Tubulin Binding Research Articles

Drug-Linker Constructs Bearing Unique Dual-Mechanism Tubulin Binding Payloads Tethered through Cleavable and Non-Cleavable Linkers

Antibody-drug conjugates (ADCs) have advanced as a mainstay among the most promising cancer therapeutics, offering enhanced antigen targeting and encompassing wide diversity in their linker and payload components. Small-molecule inhibitors of tubulin polymerization have found success as payloads in FDA approved ADCs and represent further promise in next-generation, pre-clinical and developmental ADCs. Unique dual-mechanism payloads (previously designed and synthesized in our laboratories) function as both potent antiproliferative agents and promising vascular disrupting agents capable of imparting selective and effective damage to tumor-associated microvessels. These payloads have been incorporated into a variety of drug-linker constructs utilizing the clinically relevant cathepsin B cleavable Val-Cit dipeptide linker, employed within several FDA approved ADCs, along with other non-cleavable constructs. Various synthetic strategies were evaluated to prepare these drug-linker constructs. Aniline-based payloads were incorporated utilizing the Val-Cit dipeptide linker similar to FDA approved ADCs such as Adcetris® (brentuximab vedotin). An additional self-immolative group, previously described in the literature for related model systems, was employed to tether the phenolic payloads. A variety of drug-linker constructs (with each bearing a unique dual mechanism payload) were synthesized and evaluated biologically for their enzyme-mediated release of payload and inhibition of tubulin polymerization. Following deactivation of the highly electrophilic maleimido terminus as its corresponding N-acetyl cysteine (NAC) derivative, the most promising construct (NAC-4) demonstrated approximately 90% release of an aniline-functionalized payload (1) upon treatment with cathepsins B or L over 90 minutes. Building on these promising results, future studies will examine the conjugation of drug-linker construct 4 to selected antibodies and engineered proteins and evaluate the biological activity of the resultant antibody-drug conjugates (ADCs).

Structural Insights into the Role of the Proline Rich Region in Tau Function.

Tau is a microtubule–associated protein that plays an important role in modulating axonal microtubules in neurons. Intracellular tau aggregates are found in a broad class of disorders, including Alzheimer&#8242s disease, termed tauopathies. Tau is an intrinsically disordered protein, and its structural disorder appears to be critical to its microtubule-related functions. Tubulin binding sites are found in tau&#8242s proline-rich region (PRR), microtubule binding repeats (MTBR: R1–R4), and pseudo–repeat, R′. While many post-translational modifications have been identified on tau, phosphorylation sites, which both regulate tubulin dimer and microtubule interactions and are correlated with disease, cluster with high frequency within the PRR. Here, we use fluorescence correlation spectroscopy and structural mass spectrometry techniques to characterize the impact of phosphomimic mutations in the PRR on tubulin dimer binding and probe the structure of the PRR–tubulin dimer complex. We find that phosphomimics cumulatively diminish tubulin dimer binding and slow microtubule polymerization. Additionally, we map two ~15 residue regions of the PRR as primary tubulin dimer binding sites and propose a model in which PRR enhances lateral interactions between tubulin dimers, complementing the longitudinal interactions observed for MTBR. Together these measurements provide insight into the previously overlooked relevance of tau&#8242s PRR in functional interactions with tubulin.

Discovery and biological evaluation of 6-aryl-4-(3,4,5-trimethoxyphenyl)quinoline derivatives with promising antitumor activities as novel colchicine-binding site inhibitors

Tubulin, as the fundamental unit of microtubules, is a crucial target in the investigation of anticarcinogens. The synthesis and assessment of small-molecule tubulin polymerization inhibitors remains a promising avenue for the development of novel cancer therapeutics. Through an analysis of reported colchicine-binding site inhibitors (CBSIs) and tubulin binding models, a set of 6-aryl-4-(3,4,5-trimethoxyphenyl)quinoline derivatives were meticulously crafted as potential CBSIs. Notably, compound 14u exhibited potent anti-proliferative efficacy, displaying IC50 values ranging from 0.03 to 0.18 μM against three human cancer cell lines (Huh7, MCF-7, and SGC-7901). Mechanistic investigations revealed that compound 14u could disrupt tubulin polymerization, dismantle the microtubule architecture, arrest the cell cycle at G2/M phase, and induce apoptosis in cancer cells. Furthermore, compound 14u demonstrated significant inhibition of tumor proliferation in vivo with no discernible toxicity in the Huh7 orthotopic tumor model mice. Additionally, physicochemical property predictions indicated that compound 14u adhered well to Lipinski's rule of five. These findings collectively suggest that compound 14u holds promise as an antitumor agent targeting the colchicine-binding site on tubulin and warrants further investigation.

