CA125 is expressed on the surface of ovarian carcinoma cells. It is either sloughed or secreted so that significant levels are detected in serum. Serum levels of CA125 correlate with progression or regression of clinical disease and thereby provide a monitoring system for the therapeutic management of these patients. Neither the functional relationship of CA125 to malignancy (if any) or the structure of CA125 have been established. It has been established that CA125 is part of a mucin-like carbohydrate complex and that CA125 is intimately associated with the apocrine secretion process of the endometrium. Recently it has been possible to dissociate the CA125 complex into its component substructure which indicates that CA125 epitopes are present on a 66kD, 97kD and 115kD subunits. It is the objective of this proposal to understand the role (or co-incidental expression) of CA125 in malignancy as well as the biology of the CA125 molecule in normal growth and development. To do so, and to provide the basis for such an understanding it is proposed to structurally analyze the purified subunits of the CA125 molecule and to develop both antibodies and sequence information for use as reagents to clone and characterize the CA125 gene(s).