Construction of a gene signature associated with anoikis to evaluate the prognosis and immune infiltration in patients with colorectal cancer

Background

Colorectal cancer (CRC) is characterized by a high metastasis rate, leading to poor prognosis and increased mortality. Anoikis, a physiological process, serves as a crucial barrier against metastasis. The objective of this research is to construct a prognostic model for CRC based on genes associated with anoikis.

Methods

The study involved differential analysis and univariate Cox analysis of anoikis-related genes (ARGs), resulting in the selection of 47 genes closely associated with prognosis. Subsequently, unsupervised k-means clustering analysis was conducted on all patients to identify distinct clusters. Survival analysis, principal component analysis (PCA), and t-distributed stochastic neighbor embedding (t-SNE) analysis were performed on the different clusters to investigate associations within the clusters. Gene set variation analysis (GSVA) and gene set enrichment analysis (GSEA) were utilized to assess metabolic pathway enrichment between the identified clusters. Furthermore, single-sample GSEA (ssGSEA) was applied to explore variations in immune infiltration. Multivariable Cox regression and least absolute shrinkage and selection operator (LASSO) analyses were conducted to construct a risk model based on ten signatures, which enabled the grouping of all samples according to their risk scores. The prognostic value of the model was validated using receiver operating characteristic (ROC) curves, area under the curve (AUC) calculations, and survival curves. Additionally, the expression of candidate genes was validated using quantitative real-time polymerase chain reaction (qRT-PCR).

Results

Forty-seven survival-related ARGs were screened out. Somatic mutation analysis showed that these genes revealed a high mutation rate. Based on their expression, two clusters were identified. Cluster B patients exhibited a shortened overall survival and higher immune infiltration. A risk scoring model including ten genes was subsequently developed, which exhibited excellent prognostic predictive ability for CRC, as evidenced by the survival curve, ROC curve, and AUC curve. In addition, a nomogram was developed for predicting 3- and 5-year survival probabilities. The qRT-PCR results indicated the dissimilarities among the ten signatures in the tumor tissues and adjacent tissues of patients with CRC were fundamentally consistent with the analytical findings.

Conclusions

This study comprehensively evaluated the prognostic significance of ARGs in CRC. It identified two distinct anoikis-related clusters and examined their respective immune microenvironments. Furthermore, an ARGs signature was developed to effectively predict the prognosis of CRC, thereby establishing a solid foundation for investigating the clinical prognostic role of anoikis in CRC.

C9orf10/Ossa regulates the bone metastasis of established lung adenocarcinoma cell subline H322L-BO4 in a mouse model

Lung cancer frequently metastasizes to the bones. An in vivo model is urgently required to identify potential therapeutic targets for the prevention and treatment of lung cancer with bone metastasis. We established a lung adenocarcinoma cell subline (H322L-BO4) that specifically showed metastasis to the leg bones and adrenal glands. This was achieved by repeated isolation of metastatic cells from the leg bones of mice. The cells were intracardially injected into nude mice. Survival was prolonged for mice that received H322L-BO4 cells versus original cells (H322L). H322L-BO4 cells did not exhibit obvious changes in general in vitro properties associated with the metastatic potential (e.g., cell growth, migration, and invasion) compared with H322L cells. However, the phosphorylation of chromosome 9 open reading frame 10/oxidative stress-associated Src activator (C9orf10/Ossa) was increased in H322L-BO4 cells. This result confirmed the increased anchorage independence through C9orf10/Ossa-mediated activation of Src family tyrosine kinase. Reduction of C9orf10/Ossa by shRNA reduced cells' metastasis to the leg bone and prolonged survival in mice. These findings indicate that H322L-BO4 cells can be used to evaluate the effect of candidate therapeutic targets against bone metastatic lung cancer cells. Moreover, C9orf10/Ossa may be a useful target for treatment of lung cancer with bone metastasis.

G-protein-coupled estrogen receptor 1 promotes peritoneal metastasis of gastric cancer through nicotinamide adenine dinucleotide kinase 1-mediated redox modulation

Adipose tissue is the second most important site of estrogen production, where androgens are converted into estrogen by aromatase. While gastric cancer patients often develop adipocyte-rich peritoneal metastasis, the underlying mechanism remains unclear. In this study, we identified the G-protein-coupled estrogen receptor (GPER1) as a promoter of gastric cancer peritoneal metastasis. Functional in vitro studies revealed that β-Estradiol (E2) or the GPER1 agonist G1 inhibited anoikis in gastric cancer cells. Additionally, genetic overexpression or knockout of GPER1 significantly inhibited or enhanced gastric cancer cell anoikis in vitro and peritoneal metastasis in vivo, respectively. Mechanically, GPER1 knockout disrupted the NADPH pool and increased reactive oxygen species (ROS) generation. Conversely, overexpression of GPER1 had the opposite effects. GPER1 suppressed nicotinamide adenine dinucleotide kinase 1(NADK1) ubiquitination and promoted its phosphorylation, which were responsible for the elevated expression of NADK1 at protein levels and activity, respectively. Moreover, genetic inhibition of NADK1 disrupted NADPH and redox homeostasis, leading to high levels of ROS and significant anoikis, which inhibited lung and peritoneal metastasis in cell-based xenograft models. In summary, our study suggests that inhibiting GPER1-mediated NADK1 activity and its ubiquitination may be a promising therapeutic strategy for peritoneal metastasis of gastric cancer.

A Novel Role of Connective Tissue Growth Factor in the Regulation of the Epithelial Phenotype

BACKGROUND

Epithelial-mesenchymal transition (EMT) is a biological process where epithelial cells lose their adhesive properties and gain invasive, metastatic, and mesenchymal properties. Maintaining the balance between the epithelial and mesenchymal stage is essential for tissue homeostasis. Many of the genes promoting mesenchymal transformation have been identified; however, our understanding of the genes responsible for maintaining the epithelial phenotype is limited. Our objective was to identify the genes responsible for maintaining the epithelial phenotype and inhibiting EMT.

METHODS

RNA seq was performed using an vitro model of EMT. CTGF expression was determined via qPCR and Western blot analysis. The knockout of CTGF was completed using the CTGF sgRNA CRISPR/CAS9. The tumorigenic potential was determined using NCG mice.

RESULTS

The knockout of CTGF in epithelial ovarian cancer cells leads to the acquisition of functional characteristics associated with the mesenchymal phenotype such as anoikis resistance, cytoskeleton remodeling, increased cell stiffness, and the acquisition of invasion and tumorigenic capacity.

CONCLUSIONS

We identified CTGF is an important regulator of the epithelial phenotype, and its loss is associated with the early cellular modifications required for EMT. We describe a novel role for CTGF, regulating cytoskeleton and the extracellular matrix interactions necessary for the conservation of epithelial structure and function. These findings provide a new window into understanding the early stages of mesenchymal transformation.

MCL1 Inhibition Overcomes the Aggressiveness Features of Triple-Negative Breast Cancer MDA-MB-231 Cells

Triple-Negative Breast Cancer (TNBC) is a particularly aggressive subtype among breast cancers (BCs), characterized by anoikis resistance, high invasiveness, and metastatic potential as well as Epithelial-Mesenchymal Transition (EMT) and stemness features. In the last few years, our research focused on the function of MCL1, an antiapoptotic protein frequently deregulated in TNBC. Here, we demonstrate that MCL1 inhibition by A-1210477, a specific BH3-mimetic, promotes anoikis/apoptosis in the MDA-MB-231 cell line, as shown via an increase in proapoptotic markers and caspase activation. Our evidence also shows A-1210477 effects on Focal Adhesions (FAs) impairing the integrin trim and survival signaling pathways, such as FAK, AKT, ERK, NF-κB, and GSK3β-inducing anoikis, thus suggesting a putative role of MCL1 in regulation of FA dynamics. Interestingly, in accordance with these results, we observed a reduction in migratory and invasiveness capabilities as confirmed by a decrease in metalloproteinases (MMPs) levels following A-1210477 treatment. Moreover, MCL1 inhibition promotes a reduction in EMT characteristics as demonstrated by the downregulation of Vimentin, MUC1, DNMT1, and a surprising re-expression of E-Cadherin, suggesting a possible mesenchymal-like phenotype reversion. In addition, we also observed the downregulation of stemness makers such as OCT3/4, SOX2, NANOG, as well as CD133, EpCAM, and CD49f. Our findings support the idea that MCL1 inhibition in MDA-MB-231 could be crucial to reduce anoikis resistance, aggressiveness, and metastatic potential and to minimize EMT and stemness features that distinguish TNBC.

