RNA interference screening identifies lenalidomide sensitizers in multiple myeloma, including RSK2.
To identify molecular targets that modify sensitivity to lenalidomide, we measured proliferation in multiple myeloma (MM) cells transfected with 27 968 small interfering RNAs in the presence of increasing concentrations of drug and identified 63 genes that enhance activity of lenalidomide upon silencing. Ribosomal protein S6 kinase (RPS6KA3 or RSK2) was the most potent sensitizer. Other notable gene targets included 5 RAB family members, 3 potassium channel proteins, and 2 peroxisome family members. Single genes of interest included I-κ-B kinase-α (CHUK), and a phosphorylation dependent transcription factor (CREB1), which associate with RSK2 to regulate several signaling pathways. RSK2 knockdown induced cytotoxicity across a panel of MM cell lines and consistently increased sensitivity to lenalidomide. Accordingly, 3 small molecular inhibitors of RSK2 demonstrated synergy with lenalidomide cytotoxicity in MM cells even in the presence of stromal contact. Both RSK2 knockdown and small molecule inhibition downregulate interferon regulatory factor 4 and MYC, and provides an explanation for the synergy between lenalidomide and RSK2 inhibition. Interestingly, RSK2 inhibition also sensitized MM cells to bortezomib, melphalan, and dexamethasone, but did not downregulate Ikaros or influence lenalidomide-mediated downregulation of tumor necrosis factor-α or increase lenalidomide-induced IL-2 upregulation. In summary, inhibition of RSK2 may prove a broadly useful adjunct to MM therapy.
Division of Hematology-Oncology, Mayo Clinic, Scottsdale, AZ; and.
Yuan Xiao
YX
Zhu
Translational Genomics Research Institute, Phoenix, AZ.
Hongwei
H
Yin
Division of Hematology-Oncology, Mayo Clinic, Scottsdale, AZ; and.
Laura A
LA
Bruins
Division of Hematology-Oncology, Mayo Clinic, Scottsdale, AZ; and.
Chang-Xin
CX
Shi
Division of Hematology-Oncology, Mayo Clinic, Scottsdale, AZ; and.
Patrick
P
Jedlowski
Translational Genomics Research Institute, Phoenix, AZ.
Meraj
M
Aziz
Translational Genomics Research Institute, Phoenix, AZ.
Chris
C
Sereduk
Division of Hematology-Oncology, Mayo Clinic, Scottsdale, AZ; and.
Klaus Martin
KM
Kortuem
Division of Hematology-Oncology, Mayo Clinic, Scottsdale, AZ; and.
Jessica E
JE
Schmidt
Division of Hematology-Oncology, Mayo Clinic, Scottsdale, AZ; and.
Mia
M
Champion
Division of Hematology-Oncology, Mayo Clinic, Scottsdale, AZ; and.
Esteban
E
Braggio
Division of Hematology-Oncology, Mayo Clinic, Scottsdale, AZ; and.
A
A
Keith Stewart
D020533:Angiogenesis Inhibitors / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects* / Q000235:genetics; D004354:Drug Screening Assays, Antitumor; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D053263:Gene Regulatory Networks; D006801:Humans; D050835:Interferon Regulatory Factors / Q000235:genetics / Q000378:metabolism; D000077269:Lenalidomide; D009101:Multiple Myeloma / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000032:analysis / Q000235:genetics / Q000302:isolation & purification*; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000037:antagonists & inhibitors* / Q000235:genetics; D013792:Thalidomide / Q000031:analogs & derivatives* / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D000099218:Interferon Regulatory Factor-4
D020533:Angiogenesis Inhibitors; D050835:Interferon Regulatory Factors; D000077269:Lenalidomide; D047428:Protein Kinase Inhibitors; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D013792:Thalidomide; D000099218:Interferon Regulatory Factor-4; C489427:MYC protein, human; C069330:ribosomal protein S6 kinase, 90kDa, polypeptide 3