Song Li

3,5-Diethoxycarbonyl-1,4-dihydrocollidine (DDC) is a porphyrinogenic compound that induces hepatic formation of N-methyl protoporphyrin IX (NmePPIX), a potent endogenous inhibitor of ferrochelatase (FECH). Inhibition of FECH by NmePPIX blocks the conversion of protoporphyrin IX (PPIX) into heme, resulting in PPIX accumulation and PPIX-mediated cholestatic liver injury. Although cytochrome P450 (CYP)-mediated transfer of a methyl group from DDC has long been proposed as the mechanism underlying DDC-induced NmePPIX formation, the specific CYP enzymes responsible for DDC metabolism and NmePPIX formation remain poorly characterized. Here, a metabolomics-based approach identified six CYP-dependent DDC metabolites (M1–M6) in the incubation with mouse liver S9 fractions. Notably, no demethylated DDC metabolite was detected. We further demonstrated that CYP3A contributes to four metabolic pathways of DDC, including a previously unrecognized pathway involving deamination and intramolecular cyclization. Given the important role of CYP3A in DDC metabolism and its high hepatic expression, we investigated whether CYP3A contributes to NmePPIX formation. Our in vivo study found that Cyp3a deficiency had no effect on DDC-induced NmePPIX formation, PPIX accumulation, or PPIX-mediated liver injury. Collectively, these findings provide the first comprehensive characterization of CYP-dependent DDC metabolism and demonstrate that CYP3A is not essential for DDC-induced NmePPIX formation, indicating that the major CYP-dependent metabolic pathways of DDC are mechanistically distinct from the pathway leading to NmePPIX formation.

Nanoparticle (NP)-based drug delivery has been explored to improve the therapeutic index of anticancer agents by enhancing tumor accumulation and reducing systemic toxicity. Among active targeting approaches, cluster of differentiation 44 (CD44) has attracted attention because of its overexpression in tumor cells and tumor-associated endothelial cells and its involvement in tumor progression and therapeutic resistance. Hyaluronic acid (HA) and other glycosaminoglycan (GAG)-based nanocarriers have been developed to exploit CD44-mediated tumor targeting and cellular uptake. However, the in vivo performance of CD44-targeted NPs remains variable because of barriers such as systemic clearance, heterogeneous tumor vasculature and stroma, limited receptor accessibility, competition with endogenous ligands, and inefficient intracellular trafficking or payload release. This Letter summarizes advances in CD44-targeted NP delivery, focusing on barriers at systemic, tumor tissue, and cellular levels. We discuss barrier-informed strategies to optimize ligand presentation, improve penetration, promote intracellular payload release, and highlight translational challenges and opportunities for CD44-targeted nanomedicines.

Protein S -sulfinylation is a reversible oxidative cysteine modification, but its contribution to acute liver injury such as those induced by acetaminophen (APAP) overdose has not been reported. Sulfiredoxin-1 (SRXN1) is the only oxidoreductase known to reduce the sulfinylated proteins, yet the substrates and mechanisms through which it protects against acute liver injury are unclear. Here, we show that hepatic protein S -sulfinylation was markedly upregulated in APAP-overdose patients and mice. Hepatocyte-specific knockout or pharmacological inhibition of Srxn1 sensitized mice to APAP-induced acute liver injury. In contrast, overexpression of SRXN1, but not its oxidoreductase-dead C99S mutant, protected mice from APAP-induced liver injury. Mechanistically, we identified the deubiquitinase ubiquitin-specific protease 7 (USP7) as an SRXN1 substrate required for hepatoprotection. USP7 inhibition worsened APAP-induced liver injury, whereas its overexpression alleviated injury by stabilizing its deubiquitinase substrate heme oxygenase-1 (HO-1). Loss of SRXN1 enhanced S -sulfinylation of USP7 at Cys315, promoting its ubiquitination and degradation. SRXN1 expression correlated with USP7 levels in human liver samples. Delayed lipid nanoparticle (LNP) delivery of SRXN1 messenger RNA (mRNA) mitigated established APAP-induced liver injury beyond the therapeutic window of N -acetylcysteine. These findings define an SRXN1-USP7-HO-1 axis as a promising therapeutic target for oxidative liver injury and highlight LNP-mediated SRXN1 mRNA delivery as a potential treatment approach.

Advances with the 7 + 3 regimen and liposomal CPX-351 have significantly improved the treatment of acute myeloid leukemia (AML); however, challenges like drug resistance and immune evasion persist. Despite the demonstrated potential of immunotherapy in treating several types of solid tumors, its impact on the treatment of AML remains limited. To address these challenges, we engineered an ultrasmall (~ 15 nm) cytarabine (AraC)-based polymeric micelle nanocarrier (PAraC) for efficient AML cell uptake and bone marrow niche targeting. scRNA-seq and real-world dataset analysis identified upregulated TLR7/8 in malignant AML cells, particularly after 7 + 3 treatment, supporting the inclusion of the TLR7/8 agonist R848 in our combination therapy. Our strategy integrates smart co-delivery of AraC, daunorubicin (Daun), and R848 using the PAraC platform. This triple nano-combination (PAraC/Daun/R848) demonstrated potent antitumor efficacy, outperforming CPX-351 and PAraC/Daun in multiple leukemia models, including murine and patient-derived xenografts (PDX) AML models and AraC-resistant acute lymphoblastic leukemia (ALL) model. Notably, PAraC/Daun/R848 reversed immunosuppressive phenotypes seen with CPX-351 or PAraC/Daun and induced robust leukemia cell maturation. With its modular design, efficient delivery, and remarkable preclinical performance, the PAraC platform holds immense promise for clinical translation, offering a new frontier for immunotherapeutic interventions in AML.

