Rho GTPases: Regulation and roles in cancer cell biology

Targeting small GTPases and their downstream pathways with intracellular macromolecule binders to define alternative therapeutic strategies in cancer

The RAS superfamily of small GTPases regulates major physiological cellular processes. Mutation or deregulation of these small GTPases, their regulators and/or their effectors are associated with many diseases including cancer. Hence, targeting these classes of proteins is an important therapeutic strategy in cancer. This has been recently achieved with the approval of the first KRASG12C covalent inhibitors for the clinic. However, many other mutants and small GTPases are still considered as 'undruggable' with small molecule inhibitors because of a lack of well-defined pocket(s) at their surface. Therefore, alternative therapeutic strategies have been developed to target these proteins. In this review, we discuss the use of intracellular antibodies and derivatives - reagents that bind their antigen inside the cells - for the discovery of novel inhibitory mechanisms, targetable features and therapeutic strategies to inhibit small GTPases and their downstream pathways. These reagents are also versatile tools used to better understand the biological mechanisms regulated by small GTPases and to accelerate the drug discovery process.

Chronic arsenic increases cell migration in BEAS-2B cells by increasing cell speed, cell persistence, and cell protrusion length

There is a strong association between arsenic exposure and lung cancer development, however, the mechanism by which arsenic exposure leads to carcinogenesis is not clear. In our previous study, we observed that when BEAS-2B cells are chronically exposed to arsenic, there is an increase in secreted TGFα, as well as an increase in EGFR expression and activity. Further, these changes were broadly accompanied with an increase in cell migration. The overarching goal of this study was to acquire finer resolution of the arsenic-dependent changes in cell migration, as well as to understand the role of increased EGFR expression and activity levels in the underlying mechanisms of cell migration. To do this, we used a combination of biochemical and single cell assays, and observed chronic arsenic treatment enhancing cell migration by increasing cell speed, cell persistence and cell protrusion length. All three parameters were further increased by the addition of TGFα, indicating EGFR activity is sufficient to enhance those aspects of cell migration. In contrast, EGFR activity was necessary for the increase in cell speed, as it was reversed with an EGFR inhibitor, AG1478, but was not necessary to enhance persistence and protrusion length. From these data, we were able to isolate both EGFR-dependent and -independent features of cell migration that were enhanced by chronic arsenic exposure.

ARHGAP4-SEPT2-SEPT9 complex enables both up- and down-modulation of integrin-mediated focal adhesions, cell migration, and invasion

The Rho family of GTPases are inactivated in a cell context–dependent manner by Rho-GTPase-activating proteins (Rho-GAPs), but their signaling mechanisms are poorly understood. Here we demonstrate that ARHGAP4, one of the Rho-GAPs, forms a complex with SEPT2 and SEPT9 via its Rho-GAP domain and SH3 domain to enable both up- and down-modulation of integrin-mediated focal adhesions (FAs). We show that silencing ARHGAP4 and overexpressing its two mutually independent upstream regulators, SEPT2 and SEPT9, all induce reorganization of FAs to newly express Integrin Beta 1 and also enhance both cell migration and invasion. Interestingly, even if these cell migration/invasion–associated phenotypic changes are induced upon perturbations to the complex, it does not necessarily cause enhanced clustering of FAs. Instead, its extent depends on whether the microenvironment contains ligands suitable for the up-regulated Integrin Beta 1. These results provide novel insights into cell migration, invasion, and microenvironment-dependent phenotypic changes regulated by the newly identified complex.

High TSPAN8 expression in epithelial cancer cell-derived small extracellular vesicles promote confined diffusion and pronounced uptake

Small extracellular vesicles (sEVs) play a key role in intercellular communication. Cargo molecules carried by sEVs may affect the phenotype and function of recipient cells. Epithelial cancer cell-derived sEVs, particularly those enriched in CD151 or tetraspanin8 (TSPAN8) and associated integrins, promote tumour progression. The mechanism of binding and modulation of sEVs to recipient cells remains elusive. Here, we used genetically engineered breast cancer cells to derive TSPAN8-enriched sEVs and evaluated the impact of TSPAN8 on target cell membrane's diffusion and transport properties. The single-particle tracking technique showed that TSPAN8 significantly promoted sEV binding via confined diffusion. Functional assays indicated that the transgenic TSPAN8-sEV cargo increased cancer cell motility and epithelial-mesenchymal transition (EMT). In vivo, transgenic TSPAN8-sEV promoted uptake of sEVs in the liver, lung, and spleen. We concluded that TSPAN8 encourages the sEV-target cell interaction via forced confined diffusion and significantly increases cell motility. Therefore, TSPAN8-sEV may serve as an important direct or indirect therapeutic target.

The role of GTPase-activating protein ARHGAP26 in human cancers

Rho GTPases are molecular switches that play an important role in regulating the behavior of a variety of tumor cells. RhoA GTPase-activating protein 26 (ARHGAP26) is a GTPase-activating protein and inhibits the activity of Rho GTPases by promoting the hydrolytic ability of Rho GTPases. It also affects tumorigenesis and progression of various tumors through several methods, including formation of abnormal fusion genes and circular RNA. This review summarizes the biological functions and molecular mechanisms of ARHGAP26 in different tumors, proposes the potential clinical value of ARHGAP26 in cancer treatment, and discusses current issues that need to be addressed.

RHO GTPase-Related Long Noncoding RNAs in Human Cancers

RHO GTPases are critical signal transducers that regulate cell adhesion, polarity, and migration through multiple signaling pathways. While all these cellular processes are crucial for the maintenance of normal cell homeostasis, disturbances in RHO GTPase-associated signaling pathways contribute to different human diseases, including many malignancies. Several members of the RHO GTPase family are frequently upregulated in human tumors. Abnormal gene regulation confirms the pivotal role of lncRNAs as critical gene regulators, and thus, they could potentially act as oncogenes or tumor suppressors. lncRNAs most likely act as sponges for miRNAs, which are known to be dysregulated in various cancers. In this regard, the significant role of miRNAs targeting RHO GTPases supports the view that the aberrant expression of lncRNAs may reciprocally change the intensity of RHO GTPase-associated signaling pathways. In this review article, we summarize recent advances in lncRNA research, with a specific focus on their sponge effects on RHO GTPase-targeting miRNAs to crucially mediate gene expression in different cancer cell types and tissues. We will focus in particular on five members of the RHO GTPase family, including RHOA, RHOB, RHOC, RAC1, and CDC42, to illustrate the role of lncRNAs in cancer progression. A deeper understanding of the widespread dysregulation of lncRNAs is of fundamental importance for confirmation of their contribution to RHO GTPase-dependent carcinogenesis.

Role of RhoC in cancer cell migration

Migration is one of the five major behaviors of cells. Although RhoC-a classic member of the Rho gene family-was first identified in 1985, functional RhoC data have only been widely reported in recent years. Cell migration involves highly complex signaling mechanisms, in which RhoC plays an essential role. Cell migration regulated by RhoC-of which the most well-known function is its role in cancer metastasis-has been widely reported in breast, gastric, colon, bladder, prostate, lung, pancreatic, liver, and other cancers. Our review describes the role of RhoC in various types of cell migration. The classic two-dimensional cell migration cycle constitutes cell polarization, adhesion regulation, cell contraction and tail retraction, most of which are modulated by RhoC. In the three-dimensional cell migration model, amoeboid migration is the most classic and well-studied model. Here, RhoC modulates the formation of membrane vesicles by regulating myosin II, thereby affecting the rate and persistence of amoeba-like migration. To the best of our knowledge, this review is the first to describe the role of RhoC in all cell migration processes. We believe that understanding the detail of RhoC-regulated migration processes will help us better comprehend the mechanism of cancer metastasis. This will contribute to the study of anti-metastatic treatment approaches, aiding in the identification of new intervention targets for therapeutic or genetic transformational purposes.

MICAL2 Contributes to Gastric Cancer Cell Proliferation by Promoting YAP Dephosphorylation and Nuclear Translocation

Dynamic cytoskeletal rearrangements underlie the changes that occur during cell division in proliferating cells. MICAL2 has been reported to possess reactive oxygen species- (ROS-) generating properties and act as an important regulator of cytoskeletal dynamics. However, whether it plays a role in gastric cancer cell proliferation is not known. In the present study, we found that MICAL2 was highly expressed in gastric cancer tissues, and this high expression level was associated with carcinogenesis and poor overall survival in gastric cancer patients. The knockdown of MICAL2 led to cell cycle arrest in the S phase and attenuated cell proliferation. Concomitant with S-phase arrest, a decrease in CDK6 and cyclin D protein levels was observed. Furthermore, MICAL2 knockdown attenuated intracellular ROS generation, while MICAL2 overexpression led to a decrease in the p-YAP/YAP ratio and promoted YAP nuclear localization and cell proliferation, effects that were reversed by pretreatment with the ROS scavenger N-acetyl-L-cysteine (NAC) and SOD-mimetic drug tempol. We further found that MICAL2 induced Cdc42 activation, and activated Cdc42 mediated the effect of MICAL2 on YAP dephosphorylation and nuclear translocation. Collectively, our results showed that MICAL2 has a promotive effect on gastric cancer cell proliferation through ROS generation and Cdc42 activation, both of which independently contribute to YAP dephosphorylation and its nuclear translocation.

