Clustering of integrin α5 at the lateral membrane restores epithelial polarity in invasive colorectal cancer cells

Tumor cell-derived ANGPTL2 promotes β-catenin-driven intestinal tumorigenesis

Uncontrolled proliferation of intestinal epithelial cells caused by mutations in genes of the WNT/β-catenin pathway is associated with development of intestinal cancers. We previously reported that intestinal stromal cell-derived angiopoietin-like protein 2 (ANGPTL2) controls epithelial regeneration and intestinal immune responses. However, the role of tumor cell-derived ANGPTL2 in intestinal tumorigenesis remained unclear. Here, we show that tumor cell-derived ANGPTL2 promotes β-catenin-driven intestinal tumorigenesis. ANGPTL2 deficiency suppressed intestinal tumor development in an experimental mouse model of sporadic colon cancer. We also found that increased ANGPTL2 expression in colorectal cancer (CRC) cells augments β-catenin pathway signaling and promotes tumor cell proliferation. Relevant to mechanism, our findings suggest that tumor cell-derived ANGPTL2 upregulates expression of OB-cadherin, which then interacts with β-catenin, blocking destruction complex-independent proteasomal degradation of β-catenin proteins. Moreover, our observations support a model whereby ANGPTL2-induced OB-cadherin expression in CRC cells is accompanied by decreased cell surface integrin α5β1 expression. These findings overall provide novel insight into mechanisms of β-catenin-driven intestinal tumorigenesis.

Plasmon Coupling Enhanced Micro-Spectroscopy and Imaging for Sensitive Discrimination of Membrane Domains of a Single Cell

Different cell membrane domains play different roles in many cell processes, and the discrimination of these domains is of considerable importance for the elucidation of cellular functions. However, the strategies available for distinguishing these cell membrane domains are limited. A novel technique called plasmon coupling enhanced micro-spectroscopy and imaging to discriminate basal and lateral membrane domains of a single cell combines the application of an additional plasmonic silver film for surface plasmon (SP) excitation to selectively excite and enhance the basal membranes in the near-field with directional enhanced microscopic imaging and spectroscopy. The SP and critical evanescent fields are induced upon excitation through a silver-coated semitransparent coverslip at the surface plasmon resonance and critical angles, respectively. The basal and lateral membrane domains located within the SP and critical evanescent fields can be selectively excited and distinguished by adjusting the incident angle of laser irradiation. Moreover, the brighter images and more intense spectra of membrane-targeting fluorescence-Raman probes under directional excitation than in conventional EPI mode allow clear identification of the membrane domains.

Long non-coding RNA ABHD11-AS1 promotes colorectal cancer progression and invasion through targeting the integrin subunit alpha 5/focal adhesion kinase/phosphoinositide 3 kinase/Akt signaling pathway

Long non-coding (lnc)RNA ABHD11-AS1 participates in the development and progress of various cancers, but its role in colorectal cancer (CRC) remains poorly known. In the present study, public database analysis and quantitative reverse transcription PCR of CRC and normal tissues showed that ABHD11-AS1 was overexpressed in CRC and associated with poor prognosis in CRC patients. Both in vitro and in vivo experiments demonstrated that loss-of-function of ABHD11-AS1 attenuated the proliferation, migration, and invasion of CRC cells and induced their apoptosis. Transcriptome sequencing and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis indicated that the phosphoinositide 3 kinase (PI3K)/Akt signaling pathway is a potential target of ABHD11-AS1. Additionally, we noted that ABHD11-AS1 deficiency reduced integrin subunit alpha (ITGA)5 expression, and impaired the phosphorylation of P85, focal adhesion kinase (FAK), and Akt1 in CRC cell lines and tumor tissues of nude mice. Furthermore, we observed that ITGA5 overexpression abrogated the effect of ABHD11-AS1 knockdown on the proliferation and invasion abilities of CRC cells. Taken together, our studies suggest that lncRNA ABHD11-AS1 promotes proliferation, migration, and invasion in CRC by activating the ITGA5/Fak/PI3K/Akt signaling pathway, and that the ITGA5/Fak/PI3K/Akt axis is a promising target for CRC therapy.