Emerging evidence suggests that MYC binds RNAs, but its functional consequences remain unclear. Here, we integrate multiomics data and reveal that MYC broadly binds enhancer RNAs (eRNAs), which exhibit high cancer- and tissue-specific expression in cancer cell lines and patient tumors. Moreover, we developed a computational pipeline to identify potential cis-regulatory MYC-eRNA target genes, with most predicted eRNA-target pairs supported by RNA polymerase II–mediated chromatin interaction data. Among these, we functionally characterized MERG1 as an oncogenic eRNA that promotes breast cancer tumorigenesis. Mechanistically, MERG1 interacts with MYC to enhance its occupancy at the GREB1 promoter, driving chromatin remodeling and epigenetic activation. This process specifically amplifies GREB1 expression and promotes tumor progression. Last, nanoparticle-mediated delivery of antisense oligonucleotides targeting MERG1 suppresses MYC-mediated breast cancer growth. These results advance our understanding of the enhancer-driven regulation of gene expression and tumorigenesis and provide insights into the regulatory landscape of MYC in cancer.

Lipid nanoparticles (LNPs) have demonstrated their effectiveness as carriers for the delivery of RNA therapeutics. As the core components of the LNP system, ionizable cationic lipids (ICLs) are still the major focus of research in this field. In this study, we reported a class of novel β‐triketone‐based ICLs synthesized via click chemistry. We demonstrated that the reaction could be completed instantaneously, and a library of ICLs was generated in a short time. In vitro and in vivo screening identified a lipid that was comparable to FDA approved Dlin‐MC3‐DMA lipid in siRNA LNPs‐mediated gene silencing. In addition, we adopted a computational approach to characterizing the click chemistry in lipid synthesis, as well as the binding between siRNA and ICLs. Our work offers a novel approach to synthesizing ICLs of new structural features, which may not only improve our understanding of the structure‐activity relationship (SAR) of ICLs but also lead to the development of improved LNPs for more effective delivery of nucleic acid therapeutics.

Increases in retroelement-derived double-stranded RNAs (dsRNAs) in various types of cancer cells facilitate the activation of antitumor immune responses. The long noncoding RNA EPIC1 interacts with the histone methyltransferase EZH2 and contributes to tumor immune evasion. Here, we found that EPIC1 in tumor cells suppressed cytoplasmic dsRNA accumulation, type I interferon (IFN) responses, and antitumor immunity. In various cancer cell lines, knockdown of EPIC1 stimulated the production of dsRNA from retroelements and an antiviral-like type I IFN response that activated immune cells. EPIC1 inhibited the expression of LINE, SINE, and LTR retroelements that were also repressed by EZH2, suggesting a potential role for the EPIC1-EZH2 interaction in regulating dsRNA production. In a humanized mouse model, in vivo delivery of EPIC1-targeting oligonucleotides enhanced dsRNA accumulation in breast cancer xenografts, reduced tumor growth, and increased the infiltration of T cells and inflammatory macrophages into tumors. Furthermore, EPIC1 knockdown improved the therapeutic efficacy of the immunotherapy drug pembrolizumab, a PD-1 inhibitor, in the humanized mouse model. Together, our findings establish EPIC1 as a key regulator of dsRNA-mediated type I IFN responses and highlight its potential as a therapeutic target to improve the efficacy of immunotherapy.

STRAP (serine-threonine kinase receptor-associated protein), a WD domain-containing 38.5 kDa protein, was first identified in TGF-ß signaling and participates in scaffold formation in numerous cellular multiprotein complexes. It is involved in the regulation of several oncogenic biological processes, including cell proliferation, apoptosis, migration/invasion, tumor initiation and progression, and metastasis. STRAP upregulation in epithelial tumors regulates several signaling pathways, such as TGF-ß, MEK/ERK, Wnt/β-Catenin, Notch, PI3K, NF-κB, and ASK-1 in human cancers, including colon, breast, lung, osteosarcoma, and neuroblastoma. The upregulation of STRAP expression is correlated with worse survival in colorectal cancer following post-adjuvant therapy. Strap knockout sensitizes colon tumors to chemotherapy, delays APC-induced tumor progression, and reduces cancer cell stemness. The loss of Strap disrupts lineage differentiation, delays neural tube closure, and alters exon skipping, resulting in early embryonic lethality in mice. Collectively, the purpose of this review is to update and describe the diversity of targets functionally interacting with STRAP and to rationalize the involvement of STRAP in a variety of signaling pathways and biological processes. Therefore, these in vitro and in vivo studies provide a proof of concept that lowering STRAP expression in solid tumors decreases tumorigenicity and metastasis, and targeting STRAP provides strong translational potential to develop pre-therapeutic leads.