HER2/ErbB2-induced breast cancer cell migration and invasion require p120 catenin activation of Rac1 and Cdc42

Functions of p120-catenin in physiology and diseases

p120-catenin (p120) plays a vital role in regulating cell-cell adhesion at adherens junctions, interacting with the juxtamembrane domain (JMD) core region of E-cadherin and regulates the stability of cadherin at the cell surface. Previous studies have shown significant functions of p120 in cell-cell adhesion, tumor progression and inflammation. In this review, we will discuss recent progress of p120 in physiological processes and diseases, and focus on the functions of p120 in the regulation of cancer and inflammation.

Cdc42-driven endosomal cholesterol transport promotes collateral resistance in HER2-positive gastric cancer

Resistance to trastuzumab and the poor efficacy of subsequent chemotherapy have become major challenges for HER2-positive gastric cancer (GC). As resistance evolves, tumor cells may acquire a new drug susceptibility profile, profoundly impacting the subsequent treatment selection and patient survival. However, the interplay between trastuzumab and other types of drugs in HER2-positive GC remains elusive. In our study, we utilized resistant cell lines and tissue specimens to map the drug susceptibility profile of trastuzumab-resistant GC, discovering that resistance to trastuzumab induces collateral resistance to commonly used chemotherapeutic agents. Additionally, patients with collateral resistance distinguished by a 13-gene scoring model in HER2-positive GC cohorts are predicted to have a poor prognosis and may be sensitive to cholesterol-lowering drugs. Mechanistically, endosomal cholesterol transport is further confirmed to enrich cholesterol in the plasma membrane, contributing to collateral resistance through the Hedgehog-ABCB1 axis. As a driver for cholesterol, Cdc42 is activated by the formation of the NPC1-TβRI-Cdc42 complex to facilitate endosomal cholesterol transport. We demonstrated that inhibiting Cdc42 activation with ZCL278 reduces cholesterol levels in the plasma membrane and reverses collateral resistance between trastuzumab and chemotherapy in vitro and in vivo. Collectively, our findings verify the phenomena and mechanism of collateral resistance between trastuzumab and chemotherapy, and propose a potential therapeutic target and strategy in the second-line treatment for trastuzumab-resistant HER2-positive GC.

The distinct localization of CDC42 isoforms is responsible for their specific functions during migration

The small G-protein CDC42 is an evolutionary conserved polarity protein and a key regulator of polarized cell functions, including directed cell migration. In vertebrates, alternative splicing gives rise to two CDC42 proteins: the ubiquitously expressed isoform (CDC42u) and the brain isoform (CDC42b), which only differ in their carboxy-terminal sequence, including the CAAX motif essential for their association with membranes. We show that these divergent sequences do not directly affect the range of CDC42's potential binding partners but indirectly influence CDC42-driven signaling by controlling the subcellular localization of the two isoforms. In astrocytes and neural precursors, which naturally express both variants, CDC42u associates with the leading-edge plasma membrane of migrating cells, where it recruits the Par6-PKCζ complex to fulfill its polarity function. In contrast, CDC42b mainly localizes to intracellular membrane compartments, where it regulates N-WASP-mediated endocytosis. Both CDC42 isoforms contribute their specific functions to promote the chemotaxis of neural precursors, demonstrating that their expression pattern is decisive for tissue-specific cell behavior.

Network pharmacology-integrated molecular docking analysis of phytocompounds of Caesalpinia pulcherrima (peacock flower) as potential anti-metastatic agents

Caesalpinia pulcherrima, or peacock flower, has been a subject of cancer therapeutics research, showing promising anti-cancer and anti-metastatic properties. The present research aims to investigate the anti-metastatic potential of the flower, through bioinformatics approaches. Metastasis targets numbering 471 were identified through overlap analysis following NCBI gene, Gene Card and OMIM query. Phytocompounds of the flower were retrieved from PubChem and their protein interactions predicted using Super-PRED and TargetNet. The 28 targets that overlapped with the predicted proteins were used to generate STRING >0.7. Enrichment analysis revealed that C. pulcherrima may inhibit metastasis through angiogenesis-related and leukocyte migration-related pathways. HSP90AA1, ESR1, PIK3CA, ERBB2, KDR and MMP9 were identified as potential core targets while and 6 compounds (3-[(4-Hydroxyphenyl)methylidene]-7,8-dimethoxychromen-4-one (163076213), clotrimazole (2812), Isovouacapenol A (636673), [(4aR,5R,6aS,7R,11aS,11bR)-4a-hydroxy-4,4,7,11b-tetramethyl-9-oxo-1,2,3,5,6,6a,7,11a-octahydronaphtho[2,1-f][1]benzofuran-5-yl] benzoate (163104827), Stigmast-5-en-3beta-ol (86821) and 4,2'-dihydroxy-4'-methoxychalcone (592216)) were identified as potential core compounds. Molecular docking analysis and molecular dynamics simulations investigations revealed that ERBB2, HSP90AA1 and KDR, along with the newly discovered 163076213 compound to be the most significant metastasis targets and bioactive compound, respectively. These three core targets demonstrated interactions consistent with angiogenesis and leukocyte migration pathways. Furthermore, potentially novel interactions, such as KDR-MMP9, KDR-PIK3CA, ERBB2-HSP90AA1, ERBB2-ESR1, ERBB2-PIK3CA and ERBB2-MMP9 interactions were identified and may play a role in crosslinking the aforementioned metastatic pathways. Therefore, the present study revealed the main mechanisms behind the anti-metastatic effects of C. pulcherrima, paving the path for further research on these compounds and proteins to accelerate the research of cancer therapeutics and application of C. pulcherrima.Communicated by Ramaswamy H. Sarma.

Activation of invasion by oncogenic reprogramming of cholesterol metabolism via increased NPC1 expression and macropinocytosis

Cancer cells are dependent on cholesterol, and they possess strictly controlled cholesterol homeostasis mechanisms. These allow them to smoothly switch between cholesterol synthesis and uptake to fulfill their needs and to adapt environmental changes. Here we describe a mechanism of how cancer cells employ oncogenic growth factor signaling to promote uptake and utilization of extracellular cholesterol via Myeloid Zinc Finger 1 (MZF1)-mediated Niemann Pick C1 (NPC1) expression and upregulated macropinocytosis. Expression of p95ErbB2, highly oncogenic, standard-treatment resistant form of ErbB2 mobilizes lysosomes and activates EGFR, invasion and macropinocytosis. This is connected to a metabolic shift from cholesterol synthesis to uptake due to macropinocytosis-enabled flow of extracellular cholesterol. NPC1 increase facilitates extracellular cholesterol uptake and is necessary for the invasion of ErbB2 expressing breast cancer spheroids and ovarian cancer organoids, indicating a regulatory role for NPC1 in the process. The ability to obtain cholesterol as a byproduct of increased macropinocytosis allows cancer cells to direct the resources needed for the energy-consuming cholesterol synthesis towards other activities such as invasion. These results demonstrate that macropinocytosis is not only an alternative energy source for cancer cells but also an efficient way to provide building material, such as cholesterol, for its macromolecules and membranes.

Glutamine metabolic microenvironment drives M2 macrophage polarization to mediate trastuzumab resistance in HER2-positive gastric cancer

BACKGROUND

Trastuzumab is a first-line targeted therapy for human epidermal growth factor receptor-2 (HER2)-positive gastric cancer. However, the inevitable occurrence of acquired trastuzumab resistance limits the drug benefit, and there is currently no effective reversal measure. Existing researches on the mechanism of trastuzumab resistance mainly focused on tumor cells themselves, while the understanding of the mechanisms of environment-mediated drug resistance is relatively lacking. This study aimed to further explore the mechanisms of trastuzumab resistance to identify strategies to promote survival in these patients.

METHODS

Trastuzumab-sensitive and trastuzumab-resistant HER2-positive tumor tissues and cells were collected for transcriptome sequencing. Bioinformatics were used to analyze cell subtypes, metabolic pathways, and molecular signaling pathways. Changes in microenvironmental indicators (such as macrophage, angiogenesis, and metabolism) were verified by immunofluorescence (IF) and immunohistochemical (IHC) analyses. Finally, a multi-scale agent-based model (ABM) was constructed. The effects of combination treatment were further validated in nude mice to verify these effects predicted by the ABM.

RESULTS

Based on transcriptome sequencing, molecular biology, and in vivo experiments, we found that the level of glutamine metabolism in trastuzumab-resistant HER2-positive cells was increased, and glutaminase 1 (GLS1) was significantly overexpressed. Meanwhile, tumor-derived GLS1 microvesicles drove M2 macrophage polarization. Furthermore, angiogenesis promoted trastuzumab resistance. IHC showed high glutamine metabolism, M2 macrophage polarization, and angiogenesis in trastuzumab-resistant HER2-positive tumor tissues from patients and nude mice. Mechanistically, the cell division cycle 42 (CDC42) promoted GLS1 expression in tumor cells by activating nuclear factor kappa-B (NF-κB) p65 and drove GLS1 microvesicle secretion through IQ motif-containing GTPase-activating protein 1 (IQGAP1). Based on the ABM and in vivo experiments, we confirmed that the combination of anti-glutamine metabolism, anti-angiogenesis, and pro-M1 polarization therapy had the best effect in reversing trastuzumab resistance in HER2-positive gastric cancer.

