Gene Summary

Gene:IQGAP1; IQ motif containing GTPase activating protein 1
Aliases: SAR1, p195, HUMORFA01
Summary:This gene encodes a member of the IQGAP family. The protein contains four IQ domains, one calponin homology domain, one Ras-GAP domain and one WW domain. It interacts with components of the cytoskeleton, with cell adhesion molecules, and with several signaling molecules to regulate cell morphology and motility. Expression of the protein is upregulated by gene amplification in two gastric cancer cell lines. [provided by RefSeq, Jul 2008]
Databases:OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:ras GTPase-activating-like protein IQGAP1
Source:NCBIAccessed: 31 August, 2019


What does this gene/protein do?
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Pathways:What pathways are this gene/protein implicaed in?
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Cancer Overview

Research Indicators

Publications Per Year (1994-2019)
Graph generated 31 August 2019 using data from PubMed using criteria.

Literature Analysis

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Tag cloud generated 31 August, 2019 using data from PubMed, MeSH and CancerIndex

Latest Publications: IQGAP1 (cancer-related)

Fan J, Zhang W, Wu Y, et al.
miR‑124 inhibits cell growth through targeting IQGAP1 in colorectal cancer.
Mol Med Rep. 2018; 18(6):5270-5278 [PubMed] Related Publications
MicroRNA (miRNA/miR)-124 is a miRNA, which exerts tumor suppressive effects but is frequently absent in tumors. Although it has been validated to target oncogenic genes such as signal transducer and activator of transcription 3, forkhead box Q1, and Slug, the mechanistic link between miR‑124 and potential target genes that contribute to tumor progression, is yet to be investigated. IQ motif containing GTPase activating protein 1 (IQGAP1) is a scaffold protein that participates in protein‑protein interactions and integrating diverse signaling pathways. Previous studies suggest that overexpression of IQGAP1 enhances activity of mitogen activated protein kinase 1 and β‑catenin signaling cascades to facilitate tumor progression. The present study aimed to identify the regulative link between miR‑124 and IQGAP1 in colorectal cancer (CRC). It was demonstrated that IQGAP1 was aberrantly overexpressed in CRC tissues and cell lines. Knockdown of IQGPA1 by introducing short hairpin‑IQGAP1 lentivirus inhibited CRC cell growth and colony formation ability, and simultaneously suppressed phosphorylation of extracellular signal‑regulated kinase (ERK)1/2 and β‑catenin expression. Furthermore, it was demonstrated that miR‑124 was silenced in CRC. Restoration of miR‑124 in CRC cells impeded cell growth and colony formation ability. The direct binding of miR‑124 to the 3'untranslated region of IQGAP1 mRNA was confirmed using a luciferase reporter gene assay. Importantly, downregulation of IQGAP1 expression was observed in miR‑124‑restoration cells with simultaneous reduction of phosphorylated‑ERK1/2 and β‑catenin. In conclusion, the present study describes a potential mechanism underlying the miR‑124/IQGAP1 link in CRC progression. Silencing of miR‑124 may depress IQGAP1 expression, leading to increased activity of ERK1/2 and β‑catenin signaling.

Razidlo GL, Burton KM, McNiven MA
Interleukin-6 promotes pancreatic cancer cell migration by rapidly activating the small GTPase CDC42.
J Biol Chem. 2018; 293(28):11143-11153 [PubMed] Free Access to Full Article Related Publications
Inflammation is a major driver of tumor progression and metastasis, although the mechanisms by which proinflammatory cytokines drive metastatic invasion are unknown. Interleukin-6 (IL-6) is a potent proinflammatory cytokine that is elevated in individuals with pancreatic cancer (PDAC), is required for PDAC progression in mice, and increases tumor cell invasion

Zeng F, Jiang W, Zhao W, et al.
Ras GTPase-Activating-Like Protein IQGAP1 (IQGAP1) Promotes Breast Cancer Proliferation and Invasion and Correlates with Poor Clinical Outcomes.
Med Sci Monit. 2018; 24:3315-3323 [PubMed] Free Access to Full Article Related Publications
BACKGROUND Breast cancer is one of the most common female cancers in the world. As a key integrator of cell signaling pathways, IQGAP1 contributes to the development and progression of several cancers. However, the exact effects and molecular mechanisms of IQGAP1 in breast cancer progression remain poorly understood. MATERIAL AND METHODS In the present study, IQGAP1 expression was measured in 96 paired breast cancer samples and the corresponding adjacent non-cancerous tissues by immunohistochemistry and quantitative polymerase chain reaction. To further explore the biological function of IQGAP1 in breast cancer cells, we knocked down IQGAP1 expression in MCF-7 cells and overexpressed it in SK-BR-3 cells. RESULTS IQGAP1 was specifically upregulated in breast cancer tissues compared with the corresponding adjacent non-cancerous tissues. Moreover, IQGAP1 expression was positively correlated with breast cancer survival rate. IQGAP1 also promoted breast cancer cell proliferation and cell cycle progression and suppressed apoptosis. CONCLUSIONS In conclusion, our results suggest that IQGAP1 plays an important role in the cell proliferation and invasion of human breast cancer cells, thus indicating that IQGAP1 may be a potential therapeutic target for the treatment of human breast cancer.

Naidu S, Shi L, Magee P, et al.
PDGFR-modulated miR-23b cluster and miR-125a-5p suppress lung tumorigenesis by targeting multiple components of KRAS and NF-kB pathways.
Sci Rep. 2017; 7(1):15441 [PubMed] Free Access to Full Article Related Publications
In NSCLC alterations in PDGF receptors are markers of worst prognosis and efficient targeting of these receptors is yet to be achieved. In this study, we explored PDGFR-regulated microRNAs demonstrating that miR-23b cluster and miR-125a-5p are downregulated by increased expression of PDGFR-α or PDGFR-β in NSCLC cells. Mechanistically, the expression of these microRNAs is positively regulated by p53 and negatively modulated by NF-kB p65. Forced expression of miR-23b cluster or miR-125a-5p enhanced drug sensitivity and suppressed invasiveness of NSCLC cells by silencing several genes involved in oncogenic KRAS and NF-kB pathways, including SOS1, GRB2, IQGAP1, RALA, RAF-1, IKKβ, AKT2, ERK2 and KRAS itself. Of note, an inverse correlation between miR-23b cluster, miR-125a-5p and respective target genes was also found in vivo in a large dataset of lung adenocarcinoma samples. Furthermore, in vivo delivery of miR-23b cluster or miR-125a-5p significantly repressed tumour growth in a highly aggressive NSCLC circulating tumour cell (CTC) patient derived explant (CDX) mouse model. In conclusion, our finding sheds light on the PDGFR signaling and endorses the possibility to employ miR-23b cluster and miR-125a-5p as therapeutic tools to silence simultaneously a range of redundant pathways and main effectors of tumorigenesis in NSCLC.

