Vav proteins maintain epithelial traits in breast cancer cells using miR-200c-dependent and independent mechanisms

Downregulated miRNA-491-3p accelerates colorectal cancer growth by increasing uMtCK expression

Colorectal carcinoma (CRC) is the second most frequent cancer worldwide. MiR-491-3p, a tumor-suppressive microRNA (miRNA, miR), has been revealed to be abnormally expressed in CRC tissues. Meanwhile, up-regulated ubiquitous mitochondrial creatine kinase (uMtCK) contributes to CRC cell proliferation. Here we aim to explore whether aberrant miR-491-3p expression promotes CRC progression through regulating uMtCK. To this end, miR-491-3p and uMtCK levels were assessed in CRC tissues using quantitative real-time PCR (qRT-PCR). The biological roles of miR-491-3p and uMtCK in regulating CRC growth were evaluated using colony formation assay and mouse Xenograft tumour model. We found that miR-491-3p expression was decreased in CRC tissues compared with matched para-cancerous tissues, whereas uMtCK expression was increased. Functionally, miR-491-3p overexpression repressed SW480 cell growth, whereas miR-491-3p depletion accelerated SW620 cell proliferation and growth. Inversely, uMtCK positively regulated CRC cell proliferation. Mechanistically, miR-491-3p post-transcriptionally downregulated uMtCK expression by binding to 3'-UTR of uMtCK. Consequently, restoring uMtCK expression markedly eliminated the role of miR-491-3p in suppressing CRC growth. Collectively, miR-491-3p functions as a tumour suppressor gene by repressing uMtCK, and may be a potential target for CRC treatment.

Vav Proteins in Development of the Brain: A Potential Relationship to the Pathogenesis of Congenital Zika Syndrome?

Zika virus (ZIKV) infection during pregnancy can result in a significant impact on the brain and eye of the developing fetus, termed congenital zika syndrome (CZS). At a morphological level, the main serious presentations of CZS are microcephaly and retinal scarring. At a cellular level, many cell types of the brain may be involved, but primarily neuronal progenitor cells (NPC) and developing neurons. Vav proteins have guanine exchange activity in converting GDP to GTP on proteins such as Rac1, Cdc42 and RhoA to stimulate intracellular signaling pathways. These signaling pathways are known to play important roles in maintaining the polarity and self-renewal of NPC pools by coordinating the formation of adherens junctions with cytoskeletal rearrangements. In developing neurons, these same pathways are adopted to control the formation and growth of neurites and mediate axonal guidance and targeting in the brain and retina. This review describes the role of Vavs in these processes and highlights the points of potential ZIKV interaction, such as (i) the binding and entry of ZIKV in cells via TAM receptors, which may activate Vav/Rac/RhoA signaling; (ii) the functional convergence of ZIKV NS2A with Vav in modulating adherens junctions; (iii) ZIKV NS4A/4B protein effects on PI3K/AKT in a regulatory loop via PPI3 to influence Vav/Rac1 signaling in neurite outgrowth; and (iv) the induction of SOCS1 and USP9X following ZIKV infection to regulate Vav protein degradation or activation, respectively, and impact Vav/Rac/RhoA signaling in NPC and neurons. Experiments to define these interactions will further our understanding of the molecular basis of CZS and potentially other developmental disorders stemming from in utero infections. Additionally, Vav/Rac/RhoA signaling pathways may present tractable targets for therapeutic intervention or molecular rationale for disease severity in CZS.

VAV Proteins as Double Agents in Cancer: Oncogenes with Tumor Suppressor Roles

Simple Summary

The role of the VAV family (comprised of VAV1, VAV2, and VAV3) in proactive pathways involved in cell transformation has been historically assumed. Indeed, the discovery of potential gain-of-function VAV1 mutations in specific tumor subtypes reinforced this functional archetype. Contrary to this paradigm, we demonstrated that VAV1 could unexpectedly act as a tumor suppressor in some in vivo contexts. In this review, we discuss recent findings in the field, where the emerging landscape is one in which GTPases and their regulators, such as VAV proteins, can exhibit tumor suppressor functions.

Abstract

Guanosine nucleotide exchange factors (GEFs) are responsible for catalyzing the transition of small GTPases from the inactive (GDP-bound) to the active (GTP-bound) states. RHO GEFs, including VAV proteins, play essential signaling roles in a wide variety of fundamental cellular processes and in human diseases. Although the most widespread archetype in the field is that RHO GEFs exert proactive functions in cancer, recent studies in mice and humans are providing new insights into the in vivo function of these proteins in cancer. These results suggest a more complex scenario where the role of GEFs is not so clearly defined. For example, VAV1 can unexpectedly play non-catalytic tumor suppressor functions in T-cell acute lymphoblastic leukemia (T-ALL) by controlling the levels of the active form of NOTCH1 (ICN1). This review focuses on emerging work unveiling tumor suppressor roles for these proteins that should prompt a reevaluation of the role of VAV GEF family in tumor biology.

