IL-2 inhibits proliferation of K562 cells and reduces accumulation of bcr/abl mRNA and oncoprotein.
Cell lines of myeloid origin have been shown to express interleukin-2 receptors (IL-2R). Here, we demonstrate the expression of IL-2R alpha and IL-R beta on the CML blast cell line K562 by FACS analysis and cross-linking assay. Furthermore, we examined the effect of IL-2 on leukemic progenitor growth, employing K562 as a model. Clonogenic growth was assessed after 3 days of culture by colony formation in a serum-free, semi-solid assay system. IL-2 was found to exhibit a dose-dependent suppressive effect on K562 clonogenicity with 48% inhibition of colony formation at 250 U IL-2 and 60% inhibition at 1000 U IL-2. Philadelphia chromosome (Ph)-positive K562 cells possess multiple copies of the bcr/abl fusion gene whose transcript and protein product (p210) is thought to confer growth advantage to CML cells. We therefore investigated IL-2-dependent modulation of bcr/abl mRNA accumulation and p210 protein levels in K562 cells. After 4 h of culture in the presence of IL-2, a 3-15-fold reduction of bcr/abl mRNA accumulation was demonstrated by competitive reverse PCR. Reduction of bcr/abl fusion protein levels was demonstrated at 24 h of IL-2-supplemented cell culture, employing p210 recognizing monoclonal antibodies (mAbs) in FACS analysis. Levels of proliferation marker Ki67 were only marginally affected. We conclude: (1) K562 cells express both IL-2R alpha and IL-R beta; (2) IL-2 inhibits clonogenic growth of K562 in a dose-dependent manner; and (3) IL-2-mediated inhibition of K562 proliferation is preceded by a reduction of bcr/abl mRNA accumulation and p210 protein levels.
Dilloo
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Bone Marrow Transplantation Programme, Heinrich Heine-University Medical Center, Düsseldorf, Germany.
Hanenberg
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Lion
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Burdach
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D001483:Base Sequence; D001752:Blast Crisis / Q000473:pathology*; D002455:Cell Division / Q000187:drug effects; D003864:Depression, Chemical; D016044:Fusion Proteins, bcr-abl / Q000096:biosynthesis* / Q000235:genetics; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects*; D006801:Humans; D007376:Interleukin-2 / Q000494:pharmacology*; D019394:Ki-67 Antigen; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000473:pathology*; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D014411:Neoplastic Stem Cells / Q000187:drug effects*; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis*; D012334:RNA, Neoplasm / Q000096:biosynthesis*; D015375:Receptors, Interleukin-2 / Q000096:biosynthesis / Q000235:genetics; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay
D007376:Interleukin-2; D019394:Ki-67 Antigen; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D015375:Receptors, Interleukin-2; D016044:Fusion Proteins, bcr-abl