Cytoskeleton-associated Protein 4 Research Articles

The Role of Serum Dickkopf1 and CKAP4 Levels in Diagnosing Colorectal Cancer and Measuring the Disease Severity: A Prospective Study.

Background and Objective: Colorectal cancer (CRC) is among the most common types of cancer. Although the disease is treatable in its early stages, five-year survival falls below 20% in the later stages. CEA and CA19-9 are tumor markers used in the diagnosis and follow-up of the disease in clinical practice; however, their diagnostic effectiveness is insufficient. Therefore, the identification of biomarkers that can be easily studied from serum and can diagnose CRC and determine its severity is highly important. In this context, dickkopf1 (DKK1) and cytoskeleton-associated protein 4 (CKAP4) are both promising biomarkers. Materials and Methods: Serum DKK1 and CKAP4 levels were measured in 55 patients with CRC and 40 healthy controls. The patients with CRC were divided into groups based on pathological stages and histological differentiation. The serum levels of both proteins in patients with CRC were measured preoperatively and 10 and 30 days postoperatively. Results: Serum DKK1 and CKAP4 were significantly higher in the CRC group than in the healthy controls (p < 0.05). Serum levels of both proteins rose in line with the disease stage and grade but decreased following surgical resection. A positive correlation was observed between tumor diameter and protein blood levels. The diagnostic efficacy of DKK1 and CKAP4 in CRC (approximately 95%) was higher than that of markers such as CEA and CA19-9. Conclusions: The DKK1 and CKAP4 serum values of patients with CRC are promising biomarkers. They can potentially be used in CRC management, namely, in the diagnosis and treatment of tumor response access and in tumor aggressiveness prediction.

DKK1 Activates the PI3K/AKT Pathway via CKAP4 to Balance the Inhibitory Effect on Wnt/β-Catenin Signaling and Regulates Wnt3a-Induced MSC Migration.

Wnt/β-catenin signaling plays a crucial role in the migration of mesenchymal stem cells (MSCs). However, our study has revealed an intriguing phenomenon where Dickkopf-1 (DKK1), an inhibitor of Wnt/β-catenin signaling, promotes MSC migration at certain concentrations ranging from 25 to 100 ng/mL while inhibiting Wnt3a-induced MSC migration at a higher concentration (400 ng/mL). Interestingly, DKK1 consistently inhibited Wnt3a-induced phosphorylation of LRP6 at all concentrations. We further identified cytoskeleton-associated protein 4 (CKAP4), another DKK1 receptor, to be localized on the cell membrane of MSCs. Overexpressing the CRD2 deletion mutant of DKK1 (ΔCRD2), which selectively binds to CKAP4, promoted the accumulation of active β-catenin (ABC), the phosphorylation of AKT (Ser473) and the migration of MSCs, suggesting that DKK1 may activate Wnt/β-catenin signaling via the CKAP4/PI3K/AKT cascade. We also investigated the effect of the CKAP4 intracellular domain mutant (CKAP4-P/A) that failed to activate the PI3K/AKT pathway and found that CKAP4-P/A suppressed DKK1 (100 ng/mL)-induced AKT activation, ABC accumulation, and MSC migration. Moreover, CKAP4-P/A significantly weakened the inhibitory effects of DKK1 (400 ng/mL) on Wnt3a-induced MSC migration and Wnt/β-catenin signaling. Based on these findings, we propose that DKK1 may activate the PI3K/AKT pathway via CKAP4 to balance the inhibitory effect on Wnt/β-catenin signaling and thus regulate Wnt3a-induced migration of MSCs. Our study reveals a previously unrecognized role of DKK1 in regulating MSC migration, highlighting the importance of CKAP4 and PI3K/AKT pathways in this process.

