Increased Rac1 activity and Pak1 overexpression are associated with lymphovascular invasion and lymph node metastasis of upper urinary tract cancer

To explore the risk factors of lymphovascular invasion in patients with upper tract urothelial carcinoma and construct a prediction model

Background and objective

To explore the risk factors and construct a prediction model of the lymphovascular invasion (LVI) in patients with upper tract urothelial carcinoma (UTUC).

Methods

Clinical data of 143 UTUC patients treated in our hospital during Jan. 2010 and Dec. 2022 were retrospectively analyzed. The patients were divided into LVI positive group and LVI negative group according to the postoperative lymphovascular conditions. Kaplan-Meier method was used to evaluate the overall survival (OS) and cancer-specific survival (CSS) of the two groups, and the survival curve was drawn. The correlation between LVI and inclusion indexes was analyzed using univariate and ultivariate. A prediction model was established and receiver operating characteristic (ROC) curve was drawn to analyze the diagnostic value.

Results

The median survival time of LVI positive patients was 78 months (95%CI 44.47-111.53), lower than the 90months (95%CI 72.77-107.23) for LVI negative patients, and the 5-year OS of LVI positive patients was 53.0%, lower than that of LVI negative patients (79.6%). The difference was statistically significant (P=0.005). The 5-year CSS of LVI positive patients was 57.0%, lower than that of LVI negative patients (85.7%, P=0.009). The results of univariate analysis showed that there were statistically significant differences between the two groups (P < 0.05) in exfoliation cytology (P=0.044), hydronephrosis (P=0.015), preoperative fibrinogen level (P=0.003), lymph node status (P=0.014), pathological stage (P=0.001) and grade (P=0.047). Multivariate Logistic regression analysis showed that hydronephrosis (P=0.022), pathological stage (P < 0.001), lymph node status (P=0.025) and fibrinogen level (P=0.019) were independent factors influencing the occurrence of lymphovascular invasion, and the combination of four indexes above was better than any single index. the ROC curve showed that the area under the curve (AUC) of postoperative LVI was the largest when combined with the four predictors, and the AUC was 0.833 (95%CI 0.759-0.907). When the Youden index was 0.594, the sensitivity was 81.1%, and the specificity was 78.3%.

Conclusion

Lymphovascular invasion is related to hydronephrosis, pathological stage, lymph node condition and fibrinogen level. Patients with preoperative hydronephrosis, high pathological stage, lymph node metastasis and high fibrinogen level were at higher risk of lymphovascular invasion.

Modulating PAK1: Accessory Proteins as Promising Therapeutic Targets

The p21-activated kinase (PAK1), a serine/threonine protein kinase, is critical in regulating various cellular processes, including muscle contraction, neutrophil chemotaxis, neuronal polarization, and endothelial barrier function. Aberrant PAK1 activity has been implicated in the progression of several human diseases, including cancer, heart disease, and neurological disorders. Increased PAK1 expression is often associated with poor clinical prognosis, invasive tumor characteristics, and therapeutic resistance. Despite its importance, the cellular mechanisms that modulate PAK1 function remain poorly understood. Accessory proteins, essential for the precise assembly and temporal regulation of signaling pathways, offer unique advantages as therapeutic targets. Unlike core signaling components, these modulators can attenuate aberrant signaling without completely abolishing it, potentially restoring signaling to physiological levels. This review highlights PAK1 accessory proteins as promising and novel therapeutic targets, opening new horizons for disease treatment.

RAC1-Amplified and RAC1-A159V Hotspot-Mutated Head and Neck Cancer Sensitive to the Rac Inhibitor EHop-016 In Vivo: A Proof-of-Concept Study

Objective:RAC1 aberrations in head and neck squamous cell carcinoma (HNSCC) remain clinically inactionable today. Methods: Here, we investigated the clinical significance and potential druggability of RAC1 genomic aberrations in HNSCC. Results: Notably, HPV(-)HNSCC patients bearing the unique HNSCC-prevalent RAC1-A159V hotspot mutation, P29S hotspot and G-box domain mutations, and RAC1 copy number increases all displayed dismal overall survival (TCGA-HNSCC). Here, we demonstrated that all five HNSCC patient-relevant RAC1 aberrations tested (A159V and P29S hotspot mutations, K116N, G15S, and N39S) could significantly drive HNSCC tumoroid growth and/invasion, with A159V, P29S, and K116N mutants being the most potent drivers. Interestingly, transcriptomics analyses revealed that RAC1 mutations and copy increase could both drive PI3K pathway activation, with the A159V mutant associated with the prominent intra-tumoral upregulation of phospho-RPS6(Ser235/236) in patient tumors. Importantly, proof-of-principle Rac targeting with EHop-016 resulted in remarkable antitumor activity in vivo against RAC1-A159V-mutated and RAC1-amplified HNSCC patient-derived xenografts (PDXs) and/engineered models. Lastly, melanoma and endometrial xenograft models bearing endogenous RAC1-amplification and RAC1-A159V mutation were also sensitive to EHop-016 targeting. Conclusions: In principle, RAC1 genomic aberrations in HNSCC can be potentially harnessed for precision drugging.

Lymph Node Dissection in Upper Tract Urothelial Carcinoma: Current Status and Future Perspectives

PURPOSE OF REVIEW

This narrative review aims to evaluate the role of lymph node dissection (LND) in upper tract urothelial carcinoma (UTUC) and its implications for staging and management outcomes, as well as future perspectives.

RECENT FINDINGS

Multiple studies have demonstrated the limitations of conventional imaging techniques in accurately localizing lymph node metastasis (LNM) in UTUC. While 18F-fluorodeoxyglucose positron emission tomography with computed tomography (18FDG-PET/CT) shows promise for preoperative LNM detection, its specificity is low. Alternative methods such as choline PET/CT and sentinel lymph node detection are under consideration but require further investigation. Additionally, various preoperative factors associated with LNM hold potential for predicting nodal involvement, thereby improving nodal staging and oncologic outcomes of LND. Several surgical approaches, including segmental ureterectomy and robot-assisted nephroureterectomy, provide a possibility for LND, while minimizing morbidity. LND remains the primary nodal staging tool for UTUC, but its therapeutic benefit is still uncertain. Advances in imaging techniques and preoperative risk assessment show promise in improving LNM detection. Further research and multi-center studies are needed to comprehensively assess the advantages and limitations of LND in UTUC, as well as the long-term outcomes of alternative staging and treatment strategies.

Activation-induced deaminase expression defines mature B cell lymphoma in the mouse

Germinal centers (GCs) are the sites of secondary antibody diversification and underlie the mechanism of action of many vaccination strategies. Activation-induced deaminase (AID) triggers secondary antibody diversification through the introduction of somatic changes in immunoglobulin genes which lead to the generation of antibodies of higher affinity and more specialized effector functions. However, AID can also target other genomic regions, giving rise to mutations and chromosome translocations with oncogenic potential. Many human lymphomas originate from mature B cells that have undergone the GC reaction, such as the diffuse large B cell lymphoma, the follicular lymphoma and Burkitt lymphoma, and carry chromosome translocations. Mature B cell lymphomagenesis has been modeled in the mouse by the genetic introduction of chromosome translocations. Here, we present an in-depth characterization of one such model, λ-MYC mice. We found that young pre-tumor stage mice had a prominent block in early B cell differentiation that resulted in the generation of very aggressive tumors lacking surface B cell receptor (BCR) expression, indicating that a large fraction of tumors in λ-MYC mice arise from B cell precursors rather than from mature B cells. Further, we assessed the contribution of AID to B cell lymphomagenesis in λ-MYC mice by using a genetic tracer of historical AID expression. Only a fraction of tumors contained cells of GC origin as defined by AID expression. AID-experienced tumors associated with longer survival and resembled mature B cell lymphomas. Thus, AID expression defines Burkitt lymphomagenesis in λ-MYC mice.

Rac1 activation in oral squamous cell carcinoma as a predictive factor associated with lymph node metastasis

OBJECTIVES

Secondary lymph node metastasis (SLNM) indicates a poor prognosis, and limiting it can improve the survival rate in early-stage tongue squamous cell carcinoma (TSCC). Many factors have been identified as predictors of SLNM; however, there is no unified view. Ras-related C3 botulinum toxin substrate 1 (Rac1) was found to be a promoter of the epithelial-mesenchymal transition (EMT) and is also attracting attention as a new therapeutic target. This study aims to investigate the role of Rac1 in metastasis and its relationship with pathological findings in early-stage TSCC.