CONCLUSIONS

This study revealed that tumor cells secrete GLS1 microvesicles via CDC42 to promote glutamine metabolism, M2 macrophage polarization, and pro-angiogenic function of macrophages, leading to acquired trastuzumab resistance in HER2-positive gastric cancer. A combination of anti-glutamine metabolism, anti-angiogenesis, and pro-M1 polarization therapy may provide a new insight into reversing trastuzumab resistance.

Association of lesion contour and lesion composition on MR with HER2 status in breast cancer brain metastases

BACKGROUND AND PURPOSE

With the development of HER2-directed therapies, identifying non-invasive imaging biomarkers of HER2 status in breast cancer brain metastases has become increasingly important, particularly given the risks of tissue sampling within the brain and the possibility of a change in receptor expression from the primary tumor to the brain metastasis. The purpose of this study was to evaluate whether lesion contour and composition on MR could help identify the HER2 status of breast cancer brain metastases.

MATERIALS AND METHODS

We derived a cohort of 34 women with a mean age of 55 years (range: 31-81 years) with a total of 47 distinct histologically proven breast cancer brain metastases with preoperative contrast-enhanced brain MR and HER2 immunohistochemistry and/or fluorescent in-situ hybridization (FISH) of the resected/biopsied brain specimens from 2018 to 2021. Two fellowship-trained neuroradiologists evaluated the lesion contour and lesion composition of each lesion. Logistic regression analyses were performed.

RESULTS

In a logistic regression model, an irregular contour had an odds ratio of 170 (p = 0.007) in differentiating HER2-positive from HER2-negative lesions. In a logistic regression model, when compared to a predominantly cystic lesion composition, a solid lesion composition had an odds ratio of 17 (p = 0.016) in differentiating HER2-positive from HER2-negative lesions.

CONCLUSION

Lesion contour and lesion composition on MR were significantly associated with the HER2 status of breast cancer brain metastases. Current assessment of HER2 status requires tissue sampling and immunochemical and/or FISH analyses. A non-invasive imaging biomarker that may help predict HER2 status may be of great clinical value.

Upregulation of SCD1 by ErbB2 via LDHA promotes breast cancer cell migration and invasion

The incidence of breast cancer ranks at the top of female malignant tumors in China. Metastasis remains the main cause of death among breast cancer patients. The overexpression of ErbB2 is closely related to the metastasis and poor prognosis of breast cancer patients. Therefore, ErbB2 is an important clinical therapeutic target of breast cancer. However, the molecular mechanism of ErbB2 promoting breast cancer metastasis has not been studied clearly. Stearoyl-CoA desaturase 1 (SCD1) is a key enzyme in catalyzing the conversion of saturated fatty acids (SFAs) into monounsaturated fatty acids (MUFAs). SCD1 is overexpressed in breast cancer, and its overexpression is an indicator of poor prognosis in breast cancer patients. However, the role of SCD1 in ErbB2-overexpressing breast cancer metastasis has not been reported. In this study, we investigated the role of SCD1 in the migration and invasion of ErbB2-overexpressing breast cancer cells and its molecular mechanism. First, we demonstrated that ErbB2 upregulates the expression of SCD1. Second, we found that SCD1 and its catalytic product oleic acid played crucial roles in migration and invasion of ErbB2-overexpressing breast cancer cells. Finally, we found that in breast cancer cells, ErbB2 upregulated SCD1 through lactate dehydrogenase A (LDHA). To sum up, upregulation of SCD1 by ErbB2 via LDHA promotes the migration and invasion of breast cancer cells.

Synergistic Cytotoxic and Antimigratory Effect of Brazilein and Doxorubicin on HER2-Overexpressing Cells

OBJECTIVE

The present research aims to report cytotoxic and antimigratory activities of the oxidized form of brazilin, i.e., brazilein, and the effects of the combination of brazilein-doxorubicin on MCF-7/HER2 cells.

METHODS

The MTT assay was conducted to test the cytotoxic activity, while flow cytometry with PI and PI-annexin V staining were respectively performed for cell cycle and apoptosis analyses. Migration and invasion analyses were assessed via Boyden chamber assay, while HER2, Rac1, p120, MMP2, and MMP9 protein levels were determined by immunoblotting and gelatin zymography. Molecular docking of ligands with HER2, Src, PI3Kα, PI3KΔ, and PI3Kγ proteins was evaluated using MOE 2010.

RESULTS

The MTT assay showed that the IC50 value of brazilein against MCF-7/HER2 cells was 51 ± 2.1 µM. Moreover, brazilein and its combination with doxorubicin-induced G2/M accumulation and apoptosis. Combination of brazilein-doxorubicin inhibited cell migration and tended to decrease HER2, Rac1, p120, MMP2, and MMP9 protein expression levels. Based on our molecular docking study, the docking score of brazilein with PI3Kγ is comparable to that of the native ligand.

CONCLUSION

Taken together, a combination of brazilein-doxorubicin exhibited synergistic cytotoxic and antimigratory effects on MCF-7/HER2 cells.<br />.

SH3BGRL3 binds to myosin 1c in a calcium dependent manner and modulates migration in the MDA-MB-231 cell line

Background

The human SH3 domain Binding Glutamic acid Rich Like 3 (SH3BGRL3) gene is highly conserved in phylogeny and widely expressed in human tissues. However, its function is largely undetermined. The protein was found to be overexpressed in several tumors, and recent work suggested a possible relationship with EGFR family members.

We aimed at further highlighting on these issues and investigated SH3BGRL3 molecular interactions and its role in cellular migration ability.

Results

We first engineered the ErbB2-overexpressing SKBR3 cells to express exogenous SH3BGRL3, as well as wild type Myo1c or different deletion mutants. Confocal microscopy analysis indicated that SH3BGRL3 co-localized with Myo1c and ErbB2 at plasma membranes. However, co-immunoprecipitation assays and mass spectrometry demonstrated that SH3BGRL3 did not directly bind ErbB2, but specifically recognized Myo1c, on its IQ-bearing neck region. Importantly, the interaction with Myo1c was Ca²⁺-dependent.

A role for SH3BGRL3 in cell migration was also assessed, as RNA interference of SH3BGRL3 in MDA-MB-231 cells, used as a classical migration model, remarkably impaired the migration ability of these cells. On the other side, its over-expression increased cell motility.

Conclusion

The results of this study provide insights for the formulation of novel hypotheses on the putative role of SH3BGRL3 protein in the regulation of myosin-cytoskeleton dialog and in cell migration. It could be envisaged the SH3BGRL3-Myo1c interaction as a regulation mechanism for cytoskeleton dynamics. It is well known that, at low Ca²⁺ concentrations, the IQ domains of Myo1c are bound by calmodulin. Here we found that binding of Myo1c to SH3BGRL3 requires instead the presence of Ca²⁺. Thus, it could be hypothesized that Myo1c conformation may be modulated by Ca²⁺-driven mechanisms that involve alternative binding by calmodulin or SH3BGRL3, for the regulation of cytoskeletal activity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12860-021-00379-1.

HER2 and APC Mutations Promote Altered Crypt-Villus Morphology and Marked Hyperplasia in the Intestinal Epithelium

BACKGROUND AND AIMS

The Cancer Genome Atlas (TCGA) project has identified HER2 mutations or amplification in 7% of colon cancers. In addition to HER2 mutations, colon cancer patients also possess co-occurring mutations in genes such as APC. Here, we investigated the role of HER2 and APC mutations on the crypt-villus architecture of the intestinal epithelium, localization of secretory cells, and expression of intestinal stem cell markers.

METHODS

We generated a HER2 transgenic mouse (HER2V777L Tg) possessing an activating mutation commonly found in colorectal cancer patients, HER2V777L, using transcription activator-like effector nucleases-based gene editing technology. We expressed the HER2V777L transgene in mouse small intestine and colon using Lgr5-Cre and Villin-Cre recombinases. In addition, we analyzed Lgr5-Cre; APCmin; HER2V777L Tg mice by morphologic and gene expression assays on intestinal sections and organoids derived from the epithelium.

RESULTS

HER2V777L expression resulted in hypertrophic crypt formation with expanded zones of proliferation. Proximal intestinal villi showed increased abundance of multiple differentiated lineages including extensive intermediate cell differentiation, as evidenced by MUC2/MMP7 co-immunofluorescence and transmission electron microscopy. HER2V777L expression in the context of APC loss resulted in further enhancement and expansion of the proliferative crypt compartment.

CONCLUSIONS

We established an epithelial intrinsic role for HER2V777L on enhanced cellular proliferation. Additionally, we determined that HER2 and APC mutations, when combined, promote enhanced proliferation of intestinal crypts.

Functional cooperation between co-amplified genes promotes aggressive phenotypes of HER2-positive breast cancer

MED1 (mediator subunit 1)co-amplifies with HER2, but its role in HER2-driven mammary tumorigenesis is still unknown. Here, we generate MED1 mammary-specific overexpression mice and cross them with mouse mammary tumor virus (MMTV)-HER2 mice. We observe significantly promoted onset, growth, metastasis, and multiplicity of HER2 tumors by MED1 overexpression. Further studies reveal critical roles for MED1 in epithelial-mesenchymal transition, cancer stem cell formation, and response to anti-HER2 therapy. Mechanistically, RNA sequencing (RNA-seq) transcriptome analyses and clinical sample correlation studies identify Jab1, a component of the COP9 signalosome complex, as the key direct target gene of MED1 contributing to these processes. Further studies reveal that Jab1 can also reciprocally regulate the stability and transcriptional activity of MED1. Together, our findings support a functional cooperation between these co-amplified genes in HER2⁺ mammary tumorigenesis and their potential usage as therapeutic targets for the treatment of HER2⁺ breast cancers.