Lu B, Lian R, Wu Z, et al.
MTA1 promotes viability and motility in nasopharyngeal carcinoma by modulating IQGAP1 expression.
J Cell Biochem. 2018; 119(5):3864-3872 [PubMed] Related Publications
Nasopharyngeal carcinoma (NPC) is frequently seen in Chinese, especially the population that resides in southeast China. Metastasis-associated protein 1 (MTA1) is a chromatin modifier and plays a role in tumor cell metastasis. IQGAP1 is a ubiquitously expressed protein that contributes to cytoskeleton remodeling. This study aimed to investigate the role of MTA1 and IQGAP1 in NPC malignant transformation. MTA1 and IQGAP1 expression in NPC (n = 43) and control tissues (n = 31) were detected using qRT-PCR, immunoblot, and immunohistochemistry. MTA1 was overexpressed in CNE-1 and CNE-2 cell line by pcDNA3.1/MTA1 transfection. Dominant-negative p53 was transfected to inhibit p53 activity. si-IQGAP1 or dominant-negative IQGAP1 (IQGAP1ΔGRD) was used to suppress IQGAP1 activity. Cell proliferation was measured by CKK-8 assay. Cell migration was evaluated by Transwell assay. The results showed that MTA1 and IQGAP1 were highly expressed in NPC tissues compared with the controls. Forced expression of MTA1 accelerated cell proliferation and migration and upregulated IQGAP1 expression in a p53-independent way. Knockdown of IQGAP1 or transfection of dominant-negative IQGAP1 impeded tumor cell proliferation and migration as well as PI3K/Akt signaling induced by MTA1. In conclusion, MTA1 participates in NPC malignant transformation via regulating IQGAP1 expression and PI3K/Akt signaling pathway.

Kumar D, Hassan MK, Pattnaik N, et al.
Reduced expression of IQGAP2 and higher expression of IQGAP3 correlates with poor prognosis in cancers.
PLoS One. 2017; 12(10):e0186977 [PubMed] Free Access to Full Article Related Publications
IQGAPs is a family of proteins which comprises three members, in humans. The expression pattern and role of IQGAP1 has been well established in many cancers, whereas those of IQGAP2 and IQGAP3, have mostly remained unexplored. We used available large datasets, to explore the pan-cancer status of these two genes in-silico. Here we have analysed their mRNA expression and correlation with survivability in eight different cancers, including lung, breast, gastric, brain, colorectal, prostate, liver and kidney cancers and, their subtypes. The mRNA expression of IQGAP2 and IQGAP3 in individual cancers were analysed in two different publicly available databases viz. Oncomine and TCGA. The prognostic value of these genes in lung, breast and gastric cancer was analysed using Kaplan-Meier Plotter database, whereas for brain, colorectal, liver, prostate and kidney cancers, SurvExpress database was used. These results were validated by immunohistochemistry in cancer tissues (stomach, prostate, brain, colorectal). Moreover, we did IQGAP2 and IQGAP3 genomic alteration and, promoter methylation analysis using cBioportal and Wanderer web tool, respectively. Most of the cancer types (lung, breast, prostate, brain, gastric, liver, kidney and colorectal) showed increased IQGAP3 mRNA expression. In contrast, the IQGAP2 transcript levels were reduced across different cancers viz. lung, breast, gastric, liver, kidney and colorectal cancer. IQGAP2 expression correlated positively with survivability, on the contrary, IQGAP3 expression levels correlated inversely with survivability, in most of the cancers. Collectively, enhanced IQGAP3 and reduced IQGAP2 levels were frequently observed in multiple cancers with the former predicting poor survivability and the later opposite. Methylation pattern was significantly altered in most of the cancer types. We found copy no. variation and mutations in specific cancers, for IQGAP2 and IQGAP3. Our in-vivo (IHC) data confirmed the in-silico findings completely. Hence, IQGAP2 and IQGAP3 have potential to be used as prognostic markers or therapeutic targets in specific cancers.

Wang X, He C, Li C, et al.
IQGAP1 silencing suppresses the malignant characteristics of laryngeal squamous cell carcinoma cells.
Int J Biol Markers. 2018; 33(1):73-78 [PubMed] Related Publications
BACKGROUND: Laryngeal squamous cell carcinoma (LSCC) has a poor prognosis due to recurrence and metastasis. IQ-domain GTPase-activating protein 1 (IQGAP1), a scaffold protein, plays an important role in tumorigenesis and malignant development. In this study, we aimed to explore the role of IQGAP1 in LSCC.
METHODS: Expression of IQGAP1 in human LSCC specimens was assessed by immunohistochemistry. We also evaluated the roles of IQGAP1 in cell proliferation, migration and invasion and epithelial-to-mesenchymal transition (EMT) in Hep-2 cells.
RESULTS: The expression of IQGAP1 protein was significantly up-regulated in LSCC tissues compared with normal laryngeal tissues (p = 0.002). Furthermore, the knockdown of IQGAP1 in Hep-2 cells inhibited cell growth, migration and invasion. Moreover, we found that IQGAP1 silencing reversed EMT.
CONCLUSIONS: These results show for the first time that IQGAP1 is up-regulated in LSCC tissues and plays an important role in LSCC cell proliferation and invasiveness, which indicates that IQGAP1 could work as an oncogene and may serve as a promising molecular target for treatment of LSCC.