MATERIALS AND METHODS

Rac1 expression levels of 69 cases of stage I/II TSCC specimens and their association with clinicopathological characteristics were evaluated by immunohistochemical staining. The role of Rac1 in oral squamous cell carcinoma (OSCC) was examined after Rac1 in OSCC cell lines was silenced in vitro.

RESULTS

High Rac1 expression was significantly associated with the depth of invasion (DOI), tumor budding (TB), vascular invasion, and SLNM (p < 0.05). Univariate analyses revealed that Rac1 expression, DOI, and TB were factors significantly associated with SLNM (p < 0.05). Moreover, our multivariate analysis suggested that Rac1 expression was the only independent determinant of SLNM. An in vitro study revealed that Rac1 downregulation tended to decrease cell migration and proliferation.

CONCLUSION

Rac1 was suggested to be an important factor in the metastasis of OSCC, and it could be useful as a predictor of SLNM.

Analysis of PPI networks of transcriptomic expression identifies hub genes associated with Newcastle disease virus persistent infection in bladder cancer

Bladder cancer cells can acquire persistent infection of oncolytic Newcastle disease virus (NDV) but the molecular mechanism(s) remain unelucidated. This poses a major barrier to the effective clinical translation of oncolytic NDV virotherapy of cancers. To improve our understanding of the molecular mechanism(s) associated with the development of NDV persistent infection in bladder cancer, we used mRNA expression profiles of persistently infected bladder cancer cells to construct PPI networks. Based on paths and modules in the PPI network, the bridges were found mainly in the upregulated mRNA-pathways of p53 signalling, ECM-receptor interaction, and TGF-beta signalling and downregulated mRNA-pathways of antigen processing and presentation, protein processing in endoplasmic reticulum, completement and coagulation cascades in persistent TCCSUPPi cells. In persistent EJ28Pi cells, connections were identified mainly through upregulated mRNA-pathways of renal carcinoma, viral carcinogenesis, Ras signalling and cell cycle and the downregulated mRNA-pathways of Wnt signalling, HTLV-I infection and pathways in cancers. These connections were mainly dependent on RPL8-HSPA1A/HSPA4 in TCCSUPPi cells and EP300, PTPN11, RAC1-TP53, SP1, CCND1 and XPO1 in EJ28Pi cells. Oncomine validation showed that the top hub genes identified in the networks that include RPL8, THBS1, F2 from TCCSUPPi and TP53 and RAC1 from EJ28Pi are involved in the development and progression of bladder cancer. Protein-drug interaction networks identified several putative drug targets that could be used to disrupt the linkages between the modules and prevent bladder cancer cells from acquiring NDV persistent infection. This novel PPI network analysis of differentially expressed mRNAs of NDV persistently infected bladder cancer cell lines provide an insight into the molecular mechanisms of NDV persistency of infection in bladder cancers and the future screening of drugs that can be used together with NDV to enhance its oncolytic efficacy.

Targeting P21-Activated Kinase-1 for Metastatic Prostate Cancer

Metastatic prostate cancer (mPCa) has limited therapeutic options and a high mortality rate. The p21-activated kinase (PAK) family of proteins is important in cell survival, proliferation, and motility in physiology, and pathologies such as infectious, inflammatory, vascular, and neurological diseases as well as cancers. Group-I PAKs (PAK1, PAK2, and PAK3) are involved in the regulation of actin dynamics and thus are integral for cell morphology, adhesion to the extracellular matrix, and cell motility. They also play prominent roles in cell survival and proliferation. These properties make group-I PAKs a potentially important target for cancer therapy. In contrast to normal prostate and prostatic epithelial cells, group-I PAKs are highly expressed in mPCA and PCa tissue. Importantly, the expression of group-I PAKs is proportional to the Gleason score of the patients. While several compounds have been identified that target group-I PAKs and these are active in cells and mice, and while some inhibitors have entered human trials, as of yet, none have been FDA-approved. Probable reasons for this lack of translation include issues related to selectivity, specificity, stability, and efficacy resulting in side effects and/or lack of efficacy. In the current review, we describe the pathophysiology and current treatment guidelines of PCa, present group-I PAKs as a potential druggable target to treat mPCa patients, and discuss the various ATP-competitive and allosteric inhibitors of PAKs. We also discuss the development and testing of a nanotechnology-based therapeutic formulation of group-I PAK inhibitors and its significant potential advantages as a novel, selective, stable, and efficacious mPCa therapeutic over other PCa therapeutics in the pipeline.

Rac1 as a Target to Treat Dysfunctions and Cancer of the Bladder

Bladder pathologies, very common in the aged population, have a considerable negative impact on quality of life. Novel targets are needed to design drugs and combinations to treat diseases such as overactive bladder and bladder cancers. A promising new target is the ubiquitous Rho GTPase Rac1, frequently dysregulated and overexpressed in bladder pathologies. We have analyzed the roles of Rac1 in different bladder pathologies, including bacterial infections, diabetes-induced bladder dysfunctions and bladder cancers. The contribution of the Rac1 protein to tumorigenesis, tumor progression, epithelial-mesenchymal transition of bladder cancer cells and their metastasis has been analyzed. Small molecules selectively targeting Rac1 have been discovered or designed, and two of them—NSC23766 and EHT 1864—have revealed activities against bladder cancer. Their mode of interaction with Rac1, at the GTP binding site or the guanine nucleotide exchange factors (GEF) interaction site, is discussed. Our analysis underlines the possibility of targeting Rac1 with small molecules with the objective to combat bladder dysfunctions and to reduce lower urinary tract symptoms. Finally, the interest of a Rac1 inhibitor to treat advanced chemoresistance prostate cancer, while reducing the risk of associated bladder dysfunction, is discussed. There is hope for a better management of bladder pathologies via Rac1-targeted approaches.

The Use of Nanomedicine to Target Signaling by the PAK Kinases for Disease Treatment

P21-activated kinases (PAKs) are serine/threonine kinases involved in the regulation of cell survival, proliferation, inhibition of apoptosis, and the regulation of cell morphology. Some members of the PAK family are highly expressed in several types of cancer, and they have also been implicated in several other medical disorders. They are thus considered to be good targets for treatment of cancer and other diseases. Although there are several inhibitors of the PAKs, the utility of some of these inhibitors is reduced for several reasons, including limited metabolic stability. One way to overcome this problem is the use of nanoparticles, which have the potential to increase drug delivery. The overall goals of this review are to describe the roles for PAK kinases in cell signaling and disease, and to describe how the use of nanomedicine is a promising new method for administering PAK inhibitors for the purpose of disease treatment and research. We discuss some of the basic mechanisms behind nanomedicine technology, and we then describe how these techniques are being used to package and deliver PAK inhibitors.

Anticancer Potential of Aguerin B, a Sesquiterpene Lactone Isolated from Centaurea behen in Metastatic Breast Cancer Cells

BACKGROUND

Breast carcinoma is a malignant disease that represents the most common non-skin malignancy and a chief reason of cancer death in women. Large interest is growing in the use of natural products for cancer treatment, especially with goal of suppression angiogenesis, tumor cell growth, motility, as well as invasion and metastasis with low/no toxicity. It is evident from recent patents on the anticancer properties of sesquiterpene lactones such as parthenolide.

OBJECTIVE

In this study, using MDA-MB-231 cells of a human breast adenocarcinoma, the effects of aguerin B, as a natural sesquiterpene lactone, has been evaluated, in terms of the expression of metastatic-related genes (Pak-1, Rac-1 and HIF-1α).

METHODS

Cytotoxicity of aguerin B was tested toward MDA-MB-231 breast tumor cells using MTT. Scratch assay was accomplished to evaluate the tumor cell invasion. To understand the underlying molecular basis, the mRNA expressions were evaluated by real time PCR.

RESULTS

It was found that aguerin B significantly inhibited human breast cancer cell growth in vitro (IC50 = 2μg/mL) and this effect was accompanied with a persuasive suppression on metastasis. Our results showed that aguerin B in IC50 concentration down-regulated Rac-1, Pak-1, Hif-1α and Zeb-1 transcriptional levels.

CONCLUSION

Taken together, this study demonstrated that aguerin B possessed potential anti-metastatic effect, suggesting that it may consider as a potential multi target bio compound for treatment of breast metastatic carcinoma.