Long non-coding RNAs modulate tumor microenvironment to promote metastasis: novel avenue for therapeutic intervention

Cancer is a devastating disease and the primary cause of morbidity and mortality worldwide, with cancer metastasis responsible for 90% of cancer-related deaths. Cancer metastasis is a multistep process characterized by spreading of cancer cells from the primary tumor and acquiring molecular and phenotypic changes that enable them to expand and colonize in distant organs. Despite recent advancements, the underlying molecular mechanism(s) of cancer metastasis is limited and requires further exploration. In addition to genetic alterations, epigenetic changes have been demonstrated to play an important role in the development of cancer metastasis. Long non-coding RNAs (lncRNAs) are considered one of the most critical epigenetic regulators. By regulating signaling pathways and acting as decoys, guides, and scaffolds, they modulate key molecules in every step of cancer metastasis such as dissemination of carcinoma cells, intravascular transit, and metastatic colonization. Gaining a good knowledge of the detailed molecular basis underlying lncRNAs regulating cancer metastasis may provide previously unknown therapeutic and diagnostic lncRNAs for patients with metastatic disease. In this review, we concentrate on the molecular mechanisms underlying lncRNAs in the regulation of cancer metastasis, the cross-talk with metabolic reprogramming, modulating cancer cell anoikis resistance, influencing metastatic microenvironment, and the interaction with pre-metastatic niche formation. In addition, we also discuss the clinical utility and therapeutic potential of lncRNAs for cancer treatment. Finally, we also represent areas for future research in this rapidly developing field.

Transformable ECM Deprivation System Effectively Suppresses Renal Cell Carcinoma by Reversing Anoikis Resistance and Increasing Chemotherapy Sensitivity

Extracellular matrix (ECM) is crucial in various biological functions during tumor progression, including induction of anoikis resistance and cell adhesion-mediated drug resistance (CAM-DR). Fibronectin (FN) is a vital ECM component with direct regulatory effects on ECM-mediated anoikis resistance and CAM-DR, making it an attractive and innovative therapeutic target for depriving ECM in tumor tissue. Herein, an ECM deprivation system (EDS) is developed based on FN targeting self-assembly peptide for constructing nanofibers in the ECM of renal cell carcinoma (RCC), which contributes to: i) targeting and recognizing FN to form nanofibers for long-term retention in ECM, ii) reversing anoikis resistance via arresting the FN signaling pathway, and iii) serving as a drug-loading platform for sensitizing chemotherapy by ameliorating CAM-DR. The results reveal that EDS significantly reverses anoikis resistance of RCC cells by inhibiting the phosphorylation of FAK, a positive regulator of the FN signaling pathway. Meanwhile, EDS serves as a chemotherapy-sensitizer of cancer, exerting significant synergistic effects with doxorubicin (DOX). In vivo validation experiments show that EDS effectively suppresses metastasis and tumor growth with chemotherapy resistance. Collectively, the innovative EDS notably inhibits the tumor-promoting effect of ECM and may provide a novel approach for suppressing ECM and enhancing chemo-drug sensitivity.

Cellular Model of Malignant Transformation of Primary Human Astrocytes Induced by Deadhesion/Readhesion Cycles

Astrocytoma is the most common and aggressive tumor of the central nervous system. Genetic and environmental factors, bacterial infection, and several other factors are known to be involved in gliomagenesis, although the complete underlying molecular mechanism is not fully understood. Tumorigenesis is a multistep process involving initiation, promotion, and progression. We present a human model of malignant astrocyte transformation established by subjecting primary astrocytes from healthy adults to four sequential cycles of forced anchorage impediment (deadhesion). After limiting dilution of the surviving cells obtained after the fourth deadhesion/readhesion cycle, three clones were randomly selected, and exhibited malignant characteristics, including increased proliferation rate and capacity for colony formation, migration, and anchorage-independent growth in soft agar. Functional assay results for these clonal cells, including response to temozolomide, were comparable to U87MG—a human glioblastoma-derived cell lineage—reinforcing malignant cell transformation. RNA-Seq analysis by next-generation sequencing of the transformed clones relative to the primary astrocytes revealed upregulation of genes involved in the PI3K/AKT and Wnt/β-catenin signaling pathways, in addition to upregulation of genes related to epithelial–mesenchymal transition, and downregulation of genes related to aerobic respiration. These findings, at a molecular level, corroborate the change in cell behavior towards mesenchymal-like cell dedifferentiation. This linear progressive model of malignant human astrocyte transformation is unique in that neither genetic manipulation nor treatment with carcinogens are used, representing a promising tool for testing combined therapeutic strategies for glioblastoma patients, and furthering knowledge of astrocytoma transformation and progression.

BMP4 enhances anoikis resistance and chemoresistance of breast cancer cells through canonical BMP signaling

Bone morphogenetic proteins (BMPs) regulate cell fate during development and mediate cancer progression. In this study, we investigated the role of BMP4 in proliferation, anoikis resistance, metastatic migration, and drug resistance of breast cancer cells. We utilized breast cancer cell lines and clinical samples representing different subtypes to understand the functional effect of BMP4 on breast cancer. The BMP pathway was inhibited with the small molecule inhibitor LDN193189 hydrochloride (LDN). BMP4 signaling enhanced the expression of stem cell genes CD44, ALDH1A3, anti-apoptotic gene BCL2 and promoted anoikis resistance in MDA-MB-231 breast cancer cells. BMP4 enhanced self-renewal and chemoresistance in MDA-MB-231 by upregulating Notch signaling while LDN treatment abrogated anoikis resistance and proliferation of anoikis resistant breast cancer cells in the osteogenic microenvironment. Conversely, BMP4 downregulated proliferation, colony-forming ability, and suppressed anoikis resistance in MCF7 and SkBR3 cells, while LDN treatment promoted tumor spheroid formation and growth. These findings indicate that BMP4 has a context-dependent role in breast cancer. Further, our data with MDA-MB-231 cells representing triple-negative breast cancer suggest that BMP inhibition might impair its metastatic spread and colonization.

Silencing ZIC2 abrogates tumorigenesis and anoikis resistance of non-small cell lung cancer cells by inhibiting Src/FAK signaling

Aberrant expression of the zinc finger protein (ZIC) family has been extensively reported to contribute to progression and metastasis in multiple human cancers. However, the functional roles and underlying mechanisms of ZIC2 in non-small cell lung cancer (NSCLC) are largely unknown. In this study, ZIC2 expression was evaluated using qRT-PCR, western blot, and immunohistochemistry, respectively. Animal experiments in vivo and functional assays in vitro were performed to investigate the role of ZIC2 in NSCLC. Luciferase assays and chromatin immunoprecipitation (ChIP) were carried out to explore the underlying target involved in the roles of ZIC2 in NSCLC. Here, we reported that ZIC2 was upregulated in NSCLC tissues, and high expression of ZIC2 predicted worse overall and progression-free survival of NSCLC patients. Silencing ZIC2 repressed tumorigenesis and reduced the anoikis resistance of NSCLC cells. Mechanical investigation further revealed that silencing ZIC2 transcriptionally inhibited Src expression and inactivated steroid receptor coactivator/focal adhesion kinase signaling, which further attenuated the anoikis resistance of NSCLC cells. Importantly, our results showed that the number of circulating tumor cells (CTCs) was positively correlated with ZIC2 expression in NSCLC patients. Collectively, our findings unravel a novel mechanism implicating ZIC2 in NSCLC, which will facilitate the development of anti-tumor strategies in NSCLC.

HRC promotes anoikis resistance and metastasis by suppressing endoplasmic reticulum stress in hepatocellular carcinoma

Histidine-rich calcium binding protein (HRC) is markedly overexpressed in hepatocellular carcinoma (HCC) and is significantly correlated with metastasis. Anoikis resistance and endoplasmic reticulum (ER) stress may have a critical effect on survival before metastasis. However, the potential functions of HRC in anoikis resistance in HCC remain unknown. Here, we uncovered the clinical value of HRC and its functional significance on anoikis in HCC. The positive expression of HRC was observably correlated with tumor size, tumor encapsulation, and tumor-node-metastasis (TNM) stage. The expression of HRC increased in HCC cells cultured in suspension. HRC enhanced the anoikis resistance of HCC, and promoted the HCC metastasis in vivo. Mechanistically, the anoikis resistance was probably dependent on endoplasmic reticulum stress. Modulating HRC level changed the ERS to affect anoikis resistance by acting protein kinase RNA-like ER kinase (PERK)-eIF2a-ATF4-CHOP signaling axis. In conclusion, we define HRC as a novel candidate oncogene involved in anoikis resistance and HCC metastasis, and provide a new potential therapeutic target for HCC.

Acidic extracellular pH induces autophagy to promote anoikis resistance of hepatocellular carcinoma cells via downregulation of miR-3663-3p

Metastasis is the major reason for poor prognosis and high fatality in hepatocellular carcinoma (HCC). Due to the “Warburg effect”, an acidic tumor microenvironment (TME) exists in solid tumors and plays a critical role in cancer metastasis. Thus, clarifying the mechanism underlying the acidic TME in tumor metastasis could facilitate the development of new therapeutic strategies for HCC. Anoikis resistance is one of the most important events in the early stage of cancer metastasis. Here, we report that acidic extracellular pH (pH_e) promotes autophagy of HCC cells via the AMPK/mTOR pathway. We found that autophagy induced by acidity enhances anoikis resistance of HCC cells, which could be reversed by autophagy inhibitors. Furthermore, miR-3663-3p was downregulated by acidity, and overexpression of miR-3663-3p abolished acidic pH_e-induced autophagy and anoikis resistance. In summary, acidic pH_e enhances anoikis resistance of HCC cells by inducing autophagy, which is regulated by miR-3663-3p. Our findings provide new insight into how the acidic TME is involved in HCC progression.

