Toca-1 is suppressed by p53 to limit breast cancer cell invasion and tumor metastasis

Isoprenylcysteine carboxyl methyltransferase (ICMT) promotes invadopodia formation and metastasis in cancer cells

Isoprenyl cysteine carboxyl methyltransferase (ICMT) catalyzes the last step of the prenylation pathway. Previously, we found that high ICMT levels enhance tumorigenesis in vivo and that its expression is repressed by the p53 tumor suppressor. Based on evidence suggesting that some ICMT substrates affect invasive traits, we wondered if this enzyme may promote metastasis. In this work, we found that ICMT overexpression enhanced lung metastasis in vivo. Accordingly, ICMT overexpression also promoted cellular functions associated with aggressive phenotypes such as migration and invasion in vitro. Considering that some ICMT substrates are involved in the regulation of actin cytoskeleton, we hypothesized that actin-rich structures, associated with invasion and metastasis, may be affected. Our findings revealed that ICMT enhanced the formation of invadopodia. Additionally, by analyzing cancer patient databases, we found that ICMT is overexpressed in several tumor types. Furthermore, the concurrent expression of ICMT and CTTN, which encodes a crucial component of invadopodia, showed a significant correlation with clinical outcome. In summary, our work identifies ICMT overexpression as a relevant alteration in human cancer that promotes the development of metastatic tumors.

Targeted MDM2 Degradation Reveals a New Vulnerability for p53-Inactivated Triple-Negative Breast Cancer

Triple-negative breast cancers (TNBC) frequently inactivate p53, increasing their aggressiveness and therapy resistance. We identified an unexpected protein vulnerability in p53-inactivated TNBC and designed a new PROteolysis TArgeting Chimera (PROTAC) to target it. Our PROTAC selectively targets MDM2 for proteasome-mediated degradation with high-affinity binding and VHL recruitment. MDM2 loss in p53 mutant/deleted TNBC cells in two-dimensional/three-dimensional culture and TNBC patient explants, including relapsed tumors, causes apoptosis while sparing normal cells. Our MDM2-PROTAC is stable in vivo, and treatment of TNBC xenograft-bearing mice demonstrates tumor on-target efficacy with no toxicity to normal cells, significantly extending survival. Transcriptomic analyses revealed upregulation of p53 family target genes. Investigations showed activation and a required role for TAp73 to mediate MDM2-PROTAC-induced apoptosis. Our data, challenging the current MDM2/p53 paradigm, show MDM2 is required for p53-inactivated TNBC cell survival, and PROTAC-targeted MDM2 degradation is an innovative potential therapeutic strategy for TNBC and superior to existing MDM2 inhibitors.

SIGNIFICANCE

p53-inactivated TNBC is an aggressive, therapy-resistant, and lethal breast cancer subtype. We designed a new compound targeting an unexpected vulnerability we identified in TNBC. Our MDM2-targeted degrader kills p53-inactivated TNBC cells, highlighting the requirement for MDM2 in TNBC cell survival and as a new therapeutic target for this disease. See related commentary by Peuget and Selivanova, p. 1043. This article is highlighted in the In This Issue feature, p. 1027.

Cancer informatics analysis indicates high CHAC2 associated with unfavorable prognosis in breast cancer

Breast cancer remains the most commonly diagnosed cancer worldwide and exhibits a poor prognosis. The induction of genetic changes deregulates several genes that increase the disposal towards this life-threatening disease. CHAC2, a member of the glutathione degrading enzyme family has been shown to suppress gastric and colorectal cancer progression, however, the expression of CHAC2 in breast cancer has not been reported. We did an analysis of CHAC2 expression in breast cancer patients from various online tools like UALCAN, GEPIA2, GENT2, TIMER2, and bcGenExminer v4.8. Further, we used the Kaplan-Meier plotter to establish the significance of CHAC2 in BC patient survival and prognosis while TISIDB and TIMER databases were used to investigate the filtration of immune cells. The results showed that CHAC2 levels were high in breast cancer patients and elevated CHAC2 was associated with low overall survival. Taken together, the results of the present study show that like its paralog CHAC1, CHAC2 may also be an important biomarker and could have a potential therapeutic implication in breast cancer.

