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Open Access Research

Indoleamine 2,3-dioxygenase 1 (IDO1) activity correlates with immune system abnormalities in multiple myeloma

Giuseppina Bonanno1, Andrea Mariotti1, Annabella Procoli1, Valentina Folgiero2, Daniela Natale1, Luca De Rosa3, Ignazio Majolino3, Linda Novarese4, Alberto Rocci5, Manuela Gambella5, Marilena Ciciarello6, Giovanni Scambia1, Antonio Palumbo5, Franco Locatelli27, Raimondo De Cristofaro4 and Sergio Rutella2*

Author Affiliations

1 Department of Gynecology, Catholic University Med. School, Rome, Italy

2 Department of Pediatric Hematology/Oncology, IRCCS Bambino Gesù Children’s Hospital, Rome, Italy

3 Department of Hematology, Azienda Ospedaliera “S. Camillo-Forlanini”, Rome, Italy

4 Department of Medicine, Hemostasis Research Centre, Catholic University Med. School, Rome, Italy

5 Myeloma Unit, Division of Hematology, University of Turin, AOU S. Giovanni Battista, Turin, Italy

6 Institute of Hematology and Medical Oncology “L.&A. Seràgnoli”, University of Bologna, Bologna, Italy

7 University of Pavia, Pavia, Italy

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Journal of Translational Medicine 2012, 10:247  doi:10.1186/1479-5876-10-247

Published: 11 December 2012

Abstract

Background

Multiple myeloma (MM) is a plasma cell malignancy with a multifaceted immune dysfunction. Indoleamine 2,3-dioxygenase 1 (IDO1) degrades tryptophan into kynurenine (KYN), which inhibits effector T cells and promote regulatory T-cell (Treg) differentiation. It is presently unknown whether MM cells express IDO1 and whether IDO1 activity correlates with immune system impairment.

Methods

We investigated IDO1 expression in 25 consecutive patients with symptomatic MM and in 7 patients with either monoclonal gammopathy of unknown significance (MGUS; n=3) or smoldering MM (SMM; n=4). IDO1-driven tryptophan breakdown was correlated with the release of hepatocyte growth factor (HGF) and with the frequency of Treg cells and NY-ESO-1-specific CD8+ T cells.

Results

KYN was increased in 75% of patients with symptomatic MM and correlated with the expansion of CD4+CD25+FoxP3+ Treg cells and the contraction of NY-ESO-1-specific CD8+ T cells. In vitro, primary MM cells promoted the differentiation of allogeneic CD4+ T cells into bona fide CD4+CD25hiFoxP3hi Treg cells and suppressed IFN-γ/IL-2 secretion, while preserving IL-4 and IL-10 production. Both Treg expansion and inhibition of Th1 differentiation by MM cells were reverted, at least in part, by D,L-1-methyl-tryptophan, a chemical inhibitor of IDO. Notably, HGF levels were higher within the BM microenvironment of patients with IDO+ myeloma disease compared with patients having IDO- MM. Mechanistically, the antagonism of MET receptor for HGF with SU11274, a MET inhibitor, prevented HGF-induced AKT phosphorylation in MM cells and translated into reduced IDO protein levels and functional activity.

Conclusions

These data suggest that IDO1 expression may contribute to immune suppression in patients with MM and possibly other HGF-producing cancers.