Involvement of the Integrin α1β1 in the Progression of Colorectal Cancer

The characteristics and the multiple functions of integrin β1 in human cancers

Integrins, which consist of two non-covalently linked α and β subunits, play a crucial role in cell-cell adhesion and cell-extracellular matrix (ECM) interactions. Among them, integrin β1 is the most common subunit and has emerged as a key mediator in cancer, influencing various aspects of cancer progression, including cell motility, adhesion, migration, proliferation, differentiation and chemotherapy resistance. However, given the complexity and sometimes contradictory characteristics, targeting integrin β1 for therapeutics has been a challenge. The emerging understanding of the mechanisms regulating by integrin β1 may guide the development of new strategies for anti-cancer therapy. In this review, we summarize the multiple functions of integrin β1 and signaling pathways which underlie the involvement of integrin β1 in several malignant cancers. Our review suggests the possibility of using integrin β1 as a therapeutic target and highlights the need for patient stratification based on expression of different integrin receptors in future clinical studies.

Proteomic Profiling of Colorectal Adenomas Identifies a Predictive Risk Signature for Development of Metachronous Advanced Colorectal Neoplasia

BACKGROUND & AIMS

Colonic adenomatous polyps, or adenomas, are frequent precancerous lesions and the origin of most cases of colorectal adenocarcinoma. However, we know from epidemiologic studies that although most colorectal cancers (CRCs) originate from adenomas, only a small fraction of adenomas (3%-5%) ever progress to cancer. At present, there are no molecular markers to guide follow-up surveillance programs.

METHODS

We profiled, by mass spectrometry-based proteomics combined with machine learning analysis, a selected cohort of formalin-fixed, paraffin-embedded high-grade (HG) adenomas with long clinical follow-up, collected as part of the Danish national screening program. We grouped subjects in the cohort according to their subsequent history of findings: a nonmetachronous advanced neoplasia group (G0), with no new HG adenomas or CRCs up to 10 years after polypectomy, and a metachronous advanced neoplasia group (G1) where individuals developed a new HG adenoma or CRC within 5 years of diagnosis.

RESULTS

We generated a proteome dataset from 98 selected HG adenoma samples, including 20 technical replicates, of which 45 samples belonged to the nonmetachronous advanced neoplasia group and 53 to the metachronous advanced neoplasia group. The clear distinction of these 2 groups seen in a uniform manifold approximation and projection plot indicated that the information contained within the abundance of the ∼5000 proteins was sufficient to predict the future occurrence of HG adenomas or development of CRC.

CONCLUSIONS

We performed an in-depth analysis of quantitative proteomic data from 98 resected adenoma samples using various novel algorithms and statistical packages and found that their proteome can predict development of metachronous advanced lesions and progression several years in advance.

Integrins in cancer: Emerging mechanisms and therapeutic opportunities

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

The effects of inhibition and siRNA knockdown of collagen-binding integrins on human umbilical vein endothelial cell migration and tube formation

Blood vessels in the body are lined with endothelial cells which have vital roles in numerous physiological and pathological processes. Collagens are major constituents of the extracellular matrix, and many adherent cells express several collagen-binding adhesion receptors. Here, we study the endothelium-collagen interactions mediated by the collagen-binding integrins, α1β1, α2β1, α10β1 and α11β1 expressed in human umbilical vein endothelial cells (HUVECs). Using qPCR, we found expression of the α10 transcript of the chondrocyte integrin, α10β1, along with the more abundant α2, and low-level expression of α1. The α11 transcript was not detected. Inhibition or siRNA knockdown of the α2-subunit resulted in impaired HUVEC adhesion, spreading and migration on collagen-coated surfaces, whereas inhibition or siRNA knockdown of α1 had no effect on these processes. In tube formation assays, inhibition of either α1 or α2 subunits impaired the network complexity, whereas siRNA knockdown of these integrins had no such effect. Knockdown of α10 had no effect on cell spreading, migration or tube formation in these conditions. Overall, our results indicate that the collagen-binding integrins, α1β1 and α2β1 play a central role in endothelial cell motility and self-organisation.

