tRNA and tsRNA: From Heterogeneity to Multifaceted Regulators.

As the most ancient RNA, transfer RNAs (tRNAs) play a more complex role than their constitutive function as amino acid transporters in the protein synthesis process. The transcription and maturation of tRNA in cells are subject to stringent regulation, resulting in the formation of tissue- and cell-specific tRNA pools with variations in tRNA overall abundance, composition, modification, and charging levels. The heterogeneity of tRNA pools contributes to facilitating the formation of histocyte-specific protein expression patterns and is involved in diverse biological processes. Moreover, tRNAs can be recognized by various RNase under physiological and pathological conditions to generate tRNA-derived small RNAs (tsRNAs) and serve as small regulatory RNAs in various biological processes. Here, we summarize these recent insights into the heterogeneity of tRNA and highlight the advances in the regulation of tRNA function and tsRNA biogenesis by tRNA modifications. We synthesize diverse mechanisms of tRNA and tsRNA in embryonic development, cell fate determination, and epigenetic inheritance regulation. We also discuss the potential clinical applications based on the new knowledge of tRNA and tsRNA as diagnostic and prognostic biomarkers and new therapeutic strategies for multiple diseases.

[Safety and the Short-Term Efficacy of Venetoclax Combined with Azacitidine Followed by Cladribine in Children with Refractory/Relapsed Acute Myeloid Leukemia].

OBJECTIVE: To investigate the safety and the short-term efficacy of venetoclax combined with azacitidine followed by cladribine (VAC regimen) in children with refractory/ relapsed acute myeloid leukemia (AML). METHODS: The clinical data, treatment outcomes, complications, and blood product consumption of 6 children with refractory/relapsed AML treated with VAC regimen in the Children's Hospital of Soochow University from August 2021 to December 2021 were retrospectively analyzed. RESULTS: Among the 6 children, there were 1 male and 5 females. 5 cases were refractory AML, and 1 case was relapsed AML, which recurred again 16 months after allogeneic hematopoietic stem cell transplantation. 4 children were accompanied by chromosomes or genes that predicted poor prognosis, such as RUNX1, FLT3-ITD, KMT2A exon 2-exon 8 dup, MLL-AF6, 7q-, KMT2A exon 2-exon 10 dup, etc. After received VAC regimen, 4 cases achieved CR+CRi, 1 case achieved PR (only MRD did not relieve, MRD was 0.59%), and 1 case was NR (but the proportion of bone marrow blasts decreased). All 6 patients had grade Ⅳ neutropenia, and 4 patients had grade Ⅳ thrombocytopenia. During the period of neutropenia, none of the 6 children developed symptoms of infection such as fever, cough, and diarrhea. No treatment-related death occurred. CONCLUSION: Venetoclax combined with azacitidine followed by cladribine provides a new treatment option for patients with relapsed/refractory AML who have poor efficacy in early induction remission theragy, showing good efficacy and safety.

LMO2 promotes the development of AML through interaction with transcription co-regulator LDB1.

One of the characteristics of leukemia is that it contains multiple rearrangements of signal transduction genes and overexpression of non-mutant genes, such as transcription factors. As an important regulator of hematopoietic stem cell development and erythropoiesis, LMO2 is considered an effective carcinogenic driver in T cell lines and a marker of poor prognosis in patients with AML with normal karyotype. LDB1 is a key factor in the transformation of thymocytes into T-ALL induced by LMO2, and enhances the stability of carcinogenic related proteins in leukemia. However, the function and mechanism of LMO2 and LDB1 in AML remains unclear. Herein, the LMO2 gene was knocked down to observe its effects on proliferation, survival, and colony formation of NB4, Kasumi-1 and K562 cell lines. Using mass spectrometry and IP experiments, our results showed the presence of LMO2/LDB1 protein complex in AML cell lines, which is consistent with previous studies. Furthermore, in vitro and in vivo experiments revealed that LDB1 is essential for the proliferation and survival of AML cell lines. Analysis of RNA-seq and ChIP-Seq results showed that LDB1 could regulate apoptosis-related genes, including LMO2. In LDB1-deficient AML cell lines, the overexpression of LMO2 partially compensates for the proliferation inhibition. In summary, our findings revealed that LDB1 played an important role in AML as an oncogene, and emphasize the potential importance of the LMO2/LDB1 complex in clinical treatment of patients with AML.

