The RNA-Binding Proteins OAS1, ZFP36L2, and DHX58 Are Involved in the Regulation of CD44 mRNA Splicing in Colorectal Cancer Cells

Regulation of alternative splicing is carried out by RNA-binding proteins. Each alternative splicing event is controlled by several RNA-binding proteins, which in combination create the distribution of alternative splicing products in a given cell type. Transmembrane protein CD44 plays an important role at various stages of the metastatic cascade and is considered as a promising molecule for the therapy of tumor diseases and the construction of prognostic classifiers. However, the functions of specific isoforms of this protein may differ significantly. In this work, we performed a bioinformatic search of RNA-binding proteins that can determine the expression of clinically significant isoforms 3 and 4 of CD44 protein. The analysis revealed five RNA-binding proteins, three of which (OAS1, ZFP36L2, and DHX58) are shown for the first time as potential regulators of the studied process.

Expression of CD44 Isoforms in Tumor Samples and Cell Lines of Human Colorectal Cancer

Detection of colorectal cancer biomarkers (CRC) remains an urgent task for the diagnosis and prediction of the disease course. A promising approach is the study of cancer stem cell markers. The cell surface glycoprotein CD44 is very important for CRC and its stem cells. Alternative splicing of 9 variable exons of CD44 mRNA leads to the formation of various isoforms of the protein with different roles in the progression of cancer. Studies of the functions of CD44 isoforms require adequate models considering the distribution of CD44 isoforms in real tumor samples. In the present study, the expression profile of CD44 isoforms in CRC was assessed based on the publicly available mRNA sequencing data of patient tumors from the TCGA-COAD database. It was shown that normal tissues predominantly expressed isoforms 3 and 4 at nearly equal levels, whereas tumors mainly expressed isoforms 2, 3, and 4; isoform 3 was expressed at the highest level. Further, the most relevant cell lines for studying the role of CD44 in CRC were identified based on the analysis of mRNA sequencing data of 55 CRC cell lines form CCLE database.

Selective changes in expression of integrin α-subunits in the intestinal epithelial Caco-2 cells under conditions of hypoxia and microcirculation

Intestinal epithelial cells are constantly exposed to physiologically hypoxic environment. The further reduction of tissue oxygen delivery may result in the intestinal epithelial cells function impairment, being a sign of active inflammation. The cultivation conditions are important when performing in vitro studies, since those may affect the cells’ properties. The study was aimed to assess the integrin receptor expression in the human colon adenocarcinoma Caco-2 cell line when simulating both hypoxic condition using the cobalt chloride and microcirculation. Transcriptome analysis revealed the significantly increased expression of the integrin receptors ITGA2 and ITGA5 α2- and α5-subunit genes under hypoxic conditions, as well as the reduction of ITGA5 during incubation in the microfluidic chip. The expression of β-subunits did not change. Analysis of microRNA transcriptomes revealed the decreased expression of hsa-miR-766-3p and hsa-miR-23b-5p microRNA. One of the validated targets for both microRNAs is mRNA of gene ITGA5. It has been shown that microcirculation makes it possible to bring the intestinal epithelial cells cultivation conditions closer to physiological conditions. The possible biological significance of the detected integrin expression profile alterations and the role of microcirculation have been discussed.

Interrelation between miRNA and mRNA expression in HT-29 line cells under hypoxia

Hypoxia accompanies various pathophysiological processes, including progression of tumors and metastasis. One of the mechanisms of molecular response of cells to hypoxia implies recruitment of specific miRNAs that regulate the expression of their target genes. This study aimed to evaluate the hypoxia-induced change in expression of miRNAs and their target genes in the HT-29 human colorectal adenocarcinoma cell line with the help of integrated miRNA and mRNA sequencing. To simulate hypoxia, the cells were treated with cobalt (II) chloride. We registered a significant change in expression of sixteen human miRNAs. Six of them (hsa-miR-18a-5p, hsa-miR-22-3p, hsa-miR-27a-5p, hsa-miR-182-5p, hsa-miR-215 -5p, hsa-miR-425-5p) had a significant proportion of target genes that had the expression changing in the opposite direction. Based on the bioinformatic analysis of interactions between differentially expressed transcription factors and miRNAs, we built a possible regulatory network with its main hubs being HIF-1α, p65, с-Myc, and Egr1 (encoded by the HIF1A, RELA, MYC and EGR1 genes).

Intracellular Transport of Ribosome-Inactivating Proteins Depends on Annexin 13

In the present study, we assessed the role of annexin 13 membrane-binding protein (ANXA13) in the intracellular transport of vesicles containing type II ribosome-inactivating proteins (RIP-IIs). A modified human intestinal epithelial cell line HT29 was used, in which the expression of ANXA13 was significantly reduced. The cytotoxic effect of ricin and viscumin was evaluated by modification of 28S ribosome RNA. The observed differences in the activity of toxins on the parental and modified HT29 lines indicate that ANXA13 plays a different role in the intracellular transport of vesicles containing the RIP-IIs.