The human ion channel TRPM2 modulates migration and invasion in neuroblastoma through regulation of integrin expression

Transient receptor potential channel TRPM2 is highly expressed in many cancers and involved in regulation of key physiological processes including mitochondrial function, bioenergetics, and oxidative stress. In Stage 4 non-MYCN amplified neuroblastoma patients, high TRPM2 expression is associated with worse outcome. Here, neuroblastoma cells with high TRPM2 expression demonstrated increased migration and invasion capability. RNA sequencing, RT-qPCR, and Western blotting demonstrated that the mechanism involved significantly greater expression of integrins α1, αv, β1, and β5 in cells with high TRPM2 expression. Transcription factors HIF-1α, E2F1, and FOXM1, which bind promoter/enhancer regions of these integrins, were increased in cells with high TRPM2 expression. Subcellular fractionation confirmed high levels of α1, αv, and β1 membrane localization and co-immunoprecipitation confirmed the presence of α1β1, αvβ1, and αvβ5 complexes. Inhibitors of α1β1, αvβ1, and αvβ5 complexes significantly reduced migration and invasion in cells highly expressing TRPM2, confirming their functional role. Increased pAkt^Ser473 and pERK^{Thr202/Tyr204}, which promote migration through mechanisms including integrin activation, were found in cells highly expressing TRPM2. TRPM2 promotes migration and invasion in neuroblastoma cells with high TRPM2 expression through modulation of integrins together with enhancing cell survival, negatively affecting patient outcome and providing rationale for TRPM2 inhibition in anti-neoplastic therapy.

Cancer-Associated Fibroblasts: The Origin, Biological Characteristics and Role in Cancer-A Glance on Colorectal Cancer

Simple Summary

Tumor microenvironment is a major contributor to tumor growth, metastasis and resistance to therapy. It consists of many cancer-associated fibroblasts (CAFs), which derive from different types of cells. CAFs detected in different tumor types are linked to poor prognosis, as in the case of colorectal cancer. Although their functions differ according to their subtype, their detection is not easy, and there are no established markers for such detection. They are possible targets for therapeutic treatment. Many trials are ongoing for their use as a prognostic factor and as a treatment target. More research remains to be carried out to establish their role in prognosis and treatment.

Abstract

The therapeutic approaches to cancer remain a considerable target for all scientists around the world. Although new cancer treatments are an everyday phenomenon, cancer still remains one of the leading mortality causes. Colorectal cancer (CRC) remains in this category, although patients with CRC may have better survival compared with other malignancies. Not only the tumor but also its environment, what we call the tumor microenvironment (TME), seem to contribute to cancer progression and resistance to therapy. TME consists of different molecules and cells. Cancer-associated fibroblasts are a major component. They arise from normal fibroblasts and other normal cells through various pathways. Their role seems to contribute to cancer promotion, participating in tumorigenesis, proliferation, growth, invasion, metastasis and resistance to treatment. Different markers, such as a-SMA, FAP, PDGFR-β, periostin, have been used for the detection of cancer-associated fibroblasts (CAFs). Their detection is important for two main reasons; research has shown that their existence is correlated with prognosis, and they are already under evaluation as a possible target for treatment. However, extensive research is warranted.

ANXA1: An Important Independent Prognostic Factor and Molecular Target in Glioma

Objective: The expression, prognosis, and related mechanisms of ANXA1 are investigated in glioma, with the objective to find potential therapeutic molecular targets for glioma. Methods: We analyzed the gene expression of ANXA1 using glioma-related databases, including the Chinese Glioma Genome Atlas (CGGA) database, The Cancer Genome Atlas (TCGA) database, and the Gene Expression Omnibus (GEO) database. Moreover, we collected the sample tissues and corresponding paracancerous tissues of 23 glioma patients and then conducted a Western blot experiment to verify the expression and correlate survival of ANXA1. Moreover, we generated survival ROC curves, performing univariate and multivariate Cox analyses and the construction of the nomogram. Differential expression analysis was conducted by high and low grouping based on the median of the ANXA1 gene expression values. We conducted Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis and Gene Set Enrichment Analysis (GSEA) to explore possible mechanisms, and gene co-expression analysis was also performed. Results: The results showed that the ANXA1 expression level was higher in gliomas than in normal tissues, and a high expression level of ANXA1 in gliomas was associated with poorer prognosis. The independent prognosis analysis showed that the ANXA1 gene was an independent prognostic factor of glioma. In the analysis of KEGG and Gene Set Enrichment Analysis (GSEA), it is shown that ANXA1 may play an important role in glioma patients by affecting extracellular matrix (ECM)-receptor interaction and the focal adhesion signal pathway. The core genes, including COL1A1, COL1A2, FN1, ITGA1, and ITGB1, were screened for gene correlation and prognosis analysis. The expression level of the five genes was verified by qPCR in glioma. We concluded that these five core genes and ANXA1 could play a synergistic role in gliomas. Conclusion: The results indicated that a high expression level of ANXA1 leads to worse prognosis and ANXA1 is an independent prognostic factor and a potentially important target for the treatment of gliomas.

