Biology subjects

Kessler, L.

Publications and source records attributed to Kessler, L..

8 recordsLinked to original sources

bioRxiv2026

Combined Menin and XPO1 inhibition drive synergistic antileukemic activity in KMT2Ar and NPM1-m AML

Menin scaffolds the oncogenic histone-lysine-N-methyltransferase (KMT2A)-fusion protein (FP) complex in KMT2A-r and wild-type KMT2A complex in NPM1-m acute myeloid leukemia (AML). Menin inhibitors (MIs) are effective in KMT2A-r AML and NPM1-m AML. However, not all patients respond to MIs as monotherapy. In this preclinical study, we demonstrate that the MI ziftomenib, in combination with the XPO1 inhibitor selinexor, synergistically inhibited the growth of multiple KMT2A-r and NPM1-m AML cell lines (CI<1). The combination suppressed colony formation in primary CD34+ KMT2A-r progenitor cells without affecting normal stem cells. Robust apoptosis and decreased G2/M populations were also evident. The combination downregulated HOXA9 and MEIS1 while upregulating monocytic differentiation marker CD11b in both the AML molecular signatures. RNA sequencing and proteomic analysis in KMT2A-r revealed suppression of multiple bona fide menin-KMT2A target genes. Our mechanistic studies also identified a novel role of XPO1 in stabilizing menins binding to chromatin and its interactions with KMT2A and KMT2A/MLLT3. XPO1 inhibitor-mediated disruption of these interactions, particularly in combination with ziftomenib, synergistically impairs oncogenic transcriptional programs. In vivo, combination therapy improved survival in both MV4;11 and OCI-AML3 cell line and primary patient-derived KMT2A-r and NPM1-m AML xenograft models in NSG mice, effective even at reduced drug doses. These preclinical findings demonstrate that simultaneous inhibition of the menin-KMT2A interaction and XPO1 can be a more effective translational strategy for treating KMT2A-r and NPM1-m AML than MI monotherapy to deepen responses and delay/prevent relapses.

cancer biology↗

bioRxiv2024

The farnesyl transferase inhibitor KO-2806 re-sensitizes relapsing tumors to RAS inhibition

Resistance remains a key issue limiting the clinical benefit from RAS-targeting therapeutic agents and necessitates combination approaches. We identify persistent mTORC1 activity in preclinical KRAS-mutant NSCLC and CRC models as a frequent, nongenetic driver of inherent and adaptive resistance to RAS inhibition. This vulnerability is targetable with the farnesyl transferase inhibitor KO-2806, which blocks mTORC1 activation via RHEB while sparing mTORC2 and its associated toxicities. The addition of KO-2806 to NSCLC or CRC tumors progressing on mutant-selective RAS inhibitors led to rapid and durable tumor regression. In contrast, switching from mutant-selective to pan-RAS inhibitor monotherapy resulted in only stasis of NSCLC tumors and had no effect on CRC tumor progression. Further, the addition of KO-2806 rescued sensitivity of progressing tumors to the pan-RAS inhibitor RMC-6236. Our results establish mTORC1 as an important mediator of escape from RAS inhibition and highlight KO-2806 as a promising RAS companion inhibitor in patients with prior RAS inhibitor exposure. SignificanceUtilizing in vivo models of tumor relapse, we define a subset of RAS inhibitor-resistant tumors in which vertical inhibition of MAPK is insufficient to restore sensitivity. By controlling parallel mTORC1 activity, KO-2806 may expand utility of RAS inhibitors in patients that have progressed on RAS-targeted therapy, regardless of inhibitor class.

cancer biology↗

bioRxiv2024

Rapid depletion and super-resolution microscopy reveal an unexpected role of the nuclear-speckle protein SRSF5 in paraspeckle assembly and dynamics during cellular stress