Elevated expression of B7 homolog 4 is associated with disease progression in upper urinary tract urothelial carcinoma

Background

B7 homolog 4 (B7-H4) is a negative regulator of immune responses, but its immunoregulatory role in the tumor microenvironment of upper urinary tract urothelial carcinoma (UTUC) remains unclear.

Methods

We measured the immunohistochemical expression of B7-H4, CD8 and T cell intracellular antigen 1 (TIA-1), a marker of activated CD8, in 133 patients with UTUC who underwent nephroureterectomy. We also studied the relationship between B7-H4, CD8 and TIA-1 expression and clinicopathological characteristics.

Results

B7-H4 was mainly expressed on the surface in tumor cells, while CD8 and TIA-1 were often expressed in tumor-infiltrating lymphocytes. Elevated expression of B7-H4 in tumor cells was associated with a poorer histological grade, higher pT stage, regional lymph node metastasis, lymphovascular invasion, poorer response of recurrent metastatic lesions to systemic chemotherapy and shorter overall survival. Expression of CD-8 or TIA-1 alone did not correlate directly with clinicopathological characteristics, but among the patients with higher B7-H4 expression in the primary tumors, those with higher CD8 or TIA-1 expression had a better response to systemic chemotherapy, and longer survival, than these with lower CD8 or TIA-1 expression. Cox multivariate regression analysis revealed that higher expression of B7-H4 was associated with shorter overall survival.

Conclusions

These findings suggest that B7-H4 expression in the tumor microenvironment influences the progression of UTUC through cancer immunity and metabolic activity. Tumor cell-associated B7-H4 might be a potential target for cancer immunotherapies.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00262-021-03011-5.

Rac1, A Potential Target for Tumor Therapy

RAS-related C3 botulinum toxin substrate 1 (Rac.1) is one of the important members of Rho GTPases. It is well known that Rac1 is a cytoskeleton regulation protein that regulates cell adhesion, morphology, and movement. Rac1 is highly expressed in different types of tumors, which is related to poor prognosis. Studies have shown that Rac1 not only participates in the tumor cell cycle, apoptosis, proliferation, invasion, migration and angiogenesis, but also participates in the regulation of tumor stem cell, thus promoting the occurrence of tumors. Rac1 also plays a key role in anti-tumor therapy and participates in immune escape mediated by the tumor microenvironment. In addition, the good prospects of Rac1 inhibitors in cancer prevention and treatment are exciting. Therefore, Rac1 is considered as a potential target for the prevention and treatment of cancer. The necessity and importance of Rac1 are obvious, but it still needs further study.

Dramatic Responses of Recurrent Upper Urinary Tract Urothelial Carcinoma Harboring FGFR3 and TP53 Activating Mutations to Pembrolizumab in Combination with Erdafitinib: A Case Report

Background

Upper tract urothelial carcinoma (UTUC) has a high recurrence rate and is likely refractory to systemic chemotherapy. The long-term outcomes and responses to immunotherapy and retreatment regimen after tumor recurrence for such cases had not yet been well-documented.

Case Presentation

Here we report a unique case of long-term follow-up with a 67-year-old woman, who was diagnosed with advanced UTUC, received radical nephroureterectomy with bladder cuff, and was refractory to chemotherapy with cisplatin and gemcitabine. Positive PD-L1 expression and somatic mutation of Ser249Cys in FGFR3 were identified in the tumor tissue. The patient then received pembrolizumab monotherapy and achieved complete response (CR) after 6 cycles of treatment. She discontinued pembrolizumab treatment thereafter but remained in CR for 3 years and 7 months until the recurrence of tumor in the right mid-ureter. The patient was then retreated with a combination of pembrolizumab and erdafitinib, and achieved CR again after the third cycle of treatment.

Conclusion

We reported here a rare case of UTUC with concurrent pathogenic mutations in FGFR3 and TP53 with positive PD-L1 expression. The patient archived exceptional therapeutic responses to PD-1 blockade treatment and retreatment with combination of pembrolizumab and erdafitinib. Our results provide new insight into the duration of immunotherapy and the retreatment strategy after tumor recurrence based on individual genomic profiles.

Rac Family Small GTPase 3 Correlates with Progression and Poor Prognosis in Bladder Cancer

Bladder cancer (BC) is a common genitourinary malignancy worldwide. However, the molecular pathogenesis of BC remains unclear. The current study conducted bioinformatic analyses to discover key genes involved in BC progression. A total of 375 differentially expressed genes (DEGs) were screened in the GEO database and The Cancer Genome Atlas (TCGA) database, which were further evaluated by the core level in the protein-protein interaction network. RAC3 (Rac family small GTPase 3), one of the top hub genes, was focused on for its gene expression and prognostic value in BC. Immunohistochemical assays indicated elevated RAC3 levels in BC tissues compared with normal tissues. Overexpression of RAC3 expression was closely associated with poor differentiation (p = 0.035), advanced TNM stage (p = 0.014), lymph metastasis (p = 0.033), and recurrence (p < 0.001). Kaplan-Meier and Cox proportional hazards analyses demonstrated that high RAC3 expression indicated poor survival of BC patients, which could serve as an independent prognostic factor for overall survival (HR = 3.159, p = 0.023) and disease-free survival (HR = 4.633, p = 0.002). Moreover, bioinformatic analyses indicated that RAC3 might be correlated with malignant phenotypes and immune infiltration of BC. Taken together, RAC3 could be a novel prognostic biomarker for BC.

HDAC6 promotes growth, migration/invasion, and self-renewal of rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is a devastating pediatric sarcoma. The survival outcomes remain poor for patients with relapsed or metastatic disease. Effective targeted therapy is lacking due to our limited knowledge of the underlying cellular and molecular mechanisms leading to disease progression. In this study, we used functional assays in vitro and in vivo (zebrafish and xenograft mouse models) to demonstrate the crucial role of HDAC6, a cytoplasmic histone deacetylase, in driving RMS tumor growth, self-renewal, and migration/invasion. Treatment with HDAC6-selective inhibitors recapitulates the HDAC6 loss-of-function phenotypes. HDAC6 regulates cytoskeletal dynamics to promote tumor cell migration and invasion. RAC1, a Rho family GTPase, is an essential mediator of HDAC6 function, and is necessary and sufficient for RMS cell migration and invasion. High expression of RAC1 correlates with poor clinical prognosis in RMS patients. Targeting the HDAC6-RAC1 axis represents a promising therapeutic option for improving survival outcomes of RMS patients.

Effect of increased expression of both ras-related C3 botulinum toxin substrate 1 and p21-activated kinase 1 in patients with N0M0 upper urinary tract urothelial carcinoma and cancer-free surgical margins

BACKGROUND

As a member of the Rho small guanosine triphosphatase family, ras-related C3 botulinum toxin substrate 1 (RAC1) interacts with various specific effectors, and p21-activated kinase 1 (PAK1), which has a role in both carcinogenesis and cellular invasion, binds to RAC1, after which activated PAK1 regulates cellular functions. There have been few reports about the simultaneous analysis of RAC1 and its downstream effector PAK1 in upper urinary tract urothelial carcinoma (UTUC). We assessed the expressions of both RAC1 and PAK1 and evaluated their association with clinicopathological parameters.

METHODS

Immunohistochemical studies of RAC1 or PAK1 were performed with specimens from 104 patients with N0M0 UTUC and cancer-free surgical margins. Correlation of the positive expression of RAC1 or PAK1 or both with clinicopathological parameters was evaluated.

RESULTS

A hazard model showed that the presence of mixed histologic features and moderate or strong positive expression of both RAC1 and PAK1 were independent factors for shortened disease-specific survival time (Ps = 0.041 and 0.016, respectively), and another hazard model revealed that only moderate or strong positive expression of both RAC1 and PAK1 was an independent factor for shortened recurrence-free survival time in the multivariate analysis (P = 0.036). Neither moderate or strong positive expression of RAC1 alone nor moderate or strong positive expression of PAK1 alone was an independent factor for a worse rate of disease-specific or recurrence-free survival in multivariate analysis.

CONCLUSIONS

Patients with N0M0 UTUC, cancer-free surgical margins and moderate or strong positive expression of both RAC1 and PAK1 should be carefully monitored after surgery.

Rac1 activation in human breast carcinoma as a prognostic factor associated with therapeutic resistance

BACKGROUND

RAS-related C3 botulinus toxin substrate 1 (Rac1) is a molecular switch fluctuating between GDP-bound inactive form (Rac1-GDP) and GTP-bound active form (Rac1-GTP) and involved in diverse function in both normal and malignant cells such as breast carcinoma cells. Although several studies have demonstrated immunolocalization of Rac1 protein in human breast carcinoma tissues, activation status of Rac1 still remains to be elucidated.

