The complex roles of Wnt antagonists in RCC

Wnt signaling: Modulating tumor-associated macrophages and related immunotherapeutic insights

Wnt signaling pathways are highly conserved cascades that mediate multiple biological processes through canonical or noncanonical pathways, from embryonic development to tissue maintenance, but they also contribute to the pathogenesis of numerous cancers. Recent studies have revealed that Wnt signaling pathways critically control the interplay between cancer cells and tumor-associated macrophages (TAMs) in the tumor microenvironment (TME) and potentially impact the efficacy of cancer immunotherapy. In this review, we summarize the evidence that Wnt signaling pathways boost the maturation and infiltration of macrophages for immune surveillance in the steady state but also polarize TAMs toward immunosuppressive M2-like phenotypes for immune escape in the TME. Both cancer cells and TAMs utilize Wnt signaling to transmit signals, and this interaction is crucial for the carcinogenesis and progression of common solid cancers, such as colorectal, gastric, hepatocellular, breast, thyroid, prostate, kidney, and lung cancers; osteosarcoma; and glioma. Specifically, compared with those in solid cancers, Wnt signaling pathways play a distinct role in the pathogenesis of leukemia. Efforts to develop Wnt-based drugs for cancer treatment are still ongoing, and some indeed enhance the anticancer immune response. We believe that the combination of Wnt signaling-based therapy with conventional or immune therapies is a promising therapeutic approach and can facilitate personalized treatment for most cancers.

HIF2α Promotes Cancer Metastasis through TCF7L2-Dependent Fatty Acid Synthesis in ccRCC

Recent studies have highlighted the notable involvement of the crosstalk between hypoxia-inducible factor 2 alpha (HIF2α) and Wnt signaling components in tumorigenesis. However, the cellular function and precise regulatory mechanisms of HIF2α and Wnt signaling interactions in clear cell renal cell carcinoma (ccRCC) remain elusive. To analyze the correlation between HIF2α and Wnt signaling, we utilized the Cancer Genome Atlas - Kidney Renal Clear Cell Carcinoma (TCGA-KIRC) public database, HIF2α RNA sequencing data, and conducted luciferase reporter assays. A Wnt-related gene set was employed to identify key regulators of Wnt signaling controlled by HIF2α in ccRCC. Furthermore, we assessed the biological effects of TCF7L2 on ccRCC metastasis and lipid metabolism in both in vivo and in vitro settings. Our outcomes confirm TCF7L2 as a key gene involved in HIF2α-mediated regulation of the canonical Wnt pathway. Functional studies demonstrate that TCF7L2 promotes metastasis in ccRCC. Mechanistic investigations reveal that HIF2α stabilizes TCF7L2 mRNA in a method based on m6A by transcriptionally regulating METTL3. Up-regulation of TCF7L2 enhances cellular fatty acid oxidation, which promotes histone acetylation. This facilitates the transcription of genes connected to epithelial-mesenchymal transition and ultimately enhances metastasis of ccRCC. These outcomes offer a novel understanding into the involvement of lipid metabolism in the signaling pathway regulation, offering valuable implications for targeted treatment in ccRCC.

RUNX1 predicts poor prognosis and correlates with tumor progression in clear cell renal carcinoma

BACKGROUND

Runt-related transcription factor 1 (RUNX1), also called acute myeloid leukaemia 1, is a member of RUNX family of transcription factors. This family is composed of evolutionarily conserved transcription factors that function as critical lineage determinants in various tissues, however its function in cancer development and clinical significance in RCC are still unknown.

METHODS

We used paraffin-embedded tumor tissues from 100 patients and fresh-harvested and paired adjacent normal renal tissues from 15 RCC patients who underwent primary surgical resection in Xijing Hospital between 2018 and 2022. The expression level of RUNX1 was evaluated by immunohistochemistry and Western Blot. RUNX1 promoted tumor cells proliferation, migration and invasion were verified by CCK-8, wound-healing and transwell assays. Finally, we constructed a xenografts model of the 786-O cell lines to observe the effect of RUNX1 on tumorigenesis in vivo.

RESULTS

TCGA database showed higher RUNX1 expression levels in KIRC (kidney renal clear cell carcinoma). In overall survival analysis, RCC patients with higher RUNX1 expression level would have a shorter survival period than those with lower expression. Similarly, immunohistochemical results of our cohort also showed that RUNX1 was over-expression in cancer tissues than in corresponding non-cancer tissues. We also proved this result at protein level by western-blot. Meanwhile, prognostic and OS analyses of our cohort showed that the RUNX1 expression level was an individual prognostic factor in RCC patients. CCK-8, wound-healing and transwell assays proved that the overexpression of RUNX1 in Caki-1 cells promoted the proliferation, migration and invasion of the cells. Knocking down RUNX1 in 786-O cells inhibited the proliferation, migration and invasion of cells. The experimental results of xenografts model in nude mice showed that the knockdown of RUNX1 in 786-O cells slowed down the growth of tumor.

