Targeting the actin/tropomyosin cytoskeleton in epithelial ovarian cancer reveals multiple mechanisms of synergy with anti-microtubule agents

Myosin-1C differentially displaces tropomyosin isoforms altering their inhibition of motility

Force generation and motility by actomyosin in nonmuscle cells are spatially regulated by ∼40 tropomyosin (Tpm) isoforms. The means by which Tpms are targeted to specific cellular regions and the mechanisms that result in differential activity of myosin paralogs are unknown. We show that Tpm3.1 and Tpm1.7 inhibit Myosin-IC (Myo1C), with Tpm1.7 more effectively reducing the number of gliding filaments than Tpm3.1. Strikingly, cosedimentation and fluorescence microscopy assays revealed that Tpm3.1 is displaced from actin by Myo1C and not by myosin-II. In contrast, Tpm1.7 is only weakly displaced by Myo1C. Unlike other characterized myosins, Myo1C motility is inhibited by Tpm when the Tpm-actin filament is activated by myosin-II. These results point to a mechanism for the exclusion of myosin-I paralogs from cellular Tpm-decorated actin filaments that are activated by other myosins. Additionally, our results suggest a potential mechanism for myosin-induced Tpm sorting in cells.

The Integrated Bioinformatic Approach Reveals the Prognostic Significance of LRP1 Expression in Ovarian Cancer

A hyperactive tumour microenvironment (TME) drives unrestricted cancer cell survival, drug resistance, and metastasis in ovarian carcinoma (OC). However, therapeutic targets within the TME for OC remain elusive, and efficient methods to quantify TME activity are still limited. Herein, we employed an integrated bioinformatics approach to determine which immune-related genes (IRGs) modulate the TME and further assess their potential theragnostic (therapeutic + diagnostic) significance in OC progression. Using a robust approach, we developed a predictive risk model to retrospectively examine the clinicopathological parameters of OC patients from The Cancer Genome Atlas (TCGA) database. The validity of the prognostic model was confirmed with data from the International Cancer Genome Consortium (ICGC) cohort. Our approach identified nine IRGs, AKT2, FGF7, FOS, IL27RA, LRP1, OBP2A, PAEP, PDGFRA, and PI3, that form a prognostic model in OC progression, distinguishing patients with significantly better clinical outcomes in the low-risk group. We validated this model as an independent prognostic indicator and demonstrated enhanced prognostic significance when used alongside clinical nomograms for accurate prediction. Elevated LRP1 expression, which indicates poor prognosis in bladder cancer (BLCA), OC, low-grade gliomas (LGG), and glioblastoma (GBM), was also associated with immune infiltration in several other cancers. Significant correlations with immune checkpoint genes (ICGs) highlight the potential importance of LRP1 as a biomarker and therapeutic target. Furthermore, gene set enrichment analysis highlighted LRP1's involvement in metabolism-related pathways, supporting its prognostic and therapeutic relevance also in BLCA, OC, low-grade gliomas (LGG), GBM, kidney cancer, OC, BLCA, kidney renal clear cell carcinoma (KIRC), stomach adenocarcinoma (STAD), and stomach and oesophageal carcinoma (STES). Our study has generated a novel signature of nine IRGs within the TME across cancers, that could serve as potential prognostic predictors and provide a valuable resource to improve the prognosis of OC.

Comprehensive analysis of single cell and bulk data develops a promising prognostic signature for improving immunotherapy responses in ovarian cancer

The tumor heterogeneity is an important cause of clinical therapy failure and yields distinct prognosis in ovarian cancer (OV). Using the advantages of integrated single cell RNA sequencing (scRNA-seq) and bulk data to decode tumor heterogeneity remains largely unexplored. Four public datasets were enrolled in this study, including E-MTAB-8107, TCGA-OV, GSE63885, and GSE26193 cohorts. Random forest algorithm was employed to construct a multi-gene prognostic panel and further evaluated by receiver operator characteristic (ROC), calibration curve, and Cox regression. Subsequently, molecular characteristics were deciphered, and treatments strategies were explored to deliver precise therapy. The landscape of cell subpopulations and functional characteristics, as well as the dynamic of macrophage cells were detailly depicted at single cell level, and then screened prognostic candidate genes. Based on the expression of candidate genes, a stable and robust cell characterized gene associated prognosis signature (CCIS) was developed, which harbored excellent performance at prognosis assessment and patient stratification. The ROC and calibration curves, and Cox regression analysis elucidated CCIS could serve as serve as an independent factor for predicting prognosis. Moreover, a promising clinical tool nomogram was also constructed according to stage and CCIS. Through comprehensive investigations, patients in low-risk group were charactered by favorable prognosis, elevated genomic variations, higher immune cell infiltrations, and superior antigen presentation. For individualized treatment, patients in low-risk group were inclined to better immunotherapy responses. This study dissected tumor heterogeneity and afforded a promising prognostic signature, which was conducive to facilitating clinical outcomes for patients with OV.