Relationship between the Expression Level of PSMD11 and Other Proteasome Proteins with the Activity of Ricin and Viscumin

The role of proteasome proteins and proteins of the ERAD system in the cytotoxicity of type II ribosome-inactivating proteins ricin and viscumin was investigated. For this, the cell line of colorectal adenocarcinoma HT29, as well as the HT29-sh002 line obtained on its basis, were used. On the basis on the proteome analysis of these lines and the estimation of the proportion of inactivated ribosomes, it was shown that the contribution of the proteasome to the degradation of the catalytic subunits of toxins is different. The role of the Cdc37 co-chaperone in maintaining the stability of A subunit of viscumin in the cytoplasm is shown.

Differences in the Drosha and Dicer Cleavage Profiles in Colorectal Cancer and Normal Colon Tissue Samples

Human colorectal adenocarcinoma cell line Caco-2 is often used as a model of healthy intestinal epithelium, in particular, in miRNA studies. The work of the enzymes Drosha and Dicer is an integral part of the process of miRNA formation. Inaccuracies in the work of these enzymes lead to a change in the nucleotide sequences of miRNAs with the formation of new isoforms, which, in turn, can change intracellular regulatory mechanisms. In the framework of this study, it was shown that the quantitative estimates of inaccuracies in Drosha and Dicer activity significantly differ between the specimens of normal colon tissue and malignant colorectal tumors.

Hypoxia enhances transcytosis in intestinal enterocytes

The integrity of the intestinal epithelial cell lining is crucial for the normal intestinal function. As a rule, intestinal inflammation is associated with additional tissue hypoxia, leading to the loss of epithelial monolayer integrity. However, in the absence of visible damage to the epithelium, there still might be a risk of infection driven by changes in the intracellular transport of bacteria-containing vesicles. The aim of this study was to investigate the effects of hypoxia on transcytosis using a human intestinal enterocyte model. We found that hypoxia enhances transcytosis of the model protein ricin 1.8-fold. The comparative transcriptome and proteome analyses revealed significant changes in the expression of genes involved in intracellular vesicle transport. Specifically, the expression of apoB (the regulator of lipid metabolism) was changed at both protein (6.5-fold) and mRNA (2.1-fold) levels. Further research is needed into the possible mechanism regulating gene expression in intestinal erythrocytes under hypoxic conditions.

[Epithelial to Mesenchymal Transition Marker in 2D and 3D Colon Cancer Cell Cultures in the Presence of Laminin 332 and 411]

Received August 28, 2018; revised October 10, 2018; accepted November 6, 2018 The loss of apical-basal cell polarity is a necessary stage of the epithelial-mesenchymal transition (EMT). Polarized epithelial cells interact with the basement membrane (BM) and, in particular, with laminins, the major components of BM. Here, we examined the effect of the transition of colon cancer cells from 2D polarized state to non-polarized 3D state on the expression of EMT associated genes, as well as the role of laminins 332 and 411 (LM-332 and LM-411) in this process. The three studied cell lines, HT-29, HCT-116 and RKO, were found to have different sensitivity to cultivation conditions (2D to 3D changes) and to addition of laminins. One of the possible reasons for this maybe a difference in the initial 2D state of the cells. In particular, it was shown that the cell lines were at different EMT stages. HT-29 exhibited more epithelial expression profile, RKO was more mesenchymal, and HCT-116 was in an intermediate state. The most laminin-sensitive cell line was HCT-116. The magnitude and the specificity of cell response to LM-332 and LM-411 depended on the expression pattern of laminins' receptors. EMT gene expression profile was not substantially changed neither during the transition from 2D to 3D state, nor the presence of laminins' isoforms. However, we detected changes in expression of SNAI1 and ZEB1 genes encoding transcription factors that control the EMT process. Notably, in all three studied cell lines, the expression of SNAI1 was enhanced in response to laminin treatment.

[Laminins in Metastatic Cancer]

Laminins are a family of extracellular heterotrimeric glycoproteins that are the main structural component of basement membranes (BMs), perform a barrier function, and are important for adhesion, differentiation, migration, and resistance to apoptosis of various cells, including cancer cells. The review summarizes the current knowledge of how laminins produced by cancer and normal cells influence the key stages of carcinogenesis. Laminin 332 (LN-332) and LN-111 enhance proliferation of certain cancer cells and increase the tumour growth. LN-111 increases resistance to apoptosis, induces differentiation, and inhibits the epithelial-mesenchymal transition (EMT) of cancer cells. LN-332 is associated with higher adhesion and higher migration potential of cancer cells. LN-411 and LN-421 significantly increase motility of cancer cells. LN-332 and LN-511 facilitate cell-cell adhesion and affect the efficacy of cell-cell interactions. The laminin chains α4 and α5 are important for the development and function of blood and lymphatic vessels. The expression ratio of the α4 and α5 laminin chains defines the BM permeability to leukocytes and, presumably, cancer cells in blood and lymphatic vessels. Interactions between LN-511 and α2-containing laminins enhance self-renewal and survival of circulating cancer stem cells. Moreover, laminins are involved in the formation of premetastatic niches and new colonies. Endogenous expression of the α4 laminin chain stimulates proliferation of individualised circulating cancer cells in vitro and in vivo and facilitates micrometastasis.