Bending over backwards: BAR proteins and the actin cytoskeleton in mammalian receptor-mediated endocytosis

The role of the actin cytoskeleton during receptor-mediated endocytosis (RME) has been well characterized in yeast for many years. Only more recently has the interplay between the actin cytoskeleton and RME been extensively explored in mammalian cells. These studies have revealed the central roles of BAR proteins in RME, and have demonstrated significant roles of BAR proteins in linking the actin cytoskeleton to this cellular process. The actin cytoskeleton generates and transmits mechanical force to promote the extension of receptor-bound endocytic vesicles into the cell. Many adaptor proteins link and regulate the actin cytoskeleton at the sites of endocytosis. This review will cover key effectors, adaptors and signalling molecules that help to facilitate the invagination of the cell membrane during receptor-mediated endocytosis, including recent insights gained on the roles of BAR proteins. The final part of this review will explore associations of alterations to genes encoding BAR proteins with cancer.

Lotus leaf extract inhibits ER- breast cancer cell migration and metastasis

BACKGROUND

Patients with estrogen receptor negative (ER^-) breast cancer have poor prognosis due to high rates of metastasis. However, there is no effective treatment and drugs for ER^- breast cancer metastasis. Our purpose of this study was to evaluate the effect of lotus leaf alcohol extract (LAE) on the cell migration and metastasis of ER^- breast cancer.

METHODS

The anti-migratory effect of LAE were analyzed in ER^- breast cancer cells including SK-BR-3, MDA-MB-231 and HCC1806 cell lines. Cell viability assay, wound-healing assay, RNA-sequence analysis and immunoblotting assay were used to evaluate the cytotoxicity and anti-migratory effect of LAE. To further investigate the inhibitory effect of LAE on metastasis in vivo, subcutaneous xenograft and intravenous injection nude mice models were established. Lung and liver tissues were analyzed by the hematoxylin and eosin staining and immunoblotting assay.

RESULTS

We found that lotus LAE, not nuciferine, inhibited cell migration significantly in SK-BR-3, MDA-MB-231 and HCC1806 breast cancer cells, and did not affect viability of breast cancer cells. The anti-migratory effect of LAE was dependent on TGF-β1 signaling, while independent of Wnt signaling and autophagy influx. Intracellular H₂O₂ was involved in the TGF-β1-related inhibition of cell migration. LAE inhibited significantly the breast cancer cells metastasis in mice models. RNA-sequence analysis showed that extracellular matrix signaling pathways are associated with LAE-suppressed cell migration.

CONCLUSIONS

Our findings demonstrated that lotus leaf alcohol extract inhibits the cell migration and metastasis of ER^- breast cancer, at least in part, via TGF-β1/Erk1/2 and TGF-β1/SMAD3 signaling pathways, which provides a potential therapeutic strategy for ER^- breast cancer.

High formin binding protein 17 (FBP17) expression indicates poor differentiation and invasiveness of ductal carcinomas

Formin binding protein 17 (FBP17) belongs to Cdc-42 interacting protein 4 subfamily of F-BAR proteins. Recently, we had reported that FBP17 was overexpressed in invasive breast cancer cells and interacts with the actin regulatory proteins. We also reported that FBP17 promotes invadopodia formation and enhances extracellular matrix degradation. The current study determines FBP17 expression in invasive ductal carcinomas (IDCs) using breast cancer tissue microarrays (TMAs) (82 IDCs with variable receptor status and 8 Normal adjacent tissues) and its correlation with the clinico-pathological features. Immunohistochemistry of human breast cancer TMAs showed the significant elevation in the levels of FBP17 in breast cancer tissues than the normal (p ≤ 0.0001). Interestingly, FBP17 had a higher expression in invasive molecular subtypes HER2 and TNBC (p ≤ 0.05). Similarly, tumors with lymph node positive status showed elevated FBP17 expression in HER2 and TNBC subtypes (p ≤ 0.05). Surprisingly, grade 3 tumors demonstrated higher FBP17 expression (p ≤ 0.01) indicating its role in poorly differentiated tumors. Together, the data demonstrates the overexpression of FBP17 in invasive and poorly differentiated tumors. Understanding the role of FBP17 in poor differentiation and invasion of tumors in molecular subtypes at various level might represent as a potential molecular target against the disease.

