Prognostic Significance of WT1 mRNA and Anti-WT1 Antibody Levels in Peripheral Blood in Patients with Myelodysplastic Syndromes.

Abstract 3821

Poster Board III-757

(INTRODUCTION) The Wilms tumor gene (WT1) message is overexpressed in tumor cells from various solid cancers as well as hematologic malignancies including myelodysplastic syndromes (MDS). We reported previously that WT1 mRNA expression in peripheral blood mononuclear cells (PBMCs) as well as bone marrow (BM) cells increased with the aggressiveness of MDS disease subtype as defined by the French-American-British (FAB) classification and that a humoral immune response, IgG- or IgM-type anti-WT1 antibody (Ab) expression, was detected in sera from most MDS patients. In this study, we investigated whether WT1 mRNA expression and anti-WT1 Ab titers in PB were associated with prognosis in MDS patients by examining their long-term follow-up data. (METHODS AND RESULTS) (1) WT1 mRNA expression in PBMCs was examined in 80 patients: 35 with refractory anemia (RA); 5 with RA with ringed sideroblasts (RARS); 24 with RA with excess blasts (RAEB); 5 with RAEB in transformation (RAEB-t); and 11 with acute myeloid leukemia transformed from MDS (AML-MDS). Levels of WT1 mRNA expression were assessed using the real-time quantitative polymerase chain reaction [Tamaki H, et al, Leukemia 1999]. WT1 mRNA levels increased with the aggressiveness of disease subtype (mean: RA, 220.9; RARS, 129.4; RAEB, 5,554.3; RAEB-t, 14,284.0; AML-MDS, 56,272.7 copies/μg) and with the aggressiveness of the International Prognostic Scoring System (IPSS) category (mean: low, 114.5; intermediate-1, 360.8; intermediate-2, 12,041.6; high, 7,357.9 copies/μg) in these patients. (2) IgG- and IgM-type anti-WT1 Ab titers were determined using the dot-blot assay [Elisseeva OA, Blood 2002] in sera from 45 of the 80 patients: 15 RA; 3 RARS; 18 RAEB; 3 RAEB-t; and 6 AML-MDS. IgM and IgG WT1 Abs were detected in 31 (79.5%) and 34 (87.2%) MDS patients, and 5 (83.3%) and 6 (100%) AML-MDS patients, respectively. WT1 Abs levels were not correlated with FAB subtype, IPSS, or WT1 mRNA expression in PBMCs. (3) When patients were divided into three groups based on the WT1 mRNA level (fewer than 100 copies/μg, 100 to 10,000 copies/μg, and more than 10,000 copies/μg), their survival rates differed significantly (P = 0.0186): survival was worse in those with increased WT1 mRNA levels. Specifically, a high WT1 mRNA level was a strong predictor of rapid AML transformation even if adjusted by the IPSS (P = 0.0005). Furthermore, patients with high levels of either IgM or IgG WT1 Abs had significantly better survival compared with those whose IgM and IgG WT1 Abs values were both low (P = 0.0007) even when adjusted by the IPSS (P = 0.0019). (CONCLUSIONS) This study showed for the first time that high WT1 mRNA expression and high WT1 Ab titers in PB affected the prognosis of MDS patients negatively and positively, respectively, suggesting that an optimal immune response against WT1 may beneficial. Recently, clinical trials of WT1 peptide-based immunotherapy have been conducted for various malignancies including MDS. Our data presented here may provide a rationale for anti-WT1 immunotherapy in MDS.