Lee BH, Neela PH, Kent MS, Zehnder AM
IQGAP1 is an oncogenic target in canine melanoma.
PLoS One. 2017; 12(4):e0176370 [PubMed] Free Access to Full Article Related Publications
Canine oral mucosal melanoma is an aggressive malignant neoplasm and is characterized by local infiltration and a high metastatic potential. The disease progression is similar to that of human oral melanomas. Whereas human cutaneous melanoma is primarily driven by activating mutations in Braf (60%) or Nras (20%), human mucosal melanoma harbors these mutations much less frequently. This makes therapeutic targeting and research modeling of the oral form potentially different from that of the cutaneous form in humans. Similarly, research has found only rare Nras mutations and no activating Braf mutations in canine oral melanomas, but they are still reliant on MAPK signaling. IQGAP1 is a signaling scaffold that regulates oncogenic ERK1/2 MAPK signaling in human Ras- and Raf- driven cancers, including melanomas. To investigate whether IQGAP1 is a potential target in canine melanoma, we examined the expression and localization of IQGAP1 in primary canine melanomas and canine oral melanoma cell lines obtained from the University of California-Davis. Using CRISPR/Cas9 knockout of IQGAP1, we examined effects on downstream ERK1/2 pathway activity and assayed proliferation of cell lines when treated with a peptide that blocks the interaction between IQGAP1 and ERK1/2. We observed that canine IQGAP1 is expressed and localizes to a similar extent in both human and canine melanoma by qPCR, Western blot, and immunofluorescence. Deletion of IQGAP1 reduces MAPK pathway activation in cell lines, similar to effects seen in human BrafV600E cell lines. Additionally, we demonstrated reduced proliferation when these cells are treated with a blocking peptide in vitro.

Xu Y, Qi Y, Luo J, et al.
Hepatitis B Virus X Protein Stimulates Proliferation, Wound Closure and Inhibits Apoptosis of HuH-7 Cells via CDC42.
Int J Mol Sci. 2017; 18(3) [PubMed] Free Access to Full Article Related Publications
Chronic hepatitis B virus (HBV) infection has been considered as the major cause of hepatocellular carcinoma (HCC). Hepatitis B virus X protein (HBx) has been reported to be oncogenic. The underlying mechanisms of HBV-related HCC are not fully understood, and the role played by the HBx protein in HBV induced carcinogenesis remains controversial. CDC42, a member of the Rho GTPase family, has been reported to be overexpressed in several different cancers, including HBV-related HCC. However, the specific role of CDC42 in HCC development remains unclear. Here, we investigated the cellular mechanisms by which CDC42 was responsible for the higher proliferation of HuH-7 cells mediated by HBx. We found that the expression level of CDC42 and its activity were significantly increased in HuH-7-HBx cells. The deficiency of CDC42 using the CRISPR/Cas9 system and inhibition by specific inhibitor CASIN led to the reduction of HBx-mediated proliferation. Furthermore, we observed that IQ Motif Containing GTPase Activating Protein 1 (IQGAP1), the downstream mediator of the CDC42 pathway, might be involved in the carcinogenesis induced by HBx. Therefore, the HBx/CDC42/IQGAP1 signaling pathway may potentially play an important role in HBx-mediated carcinogenesis.

Pan CW, Jin X, Zhao Y, et al.
AKT-phosphorylated FOXO1 suppresses ERK activation and chemoresistance by disrupting IQGAP1-MAPK interaction.
EMBO J. 2017; 36(8):995-1010 [PubMed] Free Access to Full Article Related Publications
Nuclear FOXO proteins act as tumor suppressors by transcriptionally activating genes involved in apoptosis and cell cycle arrest, and these anticancer functions are inhibited by AKT-induced phosphorylation and cytoplasmic sequestration of FOXOs. We found that, after AKT-mediated phosphorylation at serine 319, FOXO1 binds to IQGAP1, a hub for activation of the MAPK pathway, and impedes IQGAP1-dependent phosphorylation of ERK1/2 (pERK1/2). Conversely, decreased FOXO1 expression increases pERK1/2 in cancer cell lines and correlates with increased pERK1/2 levels in patient specimens and disease progression. Treatment of cancer cells with PI3K inhibitors or taxane causes FOXO1 localization in the nucleus, increased expression of pERK1/2, and drug resistance. These effects are reversed by administering a small FOXO1-derived phospho-mimicking peptide inhibitor

Diao B, Liu Y, Zhang Y, et al.
IQGAP1‑siRNA inhibits proliferation and metastasis of U251 and U373 glioma cell lines.
Mol Med Rep. 2017; 15(4):2074-2082 [PubMed] Free Access to Full Article Related Publications
IQ motif containing GTPase activating protein 1 (IQGAP1) is a scaffold protein, which is aberrantly expressed in several tumor types and is closely associated with the development, metastasis and prognosis of cancer. Several studies have demonstrated that IQGAP1 has broad prospects in the basic and clinical research of tumors. The present study aimed to explore the effects of IQGAP1‑small interfering (si) NA on the proliferation and metastasis of U251 and U373 glioma cell lines, which markedly expressed IQGAP1. The human glioma cell lines (U251 and U373) were transfected with siRNA and transfection efficacy was confirmed by reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) and western blot analysis. Cell proliferation was detected using the Cell Counting kit‑8, and cell metastasis capabilities were detected using cell adhesion, migration and invasion assays. In addition, the expression levels of several tumor‑associated genes were determined by RT‑qPCR and western blotting. The results indicated that IQGAP1 was expressed at higher levels in glioma tissues compared with in normal brain tissues. IQGAP1‑siRNA significantly inhibited cell proliferation, and cell adhesion, migration and invasion. Furthermore, the expression levels of matrix metalloproteinase (MMP)2, Snail, MMP9, fibronectin 1 and Twist were suppressed, and E‑cadherin was upregulated in response to siRNA‑IQGAP1. The present study identified the function of IQGAP1 in glioma cell biology, and indicated that it may be considered a novel target for glioma treatment.

