Biology subjects

Lunt, S.

Publications and source records attributed to Lunt, S..

5 recordsLinked to original sources

bioRxiv2023

Pyruvate Kinase Activity Regulates Cystine Starvation Induced Ferroptosis through Malic Enzyme 1 in Pancreatic Cancer Cells

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with high mortality and limited efficacious therapeutic options. PDAC cells undergo metabolic alterations to survive within a nutrient-depleted tumor microenvironment. One critical metabolic shift in PDAC cells occurs through altered isoform expression of the glycolytic enzyme, pyruvate kinase (PK). Pancreatic cancer cells preferentially upregulate pyruvate kinase muscle isoform 2 isoform (PKM2). PKM2 expression reprograms many metabolic pathways, but little is known about its impact on cystine metabolism. Cystine metabolism is critical for supporting survival through its role in defense against ferroptosis, a non-apoptotic iron-dependent form of cell death characterized by unchecked lipid peroxidation. To improve our understanding of the role of PKM2 in cystine metabolism and ferroptosis in PDAC, we generated PKM2 knockout (KO) human PDAC cells. Fascinatingly, PKM2KO cells demonstrate a remarkable resistance to cystine starvation mediated ferroptosis. This resistance to ferroptosis is caused by decreased PK activity, rather than an isoform-specific effect. We further utilized stable isotope tracing to evaluate the impact of glucose and glutamine reprogramming in PKM2KO cells. PKM2KO cells depend on glutamine metabolism to support antioxidant defenses against lipid peroxidation, primarily by increased glutamine flux through the malate aspartate shuttle and utilization of ME1 to produce NADPH. Ferroptosis can be synergistically induced by the combination of PKM2 activation and inhibition of the cystine/glutamate antiporter in vitro. Proof-of-concept in vivo experiments demonstrate the efficacy of this mechanism as a novel treatment strategy for PDAC. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=114 SRC="FIGDIR/small/557984v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@fa23c2org.highwire.dtl.DTLVardef@41c01dorg.highwire.dtl.DTLVardef@abc283org.highwire.dtl.DTLVardef@6f53ef_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIPKM2KO in pancreatic ductal adenocarcinoma (PDAC) cells produces enhanced defense against cystine starvation induced ferroptosis. C_LIO_LIPharmacologic activation of pyruvate kinase (PK) activity promotes ferroptosis under cystine starvation, while inhibition promotes ferroptosis survival in PDAC cells. C_LIO_LIDecrease in PK activity reprograms glutamine metabolism to increase use of malic enzyme 1 and promote survival under cystine starvation in PDAC cells. C_LIO_LICystine starvation and activation of pyruvate kinase synergistically decreases progression of pancreatic cancer in vivo. C_LI

cancer biology↗

bioRxiv2023

A CD24+CD271+ melanoma cancer stem cell generates a diffuse hierarchy of attributes that promote metastasis and therapeutic resistance

An important role for phenotype switching has been demonstrated in metastasis and therapeutic resistance of both melanoma and epithelial tumours. Phenotype switching in epithelial tumours is driven by a minority cancer stem cell sub-population with lineage plasticity, but such a sub-population has not been identified in melanoma. We investigated whether cell surface markers used to identify cancer stem cells in epithelial tumours could identify a cancer stem cell sub-population with lineage plasticity in melanoma. We identified a CD24+CD271+ minority sub-population in melanoma that possesses the stem cell characteristics of lineage plasticity and self-renewal. This population displayed hybrid characteristics, combining the attributes of discrete CD24+ and CD271+ cellular sub-populations but with heightened sphere formation, lineage plasticity, migratory ability and drug resistance over its single-marker counterparts. CD24+ and CD24+CD271+ stem cell sub-populations were observed in 10% of human melanomas, mainly at the invasive front. The lack of CD24+ and CD24+CD271+ stem cells in the majority of human melanoma specimens led us to conclude that they may be dispensable for melanoma progression. Nevertheless, the enhanced sphere formation, lineage plasticity, migratory ability and drug resistance of the CD24+CD271+ sub-population may signal a contextual requirement for these stem cells when melanomas face challenging environments both clinically and in experimental systems.

cancer biology↗

bioRxiv2020

UDP-Glucose 6-Dehydrogenase Knockout Impairs Migration and Decreases in vivo Metastatic Ability of Breast Cancer Cells

Dysregulated metabolism is a hallmark of cancer that supports tumor growth and metastasis. One understudied aspect of cancer metabolism is altered nucleotide sugar biosynthesis, which drives aberrant cell surface glycosylation known to support various aspects of cancer cell behavior including migration and signaling. We examined clinical association of nucleotide sugar pathway gene expression and found that UGDH, encoding UDP-glucose 6-dehydrogenase which catalyzes production of UDP-glucuronate, is associated with worse breast cancer patient survival. Knocking out the mouse homolog Ugdh in highly-metastatic 6DT1 breast cancer cells impaired migration ability without affecting in vitro proliferation. Further, Ugdh-KO resulted in significantly decreased metastatic capacity in vivo when the cells were orthotopically injected in syngeneic mice. Our experiments show that UDP-glucuronate biosynthesis is critical for metastasis in a mouse model of breast cancer.

cancer biology↗

bioRxiv2020

Targeting subtype-specific metabolic preferences in nucleotide biosynthesis inhibits mouse mammary tumor growth

Investigating metabolic rewiring in cancer can lead to the discovery of new treatment strategies for breast cancer subtypes that currently lack targeted therapies. Using MMTV-Myc driven tumors to model breast cancer heterogeneity, we investigated metabolic differences between two histological subtypes, the epithelial-mesenchymal transition (EMT) and the papillary subtypes, using a combination of genomic and metabolomic techniques. We identified differences in nucleotide metabolism between EMT and papillary subtypes: EMT tumors preferentially use the nucleotide salvage pathway, while papillary tumors prefer de novo nucleotide biosynthesis. Using CRISPR/Cas9 gene editing and mass spectrometry-based methods, we determined that targeting the preferred pathway in each subtype resulted in greater metabolic impact than targeting the non-preferred pathway. We further show that knocking out the preferred nucleotide pathway in each subtype has a deleterious effect on in vivo tumor growth. In contrast, knocking out the non-preferred pathway has a lesser effect or results in increased tumor growth.

cancer biology↗

bioRxiv2019

Drug target discovery via network modeling: a mathematical model of the E. coli folate network response to trimethoprim

The antibiotic trimethoprim targets the bacterial dihydrofolate reductase enzyme and subsequently affects the entire folate network. We present an expanded mathematical model of trimethoprims action on the Escherichia coli folate network that greatly improves upon Kwon et al. (2008). The improvement upon the Kwon Model lends greater insight into the effects of trimethoprim at higher resolution and accuracy. More importantly, the presented mathematical model enables drug target discovery in a way the earlier model could not. Using the improved mathematical model as a scaffold, we use parameter optimization to search for new drug targets that replicate the effect of trimethoprim. We present the model and model-scaffold strategy as an efficient route for drug target discovery.

systems biology↗