Comparative proteomic analysis of anti-benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide-transformed and normal human bronchial epithelial G0/G1 cells

The Circ_CARM1 controls cell migration by regulating CTNNBIP1 in anti-benzo[a]pyrene-trans-7,8-dihydrodiol-9,10-epoxide-transformed 16HBE cells

BACKGROUND

Circular RNAs (circRNAs) have an important role in the development and progression of human tumors, including lung cancer. Yet, their role in lung cancer induced by benzo(a)pyrene (B[a]P) remains unclear. In this study, circRNA chips and qRT-PCR were used to examine downregulated circRNAs in malignantly transformed 16HBE cells (16HBE-T) induced by B[a]P. Five down-regulated circRNAs were found, among which hsa_circ_0004552 (circ_CARM1) had the most significant downregulation. Consequently, the role of circ_CARM1 on 16HBE-T cells biological behavior was further examined using several in vitro experiments.

MATERIALS AND METHODS

Detecting RNA expression via qRT-PCR. Fluorescence in situ hybridization (FISH) was used to identify the localization of circ_CARM1 in 16HBE-T. The effect of circ_CARM1 on cell behavior (cell migration, proliferation, and apoptosis) was explored by transfecting cells with a vector carrying an overexpression and then using wound healing, transwell migration assay, and flow cytometry. Also, the regulation mechanism for circ_CARM1, miR-1288-3p, and CTNNBIP1 was studied by Dual-Luciferase® Reporter (DLR™) Assay System and western blotting.

RESULTS

Reduced expression of circ_CARM1 is observed in 16HBE-T. The overexpression of circ_CARM1 further inhibited the migration of 16HBE-T cells but did not affect cell proliferation and apoptosis. Furthermore, bioinformatic analysis and Dual-Luciferase® Reporter (DLR™) Assay System showed that the competitive binding of circ_CARM1 and miR-1288-3p enhanced the expression of CTNNBIP1, thereby inhibiting the migration of 16HBE-T cells.

CONCLUSION

Downregulation of circ_CARM1 can stimulate the expression of miR-1288-3p, thereby reducing the expression of CTNNBIP1, spurring cell migration.

Emerging roles of long non-coding RNAs in the toxicology of environmental chemicals

Environmental chemicals (ECs) are drawing great attention to their effects on health and their toxicological mechanisms are being investigated. Long non-coding RNA (lncRNA) is a class of RNA with more than 200 nucleotides and does not have protein coding potential. Recently, it is emerging as a star molecule that participates in a wide range of physiological and pathological processes. It has been reported to be abnormally expressed in diseases. As an epigenetic factor, lncRNAs play an important role in the response of organisms to environmental stress. Their roles in the toxicity of ECs are being identified. Altered expression profiles of lncRNAs have been explored after exposure to ECs. Various kinds of ECs are reported to disturb the expression of lncRNAs in vitro and in vivo. Then, dysregulated lncRNAs can affect the expression of target genes directly or indirectly via regulating the level of microRNAs. The network among lncRNAs, microRNAs and mRNAs can initiate or impede specific signaling pathway and lead to adverse outcome upon exposure to ECs. Recovery of the lncRNAs level by overexpression or knockdown technology diminished the effect induced by ECs. In the review, biological roles of lncRNAs are depicted. The lncRNAs involved in the toxicology are summarized. Types of ECs that have been reported to affect the expression of lncRNAs are categorized. The interaction between various types of ECs and lncRNAs is discussed.

Opposite effects of tumor protein D (TPD) 52 and TPD54 on oral squamous cell carcinoma cells

The tumor protein D52 (TPD52) protein family includes TPD52, -53, -54 and -55. Several reports have shown important roles for TPD52 and TPD53, and have also suggested the potential involvement of TPD54, in D52-family physiological effects. Therefore, we performed detailed expression analysis of TPD52 family proteins in oral squamous cell carcinoma (OSCC). Towards this end, TPD54-overexpressing or knocked-down cells were constructed using OSCC-derived SAS, HSC2 and HSC3 cells. tpd52 or tpd53 was expressed or co-expressed in these cells by transfection. The cells were then analyzed using cell viability (MTT), colony formation, migration, and invasion assays. In OSCC-xenograft experiments, the cells were transplanted into nude mice together with injection of anti-tpd siRNAs. MTT assay of cell monolayers showed little differences in growth of the transfected cells. tpd54 overexpression in SAS cells significantly decreased colony formation in an anchorage-independent manner. Additionally, knock-down of tpd54 enhanced the number of colonies formed and overexpression of tpd52 in tpd54 knock-down cells increased the size of the colonies formed. The chemotaxis assay showed that tpd54 overexpression decreased cell migration. In the OSCC-xenograft in vivo study, tpd54 overexpression slightly attenuated tumor volume in vivo, despite the fact that tumor metastasis or cell survival was not involved. Our results showed that TPD54 not only downregulated anchorage-independent growth and cell migration in vitro, but also attenuated tumor growth in vivo. Based on these results, it is considered that TPD54 might act as a negative regulator of tumor progression in OSCC cells.

