Background & objective: Usually pituitary adenomas are histological benign and grow slowly, but a proportion of them will become locally aggressive, and develop into invasive pituitary adenomas. The reasons for these differences in tumor behavior are poorly understood. Pituitary adenomas are abounding blood vessels. Angiogenesis and tumor invasion both require degradation of the extracellular matrix components to allow cell migration. The matrix metalloproteinases (MMPs) and their nature inhibitors-the tissue inhibitors of metalloproteinases (TIMPs) may play a central role in these processes. The aggressive mechanism of pituitary adenomas was studied through investigating the expression of MMP-9, MMP-2, TIMP-1, and TIMP-2 in both invasive and non-invasive adenomas.
Methods: Sixty-one surgical removed pituitary adenomas (forty-nine cases invasive and twelve non-invasive adenomas) were investigated. Immunohistochemistry staining (SP method) was used to detect the expression of MMP-9, MMP-2, TIMP-1, and TIMP-2 in two groups. The results were treated with semi-quantitative method and analyzed by using non-parameter rank sum test.
Results: Immunohistochemical staining of tumor cells for MMP-9, TIMP-1, MMP-2, and TIMP-2 were noted 95.9% (47/49), 57.1% (28/49), 75.5% (37/49) and 89.8% (44/49) in invasive adenomas, and 100% (12/12), 91.7% (11/12), 66.7% (8/12), and 91.7% (11/12) in non-invasive adenomas, respectively. Invasive tumors were significantly less expressing TIMP-1 and TIMP-2 (P < 0.05). There was no significant difference for MMP-9 or MMP-2 between invasive and non-invasive groups (P > 0.05).
Conclusions: TIMP-1 and TIMP-2 may play a key role in invasive pituitary adenomas to biological behavior.