Cell cycle and apoptosis regulatory protein (CARP)-1 is a novel, adriamycin-inducible, diffuse large B-cell lymphoma (DLBL) growth suppressor.
Diffuse large B-cell lymphoma (DLCL) accounts for 30-40% of adult non-Hodgkin's Lymphoma (NHL). Current anti-NHL therapies often target cellular growth suppression pathways and include R-CHOP (cyclophosphamide, adriamycin, vincristine, and prednisone plus monoclonal anti-CD20 antibody rituximab). However, since many patients relapse, resistant cells to these therapies remain a significant problem and necessitate development of new intervention strategies. Cell cycle and apoptosis regulatory protein (CARP)-1 functions in a biphasic manner to regulate growth factor as well as chemotherapy (adriamycin, etoposide, or iressa)-dependent signaling.


OBJECTIVE
To determine whether CARP-1 is a novel suppressor of lymphoma growth.


METHODS
Flow cytometric analyses coupled with Western immunoblotting, cell growth, apoptosis, and immunocytochemistry methodologies were utilized to determine CARP-1-dependent lymphoma growth inhibition in vitro and in vivo.


RESULTS
CARP-1 expression correlated with activated caspase-3 and inversely correlated with activated Akt in DLCL. Exposure to adriamycin stimulated CARP-1 expression and inhibited growth of Raji cells, but not CHOP-resistant WSU-DLCL2 cells. Expression of wild-type CARP-1 or its apoptosis-inducing mutants inhibited growth of Raji as well as CHOP-resistant WSU-DLCL2 cells, in part by activating caspase-9 and apoptosis. Since CARP-1 harbors multiple, apoptosis-promoting subdomains, we investigated whether epigenetic compensation of CARP-1 function by intracellular delivery of trans-activator of transcription (TAT) domain-tagged CARP-1 peptide(s) will inhibit lymphoma growth. Treatments with TAT-tagged CARP-1 peptides suppressed growth of the Raji and WSU-DLCL2 cells by stimulating apoptosis. TAT-CARP-1 (1-198) as well as (896-1150) peptides also suppressed growth of WSU-DLCL2 cell-derived tumor xenografts in SCID mice, while administration of TAT-CARP-1 (1-198) also inhibited growth of WSU-FSCCL cell-derived ascites and prolonged host survival.


CONCLUSIONS
CARP-1 is a suppressor of NHL growth and could be exploited for targeting the resistant DLCL.
Levi
Edi
E
Room B4334, Veterans Affairs Medical Center, Wayne State University, 4646 John R, Detroit, MI 48201, USA.
Zhang
Liyue
L
Aboukameel
Amro
A
Rishi
Sunny
S
Mohammad
Ramzi M
RM
Polin
Lisa
L
Hatfield
James S
JS
Rishi
Arun K
AK
D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D053148:Caspase 3 / Q000378:metabolism; D018797:Cell Cycle Proteins; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D004317:Doxorubicin / Q000494:pharmacology; D006801:Humans; D016403:Lymphoma, Large B-Cell, Diffuse / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D016513:Mice, SCID; D009154:Mutation; D041681:NIH 3T3 Cells; D009368:Neoplasm Transplantation; D010446:Peptide Fragments / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D014183:Transplantation, Heterologous
D000903:Antibiotics, Antineoplastic; D051017:Apoptosis Regulatory Proteins; C477529:CCAR1 protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D010446:Peptide Fragments; D004317:Doxorubicin; D051057:Proto-Oncogene Proteins c-akt; D053148:Caspase 3
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