Label-free quantitative proteomic analysis of benzo(a)pyrene-transformed 16HBE cells serum-free culture supernatant and xenografted nude mice sera

To screen potential biomarkers of benzo(a)pyrene (BaP)-induced lung cancer, the proteomic profiles of BaP-transformed 16HBE cell line T-16HBE-C1 cells serum-free culture supernatant and xenografted nude mice sera were compared with those of 16HBE group by utilizing label-free quantitative proteomic strategy. By employing nano-LC-MS/MS technology followed by MaxQuant and Perseus processing, 489 differentially expressed proteins were identified between T-16HBE-C1 and 16HBE cells serum-free culture supernatant, and 49 significantly up-regulated proteins were identified in T-16HBE-C1 xenografted nude mice sera. Three proteins neuropilin-2 (NRP2), clusterin (CLU) and A-kinase anchor protein 12 (AKAP12) were up-regulated in the serum-free culture supernatant of T-16HBE-C1 cells. These 3 human proteins were present in the sera of nude mice xenografted with T-16HBE-C1 cells, but were undetectable in mice xenografted with 16HBE cells. The proteomic results of NRP2 and AKAP12 were confirmed by Western blotting and enzyme-linked immunosorbent assays, respectively. Moreover, the serum NRP2 levels were significantly elevated at the 4th day after tumor cell implantation and showed good positive correlation with tumor growth characterized by tumor volume. In conclusion, serum NRP2, CLU and AKAP12 could be potential biomarkers of BaP-induced lung cancer. The proteomic results will gain deeper insights into the mechanisms of BaP-induced carcinogenesis.

Structural basis of Sorcin-mediated calcium-dependent signal transduction

Sorcin is an essential penta-EF hand calcium binding protein, able to confer the multi-drug resistance phenotype to drug-sensitive cancer cells and to reduce Endoplasmic Reticulum stress and cell death. Sorcin silencing blocks cell cycle progression in mitosis and induces cell death by triggering apoptosis. Sorcin participates in the modulation of calcium homeostasis and in calcium-dependent cell signalling in normal and cancer cells. The molecular basis of Sorcin action is yet unknown. The X-ray structures of Sorcin in the apo (apoSor) and in calcium bound form (CaSor) reveal the structural basis of Sorcin action: calcium binding to the EF1-3 hands promotes a large conformational change, involving a movement of the long D-helix joining the EF1-EF2 sub-domain to EF3 and the opening of EF1. This movement promotes the exposure of a hydrophobic pocket, which can accommodate in CaSor the portion of its N-terminal domain displaying the consensus binding motif identified by phage display experiments. This domain inhibits the interaction of sorcin with PDCD6, a protein that carries the Sorcin consensus motif, co-localizes with Sorcin in the perinuclear region of the cell and in the midbody and is involved in the onset of apoptosis.

The potential for chemical mixtures from the environment to enable the cancer hallmark of sustained proliferative signalling

The aim of this work is to review current knowledge relating the established cancer hallmark, sustained cell proliferation to the existence of chemicals present as low dose mixtures in the environment. Normal cell proliferation is under tight control, i.e. cells respond to a signal to proliferate, and although most cells continue to proliferate into adult life, the multiplication ceases once the stimulatory signal disappears or if the cells are exposed to growth inhibitory signals. Under such circumstances, normal cells remain quiescent until they are stimulated to resume further proliferation. In contrast, tumour cells are unable to halt proliferation, either when subjected to growth inhibitory signals or in the absence of growth stimulatory signals. Environmental chemicals with carcinogenic potential may cause sustained cell proliferation by interfering with some cell proliferation control mechanisms committing cells to an indefinite proliferative span.