The Identification of Alternative Polyadenylation in Stomach Adenocarcinomas Using the Genotype-Tissue Expression Project and the Cancer Genome Atlas- Stomach Adenocarcinoma Profiles

Objective

Alternative polyadenylation (APA) is a common mechanism that is present in most human genes and determines the length of the messenger ribonucleic acid (mRNA) three prime untranslated region (3ʹ-UTR), which can give rise to changes in mRNA stability and localization. However, little is known about the specific changes related to APA in stomach adenocarcinomas (STADs).

Methods

We integrated RNA sequencing data from The Cancer Genome Atlas and Genotype-Tissue Expression project to comprehensively analyze APA events in 289 cases of STAD.

Results

Our results showed that APA events were widespread in patients with STAD and were rich in genes related to known STAD pathways. The APA events result in the loss of tumor-suppressing micro-ribonucleic acid (miRNA) binding sites and increased heterogeneity in the length of the 3ʹ-UTR altered genes. Survival analysis revealed that specific subsets of 3ʹ-UTR-altered genes independently characterized a poor prognostic cohort among patients with STAD, thereby indicating the potential of APA as a new prognostic biomarker.

Conclusion

Our single-cancer analysis showed that by losing miRNA regulation, APA can become a driving factor for regulating the expression of oncogenic genes in STAD and promote its development. Our research revealed that APA events regulated STAD genes that were functionally related, thereby providing a new approach for gaining a better understanding of the progress of STADs and a means for identifying new drug targets as avenues of treatment.

N6-Isopentenyladenosine Hinders the Vasculogenic Mimicry in Human Glioblastoma Cells through Src-120 Catenin Pathway Modulation and RhoA Activity Inhibition

BACKGROUND

Vasculogenic mimicry (VM) is a functional microcirculation pattern formed by aggressive tumor cells. Thus far, no effective drugs have been developed to target VM. Glioblastoma (GBM) is the most malignant form of brain cancer and is a highly vascularized tumor. Vasculogenic mimicry represents a means whereby GBM can escape anti-angiogenic therapies.

METHODS

Here, using an in vitro tube formation assay on Matrigel, we evaluated the ability of N6-isopentenyladenosine (iPA) to interfere with vasculogenic mimicry (VM). RhoA activity was assessed using a pull-down assay, while the modulation of the adherens junctions proteins was analyzed by Western blot analysis.

RESULTS

We found that iPA at sublethal doses inhibited the formation of capillary-like structures suppressing cell migration and invasion of U87MG, U343MG, and U251MG cells, of patient-derived human GBM cells and GBM stem cells. iPA reduces the vascular endothelial cadherin (VE-cadherin) expression levels in a dose-dependent manner, impairs the vasculogenic mimicry network by modulation of the Src/p120-catenin pathway and inhibition of RhoA-GTPase activity.

CONCLUSIONS

Taken together, our results revealed iPA as a promising novel anti-VM drug in GBM clinical therapeutics.

RhoGTPase Signalling in Cancer Progression and Dissemination

Rho GTPases are a family of small G proteins that regulate a wide array of cellular processes related to their key roles controlling the cytoskeleton. On the other hand, cancer is a multi-step disease caused by the accumulation of genetic mutations and epigenetic alterations, from the initial stages of cancer development when cells in normal tissues undergo transformation, to the acquisition of invasive and metastatic traits, responsible for a large number of cancer related deaths. In this review, we discuss the role of Rho GTPase signalling in cancer in every step of disease progression. Rho GTPases contribute to tumour initiation and progression, by regulating proliferation and apoptosis, but also metabolism, senescence and cell stemness. Rho GTPases play a major role in cell migration, and in the metastatic process. They are also involved in interactions with the tumour microenvironment and regulate inflammation, contributing to cancer progression. After years of intensive research, we highlight the importance of relevant models in the Rho GTPase field, and we reflect on the therapeutic opportunities arising for cancer patients.

Mechanism of interaction between autophagy and apoptosis in cancer

The mechanisms of two programmed cell death pathways, autophagy, and apoptosis, are extensively focused areas of research in the context of cancer. Both the catabolic pathways play a significant role in maintaining cellular as well as organismal homeostasis. Autophagy facilitates this by degradation and elimination of misfolded proteins and damaged organelles, while apoptosis induces canonical cell death in response to various stimuli. Ideally, both autophagy and apoptosis have a role in tumor suppression, as autophagy helps in eliminating the tumor cells, and apoptosis prevents their survival. However, as cancer proceeds, autophagy exhibits a dual role by enhancing cancer cell survival in response to stress conditions like hypoxia, thereby promoting chemoresistance to the tumor cells. Thus, any inadequacy in either of their levels can lead to tumor progression. A complex array of biomarkers is involved in maintaining coordination between the two by acting as either positive or negative regulators of one or both of these pathways of cell death. The resulting crosstalk between the two and its role in influencing the survival or death of malignant cells makes it quintessential, among other challenges facing chemotherapeutic treatment of cancer. In view of this, the present review aims to highlight some of the factors involved in maintaining their diaphony and stresses the importance of inhibition of cytoprotective autophagy and deletion of the intermediate pathways involved to facilitate tumor cell death. This will pave the way for future prospects in designing drug combinations facilitating the synergistic effect of autophagy and apoptosis in achieving cancer cell death.

CdGAP promotes prostate cancer metastasis by regulating epithelial-to-mesenchymal transition, cell cycle progression, and apoptosis

High mortality of prostate cancer patients is primarily due to metastasis. Understanding the mechanisms controlling metastatic processes remains essential to develop novel therapies designed to prevent the progression from localized disease to metastasis. CdGAP plays important roles in the control of cell adhesion, migration, and proliferation, which are central to cancer progression. Here we show that elevated CdGAP expression is associated with early biochemical recurrence and bone metastasis in prostate cancer patients. Knockdown of CdGAP in metastatic castration-resistant prostate cancer (CRPC) PC-3 and 22Rv1 cells reduces cell motility, invasion, and proliferation while inducing apoptosis in CdGAP-depleted PC-3 cells. Conversely, overexpression of CdGAP in DU-145, 22Rv1, and LNCaP cells increases cell migration and invasion. Using global gene expression approaches, we found that CdGAP regulates the expression of genes involved in epithelial-to-mesenchymal transition, apoptosis and cell cycle progression. Subcutaneous injection of CdGAP-depleted PC-3 cells into mice shows a delayed tumor initiation and attenuated tumor growth. Orthotopic injection of CdGAP-depleted PC-3 cells reduces distant metastasic burden. Collectively, these findings support a pro-oncogenic role of CdGAP in prostate tumorigenesis and unveil CdGAP as a potential biomarker and target for prostate cancer treatments.

Mehra et al. investigate the role of CdGAP in early biochemical recurrence and bone metastasis in prostate cancer. The authors find that knocking down CdGAP leads to reduced cell motility, invasion and proliferation in PC-3 and 22Rv1 cells while orthotopic injection of CdGAP-depleted PC-3 cells reduces distant metastatic burden.

Structural insights into the small GTPase specificity of the DOCK guanine nucleotide exchange factors

The dedicator of cytokinesis (DOCK) family of guanine nucleotide exchange factors (GEFs) regulates cytoskeletal dynamics by activating the GTPases Rac and/or Cdc42. Eleven human DOCK proteins play various important roles in developmental processes and the immune system. Of these, DOCK1-5 proteins bind to engulfment and cell motility (ELMO) proteins to perform their physiological functions. Recent structural studies have greatly enhanced our understanding of the complex and diverse mechanisms of DOCK GEF activity and GTPase recognition and its regulation by ELMO. This review is focused on gaining structural insights into the substrate specificity of the DOCK GEFs, and discuss how Rac and Cdc42 are specifically recognized by the catalytic DHR-2 and surrounding domains of DOCK or binding partners.