LRRC59 promotes the progression of oral squamous cell carcinoma by interacting with SRP pathway components and enhancing the secretion of CKAP4-containing exosomes

BackgroundAs a ribosome receptor, LRRC59 was thought to regulate mRNA translation on the ER membrane. Evidence suggests that LRRC59 is overexpressed in a number of human malignancies and is associated with poor prognoses, but its primary biological function in the development of oral squamous cell carcinoma (OSCC) remains obscure. ObjectiveThe purpose of this study is to investigate at the expression changes and functional role of LRRC59 in OSCC. MethodsLRRC59 gene expression and correlation with prognosis of OSCC patients were first examined using the data from The Cancer Genome Atlas (TCGA) databases. Following that, a series of functional experiments, including cell counting kit-8, cell cycle analysis, wound healing assays, and transwell assays, were carried out to analyze the biological roles of LRRC59 in tumor cells. Mechanistically, we employed Tandem Affinity Purification-Mass Spectrometry (TAP-MS) approach to isolate and identify protein complexes of LRRC59. Downstream regulatory proteins of LRRC59 were verified through immunoprecipitation and immunofluorescence experiments. Furthermore, we isolated exosomes from OSCC cell supernatant and conducted co-culture experiments to examine the effect of LRRC59 knockdown on OSCC cells. ResultsIn samples from OSCC patients, LRRC59 was highly expressed and correlated with poor prognoses. Moreover, the gene sets analysis based on TCGA RNA-seq data indicated that LRRC59 seemed to be strongly related with protein secretory and OSCC migration. Upregulated levels of LRRC59 are more prone to lymph node metastasis in OSCC patients. LRRC59 knockdown impaired the ability of OSCC cell proliferation, migration, and invasion invitro. Mechanistically, our TAP-MS data situate LRRC59 in a functional nexus for mRNA translation regulation via interactions with SRP pathway components, translational initiation factors, CRD-mediated mRNA stabilization factors. More importantly, we found that LRRC59 interacted with cytoskeleton-associated protein 4 (CKAP4) and promoted the formation of CKAP4-containing exosomes. We also revealed that the LRRC59-CKAP4 axis was a crucial regulator of CKAP4-containing exosome secretion in OSCC cells for migration and invasion. ConclusionsTherefore, based on our findings, LRRC59 may serve as a potential biomarker for OSCC patients, and LRRC59-induced exosome secretion via the CKAP4 axis may serve as a potential therapeutic target for OSCC.

Transcriptional profiles associated with coronary artery disease in type 2 diabetes mellitus.

Coronary artery disease (CAD) is a common complication of Type 2 diabetes mellitus (T2DM). Understanding the pathogenesis of this complication is essential in both diagnosis and management. Thus, this study aimed to characterize the presence of CAD in T2DM using molecular markers and pathway analyses. The study is a sex- and age-frequency matched case-control design comparing 23 unrelated adult Filipinos with T2DM-CAD to 23 controls (DM with CAD). Healthy controls served as a reference. Total RNA from peripheral blood mononuclear cells (PBMCs) underwent whole transcriptomic profiling using the Illumina HumanHT-12 v4.0 expression beadchip. Differential gene expression with gene ontogeny analyses was performed, with supporting correlational analyses using weighted correlation network analysis (WGCNA). The study observed that 458 genes were differentially expressed between T2DM with and without CAD (FDR<0.05). The 5 top genes the transcription factor 3 (TCF3), allograft inflammatory factor 1 (AIF1), nuclear factor, interleukin 3 regulated (NFIL3), paired immunoglobulin-like type 2 receptor alpha (PILRA), and cytoskeleton-associated protein 4 (CKAP4) with AUCs >89%. Pathway analyses show differences in innate immunity activity, which centers on the myelocytic (neutrophilic/monocytic) theme. SNP-module analyses point to a possible causal dysfunction in innate immunity that triggers the CAD injury in T2DM. The study findings indicate the involvement of innate immunity in the development of T2DM-CAD, and potential immunity markers can reflect the occurrence of this injury. Further studies can verify the mechanistic hypothesis and use of the markers.

Regulation of Cellular Signaling with an Aptamer Inhibitor to Impede Cancer Metastasis.