In this study, Yang et al. generate a more clinically relevant MMTV-HER2/MMTV-MED1 mammary tumor mouse model and discover the critical roles and molecular mechanisms of MED1 overexpression in mediating the aggressive phenotypes of HER2⁺ tumor progression, metastasis, cancer stem cell formation, and therapy resistance.

Mutational drivers of cancer cell migration and invasion

Genomic instability and mutations underlie the hallmarks of cancer-genetic alterations determine cancer cell fate by affecting cell proliferation, apoptosis and immune response, and increasing data show that mutations are involved in metastasis, a crucial event in cancer progression and a life-threatening problem in cancer patients. Invasion is the first step in the metastatic cascade, when tumour cells acquire the ability to move, penetrate into the surrounding tissue and enter lymphatic and blood vessels in order to disseminate. A role for genetic alterations in invasion is not universally accepted, with sceptics arguing that cellular motility is related only to external factors such as hypoxia, chemoattractants and the rigidity of the extracellular matrix. However, increasing evidence shows that mutations might trigger and accelerate the migration and invasion of different types of cancer cells. In this review, we summarise data from published literature on the effect of chromosomal instability and genetic mutations on cancer cell migration and invasion.

Anticancer evaluation of N-benzoyl-3-allylthiourea as potential antibreast cancer agent through enhances HER-2 expression

Breast cancer with HER-2 overexpression is sensitive to drugs which target the receptor or its kinase activity. Although the anti-HER-2 therapies commonly used have improved patient outcome, resistance usually occurs. In this present study, we investigated a modification of the chemical structure of allylthiourea derivatives in order to enhance the cytotoxicity effect on breast cancer cells with HER-2 overexpression. The aim of this research was to predict the absorption, distribution, metabolism, excretion, and toxicity by in silico study and to explore the effect N-benzoyl-3-allylthiourea (BATU) on MCF-7 cell line with overexpressing of HER-2 using MTT assay and western blot. The result showed that the cytotoxicity effects of BATU on MCF-7/HER-2 cell line (IC₅₀ value 0.64 mM) were higher than on MCF-7 cell lines (IC₅₀ value 1.47 mM). In addition, the cytotoxic effects of BATU on MCF-7 and MCF-7/HER-2 were higher than allylthiourea as a lead compound (IC₅₀ value 5.22 and 3.17 mM). The results also confirmed that the BATU compound has the ability to effectively enhance its cytotoxicity against MCF-7/HER-2 through enhanced HER-2 expression and inhibition of nuclear factor kappa B (NF-kB) activation. Above all, the BATU compound is effective in increasing HER-2 expression and inactivating NF-kB transcription factors, thereby resulting in inhibition of protein expression which works a significant part in cell proliferation. Therefore, the BATU compound has the potential to be developed as a complementary drug in breast cancer therapy with HER-2 positive.

P120-Catenin And Its Phosphorylation On Tyr228 Inhibits Proliferation And Invasion In Colon Adenocarcinoma Cells

Background

Colorectal cancer is the third most common malignancy worldwide and is one of the leading causes of cancer-related mortality. P120-catenin protein has been well known to exert anticancer effects in several malignant diseases. The aim of our study was to investigate the phosphorylation of p120-catenin in colon adenocarcinoma (CAC) and its association with prognosis, and its role in tumor progression.

Methods

Immunohistochemical (IHC) staining was used to explore the existence of p120-catenin and its phosphorylation on tyrosine 228 (pY228-p120-catenin) in CAC samples. Overexpression and knockdown were achieved by transient transfection into SW480 cells using Lipofectamine 3000. CCK-8 and Matrigel-transwell assays were conducted to evaluate proliferation and invasion capacities, respectively. RT-qPCR and Western blotting were performed to analyze downstream signaling pathways. Chi-square test was used to analyze correlations between p120-catenin and clinicopathological characteristics. Univariate and multivariate analyses were used to identify independent prognostic factors.

Results

Lower p120-catenin and pY228-p120-catenin levels were identified in CAC tissues and were both correlated with advanced tumor stage. Additionally, lower pY228-p120-catenin indicated poorer prognosis of CAC patients although p120-catenin showed little significance. Overexpression of p120-catenin suppressed SW480 cell proliferation and invasion via stabilizing E-cadherin and inhibiting RhoA activation. Phosphorylation of Y228 on p120-catenin by Src protein enhanced the anticancer effects of p120-catenin.

Conclusion

P120-catenin and its phosphorylation on site Y228 play anticancer effects in colon adenocarcinoma via multiple signaling pathways. Hypophosphorylation of Y228 on p120-catenin in tumor tissues indicates poor clinical outcomes of colon adenocarcinoma patients.

Role of miR-337-3p and its target Rap1A in modulating proliferation, invasion, migration and apoptosis of cervical cancer cells

OBJECTIVE

To investigate the role of miR-337-3p targeting Rap1A in modulating proliferation, invasion, migration and apoptosis of cervical cancer cells.

METHODS

The expression levels of miR-337-3p and Rap1A in cervical cancer tissues and normal tissues were evaluated through quantitative Real-time PCR (qRT-PCR) and Western blotting; and correlations of miR-337-3p with clinicopathological characteristics and prognosis of patients were also analyzed. Besides, human cervical cancer cell line HeLa cells were randomly divided into five groups (Mock, NC, miR-337-3p mimic, Rap1A, and miR-337-3p mimic + Rap1A groups). CCK-8 assay was utilized to measure cell proliferation, flow cytometry to evaluate cell apoptosis, and wound-healing and Transwell assays to detect cell migration and invasion.

RESULTS

Cervical cancer tissues presented a significant decrease in miR-337-3p and a remarkable increase in Rap1A protein. Besides, the expression levels of miR-337-3p and Rap1A were closely related to the major clinicopathological characteristics of cervical cancer; and patients with high-miR-337-3p-expression had the higher 5-year survival rate (all p< 0.05). When compared to Mock group, cells in miR-337-3p mimic group were suppressed in proliferation, migration, and invasion, but significantly promoted in apoptosis; meanwhile, cells in the Rap1A group showed changes in a completely opposite trend (all p< 0.05). Moreover, Rap1A can reverse the effect of miR-337-3p mimic on cell proliferation, invasion, migration and apoptosis (all p< 0.05).

CONCLUSION

MiR-337-3p was discovered to be decreased in cervical cancer, and miR-337-3p up-regulation may inhibit the proliferation, migration and invasion and promote the apoptosis of cervical cancer cells via down-regulating Rap1A.

Focus on Cdc42 in Breast Cancer: New Insights, Target Therapy Development and Non-Coding RNAs

Breast cancer is the most common malignant tumors in females. Although the conventional treatment has demonstrated a certain effect, some limitations still exist. The Rho guanosine triphosphatase (GTPase) Cdc42 (Cell division control protein 42 homolog) is often upregulated by some cell surface receptors and oncogenes in breast cancer. Cdc42 switches from inactive guanosine diphosphate (GDP)-bound to active GTP-bound though guanine-nucleotide-exchange factors (GEFs), results in activation of signaling cascades that regulate various cellular processes such as cytoskeletal changes, proliferation and polarity establishment. Targeting Cdc42 also provides a strategy for precise breast cancer therapy. In addition, Cdc42 is a potential target for several types of non-coding RNAs including microRNAs and lncRNAs. These non-coding RNAs is extensively involved in Cdc42-induced tumor processes, while many of them are aberrantly expressed. Here, we focus on the role of Cdc42 in cell morphogenesis, proliferation, motility, angiogenesis and survival, introduce the Cdc42-targeted non-coding RNAs, as well as present current development of effective Cdc42-targeted inhibitors in breast cancer.

Cullin-3/KCTD10 E3 complex is essential for Rac1 activation through RhoB degradation in human epidermal growth factor receptor 2-positive breast cancer cells

Rho GTPase Rac1 is a central regulator of F‐actin organization and signal transduction to control plasma membrane dynamics and cell proliferation. Dysregulated Rac1 activity is often observed in various cancers including breast cancer and is suggested to be critical for malignancy. Here, we showed that the ubiquitin E3 ligase complex Cullin‐3 (CUL3)/KCTD10 is essential for epidermal growth factor (EGF)‐induced/human epidermal growth factor receptor 2 (HER2)‐dependent Rac1 activation in HER2‐positive breast cancer cells. EGF‐induced dorsal membrane ruffle formation and cell proliferation that depends on both Rac1 and HER2 were suppressed in CUL3‐ or KCTD10‐depleted cells. Mechanistically, CUL3/KCTD10 ubiquitinated RhoB for degradation, another Rho GTPase that inhibits Rac1 activation at the plasma membrane by suppressing endosome‐to‐plasma membrane traffic of Rac1. In HER2‐positive breast cancers, high expression of Rac1 mRNA significantly correlated with poor prognosis of the patients. This study shows that this novel molecular axis (CUL3/KCTD10/RhoB) positively regulates the activity of Rac1 in HER2‐positive breast cancers, and our findings may lead to new treatment options for HER2‐ and Rac1‐positive breast cancers.

