Biology subjects

Chee, J.

Publications and source records attributed to Chee, J..

4 recordsLinked to original sources

bioRxiv2026

Copper chelation reprograms the tumour microenvironment to enhance immune checkpoint blockade therapy in preclinical mesothelioma

Immune checkpoint blockade provides durable benefit to only a minority of patients with pleural mesothelioma. Here we investigated whether targeting copper homeostasis could enhance anti-tumour immunity and improve responses to immune checkpoint blockade. Copper homeostasis genes were upregulated in human mesothelioma, localised to malignant and stromal cells but downregulated in lymphocytes. In murine mesothelioma, these genes were dynamically regulated during anti-CTLA-4 and anti-PD-1 therapy. Treatment with copper chelator triethylenetetramine reduced intratumoural copper, increased cytotoxic lymphocytes, and enriched inflammatory genes in tumour-infiltrating myeloid and lymphoid compartments. Furthermore, copper chelation enhanced anti-CTLA-4 and anti-PD-1 therapy in immunocompetent mesothelioma mouse models, leading to durable tumour control. Our findings identify copper homeostasis as a therapeutic vulnerability in mesothelioma and support clinical evaluation of copper depletion with first-line immune checkpoint blockade.

immunology↗

bioRxiv2025

Age-dependent tumor-immune interactions underlie immunotherapy response in pediatric cancer

Pediatric cancers originate in rapidly growing tissues within the context of a developing host. However, the interactions between cancer cells and the developing immune system are incompletely understood. Here, we established a suite of pediatric syngeneic mouse cancer models across diverse anatomical sites and compared their tumor immune microenvironment with that in adult mice. Tumors in pediatric mice exhibited significantly accelerated growth and diminished leukocyte infiltration, dominated by naive-like PD-1low/CD8+ T cells, and proliferative MHCIIlow/PD-L1hi/CD86low macrophages. Tumor-infiltrating leukocytes in pediatric mice were enriched for MYC targets, which was also observed in pediatric patient samples. Furthermore, pediatric mice displayed poor responses to anti-PD-1/PD-L1 or bispecific T cell engager antibodies, which could be reversed by inducing a proinflammatory microenvironment via MYC inhibition or inducing macrophage polarization to an MHCIIhi phenotype. These findings underscore the significant influence of young age on cancer immune responses and reveal potential new therapeutic opportunities for pediatric cancers. HIGHLIGHTSO_LIAllograft tumors exhibit markedly accelerated growth in pediatric hosts compared to adults. C_LIO_LITumors growing in pediatric mice have reduced leukocyte infiltration, dominated by naive-like PD-1low/CD8+ T cells, and MHCIIlow/M2-like macrophages. C_LIO_LIEnrichment of MYC target genes is observed in pediatric mouse tumors and confirmed in primary patient tumor samples. C_LIO_LIPediatric mice display reduced response to anti-PD-1/PD-L1 and BiTE immunotherapy, which can be reversed by remodeling the TIME, using either MYC inhibition or macrophage polarization. C_LI

cancer biology↗

bioRxiv2023

A genetic screen identifies a role for oprF in Pseudomonas aeruginosa biofilm stimulation by subinhibitory antibiotics

Biofilms are surface-associated communities of bacteria that grow in a self-produced matrix of polysaccharides, proteins, and extracellular DNA (eDNA). Sub-minimal inhibitory concentrations (sub-MIC) of antibiotics induce biofilm formation, indicating a potential defensive response to antibiotic stress. However, the mechanisms behind sub-MIC antibiotic-induced biofilm formation are unclear. We show that treatment of Pseudomonas aeruginosa with multiple classes of sub-MIC antibiotics with distinct targets induces biofilm formation. Further, addition of exogenous eDNA or cell lysate failed to increase biofilm formation to the same extent as antibiotics, suggesting that the release of cellular contents by antibiotic-driven bacteriolysis is insufficient. Using a genetic screen to find stimulation-deficient mutants, we identified the outer membrane porin OprF and the extracytoplasmic function sigma factor SigX as important for the phenotype. Similarly, loss of OmpA - the Escherichia coli OprF homologue - prevented sub-MIC antibiotic stimulation of E. coli biofilms. The C-terminal PG-binding domain of OprF was dispensable for biofilm stimulation. Our screen also identified the periplasmic disulfide bond-forming enzyme DsbA and a predicted cyclic-di-GMP phosphodiesterase encoded by PA2200 as essential for biofilm stimulation. The phosphodiesterase activity of PA2200 is likely controlled by a disulfide bond in its regulatory domain, and folding of OprF is influenced by disulfide bond formation, connecting the mutant phenotypes. Addition of the reducing agent dithiothreitol prevented sub-MIC antibiotic biofilm stimulation. Finally, we show that activation of a c-di-GMP-responsive promoter follows treatment with sub-MIC antibiotics in the wild-type but not an oprF mutant. Together, these results show that antibiotic-induced biofilm formation is likely driven by a signalling pathway that translates changes in periplasmic redox state into elevated biofilm formation through increases in c-di-GMP. SignificanceBacterial biofilms cause significant treatment challenges in clinical settings due to their ability to resist antibiotic killing. Paradoxically, sub-inhibitory levels of a number of chemically distinct antibiotics, with different modes of action, can stimulate biofilm formation of multiple bacterial species. In this work we used the biofilm forming opportunistic pathogen Pseudomonas aeruginosa to look for mutants blind to sub-inhibitory antibiotic exposure, failing to demonstrate biofilm stimulation in response to 3 different antibiotics. We identified key players in this response, including the outer membrane porin OprF and the sigma factor SigX. Notably, the hits from our mutant screen connect changes in periplasmic redox state to elevated biofilm formation via c-di-GMP signaling. By understanding these underlying mechanisms, we can better strategize interventions against biofilm-mediated antibiotic resistance in P. aeruginosa and other bacterial species.

microbiology↗

bioRxiv2019

Thiostrepton hijacks pyoverdine receptors to inhibit growth of Pseudomonas aeruginosa

Pseudomonas aeruginosa is a biofilm-forming opportunistic pathogen and intrinsically resistant to many antibiotics. In a high-throughput screen for molecules that modulate biofilm formation, we discovered that the thiopeptide antibiotic, thiostrepton (TS) - considered inactive against Gram-negative bacteria - stimulated P. aeruginosa biofilm formation in a dose-dependent manner. This phenotype is characteristic of exposure to antimicrobial compounds at sub-inhibitory concentrations, suggesting that TS was active against P. aeruginosa. Supporting this observation, TS inhibited growth of a panel of 96 multidrug-resistant (MDR) P. aeruginosa clinical isolates at low micromolar concentrations. TS also had activity against Acinetobacter baumannii clinical isolates. Expression of Tsr - a 23S rRNA-modifying methyltransferase - in trans conferred TS resistance, confirming that the drug acted via its canonical mode of action, inhibition of ribosome function. Deletion of oligopeptide permease systems used by other peptide antibiotics for uptake failed confer TS resistance. TS susceptibility was inversely proportional to iron availability, suggesting that TS exploits uptake pathways whose expression is increased under iron starvation. Consistent with this finding, TS activity against P. aeruginosa and A. baumannii was potentiated by FDA-approved iron chelators deferiprone and deferasirox. Screening of P. aeruginosa mutants for TS resistance revealed that it exploits pyoverdine receptors FpvA and FpvB to cross the outer membrane. Our data show that the biofilm stimulation phenotype can reveal cryptic sub-inhibitory antibiotic activity, and that TS has activity against select multidrug resistant Gram-negative pathogens under iron-limited growth conditions, similar to those encountered at sites of infection.

microbiology↗