Roles of Integrins in Gastrointestinal Cancer Metastasis

Integrins are a large family of heterodimeric transmembrane receptors which mediate cell adhesion and transmit signals to the cell interior. The mechanistic roles of integrins have long been an enigma in cancer, given its complexity in regulating different cellular behaviors. Recently, however, increasing research is providing new insights into its function and the underlying mechanisms, which collectively include the influences of altered integrin expression on the aberrant signaling pathways and cancer progression. Many studies have also demonstrated the potentiality of integrins as therapeutic targets in cancer treatment. In this review, we have summarized these recent reports and put a particular emphasis on the dysregulated expression of integrins and how they regulate related signaling pathways to facilitate the metastatic progression of gastrointestinal cancer, including gastric cancer (GC) and colorectal cancer (CRC), which will address the crucial roles of integrins in gastrointestinal cancer.

Personalized Immunotherapy in Colorectal Cancers: Where Do We Stand?

Colorectal cancer (CRC) is the second leading cause of cancer death in the world. Immunotherapy using monoclonal antibodies, immune-checkpoint inhibitors, adoptive cell therapy, and cancer vaccines has raised great hopes for treating poor prognosis metastatic CRCs that are resistant to the conventional therapies. However, high inter-tumor and intra-tumor heterogeneity hinder the success of immunotherapy in CRC. Patients with a similar tumor phenotype respond differently to the same immunotherapy regimen. Mutation-based classification, molecular subtyping, and immunoscoring of CRCs facilitated the multi-aspect grouping of CRC patients and improved immunotherapy. Personalized immunotherapy using tumor-specific neoantigens provides the opportunity to consider each patient as an independent group deserving of individualized immunotherapy. In the recent decade, the development of sequencing and multi-omics techniques has helped us classify patients more precisely. The expansion of such advanced techniques along with the neoantigen-based immunotherapy could herald a new era in treating heterogeneous tumors such as CRC. In this review article, we provided the latest findings in immunotherapy of CRC. We elaborated on the heterogeneity of CRC patients as a bottleneck of CRC immunotherapy and reviewed the latest advances in personalized immunotherapy to overcome CRC heterogeneity.

The potential prognostic values of the ADAMTS-like protein family: an integrative pan-cancer analysis

Background

A disintegrin-like and metalloproteinase domain with thrombospondin type 1 motifs (ADAMTS)-like proteins, including ADAMTSL1-6 and papilin, which are part of the mammalian ADAMTS superfamily, appear to be relevant to extracellular matrix function and the regulation of ADAMTS protease activity. Their roles in tumor initiation and progression and regulating the tumor microenvironment (TME) are now recognized.

Methods

In the present study, a comprehensive investigation of the pan-cancer effects of ADAMTSLs and their associations with patient survival, drug responses, and the TME was performed by integrating The Cancer Genome Atlas (TCGA) data and annotated data resources.

Results

The expression of ADAMTSL family members was found to be dysregulated in many cancer types. More importantly, their expression was frequently associated with patients’ overall survival (OS), drug responses, and the TME. ADAMTSL1, ADAMTSL4, and ADAMTSL5 were primarily associated with aggressive phenotypes, while PAPLN was more frequently associated with a favorable prognosis. In a non-small cell lung cancer (NSCLC) cohort, Thrombospondin Type 1 Domain Containing 4 (THSD4) (ADAMTSL6) and Papilin (PAPLN) were associated with immune checkpoint inhibitor (ICI) sensitivity in samples from the Gene Expression Omnibus repository (GSE135222). Twenty and 30 proteins related to THSD4 and PAPLN, respectively, were identified through a proteomic analysis of 18 Chinese lung adenocarcinoma patients.