The Actin Cytoskeleton as a Regulator of Proteoglycan 4

OBJECTIVE

The superficial zone (SZ) of articular cartilage is responsible for distributing shear forces for optimal cartilage loading and contributes to joint lubrication through the production of proteoglycan 4 (PRG4). PRG4 plays a critical role in joint homeostasis and is chondroprotective. Normal PRG4 production is affected by inflammation and irregular mechanical loading in post-traumatic osteoarthritis (PTOA). THe SZ chondrocyte (SZC) phenotype, including PRG4 expression, is regulated by the actin cytoskeleton in vitro. There remains a limited understanding of the regulation of PRG4 by the actin cytoskeleton in native articular chondrocytes. The filamentous (F)-actin cytoskeleton is a potential node in crosstalk between mechanical stimulation and cytokine activation and the regulation of PRG4 in SZCs, therefore developing insights in the regulation of PRG4 by actin may identify molecular targets for novel PTOA therapies.

MATERIALS AND METHODS

A comprehensive literature search on PRG4 and the regulation of the SZC phenotype by actin organization was performed.

RESULTS

PRG4 is strongly regulated by the actin cytoskeleton in isolated SZCs in vitro. Biochemical and mechanical stimuli have been characterized to regulate PRG4 and may converge upon actin cytoskeleton signaling.

CONCLUSION

Actin-based regulation of PRG4 in native SZCs is not fully understood and requires further elucidation. Understanding the regulation of PRG4 by actin in SZCs requires an in vivo context to further potential of leveraging actin arrangement to arthritic therapeutics.

Cortical tension drug screen links mitotic spindle integrity to Rho pathway

Mechanical force generation plays an essential role in many cellular functions, including mitosis. Actomyosin contractile forces mediate changes in cell shape in mitosis and are implicated in mitotic spindle integrity via cortical tension. An unbiased screen of 150 small molecules that impact actin organization and 32 anti-mitotic drugs identified two molecular targets, Rho kinase (ROCK) and tropomyosin 3.1/2 (Tpm3.1/2), whose inhibition has the greatest impact on mitotic cortical tension. The converse was found for compounds that depolymerize microtubules. Tpm3.1/2 forms a co-polymer with mitotic cortical actin filaments, and its inhibition prevents rescue of multipolar spindles induced by anti-microtubule chemotherapeutics. We examined the role of mitotic cortical tension in this rescue mechanism. Inhibition of ROCK and Tpm3.1/2 and knockdown (KD) of cortical nonmuscle myosin 2A (NM2A), all of which reduce cortical tension, inhibited rescue of multipolar mitotic spindles, further implicating cortical tension in the rescue mechanism. GEF-H1 released from microtubules by depolymerization increased cortical tension through the RhoA pathway, and its KD also inhibited rescue of multipolar mitotic spindles. We conclude that microtubule depolymerization by anti-cancer drugs induces cortical-tension-based rescue to ensure integrity of the mitotic bipolar spindle mediated via the RhoA pathway. Central to this mechanism is the dependence of NM2A on Tpm3.1/2 to produce the functional engagement of actin filaments responsible for cortical tension.

Serum Proteomic Profiles of Patients with High and Low Risk of Endometrial Cancer Recurrence

Endometrial cancer is the most common gynecological cancer worldwide. Classifying endometrial cancer into low- or high-risk groups based on the following features is recommended: tumor grade, lymphovascular space invasion, myometrial involvement, and non-endometrioid histology. Despite the recent progress in molecular profiling of endometrial cancer, a substantial group of patients are misclassified based on the current criteria. This study aimed to identify proteins that could be used as biomarkers for the stratification of endometrial cancer patients into low- or high-risk groups. The proteomic analysis of serum samples from endometrial cancer patients was performed using matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS). The data were then analyzed using chemometric algorithms to identify potential biomarkers. Nineteen precursor ions were identified as fragments of eighteen proteins which included (1) connective tissue matrix proteins, (2) cytoskeletal proteins, and (3) innate immune system molecules and stress proteins. These biomarkers could be used to stratify the high- and low-risk patients, thus enabling more precise treatment decisions.

