Biology subjects

Kerr, E. M.

Publications and source records attributed to Kerr, E. M..

8 recordsLinked to original sources

bioRxiv2026

FLIP is essential for oncogenic KRAS-driven lung cancer

Mutations in KRAS represent the most common oncogenic event in human cancer and occur in approximately 30% of lung adenocarcinomas. The mechanisms by which lung tumours evade apoptosis induced by oncogenic KRAS-driven stress remain incompletely understood. Here, we identify the anti-apoptotic regulator FLIP (CFLAR) as a critical dependency in KRAS-mutant lung cancers. We demonstrate that KRAS-mutant human lung cancer cell lines exhibit elevated FLIP expression and enhanced dependence on FLIP for survival compared to KRAS wild-type counterparts. Subsequently, using genetically engineered mouse models (GEMMs), we show that FLIP is essential for Kras-driven lung tumour development in vivo. In vitro, FLIP-deficient lung cancer cells display spontaneous, caspase-8- dependent apoptosis and hyper-sensitivity to the immune/inflammatory cytokines TNF and TRAIL. Strikingly, FLIP-null lung cancer cells fail to engraft even in highly immunodeficient orthotopic models that lack TRAIL-expressing immune cells but retain TNF-expressing monocytes. Moreover, silencing of TNFR1 or TNF but not TRAIL-R2 rescued constitutive caspase-8-dependent apoptosis in FLIP null lung cancer cells, implicating TNF/TNFR1 in mediating this apoptotic response. Mechanistically, we find that mutant KRAS sustains FLIP expression via ERK1/2 signalling, thereby protecting cells from caspase-8 activation. Notably, KRAS inhibition downregulates FLIP, sensitising cells to TNF- and TRAIL-induced apoptosis. These findings uncover a novel KRAS-ERK-FLIP axis that protects tumour cells from caspase-8-mediated apoptosis and reveal FLIP as a key survival factor co-opted by KRAS-mutant lung cancers. Beyond identifying FLIP as a promising therapeutic target in KRAS mutant lung cancer, our work also provides mechanistic insight into the pro-apoptotic effects of KRAS inhibitors and suggests that FLIP expression may serve as a predictive biomarker to enhance patient stratification and the therapeutic efficacy of these agents in lung cancer.

cancer biology↗

bioRxiv2026

Mutant KRAS dosage contributes to heterogeneity in lung cancer therapeutic response

Oncogenic KRAS mutations promote tumorigenesis by constitutive activation of multiple, well-characterised signalling pathways. However, there is significant heterogeneity across mutant KRAS tumours in terms of mutation present, mutant allele abundance and downstream signalling strength. It is unclear whether these variations can impact responses to specific therapies. Here, we demonstrate that [~]20% of lung adenocarcinomas (LUAD) show an increase in mutant KRAS dosage (KRASmutant allele fraction > KRASwild-type). Furthermore, we show that KRAS mutant dosage can directly influence clinical outcome and therapeutic susceptibilities in lung cancer. Our findings show that mutant KRAS copy gains specifically affect platinum lung cancer response, promoting resistance to this standard-of-care therapy. Importantly, increases in KRAS mutant dosage are also associated with an increased vulnerability to pS6K inhibition, due to the unique metabolic rewiring of these cells. Together, we show that mutant KRAS dosage contributes to the phenotypic heterogeneity of mutant KRAS NSCLC and that assessment of mutant KRAS content or signalling strength can help optimise treatments strategies for these patients.

cancer biology↗

bioRxiv2025

Identification of a novel GREMLIN1 uptake pathway in epithelial cells that requires BMP binding