Severe aplastic anemia patients with infection who received an allogeneic hematopoietic stem cell transplantation had a better chance: Long-term outcomes of a multicenter study.

Background and aims: How to select the treatment is a challenge for the management of acquired patients with infections. This study aimed at comparing the outcomes of SAA with infections who had an allogeneic hematopoietic stem cell transplantation (allo-HSCT)with that of patients who had an infection and received non-HSCT therapy. Methods: We retrospectively compared the outcomes of patients with acquired SAA and infections who had an allo-HSCT (n = 141) with that of patients who had an infection and received non-HSCT therapy (n = 186) between July 2004 and January 2020. Results: The treatment-related mortality (TRM) of grade 1-2 infections in the HSCT and non-HSCT groups was 24.99% and 13.68%, respectively (P = 0.206), while the TRM of grade 3-4 infections was lower in the HSCT group than that observed in the non-HSCT group (18.54% vs. 33.33%, P = 0.036). At 6 months post-treatment, 91.30% patients in the HSCT group and 8.78% patients in the non-HSCT group had achieved a normal blood profile (P < 0.0001). The time required to discontinue transfusions of red blood cells and platelets in the non-HSCT group was longer than in the HSCT group (P < 0.0001). Estimated overall survival (OS) at 6 years was similar in the two groups (75.5% ± 3.9% vs. 76.3% ± 3.1%, P = 0.996), while the estimated failure-free survival (FFS) at 6 years was 75.2% ± 3.8% in the HSCT group and 48.9% ± 3.7% in the non-HSCT group (P < 0.0001). Multivariate analysis showed that younger age, lower grade of infection (grade 1-2), and SAA (vs. very SAA) were favorable factors for OS (P < 0.05), and that the choice of HSCT and younger age were favorable factors for FFS (P < 0.0001). Conclusion: These results suggest that allo-HSCT has a better chance of a successful outcome than non-HSCT in SAA patients with an infection.

SiRNA-Mediated RRM2 Gene Silencing Combined with Cisplatin in the Treatment of Epithelial Ovarian Cancer In Vivo: An Experimental Study of Nude Mice.

Introduction: We aimed to explore small interfering (si)RNA silencing of ribonucleotide reductase M2 (RRM2) gene combined with cisplatin for the treatment of human ovarian cancer in nude mice models of subcutaneous transplantation of tumor cells. Methods: After conventional cultivation of human ovarian cancer cell line SKOV3 in vitro, SKOV3 cells were injected into the right back of nude mice by subcutaneous injection to establish the subcutaneous tumor models. Twenty-four tumor-burdened rats were randomly divided into four groups (n=6): siRNA group, siRNA in combination with cisplatin group, cisplatin group, and control group. Intraperitoneal injection of cisplatin and subcutaneous injection of siRNA were performed weekly. Tumor volume was measured, and tumor growth inhibition rate was calculated. RRM2 expression at the mRNA and protein levels was detected by reverse transcription-polymerase chain reaction and immunohistochemistry. Results: In the siRNA group, the tumor volume and tumor growth inhibition rate were 249.60±20.46 mm³ and 36.39%, respectively. The tumor growth inhibition rate and tumor volume were significantly different between the siRNA and control groups (p<0.05). In the cisplatin group, the tumor volume and tumor growth inhibition rate were 249.86±12.46 mm³ and 41.10%, respectively. The tumor growth inhibition rate and tumor volume were significantly different between the cisplatin and control groups (p<0.05). In the siRNA + cisplatin group, the tumor volume reduced to 180.84±16.25 mm³ and the tumor growth inhibition rate was increased to 64.33%, which were significantly different compared with the control group (p<0.01). Significant downregulation of RRM2 mRNA and protein expression in the tumor tissues was detected by reverse transcription polymerase chain reaction and immunohistochemistry assay (p<0.05). Discussion: siRNA alone or combined with cisplatin can effectively inhibit the growth of human ovarian cancer in nude mice models of subcutaneous transplantation of tumor cells. RRM2 gene silencing may be a potential treatment regimen for ovarian cancer in future.