Nuclear speckles (NS) and paraspeckles (PS) are adjacent condensates with distinct protein composition, with serine-arginine-rich splicing factors (SRSFs) concentrated in NS. Surprisingly, we find that SRSF5 is present in both. Combining super-resolution imaging, proximity proteomics and iCLIP, we show that SRSF5 binds with PS core proteins to the PS-scaffold RNA NEAT1 and locates between PS spheres. Acute SRSF5 depletion results in reduced PS with differently packaged NEAT1. Under stress, SRSF5s association with PS increases, and without SRSF5, PS cluster assembly is impaired. Interfering with binding to purine-rich RNAs even causes PS-NS fusion. In an intriguing over-compensation, longer SRSF5 depletion reduces TDP-43 levels via premature polyadenylation, leading to NEAT1 isoform switching and more PS. We propose that SRSF5 forms a stress-specific PS shell and acts as a glue for PS clusters. Additionally, we uncover SRSF5 as a novel regulator of TDP-43 and demonstrate how acute depletion distinguishes direct from compensatory effects. HighlightsO_LINS protein SRSF5 associates with PS shells and enriches between PS spheres C_LIO_LISRSF5 binds the PS-scaffold RNA NEAT1 and ensures proper NEAT1 packaging C_LIO_LISRSF5 association with PS increases under stress and promotes cluster formation C_LIO_LIInterfering with binding to purine-rich RNAs causes the fusion of PS and NS C_LIO_LIAcute SRSF5 depletion reveals compensatory effects on PS assembly and dynamics C_LIO_LISRSF5 regulates TDP-43 levels via premature polyadenylation C_LI

cell biology↗

bioRxiv2024

Activity and function of the endothelial sodium channel is regulated by the effector domain of MARCKS like protein 1 in mouse aortic endothelial cells

The endothelial sodium channel (EnNaC) plays an important role in regulating vessel stiffness. Here, we investigated the regulation of EnNaC in mouse aortic endothelial cells (mAoEC) by the actin cytoskeleton and lipid raft association protein myristoylated alanine-rich C-kinase substrate like protein 1 (MLP1). We hypothesized that mutation of specific amino acid residues within the effector domain of MLP1 or loss of association between MLP1 and the anionic phospholipid phosphate PIP2 would significantly alter membrane association and EnNaC activity in mAoEC. mAoEC transiently transfected with a mutant MLP1 construct (three serine residues in the effector domain replaced with aspartate residues) showed a significant decrease in EnNaC activity compared to cells transfected with wildtype MLP1. Compared to vehicle treatment, mAoEC treated with the PIP2 synthesis blocker wortmannin showed less colocalization of EnNaC and MLP1. In other experiments, Western blot and densitometric analysis showed a significant decrease in MLP1 and caveloin-1 protein expression in mAoEC treated with wortmannin compared to vehicle. Finally, wortmannin treatment decreased sphingomyelin content and increased membrane fluidity in mAoEC. Taken together, our results suggest constitutive phosphorylation of MLP1 attenuates the function of EnNaC in aortic endothelial cells by a mechanism involving a decrease in association with MLP1 and EnNaC at the membrane, while deletion of PIP2 decreases MARCKS expression and overall membrane fluidity.

physiology↗

bioRxiv2024

CNVizard: a lightweight streamlit application for an interactive analysis of copy number variants

Methods to call, analyze and visualize copy number variations (CNVs) from massive parallel sequencing data have been widely adopted in clinical practice and genetic research. To enable a streamlined analysis of CNV data, comprehensive annotation and good visualization are indispensable. The ability to detect single exon CNVs is another important feature for genetic testing. Nonetheless, most available open-source tools come with limitations in at least one of these areas. One drawback is that available tools deliver data in an unstructured and static format which requires subsequent visualization and formatting efforts. Here we present CNVizard, a lightweight streamlit app which requires minimal computational knowledge, and which is compatible with widely used CNV processing tools (CNVkit and AnnotSV). CNVizard can process short- and long-read sequencing data and provides an intuitive webapp-like experience enabling an interactive visualization of CNV data.

bioinformatics↗

bioRxiv2023

Tipifarnib potentiates the antitumor effects of PI3Kα inhibition in PIK3CA- and HRAS-dysregulated HNSCC via convergent inhibition of mTOR activity