Huang JK, Ma L, Song WH, et al.
MALAT1 promotes the proliferation and invasion of thyroid cancer cells via regulating the expression of IQGAP1.
Biomed Pharmacother. 2016; 83:1-7 [PubMed] Related Publications
BACKGROUND: Increasing evidence indicated that metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) acted as a key regulator in the proliferation and invasion of several cancers. However, the function of MALAT1 in the development of thyroid cancer has not been experimentally established.
METHODS: The expression of MALAT1 and IQGAP1 in thyroid cancer tissues and cells were detected by quantitative real-time PCR and western blot. The effects of MALAT1 and IQGAP1 on the cell proliferation and invasion of thyroid cancer cells were detected with a 3-(4,5-dimethylthiazol)-2,5-diphenyl tetrazolium 4 (MTT) assay and a Transwell assay, respectively. FTC-133 or SW1736 transfected with si-MALAT1 or pcDNA-MALAT1 were injected subcutaneously into 4-week-olds BALB/c mice to examine the impact of MALAT1 on the tumor development of thyroid cancer in vivo.
RESULTS: In this study, we discovered the higher level of MALAT-1 and expression of IQGAP1 in thyroid cancer tissues and in thyroid cancer cells compared to that in the control. MTT and Transwell assay showed that the proliferation and invasion of FTC-133 cells with MALAT-1 knockdown were inhibited. Moreover, MALAT-1 could upregulate the expression of IQGAP1 in thyroid cancer cells. In addition, IQGAP1 knockdown reversed the decreasing cell proliferation and invasion of thyroid cancer induced by MALAT-1 overexpression. Finally, the study in vivo verified that MALAT-1 promoted the tumor growth of thyroid cancer.
CONCLUSION: Our study indicated that MALAT1 promoted the proliferation and invasion of thyroid cancer cells via regulating the expression of IQGAP1.

Li G, Gao Y, Cui Y, et al.
Overexpression of CD44 is associated with the occurrence and migration of non-small cell lung cancer.
Mol Med Rep. 2016; 14(4):3159-67 [PubMed] Free Access to Full Article Related Publications
Non-small cell lung cancer (NSCLC) is a potentially fatal disease and the incidence is increasing annually. In order to diagnose and treat NSCLC effectively, greater understanding of its molecular mechanism is required. In the present study, 36 NSCLC tissues and 10 normal tissues were selected. Reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) was used to analyze the CD44 mRNA expression level in NSCLC tissue and DNA sequencing was performed to further verify the CD44 expression level. Differentially expressed genes between tumor tissues and controls were determined by DNA sequencing and the Gene_act_net between CD44 and its associated genes was constructed. Gene Ontology (GO) term enrichment analysis of the differentially expressed genes was performed by the Biological Networks Gene Ontology tool. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis was performed based on the Expression Analysis Systematic Explorer test applied in the Database for Annotation, Visualization and Integrated Discovery. RT‑qPCR results showed that CD34 was overexpressed in 21 of the 36 NSCLC tissues (58.3%). The Gene_act_net indicated that there were 20 differentially expressed genes with 17 upregulated and 3 downregulated. Among them, CD44, MET, ERBB2, EGFR, AKT1, IQGAP1 and STAT3 were associated with the occurrence and migration of NSCLC. In KEGG pathway analysis, extracellular matrix‑receptor interaction and hematopoietic cell lineage pathways were the most affected by overexpressed CD44; and thus may be important in the development and migration of NSCLC. In conclusion, CD44 was overexpressed in NSCLC and the overexpression was associated with the occurrence of NSCLC and migration of NSCLC cells.

Zoheir KM, Abd-Rabou AA, Harisa GI, et al.
IQGAP1 gene silencing induces apoptosis and decreases the invasive capacity of human hepatocellular carcinoma cells.
Tumour Biol. 2016; 37(10):13927-13939 [PubMed] Related Publications
IQ motif-containing GTPase-activating proteins (IQGAPs) belong to a conserved family, and they are involved in various intracellular processes. IQGAP1 is expressed in all cells, while IQGAP2 and IQGAP3 are mainly expressed in hepatic cells. IQGAP1 has been suggested to be an oncogene, while IQGAP2 is considered a tumor-suppressor gene. However, the relationship between RAS family genes and IQGAP genes remains unclear. We recently demonstrated this interaction in a chemically induced mouse liver cancer. In this study, IQGAP1 expression was partially silenced in human hepatocellular carcinoma (HepG2) cells. We investigated the impact of IQGAP1 silencing on the interactions of IQGAP and RAS with several apoptotic proteins, including caspase-3 (CASP3), BCL2-associated X protein (BAX), and B-cell leukemia/lymphoma 2 (BCL2). Additionally, we investigated the effects of the interactions of these genes on cell viability, proliferation, apoptosis, and invasive capacity. IQGAP1 siRNA-treated HepG2 cells showed lower invasive capacity than the control cells, and this reduction was time- and vector concentration-dependent. In addition, IQGAP1 silencing resulted in significantly lower IQGAP1 level and subsequently higher IQGAP2 and IQGAP3 expression in HepG2 cells than in the control. Flow cytometry analyses indicated that the silencing of IQGAP1 can induce early and late apoptosis in HepG2 cells. Additionally, IQGAP2, IQGAP3, CASP3, and BAX were upregulated whereas IQGAP1 and BCL2 were downregulated in the siRNA-treated cells. Furthermore, we observed that the mRNA levels of HRAS, KRAS, NRAS, and MRAS decreased upon IQGAP1 silencing. These findings indicate that IQGAP1 potentially regulates the expression of IQGAP and RAS gene families and demonstrate its regulatory role in the apoptotic network. Taken together, our findings suggest that IQGAP1 silencing plays crucial roles in the apoptosis of HepG2 cells and lowers their proliferative and invasive capacities.