Dynamic interplay of two molecular switches enabled by the MEK1/2-ERK1/2 and IL-6-STAT3 signaling axes controls epithelial cell migration in response to growth factors

Cell migration is an essential physiological process, and aberrant migration of epithelial cells underlies many pathological conditions. However, the molecular mechanisms governing cell migration are not fully understood. We report here that growth factor–induced epithelial cell migration is critically dependent on the crosstalk of two molecular switches, namely phosphorylation switch (P-switch) and transcriptional switch (T-switch). P-switch refers to dynamic interactions of deleted in liver cancer 1 (DLC1) and PI3K with tensin-3 (TNS3), phosphatase and tensin homolog (PTEN), C-terminal tension, and vav guanine nucleotide exchange factor 2 (VAV2) that are dictated by mitogen-activated protein kinase kinase 1/2–extracellular signal–regulated protein kinase 1/2–dependent phosphorylation of TNS3, PTEN, and VAV2. Phosphorylation of TNS3 and PTEN on specific Thr residues led to the switch of DLC1–TNS3 and PI3K–PTEN complexes to DLC1–PTEN and PI3K–TNS3 complexes, whereas Ser phosphorylation of VAV2 promotes the transition of the PI3K–TNS3/PTEN complexes to PI3K–VAV2 complex. T-switch denotes an increase in C-terminal tension transcription/expression regulated by both extracellular signal–regulated protein kinase 1/2 and signal transducer and activator of transcription 3 (STAT3) via interleukin-6–Janus kinase–STAT3 signaling pathway. We have found that, the P-switch is indispensable for both the initiation and continuation of cell migration induced by growth factors, whereas the T-switch is only required to sustain cell migration. The interplay of the two switches facilitated by the interleukin-6–Janus kinase–STAT3 pathway governs a sequence of dynamic protein–protein interactions for sustained cell migration. That a similar mechanism is employed by both normal and tumorigenic epithelial cells to drive their respective migration suggests that the P-switch and T-switch are general regulators of epithelial cell migration and potential therapeutic targets.

NCOR1 Sustains Colorectal Cancer Cell Growth and Protects against Cellular Senescence

Simple Summary

NCOR1 is a scaffold protein that interacts with multiple partners to repress gene transcription. NCOR1 controls immunometabolic functions in several tissues and has been recently shown to protect against experimental colitis in mice. Our laboratory has observed a pro-proliferative role of NCOR1 in normal intestinal epithelial cells. However, it is unclear whether NCOR1 is functionally involved in colon cancer. This study demonstrated that NCOR1 is required for colorectal cancer cell growth. Depletion of NCOR1 caused these cells to become senescent. Transcriptomic signatures confirmed these observations but also predicted the potential for these cells to become pro-invasive. Thus, NCOR1 plays a novel role in preventing cancer-associated senescence and could represent a target for controlling colon cancer progression.

Abstract

NCOR1 is a corepressor that mediates transcriptional repression through its association with nuclear receptors and specific transcription factors. Some evidence supports a role for NCOR1 in neonatal intestinal epithelium maturation and the maintenance of epithelial integrity during experimental colitis in mice. We hypothesized that NCOR1 could control colorectal cancer cell proliferation and tumorigenicity. Conditional intestinal epithelial deletion of Ncor1 in Apc^Min/+ mice resulted in a significant reduction in polyposis. RNAi targeting of NCOR1 in Caco-2/15 and HT-29 cell lines led to a reduction in cell growth, characterized by cellular senescence associated with a secretory phenotype. Tumor growth of HT-29 cells was reduced in the absence of NCOR1 in the mouse xenografts. RNA-seq transcriptome profiling of colon cancer cells confirmed the senescence phenotype in the absence of NCOR1 and predicted the occurrence of a pro-migration cellular signature in this context. SOX2, a transcription factor essential for pluripotency of embryonic stem cells, was induced under these conditions. In conclusion, depletion of NCOR1 reduced intestinal polyposis in mice and caused growth arrest, leading to senescence in human colorectal cell lines. The acquisition of a pro-metastasis signature in the absence of NCOR1 could indicate long-term potential adverse consequences of colon-cancer-induced senescence.

Fermitin family member 2 promotes melanoma progression by enhancing the binding of p-α-Pix to Rac1 to activate the MAPK pathway

We identified fermitin family member 2 (FERMT2, also known as kindlin-2) as a potential target in A375 cell line by siRNA library screening. Drugs that target mutant BRAF kinase lack durable efficacy in the treatment of melanoma because of acquired resistance, thus the identification of novel therapeutic targets is needed. Immunohistochemistry was used to identify kindlin-2 expression in melanoma samples. The interaction between kindlin-2 and Rac1 or p-Rac/Cdc42 guanine nucleotide exchange factor 6 (α-Pix) was investigated. Finally, the tumor suppressive role of kindlin-2 was validated in vitro and in vivo. Analysis of clinical samples and Oncomine data showed that higher levels of kindlin-2 predicted a more advanced T stage and M stage and facilitated metastasis and recurrence. Kindlin-2 knockdown significantly inhibited melanoma growth and migration, whereas kindlin-2 overexpression had the inverse effects. Further study showed that kindlin-2 could specifically bind to p-α-Pix(S13) and Rac1 to induce a switch from the inactive Rac1-GDP conformation to the active Rac1-GTP conformation and then stimulate the downstream MAPK pathway. Moreover, we revealed that a Rac1 inhibitor suppressed melanoma growth and metastasis and the combination of the Rac1 inhibitor and vemurafenib resulted in a better therapeutic outcome than monotherapy in melanoma with high kindlin-2 expression and BRAF mutation. Our results demonstrated that kindlin-2 promoted melanoma progression, which was attributed to specific binding to p-α-Pix(S13) and Rac1 to stimulate the downstream MAPK pathway. Thus, kindlin-2 could be a potential therapeutic target for treating melanoma.

Decoding leader cells in collective cancer invasion

Collective cancer invasion with leader-follower organization is increasingly recognized as a predominant mechanism in the metastatic cascade. Leader cells support cancer invasion by creating invasion tracks, sensing environmental cues and coordinating with follower cells biochemically and biomechanically. With the latest developments in experimental and computational models and analysis techniques, the range of specific traits and features of leader cells reported in the literature is rapidly expanding. Yet, despite their importance, there is no consensus on how leader cells arise or their essential characteristics. In this Perspective, we propose a framework for defining the essential aspects of leader cells and provide a unifying perspective on the varying cellular and molecular programmes that are adopted by each leader cell subtype to accomplish their functions. This Perspective can lead to more effective strategies to interdict a major contributor to metastatic capability.

Discovery of Cellular RhoA Functions by the Integrated Application of Gene Set Enrichment Analysis

The small GTPase RhoA has been studied extensively for its role in actin dynamics. In this study, multiple bioinformatics tools were applied cooperatively to the microarray dataset GSE64714 to explore previously unidentified functions of RhoA. Comparative gene expression analysis revealed 545 differentially expressed genes in RhoA-null cells versus controls. Gene set enrichment analysis (GSEA) was conducted with three gene set collections: (1) the hallmark, (2) the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, and (3) the Gene Ontology Biological Process. GSEA results showed that RhoA is related strongly to diverse pathways: cell cycle/growth, DNA repair, metabolism, keratinization, response to fungus, and vesicular transport. These functions were verified by heatmap analysis, KEGG pathway diagramming, and direct acyclic graphing. The use of multiple gene set collections restricted the leakage of information extracted. However, gene sets from individual collections are heterogenous in gene element composition, number, and the contextual meaning embraced in names. Indeed, there was a limit to deriving functions with high accuracy and reliability simply from gene set names. The comparison of multiple gene set collections showed that although the gene sets had similar names, the gene elements were extremely heterogeneous. Thus, the type of collection chosen and the analytical context influence the interpretation of GSEA results. Nonetheless, the analyses of multiple collections made it possible to derive robust and consistent function identifications. This study confirmed several well-described roles of RhoA and revealed less explored functions, suggesting future research directions.

Moringa Oleifera Seed Extract Concomitantly Supplemented with Chemotherapy Worsens Tumor Progression in Mice with Triple Negative Breast Cancer and Obesity

Triple negative breast cancer (TNBC) is an aggressive and highly metastatic breast cancer subtype with limited treatment options. Obesity and insulin resistance are associated with a worse prognosis in those with TNBC. Moringa oleifera (moringa) is a tropical edible plant used for both food and medicinal purposes and found to have anti-obesity and anti-cancer effects in vitro and in preclinical models. The anti-cancer effects of moringa seed extract alone and in combination with chemotherapy were evaluated in immunocompromised female mice with diet-induced obesity bearing MDA-MB-231-derived xenograft tumors. Moringa supplementation protected against high-fat diet- and chemotherapy-induced increases in fasting glucose and improved insulin sensitivity. Moringa supplementation alone did not attenuate tumor growth relative to chemotherapy alone, and in combination worsened tumor progression. Moringa supplementation alone reduced angiogenesis, but this effect was abrogated in combination with chemotherapy. Moringa supplementation may be an effective strategy to improve metabolic health in mice with obesity and TNBC and reduce angiogenesis in tumors, but may have a negative interaction when used as a concurrent complementary therapy. Caution should be taken when considering the consumption of moringa seed extracts while receiving chemotherapy for breast cancer treatment. Further investigations of alternative timings of moringa therapy are warranted.