Casticin inhibits breast cancer cell migration and invasion by down-regulation of PI3K/Akt signaling pathway

Casticin is one of the major active components isolated from Fructus viticis Increasing studies have revealed that casticin has potential anticancer activity in various cancer cells, but its effects on breast cancer cell migration and invasion are still not well known. Therefore, the ability of cell migration and invasion in the breast cancer MDA-MB-231 and 4T1 cells treated by casticin was investigated. The results indicated that casticin significantly inhibited cell migration and invasion in the cells exposed to 0.25 and 0.50 µM of casticin for 24 h. Casticin treatment reduced matrix metalloproteinase (MMP) 9 (MMP-9) activity and down-regulated MMP-9 mRNA and protein expression, but not MMP-2. Casticin treatment suppressed the nuclear translocation of transcription factors c-Jun and c-Fos, but not nuclear factor-κB (NF-κB), and decreased the phosphorylated level of Akt (p-Akt). Additionally, the transfection of Akt overexpression vector to MDA-MB-231 and 4T1 cells could up-regulate MMP-9 expression concomitantly with a marked increase in cell invasion, but casticin treatment reduced Akt, p-Akt, and MMP-9 protein levels and inhibited the ability of cell invasion in breast cancer cells. Additionally, casticin attenuated lung metastasis of mouse 4T1 breast cancer cells in the mice and down-regulated MMP-9 expression in the lung tissues of mice treated by casticin. These findings suggest that MMP-9 expression suppression by casticin may act through inhibition of the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway, which in turn results in the inhibitory effects of casticin on cell migration and invasion in breast cancer cells. Therefore, casticin may have potential for use in the treatment of breast cancer invasion and metastasis.

Adipocytes Promote Early Steps of Breast Cancer Cell Dissemination via Interleukin-8

Fat is a major tissue component in human breast cancer (BC). Whether breast adipocytes (BAd) affect early stages of BC metastasis is yet unknown. BC progression is dependent on angiogenesis and inflammation, and interleukin-8 (IL-8) and vascular endothelial growth factor (VEGF) are key regulators of these events. Here, we show that BAd increased the dissemination of estrogen receptor positive BC cells (BCC) in vivo in the zebrafish model of metastasis, while dissemination of the more aggressive and metastatic BCC such as estrogen receptor negative was unaffected. While anti-VEGF and anti-IL-8 exhibited equal inhibition of angiogenesis at the primary tumor site, anti-IL-8 reduced BCC dissemination whereas anti-VEGF had minor effects on this early metastatic event. Mechanistically, overexpression of cell-adhesion molecules in BCC and neutrophils via IL-8 increased the dissemination of BCC. Importantly, the extracellular in vivo levels of IL-8 were 40-fold higher than those of VEGF in human BC. Our results suggest that IL-8 is a clinical relevant and promising therapeutic target for human BC.

High expression of FBP17 in invasive breast cancer cells promotes invadopodia formation

Metastatic spread of the cancer is usually the consequence of the activation of signaling pathways that generate cell motility and tissue invasion. Metastasis involves the reorganization of cytoskeleton and cell shape for the swift movement of the cells through extracellular matrix. Previously, we have described the invasive and metastatic role played by one of the members (Toca-1) of CIP4 subfamily of F-BAR proteins. In the present study, we address the role of another member (FBP17) of same family in the invasion breast cancer cells. Here, we report that the formin-binding protein 17 (FBP17) is highly expressed at both mRNA and protein levels in breast cancer cells. The study showed the association of FBP17 with cytoskeletal actin regulatory proteins like dynamin and cortactin. To determine its role in extracellular matrix (ECM) degradation, we achieved stable knockdown of FBP17 in MDA-MB-231 cells. FBP17 knockdown cells showed a defect and were found to be compromised in the degradation of ECM indicating the role of FBP17 in the invasion of breast cancer cells. Our results suggest that FBP17 is highly expressed in breast cancer cells and facilitates the invasion of breast cancer cells.