Tumor invasion and metastasis are the main causes of tumor progression and are the leading causes of death among cancer patients. In the present study, we propose a strategy to regulate cellular signaling with a tumor metastasis-relevant cytoskeleton-associated protein 4 (CKAP4) specific aptamer for the achievement of tumor metastasis inhibition. The designed aptamer could specifically bind to CKAP4 in the cell membranes and cytoplasm to block the internalization and recycling of α5β1 integrin, resulting in the disruption of the fibronectin-dependent cell adhesion and the weakening of the cell traction force. Moreover, the aptamer is able to impede the interaction between CKAP4 and Dickkopf1 (DKK1) to further block the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway, which subsequently reduces AKT phosphorylation and inhibits the reorganization of the actin cytoskeleton in cell migration. The synergetic function of the designed aptamer in inhibiting cancer cell adhesion and blocking the PI3K signaling pathway enables efficient tumor cell metastasis suppression. The aptamer with specific targeting ability in regulating cellular signaling paves the way for cancer treatment and further provides a guiding ideology for inhibiting tumor metastasis.

Invigorating human MSCs for transplantation therapy via Nrf2/DKK1 co-stimulation in an acute-on-chronic liver failure mouse model.

Since boosting stem cell resilience in stressful environments is critical for the therapeutic efficacy of stem cell-based transplantations in liver disease, this study aimed to establish the efficacy of a transient plasmid-based preconditioning strategy for boosting the capability of mesenchymal stromal cells (MSCs) for anti-inflammation/antioxidant defenses and paracrine actions in recipient hepatocytes. Human adipose mesenchymal stem cells (hADMSCs) were subjected to transfer, either with or without the nuclear factor erythroid 2-related factor 2 (Nrf2)/Dickkopf1 (DKK1) genes, followed by exposure to TNF-α/H2O2. Mouse models were subjected to acute chronic liver failure (ACLF) and subsequently injected with either transfected or untransfected MSCs. These hADMSCs and ACLF mouse models were used to investigate the interaction between Nrf2/DKK1 and the hepatocyte receptor cytoskeleton-associated protein 4 (CKAP4). Activation of Nrf2 and DKK1 enhanced the anti-stress capacity of MSCs in vitro. In a murine model of ACLF, transient co-overexpression of Nrf2 and DKK1 via plasmid transfection improved MSC resilience against inflammatory and oxidative assaults, boosted MSC transplantation efficacy, and promoted recipient liver regeneration due to a shift from the activation of the anti-regenerative IFN-γ/STAT1 pathway to the pro-regenerative IL-6/STAT3 pathway in the liver. Importantly, the therapeutic benefits of MSC transplantation were nullified when the receptor CKAP4, which interacts with DKK1, was specifically removed from recipient hepatocytes. However, the removal of the another receptor low-density lipoprotein receptor-related protein 6 (LRP6) had no impact on the effectiveness of MSC transplantation. Moreover, in long-term observations, no tumorigenicity was detected in mice following transplantation of transiently preconditioned MSCs. Co-stimulation with Nrf2/DKK1 safely improved the efficacy of human MSC-based therapies in murine models of ACLF through CKAP4-dependent paracrine mechanisms.

The clinical significance and diagnostic value of serum Dickkopf1 and CKAP4 levels in patients with gastric cancer: a prospective study.

Gastric cancer is diagnosed at an advanced stage in most patients, and the prognosis is poor. Novel biochemical markers of high diagnostic value for the detection of the disease are therefore important. Dickkopf1 (DKK1) and cytoskeleton-associated protein 4 (CKAP4) have been extensively studied as biomarkers in cancer patients. Serum DKK1 and CKAP4 levels in 58 patients with gastric cancer and 41 healthy controls were examined using an ELISA kit in this prospective study. The patients were subdivided into groups based on pathological TNM staging and histological grades. Serum levels of both proteins in the patients with gastric cancer were measured preoperatively, 10 and 30 days after surgery. Serum DKK1 and CKAP4 levels were significantly higher in the gastric cancer group compared to the healthy controls (p<0.05). Serum levels of both proteins increased in line with the pathological stage and histological grade of the gastric cancer. Serum CKAP4 and DKK1 levels decreased after surgical resection. Both serum levels also decreased significantly on day 30 after surgery compared to day 10 (p<0.05). Serum carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) positivity rates were below 20% in the gastric cancer group, while the diagnostic value (sensitivity and specificity) of serum CKAP-4 and DKK1 exceeded 80%. DKK1 and CKAP4 are biomarkers of high diagnostic value that can be used to diagnose and predict the severity of gastric cancer. These proteins can also be employed for disease monitoring after surgical resection. The diagnostic value of these proteins is higher than that of biomarkers such as CEA and CA19-9, which are routinely used in clinical practice.

