CpG immunomer DNA enhances antisense protein kinase A RIalpha inhibition of multidrug-resistant colon carcinoma growth in nude mice: molecular basis for combinatorial therapy.
OBJECTIVE
CpG DNAs induce cytokines, activate natural killer cells, and elicit vigorous T-cell response leading to antitumor effects. Antisense oligodeoxynucleotides targeted against the RIalpha subunit of protein kinase A (antisense PKA RIalpha) induce growth arrest, apoptosis, and differentiation in a variety of cancer cell lines in vitro and in vivo. This study investigated the use of a combinatorial therapy consisting of the RNA-DNA second-generation antisense PKA RIalpha and the CpG immunomer (CpG DNA linked through 3'-3' linkage containing two accessible 5' ends).


METHODS
HCT-15 multidrug-resistant colon carcinoma growth in nude mice was used as an experimental model. The inhibitory effect on tumor growth and apoptotic activity of antisense RIalpha and CpG immunomer, singly and in combination, were measured by tumor growth, levels of RIalpha subunit, and antiapoptotic and proapoptotic proteins. Effect on host-immune system was measured by mouse spleen size, interleukin-6 (IL-6) levels in mouse blood, and nuclear factor-kappaB (NF-kappaB) transcription activity in mouse spleen cells.


RESULTS
In combination, CpG immunomer and antisense PKA RIalpha induced additive/supra-additive effect on the inhibition of tumor growth. Antisense RIalpha but not CpG immunomer increased Bax and Bak proapoptotic protein levels and decreased Bcl-2 and RIalpha protein levels in tumor cells. CpG immunomer but not antisense RIalpha induced an enlargement of mouse spleen, increased IL-6 levels in mouse blood, and increased NF-kappaB transcription activity in mouse spleen cells.


CONCLUSIONS
These results show that type I PKA down-regulation and induction of apoptosis in tumor cells by antisense PKA RIalpha, and host-immune stimulation by CpG immunomer are responsible at the molecular level for the supra-additive effects of tumor growth inhibition. Thus, antisense PKA RIalpha and CpG immunomer in combination work cooperatively and as tumor-targeted therapeutics to treat human cancer.
Nesterova
Maria V
MV
Basic Research Laboratory, Cellular Biochemistry Section, National Cancer Institute, Bethesda, Maryland 20892-1750, USA.
Johnson
Natalie R
NR
Stewart
Trina
T
Abrams
Scott
S
Cho-Chung
Yoon S
YS
D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D001483:Base Sequence; D015153:Blotting, Western; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D018899:CpG Islands / Q000235:genetics* / Q000276:immunology; D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics* / Q000378:metabolism; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D016328:NF-kappa B / Q000378:metabolism; D009841:Oligonucleotides / Q000008:administration & dosage / Q000235:genetics; D016376:Oligonucleotides, Antisense / Q000008:administration & dosage / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D013997:Time Factors; D016896:Treatment Outcome; D023041:Xenograft Model Antitumor Assays / Q000379:methods; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism
D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; D015850:Interleukin-6; D016328:NF-kappa B; D009841:Oligonucleotides; D016376:Oligonucleotides, Antisense; C517834:PRKAR1A protein, human; C517835:Prkar1a protein, mouse; D019253:Proto-Oncogene Proteins c-bcl-2; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D017868:Cyclic AMP-Dependent Protein Kinases