Antisense c-myc and immunostimulatory oligonucleotide inhibition of tumorigenesis in a murine B-cell lymphoma transplant model.
BACKGROUND
Because the development of drug-resistant cells can lead to relapses in patients with lymphoma treated with chemotherapy, new approaches are needed for effective disease management, such as those targeting the c-MYC proto-oncogene with antisense oligonucleotides. Our goal was to investigate whether antisense c-myc oligonucleotides could prevent tumorigenesis in a B-cell lymphoma model.


METHODS
Immunocompetent mice received subcutaneous injections of tumor cells from a transgenic mouse model of Burkitt's lymphoma. For 7 consecutive days, beginning 1 day after tumor cell transplantation, the mice were given either a DNA phosphorothioate oligonucleotide complementary to c-myc codons 1-5 (myc6) or other c-myc-related oligonucleotides at a dose of 0.76 mg per day subcutaneously. Myc protein expression, normalized to beta-actin expression, was measured by western blotting of tumor and splenic proteins. To determine whether tumor inhibition by myc6 could be a result of B-cell activation, we compared the activity of myc6 with that of an immunostimulatory oligonucleotide, mcg.


RESULTS
In comparison with control treatments (saline vehicle, scrambled-sequence oligonucleotide, or double-mismatch oligonucleotide), treatment with myc6 delayed tumor onset by 3 days, decreased total tumor mass at sacrifice (i.e., 17 days after tumor cell transplantation) by 40% +/- 16% (mean +/- standard error), and decreased the splenic Myc-to-actin ratio. Inhibition of tumors by myc6 and mcg (both of which share a dACGTT motif) was comparable. Administration of an oligonucleotide sequence complementary to c-myc codons 384-388 (myc55) delayed tumor onset by 5-6 days, decreased total tumor mass at sacrifice by 65% +/- 6%, and reduced the splenic Myc-to-actin ratio to below that produced by myc6. A 14-day treatment regimen of myc55 alternating with mcg completely inhibited tumor formation during the therapeutic schedule.


CONCLUSIONS
A combined oligonucleotide regimen, based on antisense c-MYC and immunostimulatory oligonucleotides, should be investigated to increase the number and duration of complete remissions obtained after standard chemotherapy for B-cell lymphoma.
Department of Microbiology and Immunology, Kimmel Cancer Center, and Cardeza Foundation for Hematological Research, Thomas Jefferson University, Philadelphia, PA 19107, USA.
J B
JB
Smith
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E
Wickstrom
D000276:Adjuvants, Immunologic / Q000235:genetics* / Q000627:therapeutic use* / Q000633:toxicity; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D003062:Codon; D016207:Cytokines / Q000097:blood; D016259:Genes, myc; D016393:Lymphoma, B-Cell / Q000517:prevention & control*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009368:Neoplasm Transplantation; D016376:Oligonucleotides, Antisense / Q000235:genetics* / Q000627:therapeutic use* / Q000633:toxicity; D013154:Spleen / Q000033:anatomy & histology / Q000187:drug effects; D013873:Thionucleotides / Q000235:genetics* / Q000627:therapeutic use* / Q000633:toxicity
D000276:Adjuvants, Immunologic; D003062:Codon; D016207:Cytokines; D016376:Oligonucleotides, Antisense; D013873:Thionucleotides