Expression of cytoskeleton-associated protein 4 is associated with poor prognosis and metastasis in nasopharyngeal carcinoma.

Cytoskeleton-associated protein 4 (CKAP4) acts as a key transmembrane protein that connects the endoplasmic reticulum (ER) to microtubule dynamics. Researchers have not examined the roles of CKAP4 in nasopharyngeal carcinoma (NPC). The study aimed at evaluating the prognostic value and metastasis-regulating effect of CKAP4 in NPC. CKAP4 protein could be observed in 86.36% of 557 NPC specimens but not in normal nasopharyngeal epithelial tissue. According to immunoblot assays, NPC cell lines presented high CKAP4 expression relative to NP69 immortalized nasopharyngeal epithelial cells. Moreover, CKAP4 was highly expressed at the NPC tumor front and in matched liver, lung, and lymph node metastasis samples. Furthermore, high CKAP4 expression reported poor overall survival (OS) and presented a positive relevance to tumor (T) classification, recurrence, and metastasis. According to multivariate analysis, CKAP4 could independently and negatively predict patients' prognosis. Stable knockdown of CKAP4 expression in NPC cells inhibited cell migration, invasion and metastasis in vitro and in vivo. Moreover, CKAP4 promoted epithelial-mesenchymal transition (EMT) in NPC cells. CKAP4 knockdown was followed by the downregulation of the interstitial marker vimentin, and upregulation of the epithelial marker E-cadherin. In NPC tissues, high CKAP4 expression exhibited a positive relevance to vimentin expression and a negative relevance to E-cadherin expression. In conclusion, CKAP4 is an independent predictor of NPC, and CKAP4 might contribute NPC progression and metastasis, which may be involved in EMT with vimentin and E-cadherin.

A network map of cytoskeleton-associated protein 4 (CKAP4) mediated signaling pathway in cancer.

Cytoskeleton-associated protein 4 (CKAP4) is a non-glycosylated type II transmembrane protein that serves as a cell surface-activated receptor. It is expressed primarily in the plasma membranes of bladder epithelial cells, type II alveolar pneumocytes, and vascular smooth muscle cells. CKAP4 is involved in various biological activities including cell proliferation, cell migration, keratinocyte differentiation, glycogenesis, fibrosis, thymic development, cardiogenesis, neuronal apoptosis, and cancer. CKAP4 has been described as a pro-tumor molecule that regulates the progression of various cancers, including lung cancer, breast cancer, esophageal squamous cell carcinoma, hepatocellular carcinoma, cervical cancer, oral cancer, bladder cancer, cholangiocarcinoma, pancreatic cancer, myeloma, renal cell carcinoma, melanoma, squamous cell carcinoma, colorectal cancer, and osteosarcoma. CKAP4 and its isoform bind to DKK1 or DKK3 (Dickkopf proteins) or antiproliferative factor (APF) and regulates several downstream signaling cascades. The CKAP4 complex plays a crucial role in regulating the signaling pathways including PI3K/AKT and MAPK1/3. Recently, CKAP4 has been recognized as a potential target for cancer therapy. Due to its biomedical importance, we integrated a network map of CKAP4. The available literature on CKAP4 signaling was manually curated according to the NetPath annotation criteria. The consolidated pathway map comprises 41 activation/inhibition events, 21 catalysis events, 35 molecular associations, 134 gene regulation events, 83 types of protein expression, and six protein translocation events. CKAP4 signaling pathway map data is freely accessible through the WikiPathways Database ( https://www.wikipathways.org/index.php/Pathway:WP5322 ). Generation of CKAP4 signaling pathway map.

Formin-like 2 promotes angiogenesis and metastasis of colorectal cancer by regulating the EGFL6/CKAP4/ERK axis.

