Nuclear SIPA1 activates integrin β1 promoter and promotes invasion of breast cancer cells

SIPA1 promotes epithelial-mesenchymal transition in colorectal cancer through STAT3 activation

Colorectal cancer (CRC) is the third leading cancer type worldwide and accounts for the second highest rate of cancer-related mortality. Liver metastasis significantly contributes to the mortality associated with CRC, but the fundamental mechanisms behind it remain unclear. Signal-induced proliferation-associated protein 1 (SIPA1), a GTPase activating protein, has been shown to promote metastasis in breast cancer. In this study, our objective was to explore the role of SIPA1 in regulating epithelial-mesenchymal transition (EMT) in CRC. The analysis of The Cancer Genome Atlas (TCGA) database revealed that the expression level of SIPA1 mRNA was notably upregulated and exhibited a positively correlated with EMT and STAT3 signaling pathways in CRC. Knockdown of SIPA1 impairs CRC cell proliferation and migration. Further studies on the reliance of SIPA1 on STAT3 signaling for EMT regulation have shown that SIPA1 stimulates the activation of STAT3, resulting in its nuclear translocation. The co-treatment of overexpressed SIPA1 with the STAT3 inhibitor STTITA has shown that SIPA1 regulates the expression of EMT-related markers through STAT3. Our study indicate that SIPA1 promotes CRC metastasis by activating the STAT3 signaling pathway, underscoring the potential of SIPA1 as a therapeutic target for metastatic CRC patients.

SIPA1 promotes angiogenesis by regulating VEGF secretion in Müller cells through STAT3 activation

Diabetic retinopathy (DR) is a prevalent complication of diabetes that can lead to vision loss. The chronic hyperglycemia associated with DR results in damage to the retinal microvasculature. Müller cells, as a kind of macroglia, play a crucial role in regulating the retinal vascular microenvironment. The objective of this study was to investigate the role of signal-induced proliferation-associated protein 1 (SIPA1) in regulating angiogenesis in Müller cells. Through proteomics, database analysis, endothelial cell function tests, and Western blot detection, we observed an up-regulation of SIPA1 expression in Müller cells upon high glucose stimulation. SIPA1 expression contributed to VEGF secretion in Müller cells and regulated the mobility of retinal vascular endothelial cells. Further investigation of the dependence of SIPA1 on VEGF secretion revealed that SIPA1 activated the phosphorylation STAT3, leading to its translocation into the nucleus. Overexpression of SIPA1 combined with the STAT3 inhibitor STATTIC demonstrated the regulation of SIPA1 in VEGF expression, dependent on STAT3 activation. These findings suggest that SIPA1 promotes the secretion of pro-angiogenic factors in Müller cells by activating the STAT3 signaling pathway, thereby highlighting SIPA1 as a potential therapeutic target for DR.

A novel transcription factor SIPA1: identification and verification in triple-negative breast cancer

Transcription factors (TFs) regulate the expression of genes responsible for cell growth, differentiation, and responses to environmental factors. In this study, we demonstrated that signal-induced proliferation-associated 1 (SIPA1), known as a Rap-GTPase-activating protein, bound DNA and served as a TF. Importin β1 was found to interact with SIPA1 upon fibronectin treatment. A TGAGTCAB motif was recognized and bound by DNA-binding region (DBR) of SIPA1, which was confirmed by electrophoretic mobility shift assay. SIPA1 regulated the transcription of multiple genes responsible for signal transduction, DNA synthesis, cell adhesion, cell migration, and so on. Transcription of fibronectin 1, which is crucial for cell junction and migration of triple-negative breast cancer (TNBC) cells, was regulated by SIPA1 in a DBR-dependent manner both in vivo and in vitro. Furthermore, single-cell transcriptome sequencing analysis of specimens from a metastatic TNBC patient revealed that SIPA1 was highly expressed in metastatic TNBC. Hence, this study demonstrated that SIPA1 served as a TF, promoting TNBC migration, invasion, and metastasis.

Integrins in cancer: Emerging mechanisms and therapeutic opportunities

Integrins are vital surface adhesion receptors that mediate the interactions between the extracellular matrix (ECM) and cells and are essential for cell migration and the maintenance of tissue homeostasis. Aberrant integrin activation promotes initial tumor formation, growth, and metastasis. Recently, many lines of evidence have indicated that integrins are highly expressed in numerous cancer types and have documented many functions of integrins in tumorigenesis. Thus, integrins have emerged as attractive targets for the development of cancer therapeutics. In this review, we discuss the underlying molecular mechanisms by which integrins contribute to most of the hallmarks of cancer. We focus on recent progress on integrin regulators, binding proteins, and downstream effectors. We highlight the role of integrins in the regulation of tumor metastasis, immune evasion, metabolic reprogramming, and other hallmarks of cancer. In addition, integrin-targeted immunotherapy and other integrin inhibitors that have been used in preclinical and clinical studies are summarized.

SIPA1 Regulates LINC01615 to Promote Metastasis in Triple-Negative Breast Cancer

Simple Summary

Breast cancer is a malignant tumor that often endangers women. After undergoing surgery and supplementary chemotherapy, however, tumor recurrence has not been well researched. The primary cause is high metastatic rates. Hence, bioinformatic and functional analyses were performed to indicate the effect of LINC01615 on breast cancer. We revealed that LINC01615 is regulated by the transcription factor SIPA1 in promoting breast cancer cell malignancy.

Abstract

Long non-coding RNAs (lncRNAs) are reported to play an important regulatory effect in carcinogenesis and malignancy. We found by high-throughput sequencing that LINC01615 is upregulated in breast cancer patients and reduces patients’ overall survival. In vivo and in vitro experiments, we clarified that overexpression of LINC01615 can promote breast cancer cell metastasis ability. The expression of LINC01615 is regulated by the transcriptional activator SIPA1, thereby promoting carcinogenesis in breast cancer cells. Our research clarified that LINC01615 can act as an oncogenic factor in promoting the development of breast cancer.