Mechanisms for Modulating Anoikis Resistance in Cancer and the Relevance of Metabolic Reprogramming

The attachment of cells to the extracellular matrix (ECM) is the hallmark of structure–function stability and well-being. ECM detachment in localized tumors precedes abnormal dissemination of tumor cells culminating in metastasis. Programmed cell death (PCD) is activated during tumorigenesis to clear off ECM-detached cells through “anoikis.” However, cancer cells develop several mechanisms for abrogating anoikis, thus promoting their invasiveness and metastasis. Specific factors, such as growth proteins, pH, transcriptional signaling pathways, and oxidative stress, have been reported as drivers of anoikis resistance, thus enhancing cancer proliferation and metastasis. Recent studies highlighted the key contributions of metabolic pathways, enabling the cells to bypass anoikis. Therefore, understanding the mechanisms driving anoikis resistance could help to counteract tumor progression and prevent metastasis. This review elucidates the dynamics employed by cancer cells to impede anoikis, thus promoting proliferation, invasion, and metastasis. In addition, the authors have discussed other metabolic intermediates (especially amino acids and nucleotides) that are less explored, which could be crucial for anoikis resistance and metastasis.

Prominent Role of Histone Modifications in the Regulation of Tumor Metastasis

Tumor aggressiveness and progression is highly dependent on the process of metastasis, regulated by the coordinated interplay of genetic and epigenetic mechanisms. Metastasis involves several steps of epithelial to mesenchymal transition (EMT), anoikis resistance, intra- and extravasation, and new tissue colonization. EMT is considered as the most critical process allowing cancer cells to switch their epithelial characteristics and acquire mesenchymal properties. Emerging evidence demonstrates that epigenetics mechanisms, DNA methylation, histone modifications, and non-coding RNAs participate in the widespread changes of gene expression that characterize the metastatic phenotype. At the chromatin level, active and repressive histone post-translational modifications (PTM) in association with pleiotropic transcription factors regulate pivotal genes involved in the initiation of the EMT process as well as in intravasation and anoikis resistance, playing a central role in the progression of tumors. Herein, we discuss the main epigenetic mechanisms associated with the different steps of metastatic process, focusing in particular on the prominent role of histone modifications and the modifying enzymes that mediate transcriptional regulation of genes associated with tumor progression. We further discuss the development of novel treatment strategies targeting the reversibility of histone modifications and highlight their importance in the future of cancer therapy.

A Positive Feedback Loop Between TGFβ and Androgen Receptor Supports Triple-negative Breast Cancer Anoikis Resistance

Triple-negative breast cancer (TNBC) is an aggressive subtype with peak recurrence as metastatic disease within the first few years of diagnosis. Androgen receptor (AR) expression is increased in anchorage-independent cells in TNBC preclinical models. Both AR knockdown and inhibition lead to reduced TNBC invasion in vitro, reduced tumorigenicity, and less recurrence in vivo in preclinical models. Transforming growth factor β (TGFβ) pathway gene signatures also increased during anchorage-independent survival both in vitro and in vivo in preclinical models and in circulating tumor cells (CTCs) from patients during emergence of chemo resistant disease. We hypothesized that a positive loop between AR and TGFβ signaling facilitates TNBC anchorage-independent survival. We find that multiple components of the TGFβ pathway, including TGFβ1 and 3, as well as pathway activity measured by nuclear localization and transcriptional activity of phosphorylated Smad3, are enhanced in anchorage-independent conditions. Further, exogenous TGFβ increased AR protein while TGFβ inhibition decreased AR and TNBC viability, particularly under anchorage-independent culture conditions. ChIP-seq experiments revealed AR binding to TGFB1 and SMAD3 regulatory regions in MDA-MB-453 cells. In clinical datasets, TGFB3 and AR positively correlate and high expression of both genes together corresponded to significantly worse recurrence-free and overall survival in both ER-negative and basal-like breast cancer. Finally, inhibiting both AR and TGFβ decreased cell survival, particularly under anchorage-independent conditions. These findings warrant further investigations into whether combined inhibition of AR and TGFβ pathways might decrease metastatic recurrence rates and mortality from TNBC.

Long Non-Coding RNA MAPK8IP1P2 Inhibits Lymphatic Metastasis of Thyroid Cancer by Activating Hippo Signaling via Sponging miR-146b-3p

The principal issue derived from thyroid cancer is its high propensity to metastasize to the lymph node. Aberrant exprssion of long non-coding RNAs have been extensively reported to be significantly correlated with lymphatic metastasis of thyroid cancer. However, the clinical significance and functional role of lncRNA-MAPK8IP1P2 in lymphatic metastasis of thyroid cancer remain unclear. Here, we reported that MAPK8IP1P2 was downregulated in thyroid cancer tissues with lymphatic metastasis. Upregulating MAPK8IP1P2 inhibited, while silencing MAPK8IP1P2 enhanced anoikis resistance in vitro and lymphatic metastasis of thyroid cancer cells in vivo. Mechanistically, MAPK8IP1P2 activated Hippo signaling by sponging miR-146b-3p to disrupt the inhibitory effect of miR-146b-3p on NF2, RASSF1, and RASSF5 expression, which further inhibited anoikis resistance and lymphatic metastasis in thyroid cancer. Importantly, miR-146b-3p mimics reversed the inhibitory effect of MAPK8IP1P2 overexpression on anoikis resistance of thyroid cancer cells. In conclusion, our findings suggest that MAPK8IP1P2 may serve as a potential biomarker to predict lymphatic metastasis in thyroid cancer, or a potential therapeutic target in lymphatic metastatic thyroid cancer.

The 14-3-3σ protein promotes HCC anoikis resistance by inhibiting EGFR degradation and thereby activating the EGFR-dependent ERK1/2 signaling pathway

Resistance to anoikis, cell death due to matrix detachment, is acquired during tumor progression. The 14-3-3σ protein is implicated in the development of chemo- and radiation resistance, indicating a poor prognosis in multiple human cancers. However, its function in anoikis resistance and metastasis in hepatocellular carcinoma (HCC) is currently unknown.

Methods: Protein expression levels of 14-3-3σ were measured in paired HCC and normal tissue samples using western blot and immunohistochemical (IHC) staining. Statistical analysis was performed to evaluate the clinical correlation between 14-3-3σ expression, clinicopathological features, and overall survival. Artificial modulation of 14-3-3σ (downregulation and overexpression) was performed to explore the role of 14-3-3σ in HCC anoikis resistance and tumor metastasis in vitro and in vivo. Association of 14-3-3σ with epidermal growth factor receptor (EGFR) was assayed by co-immunoprecipitation. Effects of ectopic 14-3-3σ expression or knockdown on EGFR signaling, ligand-induced EGFR degradation and ubiquitination were examined using immunoblotting and co-immunoprecipitation, immunofluorescence staining, and flow cytometry analysis. The levels of EGFR ubiquitination, the interaction between EGFR and 14-3-3σ, and the association of EGFR with c-Cbl after EGF stimulation, in 14-3-3σ overexpressing or knockdown cells were examined to elucidate the mechanism by which 14-3-3σ inhibits EGFR degradation. Using gain-of-function or loss-of-function strategies, we further investigated the role of the EGFR signaling pathway and its downstream target machinery in 14-3-3σ-mediated anoikis resistance of HCC cells.

Results: We demonstrated that 14-3-3σ was upregulated in HCC tissues, whereby its overexpression was correlated with aggressive clinicopathological features and a poor prognosis. In vitro and in vivo experiments indicated that 14-3-3σ promoted anoikis resistance and metastasis of HCC cells. Mechanistically, we show that 14-3-3σ can interact with EGFR and significantly inhibit EGF-induced degradation of EGFR, stabilizing the activated receptor, and therefore prolong the activation of EGFR signaling. We demonstrated that 14-3-3σ downregulated ligand-induced EGFR degradation by inhibiting EGFR-c-Cbl association and subsequent c-Cbl-mediated EGFR ubiquitination. We further verified that activation of the ERK1/2 pathway was responsible for 14-3-3σ-mediated anoikis resistance of HCC cells. Moreover, EGFR inactivation could reverse the 14-3-3σ-mediated effects on ERK1/2 phosphorylation and anoikis resistance. Expression of 14-3-3σ and EGFR were found to be positively correlated in human HCC tissues.

Conclusions: Our results indicate that 14-3-3σ plays a pivotal role in the anoikis resistance and metastasis of HCC cells, presumably by inhibiting EGFR degradation and regulating the activation of the EGFR-dependent ERK1/2 pathway. To our best knowledge, this is the first report of the role of 14-3-3σ in the anoikis resistance of HCC cells, offering new research directions for the treatment of metastatic cancer by targeting 14-3-3σ.