[Expression of Stroma Components in the Lymph Nodes Affected by Prostate Cancer Metastases]

The architecture of stroma is crucial for normal lymph node functioning, as well as for the systemic and local immune response. Data from previous studies in metastatic lymph nodes suggest that changes in the composition of extracellular matrix proteins may occur, not only around the lesion site, but throughout the lymph node stroma. In the present study, the extracellular matrix status was compared between the affected and metastasis-free lymph nodes in prostate cancer. It was found that the presence of tumor cells was associated with significant changes in the expression of genes encoding extracellular matrix components, including α4, β1 and γl laminin chains, osteonectin, and collagen, as well as with decrease in the expression of lymphatic endothelial cell biomarkers LYVE1 and NRP2. This result suggests that the normal stromal architecture is significantly disrupted in metastatic lymph nodes and may indicate the development of immune tolerance to the tumor cells.

[Ribosome Inactivation and the Integrity of the Intestinal Epithelial Barrier]

The mistletoe lectin viscumin (MLI) is a ribosome-inactivating protein from Viscum album widely used in cancer therapy. Its antitumor properties are due to its immunomodulating action, previously demonstrated in experiments involving intravenous, subcutaneous, and oral administration of viscumin. To investigate whether viscumin has a cytotoxic effect on the intestinal epithelium, its safety was assessed using (i) impedance spectroscopy to measure the integrity of the colorectal adenocarcinoma Caco-2 cell monolayer after exposure to viscumin and (ii) a novel technique of determining the portion of viscumin-inactivated ribosomes. It was shown that inactivation of at least 20% of the ribosomes within 6 h did not lead to disruption of the Caco-2 cell monolayer or alter the physicochemical parameters of enterocyte membranes.

Elimination of a Viscumin-Ferromagnetic Nanoparticles Conjugate from the Tumor Nodule in Mice

External magnetic field is characterized by low toxicity and existence of magnetic properties, which contributes to an interest in the development of products from ferromagnetic nanoparticles (FNP) for antitumor therapy. Previously we synthesized a conjugate of ferromagnetic magnetite nanoparticles and viscumin (mistletoe lectin I, MLI), which exhibits the antitumor activity. Studying the pharmacological properties of this conjugate (FNP-MLI) was directed to the evaluation of FNP-MLI elimination after intratumor injection in mice. The elimination rate of FNP-MLI was much lower than that of native plant MLI. The presence of FNP-MLI was not accompanied by undesired changes in the tumor tissue. The use of a FNP-MLI conjugate allowed us to prolong the time of MLI presence in tissues without increasing the dose of exogenous lectin. These features contribute to the prolongation of an immunomodulatory effect of MLI.

mRNA expression profile of mouse oligodendrocytes in inflammatory conditions

In this study, we performed transcriptome profiling of oligodendrocyte culture of mice treated with the remyelinating therapeutic agent benztropine in the presence and absence of interferon gamma (IFNγ). The results of this work are important for understanding the expression profile of oligodendrocytes under conditions of systemic inflammation in the central nervous system in multiple sclerosis as well as the mechanisms of cellular response to benztropine in light of its possible use for the treatment of multiple sclerosis.

p53- and Caspase-3-Independent Mechanism of Acetaminophen Effect on Human Neural Cells

Acetaminophen in a concentration of 5 mM increased the expression of JNK, HIF1A (hypoxiainduced factor), and CASP3, which indicated development of oxidative stress and apoptotic cell death. Acetaminophen in a concentration of 10 mM did not induce expression of HIF1A and CASP3, but reduced expression of chaperone HSP90, which attested to activation of a caspase-3-independent mechanism of cell death. The methods of preventing acetaminophen intoxication are discussed.

Force-extension curves for broken-rod macromolecules: Dramatic effects of different probing methods for two and three rods

We study force-extension curves of a single semiflexible chain consisting of several rigid rods connected by flexible spacers. The atomic force microscopy and laser optical or magnetic tweezers apparatus stretching these rod-coil macromolecules are discussed. In addition, the stretching by external isotropic force is analyzed. The main attention is focused on computer simulation and analytical results. We demonstrate that the force-extension curves for rod-coil chains composed of two or three rods of equal length differ not only quantitatively but also qualitatively in different probe methods. These curves have an anomalous shape for a chain of two rods. End-to-end distributions of rod-coil chains are calculated by Monte Carlo method and compared with analytical equations. The influence of the spacer's length on the force-extension curves in different probe methods is analyzed. The results can be useful for interpreting experiments on the stretching of rod-coil block-copolymers.