P120 catenin expression and its correlation with E-cadherin in salivary gland neoplasms

Objectives

Altered P120 catenin expression has been associated with E-cadherin loss and poor prognosis in several cancers. The objectives of this study were to examine the P120 catenin expression in salivary gland neoplasms in correlation with E-cadherin and assess the relationships between their expression levels and pathologic characteristics.

Methods

Fifty-two cases of salivary gland neoplasms, i.e. 25 mucoepidermoid carcinomas (MEC), 13 adenoid cystic carcinomas (ACC), 12 pleomorphic adenomas (PA) and 2 polymorphous adenocarcinomas (PAC) were included. The expression of P120 catenin and E-cadherin was investigated immunohistochemically.

Results

Both P120 catenin and E-cadherin were overexpressed in salivary gland neoplasms, compared to normal tissue. P120 catenin was primarily detected on the membrane of neoplastic cells in most cases. A significant correlation between levels of expression of both proteins was noted in MECs. In ACCs and PA, ductal cells showed positive immunoreactivity, whereas myoepithelial cells variably expressed both proteins. Increased P120 catenin expression was significantly associated with the solid subtype of ACCs.

Conclusions

The cadherin-catenin complex is preserved in the heterogenous tumor cell population in salivary gland neoplasms. Overexpression of P120 catenin may be involved in the progression to solid ACCs.

The Cytotoxic and Antimigratory Activity of Brazilin-Doxorubicin on MCF-7/HER2 Cells

Purpose: Breast cancer cells with overexpression of HER2 are known to be more aggressive, invasive, and resistant to chemotherapeutic agent. Brazilin, the major compound in the Caesalpinia sappan L. (CS) heartwood, has been studied for it's anticancer activity. The purpose of this study was to investigate the cytotoxic and antimigratory activity of brazilin (Bi) in combination with doxorubicin (Dox) on MCF-7/HER2 cells.

Methods: Cytotoxic activities of Bi individually and in combination with Dox were examined by MTT assay. Synergistic effects were analyzed by combination index (CI). Apoptosis and cell cycle profiles were observed by using flow cytometry. Migrating and invading cells were observed by using a Boyden chamber assay. Levels of MMP2 and MMP9 activity were observed by using a gelatin zymography assay. Levels of HER2, Bcl-2, Rac1, and p120 protein expression were observed by using an immunoblotting assay.

Results: The results of the MTT assay showed that Bi inhibited MCF-7/HER2 cell growth in a dose-dependent manner with an IC50 of 54 ± 3.7 µM. Furthermore, the combination of Bi and Dox showed a synergistic effect (CI <1). Flow cytometric analysis of Bi and its combination with Dox showed cellular accumulation in the G2/M phase and induction of apoptosis through suppression of Bcl-2 protein expression. In the Boyden chamber assay, gelatin zymography, and subsequent immunoblotting assay, the combination Bi and Dox inhibited migration, possibly through downregulation of MMP9, MMP2, HER2, Rac1, and p120 protein expression.

Conclusion: We conclude that Bi enhanced cytotoxic activity of Dox and inhibited migration of MCF-7/HER2 cells. Therefore, we believe that it has strong potential to be developed for the treatment of metastatic breast cancer with HER2 overexpression.

p120-catenin is required for regulating epidermal proliferation, differentiation, and barrier function

p120-catenin (p120) is an important regulator in the function and stability of E-cadherin. However, the role of p120 in the epidermis is unclear. Previous studies have shown that globally knockout of p120 caused increased epidermal proliferation but little changes in epidermal differentiation and permeability. In the present study, we generated a conditional knockout mouse model and examined epidermal proliferation, differentiation and permeability. The results showed that conditional knockout of p120 in the epidermis caused not only increased epidermal proliferation but also decreased epidermal differentiation and increased permeability. These data suggest that p120 is required for suppressing epidermal proliferation, promoting epidermal differentiation and maintaining permeability barrier function of the epidermis.

ARHGAP15 in Human Breast Carcinoma: A Potent Tumor Suppressor Regulated by Androgens

Rho GTPase activating protein 15 (ARHGAP15) is a recently identified GTPase activating protein which enhances intrinsic hydrolysis of GTP-bound Ras-related C3 botulinus toxin substrate (Rac1), resulting in inactivation of Rac1. Although a lot of studies have pointed out the pivotal roles of the Rac1 pathway in the progression of breast carcinomas, the clinical significance of ARHGAP15 has remained largely unknown in human breast carcinomas. Therefore, we immunolocalized ARHGAP15 in one hundred breast carcinoma tissues. ARHGAP15 immunoreactivity was frequently detected in the cytoplasm of carcinoma cells, and was positively correlated with that of Rac1 and androgen receptor labeling index. Furthermore, ARHGAP15 immunoreactivity was significantly correlated with decreased risk of recurrence and improved prognosis, and multivariate analyses demonstrated that ARHGAP15 immunoreactivity was an independent prognostic factor for both disease-free and breast-cancer-specific survival of the patients. In addition, exogenous overexpression of ARHGA15 suppressed cell proliferation and migration of MCF-7 cells and SK-BR-3 cells. On the other hand, ARHGAP15 mRNA was significantly induced by dihydrotestosterone. These findings suggest that ARHGAP15 is an androgen-induced gene and has anti-tumorigenic roles associated with the Rac1 pathway. ARHGAP15 immunoreactivity is therefore considered a potent prognostic factor in human breast carcinomas.

The significance of tumour microarchitectural features in breast cancer prognosis: a digital image analysis

Background

As only a minor portion of the information present in histological sections is accessible by eye, recognition and quantification of complex patterns and relationships among constituents relies on digital image analysis. In this study, our working hypothesis was that, with the application of digital image analysis technology, visually unquantifiable breast cancer microarchitectural features can be rigorously assessed and tested as prognostic parameters for invasive breast carcinoma of no special type.

Methods

Digital image analysis was performed using public domain software (ImageJ) on tissue microarrays from a cohort of 696 patients, and validated with a commercial platform (Visiopharm). Quantified features included elements defining tumour microarchitecture, with emphasis on the extent of tumour-stroma interface. The differential prognostic impact of tumour nest microarchitecture in the four immunohistochemical surrogates for molecular classification was analysed. Prognostic parameters included axillary lymph node status, breast cancer-specific survival, and time to distant metastasis. Associations of each feature with prognostic parameters were assessed using logistic regression and Cox proportional models adjusting for age at diagnosis, grade, and tumour size.

Results

An arrangement in numerous small nests was associated with axillary lymph node involvement. The association was stronger in luminal tumours (odds ratio (OR) = 1.39, p = 0.003 for a 1-SD increase in nest number, OR = 0.75, p = 0.006 for mean nest area). Nest number was also associated with survival (hazard ratio (HR) = 1.15, p = 0.027), but total nest perimeter was the parameter most significantly associated with survival in luminal tumours (HR = 1.26, p = 0.005). In the relatively small cohort of triple-negative tumours, mean circularity showed association with time to distant metastasis (HR = 1.71, p = 0.027) and survival (HR = 1.8, p = 0.02).

Conclusions

We propose that tumour arrangement in few large nests indicates a decreased metastatic potential. By contrast, organisation in numerous small nests provides the tumour with increased metastatic potential to regional lymph nodes. An outstretched pattern in small nests bestows tumours with a tendency for decreased breast cancer-specific survival. Although further validation studies are required before the argument for routine quantification of microarchitectural features is established, our approach is consistent with the demand for cost-effective methods for triaging breast cancer patients that are more likely to benefit from chemotherapy.

A new role of the Rac-GAP β2-chimaerin in cell adhesion reveals opposite functions in breast cancer initiation and tumor progression

β2-chimaerin is a Rac1-specific negative regulator and a candidate tumor suppressor in breast cancer but its precise function in mammary tumorigenesis in vivo is unknown. Here, we study for the first time the role of β2-chimaerin in breast cancer using a mouse model and describe an unforeseen role for this protein in epithelial cell-cell adhesion. We demonstrate that expression of β2-chimaerin in breast cancer epithelial cells reduces E-cadherin protein levels, thus loosening cell-cell contacts. In vivo, genetic ablation of β2-chimaerin in the MMTV-Neu/ErbB2 mice accelerates tumor onset, but delays tumor progression. Finally, analysis of clinical databases revealed an inverse correlation between β2-chimaerin and E-cadherin gene expressions in Her2+ breast tumors. Furthermore, breast cancer patients with low β2-chimaerin expression have reduced relapse free survival but develop metastasis at similar times. Overall, our data redefine the role of β2-chimaerin as tumor suppressor and provide the first in vivo evidence of a dual function in breast cancer, suppressing tumor initiation but favoring tumor progression.

miR-1296-5p decreases ERBB2 expression to inhibit the cell proliferation in ERBB2-positive breast cancer

BACKGROUND

The tumor suppressive role of miR-1296 is observed in triple negative breast cancer (TNBC). However, the effect of miR-1296-5p in ERBB2-positive breast cancers remains obscure.