YAP activation in melanoma contributes to anoikis resistance and metastasis

Melanoma is inherently heterogeneous, providing resistance to apoptosis. Anoikis resistance is a hallmark feature of metastatic melanoma to escape apoptosis when cells lose contact with adjacent cells or extracellular matrix. The yes-associated protein transcription co-activator is the effector of Hippo pathway. Herein, we investigated the function of yes-associated protein in anoikis resistance of melanoma cells. When melanoma cells were grown under anchorage-independent condition, anoikis-resistant cells displayed higher levels of yes-associated protein activation than the cells that were attached to the basement membrane, as evidenced by downregulated phosphorylated yes-associated protein at Ser127 and higher expression of downstream genes BCL2 and MCL-1. Yes-associated protein overexpression directly enhanced the anoikis resistance and metastatic potential of melanoma cells. Conversely, yes-associated protein inhibitor CA3 exhibited Dose-dependent induction of anoikis in resistant melanoma cells and exerted great inhibition on cell migration. Knockdown of yes-associated protein expression by shRNA also rendered melanoma cells susceptible to anoikis and interrupted cell invasiveness. Yes-associated protein inhibition in anoikis-resistant cells also reduced the number of metastatic nodules in the lung sections of SCID mice. Clinically, higher yes-associated protein level in the lung metastasis tissues correlated with higher BCL2 and MCL1 expressions compared with the non-metastasis tissues. Overall, our finding suggests that the aberrant activation of yes-associated protein exerts important role on anoikis resistance and metastatic capability of melanoma cells.

The inhibitory effect of microRNA-1827 on anoikis resistance in lung adenocarcinoma A549 cells via targeting caveolin-1

Anoikis resistance is a critical process for cancer cell metastasis in non-small cell lung cancer (NSCLC), and microRNA-1827 (miR-1827) is closely correlated with NSCLC metastasis. In this study, we aimed to evaluate the role of miR-1827 in regulating the anoikis resistance of NSCLC. The results showed that miR-1827 level was decreased in tumor tissues and cells and was correlated with tumor grade and lymph node (LN) metastasis. Overexpression of miR-1827 inhibited anchorage-independent growth and anoikis resistance in A549 cells. Bioinformatics and functional analysis identified that caveolin-1 (CAV-1) is directly targeted by miR-1827. Restoration of CAV-1 significantly attenuated miR-1827's effect on anoikis resistance in A549 cells. Our data identified a novel signaling axis of miR-1827/CAV-1 in regulating anoikis resistance, which might serve as a potential therapeutic target for metastatic NSCLC.

Targeting Fatty Acid Oxidation to Promote Anoikis and Inhibit Ovarian Cancer Progression

Epithelial-derived high-grade serous ovarian cancer (HGSOC) is the deadliest gynecologic malignancy. Roughly 80% of patients are diagnosed with late-stage disease, which is defined by wide-spread cancer dissemination throughout the pelvic and peritoneal cavities. HGSOC dissemination is dependent on tumor cells acquiring the ability to resist anoikis (apoptosis triggered by cell detachment). Epithelial cell detachment from the underlying basement membrane or extracellular matrix leads to cellular stress, including nutrient deprivation. In this report, we examined the contribution of fatty acid oxidation (FAO) in supporting anoikis resistance. We examined expression Carnitine Palmitoyltransferase 1A (CPT1A) in a panel of HGSOC cell lines cultured in adherent and suspension conditions. With CPT1A knockdown cells, we evaluated anoikis by caspase 3/7 activity, cleaved caspase 3 immunofluorescence, flow cytometry, and colony formation. We assessed CPT1A-dependent mitochondrial activity and tested the effect of exogenous oleic acid on anoikis and mitochondrial activity. In a patient-derived xenograft model, we administered etomoxir, an FAO inhibitor, and/or platinum-based chemotherapy. CPT1A is overexpressed in HGSOC, correlates with poor overall survival, and is upregulated in HGSOC cells cultured in suspension. CPT1A knockdown promoted anoikis and reduced viability of cells cultured in suspension. HGSOC cells in suspension culture are dependent on CPT1A for mitochondrial activity. In a patient-derived xenograft model of HGSOC, etomoxir significantly inhibited tumor progression. IMPLICATIONS: Targeting FAO in HGSOC to promote anoikis and attenuate dissemination is a potential approach to promote a more durable antitumor response and improve patient outcomes.

Nuclear MYH9-induced CTNNB1 transcription, targeted by staurosporin, promotes gastric cancer cell anoikis resistance and metastasis

Rationale: Peritoneal metastasis predicts poor prognosis of gastric cancer (GC) patients, and the underlying mechanisms are poorly understood. Methods: The 2-DIGE, MALDI-TOF/TOF MS and single-cell transcriptome were used to detect differentially expressed proteins among normal gastric mucosa, primary GC and peritoneal metastatic tissues. Lentiviruses carrying shRNA and transcription activator-like effector nuclease technology were used to knock down myosin heavy chain 9 (MYH9) expression in GC cell lines. Immunofluorescence, immune transmission electron microscopy, chromatin fractionation, co-immunoprecipitation, and assays for chromatin immunoprecipitation, dual luciferase reporter, agarose-oligonucleotide pull-down, flow cytometry and cell anoikis were performed to uncover nuclear MYH9-induced β-catenin (CTNNB1) transcription in vitro. Nude mice and conditional transgenic mice were used to investigate the findings in vivo. Results: We observed that MYH9 was upregulated in metastatic GC tissues and was associated with a poor prognosis of GC patients. Mechanistically, we confirmed that MYH9 was mainly localized in the GC cell nuclei by four potential nuclear localization signals. Nuclear MYH9 bound to the CTNNB1 promoter through its DNA-binding domain, and interacted with myosin light chain 9, β-actin and RNA polymerase II to promote CTNNB1 transcription, which conferred resistance to anoikis in GC cells in vitro and in vivo. Staurosporine reduced nuclear MYH9 S1943 phosphorylation to inhibit CTNNB1 transcription, Wnt/β-catenin signaling activation and GC progression in both orthotropic xenograft GC nude mouse and transgenic GC mouse models. Conclusion: This study identified that nuclear MYH9-induced CTNNB1 expression promotes GC metastasis, which could be inhibited by staurosporine, indicating a novel therapy for GC peritoneal metastasis.

Activation of BDNF/TrkB pathway promotes prostate cancer progression via induction of epithelial-mesenchymal transition and anoikis resistance

Prostate cancer (PCa) is one of the most common malignant diseases in male worldwide, yet, the molecular mechanisms involved in PCa progression are still poorly understood. This study aimed to investigate the roles of the brain-derived neurotrophic factor/tropomyosin receptor kinase B (BDNF/TrkB) pathway in PCa progression. It was demonstrated by immunohistochemical analysis that both BDNF and TrkB were overexpressed in PCa tissues and elevated TrkB expression was tightly related with lymph node metastasis and advanced stage of PCa. In vitro studies showed that stimulation with rhBDNF or overexpression of TrkB in PCa cells promoted cell migration, invasion, and anoikis resistance. Overexpression of TrkB also resulted in epithelial-mesenchymal transition (EMT)-like transformation in cell morphology, whereas RNA interference-mediated TrkB depletion caused reversion of EMT. Further investigation demonstrated that protein kinase B (AKT) was responsible for BDNF/TrkB signaling-induced pro-migratory and pro-invasive effects, EMT, and anoikis resistance. Finally, in vivo studies confirmed that enhanced TrkB expression facilitated tumor growth, whereas downregulation of TrkB suppressed tumor growth. Our findings illustrate that BDNF/TrkB pathway is crucial for PCa progression, which may provide a novel therapeutic strategy for the treatment of advanced PCa.

Putative anoikis-resistant subpopulations in colorectal carcinoma: a marker of adverse prognosis

Anoikis is a form of apoptosis induced when a cell loses contact with the extracellular matrix (ECM). Anoikis resistance is essential for metastasis formation, yet only detectable by in vitro experiments. We present a method for quantitation of putative anoikis-resistant (AR) subpopulations in colorectal carcinoma (CRC) and evaluate their prognostic significance. We studied 137 CRC cases and identified cell subpopulations with and without stromal or extracellular matrix (ECM) contact with hematoxylin-and-eosin-stained sections and immunohistochemistry for laminin and type IV collagen. Suprabasal cells of micropapillary structures and inner cells of cribriform and solid structures lacked both stromal contact and contact with ECM proteins. Apoptosis rate (M30) was lower in these subpopulations than in the other carcinoma cells, consistent with putative AR subpopulation. We determined the areal density of these subpopulations (number/mm² tumor tissue), and their high areal density independently indicates low cancer-specific survival. In conclusion, we show evidence that subpopulations of carcinoma cells in micropapillary, cribriform, and solid structures are resistant to anoikis as shown by lack of ECM contact and low apoptosis rate. Abundance of these subpopulations is a new independent indicator of poor prognosis in CRC, consistent with the importance of anoikis resistance in the formation of metastasis.