Increasing evidence indicates that angiogenesis plays a pivotal role in tumor progression. Formin-like 2 (FMNL2) is well-known for promoting metastasis; however, the molecular mechanisms by which FMNL2 promotes angiogenesis in colorectal cancer (CRC) remain unclear. Here, we found that FMNL2 promotes angiogenesis and metastasis of CRC in vitro and in vivo. The GDB/FH3 domain of FMNL2 directly interacts with epidermal growth factor-like protein 6 (EGFL6). Formin-like 2 promotes EGFL6 paracrine signaling by exosomes to regulate angiogenesis in CRC. Cytoskeleton associated protein 4 (CKAP4) is a downstream target of EGFL6 and is involved in CRC angiogenesis. Epidermal growth factor-like protein 6 binds to the N-terminus of CKAP4 to promote the migration of HUVECs by activating the ERK/MMP pathway. These findings suggest that FMNL2 promotes the migration of HUVECs and enhances angiogenesis and tumorigenesis in CRC by regulating the EGFL6/CKAP4/ERK axis. Therefore, the EGFL6/CKAP4/ERK axis could be a candidate therapeutic target for CRC treatment.

DKK1 Promotes Tumor Immune Evasion and Impedes Anti-PD-1 Treatment by Inducing Immunosuppressive Macrophages in Gastric Cancer.

Tumor-associated macrophages (TAM) have key functions in promoting a suppressive tumor immune microenvironment (TIME) and immune evasion, which largely limit treatment effects of immune-checkpoint inhibitors (ICI) in different cancers, including gastric cancer. Dickkopf-1 (DKK1) is associated with tumor progression and has been shown to negatively regulate antitumor immunity, but the impact of DKK1 on the TIME remains incompletely understood. Here, we found that tumoral DKK1 expression is closely associated with worse survival and a suppressive TIME in gastric cancer patients. Results from in vitro coculture assays suggested that DKK1 induces macrophages to become immunosuppressive, thereby inhibiting antitumor responses of CD8+ T cells and natural killer (NK) cells. In vivo DKK1 blockade in syngeneic gastric cancer mouse models reprogramed TAMs to restore the immune activity in the TIME and triggered significant tumor regression. DKK1 blockade also directly reduced the growth of human gastric cancer tumors with high DKK1 expression in a xenograft model. Mechanistically, DKK1 interacted with cytoskeleton-associated protein 4 (CKAP4) on the macrophage surface and activated downstream PI3K-AKT signaling, which contributed to immune suppression. TAM reprogramming by DKK1 blockade also augmented the efficacy of programmed cell death protein-1 (PD-1) blockade in gastric cancer models. Therefore, our study provides novel insights into the role of DKK1 on tumor-intrinsic, innate, and adaptive antitumor immunity modulation and suggests that DKK1 is a promising immunotherapeutic target for enhanced PD-1 blockade therapy in gastric cancer.

DKK3/CKAP4 axis is associated with advanced stage and poorer prognosis in oral cancer.

We previously reported that dickkopf WNT signaling inhibitor 3 (DKK3) would modulate malignant potential of oral squamous cell carcinoma (OSCC) via activating Akt. Recently, cytoskeleton associated protein 4 (CKAP4) functions as receptor of DKK3, which activates Akt in esophageal squamous cell carcinoma, but its expression and function in OSCC were unclear. We studied DKK3 and CKAP4 protein expression in OSCC tissue and investigated the correlation between protein expression and clinical data. We also investigated whether antibodies (Ab) for DKK3 or CKAP4 could suppress malignant potential of the cancer cells. DKK3/CKAP4 protein expression was observed in majority of OSCC cases and was associated with significantly higher T-stage and TNM stage. Multivariate analysis revealed that DKK3 and CKAP4 were independent prognostic biomarkers for overall survival (OS) and disease-free survival (DFS), respectively. Survival analyses revealed that DKK3-positive cases and CKAP4-positive cases showed significantly shorter OS and DFS, respectively, and that DKK3/CKAP4 double-negative cases showed significantly favorable prognosis. Both anti-DKK3Ab and anti-CKAP4Ab could suppress cancer cell proliferation, migration, and invasion. DKK3/CKAP4 axis is thought to be important in OSCC, and it would be a promising therapeutic target.