CONCLUSION

RUNX1 is a poor prognostic factor of clear cell renal carcinoma, which may provide a novel therapeutic target for ccRCC.

MiR-24-1-5p Hinders Malignant Phenotypes of Clear Cell Renal Cell Carcinoma by Targeting SHOX2

MiRNAs are essential epigenetic modulators that can regulate protein expression. According to the principle of base complementary pairing, miRNA is partially or completely complementary to the 3'-UTR region of its target gene, by which it inhibits the translation of the targeted gene. This study investigated the role of miR-24-1-5p in clear cell renal cell carcinoma (ccRCC). Data in TCGA-KIRC denoted that miR-24-1-5p was under-expressed in ccRCC. Bioinformatics analysis predicted that its target gene was SHOX2, which was significantly expressed in cancer tissues. Dual luciferase assay verified the targeting relationship between miR-24-1-5p and SHOX2. Cell function experiments demonstrated that overexpression of miR-24-1-5p significantly inhibited SHOX2 level and the malignant phenotypes of ccRCC cells. The above results illustrated that miR-24-1-5p/SHOX2 axis was critical for the oncogenesis and development of ccRCC, which might be helpful for us to understand the mechanism and novel therapeutic methods of ccRCC.

Tanshinone IIA exerts autophagic cell death through down-regulation of β-catenin in renal cell carcinoma cells

Renal cell carcinoma (RCC), also called kidney cancer, is one of the most common malignancies worldwide, including the United States and China. Because of the characteristics of RCC that are both insidious and largely insensitive to chemo-radiation, the incidence and mortality of RCC are increasing every year. However, there are few studies describing anti-cancer effects of the natural compounds on RCC as compared to other cancers. Here, we analyzed the anti-neoplastic impact of Tanshinone IIA (TSN) on RCC cells. We noted that TSN increased the expression of LC3 proteins while having little effect on PARP and Alix protein expression. We found that TSN up-regulated the expression of autophagy-related proteins such as Atg7 and Beclin-1. Moreover, TSN promoted the formation of autophagic vacuoles such as autophagosomes and autolysosomes. However, treatment with 3-Methyladenine (3-MA) or Chloroquine (CQ), slightly decreased the ability of TSN to induce autophagy, but still autophagy occurred. In addition, TSN inhibited translocation of β-catenin into the nucleus, and β-catenin deletion and TSN treatment in RCC increased the expression of LC3 protein. Overall our findings indicate that TSN can exert significant anti-tumor effects through down-regulation of β-catenin to induce autophagic cell death.

CENPA promotes clear cell renal cell carcinoma progression and metastasis via Wnt/β-catenin signaling pathway

Clear cell renal cell carcinoma (ccRCC) is the most common malignant tumor of the kidney. New and reliable biomarkers are in urgent need for ccRCC diagnosis and prognosis. The CENP family is overexpressed in many types of cancers, but its functions in ccRCC have not been fully clarified. In this paper, we found that several CENP family members were highly expressed in ccRCC tissues. Also, CENPA expression level was related to clinicopathological grade and prognosis by weighted gene co-expression network analysis (WGCNA). CENPA served as a representative CENP family member as a ccRCC biomarker. Further in vitro experiments verified that overexpression of CENPA promoted ccRCC proliferation and metastasis by accelerating the cell cycle and activating the Wnt/β-catenin signaling pathway. The elevated β-catenin led by CENPA overexpression translocated to nucleus for downstream effect. Functional recovery experiment confirmed that Wnt/β-catenin pathway was essential for ccRCC progression and metastasis. Developing selective drugs targeting CENPA may be a promising direction for cancer treatment.

