G3139 and other CpG-containing immunostimulatory phosphorothioate oligodeoxynucleotides are potent suppressors of the growth of human tumor xenografts in nude mice.
Several phosphorothioate antisense oligodeoxynucleotides (ODN) are developed to target factors potentially involved in tumor growth and apoptosis suppression. Among them, the 18-mer G3139 (Oblimersen), which targets Bcl-2, is currently being tested in phase II and phase III clinical trials for various tumors in combination with chemotherapy. On the other hand, ODNs containing CpG dinucleotides (CpG-ODN) within specific-sequence contexts (CpG motifs) have been shown to activate rodent or primate immune cells via toll-like receptor 9 (TLR9) and have demonstrated remarkable T cell-dependent antitumor efficacy in a series of murine tumor models. However, immune cell activation by CpG-ODN is largely diminished upon C-5 methylation at CpG cytosine. As G3139 contains CpG motifs, we questioned whether the antitumor effects seen in human tumor xenografts might be abrogated by cytosine C-5 methylation of G3139, which retained the ability of G3139 to suppress Bcl-2 expression in tissue culture, or by similar derivatization of other phosphorothioate ODNs developed for the immune activation of rodent or human cells. The in vivo antitumor efficacy of the immunostimulatory H1826 and H2006 ODNs was compared with that of G3139. Bcl-2 suppression achieved by G3139 purportedly sensitizes tumor cells toward cytotoxic agents, and some of the experiments employed combinations of ODN with such drugs as cisplatin or etoposide. H1826, H2006, and G3139 all produced similar, striking, growth inhibitory effects on either H69 SCLC, A2780 ovarian carcinoma, or A549 lung adenocarcinoma human tumor xenografts at doses of 0.3 mg/kg and 1 mg/kg (H1826, H2006) or 12 mg/kg (G3139) per day. In contrast, the H2006-mC (1 mg/kg) or G3139-mC (12 mg/kg) derivatives demonstrated no significant antitumor effects. The combination of G3139 (12 mg/kg) with cisplatin produced some additive antitumor efficacy, which was not seen in combinations of G3139-mC (12 mg/kg) or H1826 (1 mg/kg) with cisplatin. G3139, at a dose of 12 mg/kg, alone induced extensive enlargement of the spleen. Immunostimulation was evaluated in vitro by flow cytometric measurements of the CD80 and CD86 activation markers found on CD19+ murine splenocytes. The CpG-ODN producing strong antitumor effects in vivo also induced these activation markers in vitro, in contrast to the in vivo inactive G3139-mC. Our data indicate a significant contribution of the immunostimulatory properties of CpG-ODN (including G3139) to the antitumor effects observed in nude mouse xenograft models. This is in contrast to previous data presented by other authors indicating that the activity of G3139 in human tumor xenografts was Bcl-2 specific. Furthermore, as nude mice are devoid of T cells, a T cell-mediated immune response apparently is not required for the potent antitumor responses observed here; innate immune responses are sufficient.
ALTANA Pharma AG, 78465 Konstanz, Germany. volker.gekeler@altanapharma.com
Volker
V
Gekeler
Petra
P
Gimmnich
Hans-Peter
HP
Hofmann
Carola
C
Grebe
Michaela
M
Römmele
Astrid
A
Leja
Monika
M
Baudler
Luba
L
Benimetskaya
Barbara
B
Gonser
Uwe
U
Pieles
Thomas
T
Maier
Thomas
T
Wagner
Karl
K
Sanders
James F
JF
Beck
Guido
G
Hanauer
C A
CA
Stein
D000230:Adenocarcinoma / Q000188:drug therapy / Q000276:immunology; D000276:Adjuvants, Immunologic / Q000008:administration & dosage / Q000737:chemistry / Q000627:therapeutic use*; D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000737:chemistry / Q000627:therapeutic use*; D001402:B-Lymphocytes / Q000187:drug effects; D002277:Carcinoma / Q000188:drug therapy / Q000276:immunology; D045744:Cell Line, Tumor; D003596:Cytosine / Q000737:chemistry; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy / Q000276:immunology; D008213:Lymphocyte Activation; D008745:Methylation; D051379:Mice; D008819:Mice, Nude; D009369:Neoplasms / Q000188:drug therapy*; D009838:Oligodeoxyribonucleotides / Q000008:administration & dosage / Q000737:chemistry / Q000627:therapeutic use*; D010051:Ovarian Neoplasms / Q000188:drug therapy / Q000276:immunology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D013873:Thionucleotides / Q000008:administration & dosage / Q000737:chemistry / Q000627:therapeutic use*; D023041:Xenograft Model Antitumor Assays
D000276:Adjuvants, Immunologic; D000970:Antineoplastic Agents; C408982:CPG-oligonucleotide; D009838:Oligodeoxyribonucleotides; D019253:Proto-Oncogene Proteins c-bcl-2; D013873:Thionucleotides; C408162:oblimersen; D003596:Cytosine