IQGAP1 Expression Research Articles

Deletion and Overexpression of the Scaffolding Protein IQGAP1 Promotes Hepatocellular Carcinoma

BackgroundHepatocellular Carcinoma (HCC) is the 5th most common cause of cancer‐related death with an estimated 32,000 annual deaths in the United States. Current treatment methods provide minimal results and can be improved by a more concrete understanding of the underlying mechanisms driving the disease.Sixty‐85% of HCCs are characterized by elevated IQGAP1 protein expression. IQGAP1 is a scaffold protein that binds signaling molecules associated with cellular proliferation to regulate or enhance their activity. While overexpression of IQGAP1 is associated with HCC, other studies indicate IQGAP1 loss enhances tumorigenic signals. Clearly, maintaining IQGAP1 expression is critical for normal tissue homeostasis.MethodsWe asked if IQGAP1 overexpression exacerbates HCC growth. To do this, we used hydrodynamic tail vein injections with the Sleeping Beauty transposase to model HCC. The transposon system can induce HCC in wild‐type, adult mice which are 69% genetically similar to human HCC when human activated (S45Y) □‐catenin and MET (B +M) are expressed in hepatocytes. We included the overexpression of IQGAP1 in this model system and subsequently investigated downstream pro‐growth and survival mechanisms that are regulated by IQGAP1.Additionally, studies suggest that IQGAP1 loss promotes oncogenic signaling. Therefore, we asked if IQGAP1 loss will impact HCC tumorigenesis. Here, we used the diethylnitrosamine (DEN) chemical carcinogenesis model to induce HCC in mice lacking Iqgap1 expression. Following tumorigenesis, we again investigated mechanisms that may become dysregulated upon loss of IQGAP1 expression.ResultsAfter 8.5 weeks, overexpression of B+M with IQGAP1 (B+M+I) in the transposon system resulted in 2‐fold higher LW/BW ratio compared to B+M – indicating potential increased tumor burden. Alpha‐fetoprotein, a marker of highly aggressive HCC, was highest in the B+M+I group. Several canonical Wnt target genes (e.g., Bric5, Lect2, and Glul) were elevated in the B+M+I group. Additionally, we measured increased nuclear □‐catenin in B+M+I compared to B+M tissues after 4 weeks in the transposon model. To test if IQGAP1 overexpression enhances Wnt/□‐catenin activity, we overexpressed IQGAP1 in vitro and found increased nuclear □‐catenin in addition to elevated Wnt/□‐catenin reporter activity.Analysis of Iqgap1−/− tissues after DEN resulted in increased HCC tumor burden compared to control mice. Tumors in Iqgap1−/− mice demonstrated increased proliferation verified by Ki‐67 staining. Finally, we found that loss of Iqgap1 causes elevated MET expression and activation leading to HCC, and can be targeted in vitro by using the MET small molecule inhibitor, EMD‐1214063.ConclusionTogether, our data suggests that dysregulation of IQGAP1 expression drives HCC in our models. Elevated IQGAP1 enhances □‐catenin signaling while IQGAP1 loss causes higher MET expression and activity. Our data indicate that IQGAP1 is in a delicate balance in the liver and any changes can result in HCC oncogenesis.Support or Funding InformationThis work supported by the NIH to AWD (R01DK103645).Summary of IQGAP1 mechanism in Hepatocellular CarcinomaFigure 1

IQGAP Genes in Psoriasis

IQGAP proteins coordinate cell signaling cascades acting as scaffolds for assembly of multiprotein complexes. They mediate growth factor signaling, epithelial-mesenchymal transition, cell proliferation and migration. All of these pathways are important for the pathogenesis of psoriasis, so we suggested that the genes of the IQGAP family may play important roles in the development of this disease. qPCR analysis of the IQGAP1, IQGAP2, and IQGAP3 expression in skin of psoriasis patients showed the genes to be differentially expressed, with IQGAP1 being downregulated and IQGAP3 upregulated. Next we conducted a bioinformatic analysis of IQGAP protein partners in order to identify the protein interactions which would explain the difference between the lesional and visually nonlesional psoriatic skin. On the basis of the meta-analysis of the RNAseq data and the protein-protein interaction databases, we constructed IQGAP PPI graphs which highlighted the IQGAP protein partners involved in psoriasis. Therefore, our studies confirmed the hypothesis on the role of the IQGAP family in the pathogenesis of psoriasis.