METHODS

We immunolocalized active form of Rac1 (Rac1-GTP) as well as total Rac1 using antibody specific for them in 115 invasive breast carcinoma tissues and correlated with clinicopathological parameters and clinical outcomes.

RESULTS

Rac1-GTP was frequently immunolocalized in the cytoplasm or cell membrane of breast carcinoma cells and it was positively correlated with Ki-67 labeling index and total Rac1 while negatively correlated with progesterone receptor. On the other hand, immunohistochemical Rac1-GTP status was significantly correlated with increased risk of recurrence and breast cancer-specific mortality of breast cancer patients and multivariate analyses did demonstrate Rac1-GTP as an independent worse prognostic factor for both disease-free and breast cancer-specific survival. In addition, Rac1-GTP was still correlated with worse prognosis in the patients who had received adjuvant chemotherapy or endocrine therapy.

CONCLUSION

These findings suggested Rac1 activation played pivotal roles in the progression and therapeutic resistance of breast cancers and Rac1 might be an important therapeutic target for improvement of the therapy for breast cancer patients.

Computational and in vitro Pharmacodynamics Characterization of 1A-116 Rac1 Inhibitor: Relevance of Trp56 in Its Biological Activity

In the last years, the development of new drugs in oncology has evolved notably. In particular, drug development has shifted from empirical screening of active cytotoxic compounds to molecularly targeted drugs blocking specific biologic pathways that drive cancer progression and metastasis. Using a rational design approach, our group has developed 1A-116 as a promising Rac1 inhibitor, with antitumoral and antimetastatic effects in several types of cancer. Rac1 is over activated in a wide range of tumor types and and it is one of the most studied proteins of the Rho GTPase family. Its role in actin cytoskeleton reorganization has effects on endocytosis, vesicular trafficking, cell cycle progression and cellular migration. In this context, the regulatory activity of Rac1 affects several key processes in the course of the cancer including invasion and metastasis. The purpose of this preclinical study was to focus on the mode of action of 1A-116, conducting an interdisciplinary approach with in silico bioinformatics tools and in vitro assays. Here, we demonstrate that the tryptophan 56 residue is necessary for the inhibitory effects of 1A-116 since this compound interferes with protein-protein interactions (PPI) of Rac1GTPase involving several GEF activators. 1A-116 is also able to inhibit the oncogenic Rac1^P29S mutant protein, one of the oncogenic drivers found in sun-exposed melanoma. It also inhibits numerous Rac1-regulated cellular processes such as membrane ruffling and lamellipodia formation. These results deepen our knowledge of 1A-116 inhibition of Rac1 and its biological impact on cancer progression. They also represent a good example of how in silico analyses represent a valuable approach for drug development.

Differential roles and activation of mammalian target of rapamycin complexes 1 and 2 during cell migration in prostate cancer cells

BACKGROUND

Mammalian target of rapamycin (mTOR) is a downstream substrate activated by PI3K/AKT pathway and it is essential for cell migration. It exists as two complexes: mTORC1 and mTORC2. mTORC1 is known to be regulated by active AKT, but the activation of mTORC2 is poorly understood. In this study, we investigated the roles and differential activation of the two mTOR complexes during cell migration in prostate cancer cells.

METHODS

We used small interfering RNA to silence the expression of Rac1 and the main components of mTOR complexes (regulatory associated protein of mTOR [RAPTOR] and rapamycin-insensitive companion of mTOR [RICTOR]) in LNCaP, DU145, and PC3 prostate cancer cell lines. We performed transwell migration assay to evaluate the migratory capability of the cells, and Western blot analysis to study the activation levels of mTOR complexes.

RESULTS

Specific knockdown of RAPTOR and RICTOR caused a decrease of cell migration, suggesting their essential role in prostate cancer cell movement. Furthermore, epidermal growth factor (EGF) treatments induced the activation of both the mTOR complexes. Lack of Rac1 activity in prostate cancer cells blocked EGF-induced activation of mTORC2, but had no effect on mTORC1 activation. Furthermore, the overexpression of constitutively active Rac1 resulted in significant increase in cell migration and activation of mTORC2 in PC3 cells, but had no effect on mTORC1 activation. Active Rac1 was localized in the plasma membrane and was found to be in a protein complex, with RICTOR, but not RAPTOR.

CONCLUSION

We suggest that EGF-induced activation of Rac1 causes the activation of mTORC2 via RICTOR. This mechanism plays a critical role in prostate cancer cell migration.

Association of cancer progression with elevated expression of programmed cell death protein 1 ligand 1 by upper tract urothelial carcinoma and increased tumor-infiltrating lymphocyte density

Background

Increased expression of programmed cell death 1 ligand 1 (PD-L1) by tumor cells is thought to be a mechanism through which solid cancers promote immune tolerance. However, the association between PD-L1 expression and the prognosis of upper urinary tract urothelial carcinoma (UTUC) remains unknown.

Methods

We examined immunohistochemical PD-L1 expression and the tumor-infiltrating lymphocyte density (TILD) in 79 patients with UTUC who underwent nephroureterectomy. We classified the tumors into four types based on the combination of PD-L1 expression and TILD, and studied the clinicopathological characteristics of these four tumor types.

Results

Elevated expression of PD-L1 by tumor cells and a higher TILD were associated with a worse histological grade, higher pT stage, and higher peripheral blood neutrophil-to-lymphocyte ratio. Elevated expression of PD-L1 by tumor cells, a higher TILD, and type I, III, or IV tumors with elevated expression of either PD-L1 or TILD showed a positive correlation with poorer differentiation and local invasion. These three variables were associated with shorter progression-free survival and overall survival in univariate analysis, but only the latter was an independent determinant according to multivariate analysis. The patients who had type II tumors with lower PD-L1 expression and a lower TILD showed more favorable survival than the other three groups.

Conclusions

These findings suggest that PD-L1 expression and TILs in the tumor microenvironment influence the progression of UTUC. Accordingly, it is important to understand the immunologic characteristics of the tumor microenvironment to develop more effective treatment strategies for this cancer.

Electronic supplementary material

The online version of this article (10.1007/s00262-020-02499-7) contains supplementary material, which is available to authorized users.

Effect of PAK Inhibition on Cell Mechanics Depends on Rac1

Besides biochemical and molecular regulation, the migration and invasion of cells is controlled by the environmental mechanics and cellular mechanics. Hence, the mechanical phenotype of cells, such as fibroblasts, seems to be crucial for the migratory capacity in confined 3D extracellular matrices. Recently, we have shown that the migratory and invasive capacity of mouse embryonic fibroblasts depends on the expression of the Rho-GTPase Rac1, similarly it has been demonstrated that the Rho-GTPase Cdc42 affects cell motility. The p21-activated kinase (PAK) is an effector down-stream target of both Rho-GTPases Rac1 and Cdc42, and it can activate via the LIM kinase-1 its down-stream target cofilin and subsequently support the cell migration and invasion through the polymerization of actin filaments. Since Rac1 deficient cells become mechanically softer than controls, we investigated the effect of group I PAKs and PAK1 inhibition on cell mechanics in the presence and absence of Rac1. Therefore, we determined whether mouse embryonic fibroblasts, in which Rac1 was knocked-out, and control cells, displayed cell mechanical alterations after treatment with group I PAKs or PAK1 inhibitors using a magnetic tweezer (adhesive cell state) and an optical cell stretcher (non-adhesive cell state). In fact, we found that group I PAKs and Pak1 inhibition decreased the stiffness and the Young’s modulus of fibroblasts in the presence of Rac1 independent of their adhesive state. However, in the absence of Rac1 the effect was abolished in the adhesive cell state for both inhibitors and in their non-adhesive state, the effect was abolished for the FRAX597 inhibitor, but not for the IPA3 inhibitor. The migration and invasion were additionally reduced by both PAK inhibitors in the presence of Rac1. In the absence of Rac1, only FRAX597 inhibitor reduced their invasiveness, whereas IPA3 had no effect. These findings indicate that group I PAKs and PAK1 inhibition is solely possible in the presence of Rac1 highlighting Rac1/PAK I (PAK1, 2, and 3) as major players in cell mechanics.

