Daunomycin was covalently attached via a dextran bridge to specific antibodies against rat a-fetoprotein produced in a horse. The effect of this conjugate on an ei-fetoproteinproducing tumor was investigated in terms of cytotoxicity and inhibition or retardation of tumor development. Under the experimental conditions used, the covalent conjugate was by both criteria more efficient than either daunomycin alone or a mixture of daunomycin and specific antibodies or a conjugate ofdaunomycin with horse immunoglobulin. These results show that the conjugate may be useful as a specific cytotoxic agent against at-fetoprotein-producing tumors.The cytotoxic activity of a specific antiserum to a-fetoprotein (AFP) on AFP-producing tumors was determined both in vitro (1, 2, t) and in vivo (3, 4). The observation that tumor cells that produce very low levels of AFP are able to survive selectively on treatment with the antiserum in vitro (5) suggests that the cytotoxic activity of the antiserum may depend on the level of AFP production by the tumor cells. Recent studies (1, 6, 7) have shown that AFP is detectable on the cell surface of AFP-producing tumor cells and suggest that the binding of antibody to AFP may have a fundamental role in its cytotoxic effect on such cells.Daunomycin (8, 9) is a well-known antitumor drug, widely used in cancer therapy. The major drawback, however, is that daunomycin, like many other drugs effective in killing tumor cells, also has detrimental effects on rapidly proliferating normal cells. This toxicity, which limits the effective use of chemotherapy in treatment of neoplastic diseases, may perhaps be overcome or reduced by binding the drug to a carrier that has specific affinity to the tumor cells (10,11). In previous studies, we have tested the effects of daunomycin-antitumor immunoglobulin conjugates on various tumors (12). These conjugates retained most of their original drug and antibody activities (13,14). Conjugates with specific antibodies were more effective than drug conjugates with normal immunoglobulin and, under certain conditions, were an improvement over the free drug (15).The aim ofthis study was to test specific antibodies produced in a horse against rat AFP as carriers of daunomycin. Daunomycin-anti-AFP conjugates were tested for their effect on rat hepatoma and compared with free daunomycin, anti-AFP, and a mixture of anti-AFP and daunomycin linked to normal horse immunoglobulin. A preliminary report ofthese studies has been presented. § A report describing the in vitro effect of daunomycin attached by a direct linkage to anti-mouse a-fetoprotein has also appeared (16). MATERIALS AND METHODSSpecific Antibodies to AFP. Specific antiserum to rat AFP was produced in a horse by weekly subcutaneous injections of 1 mg of purified AFP (17) emulsified in Freund's complete adjuvant. Specific antibodies to rat AFP were purified by affinity chromatography on activated Sepharose 4B coupled to rat AFP (18). (Fab')2 fragment from the specific antibody was prepared by pepsin digesti...

Peroxidase-conjugated lectins (peanut agglutinin: PNA; Ricinus communis agglutinin: RCA) were used for histochemical demonstration of the respective carbohydrate binders (PNA: beta-D-galactosyl-(1-3)-N-acetyl-galactosamine; RCA: D-galactose). The study of prostatic specimens from four different age groups showed marked differences in cytoplasmic PNA binding of prostatic epithelium. The basal cells of the glandular epithelium displayed cytoplasmic PNA binding only in the infantile stage and during early puberty. With the onset of puberty a number increasing with age of secretory cells developed cytoplasmic binding of PNA, mostly appearing as apically located vacuoles. Intraluminal secretion, however, was never stained. During senile involution the prostatic epithelium lost rapidly its PNA binding capacity. Since no RCA binding of the epithelium was observed, the carbohydrate moiety responsible for PNA binding presumably represents a galactosyl-N-actyl-galactosamine containing molecule, most likely a glycoprotein, which is present in actively functioning prostatic epithelial cells. It is uncertain whether or not it represents a structural or a secretory component of the prostatic cell.

Acid phosphatase was purified from human prostatic tissue and from seminal plasma. Antisera to antigens from both sources were raised in rabbits. These antisera have been used for immunohistochemical localization of the respective antigens in the prostates of neonatal, infantile, prepubertal, and adult individuals. Immunoreactivity of the prostatic epithelium with the seminal fluid-derived antigen developed progressively in pubertal specimens with increasing age. It was not present in fetal and infantile organs. Antiserum prepared from human prostatic tissue-derived acid phosphatase gave a positive immunoreaction both with stroma and epithelium of the pre- and postpubertal glands. The results give evidence for a clear cut androgen-dependence in the appearance of the acid phosphatase present in semen, which therefore has been identified as secretory. The second antigen is nonsecretory, tissue-bound, nonandrogen dependent, and shares antigenic determinants with leukocyte-derived acid phosphatase.

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