Therapeutic strategies against hDOT1L as a potential drug target in MLL-rearranged leukemias

DOT1L promotes expression of CD44 through the Wnt/β-catenin signaling pathway in early gastric carcinoma

To assess telomere silencing 1-like (DOTIL) gene expression within gastric cancer (GC) tissues as well as its function of promoting cancer stem cell (CSC)-mediated epithelial-mesenchymal switching, tissue samples from 8 patients each in 3 stages (normal, low-grade intraepithelial neoplasia (LGIN), as well as early gastric carcinoma (EGC)) were collected for whole-exome sequencing, which revealed differentially expressed genes (DEGs). The DEGs and their prognostic value were verified through TCGA and GTEx analyses. We also verified the role of DOT1L in EGC development. We collected samples from three patients each with LGIN and EGC for single-cell sequencing. We conducted single-cell transcriptomic analysis, DEG analysis, cell‒cell interaction analysis, and pseudotime analysis using R language. Sites and levels of DOT1L, CD44 and DOT1L expression were verified by IF. We found 703 deleterious mutation sites in the LGIN group and 389 deleterious mutation sites in the EGC group. The LGIN as well as EGC categories exhibited increased levels of DOT1L expression compared to the standard category (P<0.05) in TCGA and GTEx. DOT1L also correlated significantly with TMB (P=8.45E-06), MSI (P=0.001), and tumor proliferation index (P=7.17E-09) in the TCGA and GTEx datasets. In single cells, we found that DOT1L promotes CD44 expression via the Wnt/β-catenin signaling pathway and the development for stemness properties within GC. In addition, we found that DOT1L, CD44 and CTNNB1 colocalize and correlate positively. In conclusion, one important CSC regulator in GC, DOT1L may be crucial in coordinating the expression of genes specific to a certain lineage during MSC development.

Targeting the undruggable: menin inhibitors ante portas

Acute myeloid leukaemias harbouring a rearrangement of the mixed lineage leukaemia gene (MLL) are aggressive haematopoietic malignancies that relapse early and have a poor prognosis (event-free survival less than 50%). Menin is a tumour suppressor, however, in MLL-rearranged leukaemias it functions as a co-factor which is mandatory for the leukaemic transformation by interaction with the N-terminal part of MLL, which is maintained in all MLL-fusion proteins. Inhibition of menin blocks leukaemogenesis and leads to differentiation and, in turn, to apoptosis of leukaemic blasts. Furthermore, nucleophosmin 1 (NPM1) binds to specific chromatin targets, which are co-occupied by MLL, and menin inhibition has been shown to trigger degradation of mNPM1 resulting in a rapid decrease in gene expression and activating histone modifications. Therefore, disruption of the menin-MLL axis blocks leukaemias driven by NPM1 mutations for which the expression of menin-MLL target genes (e.g., MEIS1, HOX etc.) is essential. To date at least six different menin-MLL inhibitors are undergoing clinical evaluation as first- and second-line monotherapy in acute leukaemias: DS-1594, BMF-219, JNJ-75276617, DSP-5336, revumenib, and ziftomenib, however, only for revumenib and ziftomenib early clinical data have been reported. In the revumenib phase I/II AUGMENT-101 trial (N = 68) with very heavily pretreated AML patients the ORR was 53% with a CR rate of 20%. The ORR in patients harbouring MLL rearrangement of mNPM1 was 59%. Patients who achieved a response had a mOS of 7 months. Similar results have been reported for ziftomenib in the phase I/II COMET-001 trial. ORR was 40% and CRc was 35% in AML patients with mNPM1. However, outcome was worse in AML patients with a MLL rearrangement (ORR 16.7%, CRc 11%). Differentiation syndrome was a notable adverse event. The clinical development of novel menin-MLL inhibitors is well in line with the currently ongoing paradigm shift towards targeted therapies seen in the AML treatment landscape. Moreover, the clinical assessment of combinations of these inhibitors with established therapy options in AML could be the fuel for an improved outcome of MLL/NPM1 patients.

Histone Methyltransferase DOT1L as a Promising Epigenetic Target for Treatment of Solid Tumors

The histone lysine methyltransferase DOT1L (DOT1-like histone lysine methyltransferase) is responsible for the epigenetic regulation of gene expression through specific methylation of lysine79 residue of histone H3 (H3K79) in actively transcribed genes. Its normal activity is crucial for embryonic development and adult tissues functions, whereas its aberrant functioning is known to contribute to leukemogenesis. DOT1L is the only lysine methyltransferase that does not contain a SET domain, which is a feature that allowed the development of selective DOT1L inhibitors that are currently investigated in Phase I clinical trials for cancer treatment. Recently, abnormal expression of this enzyme has been associated with poor survival and increased aggressiveness of several solid tumors. In this review evidences of aberrant DOT1L expression and activity in breast, ovarian, prostate, colon, and other solid tumors, and its relationships with biological and clinical behavior of the disease and response to therapies, are summarized. Current knowledge of the structural basis of DOT1L ability to regulate cell proliferation, invasion, plasticity and stemness, cell cycle progression, cell-to-cell signaling, epithelial-to-mesenchymal transition, and chemoresistance, through cooperation with several molecular partners including noncoding RNAs, is also reviewed. Finally, available options for the treatment of therapeutically challenging solid tumors by targeting DOT1L are discussed.

Synthesis and Profiling of Highly Selective Inhibitors of Methyltransferase DOT1L Based on Carbocyclic C-Nucleosides

Histone methyltransferase DOT1L is an attractive therapeutic target for the treatment of hematological malignancies. Here, we report the design, synthesis, and profiling of new DOT1L inhibitors based on nonroutine carbocyclic C-nucleoside scaffolds. The experimentally observed SAR was found to be nontrivial as seemingly minor changes of individual substituents resulted in significant changes in the affinity to DOT1L. Molecular modeling suggested that these trends could be related to significant conformational changes of the protein upon interaction with the inhibitors. The compounds 22 and (-)-53 (MU1656), carbocyclic C-nucleoside analogues of the natural nucleoside derivative EPZ004777, and the clinical candidate EPZ5676 (pinometostat) potently and selectively inhibit DOT1L in vitro as well as in the cell. The most potent compound MU1656 was found to be more metabolically stable and significantly less toxic in vivo than pinometostat itself.