Program: Oral and Poster Abstracts
Session: 636. Myelodysplastic Syndromes – Basic and Translational Studies: Poster III
Methods and results: 1) To investigate the prognostic impact of Gal-9, plasma Gal-9 levels were measured by ELISA in 92 MDS patients: 30 with refractory anemia (RA); 3 with RA with ringed sideroblasts (RARS); 18 with RA with excess blasts (RAEB); 14 with RAEB in transformation (RAEB-t); and 29 with acute leukemia transformed from MDS (AL-MDS). The plasma Gal-9 level increased with disease progression (mean ± SD: control 3.4 ± 0.9; RA, 9.3 ± 5.7; RARS, 10.2 ± 6.8; RAEB, 9.7 ± 6.5; RAEB-t, 17.2 ± 9.6; AML-MDS, 20.1 ± 14.1 ng/ml). Furthermore, patients with AL-MDS in International Prognostic Scoring System (IPSS) high-risk categories (Intermediate-2/High) had significantly higher Gal-9 levels compared with IPSS low-risk (Low/Intermediate-1) patients (Low/Intermediate-1 vs Intermediate-2/High, p = 0.002; Low/Intermediate-1 vs AML-MDS, p = 0.004). The overall survival of MDS patients with plasma Gal-9 higher than the normal level (10 ng/mL) was significantly shorter than that of other patients (log-rank p < 0.001) even in lower-risk (RA, RARS) cases (log-rank p = 0.0369). Moreover, multivariate analysis showed that a high level of Gal-9 was an independent predictor of shorter survival in MDS patients as well as IPSS. 2) Bone marrow mononuclear cells were isolated from some MDS patients, and Tim-3 expression on granulocytes, monocytes, lymphocytes, and blasts was analyzed using flow cytometry (FCM). Tim-3 expression on blasts tended to be higher in AL-MDS patients than in MDS patients. 3) To investigate whether MDS cells can produce Gal-9, we analyzed Gal-9 levels in supernatants of cell cultures of 3 human AL-MDS cell lines, F-36P, SKM-1, and MDS-L, and MDS blasts obtained from an AL-MDS patient by ELISA. Gal-9 was detected in all cell culture supernatants and its concentration was higher when cultured in medium containing 10% fetal bovine serum (FBS) than in 2.5% FBS medium in F-36P and SKM-1 cells. The concentration of Gal-9 produced from MDS blasts was increased time dependently in 2–6 day culture. Furthermore, recombinant human Gal-9 enhanced the cell proliferation of F-36P cells. 4) After analyzing Tim-3 expression in MDS cell lines using real-time quantitative PCR and FCM, all cell lines expressed relatively low levels of Tim-3 mRNA. Extracellular expression of Tim-3 was detected and induced by adding cell culture supernatants of the human stromal cell line HS-5 in F-36P cells. To elucidate the signaling pathway inducing Tim-3 expression, we investigated Tim-3 mRNA expression in F-36P cells treated with HS-5 supernatant with several signal transduction inhibitors (STAT3 inhibitor, U0126; MAPK/ERK; AG490; JAK2, LY294002; PI3K, PDTC; NF-κB inhibitor). Upregulation of Tim-3 gene expression in F-36P cells treated with HS-5 supernatant was inhibited by the MEK inhibitor U0126. These results suggest that the MAPK/ERK pathway is involved in Tim-3 expression induced by HS-5 supernatant.
Conclusions: In MDS, the elevation of plasma Gal-9 levels is associated with disease progression, including leukemic transformation, and with shorter survival. Furthermore, its receptor Tim-3 is upregulated on blasts in AL-MDS patients. Our data suggest that the Gal-9/Tim-3 pathway plays a key role in MDS disease progression. Although further study is required to clarify the detailed functions of the interaction between Gal-9 and Tim-3, the current study could lead to the development of a new immunotherapeutic strategy via the blockade of this pathway in MDS.
Disclosures: No relevant conflicts of interest to declare.
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