Molecular mechanisms of nasal epithelium in rhinitis and rhinosinusitis

Allergic rhinitis, nonallergic rhinitis, and chronic rhinosinusitis are multifactorial upper airway diseases with high prevalence. Several genetic and environmental factors are proposed to predispose to the pathogenesis of the inflammatory upper airway diseases. Still, the molecular mechanisms leading toward the onset and progression of upper airway diseases are largely unknown. The upper airway epithelium has an important role in sensing the environment and regulating the inhaled air. As such, it links environmental insults to the host immunity. Human sinonasal epithelium serves as an excellent target for observing induced early-phase events, in vivo, and with a systems biological perspective. Actually, increasing number of investigations have provided evidence that altered homeostasis in the sinonasal epithelium might be important in the chronic upper airway inflammation.

Oncogenic role of long noncoding RNA AF118081 in anti-benzo[a]pyrene-trans-7,8-dihydrodiol-9,10-epoxide-transformed 16HBE cells

Lung cancer is the leading cause of cancer deaths and remains an important public health problem worldwide. Long noncoding RNAs (lncRNAs) are newly identified regulators of tumorigenesis and tumor progression. However, the role of lncRNAs in lung cancer induced by environmental carcinogens remains largely unknown. In this study, an lncRNA microarray was used to compare the expression profiles of malignantly transformed 16HBE cells (16HBE-T) induced with anti-benzo[a]pyrene-trans-7,8-diol-9,10-epoxide (anti-BPDE) and normal 16HBE cells (16HBE-N). Using quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR), lncRNA AF118081 was identified as the most significantly overexpressed lncRNA in 16HBE-T cells, lung cancer cells, and patient samples. Cell proliferation, colony formation, apoptosis, migration, and invasion were assayed in 16HBE-T cells following the knockdown of lncRNA AF118081 with small interfering RNA. AF118081 knockdown inhibited cell growth and tumor invasion. An in vivo (nude mouse) model was then used to assay tumor growth, and the downregulation of AF118081 clearly suppressed tumor growth, consistent with the results of the in vitro assays. Together, these findings identify a new oncogenic lncRNA, lncRNA AF118081, in malignantly transformed 16HBE cells. This enhances our understanding of lncRNAs as important regulatory elements in chemical carcinogenesis and potential targets of lung cancer therapies.

Tumor protein D52 (TPD52) and cancer-oncogene understudy or understudied oncogene?

The Tumor protein D52 (TPD52) gene was identified nearly 20 years ago through its overexpression in human cancer, and a substantial body of data now strongly supports TPD52 representing a gene amplification target at chromosome 8q21.13. This review updates progress toward understanding the significance of TPD52 overexpression and targeting, both in tumors known to be characterized by TPD52 overexpression/amplification, and those where TPD52 overexpression/amplification has been recently or variably reported. We highlight recent findings supporting microRNA regulation of TPD52 expression in experimental systems and describe progress toward deciphering TPD52's cellular functions, particularly in cancer cells. Finally, we provide an overview of TPD52's potential as a cancer biomarker and immunotherapeutic target. These combined studies highlight the potential value of genes such as TPD52, which are overexpressed in many cancer types, but have been relatively understudied.

Sorcin links calcium signaling to vesicle trafficking, regulates Polo-like kinase 1 and is necessary for mitosis

Sorcin, a protein overexpressed in many multi-drug resistant cancers, dynamically localizes to distinct subcellular sites in 3T3-L1 fibroblasts during cell-cycle progression. During interphase sorcin is in the nucleus, in the plasma membrane, in endoplasmic reticulum (ER) cisternae, and in ER-derived vesicles localized along the microtubules. These vesicles are positive to RyR, SERCA, calreticulin and Rab10. At the beginning of mitosis, sorcin-containing vesicles associate with the mitotic spindle, and during telophase are concentrated in the cleavage furrow and, subsequently, in the midbody. Sorcin regulates dimensions and calcium load of the ER vesicles by inhibiting RYR and activating SERCA. Analysis of sorcin interactome reveals calcium-dependent interactions with many proteins, including Polo-like kinase 1 (PLK1), Aurora A and Aurora B kinases. Sorcin interacts physically with PLK1, is phosphorylated by PLK1 and induces PLK1 autophosphorylation, thereby regulating kinase activity. Knockdown of sorcin results in major defects in mitosis and cytokinesis, increase in the number of rounded polynucleated cells, blockage of cell progression in G2/M, apoptosis and cell death. Sorcin regulates calcium homeostasis and is necessary for the activation of mitosis and cytokinesis.