NP-Collabs: Investigating Counterion-Mediated Bridges in the Multiply Phosphorylated Tau-R2 Repeat.

Tau is an intrinsically disordered (IDP) microtubule-associated protein (MAP) that plays a key part in microtubule assembly and organization. The function of tau can be regulated by multiple phosphorylation sites. These post-translational modifications are known to decrease the binding affinity of tau for microtubules, and abnormal tau phosphorylation patterns are involved in Alzheimer's disease. Using all-atom molecular dynamics simulations, we compared the conformational landscapes explored by the tau R2 repeat domain (which comprises a strong tubulin binding site) in its native state and with multiple phosphorylations on the S285, S289, and S293 residues, with four different standard force field (FF)/water model combinations. We find that the different parameters used for the phosphate groups (which can be more or less flexible) in these FFs and the specific interactions between bulk cations and water lead to the formation of a specific type of counterion bridge, termed nP-collab (for nphosphate collaboration, with n being an integer), where counterions form stable structures binding with two or three phosphate groups simultaneously. The resulting effect of nP-collabs on the tau-R2 conformational space differs when using sodium or potassium cations and is likely to impact the peptide overall dynamics and how this MAP interacts with tubulins. We also investigated the effect of phosphoresidue spacing and ionic concentration by modeling polyalanine peptides containing two phosphoserines located one-six residues apart. Three new metrics specifically tailored for IDPs (proteic Menger curvature, local curvature, and local flexibility) were introduced, which allow us to fully characterize the impact of nP-collabs on the dynamics of disordered peptides at the residue level.

Exploration of small molecule compounds targeting abdominal aortic aneurysm based on CMap database and molecular dynamics simulation.

The mitigation of abdominal aortic aneurysm (AAA) growth through pharmaceutical intervention offers the potential to avert the perils associated with AAA rupture and the subsequent need for surgical intervention. Nevertheless, the existing effective drugs for AAA treatment are limited, necessitating a pressing exploration for novel therapeutic medications. AAA-related transcriptome data were downloaded from GEO, and differentially expressed genes (DEGs) in AAA tissue were screened for GO and KEGG enrichment analyses. Small molecule compounds and their target proteins with negative connectivity to the AAA expression profile were predicted in the Connectivity Map (CMap) database. Molecular docking and molecular dynamics simulation were performed to predict the binding of the target protein to the small molecule compound, and the MM/GBSA method was used to calculate the binding free energy. Cluster analysis was performed using the cluster tool in the GROMACS package. An AAA cell-free model was built, and CETSA experiments were used to demonstrate the binding ability of small molecules to the target protein in cells. A total of 2244 DEGs in AAA were obtained through differential analysis, and the DEGs were mainly enriched in the tubulin binding biological function and cell cycle pathway. The CMap results showed that Apicidin had a potential therapeutic effect on AAA with a connectivity score of -97.74, and HDAC4 was the target protein of Apicidin. Based on literature, HDAC4-Apicidin was selected as the subsequent research object. The lowest affinity of Apicidin-HDAC4 molecular docking was -8.218kcal/mol. Molecular dynamics simulation results indicated that Apicidin-HDAC4 could form a stable complex. MM/GBSA analysis showed a total binding free energy of -55.40 ± 0.79kcal/mol, and cluster analysis showed that there were two main conformational clusters during the binding process, accounting for 22.4% and 57.8%, respectively. Apicidin could form hydrogen bonds with surrounding residues for stable binding. CETSA experiment proved the stable binding ability of Apicidin and HDAC4. Apicidin inhibited HDAC4 in AAA and exhibited favorable protein-ligand interactions and stability, making it a potential candidate drug for treating AAA.