Proteogenomic Workflow Reveals Molecular Phenotypes Related to Breast Cancer Mammographic Appearance

Proteogenomic approaches have enabled the generat̲ion of novel information levels when compared to single omics studies although burdened by extensive experimental efforts. Here, we improved a data-independent acquisition mass spectrometry proteogenomic workflow to reveal distinct molecular features related to mammographic appearances in breast cancer. Our results reveal splicing processes detectable at the protein level and highlight quantitation and pathway complementarity between RNA and protein data. Furthermore, we confirm previously detected enrichments of molecular pathways associated with estrogen receptor-dependent activity and provide novel evidence of epithelial-to-mesenchymal activity in mammography-detected spiculated tumors. Several transcript-protein pairs displayed radically different abundances depending on the overall clinical properties of the tumor. These results demonstrate that there are differentially regulated protein networks in clinically relevant tumor subgroups, which in turn alter both cancer biology and the abundance of biomarker candidates and drug targets.

A Targeted Bioinformatics Assessment of Adrenocortical Carcinoma Reveals Prognostic Implications of GABA System Gene Expression

Adrenocortical carcinoma (ACC) is a rare but deadly cancer for which few treatments exist. Here, we have undertaken a targeted bioinformatics study of The Cancer Genome Atlas (TCGA) ACC dataset focusing on the 30 genes encoding the γ-aminobutyric acid (GABA) system—an under-studied, evolutionarily-conserved system that is an emerging potential player in cancer progression. Our analysis identified a subset of ACC patients whose tumors expressed a distinct GABA system transcriptome. Transcript levels of ABAT (encoding a key GABA shunt enzyme), were upregulated in over 40% of tumors, and this correlated with several favorable clinical outcomes including patient survival; while enrichment and ontology analysis implicated two cancer-related biological pathways involved in metastasis and immune response. The phenotype associated with ABAT upregulation revealed a potential metabolic heterogeneity among ACC tumors associated with enhanced mitochondrial metabolism. Furthermore, many GABA_A receptor subunit-encoding transcripts were expressed, including two (GABRB2 and GABRD) prognostic for patient survival. Transcripts encoding GABA_B receptor subunits and GABA transporters were also ubiquitously expressed. The GABA system transcriptome of ACC tumors is largely mirrored in the ACC NCI-H295R cell line, suggesting that this cell line may be appropriate for future functional studies investigating the role of the GABA system in ACC cell growth phenotypes and metabolism.

VAV2 signaling promotes regenerative proliferation in both cutaneous and head and neck squamous cell carcinoma

Regenerative proliferation capacity and poor differentiation are histological features usually linked to poor prognosis in head and neck squamous cell carcinoma (hnSCC). However, the pathways that regulate them remain ill-characterized. Here, we show that those traits can be triggered by the RHO GTPase activator VAV2 in keratinocytes present in the skin and oral mucosa. VAV2 is also required to maintain those traits in hnSCC patient-derived cells. This function, which is both catalysis- and RHO GTPase-dependent, is mediated by c-Myc- and YAP/TAZ-dependent transcriptomal programs associated with regenerative proliferation and cell undifferentiation, respectively. High levels of VAV2 transcripts and VAV2-regulated gene signatures are both associated with poor hnSCC patient prognosis. These results unveil a druggable pathway linked to the malignancy of specific SCC subtypes.

The Rho signalling pathway is frequently activated in squamous carcinomas. Here, the authors find that the Rho GEF VAV2 is over expressed in both cutaneous and head and neck squamous cell carcinomas and that at the molecular level VAV2 promotes a pro-tumorigenic stem cell-like signalling programme.