SPIB promotes anoikis resistance via elevated autolysosomal process in lung cancer cells

Anoikis (detachment-induced cell death) is a specific type of programmed cell death which occurs in response to the loss of the correct extracellular matrix connections. Anoikis resistance is an important mechanism in cancer invasiveness and metastatic behavior. Autophagy, on the other hand, involves the degradation of damaged organelles and the recycling of misfolded proteins and intracellular components. However, the intersection of these two cellular responses in lung cancer cells has not been extensively studied. Here, we identified that upon matrix deprivation, the lymphocyte lineage-specific Ets transcription factor SPIB was activated and directly enhanced SNAP47 transcription in certain lung cancer cells. Loss of attachment-induced autophagy significantly increased anoikis resistance by SPIB activation. Consistent with this function, SPIB depletion by short hairpin RNA abrogated SNAP47 transcriptional activation upon matrix deprivation. Therefore, these data delineate an important role of SPIB in autophagy-mediated anoikis resistance in lung cancer cells. Accordingly, these findings suggest that manipulating SPIB-regulated pathways in vivo and evaluating the impact of anoikis resistance warrant further investigation. DATABASE: RNA sequencing and ChIP sequencing data are available in Gene Expression Omnibus database under the accession numbers GSE106592 and GSE125561, respectively.

miR-424-5p Promotes Anoikis Resistance and Lung Metastasis by Inactivating Hippo Signaling in Thyroid Cancer

miR-424-5p has been widely identified to function as an oncomiR in multiple human cancer types. However, the biological function of miR-424-5p in distant metastasis of thyroid cancer, as well as the underlying mechanism, remains not clarified yet. In the current study, miR-424-5p expression was elucidated in 10 paired fresh thyroid cancer tissues and the thyroid cancer dataset from The Cancer Genome Atlas (TCGA). Lung metastasis colonization models in vivo and functional assays in vitro were used to determine the role of miR-424-5p in thyroid cancer. Bioinformatics analysis, western blot, luciferase reporter, and immunofluorescence assays were applied to identify the potential targets and underlying mechanism involved in the functional role of miR-424-5p in lung metastasis of thyroid cancer. Here, we reported that miR-424-5p was upregulated in thyroid cancer, and overexpression of miR-424-5p significantly correlated with distant metastasis of thyroid cancer. Upregulating miR-424-5p promoted, whereas silencing miR-424-5p inhibited, anoikis resistance in vitro and lung metastasis in vivo. Mechanistic investigation further revealed that miR-424-5p promoted anoikis resistance and lung metastasis by inactivating Hippo signaling via simultaneously targeting WWC1, SAV1, and LAST2. Therefore, our results support the idea that miR-424-5p may serve as a potential therapeutic target in lung metastasis of thyroid cancer.

MicroRNA-363-3p suppresses anoikis resistance in human papillary thyroid carcinoma via targeting integrin alpha 6

MicroRNAs are highly conserved endogenous small noncoding RNAs and demonstrated to play important roles in the metastatic cascade of papillary thyroid carcinoma (PTC), including the process of anoikis resistance. In this study, the correlation between miRNA-363-3p (miR-363-3p) expression and PTC metastasis was analyzed based on clinical data, and the effect and related mechanism of miR-363-3p on anoikis resistance in B-CPAP cells were further investigated. First, miR-363-3p was found to be down-regulated in PTC tissue, which was correlated with the advanced clinical stage and lymph node (LN) metastasis. Then, functional study revealed that miR-363-3p was also down-regulated in B-CPAP cells compared with that in thyroid epithelial Nthy-ori3-1 cells, and miR-363-3p transfection could suppress anoikis resistance of B-CPAP cells. Finally, integrin alpha 6 (ITGA6) was validated as the target gene of miR-363-3p, and restoration of ITGA6 expression attenuated miR-363-3p's inhibitory effect on anoikis resistance in B-CPAP cells. These findings contribute to understand the role of miR-363-3p in the metastatic cascade of PTC and suggest the potential clinical value of miR-363-3p for the prevention of PTC metastasis.

Stimulation with Porphyromonas gingivalis enhances malignancy and initiates anoikis resistance in immortalized oral keratinocytes

The aim of this study was to get new insights into molecular processes involved in tumor propagation of immortalized oral keratinocytes induced by the keystone pathogen Porphyromonas gingivalis. Cell culture experiments with immortalized OKF6 cells were performed to analyze cellular effects caused by bacterial stimulation focusing on altered gene expression, signaling pathways, proliferation rate, cell viability, migration and invasion behavior, and on the development of antiapoptotic pathways. Gene and protein expression were analyzed using real-time polymerase chain reaction, enzyme-linked immunosorbent assay, western blot, and protein arrays. Trypan blue staining was used to analyze proliferation and viability, transwell assays for cellular migration, Matrigel assays for invasion, and anoikis-assays for evaluating anoikis resistance. Stimulation of OKF6 cells with Porphyromonas gingivalis led to an alteration in the molecular repertoire of proteins which are involved in cell proliferation, epithelial-mesenchymal transition, stem cell formation, migration, invasion, and anoikis resistance. Higher proliferation rates were detected in conjunction with an activation of PI3K/Akt signaling and the mTOR-pathway. Additionally, inhibition of glycogen-synthase-kinase3-β led to stabilization of β-catenin and Snail, which resulted in a switch from predominant E-cadherin to N-cadherin expression and increased expression of the stem cell markers Oct3/4, Sox2, and Nanog. Enhanced biosynthesis and enzyme activity of matrix metalloproteinase-9 was accompanied by elevated invasion behavior. Finally, anoikis resistance was detected in stimulated keratinocytes by decreased apoptosis of nonadherent cells and elevated expression of epidermal growth factor receptor and c-Met. Hence, Porphyromonas gingivalis is able to induce a more aggressive tumor-like phenotype in immortalized oral keratinocytes, thus contributing to enhanced tumor features.

Tumor Susceptibility Gene 101 Mediates Anoikis Resistance of Metastatic Thyroid Cancer Cells

BACKGROUND/AIM

Resistance to anoikis is a pre-requisite step in metastasis, a major cause of death in patients with cancer, including thyroid cancer. Impairing anoikis resistance is a possible strategy for therapy of metastatic cancer. We, therefore, we aimed to investigate the key players of anoikis resistance.

MATERIALS AND METHODS

Papillary-type (BCPAP), follicular-type (FTC133), and anaplastic-type (ARO) thyroid carcinoma cells, cultured in poly(2-hydroxyethyl methacrylate)-coated plates to mimic circulating cells, were used as model systems in this study. Flow cytometry and soft-agar assays were used to determine cells exhibiting anoikis resistance. Proteomics was used to identify candidate proteins and validated using western blot and siRNA knockdown.

RESULTS

Only ARO cells showed both anoikis resistance potential and anchorage-independent growth ability. Tumor susceptibility gene 101 protein (TSG101) was identified to be potentially important in anoikis resistance, which was confirmed by an increase in anoikis and expression of a pro-apoptotic protein (BCL-2 like protein 4) and an apoptotic marker (cleaved poly-ADP ribose polymerase) in floating siTSG101-knockdown cells.

CONCLUSION

To our knowledge, this is the first study that implicates the importance of TSG101 in anoikis resistance of thyroid cancer.

Stromal-induced downregulation of miR-1247 promotes prostate cancer malignancy

Cancer progression is strictly dependent on the relationship between tumor cells and the surrounding stroma, which supports cancer malignancy promoting several crucial steps of tumor progression, including the execution of the epithelial to mesenchymal transition (EMT) associated with enhancement in cell invasion, resistance to both anoikis and chemotherapeutic treatments. Recently it has been highlighted the central role of microRNAs (miRNAs) as regulators of tumor progression. Notably, in several tumors a strong deregulation of miRNAs is observed, supporting proliferation, invasion, and metabolic reprogramming of tumor cells. Here we demonstrated that cancer-associated fibroblasts induce a downregulation of miR-1247 in prostate cancer (PCa) cells. We proved that miR-1247 repression is functional for the achievement of EMT and increased cell invasion as well as stemness traits. These phenomena contribute to promote the metastatic potential of PCa cells as demonstrated by increased lung colonization in in vivo experiments. Moreover, as a consequence of miR-1247 downregulation, we observed a correlated increased expression level of neuropilin-1, a miR-1247 target involved as a coreceptor in the epidermal growth factor receptor signaling. Taken together, our data highlight miR-1247 as a potential target for molecular therapies aimed to block the progression and diffusion of PCa.