Extracellular Vesicles Derived from SIPA1high Breast Cancer Cells Enhance Macrophage Infiltration and Cancer Metastasis through Myosin-9

Simple Summary

The high expression of signal-induced proliferation-associated 1 (SIPA1) in breast cancer could aggravate cancer cell metastasis, but how the tumour microenvironment is involved in this incident is unknown. In this study, we investigated whether breast cancer cells with high SIPA1 expression recruited macrophages into the tumour microenvironment. We also found that extracellular vesicles (EVs) derived from MDA-MB-231 cells significantly enhanced macrophage migration, compared with that from SIPA1-knockdown MDA-MB-231 cells both in vitro and in vivo. In terms of the mechanism, SIPA1 in cancer cells modulated the key protein myosin-9 in EVs and promoted macrophage infiltration via EVs. We confirmed that either down-regulating SIPA1 expression or blocking myosin-9 by its inhibitor, blebbistatin, led to the suppression of macrophage infiltration. These findings contribute to a deep understanding of how SIPA1 regulates the tumour microenvironment in breast cancer to facilitate tumour metastasis and provide a basis for the development of therapeutics against breast cancer metastasis.

Abstract

Tumour cell metastasis can be genetically regulated by proteins contained in cancer cell-derived extracellular vesicles (EVs) released to the tumour microenvironment. Here, we found that the number of infiltrated macrophages was positively correlated with the expression of signal-induced proliferation-associated 1 (SIPA1) in invasive breast ductal carcinoma tissues and MDA-MB-231 xenograft tumours. EVs derived from MDA-MB-231 cells (231-EVs) significantly enhanced macrophage migration, compared with that from SIPA1-knockdown MDA-MB-231 cells (231/si-EVs) both in vitro and in vivo. We revealed that SIPA1 promoted the transcription of MYH9, which encodes myosin-9, and up-regulated the expression level of myosin-9 in breast cancer cells and their EVs. We also found that blocking myosin-9 by either down-regulating SIPA1 expression or blebbistatin treatment led to the suppression of macrophage infiltration. Survival analysis showed that breast cancer patients with high expression of SIPA1 and MYH9 molecules had worse relapse-free survival (p = 0.028). In summary, SIPA1^high breast cancer can enhance macrophage infiltration through EVs enriched with myosin-9, which might aggravate the malignancy of breast cancer.

Analysis of the expression and prognostic value of MT1-MMP, β1-integrin and YAP1 in glioma

Increased expression of membrane type 1-matrix metalloproteinase (MT1-MMP/MMP14) is associated with the development of many cancers. MT1-MMP may promote the entry of yes-associated protein1 (YAP1) into the nucleus by regulating the regulation of β1-integrin. The purpose of this study was to investigate the effects of MT1-MMP, β1-integrin and YAP1 on the prognosis of gliomas. The expression of proteins was detected by bioinformatics and immunohistochemistry. The relationship between three proteins and clinicopathological parameters was analyzed by the χ² test. Survival analysis was used to investigate the effects of three proteins on prognosis. The results showed that high expressions of MT1-MMP, β1-integrin and YAP1 were found in glioblastoma (GBM) compared with lower-grade glioma (LGG). There was a significantly positive correlation between MT1-MMP and β1-integrin (r = 0.387), MT1-MMP and YAP1 (r = 0.443), β1-integrin and YAP1 (r = 0.348). Survival analysis showed that patients with overexpression of MT1-MMP, β1-integrin and YAP1 had a worse prognosis. YAP1 expression was the independent prognostic factor for progression-free survival (PFS). There was a statistical correlation between the expression of MT1-MMP and YAP1 and isocitrate dehydrogenase 1 (IDHl) mutation. Thus, this study suggested that MT1-MMP, β1-integrin and YAP1, as tumor suppressors, are expected to be promising prognostic biomarkers and therapeutic targets for glioma patients.

SIPA1 Enhances Aerobic Glycolysis Through HIF-2α Pathway to Promote Breast Cancer Metastasis

Increased dependence on aerobic glycolysis is characteristic of most cancer cells, whereas the mechanism underlying the promotion of aerobic glycolysis in metastatic breast cancer cells under ambient oxygen has not been well understood. Here, we demonstrated that aberrant expression of signal-induced proliferation-associated 1 (SIPA1) enhanced aerobic glycolysis and altered the main source of ATP production from oxidative phosphorylation to glycolysis in breast cancer cells. We revealed that SIPA1 promoted the transcription of EPAS1, which is known as the gene encoding hypoxia-inducible factor-2α (HIF-2α) and up-regulated the expression of multiple glycolysis-related genes to increase aerobic glycolysis. We also found that blocking aerobic glycolysis by either knocking down SIPA1 expression or oxamate treatment led to the suppression of tumor metastasis of breast cancer cells both in vitro and in vivo. Taken together, aberrant expression of SIPA1 resulted in the alteration of glucose metabolism from oxidative phosphorylation to aerobic glycolysis even at ambient oxygen levels, which might aggravate the malignancy of breast cancer cells. The present findings indicate a potential target for the development of therapeutics against breast cancers with dysregulated SIPA1 expression.

Circ_0085495 knockdown reduces adriamycin resistance in breast cancer through miR-873-5p/integrin β1 axis

Circular RNAs (circRNAs) are reported to be related to cancer chemoresistance. However, the role of circ_0085495 in adriamycin (ADM) and its action mechanism has not been elucidated in breast cancer. Cell counting kit-8 was employed to detect cell viability. Quantitative real-time-PCR and western blot were performed to examine the gene and protein expression level. Flow cytometry and colony formation assay were conducted to measure cell apoptosis and proliferation. Cell migration and invasion were evaluated via transwell assay. The target association between molecules was confirmed by dual-luciferase reporter, RNA immunoprecipitation and RNA pull-down assays. Tumor xenograft assay was implemented to explore the role of circ_0085495 in vivo. Circ_0085495 and Integrin β1 were upregulated, while miR-873-5p was downregulated in ADM-resistant cells. Circ_0085495 was a stable circRNA, mainly located in the cytoplasm. Depletion of circ_0085495 repressed ADM resistance, proliferation and metastasis of ADM-resistant breast cancer cells, which was weakened by miR-873-5p inhibition or integrin β1 overexpression. Circ_0085495 sponged miR-873-5p to positively regulate integrin β1 expression. Integrin β1 knockdown also inhibited ADM resistance. Furthermore, circ_0085495 knockdown inhibited tumor growth in vivo. Circ_0085495 knockdown reduced ADM resistance in ADM-resistant cells through modulating miR-873-5p/integrin β1 axis, indicating circ_0085495 as a promising target for overcoming ADM resistance in breast cancer patients.