Conclusions

Our findings extend understandings of the role of the ADAMTSL family in cancers and are a valuable resource on their clinical utility. This article provides insight into the clinical importance of next-generation sequencing technology to identify novel biomarkers for prognosis and investigate therapeutic strategy for clinical benefit.

Loss of enteric neuronal Ndrg4 promotes colorectal cancer via increased release of Nid1 and Fbln2

The N-Myc Downstream-Regulated Gene 4 (NDRG4), a prominent biomarker for colorectal cancer (CRC), is specifically expressed by enteric neurons. Considering that nerves are important members of the tumor microenvironment, we here establish different Ndrg4 knockout (Ndrg4-/- ) CRC models and an indirect co-culture of primary enteric nervous system (ENS) cells and intestinal organoids to identify whether the ENS, via NDRG4, affects intestinal tumorigenesis. Linking immunostainings and gastrointestinal motility (GI) assays, we show that the absence of Ndrg4 does not trigger any functional or morphological GI abnormalities. However, combining in vivo, in vitro, and quantitative proteomics data, we uncover that Ndrg4 knockdown is associated with enlarged intestinal adenoma development and that organoid growth is boosted by the Ndrg4-/- ENS cell secretome, which is enriched for Nidogen-1 (Nid1) and Fibulin-2 (Fbln2). Moreover, NID1 and FBLN2 are expressed in enteric neurons, enhance migration capacities of CRC cells, and are enriched in human CRC secretomes. Hence, we provide evidence that the ENS, via loss of Ndrg4, is involved in colorectal pathogenesis and that ENS-derived Nidogen-1 and Fibulin-2 enhance colorectal carcinogenesis.

IL-33 is produced by colon fibroblasts and differentially regulated in acute and chronic murine colitis

IL-33 is upregulated in ulcerative colitis and has a protective role in chemically-induced acute murine colitis. We aimed to determine whether IL-33 influences Il10-/- chronic colitis and its cellular source in health and during colitis. Il10-/-Il33-/- and Il10-/-Il33+/+ littermates developed colitis of similar severity. Colon Il33 was induced in WT and Il10-/- mice exposed to DSS, but not in unchallenged Il10-/- mice with colitis. Il33-citrine reporter mice showed that Il33-citrine colocalized with α-smooth muscle actin+ myofibroblasts and vimentin+ fibroblasts in WT mice. Citrine+CD74+CD90hi inflammatory fibroblasts were increased with DSS treatment. IL-1β induced Il33 expression in colon myofibroblasts, but colon Il33 expression did not differ between DSS-treated WT and Il1r1-/- mice. In conclusion, deficiency of IL-33 does not alter the severity of chronic colitis in Il10-/- mice. Induction of Il33 upon DSS exposure in WT and Il10-/- mice, but not in unchallenged Il10-/- mice, suggests epithelial injury induces colon IL-33. Fibroblasts are the primary colonic source of IL-33 and IL-33-expressing CD90hiCD74+ fibroblasts are increased during DSS-induced colitis. IL-1β induces Il33 in colon myofibroblasts in vitro, but signaling through the IL-1R1 is not necessary for induction of IL-33 in DSS-induced colitis.

Twist2 is NFkB-responsive when p120-catenin is inactivated and EGFR is overexpressed in esophageal keratinocytes

Esophageal squamous cell carcinoma (ESCC) is among the most aggressive and fatal cancer types. ESCC classically progresses rapidly and frequently causes mortality in four out of five patients within two years of diagnosis. Yet, little is known about the mechanisms that make ESCC so aggressive. In a previous study we demonstrated that p120-catenin (p120ctn) and EGFR, two genes associated with poor prognosis in ESCC, work together to cause invasion. Specifically, inactivation of p120ctn combined with overexpression of EGFR induces a signaling cascade that leads to hyperactivation of NFkB and a resultant aggressive cell type. The purpose of this present study was to identify targets that are responsive to NFkB when p120ctn and EGFR are modified. Using human esophageal keratinocytes, we have identified Twist2 as an NFkB-responsive gene. Interestingly, we found that when NFkB is hyperactivated in cells with EGFR overexpression and p120ctn inactivation, Twist2 is significantly upregulated. Inhibition of NFkB activity results in nearly complete loss of Twist2 expression, suggesting that this potential EMT-inducing gene, is a responsive target of NFkB. There exists a paucity of research on Twist2 in any cancer type; as such, these findings are important in ESCC as well as in other cancer types.

