Epithelial-mesenchymal transition (EMT) is a reversible plethora of molecular events where epithelial cells gain the phenotype of mesenchymal cells to invade the surrounding tissues. EMT is a physiological event during embryogenesis (type I) but also happens during fibrosis (type II) and cancer metastasis (type III). It is a multifaceted phenomenon governed by the activation of genes associated with cell migration, extracellular matrix degradation, DNA repair, and angiogenesis. The cancer cells employ EMT to acquire the ability to migrate, resist therapeutic agents and escape immunity. One of the key biomarkers of EMT is vimentin, a type III intermediate filament that is normally expressed in mesenchymal cells but is upregulated during cancer metastasis. This review highlights the pivotal role of vimentin in the key events during EMT and explains its role as a downstream as well as an upstream regulator in this highly complex process. This review also highlights the areas that require further research in exploring the role of vimentin in EMT. As a cytoskeletal protein, vimentin filaments support mechanical integrity of the migratory machinery, generation of directional force, focal adhesion modulation and extracellular attachment. As a viscoelastic scaffold, it gives stress-bearing ability and flexible support to the cell and its organelles. However, during EMT it modulates genes for EMT inducers such as Snail, Slug, Twist and ZEB1/2, as well as the key epigenetic factors. In addition, it suppresses cellular differentiation and upregulates their pluripotent potential by inducing genes associated with self-renewability, thus increasing the stemness of cancer stem cells, facilitating the tumour spread and making them more resistant to treatments. Several missense and frameshift mutations reported in vimentin in human cancers may also contribute towards the metastatic spread. Therefore, we propose that vimentin should be a therapeutic target using molecular technologies that will curb cancer growth and spread with reduced mortality and morbidity.

In advanced metastatic cancers with reduced patient survival and poor prognosis, expression of vimentin, a type III intermediate filament protein is frequently observed. Vimentin appears to suppress epithelial characteristics and augments cell migration but the molecular basis for these changes is not well understood. Here, we have ectopically expressed vimentin in MCF-7 and investigated its genomic and functional implications. Vimentin changed the cell shape by decreasing major axis, major axis angle and increased cell migration, without affecting proliferation. Vimentin downregulated major keratin genes KRT8, KRT18 and KRT19. Transcriptome-coupled GO and KEGG analyses revealed that vimentin-affected genes were linked to either cell–cell/cell-ECM or cell cycle/proliferation specific pathways. Using shRNA mediated knockdown of vimentin in two cell types; MCF-7FV (ectopically expressing) and MDA-MB-231 (endogenously expressing), we identified a vimentin-specific signature consisting of 13 protein encoding genes (CDH5, AXL, PTPRM, TGFBI, CDH10, NES, E2F1, FOXM1, CDC45, FSD1, BCL2, KIF26A and WISP2) and two long non-coding RNAs, LINC00052 and C15ORF9-AS1. CDH5, an endothelial cadherin, which mediates cell–cell junctions, was the most downregulated protein encoding gene. Interestingly, downregulation of CDH5 by shRNA significantly increased cell migration confirming our RNA-Seq data. Furthermore, presence of vimentin altered the lamin expression in MCF-7. Collectively, we demonstrate, for the first time, that vimentin in breast cancer cells could change nuclear architecture by affecting lamin expression, which downregulates genes maintaining cell–cell junctions resulting in increased cell migration.

Vimentin, a type III intermediate filament protein, is found in most cells along with microfilaments and microtubules. It has been shown that the head domain folds back to associate with the rod domain and this association is essential for filament assembly. The N-terminally tagged vimentin has been widely used to label the cytoskeleton in live cell imaging. Although there is previous evidence that EGFP tagged vimentin fails to form filaments but is able to integrate into a pre-existing network, no study has systematically investigated or established a molecular basis for this observation. To determine whether a tag would affect de novo filament assembly, we used vimentin fused at the N-terminus with two different sized tags, AcGFP (239 residues, 27 kDa) and 3 × FLAG (22 residues; 2.4 kDa) to assemble into filaments in two vimentin-deficient epithelial cells, MCF-7 and A431. We showed that regardless of tag size, N-terminally tagged vimentin aggregated into globules with a significant proportion co-aligning with β-catenin at cell–cell junctions. However, the tagged vimentin aggregates could form filaments upon adding untagged vimentin at a ratio of 1:1 or when introduced into cells containing pre-existing filaments. The resultant filament network containing a mixture of tagged and untagged vimentin was less stable compared to that formed by only untagged vimentin. The data suggest that placing a tag at the N-terminus may create steric hinderance in case of a large tag (AcGFP) or electrostatic repulsion in case of highly charged tag (3 × FLAG) perhaps inducing a conformational change, which deleteriously affects the association between head and rod domains. Taken together our results shows that a free N-terminus is essential for filament assembly as N-terminally tagged vimentin is not only incapable of forming filaments, but it also destabilises when integrated into a pre-existing network.

