Quantitative gene expression of somatostatin receptors and noradrenaline transporter underlying scintigraphic results in patients with neuroendocrine tumors

Aim: To measure, by a quantitative approach, the gene expression underlying the results of somatostatin receptor (sst) scintigraphy (In-111-DTPA-octreotide) and noradrenaline transporter (NAT) scintigraphy (I-123-MIBG) in patients with neuroendocrine (NE) tumors. Methods: The gene expression of somatostatin receptors 1-5 (sst) and NAT was measured quantitatively by real-time PCR in a group of patients with NE tumors (n = 14) and compared to a group of patients with colorectal adenocarcinomas (n = 15). If available, scintigraphic results were compared with gene expression results (9 octreotide and 3 MIBG scintigraphies). Results: The sst(2) was upregulated in 13 of 14 patients (93%) with NE tumors, and the absolute level of gene expression was highest for sst(2). Gene expression alterations of NAT and the other sst subtypes were more variable. Gene expression of sst(2) was in all cases in agreement with positive octreotide scintigraphies. In 2 of 3 cases where MIBG scintigraphy was positive, NAT was also upregulated. Sst(2) was generally downregulated in the colorectal tumor group with the gene expression of the other receptors being more heterogeneous. Conclusions: In general, changes in gene expression of sst(2) corresponded with scintigraphic results. Our data support that sst(2) is the best target for visualization of NE tumors, whereas NAT is only a useful target in a subpopulation of NE tumors. Comparison of scintigraphic results with quantitative gene expression may be used to achieve a better understanding of the link between them, which in turn could aid in planning and development of noninvasive molecular imaging of key molecular processes. Copyright (C) 2008 S. Karger AG, Basel.