Vav2 pharmaco-mimetic mice reveal the therapeutic value and caveats of the catalytic inactivation of a Rho exchange factor

The current paradigm holds that the inhibition of Rho guanosine nucleotide exchange factors (GEFs), the enzymes that stimulate Rho GTPases, can be a valuable therapeutic strategy to treat Rho-dependent tumors. However, formal validation of this idea using in vivo models is still missing. In this context, it is worth remembering that many Rho GEFs can mediate both catalysis-dependent and independent responses, thus raising the possibility that the inhibition of their catalytic activities might not be sufficient per se to block tumorigenic processes. On the other hand, the inhibition of these enzymes can trigger collateral side effects that could preclude the practical implementation of anti-GEF therapies. To address those issues, we have generated mouse models to mimic the effect of the systemic application of an inhibitor for the catalytic activity of the Rho GEF Vav2 at the organismal level. Our results indicate that lowering the catalytic activity of Vav2 below specific thresholds is sufficient to block skin tumor initiation, promotion, and progression. They also reveal that the negative side effects typically induced by the loss of Vav2 can be bypassed depending on the overall level of Vav2 inhibition achieved in vivo. These data underscore the pros and cons of anti-Rho GEF therapies for cancer treatment. They also support the idea that Vav2 could represent a viable drug target.

Identification of a Combined RNA Prognostic Signature in Adenocarcinoma of the Lung

Background

Adenocarcinoma of the lung is a type of non-small cell lung cancer (NSCLC). Clinical outcome is associated with tumor grade, stage, and subtype. This study aimed to identify RNA expression profiles, including long noncoding RNA (lncRNA), microRNA (miRNA), and mRNA, associated with clinical outcome in adenocarcinoma of the lung using bioinformatics data.

Material/Methods

The miRNA and mRNA expression profiles were downloaded from The Cancer Genome Atlas (TCGA) database, and lncRNA expression profiles were downloaded from The Atlas of Noncoding RNAs in Cancer (TANRIC) database. The independent dataset, the Gene Expression Omnibus (GEO) accession dataset, GSE81089, was used. RNA expression profiles were used to identify comprehensive prognostic RNA signatures based on patient survival time.

Results

From 7,704 lncRNAs, 787 miRNAs, and 28,937 mRNAs of 449 patients, four joint RNA molecular signatures were identified, including RP11-909N17.2, RP11-14N7.2 (lncRNAs), MIR139 (miRNA), KLHDC8B (mRNA). The random forest (RF) classifier was used to test the prediction ability of patient survival risk and showed a good predictive accuracy of 71% and also showed a significant difference in overall survival (log-rank P=0.0002; HR, 3.54; 95% CI, 1.74–7.19). The combined RNA signature also showed good performance in the identification of patient survival in the validation and independent datasets.

Conclusions

This study identified four RNA sequences as a prognostic molecular signature in adenocarcinoma of the lung, which may also provide an increased understanding of the molecular mechanisms underlying the pathogenesis of this malignancy.

Epithelial mesenchymal transition and resistance in endocrine-related cancers

Epithelial to mesencyhmal transition (EMT) has a central role in tumor metastasis and progression. EMT is regulated by several growth factors and pro-inflammatory cytokines. The most important role in this regulation could be attributed to transforming growth factor-β (TGF-β). In breast cancer, TGF-β effect on EMT could be potentiated by Fos-related antigen, oncogene HER2, epidermal growth factor, or mitogen-activated protein kinase kinase 5 - extracellular-regulated kinase signaling. Several microRNAs in breast cancer have a considerable role either in potentiation or in suppression of EMT thus acting as oncogenic or tumor suppressive modulators. At present, possibilities to target EMT are discussed but the results of clinical translation are still limited. In prostate cancer, many cellular events are regulated by androgenic hormones. Different experimental results on androgenic stimulation or inhibition of EMT have been reported in the literature. Thus, a possibility that androgen ablation therapy leads to EMT thus facilitating tumor progression has to be discussed. Novel therapy agents, such as the anti-diabetic drug metformin or selective estrogen receptor modulator ormeloxifene were used in pre-clinical studies to inhibit EMT in prostate cancer. Taken together, the results of pre-clinical and clinical studies in breast cancer may be helpful in the process of drug development and identify potential risk during the early stage of that process.

The Vav GEF Family: An Evolutionary and Functional Perspective

Vav proteins play roles as guanosine nucleotide exchange factors for Rho GTPases and signaling adaptors downstream of protein tyrosine kinases. The recent sequencing of the genomes of many species has revealed that this protein family originated in choanozoans, a group of unicellular organisms from which animal metazoans are believed to have originated from. Since then, the Vav family underwent expansions and reductions in its members during the evolutionary transitions that originated the agnates, chondrichthyes, some teleost fish, and some neoaves. Exotic members of the family harboring atypical structural domains can be also found in some invertebrate species. In this review, we will provide a phylogenetic perspective of the evolution of the Vav family. We will also pay attention to the structure, signaling properties, regulatory layers, and functions of Vav proteins in both invertebrate and vertebrate species.