Computational Prediction of Hot Spots and Binding Site of Inhibitor NSC23766 on Rac1 Binding With Tiam1

Rac1 is a small signaling protein, which belongs to the Rho subfamily of Ras superfamily. It is activated by binding GTP and inactivated by exchanging GDP for GTP. The ability of nucleotide exchange depends on guanine nucleotide exchange factors (GEFs) family proteins. T-lymphoma invasion and metastasis factor 1 (Tiam1) is a member of GEFs. Rac1 participates in multiple signaling pathways and regulates various cellular events by interacting with GEFs. Particularly, it is involved in the development and progression of various kinds of tumors. In this paper, we have studied the detailed interaction between Rac1 and Tiam1. Seven residues on Rac1 are predicted to be important for the interaction with Tiam1, i.e. E31, Y32, D38, N39, Y64, D65 and W56. All these residues are located on the switch 1 and 2 domains which are the interface between Rac1 and Tiam1, except W56. In addition, we analyzed how inhibitor NSC23766 interacts with Rac1. Our docking results show that NSC23766 binds to the same region as Tiam1. Several residues, i.e. F37, D38, N39, W56, Y64, L67, L70 and S71, contribute much to binding free energy. These findings are very useful for the structure-based design of inhibitors toward Rac1.

Orai1 Promotes Osteosarcoma Metastasis by Activating the Ras-Rac1-WAVE2 Signaling Pathway

Background

The purpose of this study was to investigate whether Orai1 plays a role in the metastasis of osteosarcoma.

Material/Methods

The expression of Orai1 was silenced by small interfering RNAs against Orai1 (Orai1 siRNA) in osteosarcoma MG-63 cells. Various experiments were carried out to detect the changes in migration, invasion, and adhesion ability of these osteosarcoma cells. Furthermore, the activity of Rac1, Wave2, and Ras was detected using Western blot analysis. Moreover, the Rac1 and Ras inhibitors were used to confirm whether the Ras-Rac1-WAVE2 signaling pathway was involved in osteosarcoma metastasis promoted by Orai1.

Results

We found that the migration, invasion, and adhesion ability of MG-63 cells were significantly reduced after silencing Orai1 expression (p<0.05). Moreover, the activity of the Rac1-WAVE2 signaling pathway was significantly inhibited after silencing of Orai1 expression (p<0.05). After the Rac1 inhibitor was added, Orai1 siRNA could not further inhibit migration, invasion, and adhesion of the osteosarcoma cells. Further experiments showed that Ras activity was significantly inhibited after silencing Orai1 expression (p<0.05). Moreover, Orai1 siRNA did not further inhibit the activity of the Rac1-WAVE2 signaling pathway nor did it further inhibit the migration, invasion, and adhesion ability of osteosarcoma cells following the addition of Ras inhibitors.

Conclusions

Orai1 activates the Ras-Rac1-WAVE2 signaling pathway to promote metastasis of osteosarcoma. Abnormal expression or function of Orai1 may be an important cause of osteosarcoma metastasis.

RAC1 inhibition reverses cisplatin resistance in esophageal squamous cell carcinoma and induces downregulation of glycolytic enzymes

Development of chemoresistance remains a major challenge in treating esophageal squamous cell carcinoma (ESCC) patients despite treatment advances. However, the role of RAC1 in chemoresistance of ESCC and the underlying mechanisms remain largely unknown. In this study, we found that higher levels of RAC1 expression were associated with poorer prognosis in ESCC patients. Enhanced RAC1 expression increased cell proliferation, migration, and chemoresistance in vitro. Combination therapy using RAC1 inhibitor EHop-016 and cisplatin significantly promoted cell viability inhibition, G2/M phase cycle arrest, and apoptosis when compared to each monotherapy. Mechanistically, glycolysis was significantly downregulated in the RAC1 inhibitor monotherapy group and the combination group via inhibiting AKT/FOXO3a signaling when compared to the control group. Moreover, the silencing of RAC1 inhibited AKT/FOXO3a signaling and cell glycolysis while the upregulation of RAC1 produced an opposite effect. In murine xenograft models, the tumor volume and the expression of glycolytic enzymes were significantly reduced in combination therapy when compared to each monotherapy group. Overall, our study demonstrates that targeting RAC1 with an inhibitor overcomes cisplatin resistance in ESCC by suppressing glycolytic enzymes, which provides a promising strategy for treatment of ESCC in clinical practice.

5-Fluorouracil-based adjuvant chemotherapy improves the clinical outcomes of patients with lymphovascular invasion of upper urinary tract cancer and low expression of dihydropyrimidine dehydrogenase

Lymphovascular invasion (LVI) by urothelial carcinoma of the upper urinary tract (UC-UUT) is associated with an unfavorable prognosis. However, a high proportion of patients with UC-UUT are unable to receive the recommended doses of cisplatin-based adjuvant chemotherapy due to advanced age or renal dysfunction resulting from nephroureterectomy. Tegafur-uracil is an oral form of 5-fluorouracil whose efficacy is influenced by the activities of enzymes associated with its metabolism, such as dihydropyrimidine dehydrogenase (DPD), orotatephosphoribosyltransferase (OPRT) and thymidylate synthase (TS). The aim of the present study was to investigate the efficacy of adjuvant 5-fluorouracil chemotherapy for UC-UUT with LVI, and to assess the expression of enzymes associated with 5-fluorouracil metabolism as promising biomarkers of therapy efficacy. The present study retrospectively investigated 52 cases of UC-UUT. Following nephroureterectomy, tegafur-uracil was administered to 15 out of 30 patients with LVI who were not eligible for cisplatin-based adjuvant chemotherapy. Levels of DPD, OPRT and TS expression in tumor specimens were determined by reverse transcription-quantitative polymerase chain reaction, and their associations with the efficacy of adjuvant 5-fluorouracil chemotherapy were analyzed. The levels of DPD, OPRT and TS expression were not associated with pathological factors or outcome, although a higher expression of TS was associated with a poorer outcome. Adjuvant 5-fluorouracil chemotherapy significantly improved the outcome of patients with lower DPD expression. However, the levels of OPRT and TS expression did not influence therapeutic efficacy. Adjuvant 5-fluorouracil chemotherapy appears to be effective for lymphovascular-invasive UC-UUT in patients with lower DPD expression.

miR-506 regulates cell proliferation and apoptosis by affecting RhoA/ROCK signaling pathway in hepatocellular carcinoma cells

BACKGROUND

Hepatocellular carcinoma (HCC), is the third leading cause of cancer-related death. MicroRNA-506 (miR-506) has been reported to exhibit abnormal expression in HCC; however, the role of miR-506 in HCC and the molecular mechanisms underlying miR-506 in HCC remain unclarified.

METHODS

Quantitative reverse transcription polymerase chain reaction (qRT-PCR) assay was performed to detect the expression of miR-506 and Rho associated coiled-coil containing protein kinase 2 (ROCK2). Cell proliferation and apoptosis were evaluated by MTT assay and flow cytometry, respectively. Bioinformatics analysis and luciferase reporter assays were performed to identify the regulation between miR-506 and ROCK2. Western blot assay was performed to detect the expression of ROCK2, RhoA, and Ras-related C3 botulinum toxin substrate 1 (Rac1). The tumor growth in vivo was evaluated in a HCC xenograft mice model.

RESULTS

The mRNA levels of ROCK2 were significantly upregulated, while miR-506 levels were significantly downregulated in HCC tissues and cells. The expression of ROCK2 was negatively correlated with miR-506 in HCC tissues. In vitro, upregulation of miR-506 inhibited proliferation and induced apoptosis, and downregulation of miR-506 promoted proliferation and blocked apoptosis in HepG2 and Hep3B cells. ROCK2 was a target gene of miR-506 and miR-506 regulated the expression of ROCK2 in HepG2 and Hep3B cells. Furthermore, downregulation of miR-506 partially attenuated the tumor-suppressive effect of ROCK2 knockout on HepG2 and Hep3B cells, and upregulation of miR-506 partially attenuated the oncogenic effect of ROCK2 overexpression on HepG2 and Hep3B cells; Overexpression of ROCK2 increased and ROCK2 knockdown decreased the expression of Rac1, which were attenuated by upregulation of miR-506 or downregulation of miR-506, respectively. In addition, ROCK2 overexpression or knockdown hadno significant effect on RhoA expression. In vivo, upregulation of miR-506 suppressed tumor growth, while downregulation of miR-506 promoted tumor growth.

