Metformin reduces the clonal fitness of Dnmt3aR878H hematopoietic stem and progenitor cells by reversing their aberrant metabolic and epigenetic state.

Clonal hematopoiesis (CH) arises when a hematopoietic stem cell (HSC) acquires a mutation that confers a competitive advantage over wild-type (WT) HSCs, resulting in its clonal expansion. Individuals with CH are at an increased risk of developing hematologic neoplasms and a range of age-related inflammatory illnesses1-3. Therapeutic interventions that suppress the expansion of mutant HSCs have the potential to prevent these CH-related illnesses; however, such interventions have not yet been identified. The most common CH driver mutations are in the DNA methyltransferase 3 alpha (DNMT3A) gene with arginine 882 (R882) being a mutation hotspot. Here we show that murine hematopoietic stem and progenitor cells (HSPCs) carrying the Dnmt3aR878H/+ mutation, which is equivalent to human DNMT3AR882H/+, have increased mitochondrial respiration compared with WT cells and are dependent on this metabolic reprogramming for their competitive advantage. Importantly, treatment with metformin, an oral anti-diabetic drug with inhibitory activity against complex I in the electron transport chain (ETC), reduced the fitness of Dnmt3aR878H/+ HSCs. Through a multi-omics approach, we discovered that metformin acts by enhancing the methylation potential in Dnmt3aR878H/+ HSPCs and reversing their aberrant DNA CpG methylation and histone H3K27 trimethylation (H3K27me3) profiles. Metformin also reduced the fitness of human DNMT3AR882H HSPCs generated by prime editing. Our findings provide preclinical rationale for investigating metformin as a preventive intervention against illnesses associated with DNMT3AR882 mutation-driven CH in humans.

Efficacy and feasibility of 3D printed redesigned Venezia™ applicator for treating advanced cervix and recurrent endometrial cancer.

PURPOSE: Venezia™ is an interstitial brachytherapy applicator for treating advanced cervical and vaginal vault recurrent cancer. However, there are limitations that lead to suboptimal target coverage. 3D printing introduction allows the redesign of Venezia™ for bulky and irregular-shaped tumors. METHODS: This study first describes three new designs included: 1) add-on needles template allowed for an extra layer of straight and oblique needles, 2) redesigned vaginal cap so straight and oblique needles can be used together and 3) redesigned central tube allowed vaginal vault interstitial needle insertion. Drawbacks to original Venezia™ and rationale for using these new designs were discussed. Dosimetric analysis by comparing the original Venezia™ with new design for 10 cases in Oncentra treatment planning system v4.5 (Elekta, Stockholm, Sweden) to observe the dose differences in gross tumor volume (GTV), high risk clinical target volume (HRCTV), intermediate clinical target volume (IRCTV) and organs at risk. RESULTS: For the dosimetric comparison, there were statistically significantly increased median minimal dose to 98% (D98%) of GTV, 90% (D90%) of HRCTV, and IRCTV for the new design with p-value of 0.008, 0.005 and 0.0018, respectively. Comparing the physical dose of D98% of GTV, D90% of HRCTV, and IRCTV when using the new design, it averagely increased by 11.7%, 8.0%, 19.4%, respectively per fraction. CONCLUSIONS: Dosimetric comparison revealed the new designs increased the dose to GTV, HRCTV and IRCTV and fulfilled the dose constraints of bladder, rectum and sigmoid. The 3D printed new design is biocompatible, inexpensive and can be patient specific.

Dosimetric benefits of 3D-printed modulated electron bolus following lumpectomy and whole-breast radiotherapy for left breast cancer.