Lagares-Tena L, García-Monclús S, López-Alemany R, et al.
Caveolin-1 promotes Ewing sarcoma metastasis regulating MMP-9 expression through MAPK/ERK pathway.
Oncotarget. 2016; 7(35):56889-56903 [PubMed] Free Access to Full Article Related Publications
Ewing sarcoma (ES) is a bone and soft tissue sarcoma affecting mostly children and young adults. Caveolin-1 (CAV1) is a well-known target of EWS/FLI1, the main driver of ES, with an oncogenic role in ES. We have previously described how CAV1 is able to induce metastasis in ES via matrix metalloproteinase-9 (MMP-9). In the present study we showed how CAV1 silencing in ES reduced MEK1/2 and ERK1/2 phosphorylation. Accordingly, chemical inhibition of MEK1/2 resulted in reduction in MMP-9 expression and activity that correlated with reduced migration and invasion. IQ Motif Containing GTPase Activating Protein 1 (IQGAP1) silencing reduced MEK1/2 and ERK1/2 phosphorylation and MMP-9 expression. Furthermore, IQGAP1 silenced cells showed a marked decrease in their migratory and invasive capacity. We demonstrated that CAV1 and IQGAP1 localize in close proximity at the cellular edge, thus IQGAP1 could be the connecting node between CAV1 and MEK/ERK in ES metastatic phenotype. Analysis of the phosphorylation profile of CAV1-silenced cells showed a decrease of p-ribosomal protein S6 (RPS6). RPS6 can be phosphorylated by p90 ribosomal S6 kinases (RSK) proteins. CAV1-silenced cells showed reduced levels of p-RSK1 and treatment with U0126 provoked the same effect. Despite not affecting ERK1/2 and RPS6 phosphorylation status neither MMP-9 expression nor activity, RSK1 silencing resulted in a reduced migratory and invasive capacity in vitro and reduced incidence of metastases in vivo in a novel orthotopic model. The present work provides new insights into CAV1-driven metastatic process in ES unveiling novel key nodes.

Okura H, Golbourn BJ, Shahzad U, et al.
A role for activated Cdc42 in glioblastoma multiforme invasion.
Oncotarget. 2016; 7(35):56958-56975 [PubMed] Free Access to Full Article Related Publications
Cdc42 is a Rho-GTPase which plays a major role in regulating cell polarity and migration by specifying the localization of filopodia. However, the role of Cdc42 in GBM invasion has not been thoroughly investigated. We generated stable doxycycline-inducible clones expressing wild type (WT)-, constitutively active (CA)-, and dominant negative (DN)-Cdc42 in three different human glioma cell lines. Expression of CA-Cdc42 significantly increased the migration and invasive properties of malignant glioma cells compared to WT and DN-Cdc42 cell clones, and this was accompanied by a greater number of filopodia and focal adhesion structures which co-localize with phosphorylated focal adhesion kinase (FAK). By mass spectrometry and immunoprecipitation studies, we demonstrated that activated Cdc42 binds to IQGAP1. When implanted orthotopically in mice, the CA-Cdc42 expressing glioma cells exhibited enhanced local migration and invasion, and led to larger tumors, which significantly reduced survival. Using the Cancer Genome Atlas dataset, we determined that high Cdc42 expression is associated with poorer progression free survival, and that Cdc42 expression is highest in the proneural and neural subgroups of GBM. In summary, our studies demonstrate that activated Cdc42 is a critical determinant of the migratory and invasive phenotype of malignant gliomas, and that its effect may be mediated, at least in part, through its interaction with IQGAP1 and phosphorylated FAK.

Jin Y, Lv X, Zhou J, Chen J
Potential involvement of IQGAP1 in proliferation and metastasis of human pancreatic cancer.
Front Biosci (Landmark Ed). 2016; 21:1076-83 [PubMed] Related Publications
IQGAP1, as a scaffold protein, integrates diverse cellular functions, including rearrangement of the actin cytoskeleton, cell adhesion, gene transcription and cell cycle regulation. IQGAP1 is elevated in a number of human cancer cells. However little is known about the expression of IQGAP in human pancreatic cancer and its association with cancer proliferation or metastasis. In the present study, we examined the expression of IQGAP1 in different pancreatic cancer cell lines and we found that IQGAP1 level is highly correlated with the degree of malignancy of pancreatic cancer cell metastasis. The proliferation, metastasis, motility and tumorigenesis in SW1990 human pancreatic cells were greatly impaired by down-regulating IQGAP1 expression with RNA interference. Mechanistic analysis indicated that Cdc42/Rac1 pathway might contribute to IQGAP1-mediated-pancreatic cell proliferation and tumorigenesis.

Dong P, Ihira K, Xiong Y, et al.
Reactivation of epigenetically silenced miR-124 reverses the epithelial-to-mesenchymal transition and inhibits invasion in endometrial cancer cells via the direct repression of IQGAP1 expression.
Oncotarget. 2016; 7(15):20260-70 [PubMed] Free Access to Full Article Related Publications
Overexpression of IQGAP1 and microRNA (miRNA) dysregulation are frequent in human tumors, but little is known about the role of IQGAP1 and its relationship to miRNA in endometrial carcinogenesis. We demonstrate that IQGAP1 activates the epithelial-mesenchymal transition (EMT) program and that miR-124 directly represses IQGAP1 expression in endometrial cancer (EC) cells. The overexpression of IQGAP1 stimulates EMT features and enhances migration, invasion and proliferation of EC cells, whereas knocking down IQGAP1 expression reverses EMT and inhibits these malignant properties. Using miRNA microarray profiling, we identified 29 miRNAs (let-7b, let-7f, miR-10b, miR-15b, miR-23a, miR-24, miR-25, miR-27a, miR-29b, miR-30a-5p, miR-34a, miR-124, miR-127, miR-130b, miR-148a, miR-155, miR-191*, miR-194, miR-224, miR-362, miR-409-3p, miR-422b, miR-424, miR-453, miR-497, miR-518d, miR-518f*, miR-526a and miR-656) that are significantly down-regulated in an in vitro-selected highly invasive derivative cell line (HEC-50-HI) relative to the parental HEC-50 cells. We further identified miR-124 as a direct regulator of IQGAP1 in EC cells. Enforced expression of miR-124 suppresses EC cell invasion and proliferation. The expression of IQGAP1 mRNA was significantly elevated in EC tissues, while the expression of miR-124 was decreased. The downregulation of miR-124 correlates with a poor survival outcome for patients with EC. Treating EC cells with the demethylating agent 5-aza-2'-deoxycytidine increased miR-124 expression and down-regulated IQGAP1 levels. Our data suggest that IQGAP1 promotes EMT, migration and invasion of EC cells. MiR-124, a novel tumor suppressor miRNA that is epigenetically silenced in EC, can reverse EMT and the invasive properties, by attenuating the expression of the IQGAP1 oncogene.

