Identification of the apoptosis-inducing moiety within urinary preparations of human chorionic gonadotropin (hCG) and identification ot the respective receptor/mechanism in Kaposi´s Sarkoma cells

Kaposi`s sarcomas represent multiple, highly vascularized tumorous lesions that occur mainly in the external skin but also in the mucosae of internal organs such as the gastrointestinal tract. Kaposi`s sarcomas are the most frequent tumors of patients suffering from immunodeficiency, either genetically determined or postnatally aquired (e.g. by immunosuppresssive therapy in organ transplant patients or by HIV infection). Polychemotherapy of such tumors is commonly associated with unwanted serious side effects and therefore an alternative therapy with more selective and less side effects inducing drugs is medically desirable. Such a vision seemed to be realizable from a publication from the laboratory of Robert Gallo (Lunardi-Iskandar et al., 1995) which showed that apoptosis (programmed cell death) could be induced in a Kaposi`s sarcoma cell line in vitro (in culture) as well as in vivo (in a nude mice model) by treatment with certain hCG preparations from the urine of pregnant women. HCG stands for human chorionic gonadotropin, that hormone that is present only in pregnancy. HCG is a complex built glycosylated protein consisting of an alpha and a beta subunit that are non- covalently associated and thus form together the holo-hormone (MW approximately 40.000). Our initial studies (Lang et al, 1997) seemed to support this finding. As a matter of fact we showed that this Kaposi`s sarcoma-apoptosis-inducing activity (KSAIA) could be neutralized by pretreatment with anti-hCG antisera. On the other hand, recombinant pure hCG was inactive, i.e. could not kill Kaposi`s sarcoma cells in vitro, but - of course - was hormonally active, i.e. able to induce testosterone production in an Leydig cell bioassay. This discrepancy let us suggest that the mojety with KSAIA within pregnancy urines or pregnancy urine-derived pharmaceutical hCG preparations is a different mojety rather than hCG itself. This KSAIA substance, however, could be molecularly associated and copurified with hCG and or chemically similar, such as a metabolite of hCG of which a number of different ones are known to be present in urine, such as the isolated subunits or variously deglycosylated forms or various proteolytic fragments of hCG such as the beta core fragment. In every case it has to be considered that the pharmaceutical production of an hCG protein/peptide derivative would be complicated and expensive and that the application to patients would be cumbersome as it would require an intramuscular or intravenous route. Would, however, the KSAIA mojety be an hCG-associated substance (instead of an hCG-like one), would it be conceivable that it could be dissociated from hCG and that it could represent a small molecular non-peptidic substance. Such a type of pharmaceutical substance could conceivably be produced with much less cost and could be applied to patients with better acceptance, such as orally. For this reason we have worked for more than 2 years - using a highly advanced purification and chromatography protocol - to isolated that KSAIA mojety and - using mass spectrometry - to identify its chemical nature. The project was incorporated in 2 Concerted Actions of the European Union entitled "Pathogenesis of AIDS Kaposi`s Sarcoma: Biological, Clinical and Therapeutic Aspects" until 2001 and "Oncogenesis in HIV Infection" until 1999. Within this scientific research context, a number of international cooperations and mutually productive discussions could be established and promise to form a basis for a possible continuation of this project.