High Expression of RhoF Predicts Worse Overall Survival: A Potential Therapeutic Target for non-M3 Acute Myeloid Leukemia

Rho GTPases are involved in multiple human malignancies and diverse biological functions. However, the patterns and prognostic significance of the expression of RhoD subfamily in acute myeloid leukemia (AML) remain unknown. Here, we detected the expressions of RhoD subfamily genes in AML on the basis of several published datasets and analyzed the survival of RhoD subfamily across the TCGA profiles and in a GEO series. We found that the expression of RhoF, but not RhoD, increased in AML patients in TCGA and GEO (all P<0.001); the survival analysis of two independent cohorts demonstrated that higher RhoF expression was significantly associated with poorer overall survival (OS) (P<0.001), whereas RhoD expression had no significant effect on OS in patients with AML (P>0.05); the subgroup analysis showed that high RhoF expression was correlated with poor 1-, 3-, and 5-year OS (P<0.05 for all); upregulated RhoF expression had a more significant prognostic value for OS in the younger patients (age<60), the intensive chemotherapy group, and wild-type groups (IDH1, NRAS, and TP53) (P<0.05 for all). Multivariate analysis indicated high RhoF expression as a strongly independent unfavorable prognostic factor for OS in patients without transplantation (P<0.05). Furthermore, a higher RhoF expression was closely associated with an older age, intermediate-/poor-risk cytogenetics and mutations in IDH1, NRAS, and TP53. RhoF expression was negatively correlated with BM blasts (P=0.020) and WBC (P=0.003). These findings suggest that high RhoF expression is associated with worsening OS in AML patients and is a potential therapeutic target for the treatment of AML.

Estimating the predictive power of silent mutations on cancer classification and prognosis

In recent years it has been shown that silent mutations, in and out of the coding region, can affect gene expression and may be related to tumorigenesis and cancer cell fitness. However, the predictive ability of these mutations for cancer type diagnosis and prognosis has not been evaluated yet. In the current study, based on the analysis of 9,915 cancer genomes and approximately three million mutations, we provide a comprehensive quantitative evaluation of the predictive power of various types of silent and non-silent mutations over cancer classification and prognosis. The results indicate that silent-mutation models outperform the equivalent null models in classifying all examined cancer types and in estimating the probability of survival 10 years after the initial diagnosis. Additionally, combining both non-silent and silent mutations achieved the best classification results for 68% of the cancer types and the best survival estimation results for up to nine years after the diagnosis. Thus, silent mutations hold considerable predictive power over both cancer classification and prognosis, most likely due to their effect on gene expression. It is highly advised that silent mutations are integrated in cancer research in order to unravel the full genomic landscape of cancer and its ramifications on cancer fitness.

Pathogenic nsSNPs that increase the risks of cancers among the Orang Asli and Malays

Single-nucleotide polymorphisms (SNPs) are the most common genetic variations for various complex human diseases, including cancers. Genome-wide association studies (GWAS) have identified numerous SNPs that increase cancer risks, such as breast cancer, colorectal cancer, and leukemia. These SNPs were cataloged for scientific use. However, GWAS are often conducted on certain populations in which the Orang Asli and Malays were not included. Therefore, we have developed a bioinformatic pipeline to mine the whole-genome sequence databases of the Orang Asli and Malays to determine the presence of pathogenic SNPs that might increase the risks of cancers among them. Five different in silico tools, SIFT, PROVEAN, Poly-Phen-2, Condel, and PANTHER, were used to predict and assess the functional impacts of the SNPs. Out of the 80 cancer-related nsSNPs from the GWAS dataset, 52 nsSNPs were found among the Orang Asli and Malays. They were further analyzed using the bioinformatic pipeline to identify the pathogenic variants. Three nsSNPs; rs1126809 (TYR), rs10936600 (LRRC34), and rs757978 (FARP2), were found as the most damaging cancer pathogenic variants. These mutations alter the protein interface and change the allosteric sites of the respective proteins. As TYR, LRRC34, and FARP2 genes play important roles in numerous cellular processes such as cell proliferation, differentiation, growth, and cell survival; therefore, any impairment on the protein function could be involved in the development of cancer. rs1126809, rs10936600, and rs757978 are the important pathogenic variants that increase the risks of cancers among the Orang Asli and Malays. The roles and impacts of these variants in cancers will require further investigations using in vitro cancer models.

Rho GTPase Activating Protein 9 (ARHGAP9) in Human Cancers

BACKGROUND

In recent years, targeted therapy combined with traditional chemoradiotherapy and surgery has brought new opportunities for cancer treatment. However, the complex characteristics of cancer, such as heterogeneity and diversity, limit the clinical success of targeted drugs. The discovery of new cancer targets and deepening the understanding of their functional mechanisms will bring additional promising application prospects for the research and development of personalized cancer-targeted drugs.

OBJECTIVE

This study aimed to summarize the role of the Rho GTPase activating protein 9 (ARHGAP9) gene in tumorigenesis and development to discover therapeutic targets for cancer in the future.

METHODS

For this review, we collected patents from the databases of Espacenet and WIPO and articles from PubMed that were related to the ARHGAP9 gene.

RESULTS

Genetic/epigenetic variations and abnormal expression of the ARHGAP9 gene are closely associated with a variety of diseases, including cancer. ARHGAP9 can inactivate Rho GTPases by hydrolyzing GTP into GDP and regulate cancer cellular events, including proliferation, differentiation, apoptosis, migration and invasion, by inhibiting JNK/ERK/p38 and PI3K/AKT signaling pathways. In addition to reviewing these mechanisms, we assessed various patents on ARHGAP9 to determine whether ARHGAP9 might be used as a predictive biomarker for diagnosis/prognosis evaluation and a druggable target for cancer treatment.

CONCLUSION

In this review, the current knowledge of ARHGAP9 in cancer is summarized with an emphasis on its molecular function, regulatory mechanism and disease implications. Its characterization is crucial to understanding its important roles during different stages of cancer progression and therapy as a predictive biomarker and/or target.

Post-Translational Modification and Subcellular Compartmentalization: Emerging Concepts on the Regulation and Physiopathological Relevance of RhoGTPases

Cells and tissues are continuously exposed to both chemical and physical stimuli and dynamically adapt and respond to this variety of external cues to ensure cellular homeostasis, regulated development and tissue-specific differentiation. Alterations of these pathways promote disease progression-a prominent example being cancer. Rho GTPases are key regulators of the remodeling of cytoskeleton and cell membranes and their coordination and integration with different biological processes, including cell polarization and motility, as well as other signaling networks such as growth signaling and proliferation. Apart from the control of GTP-GDP cycling, Rho GTPase activity is spatially and temporally regulated by post-translation modifications (PTMs) and their assembly onto specific protein complexes, which determine their controlled activity at distinct cellular compartments. Although Rho GTPases were traditionally conceived as targeted from the cytosol to the plasma membrane to exert their activity, recent research demonstrates that active pools of different Rho GTPases also localize to endomembranes and the nucleus. In this review, we discuss how PTM-driven modulation of Rho GTPases provides a versatile mechanism for their compartmentalization and functional regulation. Understanding how the subcellular sorting of active small GTPase pools occurs and what its functional significance is could reveal novel therapeutic opportunities.

New insights into the mechanisms underlying 5-fluorouracil-induced intestinal toxicity based on transcriptomic and metabolomic responses in human intestinal organoids

5-Fluorouracil (5-FU) is a widely used chemotherapeutical that induces acute toxicity in the small and large intestine of patients. Symptoms can be severe and lead to the interruption of cancer treatments. However, there is limited understanding of the molecular mechanisms underlying 5-FU-induced intestinal toxicity. In this study, well-established 3D organoid models of human colon and small intestine (SI) were used to characterize 5-FU transcriptomic and metabolomic responses. Clinically relevant 5-FU concentrations for in vitro testing in organoids were established using physiologically based pharmacokinetic simulation of dosing regimens recommended for cancer patients, resulting in exposures to 10, 100 and 1000 µM. After treatment, different measurements were performed: cell viability and apoptosis; image analysis of cell morphological changes; RNA sequencing; and metabolome analysis of supernatant from organoids cultures. Based on analysis of the differentially expressed genes, the most prominent molecular pathways affected by 5-FU included cell cycle, p53 signalling, mitochondrial ATP synthesis and apoptosis. Short time-series expression miner demonstrated tissue-specific mechanisms affected by 5-FU, namely biosynthesis and transport of small molecules, and mRNA translation for colon; cell signalling mediated by Rho GTPases and fork-head box transcription factors for SI. Metabolomic analysis showed that in addition to the effects on TCA cycle and oxidative stress in both organoids, tissue-specific metabolic alterations were also induced by 5-FU. Multi-omics integration identified transcription factor E2F1, a regulator of cell cycle and apoptosis, as the best key node across all samples. These results provide new insights into 5-FU toxicity mechanisms and underline the relevance of human organoid models in the safety assessment in drug development.