METHODS

Whether ERBB2 was the target gene of the miR-1296-5p was predicted by online software, and determined by dual-luciferase activity assay. miR-1296-5p expression levels were determined in breast cancer samples (114 breast cancer tissues and 30 adjacent normal tissues) by using qRT-PCR. The effect of miR-1296-5p and inhibition of ERBB2/mTORC1 signaling on the downstream target was assessed by Western blot. SK-BR-3 and BT-474 breast cancer cell line was transfected with miR-1296-5p mimic after which cell proliferation and apoptosis were determined by the clonogenic assay and the flow cytometry system, respectively. In addition, the chemotherapeutic drug sensitivity of SK-BR-3 and BT-474 cells transfected with miR-1296-5p mimic were determined by MTT assay.

RESULTS

The luciferase assay carrying ERBB2 3'-untranslated region-based reporters expressed in SK-BR-3 and BT-474 cells suggested that ERBB2 was the target gene of miR-1296-5p. MiR-1296-5p was significantly decreased in breast cancer tissues compared to adjacent normal tissues. Moreover, it was declined in ERBB2-positive breast cancer samples compared with that in ERBB2-negative breast cancer tissues. Overexpressed miR-1296-5p reduced its target protein level and mTORC1/S6 activation, inhibited the proliferation of ERBB2-positive breast cancer cells and sensitized these cells to cisplatin and 5-fluorouracil-induced apoptosis.

CONCLUSIONS

Our findings suggest that miR-1296-5p is involved in the regulation of proliferation in breast cancer cells via targeting ERBB2/mTORC1 signaling pathway.

Tumor suppressor role of miR-3622b-5p in ERBB2-positive cancer

Over-expression or amplification of ERBB2 is observed in multifarious carcinomas. However, the molecular mechanism of ERBB2 downregulation in ERBB2-positive cancers remains obscure. This experiment investigated the suppressive role of miR-3622b-5p in ERBB2-positive breast and gastric cancers. The luciferase activity of ERBB2 3′-untranslated region-based reporters constructed in HEK-293T, SK-BR-3 and MCF-10A cells suggested that ERBB2 was the target gene of miR-3622b-5p. Over-expressed miR-3622b-5p reduced the protein level of ERBB2, weakened the activation of mTORC1/S6, and induced the apoptosis of ERBB2-positive cancer cells. MiR-3622b-5p was significantly down-regulated in breast and gastric cancer tissues. This down-regulation in ERBB2-positive breast and gastric cancer tissues was more obvious than that in ERBB2-negative breast and gastric cancer tissues. MiR-3622b-5p turned ERBB2-positive cancer cells more vulnerable to the apoptosis induced by cisplatin and 5-fluorouracil. Taken together, miR-3622b-5p is involved in the proliferation and apoptosis of human ERBB2-positive cancer cells via targeting ERBB2/mTORC1 signaling pathway.

RORα2 requires LSD1 to enhance tumor progression in breast cancer

Retinoic acid-related orphan receptor α (RORα) regulates diverse physiological processes, including inflammatory responses, lipid metabolism, circadian rhythm, and cancer biology. RORα has four different isoforms which have distinct N-terminal domains but share identical DNA binding domain and ligand binding domain in human. However, lack of specific antibody against each RORα isoform makes biochemical studies on each RORα isoform remain unclear. Here, we generate RORα2-specific antibody and characterize the role of RORα2 in promoting tumor progression in breast cancer. RORα2 requires lysine specific demethylase 1 (LSD1/KDM1A) as a coactivator for transcriptional activation of RORα2 target genes, exemplified by CTNND1. Intriguingly, RORα2 and LSD1 protein levels are dramatically elevated in human breast cancer specimens compared to normal counterparts. Taken together, our studies indicate that LSD1-mediated RORα2 transcriptional activity is important to promote tumor cell migration in human breast cancer as well as breast cancer cell lines. Therefore, our data establish that suppression of LSD1-mediated RORα2 transcriptional activity may be potent therapeutic strategy to attenuate tumor cell migration in human breast cancer.

Paving the Rho in cancer metastasis: Rho GTPases and beyond

Malignant carcinomas are often characterized by metastasis, the movement of carcinoma cells from a primary site to colonize distant organs. For metastasis to occur, carcinoma cells first must adopt a pro-migratory phenotype and move through the surrounding stroma towards a blood or lymphatic vessel. Currently, there are very limited possibilities to target these processes therapeutically. The family of Rho GTPases is an ubiquitously expressed division of GTP-binding proteins involved in the regulation of cytoskeletal dynamics and intracellular signaling. The best characterized members of the Rho family GTPases are RhoA, Rac1 and Cdc42. Abnormalities in Rho GTPase function have major consequences for cancer progression. Rho GTPase activation is driven by cell surface receptors that activate GTP exchange factors (GEFs) and GTPase-activating proteins (GAPs). In this review, we summarize our current knowledge on Rho GTPase function in the regulation of metastasis. We will focus on key discoveries in the regulation of epithelial-mesenchymal-transition (EMT), cell-cell junctions, formation of membrane protrusions, plasticity of cell migration and adaptation to a hypoxic environment. In addition, we will emphasize on crosstalk between Rho GTPase family members and other important oncogenic pathways, such as cyclic AMP-mediated signaling, canonical Wnt/β-catenin, Yes-associated protein (YAP) and hypoxia inducible factor 1α (Hif1α) and provide an overview of the advancements and challenges in developing pharmacological tools to target Rho GTPase and the aforementioned crosstalk in the context of cancer therapeutics.

A central role for cadherin signaling in cancer

Cadherins are homophilic adhesion molecules with important functions in cell-cell adhesion, tissue morphogenesis, and cancer. In epithelial cells, E-cadherin accumulates at areas of cell-cell contact, coalesces into macromolecular complexes to form the adherens junctions (AJs), and associates via accessory partners with a subcortical ring of actin to form the apical zonula adherens (ZA). As a master regulator of the epithelial phenotype, E-cadherin is essential for the overall maintenance and homeostasis of polarized epithelial monolayers. Its expression is regulated by a host of genetic and epigenetic mechanisms related to cancer, and its function is modulated by mechanical forces at the junctions, by direct binding and phosphorylation of accessory proteins collectively termed catenins, by endocytosis, recycling and degradation, as well as, by multiple signaling pathways and developmental processes, like the epithelial to mesenchymal transition (EMT). Nuclear signaling mediated by the cadherin associated proteins β-catenin and p120 promotes growth, migration and pluripotency. Receptor tyrosine kinase, PI3K/AKT, Rho GTPase, and HIPPO signaling, are all regulated by E-cadherin mediated cell-cell adhesion. Finally, the recruitment of the microprocessor complex to the ZA by PLEKHA7, and the subsequent regulation of a small subset of miRNAs provide an additional mechanism by which the state of epithelial cell-cell adhesion affects translation of target genes to maintain the homeostasis of polarized epithelial monolayers. Collectively, the data indicate that loss of E-cadherin function, especially at the ZA, is a common and crucial step in cancer progression.

Two distinct mTORC2-dependent pathways converge on Rac1 to drive breast cancer metastasis

Background

The importance of the mTOR complex 2 (mTORC2) signaling complex in tumor progression is becoming increasingly recognized. HER2-amplified breast cancers use Rictor/mTORC2 signaling to drive tumor formation, tumor cell survival and resistance to human epidermal growth factor receptor 2 (HER2)-targeted therapy. Cell motility, a key step in the metastatic process, can be activated by mTORC2 in luminal and triple negative breast cancer cell lines, but its role in promoting metastases from HER2-amplified breast cancers is not yet clear.

Methods

Because Rictor is an obligate cofactor of mTORC2, we genetically engineered Rictor ablation or overexpression in mouse and human HER2-amplified breast cancer models for modulation of mTORC2 activity. Signaling through mTORC2-dependent pathways was also manipulated using pharmacological inhibitors of mTOR, Akt, and Rac. Signaling was assessed by western analysis and biochemical pull-down assays specific for Rac-GTP and for active Rac guanine nucleotide exchange factors (GEFs). Metastases were assessed from spontaneous tumors and from intravenously delivered tumor cells. Motility and invasion of cells was assessed using Matrigel-coated transwell assays.

Results

We found that Rictor ablation potently impaired, while Rictor overexpression increased, metastasis in spontaneous and intravenously seeded models of HER2-overexpressing breast cancers. Additionally, migration and invasion of HER2-amplified human breast cancer cells was diminished in the absence of Rictor, or upon pharmacological mTOR kinase inhibition. Active Rac1 was required for Rictor-dependent invasion and motility, which rescued invasion/motility in Rictor depleted cells. Rictor/mTORC2-dependent dampening of the endogenous Rac1 inhibitor RhoGDI2, a factor that correlated directly with increased overall survival in HER2-amplified breast cancer patients, promoted Rac1 activity and tumor cell invasion/migration. The mTORC2 substrate Akt did not affect RhoGDI2 dampening, but partially increased Rac1 activity through the Rac-GEF Tiam1, thus partially rescuing cell invasion/motility. The mTORC2 effector protein kinase C (PKC)α did rescue Rictor-mediated RhoGDI2 downregulation, partially rescuing Rac-guanosine triphosphate (GTP) and migration/motility.

