IQGAP1 silencing suppresses the malignant characteristics of laryngeal squamous cell carcinoma cells

IQGAP1 enhances cell invasion and matrix metalloproteinase-2 expression through upregulating NF-κB activity in esophageal squamous cell carcinoma cells

Esophageal squamous cell carcinoma (ESCC) is one type of the most common malignancies, yet the overall survival rate is still not ideal. IQ motif containing GTPase activating protein 1 (IQGAP1) participates in cell biological functions of various tumors as an oncogene. However, the mechanisms of IQGAP1 affecting malignant development of ESCC are still unclear. In this study, the expression and correlation of IQGAP1 and MMP2 in esophageal cancer tissues were evaluated by online databases and immunohistochemistry. Stably transfected cell lines with IQGAP1 overexpression and knockdown were constructed. Cell growth, migration and invasion ability, the expression of MMP2 and NF-κB expression were examined in ESCC cells. Furthermore, the cellular malignant phenotypes of ESCC and MMP2 expression in IQGAP1 overexpressing cells after treatment with the NF-κB inhibitor pyrrolidinecarbodithioic acid (PDTC) or JSH-23 were detected. We found that the expression of IQGAP1 and MMP2 were up-regulated and positively correlated in ESCC tissues. IQGAP1 overexpression promoted the growth, migration and invasion of ESCC cells, and up-regulated the expression of MMP2, and increased the expression and the nuclear localization level of NF-κB. Treating with PDTC or JSH-23 reversed IQGAP1-mediated cell migration and invasion ability, as well as the expression of MMP2. In summary, IQGAP1 plays a tumor promotion role to regulate the migration and invasion of ESCC cells and the expression of MMP2 through upregulating NF-κB activity, supporting a promising therapeutic target against ESCC.

Role of IQGAP1 in Carcinogenesis

Scaffolding proteins can play important roles in cell signaling transduction. IQ motif-containing GTPase-activating protein 1 (IQGAP1) influences many cellular activities by scaffolding multiple key signaling pathways, including ones involved in carcinogenesis. Two decades of studies provide evidence that IQGAP1 plays an essential role in promoting cancer development. IQGAP1 is overexpressed in many types of cancer, and its overexpression in cancer is associated with lower survival of the cancer patient. Here, we provide a comprehensive review of the literature regarding the oncogenic roles of IQGAP1. We start by describing the major cancer-related signaling pathways scaffolded by IQGAP1 and their associated cellular activities. We then describe clinical and molecular evidence for the contribution of IQGAP1 in different types of cancers. In the end, we review recent evidence implicating IQGAP1 in tumor-related immune responses. Given the critical role of IQGAP1 in carcinoma development, anti-tumor therapies targeting IQGAP1 or its associated signaling pathways could be beneficial for patients with many types of cancer.

The interplay between IQGAP1 and small GTPases in cancer metastasis

The metastatic spread of tumor cells to distant anatomical locations is a critical cause for disease progression and leads to more than 90 % of cancer-related deaths. IQ motif-containing GTPase-activating protein 1 (IQGAP1), a prominent regulator in the cancer metastasis process, is a scaffold protein that interacts with components of the cytoskeleton. As a critical node within the small GTPase network, IQGAP1 acts as a binding partner of several small GTPases, which in turn function as molecular switches to control most cellular processes, including cell migration and invasion. Given the significant interaction between IQGAP1 and small GTPases in cancer metastasis, we briefly elucidate the role of IQGAP1 in regulating cancer metastasis and the varied interactions existing between IQGAP1 and small GTPases. In addition, the potential regulators for IQGAP1 activity and its interaction with small GTPases are also incorporated in this review. Overall, we comprehensively summarize the role of IQGAP1 in cancer tumorigenicity and metastasis, which may be a potential anti-tumor target to restrain cancer progression.

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.

Downregulation of IQGAP1 inhibits epithelial-mesenchymal transition via the HIF1α/VEGF-A signaling pathway in gastric cancer

As an oncogene, IQ-domain GTPase-activating protein 1 (IQGAP1) regulates the epithelial-mesenchymal transition (EMT) of several cancers, such as breast cancer, thyroid cancer, and esophageal squamous cell carcinoma. However, the role of the scaffold protein IQGAP1 on EMT in gastric cancer remains unclear. Therefore, the present work was performed to address the question. Our results showed that IQGAP1 expression is upregulated in human gastric cancer specimens and cell lines. Furthermore, IQGAP1 knockdown inhibited the migratory ability of gastric cancer cells and reduced the expression of mesenchymal phenotype markers, including Slug, β-catenin, Snail, Vimentin, and N-cadherin, as well as vascular endothelial growth factor-A (VEGF-A) secretion in gastric cancer cells. Conversely, IQGAP1 downregulation increased the epithelial phenotype marker E-cadherin. Furthermore, IQGAP1 silencing not only downregulated hypoxia-inducible transcription factor 1α (HIF1α) but also limited its translocation from the cytosol to the nucleus. Collectively, our results indicated that EMT was regulated by IQGAP1, which was associated with VEGF-A, since other data demonstrated that HIF1α was involved in VEGF-A expression. Therefore, we speculated that IQGAP1 regulated EMT of gastric cancer partially via the HIF1α/VEGF-A signaling pathway. IQGAP1 may serve as an effective therapeutic biomarker for gastric cancer.