Early detection of chemoresistance in vivo through the use of a radiolabeled antisense oligonucleotide.
OBJECTIVE
Radiolabeled antisense oligonucleotide to target the mRNA of the hmdr1 gene for diagnostic purposes is a new concept for evaluating the chemoresistance of tumors in vivo.


RESULTS
An 18 mer complementary to the zone which contains the translation initiation codon of the hmdr1 gene was modified using one phosphoramidate group and one dimethoxytrityle group at the 5' and 3'ends. It permitted probe radiolabeling by 125I. Chemical modifications made to the antisense probe ensured the stability in biological media tested by incubation with human serum at 37 degrees C from 5 minutes to 24 hours. These modifications did not interfere with recognition of the target. Retention of the antisense probe followed the expression level of the target transcript in in vitro and in vivo studies. In vitro, after a 2-hour incubation in the presence of K562--sensitive (S) and- resistant (R) cell lines, uptake was respectively 4.27 +/- 0.96% ID/mg protein and 7.78 +/- 0.46% ID/mg protein (p < 0.001). In vivo, the ratios between radioactivity found in the tumor and that found in the striated muscle and in the blood were, respectively, 20 and 3 for IGR OV1 resistant tumor and 1 and 0.3 for the sensitive one.


CONCLUSIONS
In our study, resistant cell lines and tumor showed greater retention of the specific probe than the sensitive ones. This constitutes a further advance towards non invasive imaging of resistant genes involved in chemoresistance. These results are encouraging: the current trend in innovative cancer therapy is moving towards targeting the genes of interest.
Touboul
Muriel
M
Radiopharmaceutiques Biocliniques, INSERM E 00-08, CEA LRC 10, Université de Grenoble, 38043 Grenoble, France.
Gauchez
Anne-Sophie
AS
D'Hardemare
Amaury Du Moulinet
Adu M
Lunardi
Joël
J
Deverre
Jean-Robert
JR
Pernin
Claude
C
Mathieu
Jean-Paul
JP
Vuillez
Jean-Philippe
JP
Fagret
Daniel
D
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis* / Q000235:genetics; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004355:Drug Stability; D005260:Female; D019450:Genes, MDR; D006801:Humans; D007457:Iodine Radioisotopes; D020014:K562 Cells / Q000187:drug effects / Q000378:metabolism; D007700:Kinetics; D051379:Mice; D008819:Mice, Nude; D008875:Middle Aged; D009693:Nucleic Acid Hybridization; D016376:Oligonucleotides, Antisense / Q000235:genetics* / Q000493:pharmacokinetics; D010051:Ovarian Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism; D011094:Polyethyleneimine / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics*; D014018:Tissue Distribution; D014407:Tumor Cells, Cultured
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D007457:Iodine Radioisotopes; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D011094:Polyethyleneimine