Phospho-p70S6K/p85S6K and cdc2/cdk1 are novel targets for diffuse large B-cell lymphoma combination therapy.
OBJECTIVE
This study aimed to identify and evaluate molecular targets for the development of a novel combination chemotherapy to treat refractory and recurrent diffuse large B-cell lymphoma (DLBCL).


METHODS
Lymphoma samples from 38 cases of primary and recurrent DLBCL were analyzed using real-time quantitative PCR of the RPS6KB1 and CDC2 genes, and immunohistochemistry for their gene products p70S6K/p85S6K and cdc2/cdk1. The Farage, Karpas422, Pfeiffer, and Toledo DLBCL cell lines were subsequently treated with rapamycin and UCN-01 alone or in combination. Cell proliferation, apoptosis, and cell cycle progression were analyzed after the drug treatment. In addition, the levels of several key protein kinases involved in the phosphoinositide 3'-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway, apoptosis, and cell cycle progression were analyzed in the presence and absence of the drugs.


RESULTS
Amplification of the RPS6KB1 and CDC2 genes was found in both primary and recurrent DLBCL. Moreover, the vast majority of these lymphomas (approximately 94%) were strongly positive for phospho-p70S6K and cdc2/cdk1 proteins. The combination of rapamycin and UCN-01 synergistically inhibited the DLBCL cell proliferation by inducing G1 arrest as well as apoptosis by suppressing the phosphorylation of p70S6K/p85S6K and CDC2 expression.


CONCLUSIONS
RPS6KB1 and CDC2 overexpression is common in DLBCL. Simultaneously targeting the RPS6KB1 and CDC2 products phospho-p70S6K/p85S6K and cdc2/cdk1 is very effective in inhibiting DLBCL proliferation and overcoming drug resistance. This work suggests that multilevel inhibition of the PI3K/Akt/mTOR pathway and double-block of cell cycle progression are effective strategies for DLBCL therapy.
Zhao
Merry Y
MY
Department of Pathology, University of Maryland School of Medicine, Marlene and Stewart Greenebaum Cancer Center, Baltimore, Maryland 21201, USA.
Auerbach
Aaron
A
D'Costa
Anisha M
AM
Rapoport
Aaron P
AP
Burger
Angelika M
AM
Sausville
Edward A
EA
Stass
Sanford A
SA
Jiang
Feng
F
Sands
Amy M
AM
Aguilera
Nadine
N
Zhao
X Frank
XF
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D016203:CDC2 Protein Kinase / Q000235:genetics / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects; D019926:Cyclin B / Q000235:genetics / Q000378:metabolism*; D018844:Cyclin-Dependent Kinases; D004357:Drug Synergism; D005260:Female; D005434:Flow Cytometry; D016193:G1 Phase / Q000187:drug effects; D020869:Gene Expression Profiling; D006801:Humans; D007124:Immunoenzyme Techniques; D016403:Lymphoma, Large B-Cell, Diffuse / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000378:metabolism / Q000473:pathology*; D020411:Oligonucleotide Array Sequence Analysis; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000235:genetics / Q000378:metabolism*; D020123:Sirolimus / Q000008:administration & dosage; D019311:Staurosporine / Q000008:administration & dosage / Q000031:analogs & derivatives; D058570:TOR Serine-Threonine Kinases; D014407:Tumor Cells, Cultured
D016203:CDC2 Protein Kinase; D019926:Cyclin B; D018844:Cyclin-Dependent Kinases; D019869:Phosphatidylinositol 3-Kinases; D011494:Protein Kinases; D051057:Proto-Oncogene Proteins c-akt; D012333:RNA, Messenger; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D020123:Sirolimus; D019311:Staurosporine; D058570:TOR Serine-Threonine Kinases; C054852:7-hydroxystaurosporine; C546842:MTOR protein, human; C448901:ribosomal protein S6 kinase, 70kD, polypeptide 1; C528899:CDK1 protein, human