Strong uptake of 111in‐pentetreotide by an MIBG‐negative, xenografted neuroblastoma

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Abstract
We investigated the distribution of 111In-pentetreotide (Octreoscan, Mallinckrodt) in nude mice xenografted with a human neuroblastoma cell line (SKLAN, derived from the LAN I line). These cells develop into solid tumours in nude mice and can be grafted repeatedly in grafts of 108 cells. Animals were sequentially explored by scintigraphy 2, 4, 24 and 48 hr after i.v. injection of 2.5-4 MBq of the tracer and killed at various times up to 46 hr. 111In-pentetreotide was rapidly and strongly taken up by all tumours, with a tumour/muscle (T/M) ratio on resected samples of 20.0 ± 5.7 at 2 hr, 23.7 ± 3.0 at 4 hr, 75.6 ± 12.6 at 24 hr and 78.7 ± 12.4 at 48 hr, for tumours ranging from 0.5 to 8 g. Scintigraphy results were quantitatively in agreement Pre-injection of a 15-20 times larger quantity of unlabelled octreotide s.c. reduced the tumour uptake by a factor of 2. For comparison, nude mice xenografted with the same cell line were also studied with 123I-MIBG (4 MBq). At 24 hr, the T/M ratio was 0.62 ± 0.18. Two other cell lines (glioblastoma ROM and small-cell lung carcinoma SC41) which were similarly tested with 111In-pentetreotide (2.5-4 MBq) gave T/M ratios at 24 hr of 4.8 ± 2.8 and 38.4 ± 21.8, respectively. Pentetreotide seems to have a high affinity for this MIBG-negative neuroblastoma cell line, which exhibited a clearly higher tumour uptake than the 2 other lines. This work provides new experimental arguments in favour of the particular interest of somatostatin analogues in neuroblastoma and confirms our first clinical results.