The Rho guanine nucleotide exchange factor P-Rex1 as a potential drug target for cancer metastasis and inflammatory diseases

The Genetic, Pharmacogenomic, and Immune Landscapes Associated with Protein Expression across Human Cancers

Proteomics is a powerful approach that can rapidly enhance our understanding of cancer development. Detailed characterization of the genetic, pharmacogenomic, and immune landscape in relation to protein expression in patients with cancer could provide new insights into the functional roles of proteins in cancer. By taking advantage of the genotype data from The Cancer Genome Atlas and protein expression data from The Cancer Proteome Atlas, we characterized the effects of genetic variants on protein expression across 31 cancer types and identified approximately 100,000 protein quantitative trait loci (pQTL). Among these, over 8000 pQTLs were associated with patient overall survival. Furthermore, characterization of the impact of protein expression on more than 350 imputed anticancer drug responses in patients revealed nearly 230,000 significant associations. In addition, approximately 21,000 significant associations were identified between protein expression and immune cell abundance. Finally, a user-friendly data portal, GPIP (https://hanlaboratory.com/GPIP), was developed featuring multiple modules that enable researchers to explore, visualize, and browse multidimensional data. This detailed analysis reveals the associations between the proteomic landscape and genetic variation, patient outcome, the immune microenvironment, and drug response across cancer types, providing a resource that may offer valuable clinical insights and encourage further functional investigations of proteins in cancer.

SIGNIFICANCE

Comprehensive characterization of the relationship between protein expression and the genetic, pharmacogenomic, and immune landscape of tumors across cancer types provides a foundation for investigating the role of protein expression in cancer development and treatment.

Guanine nucleotide exchange factors for Rho GTPases (RhoGEFs) as oncogenic effectors and strategic therapeutic targets in metastatic cancer

Metastatic cancer cells dynamically adjust their shape to adhere, invade, migrate, and expand to generate secondary tumors. Inherent to these processes is the constant assembly and disassembly of cytoskeletal supramolecular structures. The subcellular places where cytoskeletal polymers are built and reorganized are defined by the activation of Rho GTPases. These molecular switches directly respond to signaling cascades integrated by Rho guanine nucleotide exchange factors (RhoGEFs), which are sophisticated multidomain proteins that control morphological behavior of cancer and stromal cells in response to cell-cell interactions, tumor-secreted factors and actions of oncogenic proteins within the tumor microenvironment. Stromal cells, including fibroblasts, immune and endothelial cells, and even projections of neuronal cells, adjust their shapes and move into growing tumoral masses, building tumor-induced structures that eventually serve as metastatic routes. Here we review the role of RhoGEFs in metastatic cancer. They are highly diverse proteins with common catalytic modules that select among a variety of homologous Rho GTPases enabling them to load GTP, acquiring an active conformation that stimulates effectors controlling actin cytoskeleton remodeling. Therefore, due to their strategic position in oncogenic signaling cascades, and their structural diversity flanking common catalytic modules, RhoGEFs possess unique characteristics that make them conceptual targets of antimetastatic precision therapies. Preclinical proof of concept, demonstrating the antimetastatic effect of inhibiting either expression or activity of βPix (ARHGEF7), P-Rex1, Vav1, ARHGEF17, and Dock1, among others, is emerging.

Transcriptomics and systems network-based molecular mechanism of herbal formula Huosu-Yangwei inhibited gastric cancer in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

The efficacy of the herbal formula Huosu-Yangwei (HSYW) in the treatment of advanced gastric cancer and chronic atrophic gastritis with precancerous lesions has been reported in clinical trials. However, the molecular mechanisms underlying its inhibition of gastric tumor are not well-understood.

AIM OF THE STUDY

Combined with transcriptomics and systems network-based molecular mechanism to explore the potential circRNA-miRNA-mRNA network of HSYW in the treatment of gastric cancer.

MATERIALS AND METHODS

Animal experiments were conducted to investigate the effect of HSYW on tumor growth in vivo. RNA sequencing (RNA-seq) was implemented to identify the differentially expressed (DE) genes. Predictive miRNA targets and mRNA were used to construct circRNA-miRNA-mRNA networks and protein-protein interaction (PPI) networks. Quantitative real-time PCR (qRT-PCR) was utilized to verify the accuracy of the proposed circRNA-miRNA-mRNA networks. Additionally, the differentially expressed target proteins between gastric cancer (GC) and normal patients were assessed using data from the TCGA (The Cancer Genome Atlas) and HPA (The Human Protein Atlas) databases.

RESULTS

We demonstrate HSYW significantly inhibits tumor growth of N87 cell-bearing Balb/c mice. Transcriptomic analysis revealed the existence of 119 differentially expressed (DE) circRNAs and 200 DE mRNAs between HSYW-treated and model mice. By associating predicted circRNA-miRNA pairs and miRNA-mRNA pairs, we constructed a circRNA-miRNA-mRNA (CMM) network. Furthermore, a protein-protein interaction (PPI) network was developed using the differential expressed mRNAs. Consequently, the reconstructed core CMM network and qRT-PCR validation indicated that 4 circRNAs, 5 miRNAs and 6 mRNAs could potentially serve as biomarkers to assess the therapeutic effects of HSYW-treated N87-bearing Balb/c mice. The TCGA and HPA databases also demonstrated that mRNA KLF15 and PREX1 had substantial differences between gastric cancer (GC) and healthy controls.