Periostin regulates autophagy through integrin α5β1 or α6β4 and an AKT-dependent pathway in colorectal cancer cell migration

Colorectal cancer (CRC) is one of the most fatal cancers with highly invasive properties. The progression of CRC is determined by the driving force of periostin (PN) from cancer‐associated fibroblasts (CAFs) in the tumour microenvironment. This present work aims to investigate autophagy‐mediated CRC invasion via the receptor integrin (ITG) by PN. The level of PN in 410 clinical CRC tissues was found increased and was an independent poor prognosis marker (HR = 2.578, 95% CI = 1.218‐5.457, P‐value = .013) with a significant correlation with overall survival time (P‐value < .001). PN activated proliferation, migration and invasion of CRC cells, but with reduced autophagy. Interestingly, the reduction of LC3 autophagic protein corresponded to the increased ability of CRC cell migration. The siITGα5‐treated HT‐29 and siITGβ4‐treated HCT‐116 CRC cells attenuated epithelial‐to‐mesenchymal transitions (EMT)‐related genes and pAKT compared with those in siITG‐untreated cells. The reduction of pAKT by a PI3K inhibitor significantly restored autophagy in CRC cells. These evidences confirmed the effect of PN through either ITGα5β1 or ITGα6β4 and the AKT‐dependent pathway to control autophagy‐regulated cell migration. In conclusion, these results exhibited the impact of PN activation of ITGα5β1 or ITGα6β4 through pAKT in autophagy‐mediated EMT and migration in CRC cells.

Reciprocal Interplay Between Fibrillar Collagens and Collagen-Binding Integrins: Implications in Cancer Progression and Metastasis

Cancers are complex ecosystems composed of malignant cells embedded in an intricate microenvironment made of different non-transformed cell types and extracellular matrix (ECM) components. The tumor microenvironment is governed by constantly evolving cell-cell and cell-ECM interactions, which are now recognized as key actors in the genesis, progression and treatment of cancer lesions. The ECM is composed of a multitude of fibrous proteins, matricellular-associated proteins, and proteoglycans. This complex structure plays critical roles in cancer progression: it functions as the scaffold for tissues organization and provides biochemical and biomechanical signals that regulate key cancer hallmarks including cell growth, survival, migration, differentiation, angiogenesis, and immune response. Cells sense the biochemical and mechanical properties of the ECM through specialized transmembrane receptors that include integrins, discoidin domain receptors, and syndecans. Advanced stages of several carcinomas are characterized by a desmoplastic reaction characterized by an extensive deposition of fibrillar collagens in the microenvironment. This compact network of fibrillar collagens promotes cancer progression and metastasis, and is associated with low survival rates for cancer patients. In this review, we highlight how fibrillar collagens and their corresponding integrin receptors are modulated during cancer progression. We describe how the deposition and alignment of collagen fibers influence the tumor microenvironment and how fibrillar collagen-binding integrins expressed by cancer and stromal cells critically contribute in cancer hallmarks.

Cancer-associated fibroblasts of colorectal cancer and their markers: updates, challenges and translational outlook

Accumulation of cancer-associated fibroblasts (CAFs) in the tumor microenvironment is associated with poor prognosis and recurrence of colorectal cancer (CRC). Despite their prominent roles in colorectal carcinogenesis, there is a lack of robust and specific markers to classify the heterogeneous and highly complex CAF populations. This has resulted in confusing and misleading definitions of CAFs in cancer niche. Advancements in molecular biology approaches have open doors to reliable CAF marker detection methods in various solid tumors. These discoveries would contribute to more efficient screening, monitoring and targeted therapy of CRC thus potentially will reduce cancer morbidity and mortality rates. This review highlights current scenarios, dilemma, translational potentials of CAF biomarker and future therapeutic applications involving CAF marker identification in CRC.

