Development of a highly sensitive method for detection of FLT3D835Y

FLT3 inhibitors induce p53 instability, driven by STAT5/MDM2/p53 competitive interactions in acute myeloid leukemia

FLT3 mutations are present in one third of patients with Acute myeloid leukemia (AML) and stand as an attractive therapeutic target. Although FLT3 inhibitors demonstrate clinical efficacy, the drug resistance remains challenging attributed to multiple mechanisms. In this study, we found that tyrosine kinase inhibitors (TKIs) targeting FLT3 prompt p53 degradation in AML cells with FLT3-ITD through ubiquitination. STAT5 phosphorylation facilitates its nuclear localization, leading to competitive interactions among STAT5, MDM2, and p53. TKIs blocked STAT5 nuclear entry, amplifying MDM2/p53 binding and subsequent p53 degradation. Additionally, STAT5 overexpression inhibited MDM2-mediated p53 ubiquitination, whereas knock-down of STAT5 destabilizes p53. Co-administration of MDM2 inhibitors stabilizes p53 ubiquitination induced by TKIs, enhancing pro-apoptotic effects on AML cells. Moreover, in mice engrafted with AML cells, gilteritinib treatment results in decreased p53 protein levels and the transcriptional repression of downstream genes in leukemia cells, which are mitigated by the co-administration of MDM2 inhibitors. In conclusion, our study shows that FLT3 TKIs impede STAT5 nuclear translocation, strengthening p53/MDM2 interaction and consequent p53 degradation. This finding reveals a novel mechanism of TKIs resistance and indicates a combination of MDM2 inhibitors with TKIs for AML therapy, offering new insights into effective treatment strategies.

Novel method for detecting frequent TERT promoter hot spot mutations in bladder cancer samples

Telomerase reverse transcriptase promoter (TERTp) mutations are frequently targeted tumor markers, however, they reside in regions with high GC content, which poses challenges when examined with simple molecular techniques or even with next-generation sequencing (NGS). In bladder cancer (BC), TERTp mutations are particularly frequent, however, none of the available tools have demonstrated efficacy in detecting TERTp mutations via a simple noninvasive technique. Therefore, we developed a novel PCR-based method for the detection of the two most common TERTp mutations and demonstrated its use for the analysis of BC samples. The developed SHARD-PCR TERTp mutation detection technique requires PCR and restriction digestion steps that are easily implementable even in less well-equipped laboratories. Cell lines with known mutational status were utilized for method development. Matching urine and tumor tissue samples from BC patients were analyzed, and the results were validated by next-generation sequencing. Analysis of eighteen urine and corresponding tumor tissue samples by SHARD-PCR revealed perfect matches in sample pairs, which paralleled the corresponding NGS results: fourteen samples exhibited mutations at the -124 position, two samples showed mutations at the -146 position, and no mutations were detected in two samples. Our study serves as a proof-of-concept and is limited by its small sample size, nonetheless, it demonstrates that SHARD-PCR is a simple, economic and highly reliable method for detecting TERTp mutations, which are common in different cancer types. For bladder cancer, SHARD-PCR can be performed with the use of noninvasive samples and could replace or complement currently used techniques.

miR-221/222 induce instability of p53 By downregulating deubiquitinase YOD1 in acute myeloid leukemia

Acute myeloid leukemia (AML) is a hematological malignancy characterized by the impaired differentiation and uncontrolled proliferation of myeloid blasts. Tumor suppressor p53 is often downregulated in AML cells via ubiquitination-mediated degradation. While the role of E3 ligase MDM2 in p53 ubiquitination is well-accepted, little is known about the involvement of deubiquitinases (DUBs). Herein, we found that the expression of YOD1, among several DUBs, is substantially reduced in blood cells from AML patients. We identified that YOD1 deubiqutinated and stabilized p53 through interaction via N-terminus of p53 and OTU domain of YOD1. In addition, expression levels of YOD1 were suppressed by elevated miR-221/222 in AML cells through binding to the 3' untranslated region of YOD1, as verified by reporter gene assays. Treatment of cells with miR-221/222 mimics and inhibitors yielded the expected effects on YOD1 expressions, in agreement with the negative correlation observed between the expression levels of miR-221/222 and YOD1 in AML cells. Finally, overexpression of YOD1 stabilized p53, upregulated pro-apoptotic p53 downstream genes, and increased the sensitivity of AML cells to FLT3 inhibitors remarkably. Collectively, our study identified a pathway connecting miR-221/222, YOD1, and p53 in AML. Targeting miR-221/222 and stimulating YOD1 activity may improve the therapeutic effects of FLT3 inhibitors in patients with AML.

FLT3-TKD in the prognosis of patients with acute myeloid leukemia: A meta-analysis

Background

Fms-like tyrosine kinase 3 (FLT3) gene mutations occur in approximately 30% of all patients with acute myeloid leukemia (AML). Internal tandem duplication (ITD) in the juxtamembrane domain and point mutations within the tyrosine kinase domain (TKD) are two distinct types of FLT3 mutations. FLT3-ITD has been determined as an independent poor prognostic factor, but the prognostic impact of potentially metabolically related FLT3-TKD remains controversial. Hence, we performed a meta-analysis to investigate the prognostic significance of FLT3-TKD in patients with AML.

Methods

A systematic retrieval of studies on FLT3-TKD in patients with AML was performed in PubMed, Embase, and Chinese National Knowledge Infrastructure databases on 30 September 2020. Hazard ratio (HR) and its 95% confidence intervals (95% CIs) were used to determine the effect size. Meta-regression model and subgroup analysis were used for heterogeneity analysis. Begg's and Egger's tests were performed to detect potential publication bias. The sensitivity analysis was performed to evaluate the stability of findings in meta-analysis.

Results

Twenty prospective cohort studies (n = 10,970) on the prognostic effect of FLT3-TKD in AML were included: 9,744 subjects with FLT3-WT and 1,226 subjects with FLT3-TKD. We found that FLT3-TKD revealed no significant effect on disease-free survival (DFS) (HR = 1.12, 95% CI: 0.90-1.41) and overall survival (OS) (HR = 0.98, 95% CI: 0.76-1.27) in general. However, meta-regressions demonstrated that patient source contributed to the high heterogeneity observed in the prognosis of FLT3-TKD in AML. To be specific, FLT3-TKD represented a beneficial prognosis of DFS (HR = 0.56, 95% CI: 0.37-0.85) and OS (HR = 0.63, 95% CI: 0.42-0.95) for Asians, whereas it represented an adverse prognosis of DFS for Caucasians with AML (HR = 1.34, 95% CI: 1.07-1.67).

Conclusion

FLT3-TKD revealed no significant effects on DFS and OS of patients with AML, which is consistent with the controversial status nowadays. Patient source (Asians or Caucasians) can be partially explained the different effects of FLT3-TKD in the prognosis of patients with AML.

Acute myelogenous leukemia – current recommendations and approaches in molecular-genetic assessment

Acute myelogenous leukemia is a multi-step hematological malignancy, affecting function, growth, proliferation and cell cycle of myeloid precursors. Overall assessment of patients with the disease requires among everything else, a comprehensive investigation of the genetic basis through various methods such as cytogenetic and molecular-genetic ones. This clarification provides diagnostic refinement and carries prognostic and predictive value in respect of essential therapeutic choices.

With this review of the literature, we focus on summarizing the latest recommendations and preferred genetic methods, as well as on emphasizing on their general benefits and limitations. Since none of these methods is actually totipotent, we also aim to shed light over the often-difficult choice of appropriate genetic analyses.