ANGPTL3 Overexpression Suppresses the Development of Oncogenic Properties in Renal Cell Carcinoma via the Wnt/β-Catenin Signaling Pathway and Predicts Good Prognosis

Angiopoietin-like 3 (ANGPTL3), which is involved in new blood vessel growth, has been reported to exhibit an abnroaml expression in many different cancers. However, the expressing pattern and functions of ANGPTL3 renal cell carcinoma (RCC) were rarely reported. In this study, we observed that ANGPTL3 expression was distinctly downregulated in both RCC specimens from TCGA datasets and cell lines. Survival assays also revealed that patients with low ANGPTL3 expression exhibited a shorter overall survival and disease-free survival than those with high ANGPTL3 expression. Cell counting kit-8 (CCK-8) assay, Colony formation assay, and flow cytometry showed that overexpression of ANGPTL3 distinctly suppressed the proliferation of RCC cells, and promoted apoptosis. Transwell assays and Wound healing assays revealed that ANGPTL3 upregulation suppressed the migration and invasion of RCC cells. Then, we explored whether ANGPTL3 dysregulation influenced the alteration of Wnt/β-catenin signaling using TOP/FOP flash reporter assays and western blot. The results showed that overexpression of ANGPTL3 distinctly suppressed the activity of Wnt/β-catenin signaling. Overall, our results confirmed that overexpression of ANGPTL3 was related to the malignancy and good prognosis of RCC patients, and ANGPTL3 upregulation inhibited the tumor proliferation and metastasis via the Wnt/β-catenin pathway. ANGPTL3 may be a novel therapeutic target and a prognostic biomarker for RCC patients.

Immunohistochemical analysis of beta-catenin expression: a probable prognostic marker and potential therapeutic target in renal cell carcinoma

Background and aims

Renal cell carcinoma (RCC) seems to be the most aggressive type of genitourinary neoplasm. Down regulation of normal beta-catenin expression contributes to development of RCC, reflecting the role of beta-catenin/Wnt signaling pathway in pathogenesis. This study aims to evaluate the significance of beta-catenin expression and its correlation with the prognostic parameters.

Methods

A cross-sectional observational study was carried out in a tertiary care center on 58 RCC cases using variables like histological grade and type, tumor stage, necrosis. Formalin fixed, paraffin-embedded blocks were evaluated for beta-catenin expression by immunohistochemistry using scoring system. Data were analyzed by mean ± SD, χ² test, Pearson’s correlation test.

Results

Membranous score (MS) had a strong negative correlation with tumor stage (r=−0.407, p=0.044) and grade (r=−0.787, p=<0.001). Mean membranous score difference between low (Stage 1 and 2) vs. high stage (Stage 3 and 4) and low (Grade 1 and 2) vs. high grade (Grade 3 and 4) was statistically significant (p<0.001). Cytoplasmic score (CS) had positive correlation with tumor stage (r=0.586; p=0.002). No significant correlation was evident between cytoplasmic scores and tumor grade, however the mean cytoplasmic score difference between low grade vs. high grade was statistically significant (p < 0.001).

Conclusion

Beta-catenin may play a crucial role in the pathogenesis of RCC and has a positive correlation with the biological behavior of this tumor. The important role of beta-catenin as a prognostic parameter and probably a critical evaluator of targeted chemotherapy cannot be overemphasized.

Expression of RSK4, CD44 and MMP-9 is upregulated and positively correlated in metastatic ccRCC

BACKGROUND

To investigate the expression and function of RSK4, MMP-9 and CD44 in primary clear cell renal cell carcinoma (primary ccRCC) and metastatic clear cell renal cell carcinoma (metastatic ccRCC), as well as the correlation with clinicopathological features of patients.

METHOD

The expression levels of RSK4, CD44 and MMP-9 in 52 primary ccRCC samples and 48 metastatic ccRCC samples were detected by immunohistochemistry, and the relationship between RSK4, CD44 and MMP-9 expression and clinicopathological features as well as prognosis of metastatic ccRCC patients was statistically analysed. Ectopic RSK4 expression in ccRCC cell lines was performed to determine its effect on cell cycle regulation, tumour invasiveness, and metastatic capability.

RESULTS

The positive rates of RSK4, MMP-9 and CD44 expression in metastatic ccRCC tissues were 75, 68.75 and 91.7%, respectively, while the rates in primary ccRCC tissues were 44.2, 34.6 and 69.2%, respectively. Thus, the positive rates in metastatic ccRCC were higher than those in primary ccRCC (PRSK4 = 0. 002; PMMP-9 = 0. 002; PCD44 = 0. 001). However, the expression of RSK4, CD44 and MMP-9 was unrelated to age, gender, or metastatic sites (P > 0.05) but was related to WHO/ISUP nucleolar grade (PRSK4 = 0.019; PCD44 = 0.026; PMMP-9 = 0.049). In metastatic ccRCC, expression among the three proteins showed a positive correlation (P = 0.008). Moreover, expression between RSK4 and CD44 (P = 0.019) and MMP-9 and CD44 (P = 0.05) also showed positive correlations, whereas RSK4 and MMP-9 showed no significant correlation (P = 1.00). Molecular studies showed that overexpression of RSK4 could enhance the invasive and migratory abilities of ccRCC cell lines through the regulation of CD44 and MMP-9 expression and vice versa.

