Heterogeneous expression and function of IL-21R and susceptibility to IL-21-mediated apoptosis in follicular lymphoma cells.
OBJECTIVE
Interleukin (IL)-21, a member of the IL-2 family, has antitumor activity and is now being tested in non-Hodgkin's lymphoma in combination with anti-CD20 antibodies. IL-21 may either induce apoptosis or promote growth in different lymphoid malignancies. We therefore investigated the IL-21/IL-21R system in follicular lymphoma (FL) cells.


METHODS
IL-21R expression was studied by reverse transcription polymerase chain reaction, immunofluorescence, and Western blot analyses. Apoptosis was measured by Annexin-V-propidium iodide staining. Signaling via IL-21R was studied using antibodies specific for phosphorylated Janus-activating kinase and signal transducers and activators of transcription proteins by Western Blot.


RESULTS
IL-21R was found on primary FL cells in 15 of 15 cases at diagnosis and IL-21 increased apoptosis in 10 of 10 FL samples. However, cells from areas of diffuse growth in FL and from two diffuse lymphomas evolved from previous FL, showed low IL-21R expression. The latter were also resistant to IL-21-mediated apoptosis. Among lymphoma cell lines bearing the t(14;18) translocation, only 1 of 7 showed increased apoptosis in response to IL-21 stimulation. This cell line was IL-21R-positive, whereas five of six nonresponsive cell lines showed very low IL-21R expression. Intriguingly, one of the IL-21-resistant cell lines (DOHH2) expressed high levels of IL-21R. Treatment with IL-21 or IL-4 upregulated suppressor of cytokine signaling 3 gene expression in the IL-21-responsive cell line, but not in DOHH2 cells, which showed defective Janus-activating kinase/signal transducers and activators of transcription signaling in response to IL-21, in relationship to the lack of Janus-activating kinase 3 gene expression.


CONCLUSIONS
These data indicate that low IL-21R expression or defective signal transduction downstream IL-21R may cause refractoriness to IL-21-mediated effects in some FL cells.
de Totero
Daniela
D
Istituto Nazionale per la Ricerca sul Cancro, Genova, Italy.
Capaia
Matteo
M
Fabbi
Marina
M
Croce
Michela
M
Meazza
Raffaella
R
Cutrona
Giovanna
G
Zupo
Simona
S
Loiacono
Fabrizio
F
Truini
Mauro
M
Ferrarini
Manlio
M
Ferrini
Silvano
S
D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor / Q000166:cytology / Q000187:drug effects; D002883:Chromosomes, Human, Pair 14 / Q000648:ultrastructure; D002887:Chromosomes, Human, Pair 18 / Q000648:ultrastructure; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D053738:Interleukin-21 Receptor alpha Subunit / Q000096:biosynthesis / Q000187:drug effects / Q000502:physiology*; D007378:Interleukins / Q000494:pharmacology / Q000502:physiology*; D053616:Janus Kinase 3 / Q000172:deficiency; D053612:Janus Kinases / Q000502:physiology; D008224:Lymphoma, Follicular / Q000235:genetics / Q000473:pathology*; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D050791:STAT Transcription Factors / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000096:biosynthesis / Q000235:genetics; D014178:Translocation, Genetic; D000098546:Interleukin-21
C508117:IL21R protein, human; D053738:Interleukin-21 Receptor alpha Subunit; D007378:Interleukins; D009363:Neoplasm Proteins; C106644:SOCS3 protein, human; D050791:STAT Transcription Factors; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; C507933:JAK3 protein, human; D053616:Janus Kinase 3; D053612:Janus Kinases; D000098546:Interleukin-21