Insulin and IGF-1 increase mitogenesis and glucose metabolism in the multiple myeloma cell line, RPMI 8226.
Insulin receptors and insulin-like growth factor-1 (IGF-1) receptors are present in circulating human B lymphocytes (B cells) and certain B cell malignancies, but no function has been attributed to either receptor. We report a human myeloma cell line, RPMI 8226, that exhibits insulin and IGF-1-dependent receptor and substrate tyrosine phosphorylation as well as hormone-responsive cellular metabolism. Competitive hormone-binding analysis revealed that the cell line expressed approximately 4 x 10(3) high affinity insulin binding sites and 1.1 x 10(4) high affinity IGF-1 binding sites per cell. The Kd of the insulin-binding sites for insulin was 0.32 nM. The Kd of high affinity IGF-1 binding sites for IGF-1 was 0.89 nM. Insulin receptor autophosphorylation was maximum at 200 nM as was tyrosine phosphorylation of the 180-kDa cytosolic receptor substrate. Insulin-dependent activation of phosphatidylinositol 3-kinase paralleled receptor phosphorylation. In contrast, IGF-1 produced its maximum effects at 200 nM for receptor phosphorylation and 20 nM for substrate phosphorylation and PI 3-kinase activation. In growth synchronized cells, IGF-1 and insulin at 200 nM increased DNA synthesis by 122 +/- 18% and 101 +/- 27%, respectively. IGF-1 increased DNA synthesis 88 +/- 21% at 2 nM and the effect of insulin at 2 nM was 34 +/- 12%. Flux through the glycolytic pathway was also increased by insulin and IGF-1. At 200 and 2 nM, insulin increased production of lactate by 33 +/- 9% and 19 +/- 11%, respectively. IGF-1 increased lactate production 47 +/- 3% and 23 +/- 3% at identical hormone concentrations. Finally, in two additional myeloma cell lines, U266 (human) and Ag8.653 (mouse), insulin and IGF-1 increased tyrosine phosphorylation of receptor beta-subunit (95 kDa), the prominent 180-kDa substrate (pp185), and several other substrates. Thus, functional insulin and IGF-1 receptors are present in myeloma cell lines. Through these receptors, insulin and IGF-1 regulate mitogenesis and glucose metabolism, and may be important in potentiating plasma cell malignancy.
Freund
G G
GG
Department of Pathology and Laboratory Medicine, University of Rochester School of Medicine and Dentistry, NY 14642.
Kulas
D T
DT
Mooney
R A
RA
D005947:Glucose / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007773:Lactates / Q000378:metabolism; D008938:Mitosis / Q000187:drug effects*; D009101:Multiple Myeloma / Q000378:metabolism* / Q000473:pathology*; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism; D019000:Phosphotyrosine; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D011972:Receptor, Insulin / Q000378:metabolism; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
D007328:Insulin; D007773:Lactates; D010750:Phosphoproteins; D019000:Phosphotyrosine; D014443:Tyrosine; D007334:Insulin-Like Growth Factor I; D010770:Phosphotransferases; D019869:Phosphatidylinositol 3-Kinases; D017526:Receptor, IGF Type 1; D011972:Receptor, Insulin; D005947:Glucose