Abstract: The present invention comprises novel recombinant DNA compounds which encode the .about.40,000 dalton adenocarcinoma antigen recognized by monoclonal antibody KS 1/4. Eukaryotic and prokaryotic expression vectors have been constructed that comprise novel KSA-encoding DNA and drive expression of KSA when transformed into an appropriate host cell. The novel expression vectors can be used to produce KSA derivatives, such as non-glycosylated KSA, and to produce KSA precursors, such as nascent KSA, and to produce subfragments of KSA. The recombinant-produced KSA is useful for the diagnosis, prognosis and treatment of disease states including adenocarcinomas of the lung, prostate, breast, ovary and colon/rectum; and for the creation of novel antibodies for treatment or diagnosis of the above.