In vitro and in vivo evaluation of Bombesin-MMAE conjugates for targeted tumour therapy

Targeted tumour therapy has proved to be an efficient alternative to overcome the limitations of conventional chemotherapy. The upregulation of the bombesin receptor 2 (BB2) in several malignancies and the advantages offered by peptide drug conjugates over antibody drug conjugates in terms of production and tumour targeting motivated us to synthesise and test bombesin conjugates armed with the tubulin binder monomethyl auristatin E. The widely used Val-Cit-PABC was initially included as cathepsin cleavable self-immolative linker for the release of the free drug. However, the poor stability of the Val-Cit-conjugates in mouse plasma encouraged us to consider the optimised alternatives Glu-Val-Cit-PABC and Glu-Gly-Cit-PABC. Conjugate BN-EVcM1, featuring Glu-Val-Cit-PABC, combined suitable stability (t(½) in mouse and human plasma: 8.4 h and 4.6 h, respectively), antiproliferative activity in vitro (IC50 = 29.6 nM on the human prostate cancer cell line PC-3) and the full release of the free payload within 24 h. Three conjugates, namely BN-EGcM1, BN-EVcM1 and BN-EVcM2, improved the accumulation of MMAE in PC-3 human prostate cancer xenograft mice models, compared to the administration of the free drug. Among them, BN-EVcM1 also stood out for the significantly extended survival of mice in in vivo acute efficacy studies and for the significant inhibition of the growth of a PC-3 tumour in mice in both acute and chronic efficacy studies.

STMND1 is a phylogenetically ancient stathmin which localizes to motile cilia and exhibits nuclear translocation that is inhibited when soluble tubulin concentration increases.

Stathmins are small, unstructured proteins that bind tubulin dimers and are implicated in several human diseases, but whose function remains unknown. We characterized a new stathmin, STMND1 (Stathmin Domain Containing 1) as the human representative of an ancient subfamily. STMND1 features a N-terminal myristoylated and palmitoylated motif which directs it to membranes and a tubulin-binding stathmin-like domain (SLD) that contains an internal nuclear localization signal. Biochemistry and proximity labeling showed that STMND1 binds tubulin, and live imaging showed that tubulin binding inhibits translocation from cellular membranes to the nucleus. STMND1 is highly expressed in multiciliated epithelial cells, where it localizes to motile cilia. Overexpression in a model system increased the length of primary cilia. Our study suggests that the most ancient stathmins have cilium-related functions that involve sensing soluble tubulin.

Interaction of norsecurinine-type monomeric and dimeric alkaloids with α-tubulin: a molecular docking study

Aim: New microtubule-targeting agents are needed to improve cancer treatment. The recent characterization of the anticancer alkaloid securinine as a tubulin-binding agent prompted us to explore the interaction of related monomeric and dimeric analogues with tubulin. The interaction between the α/β-tubulin dimer and alkaloids fluevirines A–F and flueggenines A–I, isolated from the bush Flueggea virosa (Roxb. ex Willd.) Royle, was investigated using molecular docking. Methods: Two molecular models were initially compared for the binding of securinine to α/β-tubulin. The pironetin-binding site model (5FNV) was selected for the subsequent docking analysis with all compounds. Empirical energies of interaction (ΔE) were measured and compared. Results: Fluevirine A has been identified as a potent tubulin binder. This dimeric alkaloid formed more stable complexes with tubulin than the monomeric counterparts, such as fluevirines B–D. The bis-indole derivative fluevirine E also provided more stable complexes than (nor)securinine. The study was extended to the dimeric alkaloids flueggenines A–I and three compounds were identified as potential tubulin binders: the polycyclic product flueggenine B, the norsecurinine-indole hybrid flueggenine E, and the norsecurinine dimer flueggenine I. This later compound proved to be well adapted to fit into the pironetin site of tubulin, extending its two norsecurinine units between the colchicine-binding area and the pironetin site, in close proximity to the pironetin-reactive cysteine-316 residue. Structure-binding relationships were delineated. Conclusions: The study identifies the dimeric alkaloids fluevirine A and flueggenine I as potential α-tubulin binding agents. For the first time, dimeric alkaloids including two C-C connected norsecurinine units are characterized as tubulin ligands. The study contributes to a better understanding of the mechanism of action of Flueggea alkaloids and should help the design of anticancer analogues targeting the pironetin site of α-tubulin.

Abstract 1848: The Cellular Thermal Shift assay and its applications in Target ID, MoA determination and biomarker discovery