SIPA1 boosts migration and proliferation, and blocks apoptosis of glioma by activating the phosphorylation of the FAK signaling pathway

Background

We aimed to analyze the regulatory effects of SIPA1 (signal-induced proliferation-associated protein 1) on glioma progression and the dominant signaling pathway.

Methods

Differential level of SIPA1 in glioma and normal tissues and cells was determined. Migratory, proliferative, apoptotic and cell cycle progression changes in A172 cells with overexpression or knockdown of SIPA1 were examined. Finally, protein levels of phosphorylated FAKs in A172 cells intervened by SIPA1, and the FAK inhibitor PF562271 were detected.

Results

SIPA1 was upregulated in glioma cases. Knock-down of SIPA1 reduced migratory and proliferative rates of glioma cells, increased apoptotic cell rate, and declined cell ratio in the S phase. The knockdown of SIPA1 also downregulated cell cycle proteins. In addition, SIPA1 upregulated phosphorylated FAKs in A172 cells and thus boosted malignant phenotypes of glioma.

Conclusions

SIPA1 is upregulated in glioma that boosts migratory and proliferative potentials of glioma cells by activating the phosphorylation of the FAK signaling pathway.

SIPA1 Is a Modulator of HGF/MET Induced Tumour Metastasis via the Regulation of Tight Junction-Based Cell to Cell Barrier Function

BACKGROUND

Lung cancer is the leading cause of cancer death. SIPA1 is a mitogen induced GTPase activating protein (GAP) and may hamper cell cycle progression. SIPA1 has been shown to be involved in MET signaling and may contribute to tight junction (TJ) function and cancer metastasis.

METHODS

Human lung tumour cohorts were analyzed. In vitro cell function assays were performed after knock down of SIPA1 in lung cancer cells with/without treatment. Quantitative polymerase chain reaction (qPCR) and western blotting were performed to analyze expression of HGF (hepatocyte growth factor), MET, and their downstream markers. Immunohistochemistry (IHC) and immunofluorescence (IFC) staining were performed.

RESULTS

Higher expression of SIPA1 in lung tumours was associated with a poorer prognosis. Knockdown of SIPA1 decreased invasiveness and proliferation of in vitro cell lines, and the SIPA1 knockdown cells demonstrated leaky barriers. Knockdown of SIPA1 decreased tight junction-based barrier function by downregulating MET at the protein but not the transcript level, through silencing of Grb2, SOCS, and PKCμ (Protein kinase Cµ), reducing the internalization and recycling of MET. Elevated levels of SIPA1 protein are correlated with receptor tyrosine kinases (RTKs), especially HGF/MET and TJs. The regulation of HGF on barrier function and invasion required the presence of SIPA1.

CONCLUSIONS

SIPA1 plays an essential role in lung tumourigenesis and metastasis. SIPA1 may be a diagnostic and prognostic predictive biomarker. SIPA1 may also be a potential therapeutic target for non-small cell lung cancer (NSCLC) patients with aberrant MET expression and drug resistance.

A novel nuclear localization region in SIPA1 determines protein nuclear distribution and epirubicin-sensitivity of breast cancer cells

Signal-induced proliferation-associated protein 1 (SIPA1) is highly expressed and mainly located in the nucleus in some breast cancer cell lines and clinical tumor tissues. Previous study revealed that nuclear localization of SIPA1 is functionally involved in breast cancer metastasis in the lymphatic gland. In the current study, we identified a non-typical region (140-179aa) of SIPA1 as a novel nuclear localization region (NLR) which is crucial for translocating the proteins into the nucleus in HEK293 cells and breast cancer cells. This region contained one basic amino acid, His160, and had no common features of typical nuclear localization signals. In addition, overexpressing SIPA1 without NLR could suppress breast cancer cell proliferation but could not promote cell migration in MCF7 cells. Furthermore, we found that a high expression of SIPA1 upregulated the expression of ABCB1, encoding multi-drug resistance protein MDR1, and promoted the resistance to epirubicin in breast cancer cells, while this effect was largely abolished in the cells with the expression of NLR-deleted SIPA1. This study overall, identified a nuclear localization-dependent region determining the nuclear distribution of SIPA1 and its regulation on epirubicin-sensitivity in breast cancer cells, which could be a potential drug target to facilitate the development of breast cancer chemotherapy.

Focal Adhesion Kinase Fine Tunes Multifaced Signals toward Breast Cancer Progression

Breast cancer represents the most common diagnosed malignancy and the main leading cause of tumor-related death among women worldwide. Therefore, several efforts have been made in order to identify valuable molecular biomarkers for the prognosis and prediction of therapeutic responses in breast tumor patients. In this context, emerging discoveries have indicated that focal adhesion kinase (FAK), a non-receptor tyrosine kinase, might represent a promising target involved in breast tumorigenesis. Of note, high FAK expression and activity have been tightly correlated with a poor clinical outcome and metastatic features in several tumors, including breast cancer. Recently, a role for the integrin-FAK signaling in mechanotransduction has been suggested and the function of FAK within the breast tumor microenvironment has been ascertained toward tumor angiogenesis and vascular permeability. FAK has been also involved in cancer stem cells (CSCs)-mediated initiation, maintenance and therapeutic responses of breast tumors. In addition, the potential of FAK to elicit breast tumor-promoting effects has been even associated with the capability to modulate immune responses. On the basis of these findings, several agents targeting FAK have been exploited in diverse preclinical tumor models. Here, we recapitulate the multifaceted action exerted by FAK and its prognostic significance in breast cancer. Moreover, we highlight the recent clinical evidence regarding the usefulness of FAK inhibitors in the treatment of breast tumors.