CONCLUSION

miR-506 was involved in cell proliferation and apoptosis by affecting RhoA/ROCK signaling pathway in HCC cells. Our results provide a novel mechanism of miR-506-mediated suppressive effects on HCC tumorigenesis.

PAK1 Expression in Pancreatic Cancer: Clinicopathological Characteristics and Prognostic Significance

BACKGROUND

Improvement of the management of pancreatic cancer requires a better understanding of the genetic and molecular changes responsible for the development of the disease. The family of p21-activated kinases (PAKs) and especially PAK1 appears to mediate many cellular processes that contribute to the development and progression of pancreatic cancer, but the clinical relevance of PAK1 expression with the disease still remains unclear. Aim of the study was to assess the clinical value and the potential prognostic significance of PAK1 in pancreatic adenocarcinoma.

METHODS

We investigated the relationship between the PAK1 expression and the clinical and histopathologic characteristics of pancreatic cancer patients and the potential significance of PAK1 on survival. We examined tissue samples from 51 patients operated for pancreatic cancer. PAK1 expression was investigated with immunohistochemistry and correlated to clinicopathological parameters.

RESULTS

PAK1 was detected in all tumor samples and high expression was found in most patients. High PAK1 expression was also associated with younger age and well-differentiated tumors, but no association was found between PAK1 expression and Tumor-Node-Metastasis stage as well as deceased or alive status on follow-up. Moderate to high PAK1 expression favored higher 6-month and 1-year survival and low PAK1 expression 2-year survival but without statistical significance.

CONCLUSIONS

Our results indicate that PAK1 could potentially be used as a prognostic marker in pancreatic cancer. Further studies could clarify whether utilization of PAK1 in therapeutic protocols for the treatment of pancreatic cancer will render them more effective.

sFRP1 exerts effects on gastric cancer cells through GSK3β/Rac1‑mediated restraint of TGFβ/Smad3 signaling

Secreted frizzled-related protein 1 (sFRP1) is an inhibitor of canonical Wnt signaling; however, previous studies have determined a tumor-promoting function of sFRP1 in a number of different cancer types. A previous study demonstrated that sFRP1 overexpression was associated with an aggressive phenotype and the activation of transforming growth factor β (TGFβ) signaling. sFRP1 overexpression and sFRP1 knockdown cell models were established. Immunoblotting was conducted to examine the protein levels of the associated molecules. Immunofluorescence staining followed by confocal microscopy was performed to visualize the cytoskeleton alterations and subcellular localization of key proteins. sFRP1 overexpression restored glycogen synthase kinase 3β (GSK3β) activity, which activated Rac family small GTPase 1 (Rac1). GSK3β and Rac1 mediated the effect of sFRP1 on the positive regulation of cell growth and migration/invasion. Inhibition of GSK3β or Rac1 abolished the regulation of sFRP1 on TGFβ/SMAD family member 3 (Smad3) signaling and the aggressive phenotype; however, GSK3β or Rac1 overexpression increased cell migration/invasion and restrained Smad3 activity by preventing its nuclear translocation and limiting its transcriptional activity. The present study demonstrated a tumor-promoting function of sFRP1-overexpression by selectively activating TGFβ signaling in gastric cancer cells. GSK3β and Rac1 serve an important function in mediating the sFRP1-induced malignant alterations and signaling changes.

Transcription Factors Contribute to Differential Expression in Cellular Pathways in Lung Adenocarcinoma and Lung Squamous Cell Carcinoma

Lung cancers are broadly classified into small cell lung cancers and non-small cell lung cancers (NSCLC). Lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC) are two common subtypes of NSCLC, and despite the fact that both occur in lung tissues, these two subtypes show a number of different pathological characteristics. To investigate the differences and seek potential therapy targets, we used bioinformatics methods to analyze RNA-Seq data from different aspects. The previous studies and comparative pathway enrichment analysis on publicly available data showed that expressed or inhibited genes are different in two cancer subtypes through important pathways. Some of these genes could not only affect cell function through expression, but also could regulate other genes' expression by binding to a specific DNA sequence. This kind of genes is called transcription factor (TF) or sequence-specific DNA-binding factor. Transcription factors play important roles in controlling gene expression in carcinoma pathways. Our results revealed transcription factors that may cause differential expression of genes in cellular pathways of LUAD and LUSC, which provide new clues for study and treatment. Once such TF is NFE2l2 which may regulate genes in the Wnt signaling pathway, and the MAPK signaling pathway, thus leading to an increase the cell growth, cell division, and gene transcription. Another TF-XBP1 has high correlation with genes related to cell adhesion molecules and cytokine-cytokine receptor interaction pathways that may further affect the immune system. Moreover, the two TF and high correlated genes also show similar patterns in an independent GEO data set.

Prognostic and Clinicopathological Value of Rac1 in Cancer Survival: Evidence from a Meta-Analysis

Purpose: The role of Rac1 in cancer survival has been widely studied. However, the prognostic and clinicopathological value of Rac1 remains inconclusive. We performed a meta-analysis to clarify the role of Rac1 in cancer survival as well as its association with clinicopathological features.

Methods: Eligible studies were searched from PubMed, Cochrane Library, Embase, and Web of Science databases. The pooled hazard ratios (HRs) and odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were used to detect the prognostic and clinicopathological role of Rac1.

Results: A total of 14 studies including 1793 patients were enrolled in the present meta-analysis. Pooled HR for overall survival (OS) (HR=2.02, 95% CI: 1.70-2.39) and disease-free survival (DFS) (HR=2.64, 95% CI: 1.71-4.09) indicated a significant poor prognostic effect for Rac1. Positive Rac1 expression was found to be correlated with tumor stage, blood vessel invasion, and lymph metastasis, but not with histological differentiation. Sensitivity test showed no single study altered OS or DFS significantly. No publication bias was detected by Egger's test and Begg's funnel plot test.

Conclusion: This meta-analysis indicated that Rac1 could be used as a potential marker to predict cancer prognosis. Additionally, Rac1 expression was associated with the malignancy-related phenotype.

Knockdown of RAC1 and VASP gene expression inhibits breast cancer cell migration

The ability of tumor cells to migrate is biologically fundamental for tumorigenesis, growth, metastasis and invasion. The present study examined the role of Ras-related C3 botulinum toxin substrate (RAC1) and vasodilator-stimulated phosphoprotein (VASP) in breast cancer cell migration. According to data in Kaplan, Oncomine and The Cancer Genome Atlas, increased expression levels of RAC1 and VASP in breast cancer are associated with decreased cancer cell differentiation, advanced pathological stage and more aggressive tumor subtypes, while increased VASP mRNA expression levels are positively correlated with a poor prognosis in patients with breast cancer. The short hairpin (sh)RNA technique was employed to knock down the expression of RAC1 or VASP. Stable interference with the expression of RAC1 or VASP using RAC1-shRNA or VASP-shRNA, respectively, was established in MCF-7 breast cancer cells. In RAC1-shRNA or VASP-shRNA cells, the protein expression levels of RAC1 or VASP were significantly downregulated compared with control cells. The proliferation and migration rates of the RAC1-shRNA or VASP-shRNA cells were significantly lower compared with control cells. It was observed that the protein expression levels of VASP also decreased in RAC1-shRNA cells compared with control cells. The results revealed that RAC1 and VASP may serve important roles in promoting the migration of MCF-7 breast cancer cells, and that VASP may among the downstream signaling molecules associated with RAC1.

Clinically significant association of elevated expression of nuclear factor E2-related factor 2 expression with higher glucose uptake and progression of upper urinary tract cancer

BACKGROUND

There is growing evidence that the transcription factor nuclear factor E2-related factor 2 (Nrf2) is the major participant in regulating antioxidants and pathways for detoxifying reactive oxygen species (ROS), as well as having a vital role in tumor proliferation, invasion, and chemoresistance. It was also recently reported that Nrf2 supports cell proliferation by promoting metabolic activity. Thus, Nrf2 is involved in progression of cancer. Upper urinary tract urothelial carcinoma (UTUC) is a biologically aggressive tumor with high rates of recurrence and progression, resulting in a poor prognosis. However, the role of Nrf2 in UTUC is largely unknown.

METHODS

In order to study the role of Nrf2 in UTUC from the metabolic perspective, we retrospectively assessed Nrf2 expression in the surgical specimen and the preoperative maximum standard glucose uptake (SUVmax) on [¹⁸F]fluorodeoxy-glucose positron emission tomography (¹⁸F-FDG-PET) of 107 patients with UTUC who underwent radical nephroureterectomy.

