ONCOPRECIPITINS - A NOVEL TYPE OF NATURAL SUBSTANCES AND ONCOFETAL ANTIGENS

Immunochemical and physico-chemical properties of two oncofetal antige ns-carcinoembryonic antigen (CEA) and pregnancy-specific beta1-glycopr otein (SP-1, PSbetaG) have been studiEd. The spatial organization of t he protein portion of SP-1 and CEA preparations, as revealed by spectr oscopic evidence, has been discussed with respect to their antigenic a ctivity. We found that the SP-1 and CEA protein portion consists mainl y of a beta-structural type. The antigenic determinants of both prepar ations were shown to be topographic. It seems, that the orientation of the CEA carbohydrate chains relatively to the protein core plays an i mportant role in the formation of the antigenic sites. SP-1 preparatio ns were found to be capable of splitting p-nitrophenylphosphate, gamma -[P-32]-ATP and 4-nitrophenyl-5'-TMP. SP-1 was also shown to effective ly hydrolyse [H-3]-polyuridilic acid and heat-denatured [H-3]-DNA of e mbryos of marine urchin S.intermedius. Enzymic hydrolysis proceeds fro m 3' end of the DNA chain by exonuclease's mechanism. Peculiar glycopr oteins, termed as oncoprecipitins have been found in the extracts of v arious marine invertebrates. The following oncoprecipitins have been i solated and characterized: crustacin from hermit crab Pagurus prideaux ii, cyprein from cowrie Cyprea caputserpentis recognizing CEA and onco precipitin A from ascidian Didemnum ternatum interacting with SP-1. Th e interaction pattern of CEA and its oncoprecipitins is similar to tha t of CEA and its antibody. The possibility of application of CEA oncop recipitins for serologic tumour diagnosis has been demonstrated. The i nteraction between oncoprecipitin A and SP-1 differs from that of SP-1 with its antibodies. The effect, produced by oncoprecipitin A on HeLa -M and A-431 tumour cells causes the essential alteration of their cyt oskeleton. The incubation of HeLa cells with oncoprecipitin A, followe d by SP-1 leads to a recurrent state of their cytoskeleton. The possib le role of oncoprecipitins as substances able to monitor the appearanc e and elimination of neoplastic cells of invertebrates will be discuss ed.