The scaffold protein IQGAP1 is crucial for extravasation and metastasis

IQGAP1 is a scaffold protein involved in a range of cellular activities, including migration, invasion, adhesion and proliferation. It is also oncogenic in a variety of cancers, promoting primary tumor growth and invasiveness. However, the role of IQGAP1 in tumor progression and metastasis remains unclear. In this study, we use both knockdown and knockout of IQGAP1 to investigate its role in the metastatic cascade of both melanoma and breast cancer cells in vivo. We find that reduction of IQGAP1 expression decreases the formation of both spontaneous and experimental metastases, without limiting primary or metastatic tumor growth. Furthermore, IQGAP1 knockout significantly inhibits extravasation of tumor cells from circulation, possibly involving invadopodial function. By expressing mutant forms of IQGAP1 in a knockout context, we also determine that IQGAP1’s pro-metastatic functions are dependent on multiple domains and functions. These data demonstrate that IQGAP1 is crucial for metastasis in vivo through regulation of extravasation and suggest that it may represent a valid therapeutic target for inhibiting metastasis.

The mechanism of SP1/p300 complex promotes proliferation of multiple myeloma cells through regulating IQGAP1 transcription

Our previous research had firstly shown that MM cells overexpressed IQGAP1 gene and activated Ras/Raf/MEK/ERK pathway. But the mechanism of IQGAP1 overexpression and IQGAP1 gene transcription regulation remains uncertain. The mechanism of IQGAP1 overexpression and transcriptional regulation of IQGAP1 gene in myeloma cells was explored in the study. Through bioinformatics analysis and prediction we predicted and screened transcription factor Sp1 as a possible upstream regulator of IQGAP1.The proliferation, cell cycle and downstream ERK1/2 and p-ERK1/2 proteins were detected after siRNA-IQGAP1 was transfected to myeloma cells. The expression of Sp1, p300, IQGAP1, p-ERK1/2 and ERK1/2 were detected after Sp1 and p300 were inhibited or overexpressed respectively. The dual-luciferase reporter system was used to detect the activity of IQGAP1 gene promoter. CHIP was used to detect the binding of the Sp1 and IQGAP1 promoter regions.CO-IP was used to explore the interaction between Sp1 and p300.The mRNA expression levels of Sp1,p300 and IQGAP1 of the myeloma patients were detected, and the correlation analysis of their mRNA expression levels were carried out. The results showed IQGAP1-siRNA inhibits cell proliferation, cell cycle, IQGAP1 expression and phosphorylation of ERK1/2 protein. Inhibition of Sp1 or p300 down-regulated ERK1/2 and IQGAP1 expression; overexpression of Sp1 or p300 up-regulated ERK1/2 and IQGAP1 expression; Sp1 and p300 had a positive regulation effect on IQGAP1.Over expression of Sp1 or p300 significantly increased activity of IQGAP1 gene promoter. The transcription factor Sp1 plays a regulatory role in the IQGAP1 promoter region. There is an interaction between Sp1 and p300 in myeloma cells. The mRNA expression levels of Sp1, IQGAP1 and p300 in MM samples showed a positive correlation. In summary IQGAP1 is required for cell proliferation in MM cells, and the transcription of Sp1/p300 complex regulates expression of IQGAP1 gene.

Site-specific expression of IQGAP1 in human nephrons.

