Sequence-selective binding of C8-conjugated pyrrolobenzodiazepines (PBDs) to DNA

Increased N-glycosylation of PSMA by GnT-V enhances tumor malignancy through interacting with JAK2 and the subsequent STAT3-mediated transcriptional activation in prostate cancer

Prostate-specific membrane antigen (PSMA), a membrane glycoprotein with high specificity, has emerged as an effective target for imaging and therapy in prostate cancer. Despite its potential, the role and molecular mechanism underlying PSMA glycosylation and overexpression remain to be fully clarified. In this study, we performed a comprehensive analysis of site-specific N-glycosylation patterns of PSMA, revealing that β1,6-GlcNAc branching at N121 and N336, catalyzed by GnT-V, is crucial for its expression. We found that the degradation of non-N-glycosylated PSMA predominantly occurs through the autophagy-lysosome pathway. Notably, androgen deprivation was shown to upregulate the expression of PSMA and GnT-V, simultaneously activating the transcription factor STAT3. Co-immunoprecipitation assay confirmed a direct interaction between PSMA and JAK2, which facilitates the activation of STAT3. This, in turn, drives the overexpression of PSMA and promotes its aberrant N-glycosylation, thereby advancing prostate cancer progression. Importantly, combined inhibition of STAT3 and N-glycosylation demonstrated a synergistic effect in reducing tumor viability. Our findings elucidate a novel positive feedback loop involving JAK2/STAT3/GnT-V/PSMA axis, contributing to the malignancy of prostate cancer and providing a foundation for innovative therapeutic strategies targeting this pathway.

A novel DNA sequence-selective, guanine mono-alkylating ADC payload suitable for solid tumour treatment

Pyridinobenzodiazepines (PDDs) are a new class of DNA mono-alkylating antibody-drug conjugate (ADC) payloads that can be linked through their C9 position to a sequence recognition component, guiding them to specific DNA sequences. Compound 18 is a PDD monomer with a unique sequence-selectivity profile and high cytotoxicity in vitro (e.g., IC50 = 0.30 nM in SW60; 1.6 nM in LIM1215 and 0.142 nM in SW48 cell line, after 96 hours incubation). To evaluate its potential as an ADC payload, an amine functionality was introduced into the terminal phenyl ring, and the modified compound was conjugated to trastuzumab (drug-antibody ratio [DAR] = 1.6). The resulting ADC exhibits significant in vivo efficacy in a pancreatic cancer xenograft model using BALB-c mice transplanted with the CAPAN-1 cell line. Complete tumour regression is observed out to 60 days after a single dose of 2 mg kg-1 comparing favourably to a 10 mg kg-1 dose of trastuzumab deruxtecan (Enhertu®). The novel ADC has a good tolerability profile, with a maximum tolerated dose (MTD) above 15 mg kg-1. The tolerability and efficacy profile of compound 18 in an ADC format suggests that PDDs represent a potentially valuable new class of payloads for the treatment of solid tumours.

Advances in PSMA-targeted therapy for prostate cancer

Prostate-specific membrane antigen (PSMA), a transmembrane glycoprotein located on the cell membrane, is specifically and highly expressed in prostate cancer (PCa). Besides, its expression level is related to tumor invasiveness. As a molecular target of PCa, PSMA has been extensively studied in the past two decades. Currently, a great deal of evidence suggests that significant progresses have been made in the PSMA-targeted therapy of PCa. Herein, different PSMA-targeted therapies for PCa are reviewed, including radioligand therapy (177Lu-PSMA-RLT, 225Ac-PSMA-RLT), antibody-drug conjugates (MLN2704, PSMA-MMAE, MEDI3726), cellular immunotherapy (CAR-T, CAR/NK-92, PSMA-targeted BiTE), photodynamic therapy, imaging-guided surgery (radionuclide-guided surgery, fluorescence-guided surgery, multimodal imaging-guided surgery), and ultrasound-mediated nanobubble destruction.

