Increased Tissue Stiffness in Tumors from Mice with Neurofibromatosis-1 Optic Glioma.

Children with neurofibromatosis type 1 (NF1) cancer predisposition syndrome are prone to the development of low-grade brain tumors (gliomas) within the optic pathway (optic gliomas). One of the key obstacles to developing successful therapeutic strategies for these tumors is the striking lack of information about the mechanical properties that characterize these tumors relative to non-neoplastic optic nerve tissue. To study the physical changes that may occur when an optic nerve glioma is present, we employed atomic force microscopy to measure the stiffness of healthy versus tumor-bearing optic nerve tissue. We found that the average elastic moduli of non-neoplastic and tumor-bearing optic nerves were ∼3 and ∼6 kPa, respectively. Based on previous studies implicating changes in extracellular matrix remodeling in other, related optic nerve pathological states, we found decreased expression of one major metalloproteinase protein (MMP-2) and unchanged expression of lysyl oxidase and a second metalloproteinase, MMP-9, in murine optic gliomas relative to normal non-neoplastic optic nerve. Collectively, these observations suggest a productive interplay between physical properties of mouse optic nerve gliomas and the extracellular matrix.