IQGAP1 is a multifunctional, 190-kDa scaffolding protein that plays an important role in the regulation of cell adhesion, migration, proliferation, differentiation, polarization and cytoskeletal remodeling. IQGAP1 is ubiquitously expressed in human organs and is highly expressed in the kidney. Currently, the site-specific expression of IQGAP1 in the human nephrons is unclear. We performed Western blotting analysis, immunohistochemistry and double-immunolabeling confocal microscopic analysis of IQGAP1 with specific biomarkers of each nephron segment to study the expression and distribution of IQGAP1 in human nephrons. We found that IQGAP1 was strongly expressed in human podocytes and glomerular endothelial cells, but weakly expressed in glomerular mesangial cells. In human renal tubules, IQGAP1 was strongly expressed in the collecting duct, moderately expressed in the proximal tubule, medullary loop, distal convoluted tubule and connecting tubule. IQGAP1 staining was much stronger in the apical membrane in the proximal tubule, thick descending limb and thick ascending limb of medullary loop and collecting duct. However, the expression of IQGAP1 was mainly in the basolateral membrane of the connecting tubule, and diffusely in the thin limb of medullary loop and distal convoluted tubule. The interaction between IQGAP1 and F-actin suggested that cytoskeleton regulation may be the underlying mechanism mediating the effect of IQGAP1 in human nephrons. To the best of our knowledge, this is the first report of specific expression and differential subcellular location of IQGAP1 in human nephrons. The site-specific expression pattern of IQGAP1 suggests that IQGAP1 may play diverse roles in various human nephron segments.

The phenotype of vascular smooth muscle cells co-cultured with endothelial cells is modulated by PDGFR-β/IQGAP1 signaling in LPS-induced intravascular injury.

Background Sepsis, a leading cause of death in intensive care units, is generally associated with vascular dysfunction. However, its pathophysiological process has not been fully clarified, lacking in-depth knowledge of its pathophysiological process may hinder the improvement of diagnosis and therapy for sepsis. Hence, as the key parts of the vascular wall, the interaction between endothelial cells (ECs) and smooth muscle cells (SMCs) under septic situation need to be further studied.Methods ECs and SMCs were co-cultured using Transwell plates. Lipopolysaccharide (LPS) was used to induce sepsis. A scratch-wound assay was used to assess cell migration, and western blotting was used to assess the level of redifferentiation of SMCs as well as the expression of PDGFR-β and IQGAP1.Results Co-culture with ECs reduced the redifferentiation of SMCs induced by LPS (10 μg/ml), which was characterized by increased migration ability and decreased expression of contractile proteins (e.g., SM22 and α-SMA). The production of TNF-α could decrease the level of PDGFR-β in SMCs. Treatment of SMCs with the PDGFR-β inhibitor imatinib (5 μM) was able to counteract LPS-induced SMC redifferentiation and reduce IQGAP1 protein expression, especially when SMCs were co-cultured with ECs.Conclusion The phenotype of vascular SMCs co-cultured with ECs was modulated by IQGAP1 through the PDGFR-β pathway, which may lead to vascular remodeling and homeostasis in LPS-induced intravascular injury. This pathway could be a novel target for the treatment of vascular damage.

Downregulation of IQGAP2 Correlates with Prostate Cancer Recurrence and Metastasis

IQGAP2 was recently reported as a tumor suppressor of prostate cancer (PC). Nonetheless, its clinical implications remain unknown. To address this issue, we extracted data related to IQGAP2 mRNA expression and genomic alterations from multiple large datasets within the Oncomine and cBioPortal databases and performed in silico analyses to determine a potential association of IQGAP2 mRNA expression and its genomic alterations with PC progression. In 4 cohorts consisting of 118 normal prostate tissues and 277 PCs, IQGAP2 mRNA expression was significantly elevated particularly in low-grade (primary Gleason score ≤3) PCs; these changes separate PC from normal tissues with area under curve values of 0.7-0.8. Significant reductions in IQGAP2 mRNA levels and gene copy number occurred in more than 70 metastases compared to at least 230 local PCs. This duo-alteration in IQGAP2 expression supports IQGAP2 elevation suppressing and its downregulation facilitating PC progression. Deletion and missense mutations were detected in 23 of 492 primary PCs; these alterations significantly associate with PC recurrence (HR=2.71; 95% CI: 1.35-5.44; P=.005) after adjusting for known risk factors and correlate with reductions in disease-free survival (DFS, P=.002). IQGAP2 (5q13.3) genomic alterations were observed in SPOP-marked PCs and co-occurred with deletion in the RN7SK (16p12.2), SNORA50A (16q21), and SNORA50C (17q23.3) genes; the co-occurrence associated with reductions in DFS (P=4.14e-4). In two independent PC populations, MSKCC (n=130) and TCGA provisional (n=490), reductions in IQGAP2 mRNA expression were significantly associated with DFS. Collectively, this investigation reveals an association of IQGAP2 with PC progression.