CONCLUSIONS

The overexpression of RSK4, MMP-9 and CD44 is associated with the invasion and metastasis of ccRCC, indicating that they could be potential prognostic factors and serve as new potential therapeutic targets for ccRCC.

Decreased expression of SFRP2 promotes development of the pituitary corticotroph adenoma by upregulating Wnt signaling

Cushing's disease is primarily caused by pituitary adrenocorticotropin‑secreting adenoma. However, its pathogenesis has remained obscure. In the present study, whole transcriptome analysis was performed by RNA sequencing (RNA‑Seq) and expression of secreted frizzled‑related protein 2 (SFRP2) was decreased in corticotroph tumors compared with normal pituitary glands. Furthermore, the RNA‑Seq results were validated and the expression of SFRP2 in tumor tissues was analyzed by comparing another cohort of 23 patients with Cushing's disease and 3 normal human pituitary samples using reverse transcription‑quantitative polymerase chain reaction, western blot and immunohistochemistry staining. Clinically, there was an association between lower SFRP2 expression and aggressive adenoma characteristics, including larger size and invasiveness. Conversely, SFRP2 overexpression reduced the ability of AtT20 cells to proliferate and migrate, and reduced production of the adrenocorticotrophic hormone in vitro. Mechanistically, overexpressed SFRP2 reduced the level of β‑catenin in the cytoplasm and nucleus, and decreased Wnt signaling activity in AtT20 cells. Therefore, SFRP2 appears to act as a tumor suppressor in Cushing's disease by regulating the activity of the Wnt signaling pathway.

Effect of perineoplasm perinephric adipose tissues on migration of clear cell renal cell carcinoma cells: a potential role of WNT signaling

To investigate the cellular and molecular interactions between clear-cell renal cell carcinoma (ccRCC) and perinephric adipose tissue (PAT), perineoplasm PAT, PAT away from the neoplasm, renal sinus and subcutaneous adipose tissues were collected at the time of renal surgery for renal masses and conditioned medium (CM) was generated from 62 patients. Perineoplasm PAT CMs from 44 out of 62 (about 71%) of patients with ccRCC or benign renal diseases (e.g. oncocytomas, angiomyolipomas, multicystic kidney, interstitial fibrosis, etc.) enhanced the migration of CaKi-2 cells. Perineoplasm PAT CMs from ccRCC significantly increased migration of ACHN and CaKi-2 cells by ~8.2 and ~2.4 folds, respectively, relative to those from benign renal diseases, whereas there is no significant difference in migration between ccRCC and benign renal diseases in CMs collected from culturing PAT away from neoplasm, renal sinus and subcutaneous adipose tissues. High Fuhrman Grade was associated with increased migration of Caki-2 cells by perineoplasm PAT CMs. Perineoplasm PATs from pT3 RCCs overexpressed multiple WNTs and their CMs exhibited higher WNT/ß-catenin activity and increased the migration of Caki-2 cells compared to CMs from benign neoplasms. Addition of secreted WNT inhibitory factor-1 recombinant protein into perineoplasm PAT CMs completely blocked the cell migration. These results indicate that WNT related factors from perineoplasm PAT may promote progression of local ccRCC to locally advanced (pT3) disease by increasing ccRCC cell mobility.

Wnt Signaling in Kidney Development and Disease

Wnt signal cascade is an evolutionarily conserved, developmental pathway that regulates embryogenesis, injury repair, and pathogenesis of human diseases. It is well established that Wnt ligands transmit their signal via canonical, β-catenin-dependent and noncanonical, β-catenin-independent mechanisms. Mounting evidence has revealed that Wnt signaling plays a key role in controlling early nephrogenesis and is implicated in the development of various kidney disorders. Dysregulations of Wnt expression cause a variety of developmental abnormalities and human diseases, such as congenital anomalies of the kidney and urinary tract, cystic kidney, and renal carcinoma. Multiple Wnt ligands, their receptors, and transcriptional targets are upregulated during nephron formation, which is crucial for mediating the reciprocal interaction between primordial tissues of ureteric bud and metanephric mesenchyme. Renal cysts are also associated with disrupted Wnt signaling. In addition, Wnt components are important players in renal tumorigenesis. Activation of Wnt/β-catenin is instrumental for tubular repair and regeneration after acute kidney injury. However, sustained activation of this signal cascade is linked to chronic kidney diseases and renal fibrosis in patients and experimental animal models. Mechanistically, Wnt signaling controls a diverse array of biologic processes, such as cell cycle progression, cell polarity and migration, cilia biology, and activation of renin-angiotensin system. In this chapter, we have reviewed recent findings that implicate Wnt signaling in kidney development and diseases. Targeting this signaling may hold promise for future treatment of kidney disorders in patients.