RESULTS

Increased expression of Nrf2 in the primary lesion was correlated with less differentiated histology, local invasion, and lymph node metastasis, and was also an independent indicator of shorter overall survival according to multivariate analysis. Furthermore, increased expression of Nrf2 was associated with higher preoperative SUVmax by the primary tumor on ¹⁸F-FDG-PET, while Nrf2 expression and SUVmax were also significantly correlated in the metastatic lymph nodes. Among the 18 patients with lymph node metastasis at nephroureterectomy who underwent retroperitoneal lymph node dissection and received adjuvant chemotherapy, the patients with higher Nrf2 expression in the primary tumor had worse recurrence-free survival.

CONCLUSIONS

These results suggest that constitutive activation of Nrf2 might be linked with tumor aerobic glycolysis and progression of UTUC, indicating that Nrf2 signaling in the tumor microenvironment promotes progression of UTUC.

p21-activated kinase 1 (PAK1) expression correlates with prognosis in solid tumors: A systematic review and meta-analysis

p21 protein (Cdc42/Rac)-activated kinase 1 (PAK1) expression appears to be predictive of prognosis in various solid tumors, though the evidence is not yet conclusive. We therefore performed a meta-analysis to explore the relationship between PAK1 and prognosis in patients with solid tumors. Relevant publications were searched in several widely used databases, and 15 studies (3068 patients) were included in the meta-analysis. Pooled hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated to evaluate the strength of the association between PAK1 and prognosis. Associations between PAK1 expression and prognosis were observed for overall survival (HR = 2.81, 95% CI = 1.07-7.39) and disease-specific survival (HR = 2.15, 95% CI = 1.47-3.16). No such association was detected for time to tumor progression (HR = 1.78, 95% CI = 0.99-3.21).Our meta-analysis thus indicates that PAK1 expression may be a predictive marker of overall survival and disease-specific survival in patients with solid tumors.

The Rho GTPase signalling pathway in urothelial carcinoma

Urothelial carcinoma remains a clinical challenge: non-muscle-invasive disease has a high rate of recurrence and risk of progression, and outcomes for patients with advanced disease are poor, owing to a lack of effective systemic therapies. The Rho GTPase family of enzymes was first identified >30 years ago and contains >20 members, which are divided into eight subfamilies: Cdc42, Rac, Rho, RhoUV, RhoBTB, RhoDF, RhoH, and Rnd. Rho GTPases are molecular on-off switches, which are increasingly being understood to have a critical role in a number of cellular processes, including cell migration, cell polarity, cell adhesion, cell cycle progression, and regulation of the cytoskeleton. This switch is an evolutionarily conserved system in which GTPases alternate between GDP-bound (inactive) and GTP-bound (active) forms. The activities of these Rho GTPases are many, context-dependent, and regulated by a number of proteins that are being progressively elucidated. Aberrations of the Rho GTPase signalling pathways have been implicated in various malignancies, including urothelial carcinoma, and understanding of the role of Rho GTPases in these diseases is increasing. This signalling pathway has the potential for therapeutic targeting in urothelial carcinoma. Research in this area is nascent, and much work is necessary before current laboratory-based research can be translated into the clinic.

Gain-of-function mutant p53 activates small GTPase Rac1 through SUMOylation to promote tumor progression

Here, Yue et al. investigated the mechanisms underlying p53 gain-of-function (GOF) mutations and found that mutant p53 activates small GTPase Rac1 as a critical mechanism for mutant p53 GOF to promote tumor progression. Their findings provide insight into a new mechanism for Rac1 activation in tumors and show that activation of Rac1 is an unidentified and critical mechanism for mutant p53 GOF in tumorigenesis.

Tumor suppressor p53 is frequently mutated in human cancer. Mutant p53 often promotes tumor progression through gain-of-function (GOF) mechanisms. However, the mechanisms underlying mutant p53 GOF are not well understood. In this study, we found that mutant p53 activates small GTPase Rac1 as a critical mechanism for mutant p53 GOF to promote tumor progression. Mechanistically, mutant p53 interacts with Rac1 and inhibits its interaction with SUMO-specific protease 1 (SENP1), which in turn inhibits SENP1-mediated de-SUMOylation of Rac1 to activate Rac1. Targeting Rac1 signaling by RNAi, expression of the dominant-negative Rac1 (Rac1 DN), or the specific Rac1 inhibitor NSC23766 greatly inhibits mutant p53 GOF in promoting tumor growth and metastasis. Furthermore, mutant p53 expression is associated with enhanced Rac1 activity in clinical tumor samples. These results uncover a new mechanism for Rac1 activation in tumors and, most importantly, reveal that activation of Rac1 is an unidentified and critical mechanism for mutant p53 GOF in tumorigenesis, which could be targeted for therapy in tumors containing mutant p53.

RETRACTED: Role of Rac1 Pathway in Epithelial-to-Mesenchymal Transition and Cancer Stem-like Cell Phenotypes in Gastric Adenocarcinoma

Rac1, a Rho GTPase family member, is dysregulated in a variety of tumor types including gastric adenocarcinoma, but little is known about its role in cancer stem-like cells (CSCs). Therefore, Rac1 activity and inhibition were examined in gastric adenocarcinoma cells and mouse xenograft models for epithelial-to-mesenchymal transition (EMT) and CSC phenotypes. Rac1 activity was significantly higher in spheroid-forming or CD44+ gastric adenocarcinoma CSCs compared with unselected cells. Rac1 inhibition using Rac1 shRNA or a Rac1 inhibitor (NSC23766) decreased expression of the self-renewal transcription factor, Sox-2, decreased spheroid formation by 78%-81%, and prevented tumor initiation in immunodeficient mice. Gastric adenocarcinoma CSCs had increased expression of the EMT transcription factor Slug, 4.4- to 8.3-fold greater migration, and 4.2- to 12.6-fold greater invasion than unselected cells, and these increases could be blocked completely with Rac1 inhibition. Gastric adenocarcinoma spheroid cells were resistant to 5-fluorouracil and cisplatin chemotherapy, and this chemotherapy resistance could be reversed with Rac1 shRNA or NSC23766. The PI3K/Akt pathway may be upstream of Rac1, and JNK may be downstream of Rac1. In the MKN-45 xenograft model, cisplatin inhibited tumor growth by 50%, Rac1 inhibition by 35%, and the combination by 77%. Higher Rac1 activity, in clinical specimens from gastric adenocarcinoma patients who underwent potentially curative surgery, correlated with significantly worse survival (P = 0.017). In conclusion, Rac1 promotes the EMT program in gastric adenocarcinoma and the acquisition of a CSC state. Rac1 inhibition in gastric adenocarcinoma cells blocks EMT and CSC phenotypes, and thus may prevent metastasis and augment chemotherapy.Implications: In gastric adenocarcinoma, therapeutic targeting of the Rac1 pathway may prevent or reverse EMT and CSC phenotypes that drive tumor progression, metastasis, and chemotherapy resistance. Mol Cancer Res; 15(8); 1106-16. ©2017 AACR.

Targeting PAK1

p21-Activated kinase 1 (PAK1) has attracted much attention as a potential therapeutic target due to its central role in many oncogenic signaling pathways, its frequent dysregulation in cancers and neurological disorders, and its tractability as a target for small-molecule inhibition. To date, several PAK1-targeting compounds have been developed as preclinical agents, including one that has been evaluated in a clinical trial. A series of ATP-competitive inhibitors, allosteric inhibitors and peptide inhibitors with distinct biochemical and pharmacokinetic properties represent useful laboratory tools for studies on the role of PAK1 in biology and in disease contexts, and could lead to promising therapeutic agents. Given the central role of PAK1 in vital signaling pathways, future clinical development of PAK1 inhibitors will require careful investigation of their safety and efficacy.