Tumour cell CD99 regulates transendothelial migration via CDC42 and actin remodelling

Metastasis requires tumour cells to cross endothelial cell (EC) barriers using pathways similar to those used by leucocytes during inflammation. Cell surface CD99 is expressed by healthy leucocytes and ECs, and participates in inflammatory transendothelial migration (TEM). Tumour cells also express CD99, and we have analysed its role in tumour progression and cancer cell TEM. Tumour cell CD99 was required for adhesion to ECs but inhibited invasion of the endothelial barrier and migratory activity. Furthermore, CD99 depletion in tumour cells caused redistribution of the actin cytoskeleton and increased activity of the Rho GTPase CDC42, known for its role in actin remodelling and cell migration. In a xenograft model of breast cancer, tumour cell CD99 expression inhibited metastatic progression, and patient samples showed reduced expression of the CD99 gene in brain metastases compared to matched primary breast tumours. We conclude that CD99 negatively regulates CDC42 and cell migration. However, CD99 has both pro- and anti-tumour activity, and our data suggest that this results in part from its functional linkage to CDC42 and the diverse signalling pathways downstream of this Rho GTPase. This article has an associated First Person interview with the first author of the paper.

ORMDL1 is upregulated and associated with favorable outcomes in colorectal cancer

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The association between ORMDL1 expression and clinipathological characteristic in colorectal cancer (CRC) has not been reported before, which is addressed in this study.

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Although ORMDL1 is generally upregulated in CRC, high expression of ORMDL1 is associated with longer survival; the combination of ORMDL1 expression and other biomarkers to stratify and predict prognosis in CRC is worth to explore.

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ORMDL1 seems to influence cell cytoskeleton dynamics through Rho GTPase, other than canonical EMT related transcription factors.

Background

The ORMDL1 gene is known as a crucial negative regulator of sphingolipid biogenesis. However, the ORMDL1 gene has rarely been studied in a tumor-related context. Therefore, its prognostic value and functional significance in colorectal cancer (CRC) remain to be explored.

Methods

TCGA CRC cohort analysis, qRT-PCR, and immunohistochemistry (IHC) were used to examine the ORMDL1 expression level. The association between ORMDL1 expression and various clinical characteristics was analyzed by chi-square tests. The overall survival (OS) of CRC patients was analyzed by Kaplan-Meier analysis. In vitro and in vivo cell-based assays were performed to explore the role of ORMDL1 in cell proliferation, invasion and migration. Transcriptional changes in cells with either ORMDL1 knockdown or overexpression were compared and analyzed.

Results

ORMDL1 was upregulated in CRC tissues in both the TCGA and our cohort. Interestingly, its expression was significantly lower in patients with metastasis than in patients without metastasis, and the high expression group had longer OS than the low expression group. Knockdown of ORMDL1 expression can promote proliferation, colony formation and invasion, while attenuating migration in CRC cell lines. In contrast, forced overexpression of ORMDL1 reduced cell proliferation, colony formation and invasion, while enhancing cell migration. Stable knockdown of ORMDL1 can promote cancer cell proliferation in vivo to some extent. Finally, Rho GTPase activity was influenced by ORMDL1, and the expression of ORMDL1 was enhanced by DTT treatment.

Conclusion

ORMDL1 is upregulated and may serve as a biomarker to predict favourable outcomes in colorectal cancer.

Mechanism of WASP and WAVE family proteins in the progression of prostate cancer

Prostate cancer (PCa) is the second most commonly diagnosed and third lethal cause of death from cancer in men worldwide. Despite the availability of vast treatment procedures, still the high occurrence of invasion and metastasis of PCa are reported in cancer patients. The WASP (Wiskott-Aldrich syndrome protein) and WAVE (WASP family verprolin homologous protein) family of proteins are actin cytoskeleton regulatory proteins, reported to enhance cancer cell invasion and migration in prostate cancer. Hence, this review sheds light on the studies that explored the potential role of WASP and WAVE family of proteins in invasion and metastasis of prostate cancer. The research articles explored for the completion of this review were mostly from PubMed and Google Scholar by using the appropriate keywords for indexing. The conserved function of WASP and WAVE protein family is to receive the upstream signals from the Rho GTPase family and transmit them to activate the Arp2/3 complex that leads to rapid actin polymerization at leading edge of cells, which is crucial for PCa metastasis. Therefore, targeting these proteins could reflect a very interesting therapeutic opportunity to combat prostate cancer.

Bioinformatic analysis of RHO family of GTPases identifies RAC1 pharmacological inhibition as a new therapeutic strategy for hepatocellular carcinoma

OBJECTIVE

The RHO family of GTPases, particularly RAC1, has been linked with hepatocarcinogenesis, suggesting that their inhibition might be a rational therapeutic approach. We aimed to identify and target deregulated RHO family members in human hepatocellular carcinoma (HCC).

DESIGN

We studied expression deregulation, clinical prognosis and transcription programmes relevant to HCC using public datasets. The therapeutic potential of RAC1 inhibitors in HCC was study in vitro and in vivo. RNA-Seq analysis and their correlation with the three different HCC datasets were used to characterise the underlying mechanism on RAC1 inhibition. The therapeutic effect of RAC1 inhibition on liver fibrosis was evaluated.

RESULTS

Among the RHO family of GTPases we observed that RAC1 is upregulated, correlates with poor patient survival, and is strongly linked with a prooncogenic transcriptional programme. From a panel of novel RAC1 inhibitors studied, 1D-142 was able to induce apoptosis and cell cycle arrest in HCC cells, displaying a stronger effect in highly proliferative cells. Partial rescue of the RAC1-related oncogenic transcriptional programme was obtained on RAC1 inhibition by 1D-142 in HCC. Most importantly, the RAC1 inhibitor 1D-142 strongly reduce tumour growth and intrahepatic metastasis in HCC mice models. Additionally, 1D-142 decreases hepatic stellate cell activation and exerts an anti-fibrotic effect in vivo.

CONCLUSIONS

The bioinformatics analysis of the HCC datasets, allows identifying RAC1 as a new therapeutic target for HCC. The targeted inhibition of RAC1 by 1D-142 resulted in a potent antitumoural effect in highly proliferative HCC established in fibrotic livers.

NecroX-5 Can Suppress Melanoma Metastasis by Reducing the Expression of Rho-Family GTPases

NecroX-5 (NX-5) is a cell-permeable necrosis inhibitor with cytoprotective effects. Although it has been reported to inhibit lung and breast cancer metastasis by modulating migration, its therapeutic effect on melanoma metastasis is still unknown. In this study, we examined the anti-metastatic effect of NX-5 on melanoma cell lines and its related therapeutic mechanism. The anti-metastatic effect of NX-5 on melanoma cell lines was determined using a transwell migration assay. We performed a quantitative real-time polymerase chain reaction and western blot analysis to measure changes in the expression of mRNA and protein, respectively, for major mediators of Rho-family GTPases after NX-5 treatment in melanoma cells. In addition, after constructing the 3D melanoma model, the expression of Rho-family GTPases was measured by immunohistochemistry. NX-5 (10 μM and 20 μM) treatment significantly reduced melanoma cell migration (p < 0.01). Additionally, NX-5 (20 μM) treatment significantly decreased the mRNA and protein expression levels of Cdc42, Rac1, and RhoA in melanoma cells compared with the untreated group (p < 0.001 and p < 0.05, respectively). Immunohistochemistry for our 3D melanoma model showed that Cdc42, Rac1, and RhoA were constitutively expressed in the nuclei of melanoma cells of the untreated group, and NX-5 treatment decreased their expression. These results demonstrate that NX-5 can suppress melanoma metastasis by reducing the expression of Rho-family GTPases.

SmgGDS: An Emerging Master Regulator of Prenylation and Trafficking by Small GTPases in the Ras and Rho Families

Newly synthesized small GTPases in the Ras and Rho families are prenylated by cytosolic prenyltransferases and then escorted by chaperones to membranes, the nucleus, and other sites where the GTPases participate in a variety of signaling cascades. Understanding how prenylation and trafficking are regulated will help define new therapeutic strategies for cancer and other disorders involving abnormal signaling by these small GTPases. A growing body of evidence indicates that splice variants of SmgGDS (gene name RAP1GDS1) are major regulators of the prenylation, post-prenylation processing, and trafficking of Ras and Rho family members. SmgGDS-607 binds pre-prenylated small GTPases, while SmgGDS-558 binds prenylated small GTPases. This review discusses the history of SmgGDS research and explains our current understanding of how SmgGDS splice variants regulate the prenylation and trafficking of small GTPases. We discuss recent evidence that mutant forms of RabL3 and Rab22a control the release of small GTPases from SmgGDS, and review the inhibitory actions of DiRas1, which competitively blocks the binding of other small GTPases to SmgGDS. We conclude with a discussion of current strategies for therapeutic targeting of SmgGDS in cancer involving splice-switching oligonucleotides and peptide inhibitors.

