The extracellular matrix helps to determine cell function, and the cell recognizes the extracellular matrix through receptors known as integrins. There is preliminary data indicating that the highest grade human malignant astrocytoma cells synthesize and secrete the matrix protein osteopontin both in vivo and in vitro. It promotes malignant astrocytoma cell attachment and migration as well as initiating phosphoinositide signaling which appears to be transduced in part through integrin avb3. Phosphoinositide signaling generates second messengers both the from breakdown {Date Released: 05/23/1997 Date Printed: 12/31/1997} of inositol lipids and through phosphorylation by PI 3-kinase. The applicant's data indicate PI 3-kinase activity is necessary for osteopontin-directed cell migration, which is mediated by integrin avb3. It is hypothesized that integrin ligation of osteopontin by malignant astrocytoma cells initiates phosphoinositide signaling that ultimately stimulates cell migration/invasion. As these cells synthesize the stimulant (osteopontin), they participate in the control of their destiny. The objective of this proposal is to understand this matrix-initiated signaling pathway in malignant astrocytoma cells and how it may contribute to tumor cell migration/invasion.
The specific aims are to 1) determine the biologic role of osteopontin in malignant astrocytoma cells by transfecting them with antisense osteopontin cDNA, followed by studies of their in vitro and in vivo proliferation, adhesive and migratory functions, 2) determine the characteristics of osteopontin binding and internalization by malignant astrocytoma cells, and 3) determine whether integrin-mediated osteopontin stimulation of phosphoinositide signaling in malignant astrocytoma cells is controlled by the extracellular matrix and how it may modulate cell adhesion and migration.