Arienti C, Zanoni M, Pignatta S, et al.
Preclinical evidence of multiple mechanisms underlying trastuzumab resistance in gastric cancer.
Oncotarget. 2016; 7(14):18424-39 [PubMed] Free Access to Full Article Related Publications
HER2-positive advanced gastric cancer patients frequently develop resistance to trastuzumab through mechanisms still poorly understood. In breast cancer, other members of the HER-family are known to be involved in trastuzumab-resistance, as is overexpression of the scaffold protein IQGAP1. In the present work, we investigated acquired resistance to trastuzumab in gastric cancer experimental models. Trastuzumab-resistant (HR) subclones derived from 3 HER2-overexpressing gastric cancer cells were generated and characterized for alterations in HER2-signaling mechanisms by next-generation sequencing, immunohistochemical, western blot and qRT-PCR techniques, and molecular modeling analysis. All subclones showed a reduced growth rate with respect to parental cell lines but each had a different resistance mechanism. In NCI N87 HR cells, characterized by a marked increase in HER2-signaling pathways with respect to the parental cell line, trastuzumab sensitivity was restored when IQGAP1 expression was silenced. AKG HR subclone showed higher HER3 protein expression than the parental line. High nuclear HER4 levels were observed in KKP HR cells. In conclusion, our study revealed that high IQGAP1 expression leads to resistance to trastuzumab in gastric cancer. Furthermore, 2 new mutations of the HER2 gene that may be involved in acquired resistance were identified in AKG HR and KKP HR subclones.

Sun G, Liu Y, Wang K, Xu Z
miR-506 regulates breast cancer cell metastasis by targeting IQGAP1.
Int J Oncol. 2015; 47(5):1963-70 [PubMed] Related Publications
MicroRNA (miRNA or miR)-506 is a novel miRNA related to the survival of breast cancer patients. However, the mechanism underlying miRNA-506 involvement in breast carcinogenesis remains unclear. In the present study, we found that miR-506 was downregulated in human breast malignant tissues and breast cancer cell lines by RT-qPCR analysis, and the expression level of miR-506 was decreased with the increasing of tumor stage. Subsequently, gain-of-function and loss-of-function experiments were performed in vitro, and the results from MTT assay, Transwell-Matrigel invasion assay and cell adhesion assay revealed that miR-506 suppresses cell proliferation, invasion and adhesion of breast cancer cells. Luciferase reporter assay revealed that IQ motif containing GTPase activating protein 1 (IQGAP1) is a direct target of miR-506. miR-506 represses the expression of IQGAP1 and its downstream extracellular signal regulated kinase (ERK) mitogen-activated protein kinase (MAPK) signaling pathways, as demonstrated by the RT-qPCR and western blot analysis. Furthermore, we found that IQGAP1 rescues the effect of miR-506 on cell proliferation, invasion, adhesion, and the activation of ERK MAPK signaling. In conclusion, the present study is the first to provide evidence that miR-506 acts as a tumor suppressor, at least partially, by directly downregulating IQGAP1 in breast cancer cells. The miR-506/IQGAP1/ERK pathway may be a novel therapeutic target in breast cancer.

Jin X, Liu Y, Liu J, et al.
The Overexpression of IQGAP1 and β-Catenin Is Associated with Tumor Progression in Hepatocellular Carcinoma In Vitro and In Vivo.
PLoS One. 2015; 10(8):e0133770 [PubMed] Free Access to Full Article Related Publications
The IQ-domain GTPase-activating protein 1 (IQGAP1) is a multifunctional scaffold protein, which interacts with diverse proteins to regulate cell adhesion and cell migration. The abnormal expression of IQGAP1 widely exists in many cancers, but biological roles of IQGAP1 cooperation with its interacting proteins to involve in tumorigenesis remain to clarify. In this study, we have found that IQGAP1 interacts with β-catenin and regulates β-catenin expression in hepatocellular carcinoma (HCC) cells. The expression levels of IQGAP1 and β-catenin and their associations have a positive correlation with cell metastasis ability in several HCC cell lines. The up-regulation of IQGAP1 and β-catenin improves cell proliferation and migration ability of HCC cells, whereas the knockdown of IQGAP1 by small interfering RNA can decrease β-catenin expression, which results in the reduction of cell proliferation and migration ability in vitro. In addition, a significantly higher expression of IQGAP1 and β-catenin also usually exists in human HCC tissues, especially their overexpression is clinicopathologically associated with tumor malignancy. Generally the overexpression and interactions of IQGAP1 and β-catenin contribute to HCC progression by promoting cell proliferation and migration.

Hensel J, Duex JE, Owens C, et al.
Patient Mutation Directed shRNA Screen Uncovers Novel Bladder Tumor Growth Suppressors.
Mol Cancer Res. 2015; 13(9):1306-15 [PubMed] Free Access to Full Article Related Publications
UNLABELLED: Next-generation sequencing (NGS) of human bladder cancer has revealed many gene alterations compared with normal tissue, with most being predicted to be "loss of function." However, given the high number of alterations, evaluating the functional impact of each is impractical. Here, we develop and use a high-throughput, in vivo strategy to determine which alterations are loss of function in tumor growth suppressors. Genes reported as altered by NGS in bladder cancer patients were bioinformatically processed by MutationTaster and MutationAssessor, with 283 predicted as loss of function. An shRNA lentiviral library targeting these genes was transduced into T24 cells, a nontumorigenic human bladder cancer cell line, followed by injection into mice. Tumors that arose were sequenced and the dominant shRNA constructs were found to target IQGAP1, SAMD9L, PCIF1, MED1, and KATNAL1 genes. In vitro validation experiments revealed that shRNA molecules directed at IQGAP1 showed the most profound increase in anchorage-independent growth of T24 cells. The clinical relevance of IQGAP1 as a tumor growth suppressor is supported by the finding that its expression is lower in bladder cancer compared with benign patient urothelium in multiple independent datasets. Lower IQGAP1 protein expression associated with higher tumor grade and decreased patient survival. Finally, depletion of IQGAP1 leads to increased TGFBR2 with TGFβ signaling, explaining in part how reduced IQGAP1 promotes tumor growth. These findings suggest IQGAP1 is a bladder tumor growth suppressor that works via modulating TGFβ signaling and is a potentially clinically useful biomarker.
IMPLICATIONS: This study used gene mutation information from patient-derived bladder tumor specimens to inform the development of a screen used to identify novel tumor growth suppressors. This included identification of the protein IQGAP1 as a potent bladder cancer growth suppressor.