TRM integrins CD103 and CD49a differentially support adherence and motility after resolution of influenza virus infection

Current influenza vaccination strategies require annual immunizations, with fairly low efficacy rates. One technique to improve protection against a greater breadth of influenza viruses is to elicit broadly cross-reactive cell-mediated immunity and generate a local population of cytotoxic T cells to respond to conserved regions of circulating viruses. However, this approach requires improved understanding of how these cells migrate within and attach to the tissue in order to persist and offer long-term immunity. This study investigates how receptors on the T cell surface impact the cell’s ability to interact with the tissue and provide evidence of which of these receptors are essential for protection. Furthermore, these studies reveal functional in vivo mechanisms of cellular markers used to characterize T_RM.

Tissue-resident memory CD8 T (T_RM) cells are a unique immune memory subset that develops and remains in peripheral tissues at the site of infection, providing future host resistance upon reexposure to that pathogen. In the pulmonary system, T_RM are identified through S1P antagonist CD69 and expression of integrins CD103/β7 and CD49a/CD29(β1). Contrary to the established role of CD69 on CD8 T cells, the functions of CD103 and CD49a on this population are not well defined. This study examines the expression patterns and functions of CD103 and CD49a with a specific focus on their impact on T cell motility during influenza virus infection. We show that the T_RM cell surface phenotype develops by 2 wk postinfection, with the majority of the population expressing CD49a and a subset that is also positive for CD103. Despite a previously established role in retaining T_RM in peripheral tissues, CD49a facilitates locomotion of virus-specific CD8 T cells, both in vitro and in vivo. These results demonstrate that CD49a may contribute to local surveillance mechanisms of the T_RM population.

Investigating TNS4 in the Colorectal Tumor Microenvironment Using 3D Spheroid Models of Invasion

TNS4 (Tensin 4 or Cten) is a putative oncogene in colorectal cancer (CRC) with a role in regulating cell adhesion, motility, invasion, and epithelial to mesenchymal transition (EMT). The objective is to study the role of TNS4 in CRC using more realistic models of the tumor microenvironment. CRC cells expressing TdTomato protein and shTNS4/shLUC hairpin oligos are grown in 3D spheroids with and without cancer-associated fibroblasts (CAFs). Adhesiveness to collagen I and CAFs is assessed in 2D and cell proliferation, volume, and invasion are assessed in 3D conditions. The role of TNS4 knockdown in gefitinib chemosensitivity and epidermal growth factor receptor (EGFR) and Ras protein levels are also tested. In general, TNS4 knockdown increases cell proliferation in cell lines producing compact spheroids. The addition of CAFs in spheroids supports CRC cell proliferation, whereas CAFs themselves do not proliferate, but increases ECM degradation. TNS4 knockdown reduces adhesiveness and 3D invasion and disrupts EGFR signaling which results in increased sensitivity to Gefitinib. In conclusion, in a 3D spheroid model, TNS4 inhibits cell proliferation and promotes cell invasion into the ECM, possibly by adhesion to the ECM and stromal cells. TNS4 knockdown enhances sensitivity to the EGFR inhibitor gefitinib and may be helpful for Kirsten ras oncogene homolog mutant CRC patients.

Integrin α1 promotes tumorigenicity and progressive capacity of colorectal cancer