Elucidation of CKAP4-remodeled cell mechanics in driving metastasis of bladder cancer through aptamer-based target discovery

Metastasis contributes to the dismal prognosis of bladder cancer (BLCA). The mechanical status of the cell membrane is expected to mirror the ability of cell migration to promote cancer metastasis. However, the mechanical characteristics and underlying molecular profile associated with BLCA metastasis remain obscure. To study the unique cellular architecture and traits associated with cell migration, using a process called cell-based systematic evolution of ligands by exponential enrichment (cell-SELEX) we generated an aptamer-based molecular probe, termed spl3c, which identified cytoskeleton-associated protein 4 (CKAP4). CKAP4 was associated with tumor metastasis in BLCA, but we also found it to be a mechanical regulator of BLCA cells through the maintenance of a central-to-peripheral gradient of stiffness on the cell membrane. Notably, such mechanical traits were transportable through exosome-mediated intercellular CKAP4 trafficking, leading to significant enhancement of migration in recipient cells and, consequently, aggravating metastatic potential in vivo. Taken together, our study shows the robustness of this aptamer-based molecular tool for biomarker discovery, revealing the dominance of a CKAP4-induced central-to-peripheral gradient of membrane stiffness that benefits cell migration and delineating the role of exosomes in mediating mechanical signaling in BLCA metastasis.

GOLPH3/CKAP4 promotes metastasis and tumorigenicity by enhancing the secretion of exosomal WNT3A in non-small-cell lung cancer

Cancer metastasis is the main cause of mortality associated with non-small-cell lung cancer (NSCLC), accounting for up to 70% of deaths among patients. The mechanisms underlying distal metastasis remain largely unknown. Golgi phosphoprotein 3 (GOLPH3) correlates negatively with overall survival in multiple tumors. In this study, we evaluated the function of GOLPH3 in NSCLC distal metastasis. GOLPH3 was expressed at high levels in samples from patients with NSCLC and was positively associated with clinicopathologic characteristics including clinical stage (P < 0.001), T (P = 0.001), N (P = 0.007), and M (P = 0.001) classification. Functionally, Transwell and wound-healing assays suggested that GOLPH3 overexpression enhances NSCLC cell migration and invasion abilities. Tumor-sphere formation and flow cytometry assays demonstrated that GOLPH3 overexpression enhances a stem cell-like phenotype of NSCLC cells. Metastasis models established by tail vein and intracardiac injection confirmed the pro-metastatic function of GOLPH3 in vivo. A subcutaneous tumor formation model confirmed that GOLPH3 overexpression increased the tumorigenicity of NSCLC cells. Mechanistically, gene set enrichment analysis revealed a positive association of GOLPH3 mRNA expression with WNT-activated gene signatures. Luciferase-reporter and nuclear extract assays showed that GOLPH3 overexpression enhances metastasis and tumorigenicity through activation of the WNT/β-catenin pathway. Immunoprecipitation-mass spectrometry and gene ontology analysis demonstrated that GOLPH3 interacts with cytoskeleton-associated protein 4 (CKAP4) in exosome-mediated distal metastasis. We found that GOLPH3 decreased the amount of plasma membrane-localized CKAP4 and increased the amount of exosome-localized CKAP4 to promote the formation of CKAP4-containing exosomes. Furthermore, we demonstrated that CKAP4 binds exosomal WNT3A to enhance its secretion. Therefore, the GOLPH3/CKAP4 axis plays a crucial role in promoting exosomal-WNT3A secretion to enhance and maintain the stem-like phenotype and metastasis in NSCLC, thus indicating the therapeutic potential of GOLPH3 in patients with NSCLC metastasis.

Cytoskeleton-associated protein 4 (CKAP4) promotes malignant progression of human gliomas through inhibition of the Hippo signaling pathway.