Meng D, Wu W, Li Z, Qin G
IQGAP1 modulates the proliferation and invasion of thyroid cancer cells in response to estrogen.
Int J Mol Med. 2015; 36(2):588-94 [PubMed] Related Publications
Thyroid cancer is an endocrine malignancy with a high incidence rate, which is affected by female hormones, particularly estrogens, in its growth and progression. IQ-domain GTPase-activating protein 1 (IQGAP1) is overexpressed in a range of types of cancer and is reported to interact with estrogen receptor α (ERα) in breast cancer cells. However, the association between IQGAP1 and ERα in thyroid cancer cells remains to be elucidated. In this study, the role of IQGAP1 in thyroid cancer cells was examined. The expression of IQGAP1 (190 kDa) was analyzed using western blot analysis, which indicated that IQGAP1 was overexpressed in thyroid cancer tissues and FTC133 cells. However, IQGAP1 knockdown in the FTC133 cells led to a significant downregulation in ERα transcriptional activity, cell proliferation, cell adhesion and cell invasion under 17β-estradiol (E2) conditions. Furthermore, ERα knockdown inhibited the enhanced protein expression levels of phosphorylated ERK1/2 and cyclin D1, which were induced by the overexpression of IQGAP1. Co-immunoprecipitation was also performed in thyroid cancer cells and the results suggested that IQGAP1 directly interacted with ERα in the FTC133 cells and the co-transfected COS-7 cells. Taken together, these findings revealed that IQGAP1 may directly interact with ERα and serve as a signal integrator, mediating ERα transcriptional activity, cell proliferation and cell invasion during the progression of thyroid cancer.

Gong X, Yi J, Carmon KS, et al.
Aberrant RSPO3-LGR4 signaling in Keap1-deficient lung adenocarcinomas promotes tumor aggressiveness.
Oncogene. 2015; 34(36):4692-701 [PubMed] Free Access to Full Article Related Publications
The four R-spondins (RSPO1-4) and their three related receptors LGR4, 5 and 6 (LGR4-6) have emerged as a major ligand-receptor system with critical roles in development and stem cell survival through modulation of Wnt signaling. Recurrent, gain-of-expression gene fusions of RSPO2 (to EIF3E) and RSPO3 (to PTPRK) occur in a subset of human colorectal cancer. However, the exact roles and mechanisms of the RSPO-LGR system in oncogenesis remain largely unknown. We found that RSPO3 is aberrantly expressed at high levels in approximately half of Keap1-mutated lung adenocarcinomas (ADs). This high RSPO3 expression is driven by a combination of demethylation of its own promoter region and deficiency in Keap1 instead of gene fusion as in colon cancer. Patients with RSPO3-high tumors (~9%, 36/412) displayed much poorer survival than the rest of the cohort (median survival of 28 vs 163 months, log-rank test P<0.0001). Knockdown (KD) of RSPO3, LGR4 or their signaling mediator IQGAP1 in lung cancer cell lines with Keap1 deficiency and high RSPO3-LGR4 expression led to reduction in cell proliferation and migration in vitro, and KD of LGR4 or IQGAP1 resulted in decrease in tumor growth and metastasis in vivo. These findings suggest that aberrant RSPO3-LGR4 signaling potentially acts as a driving mechanism in the aggressiveness of Keap1-deficient lung ADs.

Lu SH, Jiang XJ, Xiao GL, et al.
miR-124a restoration inhibits glioma cell proliferation and invasion by suppressing IQGAP1 and β-catenin.
Oncol Rep. 2014; 32(5):2104-10 [PubMed] Related Publications
A number of microRNAs have been identified to be important regulators of tumorigenesis. Previous research has shown that miR-124 is abundantly expressed in normal brain tissue; however, only a few reports have focused on the biological impact of miR-124 on glioma cells, and the underlying mechanisms need to be elucidated. Therefore, we investigated the effect of miR-124a on glioma cell proliferation and invasion; furthermore, the underlying molecular mechanism was examined. The present study demonstrated that miR-124a expression was downregulated in human glioma tissues, and its expression level was negatively correlated with the pathological grade of the glioma. Restoration of miR-124a inhibited glioma cell proliferation and invasion in vitro. Furthermore, we found that miR-124a directly targeted and suppressed IQ motif containing GTPase activating protein 1 (IQGAP1), a well-known regulator of actin dynamics and cell motility. RNA interference assay showed that IQGAP1 knockdown led to downregulation of β-catenin and downstream cyclin D1. Taken together, our study revealed that miR-124a could inhibit glioma cell proliferation and invasion by blocking the expression of the IQGAP1 gene and downstream β-catenin and cyclin D1. This research may provide a useful molecular therapy for gliomas.