Research Advances in the Role of the Tropomyosin Family in Cancer

Cancer is one of the most difficult diseases for human beings to overcome. Its development is closely related to a variety of factors, and its specific mechanisms have been a hot research topic in the field of scientific research. The tropomyosin family (Tpm) is a group of proteins closely related to the cytoskeleton and actin, and recent studies have shown that they play an important role in various cancers, participating in a variety of biological activities, including cell proliferation, invasion, and migration, and have been used as biomarkers for various cancers. The purpose of this review is to explore the research progress of the Tpm family in tumorigenesis development, focusing on the molecular pathways associated with them and their relevant activities involved in tumors. PubMed and Web of Science databases were searched for relevant studies on the role of Tpms in tumorigenesis and development and the activities of Tpms involved in tumors. Data from the literature suggest that the Tpm family is involved in tumor cell proliferation and growth, tumor cell invasion and migration, tumor angiogenesis, tumor cell apoptosis, and immune infiltration of the tumor microenvironment, among other correlations. It can be used as a potential biomarker for early diagnosis, follow-up, and therapeutic response of some tumors. The Tpm family is involved in cancer in a close relationship with miRNAs and LncRNAs. Tpms are involved in tumor tissue invasion and migration as a key link. On this basis, TPM is frequently used as a biomarker for various cancers. However, the specific molecular mechanism of its involvement in cancer progression has not been explained clearly, which remains an important direction for future research.

An overview on the exploring the interaction of inorganic nanoparticles with microtubules for the advancement of cancer therapeutics

Targeting microtubules (MTs), dynamic and stable proteins in cells, by different ligands have been reported to be a potential strategy to combat cancer cells. Inorganic nanoparticles (NPs) have been widely used as anticancer, antibacterial, and free radical scavenging agents, where the come in contact with biological macromolecules. The interaction between the NPs and biological macromolecules like MTs frequently occurs through different mechanisms. A prerequisite for a detailed exploration of MT structures and functions for biomedical applications like cancer therapy is to investigate profoundly the mechanisms involved in MT-NP interactions, for which the full explanation and characterization of the parameters that are responsible for the formation of a NP-protein complex are crucial. Therefore, in view of the fact that the goal of the rational NP-based future drug design and new therapies is to rely on the information of the structural details and protein-NPs binding mechanisms to manipulate the process of developing new potential drugs, a comprehensive investigation of the essence of the molecular recognition/interaction is also of considerable importance. In the present review, first, the microtubule (MT) structure and its binding sites upon interaction with MT stabilizing agents (MSAs) and MT destabilizing agents (MDAs) are introduced and rationalized. Next, MT targeting in cancer therapy and interaction of NPs with MTs are discussed. Furthermore, interaction of NPs with proteins and the manipulation of protein corona (PC), experimental techniques, and direct interaction of NPs with MTs, are discussed, and finally the challenges and future perspective of the field are introduced. We envision this review can provide useful information on the manipulation of the MT lattice for the progress of cancer nanomedicine.

PI3K/AKT Signaling Tips the Balance of Cytoskeletal Forces for Cancer Progression

The PI3K/AKT signaling pathway plays essential roles in multiple cellular processes, which include cell growth, survival, metabolism, and motility. In response to internal and external stimuli, the PI3K/AKT signaling pathway co-opts other signaling pathways, cellular components, and cytoskeletal proteins to reshape individual cells. The cytoskeletal network comprises three main components, which are namely the microfilaments, microtubules, and intermediate filaments. Collectively, they are essential for many fundamental structures and cellular processes. In cancer, aberrant activation of the PI3K/AKT signaling cascade and alteration of cytoskeletal structures have been observed to be highly prevalent, and eventually contribute to many cancer hallmarks. Due to their critical roles in tumor progression, pharmacological agents targeting PI3K/AKT, along with cytoskeletal components, have been developed for better intervention strategies against cancer. In our review, we first discuss existing evidence in-depth and then build on recent advances to propose new directions for therapeutic intervention.