Biology subjects

Brothers, S.

Publications and source records attributed to Brothers, S..

6 recordsLinked to original sources

bioRxiv2024

Identification of targetable epigenetic vulnerabilities in uveal melanoma

Uveal melanoma (UM) is the most common primary intraocular malignancy in adults, with a strong predilection for hepatic metastasis, occurring in approximately 50% of cases. Metastatic UM remains highly resistant to therapy and is almost invariably fatal. The strongest genetic drivers of UM metastasis are loss-of-function mutations in tumor suppressor BAP1, an epigenetic regulator that serves as the ubiquitin hydrolase subunit of the polycomb repressive deubiquitinase (PR-DUB) complex, and a key player in global epigenetic regulation. Inactivation of BRCA Associated Protein 1 (BAP1) has been shown to induce widespread epigenetic alterations across multiple model systems. To identify novel therapeutic strategies, we investigated whether targeting the epigenome could reveal new vulnerabilities in UM. We performed high-throughput compound screening using a curated epigenetic inhibitor library and identified BET (bromodomain and extra-terminal domain) inhibition as a particularly promising approach. Interestingly, we observed significant heterogeneity in the efficacy of different BET inhibitors in UM. While previous clinical trials with two BET inhibitors have failed to show efficacy in UM, our findings highlight substantial differences in the potency of specific BET inhibitors for this malignancy. Notably, the BET inhibitor mivebresib (ABBV-075) significantly improved survival rates by 50% in a metastatic UM xenograft mouse model and completely prevented detectable metastases in the bones, spinal cord, and brain. Unexpectedly, RNA sequencing revealed a strong transcriptional overlap between BET inhibition and histone deacetylase (HDAC) inhibition--an approach currently under clinical evaluation for UM treatment. Both BET and HDAC inhibitors reversed gene expression signatures associated with high metastatic risk and induced a neuronal differentiation-like phenotype in UM cells. Together, our findings demonstrate that UM cells exhibit a distinct vulnerability to BET inhibition and establish BET inhibitors as promising candidates for further clinical evaluation for metastatic UM.

cancer biology↗

bioRxiv2023

Heterogeneous Nuclear Ribonucleoprotein C is an Indispensable Target in Acute Myeloid Leukemia

Refractory disease is the greatest challenge in acute myeloid leukaemia (AML). Previously, we found vascular-associated AML cells as a source for refractory disease. In this study we use a bioassay of AML cells co-cultured on bone marrow-derived endothelial cells (BMECs) to screen 31 million compounds within a mixture-based synthetic combinatorial library followed by deconvolution leading to the identification of a novel polyamine sulfonamide that is selectively toxic to AML. Using three distinct proteomics methods we identified heterogeneous nuclear ribonucleoprotein C (HNRNPC) as the compound target. Depleting HNRNPC reduces AML cell proliferation, viability, colony formation and fails to establish AML in mice. In contrast, no changes in cell proliferation, survival, or colony outgrowth were observed when depleting HNRNPC in normal hematopoietic or stromal cells. Clinical data show that lower HNRNPC expression independently associates with prolonged survival times in 554 adult and pediatric AML patients. We show that HNRNPC regulates DNA replication initiation and the Myc transcriptional program. Using differential isoform expression and differential alternative splicing analyses, we show significant alternative splicing of MAX after HNRNPC depletion, resulting in MAX transcript isoforms that lack Myc-interacting domains, which we term non-activating MAX isoforms. These Myc-interacting domains are necessary for the obligate heterodimerization of Myc and Max and are critical for Myc transcriptional activation. We further analyzed the alternative splicing landscapes of 538 AML patients and 33 specimens from healthy individuals and show substantial alternative splicing of mRNA in AML patients despite the absence of splicing factor gene mutations. Moreover, we found significantly high expression of non-activating MAX isoforms in healthy individuals, while AML patients highly expressed fully functional MAX isoforms, suggesting that MAX splicing may serve an important functional role in AML. Together, these data show HNRNPC as an indispensable splicing repressor in AML that is necessary for supporting deregulated Myc-Max activity and suggest HNRNPC as a potential therapeutic target for AML.

cancer biology↗

bioRxiv2022

STAT3 gain-of-function mutations connect leukemia with autoimmune disease by pathological dysregulation of NKG2Dhi CD8 killer T cells

The association between cancer and autoimmune disease is unexplained, exemplified by T-cell large granular lymphocytic leukemia (T-LGL) where gain-of-function somatic mutations in STAT3 correlate with co-existing autoimmunity. To resolve whether these mutations are the cause or consequence of CD8 clonal expansions and autoimmunity, here we analyse patients with germline STAT3 GOF syndrome and mice with the T-LGL mutation STAT3K658Nor the most common germline mutation, STAT3T716M. STAT3 GOF mutations drove accumulation of effector CD8 T cell clones highly expressing the NKG2D receptor for MHC-I-related molecules expressed on stressed cells, and the genes for inflammatory/cytotoxic granzymes, perforin, interferon-{gamma} and Ccl5/Rantes. CD8 cells were essential to lethal disease in Stat3K658Nmice and their accumulation required NKG2D and the receptor for IL-15 and IL-2, IL2RB. These results demonstrate that STAT3 GOF mutations cause effector CD8 T cell oligoclonal accumulation and that these rogue T cells contribute to autoimmune pathology, supporting the hypothesis that somatic mutations in leukemia/lymphoma driver genes contribute to autoimmune disease. IN BRIEFLeukemia and autoimmune-associated STAT3 gain-of-function mutations dysregulate CD8 T cells to cause autoimmune pathology and oligoclonal expansion of cytotoxic killer CD8 T cells, that depend upon NKG2D and IL2RB receptors for signals displayed on stressed, damaged, infected, or mutated tissues.