Rac1-mediated sustained β4 integrin level develops reattachment ability of breast cancer cells after anchorage loss

Previously, we reported that non-apoptotic cell death was induced in non-malignant mammary epithelial cells (HMECs) upon loss of anchorage during 48 h incubation in suspension. In this study, we examined HMECs in suspension at an earlier time point and found that most of them lost attachment ability to substrata when replated, although >80% were alive. This suggested that HMECs lost reattachment ability (RA) prior to cell death upon detachment. Concomitant with the loss of RA, a decrease in the levels of β1 and β4 integrin was observed. In sharp contrast, breast cancer cells retained integrin levels, reattached to substrata, and formed colonies after exposure to anchorage loss as efficiently as those maintained under adherent conditions. Such RA of cancer cells is essential for the metastatic process, especially for establishing adhesion contact with ECM in the secondary organ after systemic circulation. Further analysis suggested that sustained levels of β4 integrin, which was mediated by Rac1, was critical for RA after anchorage loss and lung metastasis of breast cancer cells. In the cancer cells, persistent Rac1 activity enhanced escape of β4 integrin from lysosomal degradation depending on actin-related protein 2/3 and TBC1D2, a GTPase-activating protein of Rab7 GTPase. Notably, simultaneous high expression of ITGB4 and RAC1 was associated with poor prognosis in patients with breast cancer. Therefore, β4 integrin and Rac1 are attractive therapeutic targets to eliminate RA in cancer cells, thereby preventing the initial step of colonization at the secondary organ during metastasis.

Silencing of METTL3 effectively hinders invasion and metastasis of prostate cancer cells

Background: Since primary prostate cancer (PCa) can advance to the life-threatening metastatic PCa, exploring the molecular mechanisms underlying PCa metastasis is crucial for developing the novel targeted preventive strategies for decreasing the mortality of PCa. RNA N⁶-methyladenosine (m⁶A) is an emerging regulatory mechanism for gene expression and its specific roles in PCa progression remains elusive. Methods: Western blotting, quantitative real-time PCR and immunohistochemical analyses were used to detect target gene expression in PCa cells in vitro and prostate tissues from patients. RNA immunoprecipitation was conducted to analyze the specific binding of mRNA to the target protein. Migration and invasion assays were used to assess the migratory capacities of cancer cells. The correlation between target gene expression and survival rate of PCa patients was analyzed based the TCGA database. Results: We found that total RNA N⁶-methyladenosine (m⁶A) modification levels were markedly upregulated in human PCa tissues due to increased expression of methyltransferase like 3 (METTL3). Further studies revealed that the migratory and invasive capacities of PCa cells were markedly suppressed upon METTL3 knockdown. Mechanistically, METTL3 mediates m⁶A modification of USP4 mRNA at A2696, and m⁶A reader protein YTHDF2 binds to and induces degradation of USP4 mRNA by recruiting RNA-binding protein HNRNPD to the mRNA. Decrease of USP4 fails to remove the ubiquitin group from ELAVL1 protein, resulting in a reduction of ELAVL1 protein. Lastly, downregulation of ELAVL1 in turn increases ARHGDIA expression, promoting migration and invasion of PCa cells. Conclusions: Our findings highlight the role of METTL3 in modulating invasion and metastasis of PCa cells, providing insight into promising therapeutic strategies for hindering PCa progressing to deadly metastases.

Overexpression of microRNA-19a-3p promotes lymph node metastasis of esophageal squamous cell carcinoma via the RAC1/CDC42-PAK1 pathway

BACKGROUND

A tendency towards extensive regional lymph node metastasis (LNM) is a typical clinical characteristic of esophageal squamous cell carcinoma (ESCC). Up-regulated microRNA (miR)-19a-3p was verified as a predictor of LNM in ESCC in previous microarray analyses, but the underlying mechanisms remain unclear. Here, in vitro experiments were performed to confirm the effect of miR-19a-3p on promoting LNM and to explore the underlying mechanisms.

METHODS

KYSE-150 and TE-1 cell lines were transfected with lentiviral vectors to inhibit miR-19a-3p (LV-miR-19a-3p-inhibition), and cell proliferation, invasion, and migration were assessed. Target genes of miR-19a-3p were identified by sequencing analysis and quantitative reverse transcription PCR (qRT-PCR); Western blotting was performed to confirm targets and explore the potential mechanisms underlying the effect of miR-19a-3p on LNM.

RESULTS

miR-19a-3p had no effect on ESCC cell proliferation, whereas miR-19a-3p overexpression promoted the invasion and migration of ESCC cells. qRT-PCR verification and western blot analysis showed that LV-miR-19a-3p-inhibition downregulated cell division cycle 42 (CDC42), Rac family small GTPase 1 (RAC1), and p21 activated kinase 1 (PAK1).

CONCLUSIONS

Overexpression of miR-19a-3p increased the invasion and migration of ESCC cells via the RAC1/CDC42-PAK1 pathway, suggesting that this pathway mediates the effect of miR-19a-3p on promoting LNM in ESCC.

Regulation of Rho GTPases in the Vasculature by Cullin3-Based E3 Ligase Complexes

Cullin3-based ubiquitin E3 ligases induce ubiquitination of substrates leading to their proteasomal or lysosomal degradation. BTB proteins serve as adaptors by binding to Cullin3 and recruiting substrate proteins, which enables specific recognition of a broad spectrum of targets. Hence, Cullin3 and its adaptors are involved in myriad cellular processes and organ functions. Cullin3-based ubiquitin E3 ligase complexes target small GTPases of the Rho subfamily, which are key regulators of cytoskeletal dynamics and cell adhesion. In this mini review, we discuss recent insights in Cullin3-mediated regulation of Rho GTPases and their impact on cellular function and disease. Intriguingly, upstream regulators of Rho GTPases are targeted by Cullin3 complexes as well. Thus, Rho GTPase signaling is regulated by Cullin3 on multiple levels. In addition, we address current knowledge of Cullin3 in regulating vascular function, focusing on its prominent role in endothelial barrier function, angiogenesis and the regulation of blood pressure.

The Crossroads between RAS and RHO Signaling Pathways in Cellular Transformation, Motility and Contraction

Ras and Rho proteins are GTP-regulated molecular switches that control multiple signaling pathways in eukaryotic cells. Ras was among the first identified oncogenes, and it appears mutated in many forms of human cancer. It mainly promotes proliferation and survival through the MAPK pathway and the PI3K/AKT pathways, respectively. However, the myriad proteins close to the plasma membrane that activate or inhibit Ras make it a major regulator of many apparently unrelated pathways. On the other hand, Rho is weakly oncogenic by itself, but it critically regulates microfilament dynamics; that is, actin polymerization, disassembly and contraction. Polymerization is driven mainly by the Arp2/3 complex and formins, whereas contraction depends on myosin mini-filament assembly and activity. These two pathways intersect at numerous points: from Ras-dependent triggering of Rho activators, some of which act through PI3K, to mechanical feedback driven by actomyosin action. Here, we describe the main points of connection between the Ras and Rho pathways as they coordinately drive oncogenic transformation. We emphasize the biochemical crosstalk that drives actomyosin contraction driven by Ras in a Rho-dependent manner. We also describe possible routes of mechanical feedback through which myosin II activation may control Ras/Rho activation.

In vivo Functional Genomics for Undiagnosed Patients: The Impact of Small GTPases Signaling Dysregulation at Pan-Embryo Developmental Scale

While individually rare, disorders affecting development collectively represent a substantial clinical, psychological, and socioeconomic burden to patients, families, and society. Insights into the molecular mechanisms underlying these disorders are required to speed up diagnosis, improve counseling, and optimize management toward targeted therapies. Genome sequencing is now unveiling previously unexplored genetic variations in undiagnosed patients, which require functional validation and mechanistic understanding, particularly when dealing with novel nosologic entities. Functional perturbations of key regulators acting on signals' intersections of evolutionarily conserved pathways in these pathological conditions hinder the fine balance between various developmental inputs governing morphogenesis and homeostasis. However, the distinct mechanisms by which these hubs orchestrate pathways to ensure the developmental coordinates are poorly understood. Integrative functional genomics implementing quantitative in vivo models of embryogenesis with subcellular precision in whole organisms contribute to answering these questions. Here, we review the current knowledge on genes and mechanisms critically involved in developmental syndromes and pediatric cancers, revealed by genomic sequencing and in vivo models such as insects, worms and fish. We focus on the monomeric GTPases of the RAS superfamily and their influence on crucial developmental signals and processes. We next discuss the effectiveness of exponentially growing functional assays employing tractable models to identify regulatory crossroads. Unprecedented sophistications are now possible in zebrafish, i.e., genome editing with single-nucleotide precision, nanoimaging, highly resolved recording of multiple small molecules activity, and simultaneous monitoring of brain circuits and complex behavioral response. These assets permit accurate real-time reporting of dynamic small GTPases-controlled processes in entire organisms, owning the potential to tackle rare disease mechanisms.