Gremlin1 is a member of a cysteine-knot containing family of secreted antagonists of bone morphogenetic protein signaling. GREM1 binding to BMP targets prevents their engagement with cognate BMP receptors, attenuating BMP-dependent gene expression. Some evidence suggests that GREM1 can directly bind to receptor tyrosine kinases on the plasma membrane, further complicating our understanding of GREM1 biology. To attempt to clarify the modalities of GREM1 signaling, we show that GREM1 protein is produced and secreted by intestinal fibroblasts and endocytosed by neighbouring epithelial cells. GREM1 uptake is a slow process and occurs by both clathrin- and caveolin-mediated endocytosis. Cell membrane heparin sulfate proteoglycans are required for GREM1 binding and uptake, and once internalised, GREM1 appears to localise to the early endosomes. Addition of BMP2 enhanced GREM1 uptake into cells. Remarkably, generation of a BMP-resistant GREM1 mutant abolished GREM1 uptake both in the presence and absence of BMP2. These data suggest that GREM1 binding and uptake into cells requires BMP binding, a process that may contribute to the antagonism of BMP signaling by GREM1. SummaryIn this article, we demonstrate differential GREM1 mRNA versus protein expression in mouse intestine. We also identify a novel GREM1 endocytosis pathway whereby mammalian cells take up GREM1 protein in what appears to be a BMP-dependent mechanism.

cell biology↗

bioRxiv2024

Mitochondrial metabolism is a key determinant of chemotherapy sensitivity in Colorectal Cancer

Therapy resistance is attributed to over 80% of cancer deaths per year emphasizing the urgent need to overcome this challenge for improved patient outcomes. Despite its widespread use in colorectal cancer (CRC) treatment, resistance to 5-fluorouracil (5FU) remains poorly understood. Here, we investigate the transcriptional responses of CRC cells to 5FU treatment, revealing significant metabolic reprogramming towards heightened mitochondrial activity. Utilizing CRC models, we demonstrate sustained enhancement of mitochondrial biogenesis and function following 5FU treatment, leading to resistance in both in vitro and in vivo settings. Furthermore, we show that targeting mitochondrial metabolism, specifically by inhibiting Complex I (CI), sensitizes CRC cells to 5FU, resulting in delayed tumour growth and prolonged survival in preclinical models. Additionally, our analysis of patient data suggests that oxidative metabolism signatures may predict responses to 5FU-based chemotherapy. These findings shed light on mechanisms underlying 5FU resistance and propose a rational strategy for combination therapy in CRC, emphasizing the potential clinical benefit of targeting mitochondrial metabolism to overcome resistance and enhance patient outcomes.

cancer biology↗

bioRxiv2022

Spt6 directly interacts with Cdc73 and is required for Paf1C recruitment to active genes

Paf1C is a conserved transcription elongation factor that regulates transcription elongation efficiency, facilitates co-transcriptional histone modifications, and impacts molecular processes linked to RNA synthesis, such as polyA site selection. Coupling of the activities of Paf1C to transcription elongation requires its association with RNA polymerase II (Pol II). Mutational studies in yeast identified Paf1C subunits Cdc73 and Rtf1 as important mediators of Paf1C recruitment to Pol II on active genes. While the interaction between Rtf1 and the general elongation factor Spt5 is relatively well-understood, the interactions involving Cdc73 remain to be elucidated. Using an in vivo site-specific protein cross-linking strategy, we identified direct interactions between Cdc73 and two components of the elongation complex, the elongation factor Spt6 and the largest subunit of Pol II. Through in vitro protein binding assays and crosslinking/mass spectrometry, we show that Cdc73 and Spt6 can interact in the absence of additional factors and propose a binding interface. Rapid depletion of Spt6 dissociated Paf1 from chromatin and altered patterns of Paf1C-dependent histone modifications genome-wide. These results reveal previously unrecognized interactions between Cdc73 and the Pol II elongation complex and identify Spt6 as a key factor contributing to Paf1C recruitment to active genes in Saccharomyces cerevisiae.

molecular biology↗

bioRxiv2021

Stromal cell sialylation suppresses T cells in inflammatory tumour microenvironments: A new tumour stromal cell immune checkpoint?

