Biology subjects

Shackleton, M.

Publications and source records attributed to Shackleton, M..

6 recordsLinked to original sources

bioRxiv2023

Computational repurposing of oncology drugs through off-target drug binding interactions from pharmacological databases

PURPOSESystematic repurposing of approved medicine for another indication represents an attractive strategy to accelerating drug development in oncology. Herein we present a strategy of combining biomarker testing with drug repurposing to identify new treatments for patients with advanced cancer. METHODSTumours were sequenced with Illumina TruSight Oncology 500 (TSO-500) platform or the FoundationOne(R) CDx panel. Mutations were manually screened by two medical oncology clinicians and pathogenic mutations were categorised with reference to the literature. Variants of unknown significance were classified as potentially pathogenic if a plausible mechanism and computational prediction of pathogenicity existed. Gain of function mutations were evaluated through the repurposing databases Probe Miner, the Broad Institute Drug Repurposing Hub (Broad Institute DRH) and TOPOGRAPH. Gain of function mutations were classified as repurposing events if they were identified in Probe Miner, were not indexed in TOPOGRAPH which captures active clinical trial biomarkers and excluding mutations for which a known FDA-approved biomarker label exists. The performance of the computational repurposing approach was validated by evaluating its ability to identify known FDA-approved biomarkers. Exploratory functional analyses were performed with gene expression data and CRISPR-dependency data sourced from the DepMap portal. The total repurposable genome was identified by evaluating all possible gene-FDA drug approved combinations in the Probe Miner dataset. RESULTSThe computational repurposing approach was highly accurate at identifying FDA therapies with known biomarkers (94%). Using a real-world dataset of next-generation sequencing molecular reports (n = 94) and excluding the identification of mutations that would render patients eligible for FDA-licensed therapies or local clinical trials, it was found that a meaningful percentage of patients (14%) would have an off-label therapeutic identified through this approach. Exploratory analyses were performed, including the identification of drug-target interactions that have been previously described in the medicinal chemistry literature but are not well known, and the evaluation of the frequency of theoretical drug repurposing events in the TCGA pan-cancer dataset (73% of samples in the cohort). CONCLUSIONOverall, a computational drug repurposing approach may assist in identifying novel repurposing events in cancer patients with advanced tumours and no access to standard therapies. Further validation is needed to confirm the utility of a precision oncology approach using drug repurposing.

biochemistry↗

bioRxiv2022

Prospective isolation according to melanin pigment content of melanoma cells with heterogeneous potentials for disease propagation

Functional variation between cancer cells (intra-tumoral heterogeneity) poses a major challenge to treating and managing cancer patients. Melanomas are typically composed of cancer cells with heterogeneous content of melanin pigment. Pigment production is a hallmark of normal melanocytic differentiation, however the functional consequences of melanin production in melanoma cells remains poorly understood owing to a lack of experimental approaches for detection of pigment in unfixed cells. Here, we describe a novel flow cytometric method for high purity separation of viable melanoma cells based on their content of melanin pigment, exploiting the infrared light scattering properties of melanin. By fluorescence-activated cell sorting, we show that melanoma cells with low-pigment content (LPCs) in culture and in patient tumors are far more abundant than high-pigment cells (HPCs), and have substantially increased potentials for colony formation in vitro and for tumor formation in vivo. RNAseq analysis revealed activation of P53 in HPCs associated with perturbed cell cycling, whereas LPCs displayed upregulation of MYC-associated transcription and activated ribosome biogenesis. The latter was reduced by topoisomerase 2 beta targeting with CX-5461, which also induced senescent HPC phenotypes and irreversible loss of clonogenic activity. These data illuminate an inverted pyramid hierarchical model of melanoma cell propagation wherein abundant LPCs frequently renew their own malignant potential to propagate disease, but also rarely generate HPCs that lose this ability in a manner that may be promoted as an anti-melanoma strategy.

cancer biology↗

bioRxiv2021

The cytosolic role of EZH2-IMPDH2 complex in melanoma progression and metastasis via GTP regulation