Topographical and Biomechanical Guidance of Electrospun Fibers for Biomedical Applications

Electrospinning is gaining increasing interest in the biomedical field as an eco-friendly and economic technique for production of random and oriented polymeric fibers. The aim of this review was to give an overview of electrospinning potentialities in the production of fibers for biomedical applications with a focus on the possibility to combine biomechanical and topographical stimuli. In fact, selection of the polymer and the eventual surface modification of the fibers allow selection of the proper chemical/biological signal to be administered to the cells. Moreover, a proper design of fiber orientation, dimension, and topography can give the opportunity to drive cell growth also from a spatial standpoint. At this purpose, the review contains a first introduction on potentialities of electrospinning for the obtainment of random and oriented fibers both with synthetic and natural polymers. The biological phenomena which can be guided and promoted by fibers composition and topography are in depth investigated and discussed in the second section of the paper. Finally, the recent strategies developed in the scientific community for the realization of electrospun fibers and for their surface modification for biomedical application are presented and discussed in the last section.

SIPA1 enhances SMAD2/3 expression to maintain stem cell features in breast cancer cells

SIPA1, a GTPase activating protein that negatively regulates Ras-related protein (Rap), is a potential modulator of tumor metastasis and recurrence. In this study, we first showed that SIPA1 facilitated the stemness features of breast cancer cells, such as of tumorsphere formation capability and the expression of stemness marker CD44. In addition, SIPA1 promoted the expression of four stemness-associated transcription factors through increasing the expression of SMAD2 and SMAD3 in vitro and in vivo. The stemness features were abolished by blocking the phosphorylation of SMAD3 with its specific inhibitor SIS3. Furthermore, SIPA1 decreased the breast cancer cell sensitivity to chemotherapy drugs. This effect was, however, competitively reversed by blocking the SMAD3 phosphorylation by SIS3 treatment in breast cancer cells. Taken together, SIPA1 promotes and sustains the stemness of breast cancer cells and their resistance to chemotherapy by increasing the expression of SMAD2 and SMAD3, and blocking SMAD3 phosphorylation could suppress the cancer cell stemness and increase the sensitivity to chemotherapy in breast cancer cells expressing a high level of SIPA1.

Potential Diagnostic and Prognostic Utility of miR-141, miR-181b1, and miR-23b in Breast Cancer

miRNAs, a group of short noncoding RNAs, are key regulators of fundamental cellular processes and signaling pathways. Dysregulation of miRNA expression with known oncogenic or tumor suppressor functions has been associated with neoplastic transformation. Numerous studies have reported dysregulation of miRNA-141, miR-181b1, and miR-23b in a wide range of malignancies, including breast cancer. To the best of our knowledge, no previous study had demonstrated the expression of miR-141-3p, miR-181b1-5p, and miR-23b-3p in different histological grades and molecular subtypes of breast cancer. Here, we identified differential expression of these three miRNAs in breast cancer tissues compared with benign breast fibroadenomas. In addition, high expression levels of miR-141-3p and miR-181b1-5p are strongly associated with aggressive breast carcinomas. We also confirmed the clinical potential of using the three miRNAs individually or combined as diagnostic and prognostic markers in breast cancer. Using bioinformatics analyses, we identified 23 hub genes of these three miRNAs which are involved in key signaling pathways in breast cancer. Furthermore, the KM plotter online database analysis demonstrates the association between elevated expression of miR-141 and miR-181b and shorter overall survival of breast cancer patients. Together, our data suggest an oncogenic role of the studied miRNAs and highlight their molecular roles and potential clinical applications in breast cancer.

The role of SIPA1 in the development of cancer and metastases (Review)

Cancer is a leading cause of mortality and the majority of deaths are due to metastases. Many molecules have been implicated in the development of metastases. Signal induced proliferation associated protein 1 (SIPA1), a mitogen-inducible gene, has been demonstrated to be involved in the metastasis of various solid tumours and may indicate a poor prognosis. Polymorphisms of SIPA1 can be associated with several different types of cancer and interactions between SIPA1 and binding molecules integrate a series of cellular functions, which may promote the development and metastasis of cancer. The mechanisms by which SIPA1 promotes the development and metastasis of cancer varies among tumour types. The present review describes the structure, function and regulation of SIPA1 and focuses on its role in cancer metastasis. Possibilities for future research and the clinical application of SIPA1 are also discussed.

Identification of the fatty acid synthase interaction network via iTRAQ-based proteomics indicates the potential molecular mechanisms of liver cancer metastasis

Background

Fatty acid synthase (FASN) is highly expressed in various types of cancer and has an important role in carcinogenesis and metastasis. To clarify the mechanisms of FASN in liver cancer invasion and metastasis, the FASN protein interaction network in liver cancer was identified by targeted proteomic analysis.

Methods

Wound healing and Transwell assays was performed to observe the effect of FASN during migration and invasion in liver cancer. Isobaric tags for relative and absolute quantitation (iTRAQ)-based mass spectrometry were used to identify proteins interacting with FASN in HepG2 cells. Differential expressed proteins were validated by co-immunoprecipitation, western blot analyses and confocal microscopy. Western blot and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) were performed to demonstrate the mechanism of FASN regulating metastasis.

Results

FASN knockdown inhibited migration and invasion of HepG2 and SMMC7721 cells. A total of, 79 proteins interacting with FASN were identified. Additionally, gene ontology term enrichment analysis indicated that the majority of biological regulation and cellular processes that the FASN-interacting proteins were associated with. Co-precipitation and co-localization of FASN with fascin actin-bundling protein 1 (FSCN1), signal-induced proliferation-associated 1 (SIPA1), spectrin β, non-erythrocytic 1 (SPTBN1) and CD59 were evaluated. Knockdown of FASN in liver cancer reduced the expression of FSCN1, SIPA1, SPTBN1 and CD59. Furthermore, inhibition of FASN, FSCN1 or SPTBN1 expression in liver cancer resulted in alterations of epithelial–mesenchymal transition (EMT)-associated markers E-cadherin, N-cadherin, vimentin and transcription factors, Snail and Twist, at the mRNA level, and changes in matrix metallopeptidase (MMP)-2 and MMP-9 protein expression.

Conclusion

The results suggested that the FASN-interacting protein network produced by iTRAQ-based proteomic analyses may be involved in regulating invasion and metastasis in liver cancer by influencing EMT and the function of MMPs.