Conclusion

These findings suggest that mTORC2 uses two coordinated pathways to activate cell invasion/motility, both of which converge on Rac1. Akt signaling activates Rac1 through the Rac-GEF Tiam1, while PKC signaling dampens expression of the endogenous Rac1 inhibitor, RhoGDI2.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-017-0868-8) contains supplementary material, which is available to authorized users.

Ensemble clustering of phosphoproteomic data identifies differences in protein interactions and cell-cell junction integrity of HER2-overexpressing cells

Overexpression of HER2, a receptor tyrosine kinase of the ERBB family, in breast cancer is related to increased cancer progression and aggressiveness. A breast epithelial cell model with the single perturbation of HER2 overexpression is capable of replicating the increased aggressiveness of HER2 overexpressing cancers. In previous work, Wolf-Yadlin and colleagues (Wolf-Yadlin et al., Mol. Syst. Biol., 2006, 2) measured the proximal tyrosine phosphorylation dynamics of the parental and HER2 overexpressing cells (24H) in response to EGF. Here, we apply an ensemble clustering approach to dynamic phosphorylation measurements of the two cell models in order to identify signaling events that explain the increased migratory potential of HER2 overexpressing cells. The use of an ensemble approach for identifying relationships within a dataset and how these relationships change across datasets uncovers relationships that cannot be found by the direct comparison of dynamic responses in the two conditions. Of particular note is a drastic change in the clustering of SHC1 phosphorylation (on site Y349) from an EGFR-MAPK module in parental cells to a module consisting of an E-cadherin junction protein phosphorylation site, catenin delta-1 Y228, in HER2 overexpressing (24H) cells. Given the importance of E-cadherin junctions in healthy epithelial wound healing and migration, we chose to test the computationally-derived identification of altered cell junctions and CTNND1:SHC1 relationships. Our cell and molecular biology experiments demonstrate that SHC and CTNND1 interact in an EGF- and HER2-dependent manner and that the cell junctions are phenotypically affected by HER2, breaking down in response to EGF and yet avoiding apoptosis as a result of cell junction loss. The results suggest a mechanism by which HER2 alters the localization of the SHC-MAPK signaling axis and a phenotypic effect on cell junction integrity.

Follistatin is a metastasis suppressor in a mouse model of HER2-positive breast cancer

Background

Follistatin (FST) is an intrinsic inhibitor of activin, a member of the transforming growth factor-β superfamily of ligands. The prognostic value of FST and its family members, the follistatin-like (FSTL) proteins, have been studied in various cancers. However, these studies, as well as limited functional analyses of the FSTL proteins, have yielded conflicting results on the role of these proteins in disease progression. Furthermore, very few have been focused on FST itself. We assessed whether FST may be a suppressor of tumorigenesis and/or metastatic progression in breast cancer.

Methods

Using publicly available gene expression data, we examined the expression patterns of FST and INHBA, a subunit of activin, in normal and cancerous breast tissue and the prognostic value of FST in breast cancer metastases, recurrence-free survival, and overall survival. The functional effects of activin and FST on in vitro proliferation, migration, and invasion of breast cancer cells were also examined. FST overexpression in an autochthonous mouse model of breast cancer was then used to assess the in vivo impact of FST on metastatic progression.

Results

Examination of multiple breast cancer datasets revealed that FST expression is reduced in breast cancers compared with normal tissue and that low FST expression predicts increased metastasis and reduced overall survival. FST expression was also reduced in a mouse model of HER2/Neu-induced metastatic breast cancer. We found that FST blocks activin-induced breast epithelial cell migration in vitro, suggesting that its loss may promote breast cancer aggressiveness. To directly determine if FST restoration could inhibit metastatic progression, we transgenically expressed FST in the HER2/Neu model. Although FST had no impact on tumor initiation or growth, it completely blocked the formation of lung metastases.

Conclusions

These data indicate that FST is a bona fide metastasis suppressor in this mouse model and support future efforts to develop an FST mimetic to suppress metastatic progression.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-017-0857-y) contains supplementary material, which is available to authorized users.

miR 1296-5p Inhibits the Migration and Invasion of Gastric Cancer Cells by Repressing ERBB2 Expression

The metastasis of gastric cancer, one of the most common tumors, has a molecular mechanism that is still largely unclear. Here we investigated the role of possible tumor-suppressor miR-1296-5p in the cell migration and invasion of ERBB2-positive gastric cancer. It found that miR-1296-5p was significantly down-regulated in gastric cancer tissues. Moreover, it was down-regulated in lymph node metastatic gastric cancer tissues compared with non-metastatic gastric cancer tissues. The luciferase activity of ERBB2 3'-untranslated region-based reporters constructed in SNU-216 and NUGC-4 gastric cancer cells suggested that ERBB2 was the target gene of miR-1296-5p. Overexpressed miR-1296-5p reduced its target protein level and Rac1 activation, and inhibited the migration and invasion of SNU-216 and NUGC-4 gastric cancer cells. MiR-1296-5p was down-regulated in ERBB2-positive gastric cancer tissues compared with ERBB2-negative gastric cancer tissues. In ERBB2-positive gastric cancers, the miR-1296-5p expression was suppressed in a majority of metastatic lymph node tissues compared to non-metastatic gastric cancer samples. The migration and invasion of gastric cancer cells was inhibited by miR-1296-5p overexpression or herceptin treatment, and rescued by the overexpression of constitutively active Rac1-Q61L or ERBB2. Taken together, our findings first suggest that miR-1296-5p might be involved in the regulation on the migration and invasion of human gastric cancer cells at least in part via targeting ERBB2/Rac1 signaling pathway.

High cell-surface density of HER2 deforms cell membranes

Breast cancers (BC) with HER2 overexpression (referred to as HER2 positive) progress more aggressively than those with normal expression. Targeted therapies against HER2 can successfully delay the progression of HER2-positive BC, but details of how this overexpression drives the disease are not fully understood. Using single-molecule biophysical approaches, we discovered a new effect of HER2 overexpression on disease-relevant cell biological changes in these BC. We found HER2 overexpression causes deformation of the cell membranes, and this in turn disrupts epithelial features by perturbing cell-substrate and cell-cell contacts. This membrane deformation does not require receptor signalling activities, but results from the high levels of HER2 on the cell surface. Our finding suggests that early-stage morphological alterations of HER2-positive BC cells during cancer progression can occur in a physical and signalling-independent manner.

Regulation and functional significance of CDC42 alternative splicing in ovarian cancer

Our previous study found that splicing factor polypyrimidine tract-binding protein 1 (PTBP1) had a role in tumorigenesis but the underlying mechanism remained unclear. In this study, we observed that knockdown of PTBP1 inhibited filopodia formation. Subsequently, we found that PTBP1 regulated the alternative splicing of CDC42, a major regulator of filopodia formation. Two CDC42 variants, CDC42-v1 and CDC42-v2, can be generated through alternative splicing. Knockdown of PTBP1 increased the expression of CDC42-v2. Ectopic expression of individual variants showed that CDC42-v2 suppressed filopodia formation, opposite to the effect of CDC42-v1. Quantitative RT-PCR revealed that CDC42-v2 was expressed at lower levels in ovarian cancer cell lines and ovarian tumor tissues than in normal control cells and tissues. Further, CDC42-v2 was observed to have inhibitory effects on ovarian tumor cell growth, colony formation in soft agar and invasiveness. In contrast, these inhibitory effects were not found with CDC42-v1. Taken together, above results suggest that the role of PTBP1 in tumorigenesis may be partly mediated by its regulation of CDC42 alternative splicing and CDC42-v2 might function as a tumor suppressor.

TOM1L1 drives membrane delivery of MT1-MMP to promote ERBB2-induced breast cancer cell invasion

ERBB2 overexpression in human breast cancer leads to invasive carcinoma but the mechanism is not clearly understood. Here we report that TOM1L1 is co-amplified with ERBB2 and defines a subgroup of HER2⁺/ER⁺ tumours with early metastatic relapse. TOM1L1 encodes a GAT domain-containing trafficking protein and is a SRC substrate that negatively regulates tyrosine kinase signalling. We demonstrate that TOM1L1 upregulation enhances the invasiveness of ERBB2-transformed cells. This pro-tumoural function does not involve SRC, but implicates membrane-bound membrane-type 1 MMP (MT1-MMP)-dependent activation of invadopodia, membrane protrusions specialized in extracellular matrix degradation. Mechanistically, ERBB2 elicits the indirect phosphorylation of TOM1L1 on Ser321. The phosphorylation event promotes GAT-dependent association of TOM1L1 with the sorting protein TOLLIP and trafficking of the metalloprotease MT1-MMP from endocytic compartments to invadopodia for tumour cell invasion. Collectively, these results show that TOM1L1 is an important element of an ERBB2-driven proteolytic invasive programme and that TOM1L1 amplification potentially enhances the metastatic progression of ERBB2-positive breast cancers.

ERBB2 overexpression in human breast cancer leads to invasion and metastasis. Here the authors report that ERBB2 induces indirect phosphorylation of TOM1L1 that promotes trafficking of the metalloprotease MT1-MMP to invadopodia, which leads to tumour cell invasion.