Outcomes for patients with recurrent/metastatic (R/M) head and neck squamous cell carcinoma (HNSCC) are poor, with median overall survival ranging from 6 to 18 months. For those who progress on standard of care (chemo)immunotherapy, treatment options are limited, necessitating the development of rational therapeutic strategies. Toward this end, we targeted the key HNSCC drivers PI3K-mTOR and HRAS via the combination of tipifarnib, a farnesyltransferase inhibitor, and alpelisib, a PI3K inhibitor, in multiple molecularly defined subsets of HNSCC. We find that tipifarnib synergizes with alpelisib at the level of mTOR in PI3K-or HRAS-dependent HNSCCs, leading to marked cytotoxicity in vitro and tumor regression in vivo. Based on these findings, we have launched the KURRENT-HN trial to evaluate the effectiveness of this combination in PIK3CA-mutant/amplified and/or HRAS-overexpressing R/M HNSCC. Preliminary evidence supports the clinical activity of this molecular biomarker-driven combination therapy. SignificanceBacked by strong mechanistic rationale, the combination of alpelisib and tipifarnib has the potential to benefit >45% of R/M HNSCC patients. By blocking feedback reactivation of mTORC1, tipifarnib may prevent adaptive resistance to additional targeted therapies, thereby enhancing their clinical utility.

cancer biology↗

bioRxiv2022

Rnf20 shapes the endothelial control of heart morphogenesis and function

During embryogenesis, distinct cardiac cell types form, which shape the structural and functional properties of the heart. How their activity is coordinated is largely unknown. Here we show that Rnf20 is a multifaceted regulator of cardiac morphogenesis and function. On the one hand, Rnf20 controls extracellular matrix dynamics and endothelial-cardiomyocyte crosstalk essential for second heart field development. On the other hand, it safeguards endothelial cell identity and function by maintaining physiological angiocrine signaling and preventing endothelial-to-mesenchymal transition. Endothelial-specific deletion of Rnf20 led to ventricular septal defects, myocardial thinning and cardiac dysfunction as a result of aberrant signaling and excessive extracellular matrix deposition that induced precocious cardiomyocyte binucleation and irregular contractility. Furthermore, we uncovered upstream factors (e.g. Sox9) and multiple angiocrine and extracellular matrix molecules that alter cardiomyocyte functionality upon endothelial Rnf20 loss. In summary, our work identifies a novel, endothelial-specific role of Rnf20 in regulating cardiac morphogenesis and function.

developmental biology↗

bioRxiv2020

Prevalence of pathogenic variants in DNA damage response genes in patients undergoing cancer risk assessment and reporting a personal history of early-onset renal cancer

PurposePathogenic variants (PVs) in a number of genes are known to increase the risk of hereditary renal cancer (hRC). However, many early-onset RC (eoRC) patients undergoing genetic testing lack PVs in hRC genes; thus, their genetic risk remains undefined. To determine if PVs in DNA damage response (DDR) genes are enriched in a convenience sample of eoRC patients undergoing genetic testing. Materials and MethodsRetrospective review of results for 844 unselected eoRC patients, undergoing genetic testing with a multi-gene cancer panel by Ambry Genetics [between July 2012 and December 2016]. The patients were tested with CancerNext and/or CancerNext Expanded panels for a variety of indications. Identified PVs were compared with patient characteristics. ResultsMean age of RC diagnosis was 48 years [range 24-60]. In addition to eoRC, 57.9% patients tested reported at least one additional cancer; breast cancer being the most common (40.1% of females, 2.5% of males). PVs in cancer risk genes were identified in 12.8% of patients--3.7% in RC-specific genes, and 8.55% in DDR genes. DDR gene PVs were most commonly identified in CHEK2, BRCA1/2, and ATM. Among the 2.1% of patients with a BRCA1/2 PV, <50% reported a personal history of hereditary breast/ovarian-associated cancer. No association between age of RC diagnosis, and prevalence of PVs in RC-specific or DDR genes was observed. ConclusionsMulti-gene panel testing including DDR genes may provide a more comprehensive risk assessment in unselected eoRC patients, and their families. Validation in larger datasets is needed to characterize the association with eoRC.

genetics↗