Colorectal cancer (CRC) is the second leading cause of death globally. Integrin α1 (ITGA1) belongs to integrin family and involves in regulating cell adhesion, invasion, proliferation and tumorigenicity, its expression is up-regulated in various cancers, including CRC. However, the molecular understanding and clinical relevance of ITGA1 in the development and progression of CRC remain unclear. In the present study, we detected ITGA1 in 50 CRC tissues and adjacent non-cancerous tissues, sera from 100 CRC patients and 50 healthy subjects, and four CRC cell lines using immunohistochemistry staining, enzyme-linked immunosorbent assay and Western blotting. We found that the ITGA1 protein was significantly higher in human CRC tissues and cell lines than both paired non-tumor tissues and normal cells, respectively. In addition, the serum concentration of ITGA1 was also higher in CRC patients compared to the healthy subjects (p<0.01) and was significantly associated with metastatic TNM stages (p<0.0001) and circulating carbohydrate antigen 199 (CA199) (p<0.022). Furthermore, down-regulation of ITGA1 with transfecting LV-shITGA1 inhibited the progressive capacity of cell migration and invasion in CRC SW480 cell line and the tumorgenicity in nude mice. In functional studies, ITGA1 knockdown also inhibited Ras/ERK signaling pathway by decreasing the expression of Ras, p-Erk1/2 and c-Myc in SW480. Contrastly, when evelated expression of ITGA1 in NCM460 coincided with the increased expression of Ras, p-Erk1/2 and c-Myc. Taken together, our findings suggest that ITGA1 is an oncogene with a capability to promote CRC cell migration, invasion and tumorigenicity by activating the Ras/Erk signaling, implying that it may be a novel target for the diagnosis and treatment of CRC, and warrants further investigation.

Integrin α6β4 in Colorectal Cancer: Expression, Regulation, Functional Alterations and Use as a Biomarker

Integrin α6β4 is one of the main laminin receptors and is primarily expressed by epithelial cells as an active component of hemidesmosomes. In this article, after a brief summary about integrins in the gut epithelium in general, I review the knowledge and clinical potential of this receptor in human colorectal cancer (CRC) cells. Most CRC cells overexpress both α6 and β4 subunits, in situ in primary tumours as well as in established CRC cell lines. The mechanisms that lead to overexpression have not yet been elucidated but clearly involve specific transcription factors such as MYC. From a functional point of view, one key element affecting CRC cell behaviour is the relocalization of α6β4 to the actin cytoskeleton, favouring a more migratory and anoikis-resistant phenotype. Another major element is its expression under various molecular forms that have the distinct ability to interact with ligands (α6β4 ± ctd) or to promote pro- or anti-proliferative properties (α6Aβ4 vs. α6Bβ4). The integrin α6β4 is thus involved in most steps susceptible to participation with CRC progression. The potential clinical significance of this integrin has begun to be investigated and recent studies have shown that ITGA6 and ITGB4 can be useful biomarkers for CRC early detection in a non-invasive assay and as a prognostic factor, respectively.

Co-expression Network Analysis Identified Key Proteins in Association With Hepatic Metastatic Colorectal Cancer

PURPOSE

Intense efforts have been made in colorectal cancer (CRC) treatment in recent decades. However, the mechanism of development and metastasis of CRC has not been fully cleared. This study is designed to identify key proteins involved in stage III and hepatic metastatic CRC.

EXPERIMENT DESIGN

Protein expression profiles of paired tumor and benign tissue samples from stage III and hepatic metastatic CRC patients are characterized by using a label-free proteomics approach. Key proteins relevant to hepatic metastatic CRC are revealed by weighted gene correlation network analysis (WGCNA) and other bioinformatics tools.

RESULTS

WGCNA reveals three hub modules: CRC without specific stage (turquoise), stage III CRC (blue), and hepatic metastatic CRC (green). Nine key proteins (heat shock protein family D member 1 (HSPD1), eukaryotic translation elongation factor 1 gamma, heterogeneous nuclear ribonucleoprotein A2/B1, fibrinogen beta chain (FGB), Talin 1, adaptor related protein complex 2 subunit alpha 2, serrate RNA effector molecule homolog, apolipoprotein C3, phosphoglucomutase 5) are identified. Moreover, upregulation of HSPD1 is validated in CRC tissue by the immunohistochemistry. Upregulation of fibrinogen is validated in metastatic CRC by plasma fibrinogen assay.

CONCLUSION AND CLINICAL RELEVANCE

This study provides the proteomic analysis of stage III and hepatic metastatic CRC to identify key proteins of CRC. FGB plays a key role to serve as diagnostic and therapeutic biomarkers for hepatic metastatic CRC.