5-Aza-2'-deoxycytidine advances the epithelial-mesenchymal transition of breast cancer cells by demethylating Sipa1 promoter-proximal elements

Human breast cancer cells exhibit considerable diversity in the methylation status of genomic DNA CpGs that regulate metastatic transcriptome networks. In this study, we identified human Sipa1 promoter-proximal elements that contained a CpG island and demonstrated that the methylation status of the CpG island was inversely correlated with SIPA1 protein expression in cancer cells. 5-Aza-2′-deoxycytidine (5-Aza-CdR), a DNA methyltransferase inhibitor, promoted the expression of Sipa1 in the MCF7 breast cancer cells with a low level of SIPA1 expression. On the contrary, in MDA-MB-231 breast cancer cells with high SIPA1 expression levels, hypermethylation of the CpG island negatively regulated the transcription of Sipa1. In addition, the epithelial–mesenchymal transition (EMT) was reversed after knocking down Sipa1 in MDA-MB-231 cells. However, the EMT was promoted in MCF7 cells with over-expression of SIPA1 or treated with 5-Aza-CdR. Taken together, hypomethylation of the CpG island in Sipa1 promoter-proximal elements could enhance SIPA1 expression in breast cancer cells, which could facilitate EMT of cancer cells, possibly increasing a risk of cancer cell metastasis in individuals treated with 5-Aza-CdR.

Summary: Hypomethylation by 5-Aza-CdR upregulates the SIPA1 expression and promotes epithelial–mesenchymal transition in breast cancer cells, possibly increasing the risk of cancer cell metastasis.

FRK suppresses human glioma growth by inhibiting ITGB1/FAK signaling

Fyn-related kinase (FRK), a member of the Src-related tyrosine kinase family, functions as a tumor suppressor in several malignancies. We previously showed that FRK overexpression inhibited the growth of glioma cells. However, it is unknown whether FRK is equally effective against intracranial glioma in vivo, and the mechanism by which FRK influences glioma cell growth remains unclear. In this study, we found that tumor volume was reduced by about one-third in mice with FRK overexpression, which showed improved survival relative to controls. Immunofluorescence analysis revealed that FRK overexpression inhibited glioma cell proliferation and induced their apoptosis. Importantly, in vitro we further found that FRK decreased the expression of integrin subunit β1 (ITGB1) at both the mRNA and protein levels. FRK also inhibited transactivation by ITGB1, resulting in the suppression of its target proteins AKT and focal adhesion kinase (FAK). ITGB1 overexpression promoted glioma cell growth and partially reduced FRK-induced growth suppression. These results indicate that FRK inhibits human glioma growth via regulating ITGB1/FAK signaling and provide a potential therapeutic target for the treatment of glioma.

Whole-Exome Sequencing Identifies Somatic Mutations Associated With Mortality in Metastatic Clear Cell Kidney Carcinoma

Clear cell renal cell carcinoma (ccRCC) is among the most aggressive histologic subtypes of kidney cancer, representing about 3% of all human cancers. Patients at stage IV have nearly 60% of mortality in 2–3 years after diagnosis. To date, most ccRCC studies have used DNA microarrays and targeted sequencing of a small set of well-established, commonly altered genes. An exception is the large multi-omics study of The Cancer Genome Atlas Kidney Renal Clear Cell Carcinoma (TCGA-KIRC), which identified new ccRCC genes based on whole exome-sequencing (WES) data, and molecular prognostic signatures based on transcriptomics, epigenetics and proteomics data. Applying WES to simultaneously interrogate virtually all exons in the human genome for somatic variation, here we analyzed the burden of coding somatic mutations in metastatic ccRCC primary tumors, and its association with patient mortality from cancer, in patients who received VEGF receptor-targeting drugs as the first-line therapy. To this end, we sequenced the exomes of ten tumor–normal pairs of ccRCC patient tissues from primary biopsies at >100× mean depth and called somatic coding variation. Mutation burden analysis prioritized 138 genes linked to patient mortality. A gene set enrichment analysis evidenced strong statistical support for the abundance of genes involved in the development of kidney cancer (p = 2.31 × 10⁻⁹) and carcinoma (p = 1.22 × 10⁻⁵), with 49 genes having direct links with kidney cancer according to the published records. Two of these genes, SIPA1L2 and EIF3A, demonstrated independent associations with mortality in TCGA-KIRC project data. Besides, three mutational signatures were found to be operative in the tumor exomes, one of which (COSMIC signature 12) has not been previously reported in ccRCC. Selection analysis yielded no detectable evidence of overall positive or negative selection, with the exome-wide number of nonsynonymous substitutions per synonymous site reflecting largely neutral tumor evolution. Despite the limited sample size, our results provide evidence for candidate genes where somatic mutation burden is tentatively associated with patient mortality in metastatic ccRCC, offering new potential pharmacological targets and a basis for further validation studies.

Downregulation of Rap1Gap: A Switch from DCIS to Invasive Breast Carcinoma via ERK/MAPK Activation

Diagnosis of breast ductal carcinoma in situ (DCIS) presents a challenge since we cannot yet distinguish those cases that would remain indolent and not require aggressive treatment from cases that may progress to invasive ductal cancer (IDC). The purpose of this study is to determine the role of Rap1Gap, a GTPase activating protein, in the progression from DCIS to IDC. Immunohistochemistry (IHC) analysis of samples from breast cancer patients shows an increase in Rap1Gap expression in DCIS compared to normal breast tissue and IDCs. In order to study the mechanisms of malignant progression, we employed an in vitro three-dimensional (3D) model that more accurately recapitulates both structural and functional cues of breast tissue. Immunoblotting results show that Rap1Gap levels in MCF10.Ca1D cells (a model of invasive carcinoma) are reduced compared to those in MCF10.DCIS (a model of DCIS). Retroviral silencing of Rap1Gap in MCF10.DCIS cells activated extracellular regulated kinase (ERK) mitogen-activated protein kinase (MAPK), induced extensive cytoskeletal reorganization and acquisition of mesenchymal phenotype, and enhanced invasion. Enforced reexpression of Rap1Gap in MCF10.DCIS-Rap1GapshRNA cells reduced Rap1 activity and reversed the mesenchymal phenotype. Similarly, introduction of dominant negative Rap1A mutant (Rap1A-N17) in DCIS-Rap1Gap shRNA cells caused a reversion to nonmalignant phenotype. Conversely, expression of constitutively active Rap1A mutant (Rap1A-V12) in noninvasive MCF10.DCIS cells led to phenotypic changes that were reminiscent of Rap1Gap knockdown. Thus, reduction of Rap1Gap in DCIS is a potential switch for progression to an invasive phenotype. The Graphical Abstract summarizes these findings.