Genetic association of polymorphisms in AXIN1 gene with clear cell renal cell carcinoma in a Chinese population

Aim: The purpose of the present study is to investigate the association between the polymorphisms in AXIN1 with susceptibility to clear cell renal cell carcinoma (ccRCC). Materials & methods: A total of 284 ccRCC patients and 439 healthy volunteers were enrolled. Totally three tag single nucleotide polymorphisms in AXIN1 gene were genotyped using PCR & restriction fragment length polymorphism. Results: Significantly increased ccRCC risk was observed to be associated with the CT/CC genotypes of rs1805105 and AA genotype of rs12921862. Patients carrying the rs1805105 CT genotype had a 1.92-fold increased risk to developing clinical stage III and IV cancer. Conclusion: Our results suggested the rs1805105 CT/CC genotypes and rs12921862 AA genotype may relate to ccRCC development.

Frizzled 8 promotes the cell proliferation and metastasis of renal cell carcinoma

Recent reports have shown a rapid rise in the incidence of renal cell carcinoma (RCC), and Wnt (Wingless-related integration site) signaling pathway is important in RCC. Frizzled 8 (FZD8) is a member of Frizzled (FZD) receptor family which could activate canonical or non-canonical Wnt/β-catenin pathways. Nevertheless, the role of FZD8 in RCC is poorly investigated. The immunohistochemical analysis showed high expression of FZD8 in RCC tissues compared with peri-tumor tissues. FZD8 knockdown decreased the ability of proliferation and metastasis of RCC cells. Research revealed that the FZD8 regulated the transcription of Cyclin D1, c-Myc, and could promote the epithelial to mesenchymal transition (EMT) by mediating Vimentin and Snail through the Wnt/β-catenin signaling pathway. In addition, the results of our experiment revealed that FZD8 is involved in the regulation of non-canonical Wnt signaling pathway. These data suggested that the expression of FZD8 may play an important role in the proliferation and metastasis of RCC, and serve as a putative promising drug target for human RCC therapy.

ZEB1-induced tumourigenesis requires senescence inhibition via activation of DKK1/mutant p53/Mdm2/CtBP and repression of macroH2A1

OBJECTIVE

Understand the role of ZEB1 in the tumour initiation and progression beyond inducing an epithelial-to-mesenchymal transition.

DESIGN

Expression of the transcription factor ZEB1 associates with a worse prognosis in most cancers, including colorectal carcinomas (CRCs). The study uses survival analysis, in vivo mouse transgenic and xenograft models, gene expression arrays, immunostaining and gene and protein regulation assays.

RESULTS

The poorer survival determined by ZEB1 in CRCs depended on simultaneous high levels of the Wnt antagonist DKK1, whose expression was transcriptionally activated by ZEB1. In cancer cells with mutant TP53, ZEB1 blocked the formation of senescence-associated heterochromatin foci at the onset of senescence by triggering a new regulatory cascade that involves the subsequent activation of DKK1, mutant p53, Mdm2 and CtBP to ultimately repress macroH2A1 (H2AFY). In a transgenic mouse model of colon cancer, partial downregulation of Zeb1 was sufficient to induce H2afy and to trigger in vivo tumour senescence, thus resulting in reduced tumour load and improved survival. The capacity of ZEB1 to induce tumourigenesis in a xenograft mouse model requires the repression of H2AFY by ZEB1. Lastly, the worst survival effect of ZEB1 in patients with CRC ultimately depends on low expression of H2AFY and of senescence-associated genes.

CONCLUSIONS

The tumourigenic capacity of ZEB1 depends on its inhibition of cancer cell senescence through the activation of a herein identified new molecular pathway. These results set ZEB1 as a potential target in therapeutic strategies aimed at inducing senescence.

miR-106b-5p promotes renal cell carcinoma aggressiveness and stem-cell-like phenotype by activating Wnt/β-catenin signalling

PURPOSE

To examine the role of miR-106b-5p in regulating the cancer stem-cell-like phenotype in clear cell renal cell carcinomas (ccRCC).

