Selective efficacy of depsipeptide in a xenograft model of Epstein-Barr virus-positive lymphoproliferative disorder.
BACKGROUND
Immune-compromised individuals are at increased risk for developing aggressive Epstein-Barr virus (EBV)-associated lymphoproliferative disorders after primary EBV infection or for reactivation of a preexisting latent EBV infection. We evaluated the effect of depsipeptide, a histone deacetylase inhibitor, on EBV-positive lymphoblastoid cell lines (LCLs) and Burkitt lymphoma cell lines in a mouse model and explored its mechanism of action in vitro.


METHODS
We studied EBV-transformed LCLs, which express a latent III (Lat-III) viral gene profile, as do some EBV-positive lymphoproliferative malignancies, and Burkitt lymphoma cell lines, which express a Lat-I viral gene profile. Cell lines were used to characterize depsipeptide-induced apoptosis, which was evaluated by flow cytometry. Flow cytometry, western blot analyses, and histone deacetylase inhibitors were used to investigate components of prodeath and survival pathways in vitro. We studied depsipeptide's effects on survival with a mouse xenograft model of EBV-positive human B-cell tumors (groups of 10 mice). All statistical tests were two-sided.


RESULTS
Depsipeptide (5 mg/m2 of body surface area) treatment was associated with statistically significantly improved survival of mice carrying Lat-III EBV-positive LCL tumors, compared with that of control-treated mice (day 30: for depsipeptide-treated mice, 90% survival, 95% confidence interval [CI] = 73.2% to 100%; for control-treated mice, 20% survival, 95% CI = 5.79% to 69.1%; P<.001), but it was not associated with survival of mice carrying Lat-I EBV-positive Burkitt lymphoma tumors. Depsipeptide induced apoptosis in 64% of LCLs and in 14% of EBV-positive Burkitt lymphoma cells in vitro. Depsipeptide-treated LCL cultures had two distinct cell populations--one sensitive and one resistant to depsipeptide. Depsipeptide-mediated apoptosis was associated with a 12-fold increased level of active caspase 3, but some apoptosis persisted despite z-VAD-fmk treatment to inhibit caspase activity. Depsipeptide-resistant LCLs expressed higher levels of latent membrane protein 1 (LMP1; P = .017), BCL2 (P = .032), and nuclear factor kappaB (NF-kappaB) (P<.001) than depsipeptide-sensitive LCLs; this resistance was circumvented by treatment with PS-1145, an inhibitor of NF-kappaB activation (P<.001).


CONCLUSIONS
Apoptosis is induced by depsipeptide via caspase-dependent and -independent pathways in Lat-III EBV-positive LCLs and is enhanced by inhibiting NF-kappaB activity. Depsipeptide as a treatment for Lat-III EBV-associated lymphoproliferative disorders should be explored further in clinical trials.
Department of Molecular Virology, Immunology, and Medical Genetics, The Ohio State University, Columbus, USA.
Sameek
S
Roychowdhury
Robert A
RA
Baiocchi
Srinivas
S
Vourganti
Darshna
D
Bhatt
Bradley W
BW
Blaser
Aharon G
AG
Freud
Jason
J
Chou
Chang-Shi
CS
Chen
Jim J
JJ
Xiao
Mark
M
Parthun
Kenneth K
KK
Chan
Charles F
CF
Eisenbeis
Amy K
AK
Ferketich
Michael R
MR
Grever
Ching-Shih
CS
Chen
Michael A
MA
Caligiuri
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002051:Burkitt Lymphoma / Q000188:drug therapy* / Q000821:virology; D061945:Caspase Inhibitors; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D047630:Depsipeptides; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D020031:Epstein-Barr Virus Infections / Q000150:complications* / Q000276:immunology; D005434:Flow Cytometry; D004854:Herpesvirus 4, Human / Q000276:immunology / Q000302:isolation & purification*; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D016867:Immunocompromised Host; D051379:Mice; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D010456:Peptides, Cyclic / Q000494:pharmacology*; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000188:drug therapy* / Q000821:virology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000187:drug effects / Q000378:metabolism; D013936:Thymidine / Q000378:metabolism; D014183:Transplantation, Heterologous; D014763:Viral Matrix Proteins / Q000187:drug effects / Q000378:metabolism
D000970:Antineoplastic Agents; D061945:Caspase Inhibitors; D047630:Depsipeptides; C037662:EBV-associated membrane antigen, Epstein-Barr virus; D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D016328:NF-kappa B; D010456:Peptides, Cyclic; D019253:Proto-Oncogene Proteins c-bcl-2; D014763:Viral Matrix Proteins; C087123:romidepsin; D013936:Thymidine