immunology↗

bioRxiv2021

Overactive STAT3 drives accumulation of disease-associated CD21low B cells

Dysregulated STAT3 signalling is correlated with antibody-mediated autoimmunity and B- cell neoplasia, but its effect on B cells is underexplored. Here we address this in children with STAT3 gain-of-function (GOF) syndrome and in mice with STAT3T716M, the most common STAT3 GOF syndrome human mutation, or STAT3K658N, a dimerization interface mutation responsible for STAT3 GOF syndrome in two children. The main B cell consequence of overactive STAT3 was accumulation of CD19high CD21low atypical memory B cells in humans and of CD21low CD23low B cells in mice resembling age-associated B cells expressing T-bet, CD11c and plasma cell differentiation genes. Overactive STAT3 within B cells increased expression of many genes in the B cell receptor and T cell help pathways, increased the tolerogenic receptor CD22, but opposed B cell tolerance checkpoints and increased formation of T-bet+ B cells upon BCR and CD40 stimulation. These results reveal overactive STAT3 as a central driver of a key class of disease- associated B-lymphocytes in humans and mice.

immunology↗

bioRxiv2019

Incomplete resilience of a shallow lake to a brownification event

Dissolved organic carbon (DOC) concentrations in many freshwater ecosystems of the northern hemisphere have increased in recent decades due to additional terrestrial inputs. This phenomenon, known as brownification, can strongly alter the physical, chemical, and biological traits of aquatic ecosystems. Extreme rainfall can also cause sudden brownification, known as blackwater events in rivers, while longer term effects on lakes are unknown. Here, we investigated the resilience of a small, temperate, shallow lake to a strong natural flooding-induced brownification event in 2011-2012. From initial DOC and total phosphorus (TP) concentrations of ~12 and 0.04 mg L-1, respectively, the lake rapidly reached peak DOC and TP concentrations of 60 and 0.35 mg L-1, respectively. By the following year, water levels had returned close to initial values, yet two additional years of monitoring (until summer 2015) and a more recent sample in spring 2019 showed that the lake did not fully return to its pre-brownification state. Instead, DOC and TP concentrations plateaued at concentrations respectively 1.5-fold and twofold greater than pre-brownification values within less than two years and remained at these concentrations in spring 2019. During this initial recovery period the lake exhibited a decline of phytoplankton and a partial recovery of summer periphyton biomass and production, albeit a full return to pre-brownification values was not recorded in either case. DOC and TP concentrations were positively correlated to phytoplankton biomass and negatively to periphyton. As increases in phytoplankton production outpaced decreasing periphyton production, the net result of this brownification event has been an increase in whole-lake areal summertime primary production. This incomplete resilience to a flooding-induced brownification event implies consequences for several ecological and biogeochemical functions of shallow lakes that warrant further investigation and might contribute to the gradual increase of freshwater DOC concentrations in the northern hemisphere.

ecology↗

bioRxiv2018

Human IL-2 receptor β mutations associated with defects in immunity and peripheral tolerance

Interleukin-2, which conveys essential signals for effective immunity and immunological tolerance, operates through a heterotrimeric receptor comprised of , {beta} and {gamma} chains. Genetic deficiency of the or {gamma} chain causes debilitating disease. Here we identify human interleukin-2 receptor (IL-2R) {beta} chain (CD122) gene defects as a cause of life-threatening dysregulation of immunity and peripheral tolerance. We report homozygous mutations in the human IL-2R{beta} gene from four consanguineous families, comprising either recessive missense mutations in five children or an early stop-gain mutation in two deceased fetuses and a premature neonate. All patients surviving to childhood presented with autoantibodies, hypergammaglobulinemia, bowel inflammation, and dermatological abnormalities, as well as cytomegalovirus disease in most cases. Patient T lymphocytes lacked surface expression of IL-2R{beta} and were unable to normally respond to high-dose IL-2 stimulation. By contrast, patient natural killer (NK) cells retained partial IL-2R{beta} expression and cytotoxic function. IL-2R{beta} loss of function was recapitulated in a recombinant system, in which endoplasmic reticulum sequestration was revealed as the mechanism by which certain missense mutations cause disease. Hematopoietic stem cell transplant resulted in resolution of clinical symptoms in one patient. The hypomorphic nature of this disease highlights the significance of variable IL-2R{beta} expression in different lymphocyte subsets as a means of modulating immune function. Insights from these patients can inform the development of IL-2-based therapeutics for immunological diseases and cancer.

immunology↗