EXPERIMENTAL DESIGN

Real-time PCR was performed to evaluate miR-106b-5p levels in ccRCC cell lines and patients specimens. A series of in vivo and in vitro assays were performed to confirm the effect of miR-106b-5p on ccRCC stemness phenotype.

RESULTS

ccRCC cells and tissues expressed more miR-106b-5p than normal controls. Gain- and loss-of-function studies demonstrated that overexpression of miR-106b-5p in ccRCC cells increased the spheres formation ability and the proportion of side population cells. Ectopic expression of miR-106b-5p in ccRCC cells increased tumour growth rates and the number of metastatic colonies in the lungs by using an orthotopic kidney cancer model and a tail vein injection model, respectively. Mechanistic studies revealed that, miR-106b-5p has an activating effect on Wnt/β-catenin signalling. miR-106p-5p overexpression simultaneously targets multiple negative regulators of the Wnt/β-catenin pathway, namely, LZTFL1, SFRP1 and DKK2. In addition, we also confirmed that miR-106b-5p and its targets expression correlates with the overall-survival of ccRCC patients from TCGA.

CONCLUSIONS

These findings suggest that miR-106b-5p mediates the constitutive activation of Wnt/β-catenin signalling, likely serving as a potential therapeutic target for ccRCC.

Developing and characterization of single chain variable fragment (scFv) antibody against frizzled 7 (Fzd7) receptor

ABSTACT Wnt/β-catenin signaling pathway through Frizzled receptors has been shown to play a key role in both normal development and tumorigenesis. Overexpression of Wnt pathway genes, such as Fzd7 in several malignancies is well-documented. Therefore, targeting of Fzd7 and its ligand inhibits cancer cells proliferation metastasis. In the present study we isolated single chain variable fragments (scFvs) against Fzd7 receptor using phage display method. Semi-synthetic human naive antibody libraries (Tomlinson I + J) was employed in panning procedure to isolate specific scFv against specific peptide from extracellular domain of Fzd7 receptor. The reactivity and growth inhibition effects of the selected antibodies was evaluated using enzyme-linked immunosorbent assay (ELISA), MTT and annexin V assays, respectively. Seven scFvs reactive to Fzd7 were selected following 4 rounds of panning. The results showed that the selected scFvs inhibits cell growth through apoptosis cell death in a triple negative breast cancer cells, MDA-MB-231. Given that Fzd7 and Wnt pathway plays a critical role in tumor progression, selected blocking scFvs represent significant potential for immunotherapy of breast cancer cells.

Wnt Signaling in Renal Cell Carcinoma

Renal cell carcinoma (RCC) accounts for 90% of all kidney cancers. Due to poor diagnosis, high resistance to the systemic therapies and the fact that most RCC cases occur sporadically, current research switched its focus on studying the molecular mechanisms underlying RCC. The aim is the discovery of new effective and less toxic anti-cancer drugs and novel diagnostic markers. Besides the PI3K/Akt/mTOR, HGF/Met and VHL/hypoxia cellular signaling pathways, the involvement of the Wnt/β-catenin pathway in RCC is commonly studied. Wnt signaling and its targeted genes are known to actively participate in different biological processes during embryonic development and renal cancer. Recently, studies have shown that targeting this pathway by alternating/inhibiting its intracellular signal transduction can reduce cancer cells viability and inhibit their growth. The targets and drugs identified show promising potential to serve as novel RCC therapeutics and prognostic markers. This review aims to summarize the current status quo regarding recent research on RCC focusing on the involvement of the Wnt/β-catenin pathway and how its understanding could facilitate the identification of potential therapeutic targets, new drugs and diagnostic biomarkers.

TIKI2 is upregulated and plays an oncogenic role in renal cell carcinoma

TIKI2 is a negative regulator of the Wnt family. Although many Wnt antagonists play important roles in renal cell carcinoma (RCC), the molecular function of TIKI2 in human RCC has not been fully elucidated. Here, we analyzed TIKI2 mRNA level in RCC specimens, the corresponding non-tumor tissues, RCC cell lines, and human proximal tubule epithelial cell line HK-2 using qPCR. We demonstrated that TIKI2 was highly expressed in RCC tissue (P < 0.05) and most RCC cell lines. In vitro, TIKI2 knockdown significantly inhibited proliferation, invasion, and clone formation ability of 769-P cells compared with controls, while ectopic TIKI2 expression enhanced A498 cell proliferation, invasion, and clone formation ability. In vivo, the average tumor volume was significantly increased in mice injected with A498-Tiki2 cells (P < 0.05). In the 769-P cell TIKI2 knockdown group, the average tumor volume was not significantly different compared to that of the control group (P = 0.08). Moreover, Wnt/β-catenin signaling was not affected by TIKI2 knockdown or overexpression. Results of the present study indicate that TIKI2 is upregulated in RCC tissues and plays an oncogenic role in RCC.