Abstract With the Cellular Thermal Shift Assay (CETSA) celebrating its first decade since the PoC publication, the method has gained much interest in the basic science field as well as become an industry standard in applied drug discovery setting. In the last few years it has become apparent that in addition to providing information about drug-protein interaction, CETSA based thermal profiling of cells can help describe additional aspects of cell biology as it gives insight into the activating and rewiring of protein-protein interaction networks inside the cell upon stimuli. In the work presented here, we have used CETSA coupled to high resolution mass spectrometric readout to profile the response patterns of about 8000 proteins to several hundred molecular probes and marketed drugs. The goal has been to provide a map of wanted and unwanted effects following treatment and to correlate it to alternative readouts, by for example cellular imaging and cell death assays. We have applied the CETSA protocol for close to five hundred compounds, many in several cell-lines (HepG2, U87MG and K562). The experimental setup includes the step of treating the cells with a certain compound at a fixed concentration. After incubation for an hour, we heated the cells to a range of temperatures, followed by a lysis protocol and pooling of the samples. After this, the samples have been centrifuged to separate the soluble from insoluble fraction. The soluble fraction has then been prepared for MS acquisition using TMT based multiplexing. Typically, this allowed us to monitor changes in thermal stability among more than 8,000 proteins, as a consequence of compound treatment. This data reveals specific compound “fingerprints” that can be used to decipher mode of action and identify biomarkers. Despite the short incubation time, proteins with compound-induced thermal stability shifts are not only targets/off-targets (direct binders), but also downstream, and sometimes upstream, pathway members and general cellular responses. All data combined makes the basis of the Target Engagement Atlas. Here we can see clusters of compounds, sharing similar protein binding profiles. Among the most prominent ones are mTOR inhibitors, NSAIDs, as well as tubulin binders. Alternatively, one can use this resource to reveal clusters of “pharmacologically” associated protein networks. We show that pharmacological perturbation allows identification of clusters representing tight protein complexes (for example ribosomes), known metabolic pathways (folate biosynthesis), molecular functions (kinases), as well as networks of proteins linked only by ligand binding specificity. CETSA MS allows for unbiased, cellular, and molecular profiling of compound effects. Together with data from clinical settings, as well as in vivo/in vitro end point assays it is possible to correlate the CETSA patterns to wanted but also unwanted responses. Citation Format: Tomas Friman, Alexey Chernobrovkin, Tuomas Tolvanen, Erin Gilson, Stina Lundgren, Victoria Brehmer, Daniel Martinez Molina. The Cellular Thermal Shift assay and its applications in Target ID, MoA determination and biomarker discovery [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1848.

Abstract 5814: EPriL macrocycles as a platform for the rapid generation of effective kinase degrader antibody conjugates (DACs)

Abstract The therapeutic success of antibody drug conjugates (ADCs) drives a continuous search for novel payloads that can increase therapeutic window and thereby widen the applications for ADCs. Recently, heterobifunctional degraders have gained great interest as payloads, and degrader antibody conjugates (DACs) are seen as a novel therapeutic modality. Heterobifunctional degraders consist of a small molecule ligand that binds a target (protein of interest or POI), a spacer and an E3 ligase ligand, which can catalyze target degradation. Owing to their catalytic activity, degraders can have better potency than the equivalent inhibitors, making them suitable as ADC payload [1]. Degrader payloads can target a wider variety of mechanisms than classic payloads, which use the same antitumor strategies as chemotherapy, such as tubulin binding or topoisomerase inhibition. Since many FDA-approved targeted therapies are based on the inhibition of protein kinases, we investigated degraders of these kinases as DAC payloads. Kinase DACs could bring enhanced targeting and therefore better therapeutic window to a field where classic ADC payloads have often shown substantial toxicities. As many heterobifunctional degraders show poor cell membrane penetration, their inhibitory potential could be increased as part of a DAC, where endocytic uptake is followed by intracellular release of the degrader payload. To identify kinase degrader payloads, we present a workflow based on a platform called Energetically Privileged Ligands (EPriLs). EPriLs are macrocycle scaffolds that bind non-covalently in the kinase ATP pocket. Their unique binding mode avoids contacts with amino acid positions where resistance to kinase inhibitors frequently occurs. EPriL macrocycles can be decorated appropriately to rationally design specific inhibitors for many therapeutically relevant kinases, and provide synthetic handles to couple them to VHL or CRBN ligands to generate effective kinase degraders. Here we describe how EPriL kinase degraders can be developed into effective DACs, using consecutive libraries of EPriL ligands, spacers, E3 ligase ligands and linkers. First, suitable degraders are identified, based on rapid and deep target degradation and potent antiproliferative activity on target cell lines. Degraders are then transformed into maleimide-linked degraders using convenient attachment of enzymatically cleavable linkers. In a medium throughput fashion, these maleimides are coupled to antibodies to generate DACs, which are tested for stability and biological potency. Applying this workflow to various well-validated kinase targets in oncology resulted in a promising kinase targeting DAC with favorable ADME properties, clear potentiation compared to the parent degrader, and increased selectivity for tumor cell lines. 1] Dragovich et al., Chem. Soc. Rev. (2022) 51, 3886-3897. Citation Format: Joost C. Uitdehaag, Jos e Man, Michelle Muller, Freek an Cauter, Sander an Gemert, Milan Hoffmann, Yvonne G. an Mil, Winfried R. Mulder, Martine B. Prinsen, Jan Gerard Sterrenburg, Diep Vu, Joeri e Wit, Erik Ensing, Rogier C. Buijsman. EPriL macrocycles as a platform for the rapid generation of effective kinase degrader antibody conjugates (DACs) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5814.

Abstract 4476: Novel auristatins with improved tolerability and unique bystander activity profile

Abstract Auristatins are a class of clinically validated payloads used extensively in antibody-drug conjugate (ADC) technology. There are currently 4 FDA approved ADCs utilizing the vedotin drug linker to treat an array of solid tumors and lymphomas and several more in clinical trials. Auristatin payloads have several desirable properties, including strong anticancer cytotoxicity, bystander activity, and induction of immunologic cell death. While auristatin-based ADCs have been remarkably successful, there remain opportunities to further understand and improve payload properties. Bystander activity is one such property that can greatly impact the balance between efficacy and tolerability. Herein, we present a medicinal chemistry investigation into a series of auristatins with similar tubulin binding and biochemical potency that differ in lipophilicity and ability to cross the cell membrane. This design enabled us to focus on and characterize the impact of bystander activity while maintaining all other parameters. Ultimately, this effort resulted in ADCs with similar on-target in vitro cytotoxicity but differed in the extent of off-target bystander activity. Evaluation of in vivo efficacy, in vivo bystander activity, and rodent tolerability afforded a lead drug linker that was well-tolerated as an ADC and exhibited strong antitumor growth delay. Citation Format: Philip N. Moquist, Nicole M. Eng-Duncan, Tim Bovee, Katie Snead, Jenn Wright, Kaleb Smith, Teri Blevins, Brittney Blackburn, Michelle Ulrich, Forgivemore Magunda, Jessica Simmons, Peter D. Senter, Svetlana O. Doronina. Novel auristatins with improved tolerability and unique bystander activity profile [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4476.

A first complete catalog of highly expressed genes in eight chicken tissues reveals uncharacterized gene families specific for the chicken testis.

Based on next-generation sequencing, we established a repertoire of differentially overexpressed genes (DoEGs) in eight adult chicken tissues: the testis, brain, lung, liver, kidney, muscle, heart, and intestine. With 4,499 DoEGs, the testis had the highest number and proportion of DoEGs compared with the seven somatic tissues. The testis DoEG set included the highest proportion of long noncoding RNAs (lncRNAs; 1,851, representing 32% of the lncRNA genes in the whole genome) and the highest proportion of protein-coding genes (2,648, representing 14.7% of the protein-coding genes in the whole genome). The main significantly enriched Gene Ontology terms related to the protein-coding genes were "reproductive process," "tubulin binding," and "microtubule cytoskeleton." Using real-time quantitative reverse transcription-polymerase chain reaction, we confirmed the overexpression of genes that encode proteins already described in chicken sperm [such as calcium binding tyrosine phosphorylation regulated (CABYR), spermatogenesis associated 18 (SPATA18), and CDK5 regulatory subunit associated protein (CDK5RAP2)] but whose testis origin had not been previously confirmed. Moreover, we demonstrated the overexpression of vertebrate orthologs of testis genes not yet described in the adult chicken testis [such as NIMA related kinase 2 (NEK2), adenylate kinase 7 (AK7), and CCNE2]. Using clustering according to primary sequence homology, we found that 1,737 of the 2,648 (67%) testis protein-coding genes were unique genes. This proportion was significantly higher than the somatic tissues except muscle. We clustered the other 911 testis protein-coding genes into 495 families, from which 47 had all paralogs overexpressed in the testis. Among these 47 testis-specific families, eight contained uncharacterized duplicated paralogs without orthologs in other metazoans except birds: these families are thus specific for chickens/birds.NEW & NOTEWORTHY Comparative next-generation sequencing analysis of eight chicken tissues showed that the testis has highest proportion of long noncoding RNA and protein-coding genes of the whole genome. We identified new genes in the chicken testis, including orthologs of known mammalian testicular genes. We also identified 47 gene families in which all the members were overexpressed, if not exclusive, in the testis. Eight families, organized in duplication clusters, were unknown, without orthologs in metazoans except birds, and are thus specific for chickens/birds.

First-in-Class Humanized Antibody against Alternatively Spliced Tissue Factor Augments Anti-Metastatic Efficacy of Chemotherapy in a Preclinical Model of Pancreatic Ductal Adenocarcinoma.

Alternatively spliced tissue factor (asTF) promotes the progression of pancreatic ductal adenocarcinoma (PDAC) by activating β1-integrins on PDAC cell surfaces. hRabMab1, a first-in-class humanized inhibitory anti-asTF antibody we recently developed, can suppress PDAC primary tumor growth as a single agent. Whether hRabMab1 has the potential to suppress metastases in PDAC is unknown. Following in vivo screening of three asTF-proficient human PDAC cell lines, we chose to make use of KRAS G12V-mutant human PDAC cell line PaCa-44, which yields aggressive primary orthotopic tumors with spontaneous spread to PDAC-relevant anatomical sites, along with concomitant severe leukocytosis. The experimental design featured orthotopic tumors formed by luciferase labeled PaCa-44 cells; administration of hRabMab1 alone or in combination with gemcitabine/paclitaxel (gem/PTX); and the assessment of the treatment outcomes on the primary tumor tissue as well as systemic spread. When administered alone, hRabMab1 exhibited poor penetration of tumor tissue; however, hRabMab1 was abundant in tumor tissue when co-administered with gem/PTX, which resulted in a significant decrease in tumor cell proliferation; leukocyte infiltration; and neovascularization. Gem/PTX alone reduced primary tumor volume, but not metastatic spread; only the combination of hRabMab1 and gem/PTX significantly reduced metastatic spread. RNA-seq analysis of primary tumors showed that the addition of hRabMab1 to gem/PTX enhanced the downregulation of tubulin binding and microtubule motor activity. In the liver, hRabMab1 reduced liver metastasis as a single agent. Only the combination of hRabMab1 and gem/PTX eliminated tumor cell-induced leukocytosis. We here demonstrate for the first time that hRabMab1 may help suppress metastasis in PDAC. hRabMab1's ability to improve the efficacy of chemotherapy is significant and warrants further investigation.

Dimeric Tubulin Modifies Mechanical Properties of Lipid Bilayer, as Probed Using Gramicidin A Channel.

Using the gramicidin A channel as a molecular probe, we show that tubulin binding to planar lipid membranes changes the channel kinetics-seen as an increase in the lifetime of the channel dimer-and thus points towards modification of the membrane's mechanical properties. The effect is more pronounced in the presence of non-lamellar lipids in the lipid mixture used for membrane formation. To interpret these findings, we propose that tubulin binding redistributes the lateral pressure of lipid packing along the membrane depth, making it closer to the profile expected for lamellar lipids. This redistribution happens because tubulin perturbs the lipid headgroup spacing to reach the membrane's hydrophobic core via its amphiphilic α-helical domain. Specifically, it increases the forces of repulsion between the lipid headgroups and reduces such forces in the hydrophobic region. We suggest that the effect is reciprocal, meaning that alterations in lipid bilayer mechanics caused by membrane remodeling during cell proliferation in disease and development may also modulate tubulin membrane binding, thus exerting regulatory functions. One of those functions includes the regulation of protein-protein interactions at the membrane surface, as exemplified by VDAC complexation with tubulin.

Abstract A085: First-in-class humanized antibody targeting alternatively spliced tissue factor augments anti-metastatic efficacy of chemotherapy in a preclinical model of pancreatic ductal adenocarcinoma

Abstract Introduction. Alternatively spliced tissue factor (asTF) promotes progression of pancreatic ductal adenocarcinoma (PDAC) via activating b1-integrins on PDAC cell surfaces. hRabMab1, a humanized inhibitory anti-asTF antibody we recently developed, can suppress PDAC primary tumor growth as a single agent. Whether hRabMab1 has the potential to suppress metastases in PDAC is unknown. Aim. To test hRabMab1’s ability to suppress metastatic spread in combination with chemotherapy. Methods. asTF-proficient, KRAS G12V-mutant human PDAC cell line PaCa44 yields aggressive primary orthotopic tumors that spread spontaneously to the relevant anatomical sites, accompanied by severe leukocytosis. 5 × 105 PaCa44 cells were implanted into the pancreata of NOD-SCID mice (n=40). 10 days post-implantation, mice were randomized into 4 cohorts: vehicle; hRabMab1 administered IV at 18 mg/kg; gemcitabine/paclitaxel (gem/paclitaxel, 50 mg/kg/3 mg/kg); and hRabMab1+gem/paclitaxel. Results. Post-mortem analysis of tumor tissue and luciferase imaging of the abdominal cavity showed that gem/paclitaxel alone reduced primary tumor volume, but not metastatic spread; only the combination of hRabMab1 and gem/paclitaxel significantly reduced metastatic spread (p=0.0114 vs vehicle, 1-way ANOVA). RNAseq analysis of primary tumor tissue followed by gene set enrichment of differentially expressed genes showed that the addition of hRabMab1 to gem/paclitaxel downregulated tubulin binding and microtubule motor activity. Genes involved in extracellular matrix/collagen production and neovascularization were upregulated in response to gem/paclitaxel; addition of hRabMab1 to gem/paclitaxel tentatively reduced this compensatory effect. In the liver, hRabMab1 reduced liver metastasis as a single agent (p=0.031 vs vehicle) and in combination with gem/paclitaxel (p=0.0054 vs vehicle, 1-way ANOVA). In the surgical incision site, metastatic penetrance was as follows: vehicle, 100%; hRabMab1, 100%; gem/paclitaxel, 44% (4/9); hRabMab1+gem/paclitaxel, 0% (p=0.037715, gem/paclitaxel vs hRabMab1+gem/paclitaxel, Chi square test). Only the combination of hRabMab1 and gem/paclitaxel eliminated leukocytosis; levels of neutrophils, monocytes, eosinophils, and basophils were significantly lower in the hRabMab1+gem/paclitaxel cohort vs gem/paclitaxel cohort (p=0.035, p=0.051, p=0.032, and p=0.026, respectively). Leukocytes recruited from the circulation fuel tumor progression in PDAC. To address the potential significance of white blood cell (WBC) count normalization in our model, we performed correlation analysis between WBC counts and tumor volumes across all cohorts; there was a highly significant positive correlation between these two parameters (R=0.682, p=0.00002). Conclusions. This is the first study demonstrating that hRabMab1 can suppress metastasis in PDAC. hRabMab1’s ability to improve anti-metastatic efficacy of chemotherapy is potentially significant and warrants further investigation. Citation Format: Clayton S. Lewis, Charles Backman, Sabahat Ahsan, Ashley Cliff, Arthi Hariharan, Jen Jen Yeh, Davendra P. S. Sohal, Vladimir Y. Bogdanov. First-in-class humanized antibody targeting alternatively spliced tissue factor augments anti-metastatic efficacy of chemotherapy in a preclinical model of pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr A085.

Retraction: Integrating mechanisms of response and resistance against the tubulin binding agent Eribulin in preclinical models of osteosarcoma.

Retraction: Integrating mechanisms of response and resistance against the tubulin binding agent Eribulin in preclinical models of osteosarcoma.

Comparative analysis of micronucleus induction and DNA damage biomarkers in TK6 and A375 cells using flow cytometry.

Previously, we introduced an alternative adherent A375 cell line for clastogenicity and aneugenicity testing using a high content imaging platform. To further characterize the performance of A375 cells, we investigated the sensitivity and specificity of A375 and TK6 cells by directly comparing micronucleus (MN) induction, cytotoxicity (relative cell counts, viability, and apoptosis), clastogenicity (γH2AX), and aneuploidy markers (pH 3, MPM-2, and polyploidy) using flow cytometric methods. We evaluated 14 compounds across different mechanisms (non-genotoxic apoptosis inducers, clastogens, and aneugens with either tubulin binding or aurora kinase inhibiting phenotypes) at 4-h and 24-h post treatment. Both aneugens and clastogens tested positive for micronucleus induction in both cell lines. Apoptosis continued to be a confounding factor for flow cytometry-based micronuclei assessment in TK6 cells as evidenced by positive responses by the three cytotoxicants. Conversely, A375 cells were not affected by apoptosis-related false positive signals and did not produce a positive response in the in vitro micronucleus assay. Benchmark dose response (BMD) analysis showed that the induction of micronuclei and biomarkers occurred at similar concentrations in both cell lines for clastogens and aneugens. By showing that A375 cells have similar sensitivity to TK6 cells but a greater specificity, these results provide additional support for A375 cells to be used as an alternative adherent cell line for in vitro genetic toxicology assessment.

Identification of potential key genes for colorectal cancer based on bioinformatics analysis.

This study aimed to explore key genes as potential biomarkers for colorectal cancer (CRC) diagnosis and prognosis in order to improve their clinical utility. To identify and screen candidate genes involved in CRC carcinogenesis and disease progression, we downloaded the microarray datasets GSE143939, GSE196006, and GSE200427 from the GEO database and applied the GEO2R tool to obtain differentially expressed genes (DEGs) between colorectal cancer tissue samples and normal tissue samples. Differentially expressed genes were analyzed using the DAVID online database for gene ontology and Kyoto encyclopedia of genes and genomes pathway enrichment analyses. Protein-protein interaction network was constructed and related module analysis was performed using STRING and Cytoscape. In total, 241 DEGs were identified, including 127 downregulated and 114 upregulated genes. DEGs enriched functions and pathways included cellular response to chemical stimulus, extracellular region, carbonate dehydratase activity, cell division, spindle, and cell division. The abundant functions and pathways of DEGs included cellular response to chemical stimulus, extracellular region, carbonate dehydratase activity, cell division, spindle, cell adhesion molecule binding, Aldosterone-regulated sodium reabsorption, and Cell cycle-related processes. Fifteen key genes were identified, and bioprocess analyses showed that these genes were mainly enriched in cell cycle, cell division, mitotic spindle, and tubulin binding processes. It was found that CDK1, CEP55, MKI67, and TOP2A may be involved in CRC cancer invasion and recurrence. The pivotal genes identified in this study contribute to our understanding of the molecular and pathogenic mechanisms of CRC carcinogenesis and progression, and provide possible biomarkers for the diagnosis and treatment of CRC.

Random Allelic Expression in Inherited Retinal Disease Genes.

Inherited retinal diseases (IRDs) are a significant contributor to visual loss in children and young adults, falling second only to diabetic retinopathy. Understanding the pathogenic mechanisms of IRDs remains paramount. Some autosomal genes exhibit random allelic expression (RAE), similar to X-chromosome inactivation. This study identifies RAE genes in IRDs. Genes in the Retinal Information Network were cross-referenced with the recent literature to identify expression profiles, RAE, or biallelic expression (BAE). Loss-of-function intolerance (LOFI) was determined by cross-referencing the existing literature. Molecular and biological pathways that are significantly enriched were evaluated using gene ontology. A total of 184 IRD-causing genes were evaluated. Of these, 31 (16.8%) genes exhibited RAE. LOFI was exhibited in 6/31 (19.4%) of the RAE genes and 18/153 (11.8%) of the BAE genes. Brain tissue exhibited BAE in 107/128 (83.6%) genes for both sexes. The molecular pathways significantly enriched among BAE genes were photoreceptor activity, tubulin binding, and nucleotide/ribonucleotide binding. The biologic pathways significantly enriched for RAE genes were equilibrioception, parallel actin filament bundle assembly, photoreceptor cell outer segment organization, and protein depalmitoylation. Allele-specific expression may be a mechanism underlying IRD phenotypic variability, with clonal populations of embryologic precursor cells exhibiting RAE. Brain tissue preferentially exhibited BAE, possibly due to selective pressures against RAE. Pathways critical for cellular and visual function were enriched in BAE, which may offer a survival benefit.

RING-type E3 ligase BnaJUL1 ubiquitinates and degrades BnaTBCC1 to regulate drought tolerance in Brassica napus L.

Drought stress poses a persistent threat to field crops and significantly limits global agricultural productivity. Plants employ ubiquitin-dependent degradation as a crucial post-translational regulatory mechanism to swiftly adapt to changing environmental conditions. JUL1 is a RING-type E3 ligase related to drought stress in Arabidopsis. In this study, we explored the function of BnaJUL1 (a homologous gene of JUL1 in Brassica napus) and discovered a novel gene BnaTBCC1 participating in drought tolerance. First, we utilised BnaJUL1-cri materials through the clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 system. Second, we confirmed that BnaJUL1 regulated drought tolerance through the drought tolerance assay and transcriptome analysis. Then, we identified a series of proteins interacting with BnaJUL1 through yeast library screening, including BnaTBCC1 (a tubulin binding cofactor C domain-containing protein); whose homologous gene TBCC1 knockdown mutants (tbcc1-1) exhibited ABA-sensitive germination in Arabidopsis, we then confirmed the involvement of BnaTBCC1 in drought tolerance in both Arabidopsis and Brassica. Finally, we established that BnaJUL1 could ubiquitinate and degrade BnaTBCC1 to regulate drought tolerance. Consequently, our study unveils BnaJUL1 as a novel regulator that ubiquitinates and degrades BnaTBCC1 to modulate drought tolerance and provided desirable germplasm for further breeding of drought tolerance in rapeseed.