Identification of key genes in non‑alcoholic fatty liver disease progression based on bioinformatics analysis

Due to economic development and lifestyle changes, the incidence of non-alcoholic fatty liver disease (NAFLD) has gradually increased in recent years. However, the pathogenesis of NAFLD is not yet fully understood. To identify candidate genes that contribute to the development and progression of NAFLD, two microarray datasets were downloaded from the Gene Expression Omnibus database. The differentially expressed genes (DEGs) were identified and functional enrichment analyses were performed. A protein-protein interaction network was constructed and modules were extracted using the Search Tool for the Retrieval of Interacting Genes and Cytoscape. The enriched functions and pathways of the DEGs included ‘cellular macromolecule biosynthetic process’, ‘cellular response to chemical stimulus’, ‘extracellular matrix organization’, ‘metabolic pathways’, ‘insulin resistance’ and ‘forkhead box protein O1 signaling pathway’. The DEGs, including type-1 angiotensin II receptor, formin-binding protein 1-like, RNA-binding protein with serine-rich domain 1, Ras-related C3 botulinum toxin substrate 1 and polyubiquitin-C, were identified using multiple bioinformatics methods and validated in vitro with reverse transcription-quantitative polymerase chain reaction analysis. In conclusion, five hub genes were identified in the present study, and they may aid in understanding of the molecular mechanisms underlying the development and progression of NAFLD.

Identification of a novel p53 target, COL17A1, that inhibits breast cancer cell migration and invasion

p53 mutation is a marker of poor prognosis in breast cancers. To identify downstream targets of p53, we screened two transcriptome datasets, including cDNA microarrays of MCF10A breast epithelial cells with wild-type p53 or p53-null background, and RNA sequence analysis of breast invasive carcinoma. Here, we unveil ten novel p53 target candidates that are up-regulated after the induction of p53 in wild-type cells. Their expressions are also high in breast invasive carcinoma tissues with wild-type p53. The GO analysis identified epidermis development and ectoderm development, which COL17A1 participates, as significantly up-regulated by wild-type p53. The COL17A1 expressions increased in a p53-dependent manner in human breast cells and mouse mammary tissues. Reporter assay and ChIP assay identified intronic p53-binding sequences in the COL17A1 gene. The MDA-MB-231 cells that genetically over-express COL17A1 gene product exhibited reduced migration and invasion in vitro. Similarly, COL17A1 expression was decreased in metastatic tumors compared to primary tumors and normal tissues, even from the same patients. Moreover, high COL17A1 expression was associated with longer survival of patients with invasive breast carcinoma. In conclusion, we revealed that COL17A1 is a novel p53 transcriptional target in breast tissues that inhibits cell migration and invasion and is associated with better prognosis.

Numb Gene Enhances Radiation Sensitivity of Nonsmall Cell Lung Cancer Stem Cells

OBJECTIVE

To study the effects of Numb gene expression on radiation sensitivity of nonsmall cell lung cancer (NSCLC) stem cells.

MATERIALS AND METHODS

The side population (SP) cells A549-SP were transfected with pcDNA3.1 (pcDNA3.1 group), pcDNA-Numb (pcDNA-Numb group) and shRNA-Numb (shRNA-Numb group). Real-time quantitative polymerase chain reaction and Western blot were performed to determine Numb expression; MTT method was used to measure the proliferation activity change of the NSCLC stem cells both before and after irradiation with different doses of 60Coγ ray; Hoechst staining and Annexin V-FITC/PI were used to detect the apoptosis of the NSCLC stem cells; and colony-forming assay was used to determine the effect of Numb expression on radiation sensitivity of the NSCLC stem cells.

RESULTS

Increased mRNA and protein expressions of the A549-SP cells were found in the pcDNA-Numb group, and decreased mRNA and protein expressions were found in the shRNA-Numb group. The optical density value of the cells decreased in the pcDNA-Numb group but increased in the shRNA-Numb group. The cells with over-expressed Numb showed obvious nuclear condensation and fragmentation; the apoptosis rate increased significantly. The cells with knockdown Numb showed less nuclear damage; the apoptosis rate significantly decreased. After irradiation, the cells in the pcDNA-Numb group showed decreased survival rate, clonality, and the values of D0, Dq, N, and SF2; whereas the cells in the shRNA-Numb group showed the opposite trend.

