Synchronization of some human cell strains by serum and calcium starvation

The Impact of Microelectrode Pattern on the Sensitivity of Tracing Environmental CO2 Deficiency in Cellular Metabolism by a New Design of Electrochemical Biosensor

Here, two different electrode patterns are described as cyclic voltammetry (CV) biosensors to detect the effect of a hypo CO2 condition (for 6 h) in ambient on cellular secretion. The cells were selected from breast cancer and endothelial standard lines. Changes in CV peaks of the secretions were recorded by the modified pattern whereby increasing the interactive surface with homogenous electric paths was considered by simulation before fabrication. The results of the simulation and experimental procedures showed a meaningful correlation between hypo CO2 samples and the occurrence of CV oxidative peaks at about 0.07 V and reductive peaks at approximately -0.22 V in the modified biosensor in all cell lines, while no apoptosis was found in any of the control and hypo CO2 samples. This observation could not be related to the lack of H+ (alkaline pH induction) in the media solution as such peaks were not observed in the pure cell culture medium but had been maintained in the hypo CO2 ambient. This approach could be used as a cell-free sensor to monitor ambient shocks. This may not induce apoptosis but may be vital in the proliferation and protein expression of the cells, such as the hypo CO2 ambient. The sensor is not disposable in use and showed repeatable responses after rinsing.

Cell Cycle Synchronization of the Murine EO771 Cell Line Using Double Thymidine Block Treatment

This study shows that double thymidine block treatment efficiently arrests the EO771 cells in the S-phase without altering cell growth or survival. A long-term analysis of cell behavior, using 5(6)-carboxyfluorescein diacetate N-succinimidyl ester (CFSE) staining, show synchronization to be stable and consistent over time. The EO771 cell line is a medullary breast-adenocarcinoma cell line isolated from a spontaneous murine mammary tumor, and can be used to generate murine tumor implantation models. Different biological (serum or amino acid deprivation), physical (elutriation, mitotic shake-off), or chemical (colchicine, nocodazole, thymidine) treatments are widely used for cell synchronization. Of the different methods tested, the double thymidine block is the most efficient for synchronization of murine EO771 cells if a large quantity of highly synchronized cells is recommended to study functional and biochemical events occurring in specific points of cell cycle progression.

Nck1 promotes the progression of ovarian carcinoma by enhancing the PI3K/AKT/p70S6K signaling

Non-catalytic region of tyrosine kinase adaptor protein 1 (Nck1) is crucial for the progression of cancers. However, little is known on the role of Nck1 in the progression of ovarian carcinoma (OC). Here, we show that Nck1 expression is up-regulated in 176 OC tissues, compared with non-carcinoma ovarian tissues, and the up-regulated Nck1 expression is associated with the aggressiveness of OC and shorter overall and disease-free survival in this population. Higher Nck1 expression was an independent risk factor for poor prognosis of OC. Furthermore, Nck1 silencing by short hairpin RNA (shRNA) technology significantly inhibited the proliferation, migration and invasion of OC cells in vitro and the growth and metastasis of implanted OC tumors in vivo. Human kinase phosphorylation array indicated that Nck1 silencing significantly reduced the relative levels of 11 kinase expression and phosphorylation in OC cells, particularly for decreased levels of p70S6 kinase (p70S6K) and protein kinase B (AKT) expression in SKOV3 cells. Actually, Nck1 silencing significantly decreased PI3K and AKT expression, and reduced AKT and p70S6K phosphorylation while Nck1 over-expression had opposite effects in OC cells. Therefore, our data indicate that Nck1 promotes the progression of OC by enhancing the PI3k/AKT/p70S6K signaling in OC. Our findings suggest that Nck1 expression may be valuable for evaluating the prognosis of OC and as a target for design of new therapies for OC.

Quaking orchestrates a post-transcriptional regulatory network of endothelial cell cycle progression critical to angiogenesis and metastasis