APE1/Ref-1 knockdown in pancreatic ductal adenocarcinoma - characterizing gene expression changes and identifying novel pathways using single-cell RNA sequencing

Apurinic/apyrimidinic endonuclease 1/redox factor-1 (APE1/Ref-1 or APE1) is a multifunctional protein that regulates numerous transcription factors associated with cancer-related pathways. Because APE1 is essential for cell viability, generation of APE1-knockout cell lines and determining a comprehensive list of genes regulated by APE1 has not been possible. To circumvent this challenge, we utilized single-cell RNA sequencing to identify differentially expressed genes (DEGs) in relation to APE1 protein levels within the cell. Using a straightforward yet novel statistical design, we identified 2837 genes whose expression is significantly changed following APE1 knockdown. Using this gene expression profile, we identified multiple new pathways not previously linked to APE1, including the EIF2 signaling and mechanistic target of Rapamycin pathways and a number of mitochondrial-related pathways. We demonstrate that APE1 has an effect on modifying gene expression up to a threshold of APE1 expression, demonstrating that it is not necessary to completely knockout APE1 in cells to accurately study APE1 function. We validated the findings using a selection of the DEGs along with siRNA knockdown and qRT-PCR. Testing additional patient-derived pancreatic cancer cells reveals particular genes (ITGA1, TNFAIP2, COMMD7, RAB3D) that respond to APE1 knockdown similarly across all the cell lines. Furthermore, we verified that the redox function of APE1 was responsible for driving gene expression of mitochondrial genes such as PRDX5 and genes that are important for proliferation such as SIPA1 and RAB3D by treating with APE1 redox-specific inhibitor, APX3330. Our study identifies several novel genes and pathways affected by APE1, as well as tumor subtype specificity. These findings will allow for hypothesis-driven approaches to generate combination therapies using, for example, APE1 inhibitor APX3330 with other approved FDA drugs in an innovative manner for pancreatic and other cancer treatments.

The cancer cell adhesion resistome: mechanisms, targeting and translational approaches

Cell adhesion-mediated resistance limits the success of cancer therapies and is a great obstacle to overcome in the clinic. Since the 1990s, where it became clear that adhesion of tumor cells to the extracellular matrix is an important mediator of therapy resistance, a lot of work has been conducted to understand the fundamental underlying mechanisms and two paradigms were deduced: cell adhesion-mediated radioresistance (CAM-RR) and cell adhesion-mediated drug resistance (CAM-DR). Preclinical work has evidently demonstrated that targeting of integrins, adapter proteins and associated kinases comprising the cell adhesion resistome is a promising strategy to sensitize cancer cells to both radiotherapy and chemotherapy. Moreover, the cell adhesion resistome fundamentally contributes to adaptation mechanisms induced by radiochemotherapy as well as molecular drugs to secure a balanced homeostasis of cancer cells for survival and growth. Intriguingly, this phenomenon provides a basis for synthetic lethal targeted therapies simultaneously administered to standard radiochemotherapy. In this review, we summarize current knowledge about the cell adhesion resistome and highlight targeting strategies to override CAM-RR and CAM-DR.

FOXM1 transcriptionally regulates expression of integrin β1 in triple-negative breast cancer

PURPOSE

Triple-negative breast cancer (TNBC) is an aggressive type of breast cancer and associated with early metastasis, drug resistance, and poor patient survival. Fork head box M1 (FOXM1) is considered as an emerging molecular target due to its oncogenic role and high overexpression profile in 85% in TNBC. However, molecular mechanisms by which FOXM1 transcription factor mediate its oncogenic effects are not fully understood. Integrin β1 is often upregulated in invasive breast cancers and associated with poor clinical outcome and shorter overall patient survival in TNBC. However, the mechanisms regulating integrin β1 (ITGB1) gene expression have not been well elucidated.

METHODS

Normal breast epithelium (MCF10A) and TNBC cells (i.e., MDA-MB-231, BT-20 MDA-MB436) were used for the study. Small interfering RNA (siRNA)-based knockdown was used to inhibit Integrin β1 gene (mRNA) and protein expressions, which are detected by RT-PCR and Western blot, respectively. Chromatin immunoprecipitation (ChiP) and gene reporter (Luciferase) assays were used to demonstrate that FOXM1 transcription factor binds to the promoter of Integrin β1 gene and drives its expression.

RESULTS

We demonstrated that FOXM1 directly binds to the promoter of integrin β1 gene and transcriptionally regulates its expression and activity of focal adhesion kinase (FAK) in TNBC cells.

CONCLUSION

Our study suggests that FOXM1 transcription factor regulates Integrin β1 gene expression and that FOXM1/ Integrin-β1/FAK axis may play an important role in the progression of TNBC.

Roles of Rap1 signaling in tumor cell migration and invasion

Ras-associated protein-1 (Rap1), a small GTPase in the Ras-related protein family, is an important regulator of basic cellular functions (e.g., formation and control of cell adhesions and junctions), cellular migration, and polarization. Through its interaction with other proteins, Rap1 plays many roles during cell invasion and metastasis in different cancers. The basic function of Rap1 is straightforward; it acts as a switch during cellular signaling transduction and regulated by its binding to either guanosine triphosphate (GTP) or guanosine diphosphate (GDP). However, its remarkably diverse function is rendered by its interplay with a large number of distinct Rap guanine nucleotide exchange factors and Rap GTPase activating proteins. This review summarizes the mechanisms by which Rap1 signaling can regulate cell invasion and metastasis, focusing on its roles in integrin and cadherin regulation, Rho GTPase control, and matrix metalloproteinase expression.