BZD9L1 sirtuin inhibitor: Identification of key molecular targets and their biological functions in HCT 116 colorectal cancer cells

BZD9L1 was previously described as a SIRT1/2 inhibitor with anti-cancer activities in colorectal cancer (CRC), either as a standalone chemotherapy or in combination with 5-fluorouracil. BZD9L1 was reported to induce apoptosis in CRC cells; however, the network of intracellular pathways and crosstalk between molecular players mediated by BZD9L1 is not fully understood. This study aimed to uncover the mechanisms involved in BZD9L1-mediated cytotoxicity based on previous and new findings for the prediction and identification of related pathways and key molecular players. BZD9L1-regulated candidate targets (RCTs) were identified using a range of molecular, cell-based and biochemical techniques on the HCT 116 cell line. BZD9L1 regulated major cancer pathways including Notch, p53, cell cycle, NFκB, Myc/MAX, and MAPK/ERK signalling pathways. BZD9L1 also induced reactive oxygen species (ROS), regulated apoptosis-related proteins, and altered cell polarity and adhesion profiles. In silico analyses revealed that most RCTs were interconnected, and were involved in the modulation of catalytic activity, metabolism and transcription regulation, response to cytokines, and apoptosis signalling pathways. These RCTs were implicated in p53-dependent apoptosis pathway. This study provides the first assessment of possible associations of molecular players underlying the cytotoxic activity of BZD9L1, and establishes the links between RCTs and apoptosis through the p53 pathway.

Cell surface integrin α5ß1 clustering negatively regulates receptor tyrosine kinase signaling in colorectal cancer cells via glycogen synthase kinase 3

As a key process within the tissue microenvironment, integrin signaling can influence cell functional responses to growth factor stimuli. We show here that clustering of integrin α5ß1 at the plasma membrane of colorectal cancer-derived epithelial cells modulates their ability to respond to stimulation by receptor tyrosine kinase (RTK)-activating growth factors EGF, NRG and HGF, through GSK3-mediated suppression of Akt pathway. We observed that integrin α5ß1 is lost from the membrane of poorly organized human colorectal tumors and that treatment with the integrin-clustering antibody P4G11 is sufficient to induce polarity in a mouse tumor xenograft model. While adding RTK growth factors (EGF, NRG and HGF) to polarized colorectal cancer cells induced invasion and loss of monolayer formation in 2D and 3D, this pathological behavior could be blocked by P4G11. Phosphorylation of ErbB family members as well as MET following EGF, NRG and HGF treatment was diminished in cells pretreated with P4G11. Focusing on EGFR, we found that blockade of integrin α5ß1 increased EGFR phosphorylation. Since activity of multiple downstream kinase pathways were altered by these various treatments, we employed computational machine learning techniques to ascertain the most important effects. Partial least-squares discriminant analysis identified GSK3 as a major regulator of EGFR pathway activities influenced by integrin α5ß1. Moreover, we used partial correlation analysis to examine signaling pathway crosstalk downstream of EGF stimulation and found that integrin α5ß1 acts as a negative regulator of the AKT signaling cascade downstream of EGFR, with GSK3 acting as a key mediator. We experimentally validated these computational inferences by confirming that blockade of GSK3 activity is sufficient to induce loss of polarity and increase of oncogenic signaling in the colonic epithelial cells.

BMAL1 Knockdown Leans Epithelial-Mesenchymal Balance toward Epithelial Properties and Decreases the Chemoresistance of Colon Carcinoma Cells

The circadian clock coordinates biological and physiological functions to day/night cycles. The perturbation of the circadian clock increases cancer risk and affects cancer progression. Here, we studied how BMAL1 knockdown (BMAL1-KD) by shRNA affects the epithelial-mesenchymal transition (EMT), a critical early event in the invasion and metastasis of colorectal carcinoma (CRC). In corresponding to a gene set enrichment analysis, which showed a significant enrichment of EMT and invasive signatures in BMAL1_high CRC patients as compared to BMAL1_low CRC patients, our results revealed that BMAL1 is implicated in keeping the epithelial-mesenchymal equilibrium of CRC cells and influences their capacity of adhesion, migration, invasion, and chemoresistance. Firstly, BMAL1-KD increased the expression of epithelial markers (E-cadherin, CK-20, and EpCAM) but decreased the expression of Twist and mesenchymal markers (N-cadherin and vimentin) in CRC cell lines. Finally, the molecular alterations after BMAL1-KD promoted mesenchymal-to-epithelial transition-like changes mostly appeared in two primary CRC cell lines (i.e., HCT116 and SW480) compared to the metastatic cell line SW620. As a consequence, migration/invasion and drug resistance capacities decreased in HCT116 and SW480 BMAL1-KD cells. Together, BMAL1-KD alerts the delicate equilibrium between epithelial and mesenchymal properties of CRC cell lines, which revealed the crucial role of BMAL1 in EMT-related CRC metastasis and chemoresistance.

