Gd-25 DTPA-MAb, a potential NMR contrast agent for MRI in the xenografted nude mouse: Preliminary studies

Abstract

The use of paramagnetic agents to enhance contrast in magnetic resonance imaging (MRI) may extend its diagnostic potential. The most promising ion so far investigated is gadolinium chelated with diethylenetriamine penta-acetic acid (DTPA), a compound that produces a marked reduction in TI and TZ proton relaxation in vitro and in vivo (Wolf, 1984; Weinmann, 1984;. One approach for increasing the specificity of nuclear magnetic resonance (NMR) image contrast is to couple gadolinium-DTPA (Gd-DTPA) to a MAb.We have shown (Curtet, 1986) that it is possible to couple MAb to gadolinium using the cyclic anhydride method (Hnatowich, 1981). We demonstrated that TI NMR relaxation of water protons decreased significantly (by 15 %) with MAb 19-9, which recognizes human colon adenocarcinoma, after i.v. infusion (Gd 0.008 mmole/kg, 15 DTPA/ MAb). However, these results did not lead to sufficient contrast in MRI.In the present work, we used several approaches to enhance the signal, increase gadolinium concentration in the tumour (15, 25, 50 DTPA/MAb) and select a GA 73-3 MAb with a higher affinity for a greater number of antigen sites per tumour cell. MATERIAL AND METHODS Mouse MAbMurine MAb 19-9 and GA 73-3, specific for human GI tract adenocarcinomas, were provided by Dr. H. Koprowski, Philadelphia, PA. Antibody 19-9 (Koprowslu, 1979), detects a mono-sialoganglioside antigen (Magnani, 1981). Antibody GA 73-3 recognizes lo6 sites per cell in the same CRC lines (Herlyn, 1984). Tumour modelSW948 human CRC lines were obtained from Dr. A. Leibowitz, Scott and White Clinic (Temple, TX) and control Foss human melanoma and MDA human breast cancer from the Cancer Task Force Cell Culture Bank, NCI, Bethesda, MD. The cells were injected subcutaneously in the right flank of 8 to 10 week-old nude mice. Twelve to 15 days after tumour transplantation, when tumour diameter was 8 to 15 mm, the contrast agent conjugate was injected via a tail vein. Gd-DTPA-MAb preparationThe method has been described previously (Curtet, 1986). Briefly, MAbs 19-9 and GA 73-3 were covalently bound to the DTPA chelating agent. Mole ratios of cDTPA (cyclic anhydride of DTPA) of 5, 50, 100 and 150 were used; and 2 , 15, 25 and 50 DTPA molecules, respectively, were conjugated to MAbs. Aggregate formation was eliminated by gel fitration through a Sephadex G200 column. The number of DTPA molecules conjugated was determined by using a titration method based on competition between InC13 and radioactive carrier-free 1111nC13. Finally, GdC13, with a 10-fold excess of DTPA MAb was added to the conjugate. Labelling efficiency was controlled by incubating 4T0 whom reprint requests should be addressed.

Monoclonal antibody conjugated to gadolinium as a contrast agent for magnetic resonance imaging of human rectal carcinoma

“…Methods using diethylenetriaminepentaacetic acid (DTPA) as a chelating substance have been reported for Mabs [16]. It is easy to conjugate a Mab to a high number of DTPA [17]. However, high uptake has always been observed with 111 In-DTPA in the liver [18,19].…”

In vitro studies of gadolinium-DTPA conjugated with monoclonal antibodies as cancer-specific magnetic resonance imaging contrast agents

“…It is possible to increase the amount of DTPA coupling per molecule of mab, although with a corresponding loss of immunoreactivity (1,3,10). In order to improve the quality of imaging and increase efficacy of therapy using radiometal-labeled mab, cyclic DTPA anhydride has been developed and well characterised.…”

“…The following is an adopted method used for insertion of gadolinium (3,11) and is the optimized procedure.…”

“…One approach to increasing the specificity of MR image contrast is to use a monoclonal antibody (mab) coupled with contrast agent Gd-DTPA (1)(2)(3)(4). The use of antibodies for diagnostic imaging in the search for tumors was established in 1953 by Pressman and Korngold (5), who imaged a tumor in a rat using 131 I-labelled polyclonal antibodies.…”

Magnetic resonance imaging of esophageal squamous cell carcinoma using magnetite particles coated with anti-epidermal growth factor receptor antibody

“…Binding numerous gadolinium ions to an antibody creates the problem of decreasing its immunologic activity (Rosenthal et al, 1993). Gd-DTPA (diethylenetriamine penta-acetic acid) has been used by several investigators, all of whom have encountered difficulty in obtaining a clinically useful contrast effect (Khaw et al, 1984;Courtet et al, 1988).…”