Nonimmune Fluorescent Protein Staining of Neoplasms

In 1952 Weiler demonstrated with ultraviolet microscopy that anti-rat liver microsomal and mitochondrial rabbit globulin conjugated with fluorescein isocyanate became selectively attached to normal and hyperplastic rat liver but not to paradimethylamino-azobenzol-induced hepato-carcinoma within such livers. In 1956 he demonstrated similar antigenic differences between normal hamster kidney and stilbesterol-induced renal carcinoma in such kidneys by microscopic localization of fluorescing antibodies (Weiler, 1956a) and by complement fixation tests (Weiler, 1956b). In addition he noted that there was slight nonspecific staining of malignant tumors by unabsorbed fluorescent tagged antibodies. He found that it was not necessary to absorb the antibody fluorescein conjugate to prevent the usual nonspecific staining of malignant neoplasms as it was in normal tissues (Weiler, 1956a). Subsequently, Hughes et al. (1957), Louis (1957c), and King et ~2. (1958) showed that there is a nonimmunospecific selective binding of certain fluorochrome protein conjugates by normal, hyperplastic tissues and benign tumors which is not observed in malignant tissues. They showed a similar selective binding with different fractions of serum tagged with either fluorescein isocyanate or rhodamine isocyanate. They used gamma, beta, and alpha globulin, and albumin from different species, as well as ovalbumin upon homologous and heterologous normal, benign tumorous and malignant epithelial tissues. They consistently produced a distinguishable difference between benign and malignant tissues (Hughes and Louis 1959; King et al., 1958, 1959). The benign tissues bound the conjugated protein whereas the malignant tissues failed to do so; such a selective binding was found to exist in all of a large number of human malignant epithelial neoplasms from different organs (Hughes, 1958a; Louis, 1957a, d, 1958a-d, 1960a, b, 1961; Louis and Varasdi, 1960). Immune and nonimmune conjugated sera produced similar results without distinguishable difference between them (Hughes et al., 1957); extraction of such protein conjugates with powdered liver or bone marrow eliminated the nonspecific binding without adversely affecting immunospecific binding (King et al., 1959). In addition, experimentally induced carcinomas lost the ability to bind fluorochrome-bound proteins as they became malignant (Hughes, 1958b; Louis, 1957c), and epithelia which were cultured in vitro gradually lost such a binding ability (Louis and White, 1960). Benign and malignant supporting tissues and neural tissue did not bind fluorochrome