SFRP2 augments WNT16B signaling to promote therapeutic resistance in the damaged tumor microenvironment

Most tumors initially respond to cytotoxic treatments, but acquired resistance often follows. The tumor microenvironment (TME) is a major barrier to clinical success by compromising therapeutic efficacy, and pathological relevance of multiple soluble factors released by a therapeutically remodeled TME remains largely unexplored. Here we show that the secreted frizzled-related protein 2 (SFRP2), a Wnt pathway modulator, is produced by human primary fibroblasts after genotoxic treatments. SFRP2 induction is remarkable in tumor stroma, with transcription mainly modulated by the nuclear factor-κB (NF-κB) complex, a property shared by several effectors of the DNA damage secretory program. Instead of directly altering canonical Wnt signaling, SFRP2 augments β-catenin activities initiated by WNT16B, another soluble factor from DNA-damaged stroma. WNT16B recognizes cancer cell surface receptors including frizzled (FZD) 3/4/6, a process enhanced by SFRP2, coordinated by the co-receptor LRP6 but subject to abrogation by DKK1. Importantly, we found WNT16B plays a central role in promoting advanced malignancies particularly acquired resistance by counteracting cell death, an effect that can be minimized by a neutralizing antibody co-administered with classical chemotherapy. Furthermore, DNA damage-triggered expression of WNT16B is systemic, imaged by significant induction among diverse solid organs and circulation in peripheral blood, thereby holding promise as not only a TME-derived anticancer target but also a novel biomarker for clinical evaluation of treatment efficacy. Overall, our study substantiates the biological complexity and pathological implication of a therapy-activated TME, and provides the proof of principle of co-targeting tumor and the TME to prevent acquired resistance, with the aim of improving intervention outcome in an era of precision medicine.

Wnt/β-catenin signaling modulates human airway sensitization induced by β2-adrenoceptor stimulation

Background

Regular use of β₂-agonists may enhance non-specific airway responsiveness. The wingless/integrated (Wnt) signaling pathways are responsible for several cellular processes, including airway inflammation and remodeling while cAMP–PKA cascade can activate the Wnt signaling. We aimed to investigate whether the Wnt signaling pathways are involved in the bronchial hyperresponsiveness induced by prolonged exposure to β₂-adrenoceptor agonists in human isolated airways.

Methods

Bronchi were surgically removed from 44 thoracic surgery patients. After preparation, bronchial rings and primary cultures of bronchial epithelial cells were incubated with fenoterol (0.1 µM, 15 hours, 37°C), a β₂-agonist with high intrinsic efficacy. The effects of inhibitors/blockers of Wnt signaling on the fenoterol-induced airway sensitization were examined and the impact of fenoterol exposure on the mRNA expression of genes interacting with Wnt signaling or cAMP–PKA cascade was assessed in complete bronchi and in cultured epithelial cells.

Results

Compared to paired controls, fenoterol-sensitization was abolished by inhibition/blockage of the Wnt/β-catenin signaling, especially the cell-surface LRP5/6 co-receptors or Fzd receptors (1 µM SFRP1 or 1 µM DKK1) and the nuclear recruitment of TCF/LEF transcriptions factors (0.3 µM FH535). Wnt proteins secretion did not seem to be involved in the fenoterol-induced sensitization since the mRNA expression of Wnt remained low after fenoterol exposure and the inactivator of Wnt secretion (1 µM IWP2) had no effect on the fenoterol-sensitization. Fenoterol exposure did not change the mRNA expression of genes regulating Wnt signaling or cAMP–PKA cascade.

Conclusions

Collectively, our pharmacological investigations indicate that fenoterol-sensitization is modulated by the inhibition/blockage of canonical Wnt/β-catenin pathway, suggesting a phenomenon of biased agonism in connection with the β₂-adrenoceptor stimulation. Future experiments based on the results of the present study will be needed to determine the impact of prolonged fenoterol exposure on the extra- and intracellular Wnt signaling pathways at the protein expression level.