Emerging role of lncRNAs in the regulation of Rho GTPase pathway

The Ras homolog (Rho) family of small GTPases comprise several proteins with prominent roles in regulation of cell cycle transition, cell migration, and remodeling of actin cytoskeleton. Expression of these proteins is regulated by several factors among them are long non-coding RNAs (lncRNAs). The impact of lncRNAs on Rho GTPases signaling can be exerted through direct modulation of expression of these proteins or influencing expression of miRNAs that negatively regulate Rho GTPases. LINC00974/miR-122/RhoA, MALAT1/miR-429/RhoA, ZFAS1/miR-3924/RhoA/ROCK2, PCAT6/miR-326/RhoA/ROCK, SMILR/miR-141/RhoA/ROCK, DAPK1/miR-182/RhoA, GAS5/miR663a/RhoB, H19/miR-15b/CDC42/PAK1, TDRG1/miR-93/RhoC, TUG1/miR-498/CDC42, UCA1/miR-18a/Cdc42 and UCA1/miR-182/Cdc42 are examples of lncRNAs/miRNAs axes that regulate Rho GTPases. In the present manuscript, we describe the role of lncRNAs on Rho GTPases.

Novel CTRP8-RXFP1-JAK3-STAT3 axis promotes Cdc42-dependent actin remodeling for enhanced filopodia formation and motility in human glioblastoma cells

C1q tumor necrosis factor‐related peptide 8 (CTRP8) is the least studied member of the C1Q‐TNF‐related peptide family. We identified CTRP8 as a ligand of the G protein‐coupled receptor relaxin family peptide receptor 1 (RXFP1) in glioblastoma multiforme (GBM). The CTRP8‐RXFP1 ligand–receptor system protects human GBM cells against the DNA‐alkylating damage‐inducing temozolomide (TMZ), the drug of choice for the treatment of patients with GBM. The DNA protective role of CTRP8 was dependent on a functional RXFP1‐STAT3 signaling cascade and targeted the monofunctional glycosylase N‐methylpurine DNA glycosylase (MPG) for more efficient base excision repair of TMZ‐induced DNA‐damaged sites. CTRP8 also improved the survival of GBM cells by upregulating anti‐apoptotic BCl‐2 and BCL‐XL. Here, we have identified Janus‐activated kinase 3 (JAK3) as a novel member of a novel CTRP8‐RXFP1‐JAK3‐STAT3 signaling cascade that caused an increase in cellular protein content and activity of the small Rho GTPase Cdc42. This is associated with significant F‐actin remodeling and increased GBM motility. Cdc42 was critically important for the upregulation of the actin nucleation complex N‐Wiskott–Aldrich syndrome protein/Arp3/4 and actin elongation factor profilin‐1. The activation of the RXFP1‐JAK3‐STAT3‐Cdc42 axis by both RXFP1 agonists, CTRP8 and relaxin‐2, caused extensive filopodia formation. This coincided with enhanced activity of ezrin, a key factor in tethering F‐actin to the plasma membrane, and inhibition of the actin filament severing activity of cofilin. The F‐actin remodeling and pro‐migratory activities promoted by the novel RXFP1‐JAK3‐STAT3‐Cdc42 axis were blocked by JAK3 inhibitor tofacitinib and STAT3 inhibitor STAT3 inhibitor VI. This provides a new rationale for the design of JAK3 and STAT3 inhibitors with better brain permeability for clinical treatment of the pervasive brain invasiveness of GBM.

Gene Expression of PSORI-CM01 and Yinxieling in the Treatment of Psoriasis Vulgaris

Background. This study aimed to explore the mechanisms of action of the PSORI-CM01 and Yinxieling formulas in the treatment of patients with psoriasis vulgaris by analyzing gene expression in peripheral blood mononuclear cells (PBMCs). Methods. PBMC samples were collected from 21 patients before and after treatment. The study included nine patients in the PSORI-CM01 treatment group, 12 patients in the Yinxieling treatment group, and nine patients in the healthy control group. Gene expression levels in PBMCs were determined using the Affymetrix gene chip technology. Results. In the PSORI-CM01 group before and after treatment, a total of 668 differentially expressed genes were found, of which 445 were upregulated and 223 were downregulated. Before and after Yinxieling treatment, 657 differentially expressed genes were found, of which 168 were upregulated and 489 were downregulated. Venn analysis showed that 78 genes were not differentially expressed in the PSORI-CM01 group and 74 were not differentially expressed in the Yinxieling group compared with those in the controls. Among these genes, 72 genes were common to both groups, which were the genes on which the two drugs acted jointly. The results of KEGG analysis and Venn analysis on the signalling pathways of drug action in treatment groups showed that haemostasis and pathways involving Rho GTPases were common signalling pathways of drug action in the two groups. Conclusions. By a comparative analysis of the treatment groups, we found that both drugs have a positive effect on patients with psoriasis vulgaris, primarily by regulating the pathways related to platelet activation, aggregation, and blood coagulation. Trial registration: ChiCTR, ChiCTR-TRC-14005185, Registered 8 August 2014, http://www.chictr.org.cn/showproj.aspx?proj=4390

GTPBP2 positively regulates the invasion, migration and proliferation of non-small cell lung cancer

Lung cancer is one of the most common malignant tumors in the world, and the mortality rate ranks first among various malignant tumors. GTP-binding proteins (guanosine 5'-triphosphate-binding proteins, GTPBPs) are a type of protein with signal transduction function, have GTP hydrolase activity, and play an important role in cell signal transmission, cytoskeletal regulation, protein synthesis and other activities. GTPBP2 is one of the members of the G protein superfamily. Research on GTPBP2 is currently focused on human genetics, and its research in tumors has not been reported. First, Western blot and quantitative real-time PCR were used to analyze the expression differences of 12 cases of GTPBP2 in human NSCLC fresh cancer tissues and adjacent tissues. Then we selected 112 cases of NSCLC cancer tissues and 65 adjacent tissues for immunohistochemistry experiments to analyze the relationships between the expression of GTPBP2 and clinical pathological parameters and prognosis, we found that GTPBP2 is highly expressed in NSCLC cancer tissues, and the high expression of GTPBP2 is related to pTNM stage and lymph node metastasis. In addition, after GTPBP2 knockdown, GTPBP2 can promote the proliferation and invasion of NSCLC cell lines by up-regulating RhoC and MMP-9, and up-regulate cyclinD1, CDK4 and c-myc, and down-regulate P27 to promote the invasion of NSCLC cell lines. In addition, GTPBP2 negatively regulates Axin to promote β-catenin expression, thereby activating Wnt/β-catenin signaling, and promoting the occurrence of NSCLC.

MTSS1 inhibits colorectal cancer metastasis by regulating the CXCR4/CXCL12 signaling axis

The liver is the most common site of metastasis for colorectal cancer (CRC). Metastasis suppressor 1 (MTSS1), a potential tumor suppressor gene associated with tumor metastasis, has been reported to play an important role in cancer development. The present study aimed to investigate the effects and underlying mechanisms of MTSS1 on the biological behavior of CRC cells both in vitro and in vivo. A CRC mouse model with a high liver metastatic potential was established by injecting mice with SW1116 cells, and the association between MTSS1 expression levels and the metastatic potential of forming liver metastasis lesions was subsequently analyzed. MTSS1 gain‑ and loss‑of‑function experiments were performed by transfecting the CRC cell lines, SW1116 and DLD‑1, with Plvx‑IRES‑ZsGreen1‑MTSS1 plasmid and short hairpin RNA, respectively. Cell proliferation, migration, invasion and cell cycle distribution were analyzed by MTT, Transwell and flow cytometric assays, respectively. To further determine the underlying mechanisms of MTSS1 in CRC, the expression levels of cell surface chemokine C‑X‑C receptor 4 (CXCR4) and its downstream signaling factors, Rac and cell division cycle 42 (CDC42), were analyzed with or without C‑X‑C motif chemokine ligand 12 (CXCL12) stimulation. The results revealed that as the CRC metastatic potential increased, the expression levels of MTSS1 decreased. The overexpression of MTSS1 exerted an inhibitory effect on cell proliferation, migration and invasion, while the knockdown of MTSS1 exerted the opposite effects in vitro. Flow cytometric analysis and western blot analysis demonstrated that MTSS1 negatively regulated the expression levels of cell surface CXCR4 and its downstream signaling pathway activation. On the whole, the results of the present study indicate that MTSS1 may play an important negative role in CRC metastasis and the underlying mechanisms may involve the downregulation of the CXCR4/CXCL12 signaling axis.