FASN, ErbB2-mediated glycolysis is required for breast cancer cell migration

Both fatty acid synthase (FASN) and ErbB2 have been shown to promote breast cancer cell migration. However, the underlying molecular mechanism remains poorly understood and there is no reported evidence that directly links glycolysis to breast cancer cell migration. In this study, we investigated the role of FASN, ErbB2-mediated glycolysis in breast cancer cell migration. First, we compared lactate dehydrogenase A (LDHA) protein levels, glycolysis and cell migration between FASN, ErbB2-overexpressing SK-BR-3 cells and FASN, ErbB2-low-expressing MCF7 cells. Then, SK-BR-3 cells were treated with cerulenin (Cer), an inhibitor of FASN, and ErbB2, LDHA protein levels, glycolysis, and cell migration were detected. Next, we transiently transfected ErbB2 plasmid into MCF7 cells and detected FASN, LDHA protein levels, glycolysis and cell migration. Heregulin-β1 (HRG-β1) is an activator of ErbB2 and 2-deoxyglucose (2-DG) and oxamate (OX) are inhibitors of glycolysis. MCF7 cells were treated with HRG-β1 alone, HRG-β1 plus 2-DG, OX or cerulenin and glycolysis, and cell migration were measured. We found that FASN, ErbB2-high-expressing SK-BR-3 cells displayed higher levels of glycolysis and migration than FASN, ErbB2-low-expressing MCF7 cells. Inhibition of FASN by cerulenin impaired glycolysis and migration in SK-BR-3 cells. Transient overexpression of ErbB2 in MCF7 cells promotes glycolysis and migration. Moreover, 2-deoxyglucose (2-DG), oxamate (OX), or cerulenin partially reverses heregulin-β1 (HRG-β1)-induced glycolysis and migration in MCF7 cells. In conclusion, this study demonstrates that FASN, ErbB2-mediated glycolysis is required for breast cancer cell migration. These novel findings indicate that targeting FASN, ErbB2-mediated glycolysis may be a new approach to reverse breast cancer cell migration.

WASF3 provides the conduit to facilitate invasion and metastasis in breast cancer cells through HER2/HER3 signaling

The WASF3 gene is overexpressed in high-grade breast cancer and promotes invasion and metastasis but does not affect proliferation. The HER2/ERBB2/NEU gene is also frequently overexpressed in breast cancer and has been shown to promote invasion and metastasis in these tumors. Here we show that WASF3 in present in the HER2 immunocomplex and suppression of WASF3 function leads to suppression of invasion even in the presence of HER2 expression. Overexpression of both HER2 and WASF3 in non-metastatic MCF7 breast cancer cells promotes invasion and metastasis more significantly than either gene alone. HER2 forms homodimers as well as heterodimers with other HER family members and we now show that the ability of WASF3 to promote invasion is highly dependent on the HER2/HER3 heterodimer. The engagement of WASF3 with the HER2/HER3 complex facilitates its phospho-activation and transcriptional upregulation, which is facilitated by HER2/HER3 activation of JAK/STAT signaling. In breast cancer cells overexpressing HER2, therefore, WASF3 is specifically required to facilitate the invasion/metastasis response. Targeting WASF3, therefore, could be a potential therapeutic approach to suppress metastasis of HER2-overexpressing breast tumors.

Divergent behaviors and underlying mechanisms of cell migration and invasion in non-metastatic T24 and its metastatic derivative T24T bladder cancer cell lines

Previous studies on cancer cell invasion were primarily focused on its migration because these two events were often considered biologically equivalent. Here we found that T24T cells exhibited higher invasion but lower migration abilities than T24 cells. Expression of Rho-GDPases was much lower and expression of SOD2 was much higher in T24T cells than those in T24 cells. Indeed, knockdown of SOD2 in T24T cells can reverse the cell migration but without affecting cell invasion. We also found that SOD2 inhibited the JNK/c-Jun cascade, and the inhibition of c-Jun activation by ectopic expression of TAM67 impaired Rho-GDPases expression and cell migration in T24T shSOD2 cells. Further, we found that Sp1 can upregulate SOD2 transcription in T24T cells. Importantly, matrix metalloproteinase-2 (MMP-2) was overexpressed in T24T and participated in increasing its invasion, and MMP-2 overexpression was mediated by increasing nuclear transport of nucleolin, which enhanced mmp-2 mRNA stability. Taken together, our study unravels an inverse relationship between cell migration and invasion in human bladder cancer T24T cells and suggests a novel mechanism underlying the divergent roles of SOD2 and MMP-2 in regulating metastatic behaviors of human bladder T24T in cell migration and invasion.

Distinct E-cadherin-based complexes regulate cell behaviour through miRNA processing or Src and p120 catenin activity

E-cadherin and p120 catenin (p120) are essential for epithelial homeostasis, but can also exert pro-tumorigenic activities. Here, we resolve this apparent paradox by identifying two spatially and functionally distinct junctional complexes in non-transformed polarized epithelial cells: one growth suppressing at the apical zonula adherens (ZA), defined by the p120 partner PLEKHA7 and a non-nuclear subset of the core microprocessor components DROSHA and DGCR8, and one growth promoting at basolateral areas of cell-cell contact containing tyrosine-phosphorylated p120 and active Src. Recruitment of DROSHA and DGCR8 to the ZA is PLEKHA7 dependent. The PLEKHA7-microprocessor complex co-precipitates with primary microRNAs (pri-miRNAs) and possesses pri-miRNA processing activity. PLEKHA7 regulates the levels of select miRNAs, in particular processing of miR-30b, to suppress expression of cell transforming markers promoted by the basolateral complex, including SNAI1, MYC and CCND1. Our work identifies a mechanism through which adhesion complexes regulate cellular behaviour and reveals their surprising association with the microprocessor.

Pro-Tumorigenic Phosphorylation of p120 Catenin in Renal and Breast Cancer

Altered protein expression and phosphorylation are common events during malignant transformation. These perturbations have been widely explored in the context of E-cadherin cell-cell adhesion complexes, which are central in the maintenance of the normal epithelial phenotype. A major component of these complexes is p120 catenin (p120), which binds and stabilizes E-cadherin to promote its adhesive and tumor suppressing function. However, p120 is also an essential mediator of pro-tumorigenic signals driven by oncogenes, such as Src, and can be phosphorylated at multiple sites. Although alterations in p120 expression have been extensively studied by immunohistochemistry (IHC) in the context of tumor progression, little is known about the status and role of p120 phosphorylation in cancer. Here we show that tyrosine and threonine phosphorylation of p120 in two sites, Y228 and T916, is elevated in renal and breast tumor tissue samples. We also show that tyrosine phosphorylation of p120 at its N-terminus, including at the Y228 site is required for its pro-tumorigenic potential. In contrast, phosphorylation of p120 at T916 does not affect this p120 function. However, phosphorylation of p120 at T916 interferes with epitope recognition of the most commonly used p120 antibody, namely pp120. As a result, this antibody selectively underrepresents p120 levels in tumor tissues, where p120 is phosphorylated. Overall, our data support a role of p120 phosphorylation as a marker and mediator of tumor transformation. Importantly, they also argue that the level and localization of p120 in human cancer tissues immunostained with pp120 needs to be re-evaluated.

Cadherin-6B undergoes macropinocytosis and clathrin-mediated endocytosis during cranial neural crest cell EMT

The epithelial-to-mesenchymal transition (EMT) is important for the formation of migratory neural crest cells during development and is co-opted in human diseases such as cancer metastasis. Chick premigratory cranial neural crest cells lose intercellular contacts, mediated in part by Cadherin-6B (Cad6B), migrate extensively, and later form a variety of adult derivatives. Importantly, modulation of Cad6B is crucial for proper neural crest cell EMT. Although Cad6B possesses a long half-life, it is rapidly lost from premigratory neural crest cell membranes, suggesting the existence of post-translational mechanisms during EMT. We have identified a motif in the Cad6B cytoplasmic tail that enhances Cad6B internalization and reduces the stability of Cad6B upon its mutation. Furthermore, we demonstrate for the first time that Cad6B is removed from premigratory neural crest cells through cell surface internalization events that include clathrin-mediated endocytosis and macropinocytosis. Both of these processes are dependent upon the function of dynamin, and inhibition of Cad6B internalization abrogates neural crest cell EMT and migration. Collectively, our findings reveal the significance of post-translational events in controlling cadherins during neural crest cell EMT and migration.

Inhibition of invasion and metastasis of human liver cancer HCCLM3 cells by portulacerebroside A

CONTEXT

Portulacerebroside A (PCA) is a novel cerebroside compound isolated from Portulaca oleracea L. (Portulacaceae), an edible and medicinal plant distributed in the temperate and tropical zones worldwide.

OBJECTIVE

This study investigates the effects of PCA in human liver cancer HCCLM3 cells on metastasis and invasion.

MATERIALS AND METHODS

After the cells were treated with PCA (2.5, 5, and 10 μg/ml) for 6, 12, 24, or 48 h, adhesion, transwell invasion, and scratch tests were conducted and cell functions were evaluated. Western blot and FQ-RT-PCR assays explored the mechanism of PCA-inhibited invasion and metastasis in the cells.