Comparative expression study of sipa family members during early Xenopus laevis development

The signal-induced proliferation-associated (SIPA) protein family belongs to the RapGAP protein superfamily. Previous studies mainly focused on the expression and function of SIPA genes in vertebrate neuronal tissue. Only limited data about the embryonic expression pattern of the genes are currently available. Our study provides the first expression analysis of sipa1, sipa1l1, sipa1l2, and sipa1l3 during early development of the vertebrate organism Xenopus laevis. In silico, analysis revealed that all genes are highly conserved across species. Semi-quantitative RT-PCR experiments demonstrated that the RNA of all genes was maternally supplied. By whole mount in situ hybridization approaches, we showed that sipa1 is mainly expressed in various sensory organs, the respiratory and blood system, heart, neural tube, and eye. In contrast, sipa1l1 showed a broad expression during development in particular within the brain, somites, eye, and heart. Sipa1l2 was detected in the branchial arches, glomerulus, and the developing eye. In contrast, sipa1l3 revealed a tissue specific expression within the olfactory and otic vesicles, the cranial placodes and ganglia, neural tube, pronephros, retina, and lens. In summary, all sipa gene family members are expressed throughout the whole developing Xenopus organism and might play an important role during vertebrate early embryogenesis.

PIAS1-FAK Interaction Promotes the Survival and Progression of Non-Small Cell Lung Cancer

The sequence of genomic alterations acquired by cancer cells during tumor progression and metastasis is poorly understood. Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase that integrates cytoskeleton remodeling, mitogenic signaling and cell survival. FAK has previously been reported to undergo nuclear localization during cell migration, cell differentiation and apoptosis. However, the mechanism behind FAK nuclear accumulation and its contribution to tumor progression has remained elusive. We report that amplification of FAK and the SUMO E3 ligase PIAS1 gene loci frequently co-occur in non-small cell lung cancer (NSCLC) cells, and that both gene products are enriched in a subset of primary NSCLCs. We demonstrate that endogenous FAK and PIAS1 proteins interact in the cytoplasm and the cell nucleus of NSCLC cells. Ectopic expression of PIAS1 promotes proteolytic cleavage of the FAK C-terminus, focal adhesion maturation and FAK nuclear localization. Silencing of PIAS1 deregulates focal adhesion turnover, increases susceptibility to apoptosis in vitro and impairs tumor xenograft formation in vivo. Nuclear FAK in turn stimulates gene transcription favoring DNA repair, cell metabolism and cytoskeleton regulation. Consistently, ablation of FAK by CRISPR/Cas9 editing, results in basal DNA damage, susceptibility to ionizing radiation and impaired oxidative phosphorylation. Our findings provide insight into a mechanism regulating FAK cytoplasm-nuclear distribution and demonstrate that FAK activity in the nucleus promotes NSCLC survival and progression by increasing cell-ECM interaction and DNA repair regulation.

Association of four new candidate genetic variants with Parkinson's disease in a Han Chinese population

Large-scale meta-analysis of genome-wide association data has identified six new risk loci (SIPA1L2, INPP5F, MIR4697, GCH1, VPS13C, and DDRGK1) for Parkinson's disease (PD). However, the characteristics of those loci in a Han Chinese population from mainland China are unknown. We examined genetic associations of VPS13C rs2414739, MIR4697 rs329648, GCH1 rs11158026, and SIPA1L2 rs10797576 with PD susceptibility in a Han Chinese population of 1028 sporadic PD patients and 1109 healthy controls. All subjects were genotyped for these loci using the Sequenom iPLEX Assay. We also conducted further stratified analysis according to age at onset and compared the clinical characteristics between minor allele carriers and non-carriers for each locus. However, we did not observe any significant difference in genotype distribution between PD patients and controls for the four loci, even after being stratified by age at onset. Besides, minor allele carriers cannot be distinguished from non-carriers based on their clinical features. Our findings first demonstrated that VPS13C rs2414739, MIR4697 rs329648, GCH1 rs11158026, and SIPA1L2 rs10797576 do not confer a significant risk for PD in Chinese population. Additional replication studies in other populations and functional studies are warranted to better validate the role of the four new loci in PD risk.

CC chemokine ligand 18(CCL18) promotes migration and invasion of lung cancer cells by binding to Nir1 through Nir1-ELMO1/DOC180 signaling pathway

Non-small cell lung cancer (NSCLC) comprises nearly 80% of lung cancers and the poor prognosis is due to its high invasiveness and metastasis. CC chemokine ligand 18 (CCL18) is predominantly secreted by M2-tumor associated macrophages (TAMs) and promotes malignant behaviors of various human cancer types. In this study, we report that the high expression of CCL18 in TAMs of NSCLC tissues and increased expression of CCL18 in TAMs is correlated with the lymph node metastasis, distant metastasis, and poor prognosis NSCLC patients. CCL18 can increase the invasive ability of NSCLC cells by binding to its receptor Nir1. In addition, CCL18 is capable of modulating cell migration and invasion by regulating the activation of RAC1 which resulted in cytoskeleton reorganization in an ELMO1 dependent manner. Furthermore, we found that CCL18 could enhance adhesion of NSCLC cells via activating ELMO1-integrin β1 signaling. Thus, CCL18 and its downstream molecules may be used as targets to develop novel NSCLC therapy. © 2016 Wiley Periodicals, Inc.

Distinct effects of β1 integrin on cell proliferation and cellular signaling in MDA-MB-231 breast cancer cells

An aberrant expression of integrin β1 has been implicated in breast cancer progression. Here, we compared the cell behaviors of wild-type (WT), β1 gene deleted (KO), and β1 gene restored (Res) MDA-MB-231 cells. Surprisingly, the expression of β1 exhibited opposite effects on cell proliferation. These effects were dependent on cell densities, and they showed an up-regulation of cell proliferation when cells were cultured under sparse conditions, and a down-regulation of cell growth under dense conditions. By comparison with WT cells, the phosphorylation levels of ERK in KO cells were consistently suppressed under sparse culture conditions, but consistently up-regulated under dense culture conditions. The phosphorylation levels of EGFR were increased in the KO cells. By contrast, the phosphorylation levels of AKT were decreased in the KO cells. The abilities for both colony and tumor formation were significantly suppressed in the KO cells, suggesting that β1 plays an important role in cell survival signaling for tumorigenesis. These aberrant phenotypes in the KO cells were rescued in the Res cells. Taken together, these results clearly showed the distinct roles of β1 in cancer cells: the inhibition of cell growth and the promotion of cell survival, which may shed light on cancer therapies.