Radiotherapy with electrons is commonly applied to the tumor bed after whole-breast radiotherapy following breast conservation surgery for breast cancer patients. However, the radiation dose to adjacent organs-at-risk (OARs) and conformity of planning target volume (PTV) cannot be optimized. In this study, we examine the feasibility of using modulated electron bolus (MEB) to improve PTV conformity and reduce the dose to these OARs. Twenty-seven patients with left breast cancer were retrospectively selected in this study. For each patient, a tangential photon plan in RayStation treatment planning system with prescription of 26 Gy in 5 fractions was created as base plan. Two electron plans, one without bolus and one with MEB using Adaptiiv software based on the PTV were created. Various dosimetric parameters of OARs including left lung, heart, left anterior descending artery (LAD) and ribs and the conformity indices of PTV of these 2 electron plans together with the base plans were compared. Statistically significant decreases in the dosimetric parameters (V5Gy, V10Gy, V20Gy, and mean dose) of the ipsilateral left lung and the heart were observed with MEB. The median maximum dose to the LAD and the ribs decreased by 6.2% and 4.5% respectively. The median conformity index was improved by 14.3% with median increases of monitor units by 1.7%. Our results show that MEB is feasible resulting in reduction of doses to the predefined OARs and an improved conformity of PTV. By using 3D printing, MEB might be considered as an alternative to conventional electron boost.

Targeting STAT5 Signaling Overcomes Resistance to IDH Inhibitors in Acute Myeloid Leukemia through Suppression of Stemness.

Mutant isocitrate dehydrogenase 1 (IDH1) and IDH2 block the differentiation of acute myeloid leukemia (AML) cells through production of R-2-hydroxyglutarate (R-2-HG). IDH inhibitors can induce differentiation of AML cells by lowering R-2-HG but have limited clinical efficacy as single agents. Here, we performed a genome-wide CRISPR knockout screen in an Idh1-mutated hematopoietic progenitor cell line to identify genes that increased the differentiation response to ivosidenib, an IDH1 inhibitor. The screen identified C-type lectin member 5a (Clec5a), which encodes a spleen tyrosine kinase (SYK)-coupled surface receptor, as one of the top hits. Knockout of Clec5a and Syk rendered cells more sensitive to ivosidenib-induced differentiation through a reduction in STAT5-dependent expression of stemness-related genes, including genes in the homeobox (HOX) family. Importantly, direct inhibition of STAT5 activity was sufficient to increase the differentiation response to IDH inhibitors in primary human IDH1- and IDH2-mutated AML cells, including those harboring mutations in receptor tyrosine kinase (RTK) and MAPK genes that have been linked to drug resistance. In patient-derived xenograft models of IDH1-mutated AML, combination treatment with ivosidenib and the STAT5 inhibitor pimozide was superior to each agent alone in inducing differentiation in leukemic cells without compromising normal hematopoiesis. These findings demonstrate that STAT5 is a critical mediator of resistance to IDH inhibitors and provide the rationale for combining STAT5 and IDH inhibitors in the treatment of IDH-mutated AML. SIGNIFICANCE: A CRISPR knockout screen identifies a mechanism of resistance to IDH inhibitors in AML involving activated STAT5 signaling, suggesting a potential strategy to improve the clinical efficacy of IDH inhibitors.

SARS-CoV-2 impairs interferon production via NSP2-induced repression of mRNA translation.

Viruses evade the innate immune response by suppressing the production or activity of cytokines such as type I interferons (IFNs). Here we report the discovery of a mechanism by which the SARS-CoV-2 virus coopts an intrinsic cellular machinery to suppress the production of the key immunostimulatory cytokine IFN-ß. We reveal that the SARS-CoV-2 encoded nonstructural protein 2 (NSP2) directly interacts with the cellular GIGYF2 protein. This interaction enhances the binding of GIGYF2 to the mRNA cap-binding protein 4EHP, thereby repressing the translation of the Ifnb1 mRNA. Depletion of GIGYF2 or 4EHP significantly enhances IFN-ß production, which inhibits SARS-CoV-2 replication. Our findings reveal a target for rescuing the antiviral innate immune response to SARS-CoV-2 and other RNA viruses.