Angiogenesis is critical to cancer development and metastasis. However, anti-angiogenic agents have only had modest therapeutic success, partly due to an incomplete understanding of tumor endothelial cell (EC) biology. We previously reported that the microRNA (miR)-200 family inhibits metastasis through regulation of tumor angiogenesis, but the underlying molecular mechanisms are poorly characterized. Here, using integrated bioinformatics approaches, we identified the RNA-binding protein (RBP) quaking (QKI) as a leading miR-200b endothelial target with previously unappreciated roles in the tumor microenvironment in lung cancer. In lung cancer samples, both miR-200b suppression and QKI overexpression corresponded with tumor ECs relative to normal ECs, and QKI silencing phenocopied miR-200b-mediated inhibition of sprouting. Additionally, both cancer cell and endothelial QKI expression in patient samples significantly corresponded with poor survival and correlated with angiogenic indices. QKI supported EC function by stabilizing cyclin D1 (CCND1) mRNA to promote EC G1/S cell cycle transition and proliferation. Both nanoparticle-mediated RNA interference of endothelial QKI expression and palbociclib blockade of CCND1 function potently inhibited metastasis in concert with significant effects on tumor vasculature. Altogether, this work demonstrates the clinical relevance and therapeutic potential of a novel, actionable miR/RBP axis in tumor angiogenesis and metastasis.

Stem cell factor and NSC87877 synergism enhances c-Kit mediated proliferation of human erythroid cells

The biological mechanisms underlying the effects of stem cell factor (SCF) and an inhibitor, NSC87877 (N) of the c-Kit negative regulator (SHP-1 and SHP-2) on cell proliferation are different. Therefore, we compared the cell's response to these two either alone or in combination in K562 cells. Binding of SCF (S) to c-Kit induces dimerization that activates its kinase activity. The activated c-Kit undergoes autophosphorylation at tyrosine residues that serve as a docking site for signal transduction molecules containing SH2 domains. Predominantly, the phosphotyrosine 568 (pY568) in Juxtamembrane (JM) region of c-Kit interacts with adaptor protein APS, Src family kinase, and SHP-2, while phosphotyrosine 570 (pY570) interacts with the SHP-1 and the adaptor protein Shc. The dephosphorylation of phosphotyrosine residues by SHP-1/SHP-2 leads to inhibition of c-Kit proliferative signaling. A chemical molecule, N is reported to inhibit the enzymatic activity of SHP-1/SHP-2, but its effect on c-Kit-mediated proliferation has not been studied yet. Thus, this work aims at examining the effect of the combination of S and N on cells growth as compared to individual treatment. The present study is performed with erythroleukemic K562 cells, chosen for its mRNA expression concerning the c-Kit, and SHP-1/SHP-2. Interestingly, proliferation assay showed that combination significantly increased proliferation when G₁ sorted K562 cells were used. These changes were significantly higher when K562 cells were initially treated with N followed by S treatment. Collectively, these results give mechanistic insight into the proliferation enhancement of bone marrow transplantation through the synergistic effect of S and N by inhibiting SHP-1/SHP-2. The study gives solid evidence that S and N combination can be used to enhance cell proliferation/growth.

'MCC' protein interacts with E-cadherin and β-catenin strengthening cell-cell adhesion of HCT116 colon cancer cells

E-cadherin and β-catenin are key proteins that are essential in the formation of the epithelial cell layer in the colon but their regulatory pathways that are disrupted in cancer metastasis are not completely understood. Mutated in colorectal cancer (MCC) is a tumour suppressor gene that is silenced by promoter methylation in colorectal cancer and particularly in patients with increased lymph node metastasis. Here, we show that MCC methylation is found in 45% of colon and 24% of rectal cancers and is associated with proximal colon, poorly differentiated, circumferential and mucinous tumours as well as increasing T stage and larger tumour size. Knockdown of MCC in HCT116 colon cancer cells caused a reduction in E-cadherin protein level, which is a hallmark of epithelial-mesenchymal transition in cancer, and consequently diminished the E-cadherin/β-catenin complex. MCC knockdown disrupted cell-cell adhesive strength and integrity in the dispase and transepithelial electrical resistance assays, enhanced hepatocyte growth factor-induced cell scatter and increased tumour cell invasiveness in an organotypic assay. The Src/Abl inhibitor dasatinib, a candidate anti-invasive drug, abrogated the invasive properties induced by MCC deficiency. Mechanistically, we establish that MCC interacts with the E-cadherin/β-catenin complex. These data provide a significant advance in the current understanding of cell-cell adhesion in colon cancer cells.

