Immunohistochemical localization of a choriogonadotropin-like protein in bacteria isolated from cancer patients.

By the use of specific antibody to human chorionic gonadotropin (CG) as well as to its beta-subunit, and the application of the indirect fluorescein-labeled and peroxidase-labeled antibody techniques, we have demonstrated the presence of a membrane (wall)-associated CG-similar immunoreactive protein in 15 strains of bacteria isolated from tissues of patients bearing malignant neoplasms. These microorganisms were classified as S. epidermidis, (12) E. coli (2), and a single strain of P. maltophilia (ATCC 13637). The absence of the CG-like antigen in other "cancer associated bacteria", Streptococcus faecalis (ATCC 12818) and Pseudomonas aeruginosa (from patient with cancer of colon), demonstrated that not every "cancer associated bacteria" has the capability to synthesize the trophoblastic-like protein. The negative results obtained with a number of "noncancer control" bacteria of known origin, obtained from ATCC and from clinical samples, strongly supported the idea that the existance of these CG-like protein producing microorganisms is not a ubiquitous finding. The demonstration of a de novo bacterial biosynthesis of a protein having similar antigenic and biophysical properties to those of the human trophoblastic hormone, has great biological implications, especially if its biosynthesis is proven only in bacterial strains growing in the presence of cancer cells in which we have already demonstrated the presence of a similar antigen. The explanation of the phenomenon is unknown. Because of their origin, the potential of "genetic exchange" with subsequent expression of the mammalian gene by the bacterial cells becomes a possibility. It is also possible that the gene coding for the CG-like protein is normally present but inactive or repressed in all bacteria.