Nongenomic Actions of Thyroid Hormone: The Integrin Component

The extracellular domain of plasma membrane integrin αvβ3 contains a cell surface receptor for thyroid hormone analogues. The receptor is largely expressed and activated in tumor cells and rapidly dividing endothelial cells. The principal ligand for this receptor is l-thyroxine (T₄), usually regarded only as a prohormone for 3,5,3'-triiodo-l-thyronine (T₃), the hormone analogue that expresses thyroid hormone in the cell nucleus via nuclear receptors that are unrelated structurally to integrin αvβ3. At the integrin receptor for thyroid hormone, T₄ regulates cancer and endothelial cell division, tumor cell defense pathways (such as anti-apoptosis), and angiogenesis and supports metastasis, radioresistance, and chemoresistance. The molecular mechanisms involve signal transduction via mitogen-activated protein kinase and phosphatidylinositol 3-kinase, differential expression of multiple genes related to the listed cell processes, and regulation of activities of other cell surface proteins, such as vascular growth factor receptors. Tetraiodothyroacetic acid (tetrac) is derived from T₄ and competes with binding of T₄ to the integrin. In the absence of T₄, tetrac and chemically modified tetrac also have anticancer effects that culminate in altered gene transcription. Tumor xenografts are arrested by unmodified and chemically modified tetrac. The receptor requires further characterization in terms of contributions to nonmalignant cells, such as platelets and phagocytes. The integrin αvβ3 receptor for thyroid hormone offers a large panel of cellular actions that are relevant to cancer biology and that may be regulated by tetrac derivatives.

Fully synthetic matrices for in vitro culture of primary human intestinal enteroids and endometrial organoids

Epithelial organoids derived from human donor tissues are important tools in fields ranging from regenerative medicine to drug discovery. Organoid culture requires expansion of stem/progenitor cells in Matrigel, a tumor-derived extracellular matrix (ECM). An alternative completely synthetic ECM could improve reproducibility, clarify mechanistic phenomena, and enable human implantation of organoids. We designed synthetic ECMs with tunable biomolecular and biophysical properties to identify gel compositions supporting human tissue-derived stem/progenitor epithelial cells as enteroids and organoids starting with single cells rather than tissue fragments. The synthetic ECMs consist of 8-arm PEG-macromers modified with ECM-binding peptides and different combinations of integrin-binding peptides, crosslinked with peptides susceptible to matrix metalloprotease (MMP) degradation, and tuned to exhibit a range of biophysical properties. A gel containing an α2β1 integrin-binding peptide (GFOGER) and matrix binder peptides grafted to a 20 kDa 8-arm PEG macromer showed the most robust support of human duodenal and colon enteroids and endometrial organoids. In this synthetic ECM, human intestinal enteroids and endometrial organoids emerge from single cells and show cell-specific and apicobasal polarity markers upon differentiation. Intestinal enteroids, in addition, retain their proliferative capacity, are functionally responsive to basolateral stimulation, express canonical markers of intestinal crypt cells including Paneth cells, and can be serially passaged. The success of this synthetic ECM in supporting human postnatal organoid culture from multiple different donors and from both the intestine and endometrium suggests it may be broadly useful for other epithelial organoid culture.

Molecular determinants of the interaction between glioblastoma CD133+ cancer stem cells and the extracellular matrix

Glioblastoma multiforme (GBM) is the most common primary tumor of the human brain. It is characterized by invasive growth and strong resistance to treatment, and the median survival time of patients is 15 months. The invasive growth of this tumor type is associated with tumor cells with an aggressive phenotype, while its treatment resistance is attributed to cancer stem cells (CSCs). It remains unclear if CSCs have a more invasive nature than differentiated glioblastoma cells (DGCs), and what contribution CSCs make to the aggressive phenotype of GBM. Interaction with the extracellular matrix (ECM) is a key factor in the development of invasion. The aim of the present study was to compare the expression levels of signaling pathway proteins involved in interaction of receptors with the ECM in CSCs and DGCs. The U-87MG GBM cell line was used in the present study CSCs were extracted from gliomaspheres through magnetic-activated cell sorting based on the expression of cluster of differentiation 133 (CD133); CD133-negative DCGs were used as a control. HPLC and mass spectrometry were also used, and biological and molecular functions, signaling pathways and protein-protein interactions were analyzed using publicly available databases. Increased expression levels of the following 10 proteins involved in interaction with the ECM were identified in CSCs, compared with expression levels in DGCs: COL6A1, COL6A3, FN1, ITGA2, ITGA5, ITGAV, ITGB1, ITGB3, LAMB1 and LAMC1. The proteome of CSCs was observed to have >2-fold higher expression of these key proteins, when compared with the DGC proteome. Increased expression levels of four proteins (FERMT2, LOXL2, HDAC2 and FBN1) involved in activating signaling in response to receptor interaction with the ECM was also observed, indicating that CSCs may have highly invasive nature. LOXL2 expression level was >9-fold higher in CSCs compared to DGCs, suggesting that this protein may have potential as an marker for CSCs and as a target for this cell type in GBM.

