia marker carbonic anhydrase 9 is associated with anaplastic phenotypes in meningiomas.
OBJECTIVE
Hypoxia in the tumor microenvironment triggers a variety of genetic and adaptive responses that regulate tumor growth. Tumor hypoxia is often associated with more malignant phenotypes, resistance to therapy, and poor survival. The purpose of this study was to evaluate the prevalence of hypoxia in meningiomas using the endogenous hypoxia marker carbonic anhydrase 9 (CA9) and to relate the expression of CA9 to tumor vascularity, histopathologic grade, and clinical variables, such as recurrent tumor status.


METHODS
Expression of CA9 and CD34, an endothelial cell marker, was examined in serial paraffin-embedded sections by immunohistochemistry in 25 grade 1, 17 grade 2, and 20 grade 3 meningiomas. Areas of immunoreactivity were semiquantitatively scored and correlated to clinical variables using Statistical Analysis System statistical software.


RESULTS
Approximately 50% (29 of 62) of all meningiomas contained regions of hypoxia as judged by expression of CA9, and this expression was significantly associated with higher-grade histology (P = 0.001). In contrast, vascularity, as assessed by the percentage of vascular hotspots, was inversely associated with tumor grade (P = 0.023) and was not associated with CA9 expression. Among lower-grade meningiomas, CA9 expression tended to be more common in recurrent tumors.


CONCLUSIONS
Tumor hypoxia is an endogenous feature of meningiomas, and therapeutic regimens should include strategies to target the subpopulation of hypoxic as well as the normoxic cells within the tumor. Hypoxia in meningiomas is associated with an aggressive phenotype. Further studies to define the contribution of hypoxia to meningioma pathophysiology are warranted.
Yoo
Heon
H
Brain Tumor Research Center, Department of Neurological Surgery, University of California, San Francisco, California 94143, USA.
Baia
Gilson S
GS
Smith
Justin S
JS
McDermott
Michael W
MW
Bollen
Andrew W
AW
Vandenberg
Scott R
SR
Lamborn
Kathleen R
KR
Lal
Anita
A
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018952:Antigens, CD34 / Q000096:biosynthesis; D000951:Antigens, Neoplasm / Q000096:biosynthesis*; D000970:Antineoplastic Agents / Q000494:pharmacology; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases / Q000096:biosynthesis*; D005260:Female; D006801:Humans; D000860:Hypoxia; D007150:Immunohistochemistry; D008297:Male; D008579:Meningioma / Q000188:drug therapy* / Q000473:pathology*; D008833:Microcirculation; D008875:Middle Aged; D010641:Phenotype; D013997:Time Factors; D016896:Treatment Outcome
D018952:Antigens, CD34; D000951:Antigens, Neoplasm; D000970:Antineoplastic Agents; C089226:CA9 protein, human; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases