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PubMed2025

Zea mays Meiotic Spindle Ultrastructure Reveals Kinetochore-Microtubule Interface and Embedded Membrane Components.

UNLABELLED: Introduction: Spindles are microtubules-based machines whose primary function is to accurately segregate chromosomes in both mitotic and meiotic cell division. The structure of spindles is critical for their function; errors in morphology or attachment to chromosomes lead to aneuploidy, potentially resulting in disease, infertility, and lethality. Electron microscopy studies have yielded fine-detail spindle ultrastructures in many plant and animal species, but no studies have investigated the spindle of Zea mays, a critical crop, and cytogenetic model system. METHODS: Here we use electron tomography (ET), reconstruction, and modeling to obtain three-dimensional, nanometer-resolution of the Z. mays meiotic spindle. Structures such as microtubules, kinetochores, vesicles, membrane channels, and nuclear envelope were modeled through a partial spindle reconstruction, and confirmed using immunostaining and live fluorescence microscopy. RESULTS: ET revealed that maize spindles contain 8-18 kinetochore microtubules (kMTs) per kinetochore, which are approximately 776 nm in diameter and 316 nm in depth. Small ∼37 nm vesicles were identified, as well as larger (∼5 µm long, 800 nm wide) membrane structures with channels that allow spindle microtubules to pass through. These membrane channels stain positively for the ER-marker protein disulfide isomerase. Imaging of prophase meiotic cells revealed a cross-hatch microtubule arrangement in the perinuclear ring on the external surface of the nuclear envelope, which also contained type II nuclear grooves with transnuclear microtubules passing from the nucleus to the cytoplasm. CONCLUSIONS: Z. mays meiotic spindles are similar to animal counterparts with a comparable number of kMTs and pre-spindle transnuclear microtubules but also plant-specific features such as Golgi-derived vesicles to assist cell plate formation, internal ER membrane channels, and a perinuclear microtubule ring that aids spindle assembly. Maize kinetochores have an electron-diffuse ball in cup morphology that is comparable in size to Drosophila kinetochores and larger than mammalian kinetochores. .

Zea mays↗

PubMed2025

The first case of GOLGA5-RET fusion-positive malignant spindle cell sarcoma of the head and neck responsive to selpercatinib.

Soft-tissue sarcoma (STS) is a rare malignancy that accounts for less than 1% of all cancers, and recent advances in molecular biology have led to its classification based on genomic information. Some RET-rearranged neoplasms have been reported to present pathological features similar to Neurotrophic Tyrosine Kinase Receptor-rearranged spindle cell neoplasms. Here, we report the first case of head and neck spindle cell sarcoma with a GOLGA5-RET fusion that demonstrated a sustained clinical response to selpercatinib, identified through targeted next-generation sequencing (NGS). The patient was a 43 year-old man with a tumor in the arytenoid region that was resected and diagnosed as a malignant spindle cell tumor. Despite initial treatment with surgical resection alone, local recurrence was confirmed, requiring salvage therapy with total laryngectomy and bilateral cervical dissection. Surgical specimen revealed a spindle tumor with a patternless pattern and collagenous stroma. Immunohistochemistry (IHC) with positivity for CD34, bcl-2 (focally), S100, and weak nuclear staining for STAT6, with absence of expression of CK AE1/3, desmin, c-kit, smooth muscle actin, myogenin, synaptophysin, and SOX10. Trk A/B/C were also negative on IHC. Following confirmation of multiple lung metastases, the patient was treated with doxorubicin monotherapy. Targeted NGS identified GOLGA5-RET rearrangement, FGF14 amplification (equivocal), CDKN2B loss, and CDKN2A loss. GOLGA5-RET rearrangements were validated through fluorescence in situ hybridization. The patient subsequently was enrolled in a phase 1/2 trial for the selective RET inhibitor selpercatinib, resulting in a sustained partial response over 5 years. Although solitary fibrous tumor (SFT) was initially considered as a differential diagnosis based on immunohistochemical findings, the lack of strong and diffuse STAT6 expression made this diagnosis unlikely. Subsequent next-generation sequencing (NGS) revealed a RET fusion, leading to the diagnosis of an RET-rearranged spindle cell neoplasm. This case highlights the importance of genomic testing for certain spindle cell sarcomas and the potential benefit of RET-specific inhibitors against RET-altered sarcomas.

Next-generation sequencing↗

PubMed2025

Ossifying Spindled and Epithelioid Tumor: A Novel Soft Tissue Tumor.

This investigation describes the clinicoradiologic, pathologic, and molecular features of a unique soft tissue tumor characterized by a peripheral shell of bone and composed of bland myoid spindle and epithelioid cells that are keratin-positive. Our study cohort consists of 6 men and 6 women, with a mean age of 32 years. The tumors arose in the extremities (n = 9) and proximal limb girdle (n = 3) and were equally distributed between deep and superficial soft tissues. Patients reported dull painless masses of several months to >10 years duration (mean: 2.9 years). Imaging demonstrated a complete or partial peripheral shell of bone that could extend centrally, and the tumor's mean size was 5.7 cm. Histologically, the tumors were composed of uniform, eosinophilic myoid spindled cells growing in sheets and intersecting fascicles, surrounded by mature lamellar and/or woven bone. Also present was an admixed component of intermediate-sized epithelioid cells with eosinophilic cytoplasm. Mitotic activity was consistently low. Immunohistochemistry showed strong multifocal staining for keratins, and 50% (5/10) showed focal staining for S100; however, all were negative for SMA, desmin, SOX10, ERG, and CD34. Genetic analysis by multiple targeted RNA sequencing panels was negative (n = 10); however, whole transcriptome sequencing (n = 8) revealed a recurrent and novel in-frame SRSF7::NFATC3 fusion in 4 tumors. Dual fluorescence in situ hybridization probes for SRSF7::NFATC3 successfully confirmed this fusion and identified a fifth case, which had not undergone whole transcriptome sequencing but was negative by a targeted RNA fusion panel. Methylation profiling (n = 8) demonstrated a shared epigenetic profile distinct from other entities. Clinical follow-up (n = 11) showed no evidence of recurrence after primary excision with a mean of 41.6 months. In summary, we describe a novel soft tissue tumor designated "ossifying spindled and epithelioid tumor" as a descriptive histologic term that also emphasizes its close radiologic mimic, ossifying fibromyxoid tumor. All cases have behaved in a benign fashion without recurrence following simple excision. Awareness of this entity is important, so that it can be distinguished from other neoplasms that have more aggressive biological potential.

Humans↗

PubMed2025

4D Microscopy and Tracking of Chromosomes and the Spindle in C. elegans Early Embryos.

Maintaining genomic integrity throughout successive cell divisions is essential for the proper development and functioning of organisms. Chromosome alignment and segregation occur on a microtubule-based spindle originating from centrosomes. The molecular and cellular mechanisms involved in accurate chromosome segregation during early embryonic divisions are highly conserved between worms and humans. Therefore, C. elegans serves as a robust model for investigating mitotic cell divisions within a metazoan system. Throughout early embryonic development, filming and tracking successive cell divisions becomes progressively more challenging as the number of cells increases and cell size decreases. To address this challenge, we describe a method for preparing live samples, performing 4D time-lapse imaging, and semi-automated tracking of chromosomes and spindle poles during early mitotic divisions in C. elegans embryos.

Caenorhabditis elegans↗

PubMed2004

Kinetochore targeting of fission yeast Mad and Bub proteins is essential for spindle checkpoint function but not for all chromosome segregation roles of Bub1p.

Several lines of evidence suggest that kinetochores are organizing centers for the spindle checkpoint response and the synthesis of a "wait anaphase" signal in cases of incomplete or improper kinetochore-microtubule attachment. Here we characterize Schizosaccharomyces pombe Bub3p and study the recruitment of spindle checkpoint components to kinetochores. We demonstrate by chromatin immunoprecipitation that they all interact with the central domain of centromeres, consistent with their role in monitoring kinetochore-microtubule interactions. Bub1p and Bub3p are dependent upon one another, but independent of the Mad proteins, for their kinetochore localization. We demonstrate a clear role for the highly conserved N-terminal domain of Bub1p in the robust targeting of Bub1p, Bub3p, and Mad3p to kinetochores and show that this is crucial for an efficient checkpoint response. Surprisingly, neither this domain nor kinetochore localization is required for other functions of Bub1p in chromosome segregation.

Chromosomes, Fungal↗

PubMed2025

Plasmodium ARK1 regulates spindle formation during atypical mitosis and forms a divergent chromosomal passenger complex.

Mitosis in Plasmodium spp., the causative agent of malaria, is fundamentally different from model eukaryotes, proceeding via a bipartite microtubule organising centre (MTOC) and lacking canonical regulators such as Polo and Bub1 kinases. During schizogony, asynchronous nuclear replication produces a multinucleate schizont, while rapid male gametogony generates an octaploid nucleus before gamete formation. Here, we identify Aurora-related kinase 1 (ARK1) as a key component of inner MTOC and spindle formation, controlling kinetochore dynamics and driving mitotic progression. Conditional ARK1 depletion disrupts spindle biogenesis, kinetochore segregation, karyokinesis and cytokinesis in both stages, and affects parasite transmission. Interactome analysis reveals ARK1 as the catalytic core of a non-canonical chromosomal passenger complex (CPC) containing two divergent inner centromere proteins (INCENPs) but lacking Survivin and Borealin. Comparative genomics indicates this CPC architecture arose early in Apicomplexa, replacing canonical centromere-targeting modules. These findings uncover a distinct mitotic machinery in Plasmodium and identify the ARK1-INCENP interface as a potential multistage target for malaria therapeutic intervention.

Aurora kinase↗

PubMed2026

Spindle Assembly Checkpoint Competency Determines Sensitivity to KIF18A Inhibition in Small-Cell Lung Cancer.

BACKGROUND: Small-cell lung cancer (SCLC) is characterized by pervasive chromosomal instability (CIN) and remains largely refractory to targeted therapies. KIF18A, a motor protein that regulates chromosome alignment during mitosis, has emerged as a selective dependency in CIN-high tumors. Whether this dependency extends to SCLC, a prototypical CIN-high cancer, has not been established, and biomarkers predicting response to KIF18A inhibition, currently in clinical trials, are lacking. METHODS: We integrated analyses of patient tumor datasets, neuroendocrine (NE) and non- NE SCLC cell lines, and functional perturbation models to define the determinants of response to KIF18A inhibition. Chromosomal instability metrics, transcriptional programs, mitotic dynamics, and spindle assembly checkpoint (SAC) function were assessed using genomic profiling, live-cell imaging, genetic perturbation, and pharmacologic inhibition. RESULTS: KIF18A expression was elevated in SCLC tumors and correlated with CIN-associated transcriptional programs, proliferative markers, and NE status; however, these features did not predict sensitivity to KIF18A inhibition. Instead, response was determined by the functional integrity of the SAC. SAC-proficient SCLC cells underwent sustained mitotic arrest followed by apoptotic cell death upon KIF18A inhibition, whereas SAC-defective cells failed to maintain checkpoint activation and survived. Mechanistically, resistant cells exhibited impaired kinetochore recruitment of core SAC components, including MAD1 and BUBR1. Importantly, transient induction of acute CIN through MPS1 inhibition partially restored sensitivity to KIF18A inhibition in resistant models. CONCLUSIONS: This study provides the first mechanistic characterization of KIF18A dependency in SCLC, identifying SAC competency as the primary determinant of response. These findings establish a biologically informed framework for patient stratification and rational combination strategies. TRANSLATIONAL RELEVANCE: Small-cell lung cancer (SCLC) is an aggressive malignancy with few effective targeted therapies and marked chromosomal instability. KIF18A has emerged as a potential therapeutic target in genomically unstable cancers, but biomarkers predicting response to KIF18A inhibition are lacking. We demonstrate that sensitivity to KIF18A inhibition in SCLC is determined not by KIF18A expression, neuroendocrine subtype, or baseline chromosomal instability, but by the functional integrity of the spindle assembly checkpoint (SAC). SCLC cells with intact SAC signaling undergo sustained mitotic arrest and apoptosis upon KIF18A inhibition, whereas SAC-defective cells bypass checkpoint activation and survive aberrant mitosis. Notably, transient induction of acute chromosomal instability through MPS1 inhibition partially restores sensitivity in resistant models. Together, these findings identify mitotic checkpoint competency as a mechanistic determinant and candidate predictive biomarker for KIF18A-targeted therapies, providing a biologically informed framework for patient stratification and rational combination strategies relevant to ongoing KIF18A inhibitor clinical trials.

Journal Article↗

PubMed2024

Inhibiting the expression of spindle appendix cooled coil protein 1 can suppress tumor cell growth and metastasis and is associated with cancer immune cells in esophageal squamous cell carcinoma.

Inhibiting the expression of spindle appendix cooled coil protein 1 (SPDL1) can slow down disease progression and is related to poor prognosis in patients with esophageal cancer. However, the specific roles and molecular mechanisms of SPDL1 in esophageal squamous cell carcinoma (ESCC) have not been explored yet. The current study aimed to investigate the expression levels of SPDL1 in ESCC via transcriptome analysis using data from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus databases. Moreover, the biological roles, molecular mechanisms, and protein networks involved in SPDL1 were identified using machine learning and bioinformatics. The cell counting kit-8 assay, EdU staining, and transwell assay were used to investigate the effects of inhibiting SPDL1 expression on ESCC cell proliferation, migration, and invasion. Finally, the correlation between the SPDL1 expression and cancer immune infiltrating cells was evaluated by analyzing data from the TCGA database. Results showed that SPDL1 was overexpressed in the ESCC tissues. The SPDL1 expression was related to age in patients with ESCC. The SPDL1 co-expressed genes included those involved in cell division, cell cycle, DNA repair and replication, cell aging, and other processes. The high-risk scores of SPDL1-related long non-coding RNAs were significantly correlated with overall survival and cancer progression in patients with ESCC (P < 0.05). Inhibiting the SPDL1 expression was effective in suppressing the proliferation, migration, and invasion of ESCC TE-1 cells (P < 0.05). The overexpression of SPDL1 was positively correlated with the levels of Th2 and T-helper cells, and was negatively correlated with the levels of plasmacytoid dendritic cells and mast cells. In conclusion, SPDL1 was overexpressed in ESCC and was associated with immune cells. Further, inhibiting the SPDL1 expression could effectively slow down cancer cell growth and migration. SPDL1 is a promising biomarker for treating patients with ESCC.

Humans↗

PubMed2026

Spindle Cell Predominant Anaplastic Pleomorphic Xanthoastrocytoma (WHO Grade 3) With Focal Piloid Features: A Rare Case Study With Comprehensive Molecular Profiling.

Pleomorphic xanthoastrocytoma (PXA) is a rare astrocytic tumor of the central nervous system. The typical form demonstrates relatively low-grade histologic features, whereas an anaplastic variant shows more aggressive behavior, including increased mitotic activity and necrotic changes. These tumors are often associated with alterations involving key growth signaling pathways and cell cycle regulatory genes, with molecular features that may resemble those seen in other high-grade astrocytic neoplasms. We describe an unusual example of an anaplastic pleomorphic xanthoastrocytoma showing focal piloid differentiation. The patient presented with acute neurologic symptoms, and imaging demonstrated a large, enhancing, well-circumscribed cerebral lesion with limited surrounding edema. Histologic evaluation revealed a highly cellular astrocytic neoplasm composed of spindle-shaped cells with marked pleomorphism, including scattered multinucleated forms, brisk mitotic activity, and necrotic areas. At the periphery, regions with elongated bipolar glial cells and occasional cytoplasmic inclusions suggestive of piloid morphology were identified. Molecular analysis demonstrated an activating alteration in the mitogen-activated protein kinase (MAPK) pathway along with additional genomic abnormalities, while mutations commonly associated with diffuse gliomas were not detected. The presence of piloid features within an otherwise anaplastic tumor is rare and may be relevant to the relatively favorable outcome observed during extended follow-up.

anaplastic↗

PubMed2025

Clinical, Morphologic, and Molecular Findings in Neurotrophic Tyrosine Receptor Kinase 3 (NTRK3) Fusion Spitz Neoplasms.

Neurotrophic tyrosine receptor kinase 3 (NTRK3) fusions are a relatively common driver of Spitz neoplasms. This subset of Spitz neoplasms may have smaller cells without the typical abundant glassy eosinophilic cytoplasm seen in most Spitz neoplasms. This can make it difficult to recognize them as belonging to the Spitz family and potentially result in misdiagnosis as melanoma. In this study, we assessed the clinical, morphologic, and genomic features of 60 NTRK3 fusion Spitz neoplasms (13 previously reported and 47 new cases) and performed a comprehensive review of the literature. We identified 5 characteristic morphologic patterns: (1) conventional Spitz nevus (SN) or Spitz tumor (ST), (2) spindle cell nevus of Reed, (3) spindle cell tumor of Reed, (4) dysplastic SN, and (5) exclusively spindle cell variant of SN/ST. The most common fusion partners were MYO5A and ETV6. DNA copy number changes were infrequent (18% of cases), with an average of 1 copy number variant per case. Among 54 cases tested for a TERT promoter mutation, all were negative. One case had a homozygous deletion of 9p21. The majority of cases were diagnosed as SN or Reed nevi (n = 37), rather than ST or Reed tumor (n = 23), and none were diagnosed as Spitz melanoma. Among the 30 patients with outcome data, none experienced recurrence following excision (mean follow-up time was 15 months). NTRK3 fusions can produce morphologic variants of Spitz neoplasms that may be difficult to recognize as belonging to the Spitz family. Familiarity with these morphologic patterns can facilitate identification of the NTRK3 fusion, optimizing classification and distinction from melanoma.

Humans↗

PubMed2026

Cumulus cells enhance oocyte genomic quality control by promoting DNA damage-induced meiotic arrest.

Cumulus cells are known to maintain oocyte arrest at prophase I through gap junction-mediated cAMP signalling, but their role after meiotic resumption remains unclear. Here, we show that cumulus cells enhance oocyte genomic quality control by sensitizing mouse oocytes to DNA damage-induced meiotic arrest. Time-lapse imaging of SiR-tubulin-labelled spindles revealed that oocytes from cumulus-oocyte complexes (COCs) matured faster than denuded oocytes (DOs). Upon mild DNA damage induced by low-dose etoposide, COC oocytes arrested at metaphase I, whereas DOs completed maturation despite similar levels of DNA lesions. This arrest required spindle assembly checkpoint (SAC) activity, as reversine rescued polar body extrusion and BubR1 and Mad2 were elevated in COCs but not DOs. Disruption of gap junctions or inhibition of mTOR signalling abolished the checkpoint response. Notably, cumulus cells did not enhance oocyte response to minor spindle perturbations. These findings reveal a previously unrecognized role of cumulus cells in mediating DNA damage-induced SAC activation, providing post-GVBD genomic surveillance beyond prophase I arrest.

Animals↗

PubMed2024

Cyclin A/Cdk1 promotes chromosome alignment and timely mitotic progression.

To ensure genomic fidelity, a series of spatially and temporally coordinated events is executed during prometaphase of mitosis, including bipolar spindle formation, chromosome attachment to spindle microtubules at kinetochores, the correction of erroneous kinetochore-microtubule (k-MT) attachments, and chromosome congression to the spindle equator. Cyclin A/Cdk1 kinase plays a key role in destabilizing k-MT attachments during prometaphase to promote correction of erroneous k-MT attachments. However, it is unknown whether Cyclin A/Cdk1 kinase regulates other events during prometaphase. Here, we investigate additional roles of Cyclin A/Cdk1 in prometaphase by using an siRNA knockdown strategy to deplete endogenous Cyclin A from human cells. We find that depleting Cyclin A significantly extends mitotic duration, specifically prometaphase, because chromosome alignment is delayed. Unaligned chromosomes display erroneous monotelic, syntelic, or lateral k-MT attachments suggesting that bioriented k-MT attachment formation is delayed in the absence of Cyclin A. Mechanistically, chromosome alignment is likely impaired because the localization of the kinetochore proteins BUB1 kinase, KNL1, and MPS1 kinase are reduced in Cyclin A-depleted cells. Moreover, we find that Cyclin A promotes BUB1 kinetochore localization independently of its role in destabilizing k-MT attachments. Thus, Cyclin A/Cdk1 facilitates chromosome alignment during prometaphase to support timely mitotic progression.

Humans↗

PubMed2023

Cyclin A/Cdk1 promotes chromosome alignment and timely mitotic progression.

To ensure genomic fidelity a series of spatially and temporally coordinated events are executed during prometaphase of mitosis, including bipolar spindle formation, chromosome attachment to spindle microtubules at kinetochores, the correction of erroneous kinetochore-microtubule (k-MT) attachments, and chromosome congression to the spindle equator. Cyclin A/Cdk1 kinase plays a key role in destabilizing k-MT attachments during prometaphase to promote correction of erroneous k-MT attachments. However, it is unknown if Cyclin A/Cdk1 kinase regulates other events during prometaphase. Here, we investigate additional roles of Cyclin A/Cdk1 in prometaphase by using an siRNA knockdown strategy to deplete endogenous Cyclin A from human cells. We find that depleting Cyclin A significantly extends mitotic duration, specifically prometaphase, because chromosome alignment is delayed. Unaligned chromosomes display erroneous monotelic, syntelic, or lateral k-MT attachments suggesting that bioriented k-MT attachment formation is delayed in the absence of Cyclin A. Mechanistically, chromosome alignment is likely impaired because the localization of the kinetochore proteins BUB1 kinase, KNL1, and MPS1 kinase are reduced in Cyclin A-depleted cells. Moreover, we find that Cyclin A promotes BUB1 kinetochore localization independently of its role in destabilizing k-MT attachments. Thus, Cyclin A/Cdk1 facilitates chromosome alignment during prometaphase to support timely mitotic progression.

Preprint↗

PubMed2025

Overexpression of GFP Fusions of Regulators of the SAC from Arabidopsis thaliana.

Cell division is a fundamental biological process, essential for sustaining life on Earth. Accurate replication followed by uniform segregation of the genome is required to ensure cell division is sustainable and reduces the likelihood of aneuploidy. The cell cycle has various checkpoints to safeguard proper replication, for example, the spindle assembly checkpoint (SAC) which ensures that all chromosomes are correctly aligned and attached to the spindle, before the transition to anaphase. The precise function of the SAC and SAC components in plants is so far unclear. First, the high level of polyploidy in plants raises concerns about the efficacy of the SAC. Second, many plant SAC components are implicated in other cellular processes, such as MAD1, which has been implicated in the reproductive transition of Arabidopsis thaliana. Overexpression of GFP fusions of core SAC components provides a key route to establish the functions of the different SAC components in plants. Here we describe two methods for agrobacterium-mediated transformation of plants.

Arabidopsis↗

PubMed2005

Inactivation of the pre-mRNA cleavage and polyadenylation factor Pfs2 in fission yeast causes lethal cell cycle defects.