Accumulation of Tumor-Infiltrating CD49a+ NK Cells Correlates with Poor Prognosis for Human Hepatocellular Carcinoma

The discovery of CD49a⁺ liver-resident natural killer (NK) cells in mice alters our view of NK cells and provides another opportunity to study NK cells. Although evidence has suggested roles for NK cells in liver diseases, whether and how CD49a⁺ NK cells contribute to liver diseases remain unclear. In this study, we observed that accumulation of CD49a⁺ tissue-resident NK cells in human hepatocellular carcinoma (HCC) was higher than in peritumoral tissues. We studied the exhausted and regulatory phenotypes of CD49a⁺ tissue-resident NK cells by analysis of protein and mRNA. The proportion of CD49a⁺ NK cells was positively correlated to the proportion of NK cells expressing inhibitory receptors. In addition, CD49a⁺ NK cells expressed more of checkpoint molecules PD-1, CD96, and TIGIT. Transcriptomic analysis implicated CD49a⁺ tissue-resident NK cells in the negative regulation of immune responses. Comparison of murine and human CD49a⁺ NK cells revealed their distinct characteristics and functions. Finally, accumulation of tissue-resident CD49a⁺ NK cells in liver tumor was correlated to deteriorating disease condition and poor prognosis. Our findings show that CD49a⁺ NK cells accumulate in liver tumor and suggest a role for CD49a⁺ NK cells in the negative regulation of immune responses and the development of HCC.

MYC Regulates α6 Integrin Subunit Expression and Splicing Under Its Pro-Proliferative ITGA6A Form in Colorectal Cancer Cells

The α6 integrin subunit (ITGA6) pre-mRNA undergoes alternative splicing to form two splicing variants, named ITGA6A and ITGA6B. In primary human colorectal cancer cells, the levels of both ITGA6 and β4 integrin subunit (ITGB4) subunits of the α6β4 integrin are increased. We previously found that the upregulation of ITGA6 is a direct consequence of the increase of the pro-proliferative ITGA6A variant. However, the mechanisms that control ITGA6 expression and splicing into the ITGA6A variant over ITGA6B in colorectal cancer cells remain poorly understood. Here, we show that the promoter activity of the ITGA6 gene is regulated by MYC. Pharmacological inhibition of MYC activity with the MYC inhibitor (MYCi) 10058-F4 or knockdown of MYC expression by short hairpin RNA (shRNA) both lead to a decrease in ITGA6 and ITGA6A levels in colorectal cancer cells, while overexpression of MYC enhances ITGA6 promoter activity. We also found that MYC inhibition decreases the epithelial splicing regulatory protein 2 (ESRP2) splicing factor at both the mRNA and protein levels. Chromatin immunoprecipitation revealed that the proximal promoter sequences of ITGA6 and ESRP2 were occupied by MYC and actively transcribed in colorectal cancer cells. Furthermore, expression studies in primary colorectal tumors and corresponding resection margins confirmed that the up-regulation of the ITGA6A subunit can be correlated with the increase in MYC and ESRP2. Taken together, our results demonstrate that the proto-oncogene MYC can regulate the promoter activation and splicing of the ITGA6 integrin gene through ESRP2 to favor the production of the pro-proliferative ITGA6A variant in colorectal cancer cells.

Colorectal Cancers: An Update on Their Molecular Pathology

Colorectal cancers (CRCs) are the third leading cause of cancer-related mortality worldwide. Rather than being a single, uniform disease type, accumulating evidence suggests that CRCs comprise a group of molecularly heterogeneous diseases that are characterized by a range of genomic and epigenomic alterations. This heterogeneity slows the development of molecular-targeted therapy as a form of precision medicine. Recent data regarding comprehensive molecular characterizations and molecular pathological examinations of CRCs have increased our understanding of the genomic and epigenomic landscapes of CRCs, which has enabled CRCs to be reclassified into biologically and clinically meaningful subtypes. The increased knowledge of the molecular pathological epidemiology of CRCs has permitted their evolution from a vaguely understood, heterogeneous group of diseases with variable clinical courses to characteristic molecular subtypes, a development that will allow the implementation of personalized therapies and better management of patients with CRC. This review provides a perspective regarding recent developments in our knowledge of the molecular and epidemiological landscapes of CRCs, including results of comprehensive molecular characterizations obtained from high-throughput analyses and the latest developments regarding their molecular pathologies, immunological biomarkers, and associated gut microbiome. Advances in our understanding of potential personalized therapies for molecularly specific subtypes are also reviewed.