Zhang TT, Jiang YY, Shang L, et al.
Overexpression of DNAJB6 promotes colorectal cancer cell invasion through an IQGAP1/ERK-dependent signaling pathway.
Mol Carcinog. 2015; 54(10):1205-13 [PubMed] Related Publications
DNAJB6 is a member of the heat shock protein 40 (Hsp40) family. We here investigated the clinical correlation and biological role of DNAJB6 overexpression in colorectal cancer (CRC). The expression of DNAJB6 protein was examined in 200 cases of colorectal adenocarcinomas by immunohistochemistry (IHC) technology. Gene transfection and RNA interference were performed to determine the effect of DNAJB6 expression on the invasion of CRC cells and to explore the underlying molecular mechanisms in vitro and in vivo. Overexpression of DNAJB6 was found in 39% (78/200) of the CRC tissues, especially in tumors at pT4 as compared with at pT1-3 (P = 0.02). A Kaplan-Meier survival analysis revealed a correlation between DNAJB6 expression and overall survival (OS) times (P = 0.003). Multivariate analysis confirmed that DNAJB6 overexpression was an independent prognostic factor for CRC (P = 0.002). RNA interference-mediated silencing of the DNAJB6 gene inhibited the invasion of CRC cells in vitro were accompanied by a significant reduction in the protein levels of IQ-domain GTPase-activating protein 1 (IQGAP1) and phosphorylated ERK (pERK). An in vivo assay showed that inhibition of DNAJB6 expression decreased the lung metastases of CRC cells. IHC analysis of serial sections showed that there was a positive correlation between DNAJB6 and IQGAP1 expression in primary CRC tissues (P = 0.013). The data suggest that DNAJB6 plays an important oncogenic role in CRC cell invasion by up-regulating IQGAP1 and activating the ERK signaling pathway and that DNAJB6 may be used as a prognostic marker for CRC.

Yang Y, Zhao W, Xu QW, et al.
IQGAP3 promotes EGFR-ERK signaling and the growth and metastasis of lung cancer cells.
PLoS One. 2014; 9(5):e97578 [PubMed] Free Access to Full Article Related Publications
Proteins of the IQGAP family display complicated and often contradictory activities in tumorigenesis. IQGAP1 has well documented oncogenic potential and IQGAP2 has putative tumor-suppressive function. IQGAP3 is the latest addition to this family and its role in cancer development remains to be defined. Here we demonstrate IQGAP3 expression is markedly increased in lung cancer tissues at both mRNA and protein levels. Overexpression of IQGAP3 promoted tumor cell growth, and migration and invasion, whereas knockdown of IQGAP3 exhibited opposite effects. Moreover, suppression of IQGAP3 in a lung cancer cell line caused a reduction in the tumorigenicity of these cells in lung tissue after intravenous injection. Furthermore, we showed that IQGAP3 is able to interact with ERK1 and enhance its phosphorylation following treatment with EGF. These data suggest that IQGAP3 may contribute to the pathogenesis of lung cancer by modulating EGFR-ERK signaling.

Wang XX, Wang K, Li XZ, et al.
Targeted knockdown of IQGAP1 inhibits the progression of esophageal squamous cell carcinoma in vitro and in vivo.
PLoS One. 2014; 9(5):e96501 [PubMed] Free Access to Full Article Related Publications
IQGAP1 is a scaffolding protein that can regulate several distinct signaling pathways. The accumulating evidence has demonstrated that IQGAP1 plays an important role in tumorigenesis and tumor progression. However, the function of IQGAP1 in esophageal squamous cell carcinoma (ESCC) has not been thoroughly investigated. In the present study, we showed that IQGAP1 was overexpressed in ESCC tumor tissues, and its overexpression was correlated with the invasion depth of ESCC. Importantly, by using RNA interference (RNAi) technology we successfully silenced IQGAP1 gene in two ESCC cell lines, EC9706 and KYSE150, and for the first time found that suppressing IQGAP1 expression not only obviously reduced the tumor cell growth, migration and invasion in vitro but also markedly inhibited the tumor growth, invasion, lymph node and lung metastasis in xenograft mice. Furthermore, Knockdown of IQGAP1 expression in ESCC cell lines led to a reversion of epithelial to mesenchymal transition (EMT) progress. These results suggest that IQGAP1 plays crucial roles in regulating ESCC occurrence and progression. IQGAP1 silencing may therefore develop into a promising novel anticancer therapy.

Sharma M, Johnson M, Brocardo M, et al.
Wnt signaling proteins associate with the nuclear pore complex: implications for cancer.
Adv Exp Med Biol. 2014; 773:353-72 [PubMed] Related Publications
Several components of the Wnt signaling pathway have in recent years been linked to the nuclear pore complex. β-catenin, the primary transducer of Wnt signals from the plasma membrane to the nucleus, has been shown to transiently associate with different FG-repeat containing nucleoporins (Nups) and to translocate bidirectionally through pores of the nuclear envelope in a manner independent of classical transport receptors and the Ran GTPase. Two key regulators of β-catenin, IQGAP1 and APC, have also been reported to bind specific Nups or to locate at the nuclear pore complex. The interaction between these Wnt signaling proteins and different Nups may have functional implications beyond nuclear transport in cellular processes that include mitotic regulation, centrosome positioning and cell migration, nuclear envelope assembly/disassembly, and the DNA replication checkpoint. The broad implications of interactions between Wnt signaling proteins and Nups will be discussed in the context of cancer.

Ma Y, Jin Z, Huang J, et al.
Quercetin suppresses the proliferation of multiple myeloma cells by down-regulating IQ motif-containing GTPase activating protein 1 expression and extracellular signal-regulated kinase activation.
Leuk Lymphoma. 2014; 55(11):2597-604 [PubMed] Related Publications
The flavonoid quercetin has shown anti-tumor effects against a variety of solid tumors. However, its effects on multiple myeloma (MM) remain unclear. In this study we examined the proliferation of human myeloma cell lines U266, KM3 and RPMI8226 and MM derived cells from four patients with MM after quercetin treatment, and detected the expression of IQ motif-containing GTPase activating protein 1 (IQGAP1), a scaffold protein involved in mitogen-activated protein kinase (MAPK) signaling, by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis. We found that quercetin inhibited the proliferation of MM cells in a dose- and time-dependent manner, accompanied by reduced IQGAP1 expression at mRNA and protein levels, and reduced extracellular signal-regulated kinase 1/2 (ERK1/2) activation. Furthermore, we found that quercetin inhibited the interaction between IQGAP1 and ERK1/2 in RPMI8226 cells. In summary, our results suggest that quercetin suppresses the proliferation of MM cells by down-regulating IQGAP1 expression and ERK activation, and has potential as a novel agent to target oncogenic kinase cascades for MM therapy.

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