Definition of a consensus integrin adhesome and its dynamics during adhesion complex assembly and disassembly

Integrin receptor activation initiates the formation of integrin adhesion complexes (IACs) at the cell membrane that transduce adhesion-dependent signals to control a multitude of cellular functions. Proteomic analyses of isolated IACs have revealed an unanticipated molecular complexity; however, a global view of the consensus composition and dynamics of IACs is lacking. Here, we have integrated several IAC proteomes and generated a 2,412-protein integrin adhesome. Analysis of this data set reveals the functional diversity of proteins in IACs and establishes a consensus adhesome of 60 proteins. The consensus adhesome is likely to represent a core cell adhesion machinery, centred around four axes comprising ILK-PINCH-kindlin, FAK-paxillin, talin-vinculin and α-actinin-zyxin-VASP, and includes underappreciated IAC components such as Rsu-1 and caldesmon. Proteomic quantification of IAC assembly and disassembly detailed the compositional dynamics of the core cell adhesion machinery. The definition of this consensus view of integrin adhesome components provides a resource for the research community.

Suppression of SIPA-1 expression may reduce bladder cancer invasion and metastasis via the downregulation of E-cadherin and ZO-1

The aim of the present study was to investigate the capacity of signal-induced proliferation-associated protein 1 (SIPA-1) to regulate bladder cancer cell invasion and metastasis. BIU-87 and T24 cells were transfected with the SIPA gene and SIPA short hairpin (sh)RNA, respectively. Western blot analysis was conducted to analyze the expression levels of SIPA-1, Ras-related protein 1 (Rap1), Rap1 guanosine triphosphate (Rap1GTP), E-cadherin and zona occludens-1 (ZO-1). Cell motility and invasion were evaluated in vitro using wound and Transwell assays. Transfected cells were inoculated into the pelvic region of BALB/c nude mice, and the number of resulting tumors was recorded after 6 weeks. Western blot analysis revealed that expression levels of E-cadherin and ZO-1 were reduced in the cells with enhanced levels of SIPA-1. By contrast, the levels of E-cadherin and ZO-1 were elevated in the cells in which SIPA-1 was knocked down. In comparison with untransfected cells, the cells with reduced levels of SIPA-1 exhibited reduced wound closure and fewer cells crossed the chamber in the Transwell experiment, whereas the cells with enhanced levels of SIPA-1 exhibited increased migration and invasion In vivo, an increased tumor count was obtained in the mice with elevated levels of SIPA-1. Therefore, the results of the present study indicate that SIPA-1 is able to regulate bladder cancer cell metastasis and invasion by reducing the expression of E-cadherin and ZO-1.

MiR-183 Regulates ITGB1P Expression and Promotes Invasion of Endometrial Stromal Cells

We applied in the previous study miRNA microarray screening analysis to identify several differentially expressed miRNAs, including miR-183 in normal, eutopic, and ectopic endometrium. Knockdown of miR-183 expression induced the invasiveness and inhibition of apoptosis in endometrial stromal cells. The current study aims to identify the miR-183 targets with relevance to cell functions in endometrial stromal cells, to verify the interaction of miR-183 with its target genes, and to confirm the role of miR-183 in the process of endometriosis. Using microarray analysis, we identified 27 differentially expressed genes (19 were upregulated and 8 downregulated), from which we selected 4 downregulated genes (ITGB1, AMIGO2, VAV3, and PSEN2) based on GO databases for functional analysis and significant pathway analysis. Western blotting analyses showed that integrin β1 (ITGB1), but not AMIGO2, was affected by miR-183 overexpression, whereas no protein expression of VAV3 and PSEN2 was detected. Luciferase reporter assay verified that ITGB1 is a target gene of miR-183. Moreover, we found that ITGB1 is overexpressed in the endometrium of endometriosis patients. Furthermore, overexpression of ITGB1 rescued the repressive effects of miR-183 on the invasiveness of endometrial stromal cells. These findings, together with the fact that ITGB1 is a critical factor for cell adhesion and invasiveness, suggest that miR-183 may be involved in the development of endometriosis by regulating ITGB1 in endometrial stromal cells.

The role of individual inheritance in tumor progression and metastasis

Metastasis, the dissemination and growth of tumor cells at secondary sites, is the primary cause of patient mortality from solid tumors. Metastasis is an extremely complex, inefficient process requiring contributions of not only the tumor cell but also local and distant environmental factors, at both the cellular and molecular level. Variation in the function of any of the steps in the metastatic cascade may therefore have profound implications for the ultimate course of the disease. In addition to the somatic and cellular heterogeneity that can affect cancer outcome, an individual's specific ancestry or genetic background can also significantly influence metastatic progression. These inherited variants not only encoded for metastatic susceptibility but also provided a window to study critical factors that are not easily accessible with current technologies. Furthermore, investigations into inherited metastatic susceptibility enable identification of important molecular and cellular processes that are not subject to mutation and are consequently not detectable by standard cancer genome sequencing strategies. Incorporation of inherited variation into metastasis research therefore provides methods to more comprehensively investigate the etiology of the lethal consequences of tumor progression.

The SIPA1 -313A>G polymorphism is associated with prognosis in inoperable non-small cell lung cancer

Polymorphism in signal-induced proliferation-associated 1 (SIPA1) gene may contribute to the development of metastasis in human cancers. In this preliminary study, we examined the association of the SIPA1 -313A>G (rs931127) polymorphism with overall survival (OS) and progression-free survival (PFS) in 351 inoperable patients with non-small cell lung cancer (NSCLC) treated with radiotherapy or radiochemotherapy (curative or palliative). The GG homozygotes had significantly shorter PFS under codominant and recessive models in all patients (hazard ratio (HR) 1.47, p = 0.035, and HR 1.47, p = 0.022, respectively) and in advanced stage subgroup (HR 1.49, p = 0.037, and HR 1.48, p = 0.023, respectively). The GG genotype was also associated with reduced OS and PFS (codominant model: HR 2.41, p = 0.020, and HR 2.34, p = 0.020, respectively; recessive model: HR 2.16, p = 0.026, and HR 2.18, p = 0.022, respectively) in radiotherapy alone subgroup. Moreover, the SIPA1 -313GG was identified as an independent adverse prognostic factor for PFS in the cohort. Our results indicate, for the first time, that the SIPA1 -313A>G may have a prognostic role in unresected NSCLC making it a potential predictor of poor survival due to earlier progression.