The cell cycle distribution should be given more consideration in cell-based in vitro toxicological studies

In this study, to discuss the importance of the cell cycle distribution in cell-based in vitro toxicity mechanism studies, diethyl sulfate (DES) was selected as a model chemical that induced the alteration of the cell cycle distribution in human bronchial epithelial cell line 16HBE 14o- (HBE) cells. Cells were treated with various concentrations of DES, cell proliferation and apoptosis were then determined. The results showed that DES concentration-dependently inhibited HBE cells proliferation and induced apoptosis. When cells were treated with 2.0 mM of DES for 20 or 28 h, significant S and G2/M phase accumulation was observed. Then, the relative cellular levels of Cdk4, p-Cdk2 (Thr160), Cyclins A and B1 in DES-treated HBE cells at 20 and 28 h were determined by two ways. The differences of the cell cycle distribution between DES and control groups were ignored in one way and eliminated by using flow cytometric cell sorting in the other. The results obtained by the two ways were quite different, which indicated that the cell cycle distribution might result in confounding if it was significantly different between the treated and control groups. Therefore, we propose that the cell cycle distribution should be given more consideration in cell-based in vitro toxicological studies.

Diethyl sulfate-induced cell cycle arrest and apoptosis in human bronchial epithelial 16HBE cells

In this study, we investigated the effects of diethyl sulfate (DES) on cell proliferation, cell cycle progression and apoptosis in human bronchial epithelial 16HBE cells. Cells were treated with various doses of DES (0, 0.5, 1.0, 2.0, 4.0 or 8.0mM) for 12, 24 or 36h. Cell proliferation and apoptosis were determined by MTT assay and flow cytometer, respectively. The results showed that DES inhibited cell proliferation in a dose- and time-dependent manner, and induced significant apoptosis in 16HBE cells. Apoptosis related proteins measurement results revealed that DES-induced apoptosis was concurrent with the increasing of Bax and cleavage fragment caspase-3 and the decreasing of Bcl-2 and full length procaspase-3. When cells were incubated with 2.0mM of DES for several time intervals, S and G2/M phase accumulation was observed. Further analysis indicated that both DES-induced G1/S transition acceleration and S arrest resulted in S phase accumulation, and that DES-induced G2/M arrest resulted in G2/M phase accumulation. Western blotting results demonstrated that after DES treatment p-chk1 (Ser345) and p-chk2 (Thr68) levels decreased in G1 cells, and increased in S and G2/M cells. In addition, the increasing of chk1 and chk2 were also induced by DES treatment. With the increase in the dose of DES, p53 levels first increased (0.5-4.0mM) and then decreased (8.0mM). Down-regulation of p53 by RNA interference increased 4.0mM of DES-induced apoptosis but did not affect 2.0mM DES-induced cell cycle arrest. In conclusion, DES inhibits 16HBE cells proliferation in a dose- and time-dependent behavior. Within the sublethal dose, DES induces S and G2/M arrest through activating DNA damage checkpoints. Within the lethal dose, DES induces apoptosis through evoking apoptosis programs. p53 might play an important role in the transition between evoking cell cycle arrest/pro-survival and apoptosis programs upon DES exposure.

Nuclear proteome analysis of benzo(a)pyrene-treated HeLa cells

Previously, we employed a proteomics-based 2-D gel electrophoresis assay to show that exposure to 10μM benzo(a)pyrene (BaP) during a 24 h frame can lead to changes in nuclear protein expression and alternative splicing. To further expand our knowledge about the DNA damage response (DDR) induced by BaP, we investigated the nuclear protein expression profiles in HeLa cells treated with different concentrations of BaP (0.1, 1, and 10μM) using this proteomics-based 2-D gel electrophoresis assay. We found 125 differentially expressed proteins in BaP-treated cells compared to control cells. Among them, 79 (63.2%) were down-regulated, 46 (36.8%) were up-regulated; 8 showed changes in the 1μM and 10μM BaP-treated groups, 2 in the 0.1μM and 10μM BaP-treated groups, 4 in the 0.1μM and 1μM BaP-treated groups, and only one showed changes in all three groups. Fifty protein spots were chosen for liquid chromatography-tandem mass spectrometry (LC-MS/MS) identification, and of these, 39 were identified, including subunits of the 26S proteasome and Annexin A1. The functions of some identified proteins were further examined and the results showed that they might be involved in BaP-induced DDR. Taken together, these data indicate that proteomics is a valuable approach in the study of environmental chemical-host interactions, and the identified proteins could provide new leads for better understanding BaP-induced mutagenesis and carcinogenesis.