Adult T‐cell leukemia‐lymphoma (ATL) is an aggressive neoplasm derived from T‐cells transformed by human T‐cell lymphotropic virus‐1 (HTLV‐1). Recently, we reported that regional DNA hypermethylation in HTLV‐1‐infected T‐cells reflects the disease status of ATL and the anti‐ATL effects of DNA demethylating agents, including azacitidine (AZA), decitabine (DAC) and a new DAC prodrug, OR‐2100 (OR21), which we developed. Here, to better understand the mechanisms underlying drug resistance, we generated AZA‐, DAC‐ and OR21‐resistant (AZA‐R, DAC‐R and OR21‐R, respectively) cells from the ATL cell line TL‐Om1 and the HTLV‐1‐infected cell line MT‐2 via long‐term drug exposure. The efficacy of OR21 was almost the same as that of DAC, indicating that the pharmacodynamics of OR21 were due to release of DAC from OR21. Resistant cells did not show cellular responses observed in parental cells induced by treatment with drugs, including growth suppression, depletion of DNA methyltransferase DNMT1 and DNA hypomethylation. We also found that reduced expression of deoxycytidine kinase (DCK) correlated with lower susceptibility to DAC/OR21 and that reduced expression of uridine cytidine kinase2 (UCK2) correlated with reduced susceptibility to AZA. DCK and UCK2 catalyze phosphorylation of DAC and AZA, respectively; reconstitution of expression reversed the resistant phenotypes. A large homozygous deletion in DCK and a homozygous splice donor site mutation in UCK2 were identified in DAC‐R TL‐Om1 and AZA‐R TL‐Om1, respectively. Both genomic mutations might lead to loss of protein expression. Thus, inactivation of UCK2 and DCK might be a putative cause of phenotypes that are resistant to AZA and DAC/OR21, respectively.

DNA methyltransferase inhibitors have improved the prognosis of myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). However, because these agents are easily degraded by cytidine deaminase (CDA), they must be administered intravenously or subcutaneously. Recently, two orally bioavailable DNA methyltransferase inhibitors, CC-486 and ASTX727, were approved. In previous work, we developed 5-O-trialkylsilylated decitabines that resist degradation by CDA.However, the effects of silylation of a deoxynucleotide analog and enzymatic cleavage of silylation have not been fully elucidated. Enteric administration of OR21 in a cynomolgus monkey model led to high plasma concentrations and hypomethylation, and in a mouse model, oral administration of enteric-coated OR21 led to high plasma concentrations. The drug became biologically active after release of decitabine (DAC) from OR21 following removal of the 5'-O-trisilylate substituent. Toxicities were tolerable and lower than those of DAC. Transcriptome and methylome analysis of MDS and AML cell lines revealed that OR21 increased expression of genes associated with tumor suppression, cell differentiation, and immune system processes by altering regional promoter methylation, indicating that these pathways play pivotal roles in the action of hypomethylating agents. OR21 induced cell differentiation via upregulation of the late cell differentiation drivers CEBPE and GATA-1. Thus, silylation of a deoxynucleotide analog can confer oral bioavailability without new toxicities. Both in vivo and in vitro, OR21 exerted anti-leukemia effects, and had a better safety profile

Adult T-cell leukemia/lymphoma (ATL) is a malignancy of mature CD4+ T cells caused by human T-cell lymphotropic virus type 1 (HTLV-1)-induced T-cell transformation. Following infection with HTLV-1, it takes several decades for HTLV-1 carriers to develop ATL. The prognosis of ATL remains poor despite several new agents are approved in the last few years. Recently, it has been noted that epigenetic abnormalities both DNA methylation and tri-methylation at histone H3Lys27 (H3K27me3) contribute to ATL leukemogenesis. Here, we investigated the effect of combination treatment with DNA demethylating agents (azacytidine (AZA), decitabine (DAC), and OR-2100 (OR21), which is silylated derivative of decitabine) and inhibitors of enhancer of zeste homolog 2 (EZH2) (EPZ-6438 and DS-3201b) which catalyze trimethylation of H3K27, in ATL. The combination of DAC and OR21 but not AZA with EZH inhibitors exhibited synergistic anti-ATL effects in vitro and in vivo concomitant with DNA demethylation and reduction of H3K27me3. The combination induced gene expression reprogramming. Dual-specificity phosphatase 5 (DUSP5), an ERK-specific phosphatase, was identified as a key molecule that mediated the inhibitory effect of combination treatment by inactivating the ERK signaling pathway. DUSP5 was downregulated by DNA methylation and H3K27me3 accumulation in the promoter region in HTLV-1-infected cells from ATL patients during ATL leukemogenesis. The present results demonstrate that dual targeting of aberrant DNA and histone methylation synergistically suppresses tumor cell growth by restoring DUSP5, and the dual targeting of aberrant DNA and histone methylation is a feasible therapeutic approach for ATL.

The standard treatment for elderly patients with acute myeloid leukemia (AML) is venetoclax (Ven), a BCL-2 selective inhibitor, combined with hypomethylating agents (HMAs) such as azacitidine (AZA) or decitabine (DAC). This regimen results in low toxicity, high response rates, and potentially durable remission; however, because of low oral bioavailability, these conventional HMAs must be administered intravenously or subcutaneously. A combination of oral HMAs and Ven would provide a therapeutic advantage over parenteral administration of drugs and improve quality of life by reducing the number of hospital visits. Previously, we showed the promising oral bioavailability and anti-leukemia effects of a new HMA, OR2100 (OR21). Here, we investigated the efficacy and underlying mechanism of OR21 when used in combination with Ven to treat AML. OR21/Ven showed synergistic anti-leukemia effects in vitro, and significantly prolonged survival without increasing toxicity in a human leukemia xenograft mice model. RNA sequencing following combination therapy revealed downregulation of VAMP7, which is involved in autophagic maintenance of mitochondrial homeostasis. Combination therapy led to accumulation of reactive oxygen species, leading to increased apoptosis. The data suggest that the combination of OR21 plus Ven is a promising candidate oral therapy for AML.

Rationale Ecthyma gangrenosum (EG) is an uncommon cutaneous infection usually associated with Pseudomonas aeruginosa bacteremia in immunocompromised patients, particularly those with underlying malignant diseases. Despite its rarity, especially in immunocompetent or nondiagnosed immunodeficiency patients, EG can present as the first manifestation of an underlying immunosuppression. Patient concerns A 42-year-old Japanese man was admitted to our hospital with a 3-day history of a painless red macule on his right forearm and fever. Diagnoses Blood culture on admission revealed the presence of Pseudomonas aeruginosa , whereas pus culture of the skin lesion showed Pseudomonas aeruginosa and methicillin-susceptible Staphylococcus aureus positivity. Interventions Additional bone marrow aspirate examination and immunophenotyping were performed to confirm the diagnosis of acute promyelocytic leukaemia with PML-retinoic acid alpha receptor. Outcomes The patient was successfully treated with a 14-day course of antibiotics, and no evidence of relapse was noted. The patient achieved complete remission after treatment for acute promyelocytic leukaemia. Lessons It should be kept in mind that EG is an important cutaneous infection that is typically associated with P aeruginosa bacteremia and the presence of underlying immunodeficiency, such as acute leukaemia.