Gliomas are the most common and aggressive malignant brain tumors and are associated with high mortality and incidence in humans. Despite rigorous multi-modal therapy, including surgery, chemotherapy and radiotherapy, patients with malignant glioma survive an average of 12-15months following primary diagnosis. Therefore, new molecular biomarkers are urgently needed for diagnosis and targeted therapy. Here, we find that suppression of CKAP4 might inhibit glioma growth through regulation of Hippo signaling. We examined the expression levels of CKAP4 through analysis of RNA sequencing data from GEPIA and CGGA databases. Then, Lentivirus was used toconstruct stable cell lines with knockout or overexpression of CKAP4. Next, the function of CKAP4 on glioma was investigated in vitro and in an orthotopic brain tumor model in mice. Lastly, luciferase reporter assay, immunofluorescence and immunoblotting were performed to explore the potential mechanism of how CKAP4 affects gliomas. CKAP4 is highly upregulated in glioma and high CKAP4 expressing tumors were associated with poor patient survival. And CKAP4 promotes malignant progression of gliomas via inhibiting Hippo signaling. CKAP4 has potential as a promising biomarker and can predict the prognosis of patients with gliomas. And targeting CKAP4 expression may be an effective therapeutic strategy for the treatment of human gliomas.

The Dickkopf1 and FOXM1 positive feedback loop promotes tumor growth in pancreatic and esophageal cancers

Dickkopf1 (DKK1) is overexpressed in various cancers and promotes cancer cell proliferation by binding to cytoskeleton-associated protein 4 (CKAP4). However, the mechanisms underlying DKK1 expression are poorly understood. RNA sequence analysis revealed that expression of the transcription factor forkhead box M1 (FOXM1) and its target genes concordantly fluctuated with expression of DKK1 in pancreatic ductal adenocarcinoma (PDAC) cells. DKK1 knockdown decreased FOXM1 expression and vice versa in PDAC and esophageal squamous cell carcinoma (ESCC) cells. Inhibition of either the DKK1-CKAP4-AKT pathway or the ERK pathway suppressed FOXM1 expression, and simultaneous inhibition of both pathways showed synergistic effects. A FOXM1 binding site was identified in the 5ʹ-untranslated region of the DKK1 gene, and its depletion decreased DKK1 expression and cancer cell proliferation. Clinicopathological and database analysis revealed that PDAC and ESCC patients who simultaneously express DKK1 and FOXM1 have a poorer prognosis. Multivariate analysis demonstrated that expression of both DKK1 and FOXM1 is the independent prognostic factor in ESCC patients. Although it has been reported that FOXM1 enhances Wnt signaling, FOXM1 induced DKK1 expression independently of Wnt signaling in PDAC and ESCC cells. These results suggest that DKK1 and FOXM1 create a positive feedback loop to promote cancer cell proliferation.

Plasmalemma vesicle-associated protein promotes angiogenesis in cholangiocarcinoma via the DKK1/CKAP4/PI3K signaling pathway.

Cholangiocarcinoma (CCA) is aggressive and has poor clinical outcomes because of typically delayed diagnosis and a lack of effective non-surgical therapeutic options. Recent studies have shown that plasmalemma vesicle-associated protein (PLVAP) is related to angiogenesis in various tumors, and in vivo PLVAP targeting therapy has been proven effective against hepatocellular carcinoma and pancreatic cancer. The goal of this study was to determine the potential therapeutic utility of targeting PLVAP and thus angiogenesis in CCA and explore the underlying molecular mechanisms. We found that the PLVAP expression levels were significantly higher in CCA tissues when compared with matched adjacent non-tumor tissues obtained from a total of 90 CCA patients; higher expression levels of PLVAP were associated with shorter overall survival of patients. In addition, overexpression of PLVAP was associated with higher micro-vessel density in CCA tissues. In a PLVAP overexpressing CCA patient-derived xenograft model, a novel humanized anti-PLVAP antibody in combination with Gemcitabine plus Cisplatin was significantly inhibited tumor growth. Molecular analysis of CCA cells co-cultured with human umbilical vascular endothelial cells or human hepatic sinusoidal endothelial cells showed that Dickkopf-related protein 1 (DKK1) secreted by CCA cells activated the PI3K/Akt pathway after binding to its receptor, cytoskeleton-associated protein 4 (CKAP4), resulting in the upregulation of PLVAP. Thus, CCA cells increased the angiogenic potency of endothelial cells in a paracrine fashion. Consistently, patients bearing CKAP4 and PLVAP overexpressing tumors had a poor prognosis. In conclusion, the DKK1/CKAP4/PI3K/PLVAP pathway increases angiogenesis in CCA and is therefore a potential anti-angiogenic target.