PAK5 mediates cell: cell adhesion integrity via interaction with E-cadherin in bladder cancer cells

Urothelial bladder cancer is a major cause of morbidity and mortality worldwide, causing an estimated 150 000 deaths per year. Whilst non-muscle-invasive bladder tumours can be effectively treated, with high survival rates, many tumours recur, and some will progress to muscle-invasive disease with a much poorer long-term prognosis. Thus, there is a pressing need to understand the molecular transitions occurring within the progression of bladder cancer to an invasive disease. Tumour invasion is often associated with a down-regulation of E-cadherin expression concomitant with a suppression of cell:cell junctions, and decreased levels of E-cadherin expression have been reported in higher grade urothelial bladder tumours. We find that expression of E-cadherin in a panel of bladder cancer cell lines correlated with the presence of cell:cell junctions and the level of PAK5 expression. Interestingly, exogenous PAK5 has recently been described to be associated with cell:cell junctions and we now find that endogenous PAK5 is localised to cell junctions and interacts with an E-cadherin complex. Moreover, depletion of PAK5 expression significantly reduced junctional integrity. These data suggest a role for PAK5 in maintaining junctional stability and we find that, in both our own patient samples and a commercially available dataset, PAK5mRNA levels are reduced in human bladder cancer compared with normal controls. Taken together, the present study proposes that PAK5 expression levels could be used as a novel prognostic marker for bladder cancer progression.

ARHGEF15 overexpression worsens the prognosis in patients with pancreatic ductal adenocarcinoma through enhancing the motility and proliferative activity of the cancer cells

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive neoplastic diseases, associated with a remarkably poor prognosis. However, the molecular mechanisms underlying the development of PDAC remain elusive. The aim of this study was to identify genes whose expressions are correlated with a poor prognosis in PDAC patients, and to unravel the mechanisms underlying the involvement of these genes in the development of the cancer.

METHODS

Global gene expression profiling was conducted in 39 specimens obtained from Japanese patients with PDAC to identify genes whose expressions were correlated with a shorter overall survival. The effect of gene silencing or overexpression of ARHGEF15 in pancreatic cancer cell lines was examined by introducing siRNAs of ARHGEF15 or the ARHGEF15 expression vector. After assessing the effect of ARHGEF15 deregulation on the Rho-family proteins by pull-down assay, wound healing, transwell and cell viability assays were carried out to investigate the cellular phenotypes caused by the perturbation.

RESULTS

The global mRNA expression profiling revealed that overexpression of ARHGEF15, a Rho-specific GEF, was significantly associated with a poor prognosis in patients with PDAC. We also found that the depletion of ARHGEF15 by RNA interference in pancreatic cancer cell lines downregulated the activities of molecules of the Rho signaling pathway, including RhoA, Cdc42 and Rac1. Then, we also showed that ARHGEF15 silencing significantly reduced the motility and viability of the cells, while its overexpression resulted in the development of the opposite phenotype in multiple pancreatic cancer cell lines.

CONCLUSION

These data suggest that upregulation of ARHGEF15 contributes to the development of aggressive PDAC by increasing the growth and motility of the pancreatic cancer cells, thereby worsening the prognosis of these patients. Therefore, ARHGEF15 could serve as a novel therapeutic target in patients with PDAC.

PAKs in Human Cancer Progression: From Inception to Cancer Therapeutic to Future Oncobiology

Since the initial recognition of a mechanistic role of p21-activated kinase 1 (PAK1) in breast cancer invasion, PAK1 has emerged as one of the widely overexpressed or hyperactivated kinases in human cancer at-large, allowing the PAK family to make in-roads in cancer biology, tumorigenesis, and cancer therapeutics. Much of our current understanding of the PAK family in cancer progression relates to a central role of the PAK family in the integration of cancer-promoting signals from cell membrane receptors as well as function as a key nexus-modifier of complex, cytoplasmic signaling network. Another core aspect of PAK signaling that highlights its importance in cancer progression is through PAK's central role in the cross talk with signaling and interacting proteins, as well as PAK's position as a key player in the phosphorylation of effector substrates to engage downstream components that ultimately leads to the development cancerous phenotypes. Here we provide a comprehensive review of the recent advances in PAK cancer research and its downstream substrates in the context of invasion, nuclear signaling and localization, gene expression, and DNA damage response. We discuss how a deeper understanding of PAK1's pathobiology over the years has widened research interest to the PAK family and human cancer, and positioning the PAK family as a promising cancer therapeutic target either alone or in combination with other therapies. With many landmark findings and leaps in the progress of PAK cancer research since the infancy of this field nearly 20 years ago, we also discuss postulated advances in the coming decade as the PAK family continues to shape the future of oncobiology.

Rac1 is correlated with aggressiveness and a potential therapeutic target for gastric cancer

Rac1 is a member of the Rho GTPase family. Rac1 activity is critical in regulating cytoskeleton organization and thus, modulates a diverse spectrum of cellular functions in normal and malignant cells. The aims of the present study were to investigate the expression pattern and clinical significance of Rac1, as well as the role of Rac1 in gastric cancer tumorigenesis and metastasis. The expression of Rac1 in human gastric cancer was explored by immunohistochemistry. The correlation of Rac1 expression with the clinicopathological characteristics and the survival of patients were analyzed by Pearson's Chi-square and Kaplan-Meier analyses, respectively. Rac1 overexpression cell model was used to examine in vitro and in vivo effects of Rac1 in cell growth, migration and invasion. Rac1 was highly expressed in gastric cancer tissues and correlated with differentiation, local invasion, lymph node metastasis and Lauren's classification. Rac1 expression in gastric cancer predicted shorter survival. Overexpression of Rac1 in gastric cancer cells dramatically induced Rac1 activation and rendered a more aggressive phenotype such as increased cell growth and migration/invasion in vitro and in vivo. Inhibiting Rac1 activity by specific inhibitor abrogated the effects of Rac1 on the malignant phenotype. Our clinical findings demonstrated that Rac1 was well correlated with aggressiveness and a negative prognostic factor. In addition, our data on experimental cell models supported the fundamental role of Rac1 in gastric cancer. Given its pivotal role in gastric tumorigenesis and progression, Rac1 can serve as a promising therapeutic target for gastric cancer.

Tyrosyl phosphorylated serine-threonine kinase PAK1 is a novel regulator of prolactin-dependent breast cancer cell motility and invasion

Despite efforts to discover the cellular pathways regulating breast cancer metastasis, little is known as to how prolactin (PRL) cooperates with extracellular environment and cytoskeletal proteins to regulate breast cancer cell motility and invasion. We implicated serine-threonine kinase p21-activated kinase 1 (PAK1) as a novel target for PRL-activated Janus-kinase 2 (JAK2). JAK2-dependent PAK1 tyrosyl phosphorylation plays a critical role in regulation of both PAK1 kinase activity and scaffolding properties of PAK1. Tyrosyl phosphorylated PAK1 facilitates PRL-dependent motility via at least two mechanisms: formation of paxillin/GIT1/βPIX/pTyr-PAK1 complexes resulting in increased adhesion turnover and phosphorylation of actin-binding protein filamin A. Increased adhesion turnover is the basis for cell migration and phosphorylated filamin A stimulates the kinase activity of PAK1 and increases actin-regulating activity to facilitate cell motility. Tyrosyl phosphorylated PAK1 also stimulates invasion of breast cancer cells in response to PRL and three-dimensional (3D) collagen IV via transcription and secretion of MMP-1 and MMP-3 in a MAPK-dependent manner. These data illustrate the complex interaction between PRL and the cell microenvironment in breast cancer cells and suggest a pivotal role for PRL/PAK1 signaling in breast cancer metastasis.

Clinicopathological and cellular signature of PAK1 in human bladder cancer

Bladder cancer (BC) is the ninth most common cancer and the 13th most common cause of cancer death. Although p21 protein-activated kinase (PAK) regulates cell growth, motility, and morphology, the expression and function of PAK1 associated with the clinicopathological and cellular signature of human BC are not clear. This study was to examine the expression of PAK1 in human BC, the association of PAK1 with clinicopathological features, and the effect of PAK1 on cell proliferation, migration, and invasion in BC cells. A total of 54 BC and 12 normal bladder tissue specimens were retrieved. Among 54 BC patients, 39 cases were superficial BC and 15 cases were invasive BC. Histological examination revealed 29 patients with low-grade and 25 patients with high-grade papillary urothelial carcinomas. Immunohistochemical staining showed that PAK1 was overexpressed in BC tissue compared with normal bladder tissue. The overexpression of PAK1 was significantly associated with tumor size, histological grade, and lymph node metastasis, but not with gender, age, clinical stage, tumor number, and recurrence. Furthermore, the cytoplasmic distribution of PAK1 was observed in BC cells. Knocking down of PAK1 using lentiviral transduction decreased BC cell proliferation, migration, and invasion. In conclusion, we demonstrated that the overexpression of PAK1 is closely associated with the clinicopathological features of BC, suggesting that PAK1 may play an important role in the development and progression of BC and may be a potential therapeutic target for the treatment of BC.