CONCLUSIONS

By combining the experimental and bioinformatics analysis, this study confirms that the circRNA_00240/hsa-miR-642a-5p/KLF15 and circRNA_07980/hsa-miR-766-3p/PREX1 pathways play critical roles in HSYW-treated gastric cancer.

Gβγ mediates activation of Rho guanine nucleotide exchange factor ARHGEF17 that promotes metastatic lung cancer progression

Metastatic lung cancer is a major cause of death worldwide. Dissemination of cancer cells can be facilitated by various agonists within the tumor microenvironment, including by lysophosphatidic acid (LPA). We postulate that Rho guanine nucleotide exchange factors (RhoGEFs), which integrate signaling cues driving cell migration, are critical effectors in metastatic cancer. Specifically, we addressed the hypothetical role of ARHGEF17, a RhoGEF, as a potential effector of Gβγ in metastatic lung cancer cells responding to LPA. Here, we show that ARHGEF17, originally identified as a tumor endothelial marker, is involved in tumor growth and metastatic dissemination of lung cancer cells in an immunocompetent murine model. Gene expression–based analysis of lung cancer datasets showed that increased levels of ARHGEF17 correlated with reduced survival of patients with advanced-stage tumors. Cellular assays also revealed that this RhoGEF participates in the invasive and migratory responses elicited by Gi protein–coupled LPA receptors via the Gβγ subunit complex. We demonstrate that this signaling heterodimer promoted ARHGEF17 recruitment to the cell periphery and actin fibers. Moreover, Gβγ allosterically activates ARHGEF17 by the removal of inhibitory intramolecular restrictions. Taken together, our results indicate that ARHGEF17 may be a valid potential target in the treatment of metastatic lung cancer.

P-Rex1 Cooperates With TGFβR2 to Drive Lung Fibroblast Migration in Pulmonary Fibrosis

Pulmonary fibrosis is a kind of interstitial lung disease with progressive pulmonary scar formation, leading to irreversible loss of lung functions. The TGF-β1/Smad signaling pathway plays a key role in fibrogenic processes. It is associated with the increased synthesis of extracellular matrix, enhanced proliferation of fibroblasts, and transformation of alveolar epithelial cells into interstitial cells. We investigated P-Rex1, a PIP₃-Gβγ-dependent guanine nucleotide exchange factor (GEF) for Rac, for its potential role in TGF-β1-induced pulmonary fibrosis. A high expression level of P-Rex1 was identified in the lung tissue of patients with pulmonary fibrosis than that from healthy donors. Using the P-Rex1 knockdown and overexpression system, we established a novel player of P-Rex1 in mouse lung fibroblast migration. P-Rex1 contributed to fibrogenic processes in lung fibroblasts by targeting the TGF-β type Ⅱ receptor (TGFβR2). The RNA-seq analysis for expression profiling confirmed the modulation of P-Rex1 in cell migration and the involvement of P-Rex1 in TGF-β1 signaling. These results identified P-Rex1 as a signaling molecule involved in TGF-β1-induced pulmonary fibrosis, suggesting that P-Rex1 may be a potential target for pulmonary fibrosis treatment.

Identification of P-Rex1 in the Regulation of Liver Cancer Cell Proliferation and Migration via HGF/c-Met/Akt Pathway

Background

Rho-GTPases and their activators, guanine nucleotide exchange factors (GEFs), are increasingly being recognized as essential mediators of oncogenic signaling. Although it is known that P-Rex1, a member of the Dbl family of GEFs for the Rac small GTPase, contributes to the migration of cancer cells, its exact role in liver cancer and the underlying mechanisms remain unclear.

Materials and Methods

Public datasets from the Gene Expression Omnibus database (GEO) and clinical liver cancer samples were analyzed to explore the expression of P-Rex1. P-Rex1 knockdown and overexpression cell lines were established using a recombinant lentiviral transfection system. BrdU and colony formation assays were performed to determine cell viability. Migratory capacity was analyzed using a transwell migration assay and an in vitro wound-healing assay. Nude mice bearing subcutaneous xenograft tumors were established to determine the effects of P-Rex1 on tumorigenesis in vivo. The role of P-Rex1 in hepatocarcinogenesis was determined through Western blot and co-immunoprecipitation.

Results

Induced expression of endogenous P-Rex1 was identified in liver cancer tumors when compared with adjacent nonmalignant tissues from clinical data. In response to HGF treatment, P-Rex1-knockdown cells displayed reduced proliferation and migration in vitro as well as reduced xenograft tumor growth in vivo. Overexpression of P-Rex1 promoted liver cancer cell proliferation and migration. P-Rex1 primarily acts as a downstream effector of GPCR signaling. This study demonstrated that downregulation of P-Rex1 led to a significant decrease in the phosphorylation of Akt and Erk1/2 by reducing the phosphorylation of the tyrosine kinase receptor c-Met. Furthermore, a physical association between P-Rex1 and c-Met was observed after HGF treatment, suggesting that P-Rex1 may be involved in the HGF/c-Met signaling pathway.

Conclusion

These results support the role of P-Rex1 as a novel player in liver cancer, which suggest that targeting P-Rex1 may provide a potential strategy for liver cancer treatment.