DNA methyltransferase inhibitor-mediated apoptosis in the Wnt/β-catenin signal pathway in a renal cell carcinoma cell line

The Wnt signaling pathway is activated in most cancer types when Wnt antagonist genes are inactivated. Glycogen synthase kinase 3 ( GSK3β) is an important regulator of the Wnt/β-catenin signaling pathway. The mechanisms underlying GSK3β regulation of neoplastic transformation and tumor development are unclear. Studies have raised the possibility that the Wnt signaling pathway may be implicated in renal cell carcinoma (RCC). Therefore, in the present study, we hypothesize that the expression and methylation status of the secreted frizzled-related protein 2 ( sFRP2) gene, one of the secreted antagonists that bind Wnt protein, and re-expression of this gene with the demethylation agent (5-aza-2′-deoxycytidine; DAC) may induce apoptosis in RCC cells. To test this hypothesis, we investigated the relationship among epigenetic inactivation of sFRP2 and p-GSK3β (Ser9) and other Wnt antagonists ( sFRP1, DKK3, WIF-1) and apoptotic factors ( Bax and Caspase3) as well as the anti-apoptotic factor BCL2. Our results indicate that DAC-mediated inhibition of DNA methylation led to a re-activation of sFRP2 expression and increased expression levels of the Wnt antagonists and apoptotic factors. In contrast, the level of β-catenin (CTNNB1) expression decreased. The p-GSK3β (Ser9) protein level in Caki-2 cells was significantly down-regulated, while the DNA fragmentation rate increased after treatment with 5 μM DAC at 96 h. Our data show that sFRP2 functions as a tumor suppressor gene in RCC and that its restoration may offer a new therapeutic approach for the treatment of RCC. Moreover, our study draws attention to the regulatory features of epigenetic molecules and analyses their underlying molecular mechanisms of action and their potential use in clinical practice.

Ovatodiolide Targets β -Catenin Signaling in Suppressing Tumorigenesis and Overcoming Drug Resistance in Renal Cell Carcinoma

Dysregulated β-catenin signaling is intricately involved in renal cell carcinoma (RCC) carcinogenesis and progression. Determining potential β-catenin signaling inhibitors would be helpful in ameliorating drug resistance in advanced or metastatic RCC. Screening for β-catenin signaling inhibitors involved in silico inquiry of the PubChem Bioactivity database followed by TCF/LEF reporter assay. The biological effects of ovatodiolide were evaluated in 4 RCC cell lines in vitro and 2 RCC cell lines in a mouse xenograft model. The synergistic effects of ovatodiolide and sorafenib or sunitinib were examined in 2 TKI-resistant RCC cell lines. Ovatodiolide, a pure compound of Anisomeles indica, inhibited β-catenin signaling and reduced RCC cell viability, survival, migration/invasion, and in vitro cell or in vivo mouse tumorigenicity. Cytotoxicity was significantly reduced in a normal kidney epithelial cell line with the treatment. Ovatodiolide reduced phosphorylated β-catenin (S552) that inhibited β-catenin nuclear translocation. Moreover, ovatodiolide decreased β-catenin stability and impaired the association of β-catenin and transcription factor 4. Ovatodiolide combined with sorafenib or sunitinib overcame drug resistance in TKI-resistant RCC cells. Ovatodiolide may be a potent β-catenin signaling inhibitor, with synergistic effects with sorafenib or sunitinib, and therefore, a useful candidate for improving RCC therapy.

WNT10A plays an oncogenic role in renal cell carcinoma by activating WNT/β-catenin pathway

Renal cell carcinoma (RCC) is a malignancy with poor prognosis. WNT/β-catenin signaling dysregulation, especially β-catenin overactivation and WNT antagonist silencing, is associated with RCC carcinogenesis and progression. However, the role of WNT ligands in RCC has not yet been determined. We screened 19 WNT ligands from normal kidney and RCC cell lines and tissues and found that WNT10A was significantly increased in RCC cell lines and tissues as compared to that in normal controls. The clinical significance of increase in WNT10A was evaluated by performing an immunohistochemical association study in a 19-year follow-up cohort comprising 284 RCC and 267 benign renal disease (BRD) patients. The results of this study showed that WNT10A was dramatically upregulated in RCC tissues as compared to that in BRD tissues. This result suggests that WNT10A, nuclear β-catenin, and nuclear cyclin D1 act as independent risk factors for RCC carcinogenesis and progression, with accumulative risk effects. Molecular validation of cell line models with gain- or loss-of-function designs showed that forced WNT10A expression induced RCC cell proliferation and aggressiveness, including higher chemoresistance, cell migration, invasiveness, and cell transformation, due to the activation of β-catenin-dependent signaling. Conversely, WNT10A siRNA knockdown decreased cell proliferation and aggressiveness of RCC cells. In conclusion, we showed that WNT10A acts as an autocrine oncogene both in RCC carcinogenesis and progression by activating WNT/β-catenin signaling.