BIOMARKER POTENTIAL OF IQ-DOMAIN GTPASE-ACTIVATING PROTEINS FAMILY PROTEIN IN PANCREATIC CANCER: A MINI REVIEW

Objectives: Our present study was done to understand molecular regulatory mechanisms of IQGAP proteins and their potentials as biomarker in pancreatic cancer.Methods: In this review, relevant studies were obtained by assessing the PubMed database using the combination of words that included “IQGAP” and “pancreatic cancer”.Results: There is an increasing evidence showing that the expression of IQGAP1 and IQGAP3 is positively correlated with tumorigenesis; however, IQGAP2 might play a role to suppress tumor progression.Conclusion: IQGAP proteins might have potentials as predictive and prognostic biomarker for human pancreatic cancer.

IQGAP1 plays an important role in the tumorigenesis and invasion of papillary thyroid cancer

Background: Numerous studies have indicated that IQGAP1 plays an important role in human cancers. The present study aimed to investigate the IQGAP1 expression pattern in papillary thyroid cancer (PTC) and its relationship with tumor proliferation, invasion and metastasis. Methods: Fresh samples from PTC patients were assessed for the expression levels of IQGAP1 by qPCR, western blotting and immunochemistry assays. Mechanistically, genetic knockdown with siRNA was used to study IQGAP1 protein function. We also examined in vitro cell growth by MTT assay and soft-agar colony formation assays, and cell proliferative index (PI) and apoptosis by flow cytometry analysis. Additionally, cell migration/invasion ability was investigated by Transwell and scratch assays. The potential regulatory mechanisms of IQGAP1 in PTC were further explored by bioinformatics. Results: We found that IQGAP1 mRNA and protein expression levels in primary tumor tissue were significantly higher than in para-tumor and normal thyroid tissues. Metastatic lymph nodules had the highest expression level of IQGAP1. Compared with blank and negative control cells, silencing the Iqgap1 gene with siRNA in K1 and TPC-1 cells inhibited their proliferation and cellular invasion/migration abilities significantly. The bioinformatics analysis revealed that upregulated IQGAP1 expression was related to a series of important pathways and mechanisms involved in tumorigenesis and progression. Conclusions: IQGAP1 may play an important role in tumorigenesis, invasion and metastasis in PTC; furthermore, it may serve as a biomarker for the diagnosis of malignant PTC, and the targeting of this novel molecular marker may have potential therapeutic benefit in PTC.

IQGAP1 plays an important role in the tumorigenesis and invasion of papillary thyroid cancer

Background: Numerous studies have indicated that IQGAP1 plays an important role in human cancers. The present study aimed to investigate the IQGAP1 expression pattern in papillary thyroid cancer (PTC) and its relationship with tumor proliferation, invasion and metastasis.

Ras GTPase-Activating-Like Protein IQGAP1 (IQGAP1) Promotes Breast Cancer Proliferation and Invasion and Correlates with Poor Clinical Outcomes.

BackgroundBreast 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/MethodsIn 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.ResultsIQGAP1 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.ConclusionsIn 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.

Reduced expression of IQGAP2 and higher expression of IQGAP3 correlates with poor prognosis in cancers.

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.

