Immunotargeting of daunomycin to localized and metastatic human colon adenocarcinoma in athymic mice

Abstract

A monoclonal antibody (designated SF25), which recognizes a protein antigen expressed on a large number of human colon carcinomas, was used for drug targeting. Daunomycin-antibody conjugates were prepared by two previously described procedures. In one, the drug was bound to the antibody through a spacer of small molecular mass (cis-aconitic acid), while in the other a dextran bridge served as the link between drug and antibody. High substitution rates of drug to antibody were obtained using the latter binding procedure. Both conjugates were tested in vitro against two human colon carcinoma cell lines, LS180 and KM-12. The efficacy of a daunomycin-dextran-SF25 antibody conjugate was tested against colon carcinoma LS180 tumors transplanted at different sites into athymic mice. The specific conjugate was significantly more inhibitory to a subcutaneous tumor growth than its components or their mixture. SF25 antibody alone showed antitumoral effects against all three forms of transplanted tumor tested, namely, local, metastatic or intrahepatic, whereas daunomycin, on its own, was effective only against the subcutaneous tumor. Binding of daunomycin to dextran partially improved its inhibitory activity against the metastatic tumor. The conjugate, daunomycin-dextran-SF25 antibody reduced the number of metastatic foci, increased the survival rate and delayed death. Yet against lymph node metastases it was not significantly better than a mixture of both constituents. However, results obtained with an intrahepatic tumor, a model that mimics the natural progression of the disease, resembled those described with the subcutaneous tumor. Daunomycin-dextran-SF25 antibody was significantly more effective than all components separately and than a mixture of drug and antibody, provided a highly drug-substituted conjugate was used.

Separable Regulatory Elements Governing myogenin Transcription in Mouse Embryogenesis

“…DNA for microinjection was purified by two cycles of CsCI centrifugation and then linearized by Hind Ill and Eco RI digestion, and the fragments were isolated from a SeaPlague agarose gel (FMC, Rockland, ME) and passed through NACS columns (BRL, Gaithersburg, MD). Microinjections and transfer of fertilized eggs were performed as described (28). (C57BL6 x CBA)F1 mice (Jack-son Laboratory, Bar Harbor, ME) were used as stud males, embryo donors, and mature females for breeding.…”

Prodrugs of Anthracyclines in Cancer Chemotherapy

“…In a study by Hurwitz et al [135] the mAb SF25, which is specific for an antigen expressed by a large number of human colon carcinoma, was coupled to daunorubicin through a cis-aconityl linker or through a dextran linker. The mAb SF25-dextran-DNR conjugate showed superior cytotoxicity against two human colon cell lines (LS180 and KM-12) compared to free mAb SF25, daunorubicin and to the mAb SF25-cis-aconityl-DNR conjugate.…”

Tumor Specific Novel Taxoid-Monoclonal Antibody Conjugates

“…These mAb-drug conjugates displayed impaired affinity in vitro, and unfavorable pharmacokinetics in animals. Cleavable linkers, such as tetrapeptide spacer [19,20], cis-aconitic [21][22][23], hydrazide [24], thiocarbamoyl [25] have been used to conjugate cytotoxic drugs to antibodies. Although these "first generation mAb-drug conjugates" showed some impressive activity in animal models, they all failed in the human clinical trials.…”