Faithful chromosome segregation is fundamentally important for the maintenance of genome integrity and ploidy. By isolating conditional mutants defective in chromosome segregation in the fission yeast Schizosaccharomyces pombe, we identified a role for the essential gene pfs2 in chromosome dynamics. In the absence of functional Pfs2, chromosomal attachment to the mitotic spindle was defective, with consequent chromosome missegregation. Under these circumstances, multiple intracellular foci of spindle checkpoint proteins Bub1 and Mad2 were seen, and deletion of bub1 exacerbated the mitotic defects and the loss of cell viability that resulted from the loss of pfs2 function. Progression from G1 into S phase following release from nitrogen starvation also required pfs2+ function. The product of the orthologous Saccharomyces cerevisiae gene PFS2 is a component of a multiprotein complex required for 3'-end cleavage and polyadenylation of pre-mRNAs and, in keeping with the conservation of this essential function, an S. pombe pfs2 mutant was defective in mRNA 3'-end processing. Mutations in pfs2 were suppressed by overexpression of the putative mRNA 3'-end cleavage factor Cft1. These data suggest unexpected links between mRNA 3'-end processing and chromosome replication and segregation.

Carrier Proteins↗

PubMed2026

Natural Product Target Identification of Wheldone, a Fungal Metabolite, as a KIF11 Inhibitor in Ovarian Cancer Using the DiffPOP (Differential Protein Precipitation) Method.

Wheldone, a fungal metabolite, was identified as a cytotoxic compound in high-grade serous ovarian cancer (HGSOC). Wheldone induced caspase 3/7-dependent apoptosis and reduced migration, invasion, and spheroid growth. Wheldone stimulated apoptosis in chemoresistant HGSOC models. Wheldone treatment caused significant downregulation of HNRNPD, a DNA repair protein, and increased DNA damage that could be blocked by N-acetyl-L-cysteine. In vivo, wheldone displayed minimal toxicity but was rapidly cleared from circulation, despite in vitro metabolic stability. Wheldone treatment in vivo did not demonstrate significant reduction in tumor burden. Therefore, in order to overcome these liabilities, it was necessary to find the protein target of wheldone so that modifications can be made to improve the drug-like characteristics of the compound. Using the drug-target interaction proteomics method, differential precipitation of proteins, wheldone was found to act as an inhibitor of Kinesin superfamily protein 11 (KIF11), a motor protein essential for mitotic spindle formation. An ATPase biochemical cell-free assay confirmed direct binding and functional inhibition of KIF11. Wheldone resulted in G2/M arrest and downstream regulation of mitotic proteins such as TPX2, AURKA, and phospho-histone H3. Proteomics after treatment of wheldone in four different HGSOC cancer cell lines all supported changes consistent with mitotic spindle assembly disruption. Further, KIF11 was one of only 13 proteins upregulated in all 4 cell lines treated. Overall, wheldone was found to be a fungal metabolite that inhibits KIF11 in chemoresistant ovarian cancer, with future studies needed to improve its pharmacokinetics and delivery.

Female↗

PubMed2025

Uterine Sarcomas With Recurrent KDM2B Gene Fusions: Three Cases of a Possible Novel Subtype of High-Grade Endometrial Stromal Sarcoma.