Immunosuppressive tumour microenvironments (TME) reduce the effectiveness of immune responses in cancer. Non-haematopoietic mesenchymal stromal cells (MSC), the precursor to cancer associated fibroblasts (CAFs), dictate tumour progression by enhancing immune cell suppression. Hyper-sialylation of glycans promotes immune evasion in cancer, but the role of sialyation in stromal cell-mediated immunosuppression is unknown. Here we study changes in sialyltransferase (ST) enzymes and associated surface expressed sialic acid in stromal cells following inflammatory and tumour secretome conditioning. We show that tumour conditioned stromal cells have increased levels of sialyltransferases, 2,3/6 linked sialic acid and siglec ligands. In tumour models of solid (colorectal cancer) and haematological (multiple myeloma) stromal rich tumours, stromal cell sialylation is associated with enhanced immunosuppression. Using datasets and patient samples, we confirm that targeting sialylation in tumour stromal cells reverses immune cell exhaustion. Targeting stromal cell sialylation may represent a novel immune checkpoint to reactivate anti-tumour immunity.

immunology↗

bioRxiv2020

Clinical positioning of the IAP antagonist tolinapant (ASTX660) in colorectal cancer

Cancer cells frequently express elevated levels of Inhibitor of Apoptosis Proteins (IAPs): cIAPI, cIAP2 and XIAP. Elevated expression of cIAP1 and cIAP2 (but not XIAP) significantly correlated with poor prognosis in microsatellite stable (MSS) stage-III colorectal cancer (CRC) patients treated with adjuvant chemotherapy, suggesting their involvement in promoting resistance. Preclinical analysis of the IAP inhibitor tolinapant in CRC cell lines demonstrated robust on-target effects and caspase-8-dependent apoptosis that was inhibited by the caspase-8 paralogs FLIP and, unexpectedly, caspase-10. Importantly, tolinipant-induced apoptosis was augmented by standard-of-care chemotherapy (FOLFOX) in CRC disease models, due (at least in part) to FOLFOX-induced downregulation of Class-I histone deacetylases, leading to acetylation of the FLIP-binding partner Ku70 and downregulation of FLIP. Moreover, this effect could be phenocopied using a Class-I HDAC inhibitor. Further analyses revealed that caspase-8-knockout RIPK3-positive CRC models were sensitive to tolinostat-induced necroptosis, an effect that could be exploited with the FDA-approved caspase inhibitor emricasan. Our study provides evidence for immediate clinical exploration of tolinapant in combination with FOLFOX chemotherapy in poor prognosis MSS CRC with elevated cIAP1/2 expression.

cancer biology↗

bioRxiv2019

FLIP(L) determines p53 induced life or death

How p53 differentially activates cell cycle arrest versus cell death remains poorly understood. Here, we demonstrate that upregulation of canonical pro-apoptotic p53 target genes in colon cancer cells imposes a critical dependence on the long splice form of the caspase-8 regulator FLIP (FLIP(L)), which we identify as a direct p53 transcriptional target. Inhibiting FLIP(L) expression with siRNA or Class-I HDAC inhibitors promotes apoptosis in response to p53 activation by the MDM2 inhibitor Nutlin-3A, which otherwise predominantly induces cell-cycle arrest. When FLIP(L) upregulation is inhibited, apoptosis is induced in response to p53 activation via a novel ligand-independent TRAIL-R2/caspase-8 complex, which, by activating BID, induces mitochondrial-mediated apoptosis. Notably, FLIP(L) depletion inhibits p53-induced expression of the cell cycle regulator p21 and enhances p53-mediated upregulation of PUMA, with the latter activating mitochondrial-mediated apoptosis in FLIP(L)-depleted, Nutlin-3A-treated cells lacking TRAIL-R2/caspase-8. Thus, we report two previously undescribed, novel FLIP(L)-dependent mechanisms that determine cell fate following p53 activation.

cancer biology↗