Histatin peptides are a family of small histidine-rich cationic polypeptides produced by two genes, HTN1 and HTN3. They are found in salivary secretions from the parotid, sublingual, and submandibular salivary glands. These peptides undergo proteolytic cleavages to produce different histatin fragments which play multiple roles including wound healing, maintenance of enamel, and regulation of balance in the oral microbiome. In this review, we explored the expression, structural characteristics, and metal-ion-binding capacities of these peptides and how their functions are modulated by their structure. We also provide here an insight into the potential use of histatins as biomarkers and therapeutic peptides in the management of oral and non-oral diseases including cancer. Potential gaps in the current understanding of histatins that warrant further research have also been highlighted.

Vimentin is a type III intermediate filament (IF) protein that is induced in a large number of solid tumours. A single cysteine at position 328 in vimentin plays a crucial role in assembly, organisation, and stability of IFs. However, its exact function during epithelial–mesenchymal transition (EMT) and cancer progression has not been investigated. To investigate this, we have transduced wildtype (WT) and C328S vimentin separately in MCF-7 cells that lack endogenous vimentin. The expression of C328-VIM impacted vimentin–actin interactions and induced EMT-like features that include enhanced cell proliferation, migration, and invasion accompanied by reduced cell adhesion when compared to the wildtype cells. Functional transcriptomic studies confirmed the upregulation of EMT and mesenchymal markers, downregulation of epithelial markers, as well as acquisition of signatures associated with cancer stemness (CD56, POU5F1, PROCR, and CD49f), thus transforming MCF-7 cells from oestrogen-positive to triple-reduced (ESR1, PGR, and HER2) status. We also observed a stark increase in the expression of long non-coding RNA, XIST, in MCF-7 cells expressing C328-VIM. Targeting the mutant vimentin or XIST by RNA interference partially reversed the phenotypes in C328-VIM-expressing MCF-7 cells. Furthermore, the introduction of C328-VIM cells into nude mice promoted tumour growth by increasing cancer stemness in an oestrogen-independent manner. Altogether, our studies provide insight into how cysteine 328 in vimentin dictates mechano-transduction signals to remodel actin cytoskeleton and protect against EMT and cancer growth via modulating lncRNA XIST. Therefore, targeting vimentin and/or XIST via RNA interference should be a promising therapeutic strategy for breast cancer treatment.

Cancer stem cells (CSCs) are a small population of cancer cells that endow unique traits of self-renewal, differentiation, tumorigenicity, quiescence and therapeutic resistance, ultimately leading to cancer relapse and poor prognosis. Conventional chemo- and radiotherapies effectively destroy rapidly dividing cancer cells; however, CSCs are largely refractory to these treatments due to special characteristics that include metabolic plasticity, low reactive oxygen species (ROS) levels, apoptosis inhibition and modified DNA repair systems, effectively hijacking the tumour microenvironment and evading host immune surveillance. This review summarises the potential CSC diagnostic methods that can be used in routine clinical investigation for tailoring personalised treatment plans both pre- and post-surgery. In this way, a CSC gene signature, reactivity and load can be estimated and, by using artificial intelligence and machine learning algorithms in a personalised therapeutic regimen, the most effective treatment response can be predicted. Furthermore, we propose incorporation of CSC-targeted therapies in conjugation with conventional chemo- and radiotherapies to eradicate CSCs, thereby eliminating the risk of relapse and therapy failure in cancer patients. This review also describes multiple potential molecular targets that may be used to target CSCs and emphasises the need for further evaluation, in order that they may be applied clinically.