miR-2909-mediated regulation of KLF4: a novel molecular mechanism for differentiating between B-cell and T-cell pediatric acute lymphoblastic leukemias

Abstract

BackgroundmicroRNAs (miRNAs) play both oncogenic and oncostatic roles in leukemia. However, the molecular details underlying miRNA-mediated regulation of their target genes in pediatric B- and T-cell acute lymphoblastic leukemias (ALLs) remain unclear. The present study investigated the relationship between miR-2909 and Kruppel-like factor 4 (KLF4), and its functional relevance to cell cycle progression and immortalization in patients with pediatric ALL.MethodsElevated levels of miR-2909 targeted the tumor suppressor gene KLF4 in pediatric B-cell, but not pediatric T-cell ALL, as detected by pMIR-GFP reporter assay. Expression levels of genes including apoptosis-antagonizing transcription factor (AATF), MYC, B-cell lymphoma (BCL3), P21 CIP , CCND1 and SP1 in B- and T-cells from patients with pediatric ALL were compared with control levels using real-time quantitative reverse transcription polymerase chain reaction, western blotting, and reporter assays.ResultsWe identified two novel mutations in KLF4 in pediatric T-ALL. A mutation in the 3′ untranslated region of the KLF4 gene resulted in loss of miR-2909-mediated regulation, while mutation in its first or third zinc-finger motif (Zf1/Zf3) rendered KLF4 transcriptionally inactive. This mutation was a frameshift mutation resulting in alteration of the Zf3 motif sequence in the mutant KLF4 protein in all pediatric T-ALL samples. Homology models, docking studies and promoter activity of its target gene P21 CIP confirmed the lack of function of the mutant KLF4 protein in pediatric T-ALL. Moreover, the inability of miR-2909 to regulate KLF4 and its downstream genes controlling cell cycle and apoptosis in T-cell but not in B-ALL was verified by antagomiR-2909 transfection. Comprehensive sequence analysis of KLF4 identified the predominance of isoform 1 (~55 kDa) in most patients with pediatric B-ALL, while those with pediatric T-ALL expressed isoform 2 (~51 kDa).ConclusionsThis study identified a novel miR-2909-KLF4 molecular axis able to differentiate between the pathogeneses of pediatric B- and T-cell ALLs, and which may represent a new diagnostic/prognostic marker.

AATF Genome: Evolution of Allorecognition

“…The salient features of the phenomenon (Figure 2)( are supported by the recent findings that reveal as to how human cells respond to high glucose or arsenic threat [31,66]. Further, deregulation of KLF4 expression also ensures restricted AATF-dependant control upon the p53-induced cellular apoptosis and autophagy [28,67]. Hence, cellular deregulated miR-2909 RNomics creates a situation that favours autoimmune response in tissue-specific/localized manner.…”

RETRACTED: miR-664 negatively regulates PLP2 and promotes cell proliferation and invasion in T-cell acute lymphoblastic leukaemia

“…Many miRNAs, e.g. miR-2909 [4], miRNA-193b-3p [5], miRNA-128-3p [6] and miRNA-100/99a [7], are found to play roles in the carcinogenesis of T-ALL.…”

Mitochondrial uncoupling protein (UCP2) gene expression is regulated by miR-2909

“…It is in this context the results reported here assume importance. Recent findings have established that AATF genome encoded miR-2909 not only requires nuclear RelA translocation for its expression but also this microRNA regulates gene expression through repression of KLF4 gene expression resulting in the up-regulation of SP1 gene expression [7,8]. At this stage, it is pertinent to note that: a) SP1 has been shown to induce genes coding for AATF, CCL5 and p53 [13][14][15]; b) p53 gene expression is also induced by CCL5 and AATF-dependent translocation of RelA to p53 gene promoter [6,16]; c) KLF4 has been shown to induce IL-17 gene expression [12] and p53 binds RelA to block its translocation either to nucleus or mitochondria [4]; d) KLF4 is known to repress Bmi-1 gene which is known to degrade the p53 protein [17,18].…”

“…In this context, it is interesting to note that AATF was not only shown to ameliorate mitochondrial dysfunction coupled with accumulation of superoxide/peroxynitrite [5] but also had the capacity to induce p53 expression through its interaction with RelA [6]. AATF genome is also assumed to be important because of its ability to encode a microRNA designated as miR-2909 which was shown to regulate not only a large number of genes through the repression of KLF4 translational expression but also nuclear translocation of RelA which was crucial for inducing its expression [7,8]. Consequently, the present study was addressed to understand four specific issues: a) What type of regulatory link that may exist between AATF genome and its encoded miR-2909?…”