The advent of widespread genomic testing of uterine mesenchymal tumors has led to novel insights into the biology of these diverse tumors, and many genomically defined entities have been described in recent years. During a larger study of endometrial stromal sarcomas and unclassified uterine sarcomas, we identified 3 tumors harboring KDM2B gene fusions. Patients were 32, 61, and 67 years old, and all initially underwent incomplete sampling via laparoscopic myomectomy (n = 1), laparoscopic biopsy (n = 1), or hysteroscopic myomectomy (n = 1). One patient's tumor was densely adherent to the pelvic sidewall; she was treated with chemotherapy and died of widely metastatic disease at 29 weeks. Another underwent a subsequent recent hysterectomy with the tumor confined to the uterus and minimal follow-up to date. The final patient refused further treatment and was alive at 28 weeks, although the status of the disease progression was unknown. On microscopic examination, 2 tumors showed infiltrative borders, whereas interface with the myometrium was not present in the third. The tumors were variably cellular with alternating hypercellular and hypocellular zones in a myxoid to loosely collagenous stroma. The hypercellular areas contained round to ovoid cells in diffuse (n = 3) and sex cord-like arrangements, including cords (n = 3), nests (n = 2), and tubules (n = 1); 2 also contained occasional spindled cells arranged in vague fascicles. These cells showed moderate atypia with open chromatin, numerous mitoses (8, 24, and 25 per 10 high-power fields), and frequent apoptosis. The hypocellular areas contained sparse, ovoid-to-spindled cells with minimal atypia. All tumors were diffusely positive for cyclin D1, whereas BCL6 corepressor was diffusely positive in 1 and negative in 2; desmin and caldesmon were negative in all 3 neoplasms. All harbored KDM2B gene fusions; partner genes included EPC1, EP400, and CITED1. MDM2 amplification was also noted in 2. Clustering analysis based on RNA expression profiling revealed tight clustering of all 3 tumors within the broad group of high-grade endometrial stromal sarcomas. Based on the overall clinicopathologic and genomic features, we suggest that these tumors may represent a novel subtype of uterine sarcoma and may be best classified as high-grade endometrial stromal sarcoma, although additional confirmatory studies are needed.

Humans↗

PubMed2026

Loss of Methylthioadenosine Phosphorylase (MTAP) Expression: A Potentially Useful Tool for Distinguishing Sarcomatoid Urothelial Carcinoma From Inflammatory Myofibroblastic Tumor.

Inflammatory myofibroblastic tumor (IMT) and sarcomatoid urothelial carcinoma (SarUC) can have striking histologic overlap but have significantly different prognoses and clinical management paradigms. Loss of methylthioadenosine phosphorylase (MTAP) protein expression by immunohistochemistry (IHC) serves as a useful surrogate for homozygous 9p21 deletion, a recurrent genomic alteration in urothelial carcinoma (UC). We analyzed MTAP expression by IHC in 65 SarUCs and 27 urinary tract IMTs to evaluate its utility in navigating this challenging differential diagnosis. Overall, MTAP loss was significantly more frequent in SarUC (55%) compared with IMT (4%) (P < .0001). Among 46 biphasic SarUCs with independently evaluable epithelial and mesenchymal components, divergent expression patterns were frequent. The most common pattern was retention of MTAP staining in both epithelial and mesenchymal components (19/46; 41% of cases), followed by selective retention of MTAP in the epithelial component and loss in the mesenchymal component (16/46; 35% of cases). MTAP loss was observed in both the epithelial and mesenchymal components in 11 out of 46 (24%) SarUC cases. None of the 46 biphasic SarUC cases showed selective MTAP loss in the epithelial component but retention in the mesenchymal component. MTAP IHC was also particularly valuable in assessing clonal relationships in 2 challenging biphasic cases in which the differential diagnosis included a collision between a noninvasive low-grade papillary UC and an IMT versus a subtle IMT-like SarUC arising in association with an overlying noninvasive low-grade papillary UC. Next-generation sequencing on a subset of cases (n = 11) was useful for confirming 9p deletion in cases with MTAP loss by IHC, and for demonstrating molecular hallmarks of urothelial neoplasia thereby providing additional diagnostic support for morphologically challenging SarUC cases with IMT-like morphology. Therefore, MTAP IHC can be useful in evaluating spindle cell lesions of the urinary tract, as loss is significantly more common in SarUC than in IMT, and enriched in the mesenchymal component of biphasic SarUC. However, MTAP loss can be seen in both entities, and the diagnosis of IMT-like spindle cell tumors in the urinary tract requires careful integration of morphologic, immunohistochemical, and molecular data.

Humans↗