Noninvasive monitoring of somatostatin receptor type 2 chimeric gene transfer.
Noninvasive monitoring of gene transfer will benefit basic research and patient care. Most gene-transfer imaging systems do not directly detect the gene of interest, and most do not exploit radiopharmaceuticals that have Food and Drug Administration approval for total-body use. (111)In-Octreotide is used clinically to locate tumors overexpressing primarily somatostatin receptor type 2 (SSTR2). We report the in vitro and in vivo detection of SSTR2 chimeric gene transfer with this radiopharmaceutical.


METHODS
Full-length SSTR2A was ligated into a vector downstream of a 5' Igkappa leader sequence and the hemagglutinin A (HA) sequence. The vector plus insert was then introduced into HT1080 cells. Igkappa and HA domain functions were confirmed by immunologic methods. Receptor binding was studied in transfected cells incubated with (111)In-octreotide with and without somatostatin-28. Mice bearing tumors produced by transfected cells were injected with (111)In-octreotide for biodistribution and imaging studies.


RESULTS
Cell-membrane localization by the amino-terminal Igkappa domain was confirmed by immunofluorescence. The HA domain was identified by enzyme-linked immunosorbent assay, immunofluorescence, and Western blotting analysis with anti-HA antibodies. (111)In-Octreotide detected the SSTR2 portion of the fusion protein in vitro (receptor-binding assay) and in vivo (biodistribution studies and gamma-camera imaging). In addition, in vitro studies using either the anti-HA antibody or (111)In-octreotide correlated with biodistribution and imaging studies when cell clones expressing different levels of the fusion protein were tested. This approach may be feasible clinically because we were able to discern chimeric gene transfer in tumor-bearing animals with (111)In-octreotide at doses similar to those already used in humans.


CONCLUSIONS
With this method it may be possible to monitor transfer of a gene of interest directly and noninvasively.
Kundra
Vikas
V
Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA. vkundra@di.mdacc.tmc.edu
Mannting
Finn
F
Jones
Alun G
AG
Kassis
Amin I
AI
D000818:Animals; D001426:Bacterial Proteins; D015153:Blotting, Western; D002460:Cell Line; D002999:Clone Cells; D004797:Enzyme-Linked Immunosorbent Assay; D005455:Fluorescent Antibody Technique; D018014:Gene Transfer Techniques; D005822:Genetic Vectors; D006388:Hemagglutinins / Q000235:genetics; D006801:Humans; D037102:Lectins; D051379:Mice; D008819:Mice, Nude; D009374:Neoplasms, Experimental / Q000378:metabolism; D015282:Octreotide / Q000031:analogs & derivatives*; D019275:Radiopharmaceuticals; D017481:Receptors, Somatostatin / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism*; D014018:Tissue Distribution
D001426:Bacterial Proteins; D006388:Hemagglutinins; D037102:Lectins; D019275:Radiopharmaceuticals; D017481:Receptors, Somatostatin; D011993:Recombinant Fusion Proteins; C114923:hemagglutinin A, Porphyromonas gingivalis; C094279:indium-111-octreotide; C093733:somatostatin receptor 2; D015282:Octreotide