Biology subjects

Duncan, K. D.

Publications and source records attributed to Duncan, K. D..

3 recordsLinked to original sources

bioRxiv2025

Ambient mass spectrometry imaging enables spatial metabolomics of optimal cutting temperature compound (OCT)-embedded tumors

Mass spectrometry imaging (MSI) is emerging as a powerful tool for uncovering the distribution of metabolites in the tumor microenvironment and studying tumor metabolism in vivo. However, to date, MSI of primary patient biobanked tissues contextualized by patient data has been limited to peptides, proteins, and glycans - with few examples for metabolites. This is because most biobanked fresh-frozen tissue required for spatial metabolomics is embedded in optimal cutting temperature compound (OCT), which introduces high-abundance polymeric interferents. Herein, we use nanospray desorption electrospray ionization (nano-DESI) to demonstrate the MSI of metabolites in OCT-embedded tissue. Metabolite coverage and sensitivity for prepared tissue mimetic homogenates embedded in OCT and an MSI-compatible material, carboxymethylcellulose (CMC), showed excellent agreement. We apply our ambient MSI workflow to detect changes in intratumoral methionine using a preclinical cancer mouse model undergoing adoptive T-cell therapy. Eight days after tumor incubation, lymphoma-bearing mice were maintained on a complete or methionine-restricted diet for 2 days. Nano-DESI MSI revealed a heterogeneous tumor microenvironment, with multiple methionine-cycle intermediates (S-adenosylmethionine, S-adenosylhomocysteine) and related metabolites, including known T-cell modulators (1-methylnicotinamide, polyamines) localizing to tumor subregions. Methionine-restricted tumors exhibited reduced methionine levels and elevated S-adenosylmethionine, relative to the control group. Overall, this work demonstrates spatial metabolomics on fresh-frozen OCT-embedded tissue, unlocking the wealth of information stored in primary tissue biobanks and consequently accelerating our understanding of cancer metabolism and treatment.

cancer biology↗

bioRxiv2025

Methionine regulates antitumor function of CD8⁺ T cells through polyamine synthesis

Methionine is an essential amino acid critical for T cell activation. While methionine restriction (MR) combined with immune checkpoint blockade has been shown to enhance T cell function, the impact of methionine on adoptive T cell therapies is largely unexplored. Here, we examined the functionality of T cells under MR and pharmaceutical inhibition of the methionine cycle (MAT2Ai), using primary T cells and a murine adoptive T cell therapy model. In vitro, transient MR or MAT2Ai treatment increased interferon gamma (IFN{gamma}) expression in CD8+ T cells, whereas sustained MR led to the upregulation of T cell exhaustion-associated markers. Mechanistically, transient MR suppressed the polyamine synthesis pathway, and supplementation with polyamines reversed MR-induced IFN{gamma} expression. Genetic ablation of s-adenosylmethionine decarboxylase, an enzyme in the polyamine synthesis pathway, recapitulated the effect of MR, indicating that transient MR enhances T cell function by inhibiting polyamine synthesis. Despite this, transient MR treatment of ovalbumin (OVA)-specific (OT-I) CD8+ T cells prior to adoptive transfer did not improve antitumor efficacy against EG7-OVA tumors in vivo. In contrast, sustained dietary MR accelerated EG7-OVA tumor growth in mice treated with OT-I T cells, demonstrating that methionine availability is essential for the activity of adoptively transferred T cells. These findings suggest that enhancing methionine availability in the tumor microenvironment may improve the efficacy of adoptive T cell therapies.

immunology↗

bioRxiv2025

On a roll: Recent familiarity primes the brain to retrieve other memories via dopaminergic nuclei mechanisms

Memory retrieval is notoriously variable. Various neurocognitive states have been theorized to affect retrieval success from moment to moment, but the presence and catalysts of these states in the human brain remain largely understudied. Building on previous work, we studied how recent memory judgments during an ongoing retrieval task (i.e. retrieval judgments vs. novelty detection) and their corresponding neural activity prepare the brain to reinstate unrelated memories during upcoming trials. High-level ventral stream regions, including the hippocampus, reinstated memories with significantly greater fidelity following recent retrieval judgments compared to novelty detection. Activity in dopaminergic nuclei rose during retrieval judgments, which predicted and partially mediated the effect of retrieval judgments on upcoming reinstatement. While dopaminergic nuclei activity predicted upcoming reinstatement, it did not predict upcoming retrieval accuracy. Exploratory analyses revealed the opposite effect in the dorsal and lateral prefrontal cortex, whose activity predicted upcoming retrieval accuracy, but not reinstatement. These results point to distinct neural contributions to what is reinstated and how it may guide memory decisions, and by identifying dopaminergic nuclei as partial mediators of reinstatement, our results open new avenues for investigating how neuromodulatory states may dynamically shape memory accessibility. Significance StatementWhy can we effortlessly recall memories in some moments but struggle at others? Here, we draw on computational models to uncover why human brains are sometimes better prepared to remember and how to nudge them into that state. We discover that recent retrieval judgments, compared to recent novelty detection, increase upcoming accuracy and neural reinstatement of unrelated memories. This effect is so powerful that key memory regions only show reinstatement following preceding retrieval judgments. We found that dopaminergic nuclei are more active during retrieval judgments and predict upcoming memory reinstatement. This pattern partially explains why engaging in remembering prepares your brain to reinstate other memories and reveals new insights for the role dopaminergic nuclei may play in retrieval.

neuroscience↗