SUMOylation of IQGAP1 promotes the development of colorectal cancer

IQGAP1 is a conserved multifunctional protein implicated in tumorigenesis. An aberrant expression of IQGAP1 widely exists in many cancers, but the SUMOylation modification of IQGAP1 in carcinogenesis is unknown by now. Here we first time explore biological functions of IQGAP1 SUMOylation in promoting colorectal cancer progression in vitro and in vivo. The expression of IQGAP1 and its SUMOylation level are both increased in human colorectal carcinoma (CRC) cells and tissues. IQGAP1 is mainly SUMOylated by SUMO1 at the K1445 residue, which could stabilize IQGAP1 by reducing protein ubiquitination. IQGAP1 SUMOylation improves CRC cell growth, cell migration and tumorigenesis in vivo through activating the phosphorylation of ERK, MEK and AKT. While the SUMOylation site mutation at K1445 of IQGAP1 greatly reduces CRC cell proliferation, migration ability and tumor growth of CRC-xenograft mice by suppressing phosphorylation of ERK, MEK and AKT. Our findings discover the IQGAP1 SUMOylation is a novel regulatory mechanism to enhance tumorigenesis and development of CRC in vitro and in vivo.

IQGAP1 is an oncogenic target in canine melanoma.

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.

Knockdown of IQGAP1 inhibits proliferation and epithelial-mesenchymal transition by Wnt/β-catenin pathway in thyroid cancer.

BackgroundThyroid cancer is the most common endocrine malignant disease with a high incidence rate. The expression of IQGAP1 is upregulated in various cancers, including thyroid cancer. However, the role and underlying mechanism of IQGAP1 in thyroid cancer are still not clear.Materials and methodsThe expression of IQGAP1 in thyroid cancer tissues and cells was determined by reverse transcription polymerase chain reaction and Western blot analysis. Cells were transfected with different siRNAs using Lipofectamine 2000 or were treated with various concentrations of XAV939. The effects of IQGAP1 knockdown on proliferation and epithelial–mesenchymal transition (EMT) of thyroid cancer cells were determined by MTT assay and Western blot analysis. Animal experiments were performed to investigate the effects of IQGAP1 knockdown on the growth of tumors in vivo.ResultsHigh IQGAP1 expression is found in thyroid cancer tissues and cells. Knockdown of IQGAP1 had inhibitory effects on cell proliferation and EMT, as well as on the Wnt/β-catenin pathway. Additionally, inactivation of the Wnt/β-catenin pathway by XAV939 or si-β-catenin suppressed cell proliferation and EMT. Furthermore, suppression of the Wnt/β-catenin pathway reversed the positive effects of pcDNA-IQGAP1 on cell proliferation and EMT in vitro. Moreover, downregulation of IQGAP1 suppressed tumor growth and EMT in SW579 tumor xenografts through the Wnt/β-catenin pathway in vivo.ConclusionOur study demonstrated that knockdown of IQGAP1 inhibited cell proliferation and EMT through blocking the Wnt/β-catenin pathway in thyroid cancer.

Anti-inflammatory effect of miltirone on inflammatory bowel disease via TLR4/NF-κB/IQGAP2 signaling pathway

Inflammatory bowel disease (IBD) is characterized by a radical imbalance in the activation of proinflammatory and anti-inflammatory signaling pathways in the gut. This study was conducted to evaluate the anti-inflammation effect of miltirone against IBD in vitro and in vivo, and try to explore the underlying mechanisms. Miltirone could extenuate the loss of colon length and weight caused by TNBS. Additionally, macroscopic scores and DAI were reduced significantly compared with the TNBS group. The levels of TNF-α, IL-1β, IL-6 and IL-8 were increased significantly with the induction by TNBS (100mg/kg) or LPS (0.5mg/mL). Interestingly, miltirone could down-regulate the levels of these increased pro-inflammatory factors in a dose-dependent manner both in vivo and in vitro. The protein and mRNA expressions of TLR4, MyD88, NF-κB p65 were up-regulated by TNBS or LPS stimulation. CRX-526, the TLR4 inhibitor, as well as miltirone could significantly suppress the increased protein and mRNA expressions. Miltirone could up-regulate the descreased IQGAP2 expression induced by LPS. All these revealed that the anti-inflammatory effect of miltirone on IBD may be via regulating TLR4/NF-κB/IQGAP2 signaling pathway. The findings might supply beneficial hints for the drug research to cure the IBD.

