We have developed a new method for specifically delivering liposomal model drugs to tumor cells. Bispecific monoclonal antibodies (bsMAb) (174H.64 x anti-biotin) which can bind tumor-specific antigen and biotin were developed and characterized. Biotinylated stealth liposome loaded with model drug 99mTc-DTPA can bind to the biotin-binding arm of bsMAb. This targeted liposomal delivery strategy was tested in mouse KLN-205 squamous carcinoma model. bsMAbs were administered 24h in advance into tumor allograft bearing mice, which allow them to bind to tumor cells through the anti-tumor binding arm. After clearance of circulating bsMAb, biotinylated stealth liposomes were introduced to specifically bind to the tumor sites where bsMAb localized earlier. The results show that pretargeted bsMAb can enhance liposomal drug targeting by four times, 3.61% dose/g vs. 0.89% dose/g. This bsMAb/liposome strategy show the broad possibilities of selective delivery of cytotoxic drugs or genes to the specific targets.

The utility of measurement of serum levels of the tumor associated antigens CA 125 and CA 27.29 in detecting the presence of disease and in monitoring changes in disease status was examined in 63 patients with breast cancer. In patients with clinically detectable disease the CA 125 level was elevated in 59%, the CA 27.29 level in 59.5% and one or both markers in 84.6%. Specificity for presence of disease was 83.6% for CA 125, 88% for CA 27.29, and 69.1% for the two markers combined. Changes in marker levels of more than 50% correlated with clinical changes in disease status in 58% of cases for either CA 125 or CA 27.29 alone. In 87.5% of cases with clinically progressive disease one or both marker levels increased by more than 50% from the previous levels. In no case with greater than 50% increase in a marker level was there regression of disease. Thus, the use of these markers in combination might have utility in cases where diagnosis of recurrent disease is difficult or where monitoring of response to treatment is hampered by lack of measurable disease.

Peanut lectin (PNA) binds avidly to oligosaccharides containing the terminal sequence beta-D-Gal(1----3)alpha-D-GAlNAc. This disaccharide is the immunodeterminant group of the Thomsen-Friedenreich (T) antigen which is present in an exposed form on a number of human and animal adenocarcinomas and can be identified in tumor tissue sections by histochemical PNA staining techniques. We have studied the in vivo uptake of radioiodinated PNA in a murine TA3/Ha mammary adenocarcinoma model to evaluate the potential applications of radiolabeled PNA for the immunodetection of T antigen expressing carcinoma. We have found that PNA has a high in vitro binding affinity for the TA3/Ha tumor cells as well as for epiglycanin, a glycoprotein fraction shed by the TA3/Ha cells. Tissue biodistribution studies after IV 125I-PNA injection into TA3/Ha tumor-bearing mice indicated tumor:blood ratios of 7:1 and 55:1 at 24 and 48 h with corresponding tumor:muscle ratios of 33:1 and 77:1. The high tumor uptake and rapid blood clearance allowed clear scintigraphic delineation of tumor by 24 and 48 h without the necessity for background subtraction techniques. Rapid in vivo deiodination of 125I-PNA also contributed to localization of radioactivity in the stomach, salivary glands, thyroid, and kidney.

A panel of 56 MAbs submitted to the ISOBM TD-4 (MUC1) Workshop were analysed in two systems. These systems were designed to screen for peptide type 1 core O-glycan-related reactivities. Using synthetic MUC1 mucin-related peptides and glycopeptides, the panel of MAbs were tested for relative binding affinities to type 1 core O-glycan-substituted MUC1 structures. These studies utilized a competitive binding format with a native human adenocarcinoma-derived mucin as a solid phase. This system allows for analysis of the type 1 core glycoform subspecificity of each MAb. The second approach taken in parallel, utilized MCF-7 (BrCa) and OVCAR (OVCa) cell lines which were grown in the presence or absence of phenyl-N-acetylgalactosaminide (p-gal), a blocker of mucin O-linked glycosylation. These cells were analysed by FACS to examine the role these same glycan substitutions play with regard to either the diagnostic or therapeutic application of these MAbs. By FACS analysis there was a consistent increased ‘epitope exposure’ for peptide-specific MAbs binding in the presence of p-gal. In addition, a single MAb (TD-4 #150) is interpreted to react with a type 1 core O-glycan, probably with Tn, TF or STn specificity.

The role of glycoconjugates in tumor cell differentiation has been well documented. We have examined the expression of the two anomers of the Thomsen-Friedenreich antigen on the surface of human, canine and murine tumor cell membranes both in vitro and in vivo. This has been accomplished through the synthesis of the disaccharide terminal residues in both a and ß configuration. Both entities were used to generate murine monoclonal antibodies which recognized the carbohydrate determinants. The determination of fine specificities of these antibodies was effected by means of cellular uptake, immunohistopathology and immunoscintigraphy. Examination of pathological specimens of human and canine tumor tissue indicated that the expressed antigen was in the β configuration. More than 89% of all human carcinomas tested expressed the antigen in the above anomeric form. The combination of synthetic antigens and monoclonal antibodies raised specifically against them provide us with invaluable tools for the study of tumor marker expression in humans and their respective animal tumor models.