Distribution of labelled anti-tenascin antibodies and fragments after injection into intact or partly resected C6-gliomas in rats

Abstract

Introduction: For treatment of malignant glioma, radioimmunotherapy has become a valuable alternative for more than 2 decades. Surprisingly, very little is known about the distribution of intralesionally administered labelled antibodies or fragments. We investigated the migration of labelled antibodies and antibody fragments injected into intact and partly resected C6-glioma in rats at different times after injection.

Materials and methods: Nine days after induction of a C6-glioma, 5 microl of 125I-labelled murine anti-tenascin antibodies (n = 31) or 125I-labelled fragments of anti-tenascin antibodies (n = 32) was injected slowly into the tumour (group I). In group II the tumour was subtotally resected 9 days after induction of the C6-glioma, and 24 h later the labelled antibodies (n = 30) or fragments (n = 12) were injected into the resection cavity. At 6, 24 or 48 h after the injection, animals were sacrificed, and brains removed. Distribution of labelled antibodies and fragments was determined by superimposing autoradiographs onto frozen sections and HE-stained neighbouring sections using a digital image analysing system.

Results: After injection into intact C6-glioma, labelled antibodies covered a maximum distance of 3.2 +/- 1.0, 4.1 +/- 1.9 and 4.8 +/- 0.9 mm after 6, 24 and 48 h, respectively; while labelled fragments were found at a distance of 6.7 mm (+/-1.1) after 24 h and 5.8 mm (+/-0.9) after 48 h (significant in univariate analysis). Following partial tumour resection, the respective distances at 24 h were 3 +/- 0.4 mm for anti-tenascin antibodies and 3.4 +/- 0.3 mm for Fab fragments.

Conclusion: After injection into C6-glioma, labelled fragments are able to cover a greater distance than labelled antibodies. Injection of antibodies and fragments 1 day after tumour resection results in reduced velocity of both antibodies and fragments.

Fig. 1

T1-weighted MR image of a rat brain in coronal orientation on day 8 after induction of C6-glioma. Tumour indicated with white arrows.

Fig. 2

Sketch showing the matching of frozen sections (a) with corresponding autoradiographs (b) for further evaluation (c).

Fig. 3

Coronal section of C6-glioma matched with autoradiograph (dark area) showing needle tract (white line), distance measurement (dotted line) and determination of the area of propagation (black line).

Fig. 4

Maximum propagation of labelled antibodies and labelled fragments at different time points after injection in intact tumours.

Fig. 5

Maximum propagation of labelled antibodies and labelled fragments at different time points after injection in subtotally resected tumours.