Adipocytes fuel gastric cancer omental metastasis via PITPNC1-mediated fatty acid metabolic reprogramming

Omental metastasis occurs frequently in gastric cancer (GC) and is considered one of the major causes of gastric cancer-related mortality. Recent research indicated that omental adipocytes might mediate this metastatic predilection. Phosphatidylinositol transfer protein, cytoplasmic 1 (PITPNC1) was identified to have a crucial role in metastasis. However, whether PITPNC1 participates in the interaction between adipocytes and GC omental metastasis is unclear. Methods: We profiled and analyzed the expression of PITPNC1 through analysis of the TCGA database as well as immunohistochemistry staining using matched GC tissues, adjacent normal gastric mucosa tissues (ANTs), and omental metastatic tissues. The regulation of PITPNC1 by adipocytes was explored by co-culture systems. By using both PITPNC1 overexpression and silencing methods, the role of PITPNC1 in anoikis resistance and metastasis was determined through in vitro and in vivo experiments. Results: PITPNC1 was expressed at higher rates in GC tissues than in ANTs; notably, it was higher in omental metastatic lesions. Elevated expression of PITPNC1 predicted higher rates of omental metastasis and a poor prognosis. PITPNC1 promoted anoikis resistance through fatty acid metabolism by upregulating CD36 and CPT1B expression. Further, PITPNC1 was elevated by adipocytes and facilitated GC omental metastasis. Lastly, in vivo studies showed that PITPNC1 was a therapeutic indicator of fatty acid oxidation (FAO) inhibition. Conclusion: Elevated expression of PITPNC1 in GC is correlated with an advanced clinical stage and a poor prognosis. PITPNC1 promotes anoikis resistance through enhanced FAO, which is regulated by omental adipocytes and consequently facilitates GC omental metastasis. Targeting PITPNC1 might present a promising strategy to treat omental metastasis.

Shear stress promotes anoikis resistance of cancer cells via caveolin-1-dependent extrinsic and intrinsic apoptotic pathways

Circulating tumor cells (CTCs) need to acquire resistance to anoikis to survive after they experience fluid shear stress in the circulatory and lymphatic systems. However, the mechanism by which tumor cells resist anoikis under shear stress conditions remains unknown. Here, we found that the application of low shear stress (LSS; 2 dyn/cm² ) to human breast carcinoma cells (MDA-MB-231) resulted in increased anoikis resistance when tumor cells were grown under anchorage-independent conditions. Caveolin-1 (Cav-1), the major component of plasma membrane caveolae, was overexpressed in LSS-treated cells and prevented tumor cells from anoikis, while depletion of Cav-1 restored sensitivity to anoikis. LSS-induced dissociation of Cav-1-Fas inhibited formation of the death-inducing signaling complex, caspase-8 activation, and rendered tumor cells resistant to anoikis. Likewise, LSS blocked the mitochondrial pathway through promotion of integrin β1-focal adhesion kinase-mediated multicellular aggregation and suppression of truncated BID translocation mediated crosstalk between the extrinsic and intrinsic apoptotic pathways. Our findings provide insights into the mechanisms by which LSS induces anoikis resistance in breast carcinoma cells through inhibition of Cav-1-dependent extrinsic and intrinsic apoptotic pathways, and serves as a potential therapeutic target for CTCs and metastatic breast cancer.

Caveolin-1 contributes to anoikis resistance in human gastric cancer SGC-7901 cells via regulating Src-dependent EGFR-ITGB1 signaling

Anoikis resistance is considered to be an essential prerequisite of tumor metastasis and which is an important mechanism in the metastatic process of gastric cancer (GC). Caveolin-1 (CAV-1), a protein component of caveolae, has been reported to regulate several cancer cell behaviors including anoikis resistance. However, the role of CAV-1 in the acquisition of anoikis resistance in GC cells has never been explored. In this study, we investigated the promoting effect of CAV-1 on anchorage-independent growth and anoikis resistance, and the involvement of the related signaling pathways in such process in SGC-7901 cells. The results showed that CAV-1 could promote anchorage-independent growth and anoikis resistance in detached SGC-7901 cells, which was associated with the activation of Src-dependent epidermal growth factor receptor-integrin β signaling as well as the phosphorylation of PI3K/Akt and MEK/ERK signaling pathways. The data from this study might contribute to the in-depth understanding of the metastatic mechanism for GC.

Development and evaluation of a CEACAM6-targeting theranostic nanomedicine for photoacoustic-based diagnosis and chemotherapy of metastatic cancer

Metastasis is the leading cause of cancer-related deaths. A number of chemotherapeutic and early diagnosis strategies, including nanomedicine, have been developed to target metastatic tumor cells. However, simultaneous inhibition and imaging of metastasis is yet to be fully achieved. Methods: To overcome this limitation, we have developed human serum albumin-based nanoparticles (tHSA-NPs) with photoacoustic imaging capability, which target carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6). CEACAM6 is highly expressed in metastatic anoikis-resistant tumor cells. Results:In vitro, the CEACAM6-targeting tHSA-NPs efficiently targeted CEACAM6-overexpressing metastatic anoikis-resistant tumor cells. In vivo, CEACAM6-targeting tHSA-NPs administered intravenously to BALB/c nude mice efficiently inhibited lung metastasis in circulating anoikis-resistant tumor cells compared to the controls. In addition, anoikis-resistant tumor cells can be successfully detected by photoacoustic imaging, both in vitro and in vivo, using the intrinsic indocyanine green-binding affinity of albumin. Conclusion: In summary, the CEACAM6-targeting albumin-based nanoparticles allowed the delivery of drugs and photoacoustic imaging to metastatic anoikis-resistant tumor cells in vitro and in vivo. Based on the expression of CEACAM6 in a variety of tumors, CEACAM6-targeting nanomedicine might be used to target various types of metastatic tumor cells.

Micropapillary Structures in Colorectal Cancer: An Anoikis-resistant Subpopulation

BACKGROUND/AIM

Micropapillary structures (MIPs) are focal piles of columnar cells without extracellular matrix contact, and common in serrated colorectal carcinoma (CRC). In order to characterize biology of MIPs in colorectal cancer (CRC), the proliferation and apoptosis rates, and survivin expression were compared between MIPs and other cancer epithelial cells of CRC (non-MIPs).

MATERIALS AND METHODS

We assessed 46 samples of normal colorectal mucosa, 62 carcinomas and 54 polyps for proliferation (Ki67), apoptosis (M30), and survivin expression by immunohistochemistry.

RESULTS

MIPs in carcinoma showed lower rates of proliferation and apoptosis than non-MIPs. A low rate of apotosis in MIPs was associated with poor prognosis in local carcinoma. In normal crypts, nuclear-to-cytoplasmic transition of survivin indicated epithelial cell maturation. Cancer cases showed increased cytoplasmic expression of survivin than normal mucosa and polyps. However, MIPs showed lower nuclear and cytoplasmic survivin expression than non-MIPs. Our findings suggest that MIPs represent a biologically distinct subpopulation of carcinoma cells with features of anoikis resistance and possibly quiescence.

MDA-9/Syntenin regulates protective autophagy in anoikis-resistant glioma stem cells

Glioma stem cells (GSCs) comprise a small subpopulation of glioblastoma multiforme cells that contribute to therapy resistance, poor prognosis, and tumor recurrence. Protective autophagy promotes resistance of GSCs to anoikis, a form of programmed cell death occurring when anchorage-dependent cells detach from the extracellular matrix. In nonadherent conditions, GSCs display protective autophagy and anoikis-resistance, which correlates with expression of melanoma differentiation associated gene-9/Syntenin (MDA-9) (syndecan binding protein; SDCBP). When MDA-9 is suppressed, GSCs undergo autophagic death supporting the hypothesis that MDA-9 regulates protective autophagy in GSCs under anoikis conditions. MDA-9 maintains protective autophagy through phosphorylation of BCL2 and by suppressing high levels of autophagy through EGFR signaling. MDA-9 promotes these changes by modifying FAK and PKC signaling. Gain-of-function and loss-of-function genetic approaches demonstrate that MDA-9 regulates pEGFR and pBCL2 expression through FAK and pPKC. EGFR signaling inhibits autophagy markers (ATG5, Lamp1, LC3B), helping to maintain protective autophagy, and along with pBCL2 maintain survival of GSCs. In the absence of MDA-9, this protective mechanism is deregulated; EGFR no longer maintains protective autophagy, leading to highly elevated and sustained levels of autophagy and consequently decreased cell survival. In addition, pBCL2 is down-regulated in the absence of MDA-9, leading to cell death in GSCs under conditions of anoikis. Our studies confirm a functional link between MDA-9 expression and protective autophagy in GSCs and show that inhibition of MDA-9 reverses protective autophagy and induces anoikis and cell death in GSCs.

