Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Osteopontin (OPN) is an integrin-binding cell adhesion protein, that is expressed in many normal cells and tissues, and that is associated with a number of pathological conditions, including cancer. The work presented in this thesis addresses both structural studies of the opn gene, and functional studies of the OPN protein, in an attempt to improve our understanding of OPN.;Two conflicting gene structures of the mouse opn gene had been reported that put into question the location of the promoter, the transcriptional start site, and exon 1 of the mouse opn gene. Analysis of the expressed messages predicted by the two reported gene structures has established the correct gene structure of mouse opn. Furthermore, this analysis has established that the opn transcript (mRNA) is similar in mouse fibroblasts, mouse epithelial cells, and mouse macrophages, an important observation since the conflicting opn gene structures were derived from epithelial and macrophage cells.;The functional role of OPN in any of the physiological or pathological contexts in which OPN is found, is still unknown. Frequently, OPN has been associated with conditions of transformation, including being over-produced by ras-transformed NIH 3T3 cells. Analysis of the levels of opn mRNA and OPN protein produced in a series of ras-transformed NIH 3T3 cells has demonstrated that opn mRNA and OPN protein levels correlate with the levels of ras expression and with the metastatic potential of the cells. This finding raised the possibility of an active role for OPN in the development of a malignancy.;To determine whether OPN contributes functionally to the malignant properties of tumor cells, antisense opn RNA was expressed in metastatic, ras-transformed NIH 3T3 cells. Two independent clones that expressed antisense opn RNA in vitro were significantly reduced in their ability to form primary tumors and metastases in vivo. Primary tumors did arise only after expression of antisense opn RNA was lost from the tumor cells, independently in five individual mice. These results are consistent with a functional role for OPN in malignancy, and are the first to show expression of antisense opn RNA associated with decreased malignancy.



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