Single-cell RNA Sequencing Analysis Identifies Key Genes in Brain Metastasis from Lung Adenocarcinoma.

Lung adenocarcinoma (LADC) is the most common type of lung cancer and is a subtype of non-small-cell lung cancer (NSCLC). Approximately 40% of LADC patients experience brain metastases (BMs) during the course of the disease. In this study, integrated bioinformatics methods were applied to identify key genes related to brain metastasis in lung adenocarcinoma. We derived and characterized genes differentially expressed between the primary tumour and brain metastases using tumour cells isolated from two lung cancer Patient-derived xenografts (PDX) cases (GSE 69405). Gene ontology (GO) and KEGG pathway enrichment analyses were applied, and protein-protein interaction (PPI) networks and Cytoscape software were utilized to identify key genes. Four key genes, including CKAP4 (Cytoskeleton Associated Protein 4), SERPINA1 (Serpin Family A Member 1), SDC2 (Syndecan 2) and GNG11 (G Protein Subunit Gamma 11) were identified for BM-LADC by the Venn diagram. We believe these key genes may be potential biomarkers for improved prognosis and treatment of lung adenocarcinoma.

Cytoskeleton-Associated Protein 4, a Promising Biomarker for Tumor Diagnosis and Therapy.

Cytoskeleton-associated protein 4 (CKAP4) is located in the rough endoplasmic reticulum (ER) and plays an important role in stabilizing the structure of ER. Meanwhile, CKAP4 is also found to act as an activated receptor at the cell surface. The multifunction of CKAP4 was gradually discovered with growing research evidence. In addition to the involvement in various physiological events including cell proliferation, cell migration, and stabilizing the structure of ER, CKAP4 has been implicated in tumorigenesis. However, the role of CKAP4 is still controversial in tumor biology, which may be related to different signal transduction pathways mediated by binding to different ligands in various microenvironments. Interestingly, CKAP4 has been recently recognized as a serological marker of several tumors and CKAP4 is expected to be a tumor therapeutic target. Therefore, deciphering the gene status, expression regulation, functions of CKAP4 in different diseases may shed new light on CKAP4-based cancer diagnosis and therapeutic strategy. This review discusses the publications that describe CKAP4 in various diseases, especially on tumor promotion and suppression, and provides a detailed discussion on the discrepancy.

Palmitoylated CKAP4 regulates mitochondrial functions through an interaction with VDAC2 at ER-mitochondria contact sites.

Cytoskeleton-associated protein 4 (CKAP4) is a palmitoylated type II transmembrane protein localized to the endoplasmic reticulum (ER). Here, we found that knockout (KO) of CKAP4 in HeLaS3 cells induces the alteration of mitochondrial structures and increases the number of ER-mitochondria contact sites. To understand the involvement of CKAP4 in mitochondrial functions, the binding proteins of CKAP4 were explored, enabling identification of the mitochondrial porin voltage-dependent anion-selective channel protein 2 (VDAC2), which is localized to the outer mitochondrial membrane. Palmitoylation at Cys100 of CKAP4 was required for the binding between CKAP4 and VDAC2. In CKAP4 KO cells, the binding of inositol trisphosphate receptor (IP3R) and VDAC2 was enhanced, the intramitochondrial Ca2+ concentration increased and the mitochondrial membrane potential decreased. In addition, CKAP4 KO decreased the oxidative consumption rate, in vitro cancer cell proliferation under low-glucose conditions and in vivo xenograft tumor formation. The phenotypes were not rescued by expression of a palmitoylation-deficient CKAP4 mutant. These results suggest that CKAP4 plays a role in maintaining mitochondrial functions through the binding to VDAC2 at ER-mitochondria contact sites and that palmitoylation is required for this novel function of CKAP4.This article has an associated First Person interview with the first author of the paper.