Rabbit Anti-WT1 Monoclonal antibody, clone DBO-S0(JID)-67-3

Disease relapse from standard chemotherapy in acute myeloid leukemia (AML) is poorly understood. The importance of protein phosphatase 2A (PP2A) as an AML tumor suppressor is emerging. Therefore, here, we examined the potential role of endogenous PP2A inhibitor proteins as biomarkers predicting AML relapse in a standard patient population by using three independent patient materials: cohort1 (n = 80), cohort2 (n = 48) and The Cancer Genome Atlas Acute Myeloid Leukemia (TCGA LAML) dataset (n = 160). Out of the examined PP2A inhibitors (CIP2A, SET, PME1, ARPP19 and TIPRL), expression of ARPP19 mRNA was found to be independent of the current AML risk classification. Functionally, ARPP19 promoted AML cell viability and expression of oncoproteins MYC, CDK1, and CIP2A. Clinically, ARPP19 mRNA expression was significantly lower at diagnosis (p = 0.035) in patients whose disease did not relapse after standard chemotherapy. ARPP19 was an independent predictor for relapse both in univariable (p = 0.007) and in multivariable analyses (p = 0.0001) and gave additive information to EVI1 expression and risk group status (additive effect, p = 0.005). Low ARPP19 expression was also associated with better patient outcome in the TCGA LAML cohort (p = 0.019). In addition, in matched patient samples from diagnosis, remission and relapse phases, ARPP19 expression was associated with disease activity (p = 0.034), indicating its potential usefulness as a minimal residual disease (MRD) marker. Together, these data demonstrate the oncogenic function of ARPP19 in AML and its risk group independent role in predicting AML patient relapse tendency.

Wilms' tumor suppressor protein WT1 regulates the expression of multiple genes through binding of the Cys(2)-His(2) zinc finger domain to promoter sites. WT1 has also been proposed to be involved in post-transcriptional regulation, by binding to RNA using the same set of zinc fingers. WT1 has two major splice variants, where the Lys-Thr-Ser (KTS) tripeptide is inserted into the linker between the third and fourth zinc fingers. To obtain insights into the mechanism by which the different WT1 splice variants recognize both DNA and RNA, we have determined the solution structure of the WT1 (-KTS) zinc finger domain in complex with a 29mer stem-loop RNA. Zinc fingers 1-3 bind in a widened major groove favored by the presence of a bulge nucleotide in the double-stranded helical stem. Fingers 2 and 3 make specific contacts with the nucleobases in a conserved AUGG sequence in the helical stem. Nuclear magnetic resonance chemical shift mapping and relaxation analysis show that fingers 1-3 of the two splice variants (-KTS and +KTS) of WT1 form similar complexes with RNA. Finger 4 of the -KTS isoform interacts weakly with the RNA loop, an interaction that is abrogated in the +KTS isoform, and both isoforms bind with similar affinity to the RNA. In contrast, finger 4 is required for high-affinity binding to DNA and insertion of KTS into the linker of fingers 3 and 4 abrogates DNA binding. While finger 1 is required for RNA binding, it is dispensable for binding to consensus DNA sites.