Deletion of IQGAP1 promotes Helicobacter pylori-induced gastric dysplasia in mice and acquisition of cancer stem cell properties in vitro.

Helicobacter pylori infection is responsible for gastric carcinogenesis but host factors are also implicated. IQGAP1, a scaffolding protein of the adherens junctions interacting with E-cadherin, regulates cellular plasticity and proliferation. In mice, IQGAP1 deficiency leads to gastric hyperplasia. The aim of this study was to elucidate the consequences of IQGAP1 deletion on H. pylori-induced gastric carcinogenesis.Transgenic mice deleted for iqgap1 and WT littermates were infected with Helicobacter sp., and histopathological analyses of the gastric mucosa were performed. IQGAP1 and E-cadherin expression was evaluated in gastric tissues and in gastric epithelial cell lines in response to H. pylori infection. The consequences of IQGAP1 deletion on gastric epithelial cell behaviour and on the acquisition of cancer stem cell (CSC)-like properties were evaluated. After one year of infection, iqgap1+/- mice developed more preneoplastic lesions and up to 8 times more gastro-intestinal neoplasia (GIN) than WT littermates. H. pylori infection induced IQGAP1 and E-cadherin delocalization from cell-cell junctions. In vitro, knock-down of IQGAP1 favoured the acquisition of a mesenchymal phenotype and CSC-like properties induced by H. pylori infection.Our results indicate that alterations in IQGAP1 signalling promote the emergence of CSCs and gastric adenocarcinoma development in the context of an H. pylori infection.

IQGAP1 gene silencing induces apoptosis and decreases the invasive capacity of human hepatocellular carcinoma cells

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.

Nuclear translocation of IQGAP1 protein upon exposure to puromycin aminonucleoside in cultured human podocytes: ERK pathway involvement

IQGAP1, a protein that links the actin cytoskeleton to slit diaphragm proteins, is involved in podocyte motility and permeability. Its regulation in glomerular disease is not known. We have exposed human podocytes to puromycin aminonucleoside (PAN), an inducer of nephrotic syndrome in rats, and studied the effects on IQGAP1 biology and function.In human podocytes exposed to PAN, a nuclear translocation of IQGAP1 was observed by immunocytolocalization and confirmed by Western blot after selective nuclear/cytoplasmic extraction. In contrast to IQGAP1, IQGAP2 expression remained cytoplasmic. IQGAP1 nuclear translocation was associated with a significant decrease in its interaction with nephrin and podocalyxin. Activation of the ERK pathway was observed in PAN treated podocytes with a preponderant nuclear localization of the phosphorylated form of ERK (P-ERK). The interaction between IQGAP1 and P-ERK increased upon podocyte exposure to PAN. Inhibitors of ERK pathway activation blocked IQGAP1 nuclear translocation (p<0.02). Chromatin interaction protein assays demonstrated an interaction of IQGAP1 with chromatin and with Histone H3, which increased in response to PAN.In summary, PAN induces the ERK dependent translocation of IQGAP1 into the nuclei in human podocytes which leads to the interaction of IQGAP1 with chromatin and Histone H3, and decreased interactions between IQGAP1 and slit-diaphragm proteins. Therefore, IQGAP1 may have a role in podocyte gene regulation in glomerular disease.

MALAT1 promotes the proliferation and invasion of thyroid cancer cells via regulating the expression of IQGAP1.

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. 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. 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. Our study indicated that MALAT1 promoted the proliferation and invasion of thyroid cancer cells via regulating the expression of IQGAP1.