Systemic Bcl-2 antisense oligodeoxynucleotide in combination with cisplatin cures EBV+ nasopharyngeal carcinoma xenografts in SCID mice.
Nasopharyngeal carcinoma (NPC) is causally linked to Epstein-Barr virus (EBV), and the EBV oncoprotein, latent membrane protein 1 (LMP-1), is expressed in the majority of NPCs. LMP-1 upregulates antiapoptotic genes, including bcl-2, and Bcl-2 protein is overexpressed in NPC. Given the antiapoptotic and chemoprotective effects of Bcl-2, it represents a rational therapeutic target in NPC. We have investigated the antitumor and chemosensitizing effects of the Bcl-2 antisense oligodeoxynucleotide G3139 (oblimersen, Genasense) in NPC. For these studies, we used the C666-1 line, a stably infected NPC-derived line that co-expresses LMP-1 and Bcl-2. We have shown that G3139 treatment of C666-1 in vitro caused sequence-dependent suppression of Bcl-2 protein, inhibition of cell growth and enhanced sensitivity to cisplatin (CDDP), as measured by increased antiproliferative and apoptotic effects. In vivo, G3139 treatment (25 mg/kg every 3 days x 5 doses) delayed engraftment and significantly inhibited growth of established C666-1 xenografts in SCID mice compared to control oligo-treated animals. However, G3139 alone did not prevent engraftment or cure established tumors in any animals. In contrast, G3139 treatment (25 mg/kg every 3 days x 5 starting on day 7) in combination with CDDP (8 mg/kg on day 14) completely abrogated tumor engraftment in 80% of animals compared to CDDP (0%) or CDDP + control oligo (0%). When treatment was delayed until tumor was established, G3139 in combination with CDDP significantly inhibited tumor growth compared to CDDP or CDDP + control oligo, and cured 69% animals with established tumors. No animals treated with G3139, CDDP or CDDP + control oligo were cured. Tumor burden and response to treatment correlated with EBV DNA load in serum, measured by real-time PCR. Western blots of tumor extracts obtained during oligo treatment showed that Bcl-2 levels were significantly decreased in G3139-treated animals. Our studies have demonstrated that the Bcl-2 antisense oligodeoxynucleotide, G3139, has proapoptotic effects in C666-1, and in combination with CDDP, is curative in C666-1 NPC xenograft tumors in vivo. The sequence-dependency of these effects is consistent with an antisense mechanism. These studies suggest that Bcl-2 may represent a biologically relevant target for the development of novel combinatorial therapies for NPC.
Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520-8028, USA. jill.lacy@yale.edu
Jill
J
Lacy
Regina
R
Loomis
Susan
S
Grill
Pavani
P
Srimatkandada
Rocco
R
Carbone
Yung-Chi
YC
Cheng
D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002277:Carcinoma / Q000188:drug therapy* / Q000821:virology; D002945:Cisplatin / Q000494:pharmacology*; D004279:DNA, Viral / Q000097:blood / Q000302:isolation & purification; D004854:Herpesvirus 4, Human / Q000235:genetics / Q000302:isolation & purification*; D051379:Mice; D016513:Mice, SCID; D009303:Nasopharyngeal Neoplasms / Q000188:drug therapy* / Q000821:virology; D013873:Thionucleotides / Q000494:pharmacology*; D014183:Transplantation, Heterologous; D047368:Tumor Burden; D019562:Viral Load; D014763:Viral Matrix Proteins / Q000302:isolation & purification
D004279:DNA, Viral; C037662:EBV-associated membrane antigen, Epstein-Barr virus; D013873:Thionucleotides; D014763:Viral Matrix Proteins; C408162:oblimersen; D002945:Cisplatin