Functional interleukin-7 receptors (IL-7Rs) are expressed by marrow stromal cells: binding of IL-7 increases levels of IL-6 mRNA and secreted protein.
DNA spotted microarrays were used to compare gene expression profiles from 2 functionally distinct human marrow stromal cell lines: HS-27a, which supports cobblestone area formation by early hematopoietic progenitors, and HS-5, which secretes multiple cytokines that support the proliferation of committed progenitors. One unexpected result was the high level of interleukin-7 receptor (IL-7R) gene expression in HS-27a stromal cells. Northern blot analysis confirmed the IL-7R RNA expression, and Western blots for the IL-7R protein detected both a full-length (90-kd) IL-7R and a smaller 30-kd fragment in both HS-27a cells and primary stromal cell cultures, whereas only the 90-kd receptor protein was detected in peripheral blood mononuclear cells. Biotinylated IL-7 was shown to bind to HS-27a cells under physiologic conditions, and this binding was inhibited by blocking anti-IL-7 antibodies. Tyrosine phosphorylation of several proteins (55 kd, 30 kd, and 24 kd) in HS-27a cells was rapidly increased after incubation with recombinant IL-7. One of the phosphorylated proteins proved to be the 30-kd IL-7R fragment. Exposure of HS-27a cells to IL-7 resulted in a 10-fold increase in secretion of IL-6 into culture supernatants but no increase in the cytokines stromal cell-derived factor 1, macrophage inflammatory protein 1 alpha, or IL-1 beta. The up-regulation of IL-6 secretion is associated with a rapid but transient increase in detectable levels of IL-6 messenger RNA. These data suggest that IL-7 may function to regulate the milieu of the microenvironment by modulating IL-6 secretion by the IL-7R-expressing stromal elements.
Iwata
Mineo
M
Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA. miwata@fhcrc.org
Graf
Lynn
L
Awaya
Norihiro
N
Torok-Storb
Beverly
B
D000906:Antibodies / Q000494:pharmacology; D015152:Blotting, Northern; D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000378:metabolism*; D002455:Cell Division; D002460:Cell Line; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D015870:Gene Expression; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism*; D015851:Interleukin-7 / Q000276:immunology / Q000378:metabolism* / Q000494:pharmacology; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D020395:Receptors, Interleukin-7 / Q000235:genetics* / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism / Q000494:pharmacology; D017154:Stromal Cells / Q000378:metabolism*
D000906:Antibodies; D015850:Interleukin-6; D015851:Interleukin-7; D012333:RNA, Messenger; D020395:Receptors, Interleukin-7; D011994:Recombinant Proteins; D019000:Phosphotyrosine