The enhancer of zeste homolog 2 (EZH2) oncoprotein is a histone methyltransferase that functions canonically as a catalytic subunit of the polycomb repressive complex 2 (PRC2) to tri-methylate histone H3 at Lys 27 (H3K27me3). Although targeting EZH2 methyltransferase is a promising therapeutic strategy against cancer, methyltransferase-independent oncogenic functions of EZH2 are described. Moreover, pharmacological EZH2 methyltransferase inhibition was only variably effective in pre-clinical and clinical studies, suggesting that targeting EZH2 methyltransferase alone may be insufficient. Here, we demonstrate a non-canonical mechanism of EZH2s oncogenic activity characterized by interactions with inosine monophosphate dehydrogenase 2 (IMPDH2) and downstream promotion of guanosine-5-triphosphate (GTP) production. EZH2-IMPDH2 interactions identified by Liquid Chromatography-Mass Spectrometry (LC-MS) of EZH2 immunoprecipitates from melanoma cells were verified to occur between the N-terminal EED-binding domain of cytosolic EZH2 and the CBS domain of IMPDH2 in a methyltransfersase-independent manner. EZH2 silencing reduced cellular GTP, ribosome biogenesis, RhoA-mediated actomyosin contractility and melanoma cell proliferation and invasion by impeding the activity of IMPDH2. Guanosine, which replenishes GTP, reversed these effects and thereby promoted invasive and clonogenic cell states even in EZH2 silenced cells. IMPDH2 silencing antagonized the proliferative and invasive effects of EZH2, also in a guanosine-reversible manner. In human melanomas, high cytosolic EZH2 and IMPDH2 expression were associated with nucleolar enlargement, a marker of ribosome biogenesis. EZH2-IMPDH2 complexes were also observed in a range of cancers in which Sappanone A (SA), which inhibits EZH2-IMPDH2 interactions, was anti-tumorigenic, although notably non-toxic in normal cells. These findings illuminate a previously unrecognized, non-canonical, methyltransferase-independent, and GTP-dependent mechanism by which EZH2 regulates tumorigenicity in melanoma and other cancers, opening new avenues for development of anti-EZH2 therapeutics. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=157 SRC="FIGDIR/small/467024v2_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@153dd35org.highwire.dtl.DTLVardef@dfeb43org.highwire.dtl.DTLVardef@ce8148org.highwire.dtl.DTLVardef@189d8da_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract C_FIG HighlightsO_LIEZH2 has non-canonical methyltransferase-independent and GTP-dependent tumorigenic and metastatic functions in melanoma. C_LIO_LIThe N-terminal EED-binding domain of EZH2 interacts with the CBS domain of IMPDH2 in a polycomb repressive complex 2- (PRC2-) and methylation-independent manner. C_LIO_LIEZH2 accumulates with IMPDH2 in the cytoplasm and increases IMPDH2s tetramerization-mediated activity independently of EZH2 methyltransferase. C_LIO_LIEZH2 upregulates GTP synthesis by IMPDH2 activation and thereby activates ribosome biogenesis via rRNA synthesis and actomyosin contractility via RhoA GTPase. C_LIO_LISappanone A (SA) inhibits IMPDH2-EZH2 interactions and is anti-proliferative across a range of cancers including melanoma, but not in normal cells. C_LI

cancer biology↗

bioRxiv2021

EZH2 Abundance Regulated by UHRF1/UBE2L6/UBR4 Ubiquitin System is the Potential Therapeutic Target to Trigger Pigmented Phenotype in Melanoma