Broad-spectrum receptor tyrosine kinase inhibitors overcome de novo and acquired modes of resistance to EGFR-targeted therapies in colorectal cancer

It is increasingly appreciated that 3D cultures are more predictive of in vivo therapeutic efficacy than 2D cultures. Using in vitro 3D type I collagen cultures of human colorectal cancer (CRC) cell line HCA-7 derivatives CC, SC, and CC-CR, we previously identified that activation of receptor tyrosine kinases (RTKs) MET and RON contributed to resistance to the EGF receptor (EGFR)-directed therapeutic antibody cetuximab. The de novo mode of cetuximab resistance in SC cells could be overcome by crizotinib, a multi-RTK inhibitor that also targets MET and RON. We now show that crizotinib also overcomes acquired cetuximab resistance in CC-CR cells. Phospho-RTK array analysis showed increased phosphorylation of several RTKs, including MET and RON, in SC and CC-CR cells compared to cetuximab-sensitive CC counterparts. Furthermore, other multi-RTK inhibitors cabozantinib and BMS-777607 helped overcome cetuximab resistance, as measured by 3D colony growth and activation state of key signaling molecules. Conversely, addition of RTK ligands HGF and NRG1 induced cetuximab resistance in CC cells, which could be blocked by addition of crizotinib. We further determined the mechanism of the cooperative effect of cetuximab and crizotinib by FACS analysis and observed increased cell cycle arrest in G1 phase in cetuximab-resistant CRC 3D cultures. Finally, we show that crizotinib overcomes cetuximab resistance in vivo in SC nude mice xenografts. Thus, our work shows that multi-RTK inhibition strategy is a potent, broadly applicable strategy to overcome resistance to EGFR-targeted therapeutics in CRC and highlights the relevance of 3D cultures in these studies.

Statement of implication: Using in vitro 3D CRC cultures and in vivo CRC xenografts, we show that parallel inhibition of multiple RTKs with small molecule inhibitors overcomes de novo and acquired resistance to EGFR-directed therapies in CRC.

Supplemental psyllium fibre regulates the intestinal barrier and inflammation in normal and colitic mice

Our previous study demonstrated that supplemental psyllium fibre increased cytoprotective heat-shock protein (Hsp) 25 levels in the intestinal cells of mice. Here, we examined the effect of psyllium fibre on colonic gene and protein expression and faecal microbiota in normal and colitic mice to improve the understanding of the preventive role of the supplement. DNA microarray analysis revealed that a 10 % psyllium fibre diet administered for 5 d up-regulated eleven extracellular matrix (ECM)-associated genes, including collagens and fibronectins, in normal mice. Acute colitis was induced using dextran sodium sulphate (DSS) in mice that were administered a pre-feeding 5 to 10 % psyllium fibre diet for 5 d. Psyllium fibre partially ameliorated or resolved the DSS-induced colon damage and inflammation characterised by body weight loss, colon shortening, increased levels of pro-inflammatory cytokines and decreased tight junction protein expression in the colon. Analysis of faecal microbiota using denaturing gradient gel electrophoresis of the PCR-amplified 16S rRNA gene demonstrated that psyllium fibre affected the colonic microbiota. Intestinal permeability was evaluated by growing intestinal Caco-2 cell monolayers on membrane filter supports coated with or without fibronectin and collagen. Cells grown on collagen and fibronectin coating showed higher transepithelial electrical resistance, indicating a strengthening of barrier integrity. Therefore, increased Hsp25 levels and modification of colonic ECM contribute to the observed psyllium-mediated protection against DSS-induced colitis. Furthermore, ECM modification appears to play a role in the strengthening of the colon barrier. In conclusion, psyllium fibre may be useful in the prevention of intestinal inflammatory diseases.