MiR-21 Suppresses Anoikis through Targeting PDCD4 and PTEN in Human Esophageal Adenocarcinoma

Anoikis is a form of apoptosis induced upon cell detachment from extracellular matrix. It has been determined that acquisition of resistance to anoikis is a critical step for tumor cell metastasis. MiR-21, the most prominent oncomiR, plays an important role in tumor progression. In this study, we revealed that up-regulation of miR-21 in human esophageal adenocarcinoma (EA) is associated with lymph node metastasis and poor survival rate. Because of the established anti-apoptosis effect of miR-21, it is tempting to speculate that miR-21 might contribute to tumor metastasis by regulating anoikis. qRT-PCR analysis demonstrated that miR-21 expression in OE33/AR cells (subpopulation of human EA OE33 cells that acquired resistance to anoikis) was significantly increased. Also, transfection of miR-21 mimics provided OE33 cells resisting to anoikis. By luciferase assays, we verified that PDCD4 and PTEN were the functional targets of miR-21. In mouse model, via tail vein injection experiment, we showed that the metastasis formation of OE33 cells in vivo could be mediated by changing the miR-21 expression pattern. Taken together, our findings suggested that miR-21 was involved in the regulation of anoikis in human EA cells. Targeting miR-21 may provide a novel strategy to prevent metastasis.

14-3-3σ downregulation suppresses ICC metastasis via impairing migration, invasion, and anoikis resistance of ICC cells

BACKGROUND

14-3-3σ protein plays an important role in multiple cellular processes. The role of 14-3-3σ in the progression of intrahepatic cholangiocarcinoma (ICC) has not been well understood.

OBJECTIVE

We performed this research to explore the relationship between 14-3-3σ level and clinical characteristics and prognosis of ICC patients. Besides, we used ICC cell lines HCCC-9810 and RBE to assess the biological function of 14-3-3σ.

METHODS

We examined 14-3-3σ expression in 28 ICC tissues and matched paratumor tissues by quantitative real-time PCR and immunohistochemistry. Additionally, ICC tissue array from 100 patients and normal liver tissue array from 24 healthy people were also analyzed by immunohistochemistry. 14-3-3σ was knocked down in ICC cell lines and the functions and mechanisms of 14-3-3σ were assessed.

RESULTS

14-3-3σ is highly expressed in ICC tissues and high expression of 14-3-3σ correlates poor overall survival in ICC patients. Knocking down of 14-3-3σ in ICC cell lines reduced cells migration, invasion and anoikis resistance. Furthermore, 14-3-3σ-silenced ICC cells showed significantly decreased invasion-related protein MMP2 and MMP9 expression.

CONCLUSIONS

Our results demonstrate prognostic value of 14-3-3σ and its role in metastasis, which is associated with ICC cell lines migration, invasion and anoikis resistance.

Midkine promotes hepatocellular carcinoma metastasis by elevating anoikis resistance of circulating tumor cells

Midkine is overexpressed in hepatocellular carcinoma (HCC) and plays a role in tumor progression, but less is known about its role in resistance of circulating tumor cells (CTCs) to anoikis which leading to recurrence and metastasis. The aim of the present study was to analyze whether midkine was associated with HCC progression with anoikis resistance. We found that cultured HCC cells were more resistant to anoikis, which paralleled midkine expression, and midkine treatment significantly inhibited anoikis in a dose-dependent manner. Furthermore, in in vitro and in vivo assays, knockdown of midkine resulted in significant sensitivity to anoikis, decreased cell survival and significantly decreased tumor occurrence rate. Patients with midkine-elevated HCC had higher CTC counts and less apoptotic CTCs, as well as significantly higher recurrence rate and shorter recurrence-free interval. To understand the molecular mechanism underlying the midkine with HCC progression, we performed in vitro and in vivo studies. We found that midkine plays an important role in enhancement of HCC cell resistance to anoikis, thereby promoting subsequent metastasis. Activation of PI3K/Akt/NF-κB/TrkB signaling by midkine-activated anaplastic lymphomakinase (ALK) is responsible for anoikis resistance.

Stable and high expression of Galectin-8 tightly controls metastatic progression of prostate cancer

Two decades ago, Galectin-8 was described as a prostate carcinoma biomarker since it is only expressed in the neoplastic prostate, but not in the healthy tissue. To date, no biological function has been attributed to Galectin-8 that could explain this differential expression. In this study we silenced Galectin-8 in two human prostate cancer cell lines, PC3 and IGR-CaP1, and designed a pre-clinical experimental model that allows monitoring the pathology from its early steps to the long-term metastatic stages. We show for the first time that the natural and conserved expression of Gal-8 in tumour cells is responsible for the metastatic evolution of prostate cancer. In fact, Gal-8 controls the rearrangement of the cytoskeleton and E-Cadherin expression, with a major impact on anoikis and homotypic aggregation of tumour cells, both being essential processes for the survival of circulating tumour cells during metastasis. While localized prostate cancer can be cured, metastatic and advanced disease remains a significant therapeutic challenge, urging for the identification of prognostic markers of the metastatic process. Collectively, our results highlight Galectin-8 as a potential target for anti-metastatic therapy against prostate cancer.

Suppression of ABHD2, identified through a functional genomics screen, causes anoikis resistance, chemoresistance and poor prognosis in ovarian cancer

Anoikis resistance is a hallmark of cancer, and relates to malignant phenotypes, including chemoresistance, cancer stem like phenotypes and dissemination. The aim of this study was to identify key factors contributing to anoikis resistance in ovarian cancer using a functional genomics screen. A library of 81 000 shRNAs targeting 15 000 genes was transduced into OVCA420 cells, followed by incubation in soft agar and colony selection. We found shRNAs directed to ABHD2, ELAC2 and CYB5R3 caused reproducible anoikis resistance. These three genes are deleted in many serous ovarian cancers according to The Cancer Genome Atlas data. Suppression of ABHD2 in OVCA420 cells increased phosphorylated p38 and ERK, platinum resistance, and side population cells (p<0.01, respectively). Conversely, overexpression of ABHD2 decreased resistance to anoikis (p<0.05) and the amount of phosphorylated p38 and ERK in OVCA420 and SKOV3 cells. In clinical serous ovarian cancer specimens, low expression of ABHD2 was associated with platinum resistance and poor prognosis (p<0.05, respectively). In conclusion, we found three novel genes relevant to anoikis resistance in ovarian cancer using a functional genomics screen. Suppression of ABHD2 may promote a malignant phenotype and poor prognosis for women with serous ovarian cancer.

The matricellular protein CYR61 promotes breast cancer lung metastasis by facilitating tumor cell extravasation and suppressing anoikis

Matricellular proteins play multiple roles in primary tumor growth, local invasion and tumor angiogenesis. However, their contribution to metastasis and the putative mechanisms involved are less well characterized. In ER-negative human breast cancer, elevated expression levels of the matricellular protein Cysteine-rich angiogenic inducer 61 (CYR61) are associated with more aggressive progression. Here, we investigated the role of CYR61 in breast cancer lung metastasis using the triple negative human breast cancer cell lines MDA-MB-231 and SUM159. Silencing of CYR61 significantly decreased lung metastasis from tumors orthotopically implanted in pre-irradiated or naive mammary tissue and upon tail vein injection. Constitutive CYR61 silencing impaired cancer cell extravasation to the lung during the first 24 hours after tail vein injection. In contrast, CYR61 inducible silencing starting 24 hours after cancer cell injection had no impact on lung metastasis formation. In vitro experiments revealed that CYR61 silencing decreased cancer cell transendothelial migration and motility, reduced CYR61 levels present at the cell surface and sensitized cancer cells to anoikis. Furthermore, we demonstrate that CYR61-dependent cell survival under non-adhesive conditions relied, at least partially, on β1 integrin ligation and AMPKα signaling while it was independent of AKT, FAK and ERK1/2 activation. Our data provide the first evidence that CYR61 promotes breast cancer lung metastasis by facilitating tumor cell extravasation and protecting from anoikis during initial seeding to the lung. The uncovered CYR61-β1 integrin-AMPKα axis may serve as a potential therapeutic target to prevent breast cancer metastasis to the lung.

MicroRNA-451 dictates the anoikis resistance of osteosarcoma by targeting Rab14

Cancer cells have developed anoikis resistance and thereby survive after detachment from their primary site and while traveling through the circulation. However, the mechanisms underlying resistance to anoikis in osteosarcoma (OS) remain largely unknown. MicroRNAs (miRNA) have been reported to contribute to malignant phenotypes of cancer cells. To investigate the roles of miRNAs in anoikis resistance of OS cells, the implications of 9 well-characterized miRNAs that dysregulated in OS on cell anoikis were screened. As a result, miR-451 was identified as a crucial factor involved in anoikis resistance and anchorage-independent growth of OS cell. MiR-451 was down-regulated in OS cells, re-expression of miR-451 significantly promoted cell anoikis of three OS cell lines and inhibition of miR-451 protected HOS cells from anoikis under anoikis condition. Subsequently, bioinformatics prediction and luciferase reporter assay indicated that Rab14 was a direct target of miR-451, and Rab14 could be down-regulated by miR-451 at both mRNA and protein levels. Genetic silencing of Rab14 recapitulated the role of miR-451 on anoikis resistance and restoration of Rab14 largely abrogated the tumor suppressor function of miR-451. Finally, overexpression of miR-451 remarkably suppressed the lung metastasis of OS cells. Collectively, our findings suggest that the miR-451/Rab14 axis might serve as a novel mechanism of resistance to anoikis in OS.