Cellular heterogeneity in cancer is linked to disease progression and therapy response, although the mechanisms regulating distinct cellular states within tumours are not well understood. To address this, we identified melanin pigment content as a major source of phenotypic and functional heterogeneity in melanoma and compared RNAseq data from high (HPC) and low pigmented melanoma cells (LPC), revealing the polycomb repressor complex protein, EZH2, as a master regulator of these states. EZH2 protein, but not RNA expression, was found to be upregulated in LPCs and inversely correlated with melanin in pigmented patient melanomas. Surprisingly, conventional EZH2 methyltransferase inhibitors, GSK126 and EPZ6438, had no effect on LPC survival, clonogenicity and pigmentation, despite fully inhibiting methyltransferase activity. In contrast, EZH2 silencing by siRNA strategy or DZNep, MS1943 that reduces EZH2 protein levels, significantly inhibited cell growth in LPCs by hampering ribosome biogenesis. In addition, decline in EZH2 protein level induces pigmented cell phenotype by inducing melanin biosynthesis. Proteasomal inhibitor, MG132 treatment induced EZH2 protein levels in HPCs prompted us to look for differentially regulated ubiquitin system proteins in HPC vs LPCs. UBE2L6, E2 conjugating enzyme has been shown to be downregulated significantly in LPCs by UHRF1-mediated CpG methylation. Both biochemical assays and animal studies demonstrated that UBE2L6 expression decline, in turn, promotes EZH2 protein stability due to lack of ubiquitination on K381 residue in LPCs. UBR4 cooperates with UBE2L6 to facilitate this ubiquitination process. Targeting UHRF1/UBE2L6/UBR4 axis can be a better treatment option to trigger HPC state in melanoma in which conventional EZH2 inhibitors are ineffective.

cancer biology↗

bioRxiv2020

A peptide-signal amplification strategy for the detection and validation of neoepitope presentation on cancer biopsies

Targeting the right cancer-specific peptides presented by Human Leukocyte antigen (HLA) class I and II molecules on the tumor cell surface is a crucial step in cancer immunotherapy. Numerous approaches have been proposed to predict the presentation of potential neoepitopes that may be targeted through immune-based therapies. Often founded on patient specific somatic mutations, the routine validation of their actual appearance on the tumor cell surface is a significant barrier to realising personalized cancer immunotherapy. This can be attributed to the lack of robust and adaptable assays for antigen presentation that offer the required sensitivity to deal with the limited amounts of patient tumor tissue available. Rather than personalize individual assays we propose the use mass spectrometry to identify tumor neoepitopes from HLA-bound peptides directly isolated form the surface of tumor biopsies. We have developed a microscale HLA-peptide complex immunoprecipitation protocol combined with tandem mass tagging (TMT) to directly sequence HLA-bound peptides using mass spectrometry. Using this strategy, we identified HLA-bound peptides from as few as ~1000 cultured cells and from a small piece (~1 mg) of whole melanoma tumour tissue, encompassing epitopes derived from Melanoma-associated antigens and potential neoantigens.

immunology↗

bioRxiv2019

The Hippo pathway oncoprotein YAP promotes melanoma cell invasion and spontaneous metastasis

Melanoma is a deadly form of skin cancer that accounts for a disproportionally large proportion of cancer-related deaths in younger people. Compared to most other skin cancers, a feature of melanoma is its high metastatic capacity, although molecular mechanisms that confer this are not well understood. The Hippo pathway is a key regulator of organ growth and cell fate that is deregulated in many cancers. To analyse the Hippo pathway in cutaneous melanoma, we generated a transcriptional signature of pathway activity in melanoma cells. Hippo-mediated transcriptional activity varied in melanoma cell lines but failed to cluster with known genetic drivers of melanomagenesis such as BRAF and NRAS mutation status. Instead, it correlated strongly with published gene expression profiles linked to melanoma cell invasiveness. Consistent with this, the central Hippo oncogene, YAP, was both necessary and sufficient for melanoma cell invasion in vitro. In in vivo murine studies, YAP promoted spontaneous melanoma metastasis, whilst the growth of YAP-expressing primary tumours was impeded. Finally, we identified the YAP target genes AXL, THBS1 and CYR61 as key mediators of YAP-induced melanoma cell invasion. These data suggest that the Hippo pathway is a critical regulator of melanoma metastasis.

cancer biology↗