CONCLUSIONS

Radiation sensitivity of NSCLC stem cells was enhanced with the increase of Numb expression. Determination of Numb expression helped to evaluate the response of lung cancer to radiotherapy, which was important for guiding tumor treatment clinically.

p53 inhibits the expression of p125 and the methylation of POLD1 gene promoter by downregulating the Sp1-induced DNMT1 activities in breast cancer

p125 is one of four subunits of human DNA polymerases – DNA Pol δ as well as one of p53 target protein encoded by POLD1. However, the function and significance of p125 and the role that p53 plays in regulating p125 expression are not fully understood in breast cancer. Tissue sections of human breast cancer obtained from 70 patients whose median age was 47.6 years (range: 38–69 years) with stage II–III breast cancer were studied with normal breast tissue from the same patients and two human breast cell lines (MCF-7 and MCF-10A). p53 expression levels were reduced, while p125 protein expression was increased in human breast cancer tissues and cell line detected by Western blot and quantitative reverse transcriptase-polymerase chain reaction. The methylation level of the POLD1 gene promoter was greater in breast cancer tissues and cells when compared with normal tissues and cells. In MCF-7 cell model, p53 overexpression caused a decrease in the level of p125 protein, while the methylation level of the p125 gene promoter was also inhibited by p53 overexpression. To further investigate the regulating mechanism of p53 on p125 expression, our study focused on DNA methyltransferase 1 (DNMT1) and transcription factor Sp1. Both DNMT1 and Sp1 protein expression were reduced when p53 was overexpressed in MCF-7 cells. The Sp1 binding site appears to be important for DNMT1 gene transcription; Sp1 and p53 can bind together, which means that DNMT1 gene expression may be downregulated by p53 through binding to Sp1. Because DNMT1 methylation level of the p125 gene promoter can affect p125 gene transcription, we propose that p53 may indirectly regulate p125 gene promoter expression through the control of DNMT1 gene transcription. In conclusion, the data from this preliminary study have shown that p53 inhibits the methylation of p125 gene promoter by downregulating the activities of Sp1 and DNMT1 in breast cancer.

Fe65 Suppresses Breast Cancer Cell Migration and Invasion through Tip60 Mediated Cortactin Acetylation

Fe65 is a brain-enriched adaptor protein known for its role in the action of the Aβ amyloid precursor protein in neuronal cells and Alzheimer’s disease, but little is known about its functions in cancer cells. The present study documents for the first time a role of Fe65 in suppressing breast cancer cell migration and invasion. Mechanistic studies suggest that the suppression is mediated through its phosphotyrosine binding domain 1 that mediates the recruitment of Tip60 to cortactin to stimulate its acetylation. The studies identify the Tip60 acetyltransferase as a cytoplasmic drug target for the therapeutic intervention of metastatic breast cancers.

A complex of ZO-1 and the BAR-domain protein TOCA-1 regulates actin assembly at the tight junction

An alternative splice in TOCA-1 targets it to tight junctions. KO of TOCA-1 results in increased flux and decreased tight junction membrane dynamics. Ultrastructural analysis shows actin accumulation at the adherens junction. Identification of the ZO-1/TOCA-1 complex provides insights into tight junction barrier dependence on the dynamic nature of cell–cell contacts and junctional actin.

Assembly and sealing of the tight junction barrier are critically dependent on the perijunctional actin cytoskeleton, yet little is known about physical and functional links between barrier-forming proteins and actin. Here we identify a novel functional complex of the junction scaffolding protein ZO-1 and the F-BAR–domain protein TOCA-1. Using MDCK epithelial cells, we show that an alternative splice of TOCA-1 adds a PDZ-binding motif, which binds ZO-1, targeting TOCA-1 to barrier contacts. This isoform of TOCA-1 recruits the actin nucleation–promoting factor N-WASP to tight junctions. CRISPR-Cas9–mediated knockout of TOCA-1 results in increased paracellular flux and delayed recovery in a calcium switch assay. Knockout of TOCA-1 does not alter FRAP kinetics of GFP ZO-1 or occludin, but longer term (12 h) time-lapse microscopy reveals strikingly decreased tight junction membrane contact dynamics in knockout cells compared with controls. Reexpression of TOCA-1 with, but not without, the PDZ-binding motif rescues both altered flux and membrane contact dynamics. Ultrastructural analysis shows actin accumulation at the adherens junction in TOCA-1–knockout cells but unaltered freeze-fracture fibril morphology. Identification of the ZO-1/TOCA-1 complex provides novel insights into the underappreciated dependence of the barrier on the dynamic nature of cell-to-cell contacts and perijunctional actin.