Effect of a conjugate of daunomycin and antibodies to rat alpha-fetoprotein on the growth of alpha-fetoprotein-producing tumor cells.

Abstract

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...

Chemotherapeutic efficacy of the protein-doxorubicin conjugates on multidrug resistant rat hepatoma cell line in vitro

“…Examples of this include the immunoconjugates of IgG antibody against alpha-fetoprotein with anticancer drugs (Tsukada et al, 1982;Kato et al, 1983;Tsukada et al, 1984;Ohkawa et al, 1986). Further investigations in vitro are planned to elucidate the exact mechanism(s) via which conjugates are able to overcome the multidrug resistance.…”

Application of boronated anti-CEA immunoliposome to tumour cell growth inhibition in in vitro boron neutron capture therapy model

“…However, a heavy boronation of antibody has been shown to markedly reduce the antibody reactivity (Alam et al, 1985;Takahashi et al, 1987) and the numbers of epitope on the tumour cell surface have been estimated to be at most 106/cell (Tsukada et al, 1982;Barth et al, 1990). These results indicate that monoclonal antibody directly conjugated with '0B-compound has limited application in BNCT.…”

Suppression of human α-foetoprotein-producing hepatocellular carcinoma growth in nude mice by an anti α-foetoprotein antibody-daunorubicin conjugate with a poly-L-glutamic acid derivative as intermediate drug carrier

“…Recently, the targeting chemotherapy by polyclonal or monoclonal antibodies to tumour-associated antigens has been extensively studied (Latif et al, 1980;Embleton et al, 1981;Bernhard et al, 1983;Garnett et al, 1983). Similar approaches have been made utilizing purified antibody to rat AFP and anticancer drugs such as daunorubicin (DM) and mitomycin C (MMC) (Tsukada et al, 1982a;1982b;. Recently our-laboratory (Kato et al, 1983) developed a new method of conjugation of DM with antibody with a single thiol group-bearing PLGA derivative as intermediate drug carrier and the anti-rat AFP antibody-PLGA-DM conjugate prepared by this method showed a potent antitumour activity against the AFP-producing ascites hepatocellular carcinoma cells AH66 growing in DONRYU rats .…”

“…The maintenance of low AFP level in the group of mice treated with aAFP, aAFP plus DM, and aAFP plus PLGA-DM was probably caused by two factors viz. the selective decrease of AFP highproducing tumour cells and of remaining antibody to AFP (Tsukada et al, 1974b;1982a) (Figure 2 Time (d) Figure 1 Therapeutic activity of anti-human AFP-PLGA-DM. Li-7 cells, 1-1.5 x 106 were transplanted into nude mice on day 0. aAFP-PLGA-DM (aAFP 142 g, DM 10kg mouse/injection) and other test materials were administered i.p.…”

“…Recently, in order to increase the cytotoxic effect of anti-AFP antibody on the tumour target cells, we have successfully developed specific targeting chemotherapy using anti-AFP antibody with which daunorubicin (DM) was conjugated via periodateoxidized dextran (Tsukada et al, 1982a(Tsukada et al, , 1982b.…”