The role of host cell Rab GTPases in influenza A virus infections

Influenza A virus (IAV) is a crucial cause of respiratory infections in humans worldwide. Therefore, studies should clarify adaptation mechanisms of IAV and critical factors of the viral pathogenesis in human hosts. GTPases of the Rab family are the largest branch of the Ras-like small GTPase superfamily, and they regulate almost every step during vesicle-mediated trafficking. Evidence has shown that Rab proteins participate in the lifecycle of IAV. In this mini-review, we outline the regulatory mechanisms of different Rab proteins in the lifecycle of IAV. Understanding the role of Rab proteins in IAV infections is important to develop broad-spectrum host-targeted antiviral strategies.

Nanobody-Based Quantification of GTP-Bound RHO Conformation Reveals RHOA and RHOC Activation Independent from Their Total Expression in Breast Cancer

As key regulators of the actin cytoskeleton, RHO GTPase expression and/or activity are deregulated in tumorigenesis and metastatic progression. Nevertheless, the vast majority of experiments supporting this conclusion was conducted on cell lines but not on human tumor samples that were mostly studied at the expression level only. Up to now, the activity of RHO proteins remains poorly investigated in human tumors. In this article, we present the development of a robust nanobody-based ELISA assay, with a high selectivity that allows an accurate quantification of RHO protein GTP-bound state in the nanomolar range (1 nM; 20 μg/L), not only in cell lines after treatment but also in tumor samples. Of note, we present here a fine analysis of RHOA-like and RAC1 active state in tumor samples with the most comprehensive study of RHOA-GTP and RHOC-GTP levels performed on human breast tumor samples. We revealed increased GTP-bound RHOA and RHOC protein activities in tumors compared to normal tissue counterparts, and demonstrated that the RHO active state and RHO expression are two independent parameters among different breast cancer subtypes. Our results further highlight the regulation of RHO protein activation in tumor samples and the relevance of directly studying RHO GTPase activities involvement in molecular pathways.

Statistical profiling reveals correlations between the cell response to and the primary structure of Rho-GAPs

Rho-GTPase-activating proteins (Rho-GAPs) are essential upstream regulators of the Rho family of GTPases. Currently, it remains unclear if the phenotypic change caused by perturbations to a Rho-GAP is predictable from its amino acid sequence. Here we analyze the relationship between the morphological response of cells to the silencing of Rho-GAPs and their primary structure. For all possible pairs of 57 different Rho-GAPs expressed in MCF10A epithelial cells, the similarity in the Rho-GAP silencing-induced morphological change was quantified and compared to the similarity in the primary structure of the corresponding pairs. We found a distinct correlation between the morphological and sequence similarities in a specific group of RhoA-targeting Rho-GAPs. Thus, the family-wide analysis revealed a common feature shared by the specific Rho-GAPs.

Profiles of alternative splicing events in the diagnosis and prognosis of Gastric Cancer

Background: Gastric cancer (GC) is a heterogeneous disease, and alternative splicing (AS) is a powerful universal transcriptional regulatory mechanism that contributes to the occurrence and development of cancer. However, the systematic analysis of AS events in GC is lacking; therefore, further studies are needed. Methods: Genome-wide analysis of AS events was performed using RNA-Seq data to evaluate the difference between GC and adjacent tissues at the AS level. Prognostic signatures based on differentially expressed alternative splicing (DEAS) events and a correlation network between DEAS and genes were built. Results: We identified 48,141 AS events, of which 2325 showed differential expression patterns. The parental genes before DEAS events play an essential role in regulating GC-related processes such as ribosome (FDR < 0.0001) and thermogenesis (FDR = 0.0002). There were 76 survival-associated DEAS cases. Stratifying patients according to the percent spliced in index value of six types of splicing patterns formed significant Kaplan-Meier curves in the overall survival analysis. A prognostic feature based on DEAS performed well for stratification in patients with GC. Conclusion: The present study will enrich our understanding regarding the distinction of GC and provide a generous amount of biomarkers and potential targets for the treatment of GC.

Effects of isoprenylcysteine carboxyl methyltransferase silencing on the proliferation and apoptosis of tongue squamous cell carcinoma

OBJECTIVES

This study aimed to explore the effects of silencing isoprenylcysteine carboxyl methyltransfe-rase (Icmt) through small interfering RNA (siRNA) interference on the proliferation and apoptosis of tongue squamous cell carcinoma (TSCC).

METHODS

Three siRNA were designed and constructed for the Icmt gene sequence and were then transfected into TSCC cells CAL-27 and SCC-4 to silence Icmt expression. The tested cells were divided as follows: RNA interference groups Icmt-siRNA-1, Icmt-siRNA-2, and Icmt-siRNA-3, negative control group, and blank control group. The transfection efficiency of siRNA was detected by the fluorescent group Cy3-labeled siRNA, and the expression of Icmt mRNA was screened by quantitive real-time polymerase chain reaction (qRT-PCR) selected the experimental group for subsequent experiments. The expression of Icmt, RhoA, Cyclin D1, p21, extracellular regulated protein kinases (ERK), and phospho-extracellular regulated protein kinases (p-ERK) were analyzed by Western blot. The proliferation abilities of TSCC cells were determined by cell counting kit-8 assay. The change in apoptosis was detected by AnnexinV-APC/propidium staining (PI) assay. Cell-cycle analysis was conducted by flow cytometry.

RESULTS

The expression of Icmt mRNA and protein in TSCC cells significantly decreased after Icmt-siRNA transfection (P<0.05). No significant difference in RhoA mRNA and protein expression was detected (P>0.05), but the expression of RhoA membrane protein decreased compared with the negative control group and blank control groups (P<0.05). Cyclin D1 expression decreased, whereas p21 expression significantly increased and the relative expression of ERK protein in the experimental group did not significantly different that in the control group (P>0.05). However, the phosphorylation level of ERK was significantly reduced (P<0.05). The cell cycles of TSCC CAL-27 and SCC-4 were altered in G1/S, cell proliferation activity was inhibited, and apoptosis was induced (P<0.05).

CONCLUSIONS

Silencing Icmt can effectively downregulate its expression in TSCC cells, reduce the RhoA membrane targeting localization and cell proliferation, and induce apoptosis. Thus, Icmt may be a potential gene therapy target for TSCC.

Cellular mitosis predicts vessel stability in a mechanochemical model of sprouting angiogenesis

Angiogenesis, the formation of new vessels, occurs in both developmental and pathological contexts. Prior research has investigated vessel formation to identify cellular phenotypes and dynamics associated with angiogenic disease. One major family of proteins involved in angiogenesis are the Rho GTPases, which govern function related to cellular elongation, migration, and proliferation. Using a mechanochemical model coupling Rho GTPase activity and cellular and intercellular mechanics, we investigate the role of cellular mitosis on sprouting angiogenesis. Mitosis-GTPase synchronization was not a strong predictor of GTPase and thus vessel signaling instability, whereas the location of mitotic events was predicted to alter GTPase cycling instabilities. Our model predicts that middle stalk cells undergoing mitosis introduce irregular dynamics in GTPase cycling and may provide a source of aberrant angiogenesis. We also find that cellular and junctional tension exhibit spatial heterogeneity through the vessel, and that tension feedback, specifically in stalk cells, tends to increase the maximum forces generated in the vessel.

Loss-of-function variants in ARHGEF9 are associated with an X-linked intellectual disability dominant disorder

ARHGEF9 defects lead to an X-linked intellectual disability disorder related to inhibitory synaptic dysfunction. This condition is more frequent in males, with a few affected females reported. Up to now, sequence variants and gross deletions have been identified in males, while only chromosomal aberrations have been reported in affected females who showed a skewed pattern of X-chromosome inactivation (XCI), suggesting an X-linked recessive (XLR) disorder. We report three novel loss-of-function (LoF) variants in ARHGEF9: A de novo synonymous variant affecting splicing (NM_015185.2: c.1056G>A, p.(Lys352=)) in one female; a nonsense variant in another female (c.865C>T, p.(Arg289*)), that is, also present as a somatically mosaic variant in her father, and a de novo nonsense variant in a boy (c.899G>A; p.(Trp300*)). Both females showed a random XCI. Thus, we suggest that missense variants are responsible for an XLR disorder affecting males and that LoF variants, mainly occurring de novo, may be responsible for an X-linked dominant disorder affecting males and females.