Timp1 Promotes Cell Survival by Activating the PDK1 Signaling Pathway in Melanoma

High TIMP1 expression is associated with poor prognosis in melanoma, where it can bind to CD63 and β1 integrin, inducing PI3-kinase pathway and cell survival. Phosphatidylinositol (3,4,5)-trisphosphate (PIP3), generated under phosphatidylinositol-3-kinase (PI3K) activation, enables the recruitment and activation of protein kinase B (PKB/AKT) and phosphoinositide-dependent kinase 1 (PDK1) at the membrane, resulting in the phosphorylation of a host of other proteins. Using a melanoma progression model, we evaluated the impact of Timp1 and AKT silencing, as well as PI3K, PDK1, and protein kinase C (PKC) inhibitors on aggressiveness characteristics. Timp1 downregulation resulted in decreased anoikis resistance, clonogenicity, dacarbazine resistance, and in vivo tumor growth and lung colonization. In metastatic cells, pAKT^Thr308 is highly expressed, contributing to anoikis resistance. We showed that PDK1^Ser241 and PKCβII^Ser660 are activated by Timp1 in different stages of melanoma progression, contributing to colony formation and anoikis resistance. Moreover, simultaneous inhibition of Timp1 and AKT in metastatic cells resulted in more effective anoikis inhibition. Our findings demonstrate that Timp1 promotes cell survival with the participation of PDK1 and PKC in melanoma. In addition, Timp1 and AKT act synergistically to confer anoikis resistance in advanced tumor stages. This study brings new insights about the mechanisms by which Timp1 promotes cell survival in melanoma, and points to novel perspectives for therapeutic approaches.

Renieramycin M Sensitizes Anoikis-resistant H460 Lung Cancer Cells to Anoikis

BACKGROUND/AIM

Anoikis resistance plays a crucial role in the promotion of survival of circulating tumor cells. This study aimed to evaluate the mechanistic pathways of anoikis resistance in human lung cancer cells and test the possible therapeutic effect of renieramycin M (RM) from the sponge Xestospongia sp. in conversion of anoikis resistance.

MATERIALS AND METHODS

Anoikis-resistant H460 (AR_H460) lung cancer cells in a detached condition were treated with RM at subtoxic concentrations for 24 h. Cell viability, cell morphology, and expression of the proteins involved in survival and apoptotic pathways were determined.

RESULTS

Anoikis resistance in H460 cells is mediated through the up-regulation of survival and anti-apoptotic proteins, namely phosphorylated extracellular signal-regulated kinase (p-ERK), phosphorylated ATP-dependent tyrosine kinase (p-AKT), B-cell lymphoma-2 (BCL2), and myeloid cell leukemia-1 (MCL1). RM significantly reduced cell viability and inhibited spontaneous aggregation of AR_H460 cells. Western blot analysis revealed that RM suppressed the levels of survival proteins p-ERK and p-AKT and anti-apoptotic proteins BCL2 and MCL1.

CONCLUSION

RM is a potential anti-metastatic agent by sensitizing anoikis-resistant lung cancer cells to anoikis by the suppression of anoikis-resistance mechanisms.

Emerging Role and Targeting of Carcinoembryonic Antigen-related Cell Adhesion Molecule 6 (CEACAM6) in Human Malignancies

Background: Carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) is a member of the CEA family of cell adhesion proteins that belong to the immunoglobulin superfamily. CEACAM6 is normally expressed on the surface of myeloid (CD66c) and epithelial surfaces. Stiochiomertic expression of members of the CEA family (CEACAM1, 5, 6, 7) on epithelia maintains normal tissue architecture through homo-and hetero-philic interactions. Dysregulated over-expression of CEACAM6 is oncogenic, is associated with anoikis resistance and an invasive phenotype mediated by excessive TGFβ, AKT, FAK and SRC signaling in human malignancies. Methods: Extensive literature review through PubMed was conducted to identify relevant preclinical and clinical research publications regarding CEACAM6 over the last decade and was summarized in this manuscript. Results: CEACAM5 and 6 are over-expressed in nearly 70% of epithelial malignancies including colorectal cancer (CRC), pancreatic ductal adenocarcinoma (PDA), hepatobiliary, gastric, breast, non-small cell lung and head/neck cancers. Importantly, CEACAM6 is a poor prognostic marker in CRC, while its expression correlates with tumor stage, metastasis and post-operative survival in PDA. CEACAM6 appears to be an immune checkpoint suppressor in hematologic malignancies including acute lymphoblastic leukemia and multiple myeloma. Several therapeutic monoclonal antibodies or antibody fragments targeting CEACAM6 have been designed and developed as a targeted therapy for human malignancies. A Llama antibody targeting CEACAM6 is being evaluated in early phase clinical trials. Conclusion: This review focuses on the role of CEACAM6 in the pathogenesis and signaling of the malignant phenotype in solid and hematologic malignancies and highlights its potential as a therapeutic target for anti-cancer therapy.

Upregulation of BNIP3 mediated by ERK/HIF-1α pathway induces autophagy and contributes to anoikis resistance of hepatocellular carcinoma cells

AIM

Acquisition of anoikis resistance is the hallmark of cancer and has been shown to be involved in metastasis of melignant cells. Our previous work showed that anoikis resistance is associated with the metastasis of hepatocellular carcinoma (HCC) cells. The aim of this study is to elucidate the mechanisms of this course.

MATERIALS & METHODS

Expression of BNIP3 and HIF-1α at the mRNA and protein level in HCC cells were detected by realtime PCR and western blot, respectively. Autophagy activation and signaling transduction pathway were detected by western blot. Cell viabilities were detected by CCK8 assay and trypan blue exclusion assay.

RESULTS

Upregulation of BNIP3 promoted the activation of autophagy, one type of cell survival strategy in response to external stress, by suppressing mTOR/S6K1 signaling system. The upregulation of BNIP3 was mediated by ERK/HIF-1α pathway, which further contributed to anoikis resistance of HCC cells through the mTORC1 signaling pathway.

CONCLUSION

Upregulation of BNIP3 contributs to anoikis resistance of HCC cells, and BNIP3 may serve as a novel therapeutic target for manipulation of cancer metastasis.

The microenvironment reprograms circuits in tumor cells

In the course of multistep oncogenesis, initially normal cells acquire several new functions that render them malignant. We have recently demonstrated that the peritoneal microenvironment promotes resistance to anoikis in ovarian cancer cells by reprogramming SRC/AKT/ERK signaling and metabolism. These findings have prognostic and therapeutic implications.

Critical role of STAT3 in melanoma metastasis through anoikis resistance

Anoikis is an anchorage-independent cell death. Resistance to anoikis is one of the key features of metastatic cells. Here, we analyzed the role of STAT3 in anoikis resistance in melanoma cells leading to metastasis. When grown under anchorage-independent conditions, significant proportion of cells resisted anoikis and these resistant cells had higher rate of migration and invasion as compared to the cells grown under anchorage-dependent conditions. The anoikis resistant cells also had significantly higher expression and phosphorylation of STAT3 at Y705 than the cells that were attached to the basement membrane. STAT3 inhibitors, AG 490 and piplartine (PL) induced anoikis in a concentration-dependent manner in anoikis resistant cells. Over-expression of STAT3 or treatment with IL-6 not only increased anoikis resistance, but also protected the cancer cells from PL-induced anoikis. On the other hand, silencing STAT3 decreased the potential of cancer cells to resist anoikis and to migrate. STAT3 knock-down cells and PL treated cells did not form tumors as well as failed to metastasize in SCID-NSG mice as compared to untreated anchorage-independent cells, which formed big tumors and extensively metastasized. In summary, our results for the first time establish STAT3 as a critical player that renders anoikis resistance to melanoma cells and enhance their metastatic potential.

Understanding the Biology of Bone Sarcoma from Early Initiating Events through Late Events in Metastasis and Disease Progression

The two most common primary bone malignancies, osteosarcoma (OS), and Ewing sarcoma (ES), are both aggressive, highly metastatic cancers that most often strike teens, though both can be found in younger children and adults. Despite distinct origins and pathogenesis, both diseases share several mechanisms of progression and metastasis, including neovascularization, invasion, anoikis resistance, chemoresistance, and evasion of the immune response. Some of these processes are well-studies in more common carcinoma models, and the observation from adult diseases may be readily applied to pediatric bone sarcomas. Neovascularization, which includes angiogenesis and vasculogenesis, is a clear example of a process that is likely to be similar between carcinomas and sarcomas, since the responding cells are the same in each case. Chemoresistance mechanisms also may be similar between other cancers and the bone sarcomas. Since OS and ES are mesenchymal in origin, the process of epithelial-to-mesenchymal transition is largely absent in bone sarcomas, necessitating different approaches to study progression and metastasis in these diseases. One process that is less well-studied in bone sarcomas is dormancy, which allows micrometastatic disease to remain viable but not growing in distant sites – typically the lungs – for months or years before renewing growth to become overt metastatic disease. By understanding the basic biology of these processes, novel therapeutic strategies may be developed that could improve survival in children with OS or ES.