RESULTS

The adhesion rate of the cells was suppressed at 0.5 h (79.4 ± 1.0, 68.7 ± 1.3, and 58.1 ± 1.3%, versus 100 ± 1.5% in the control), 1 h (78.2 ± 1.2, 70.9 ± 1.6, and 55.4 ± 1.9%, versus 100 ± 1.2% in the control), and 1.5 h (71.6 ± 1.1, 62.3 ± 0.9, and 50.4 ± 0.9%, versus 100 ± 1.1% in the control). The 24 h invasion ability was decreased (356.6 ± 11.2, 204.0 ± 17.6, and 113.0 ± 9.5%, versus 443.6 ± 15.4% in the control). The migration capability was also restrained by PCA for 24 h (324.8 ± 25.4, 250.4 ± 21.0, and 126.3 ± 10.1, versus 381.6 ± 30.6 in the control) and 48 h (470.3 ± 34.3, 404.0 ± 19.7, and 201.0 ± 15.4, versus 752.0 ± 63.6 in the control). There was an increase in the mRNA and protein expression levels of TIMP-2 and nm23-H1, inhibition in the mRNA expression of MTA1, MMP-2, and MMP-9, and suppression in the protein expression of MTA1, RhoA, Rac1/Cdc42, MMP-2, but not RhoC and MMP-9.

CONCLUSION

PCA suppresses the invasion and metastasis of HCCLM3 cells possibly by modulation of the mRNA and protein expression of related parameters. This is the first study to reveal a new potential therapeutic application of PCA in antimetastatic therapy for liver cancer.

Differential effects of estrogen-dependent transactivation vs. transrepression by the estrogen receptor on invasiveness of HER2 overexpressing breast cancer cells

Estrogen (E2) supports breast cancer cell growth but suppresses invasiveness and both actions are antagonized by anti-estrogens. As a consequence, anti-estrogen treatment may increase the invasive potential of estrogen receptor (ER)+ tumor cell sub-populations that are endocrine resistant due to HER2 amplification. Either transactivation or transrepression by E2/ER could lead to both up- and down-regulation of many genes. Inhibition of the transactivation function of ER is adequate to inhibit E2-dependent growth. However, the impact of inhibiting E2-dependent transactivation vs. transrepression by ER on regulation of invasiveness by E2 is less clear. Here we dissect the roles of ER-mediated transactivation and transrepression in the regulation of invasiveness of ER+/HER2+ breast cancer cells by E2. Knocking down the general ER co-activators CBP and p300 prevented activation by E2 of its classical target genes but did not interfere with the ability of E2 to repress its direct target genes known to support invasiveness and tumor progression; there was also no effect on invasiveness or the ability of E2 to regulate invasiveness. On the other hand, overexpression of a co-repressor binding site mutant of ER (L372R) prevented E2-dependent transrepression but not transactivation. The mutant ER abrogated the ability of E2 to suppress invasiveness. E2 can partially down-regulate HER2 but knocking down HER2 below E2-regulated levels did not affect invasiveness or the ability of E2 to regulate invasiveness, although it did inhibit growth. Therefore, in ER+/HER2+ cells, the E2-dependent transrepression by ER rather than its transactivation function is critical for regulation of invasiveness and this is independent of HER2 regulation by E2. The findings suggest that selective inhibitors of transactivation by ER may be more beneficial in reducing tumor progression than conventional anti-estrogens that also antagonize E2-dependent transrepression.

Cdc42 expression in cervical cancer and its effects on cervical tumor invasion and migration

The aim of the present study was to examine Cdc42 expression in cervical cancer and explore its effects on invasion and migration capability of cervical cancer cells. Immunohistochemistry was used to detect Cdc42 expression in normal cervical tissues as well as CIN I or below, CIN II or above, and cervical cancer tissues. Western blot analysis was used to explore Cdc42 expression in normal cervical cell line Crl-2614 and cervical cancer cell line HeLa. Plasmids of constitutively active Cdc42 (Cdc42 CA), wild-type Cdc42 (Cdc42 WT) and dominant negative Cdc42 (Cdc42 DN) were transfected, respectively, into HeLa cells to investigate the impacts of Cdc42 on migration and invasion of cervical cancer cells using Transwell and on cytoskeleton microfilaments using confocal microscopy after immunofluorescence staining. Cdc42 expression was gradually increased in the order of cervical tissues with CIN I or below, CIN II or above and cancer, showing significant difference (P<0.05), and was significantly higher in HeLa cells than in Crl-2614 cells (P<0.05). Migration ability of HeLa cells transfected with Cdc42 CA was significantly higher than that of non-transfected, as well as Cdc42 WT- or Cdc42 DN-transfected HeLa cells (P<0.05). Overexpression of Cdc42 CA can promote filopodia formation in HeLa cells. We concluded that Cdc42 overexpression significantly improved the ability of cervical cancer cells to migrate possibly due to improved pseudopodia formation.

Steady-state acceptor fluorescence anisotropy imaging under evanescent excitation for visualisation of FRET at the plasma membrane

We present a novel imaging system combining total internal reflection fluorescence (TIRF) microscopy with measurement of steady-state acceptor fluorescence anisotropy in order to perform live cell Förster Resonance Energy Transfer (FRET) imaging at the plasma membrane. We compare directly the imaging performance of fluorescence anisotropy resolved TIRF with epifluorescence illumination. The use of high numerical aperture objective for TIRF required correction for induced depolarization factors. This arrangement enabled visualisation of conformational changes of a Raichu-Cdc42 FRET biosensor by measurement of intramolecular FRET between eGFP and mRFP1. Higher activity of the probe was found at the cell plasma membrane compared to intracellularly. Imaging fluorescence anisotropy in TIRF allowed clear differentiation of the Raichu-Cdc42 biosensor from negative control mutants. Finally, inhibition of Cdc42 was imaged dynamically in live cells, where we show temporal changes of the activity of the Raichu-Cdc42 biosensor.

Combined SFK/mTOR inhibition prevents rapamycin-induced feedback activation of AKT and elicits efficient tumor regression

Resistance to receptor tyrosine kinase (RTK) blockade in breast cancer is often mediated by activation of bypass pathways that sustain growth. Src and mammalian target of rapamycin (mTOR) are two intrinsic targets that are downstream of most RTKs. To date, limited clinical efficacy has been observed with either Src or mTOR inhibitors when used as single agents. Resistance to mTOR inhibitors is associated with loss of negative feedback regulation, resulting in phosphorylation and activation of AKT. Herein, we describe a novel role for Src in contributing to rapalog-induced AKT activation. We found that dual activation of Src and the mTOR pathway occurs in nearly half of all breast cancers, suggesting potential cross-talk. As expected, rapamycin inhibition of mTOR results in feedback activation of AKT in breast cancer cell lines. Addition of the Src/c-Abl inhibitor, dasatinib, completely blocks this feedback activation, confirming convergence between Src and the mTOR pathway. Analysis in vivo revealed that dual Src and mTOR inhibition is highly effective in two mouse models of breast cancer. In a luminal disease model, combined dasatinib and rapamycin is more effective at inducing regression than either single agent. Furthermore, the combination of dasatinib and rapamycin delays tumor recurrence following the cessation of treatment. In a model of human EGFR-2-positive (HER2(+)) disease, dasatinib alone is ineffective, but potentiates the efficacy of rapamycin. These data suggest that combining mTOR and Src inhibitors may provide a new approach for treating multiple breast cancer subtypes that may circumvent resistance to targeted RTK therapies.

RAC1 inhibition as a therapeutic target for gefitinib-resistant non-small-cell lung cancer

Although epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (EGFR-TKI), including gefitinib, provide a significant clinical benefit in non-small-cell lung cancer (NSCLC) patients, the acquisition of drug resistance has been known to limit the efficacy of EGFR-TKI therapy. In this study, we demonstrated the involvement of EGF-EGFR signaling in NSCLC cell migration and the requirement of RAC1 in EGFR-mediated progression of NSCLC. We showed the significant role of RAC1 pathway in the cell migration or lamellipodia formation by using gene silencing of RAC1 or induction of constitutive active RAC1 in EGFR-mutant NSCLC cells. Importantly, the RAC1 inhibition suppressed EGFR-mutant NSCLC cell migration and growth in vitro, and growth in vivo even in the gefitinib-resistant cells. In addition, these suppressions by RAC1 inhibition were mediated through MEK or PI3K independent mechanisms. Collectively, these results open up a new opportunity to control the cancer progression by targeting the RAC1 pathway to overcome the resistance to EGFR-TKI in NSCLC patients.

PDZ and LIM domain protein 1(PDLIM1)/CLP36 promotes breast cancer cell migration, invasion and metastasis through interaction with α-actinin

Increased CLP36 expression has been found to be closely associated with breast cancer progression. However, whether and how it contributes to malignant behavior of breast cancer cells were not known. We show here that CLP36 is critical for promoting breast cancer cell migration and invasion in vitro and metastasis in vivo, whereas it is dispensable for breast cell proliferation and anchorage independent growth in vitro and tumor growth in vivo. CLP36 interacted with both α-actinin-1 and -4 in breast cancer cells. Depletion of either α-actinin-1 or -4 inhibited breast cancer cell migration. Furthermore, mutations inhibiting the α-actinin-binding activity abolished the ability of CLP36 to promote breast cancer cell migration. Finally, depletion of CLP36 or disruption of the CLP36-α-actinin complex in breast cancer cells substantially inhibited Cdc42 activation, cell polarization and migration. Our results identify CLP36 as an important regulator of breast cancer cell migration and metastasis, and shed light on how increased CLP36 expression contributes to progression of breast cancer.