Noncytotoxic Pyrrolobenzodiazepine-Ciprofloxacin Conjugate with Activity against Mycobacterium tuberculosis

The development of new antitubercular agents for the treatment of infections caused by multidrug-resistant (MDR) Mycobacterium tuberculosis is an urgent priority. Pyrrolobenzodiazepines (PBDs) are a promising class of antibacterial agents that were initially discovered and isolated from a range of Streptomyces species. Recently, C8-linked PBD monomers have been shown to work by inhibiting DNA gyrase and have demonstrated activity against M. tuberculosis. However, both PBD monomers and dimers are toxic to eukaryotic cells, limiting their development as antibacterial agents. To eliminate the toxicity associated with PBDs and explore the effect of C8-modification with a known antibacterial agent with the same mechanism of action (i.e., ciprofloxacin, a gyrase inhibitor), we synthesized a C8-linked PBD-ciprofloxacin (PBD-CIP, 3) hybrid. The hybrid compound displayed minimum inhibitory concentration values of 0.4 or 2.1 μg/mL against drug-sensitive and drug-resistant M. tuberculosis strains, respectively. A molecular modeling study showed good interaction of compound 3 with wild-type M. tuberculosis DNA gyrase, suggesting gyrase inhibition as a possible mechanism of action. Compound 3 is a nontoxic combination hybrid that can be utilized as a new scaffold and further optimized to develop new antitubercular agents.

Effects of Systematic Shortening of Noncovalent C8 Side Chain on the Cytotoxicity and NF-κB Inhibitory Capacity of Pyrrolobenzodiazepines (PBDs)

The systematic shortening of the noncovalent element of a C8-linked pyrrolobenzodiazepine (PBD) conjugate (13) led to the synthesis of a 19-member library of C8-PBD monomers. The critical elements of 13, which were required to render the molecule cytotoxic, were elucidated by an annexin V assay. The effects of shortening the noncovalent element of the molecule on transcription factor inhibitory capacity were also explored through an enzyme-linked immunosorbent assay-based measurement of nuclear NF-κB upon exposure of JJN-3 cells to the synthesized molecules. Although shortening the noncovalent interactive element of 13 had a less than expected effect upon compound cytotoxicity due to reduced DNA interaction, the transcription factor inhibitory capacity of the molecule was notably altered. This study suggests that a relatively short noncovalent side chain at the C8 position of PBD is sufficient to confer cytotoxicity. The shortened PBD monomers provide a new ADC payload scaffold because of their potent cytotoxicity and drug-like properties.

Klebsiella oxytoca enterotoxins tilimycin and tilivalline have distinct host DNA-damaging and microtubule-stabilizing activities

Human gut microbes form a complex community with vast biosynthetic potential. Microbial products and metabolites released in the gut impact human health and disease. However, defining causative relationships between specific bacterial products and disease initiation and progression remains an immense challenge. This study advances understanding of the functional capacity of the gut microbiota by determining the presence, concentration, and spatial and temporal variability of two enterotoxic metabolites produced by the gut-resident Klebsiella oxytoca. We present a detailed mode of action for the cytotoxins and recapitulate their functionalities in disease models in vivo. The findings provide distinct molecular mechanisms for the enterotoxicity of the metabolites allowing them to act in tandem to damage the intestinal epithelium and cause colitis.

Establishing causal links between bacterial metabolites and human intestinal disease is a significant challenge. This study reveals the molecular basis of antibiotic-associated hemorrhagic colitis (AAHC) caused by intestinal resident Klebsiella oxytoca. Colitogenic strains produce the nonribosomal peptides tilivalline and tilimycin. Here, we verify that these enterotoxins are present in the human intestine during active colitis and determine their concentrations in a murine disease model. Although both toxins share a pyrrolobenzodiazepine structure, they have distinct molecular targets. Tilimycin acts as a genotoxin. Its interaction with DNA activates damage repair mechanisms in cultured cells and causes DNA strand breakage and an increased lesion burden in cecal enterocytes of colonized mice. In contrast, tilivalline binds tubulin and stabilizes microtubules leading to mitotic arrest. To our knowledge, this activity is unique for microbiota-derived metabolites of the human intestine. The capacity of both toxins to induce apoptosis in intestinal epithelial cells—a hallmark feature of AAHC—by independent modes of action, strengthens our proposal that these metabolites act collectively in the pathogenicity of colitis.