Histone methyltransferase Setd2 is critical for the proliferation and differentiation of myoblasts

Skeletal muscle cell proliferation and differentiation are tightly regulated. Epigenetic regulation is a major component of the regulatory mechanism governing these processes. Histone modification is part of the epigenetic code used for transcriptional regulation of chromatin through the establishment of an active or repressive state for genes involved in myogenesis in a temporal manner. Here, we uncovered the function of SET domain containing 2 (Setd2), an essential histone 3 lysine 36 trimethyltransferase, in regulating the proliferation and differentiation of myoblasts. Setd2 was silenced in the skeletal muscle myoblast cell line, C2C12, using the CRISPR/CAS9 system. The mutant cells exhibited defect in myotube formation. The myotube formation marker, myosin heavy chain (MHC), was downregulated earlier in Setd2 silenced cells compared to wild-type myoblasts during differentiation. The deficiency in Setd2 also resulted in repression of Myogenin (MyoG) expression, a key myogenic regulator during differentiation. In addition to the myoblast differentiation defect, decreased proliferation rate with significantly reduced levels of histone 3 phosphorylation, indicative of cell proliferation defect, were observed in the Setd2 silenced cells; suggesting an impaired proliferation phenotype. Furthermore, compromised G1/S- and G2/M-phase transition and decreased expression levels of major regulators of cell cycle G1/S checkpoints, cyclin D1, CDK4, CDK6, and cyclin E2 were detected in Setd2 silenced cells. Consistent with the cell cycle arrested phenotype, cyclin-dependent kinase inhibitor p21 was upregulated in Setd2 silenced cells. Together, this study demonstrates an essential role of Setd2 in myoblast proliferation and differentiation, and uncovers Setd2-mediated molecular mechanism through regulating MyoG and p21.

Quercetin-induced miR-200b-3p regulates the mode of self-renewing divisions in pancreatic cancer

BACKGROUND

Cancer stem cells are suggested to contribute to the extremely poor prognosis of pancreatic ductal adenocarcinoma and dysregulation of symmetric and asymmetric stem cell division may be involved. Anticancer benefits of phytochemicals like the polyphenol quercetin, present in many fruits, nuts and vegetables, could be expedited by microRNAs, which orchestrate cell-fate decisions and tissue homeostasis. The mechanisms regulating the division mode of cancer stem cells in relation to phytochemical-induced microRNAs are poorly understood.

METHODS

Patient-derived pancreas tissue and 3 established pancreatic cancer cell lines were examined by immunofluorescence and time-lapse microscopy, microRNA microarray analysis, bioinformatics and computational analysis, qRT-PCR, Western blot analysis, self-renewal and differentiation assays.

RESULTS

We show that symmetric and asymmetric division occurred in patient tissues and in vitro, whereas symmetric divisions were more extensive. By microarray analysis, bioinformatics prediction and qRT-PCR, we identified and validated quercetin-induced microRNAs involved in Notch signaling/cell-fate determination. Further computational analysis distinguished miR-200b-3p as strong candidate for cell-fate determinant. Mechanistically, miR-200b-3p switched symmetric to asymmetric cell division by reversing the Notch/Numb ratio, inhibition of the self-renewal and activation of the potential to differentiate to adipocytes, osteocytes and chondrocytes. Low miR-200b-3p levels fostered Notch signaling and promoted daughter cells to become symmetric while high miR-200b-3p levels lessened Notch signaling and promoted daughter cells to become asymmetric.

CONCLUSIONS

Our findings provide a better understanding of the cross talk between phytochemicals, microRNAs and Notch signaling in the regulation of self-renewing cancer stem cell divisions.

DNA Damage Response Resulting from Replication Stress Induced by Synchronization of Cells by Inhibitors of DNA Replication: Analysis by Flow Cytometry

Cell synchronization is often achieved by transient inhibition of DNA replication. When cultured in the presence of such inhibitors as hydroxyurea, aphidicolin or excess of thymidine the cells that become arrested at the entrance to S-phase upon release from the block initiate progression through S then G₂ and M. However, exposure to these inhibitors at concentrations commonly used to synchronize cells leads to activation of ATR and ATM protein kinases as well as phosphorylation of Ser139 of histone H2AX. This observation of DNA damage signaling implies that synchronization of cells by these inhibitors is inducing replication stress. Thus, a caution should be exercised while interpreting data obtained with use of cells synchronized this way since they do not represent unperturbed cell populations in a natural metabolic state. This chapter critically outlines virtues and vices of most cell synchronization methods. It also presents the protocol describing an assessment of phosphorylation of Ser139 on H2AX and activation of ATM in cells treated with aphidicolin, as a demonstrative of one of several DNA replication inhibitors that are being used for cell synchronization. Phosphorylation of Ser139H2AX and Ser1981ATM in individual cells is detected immunocytochemically with phospho-specific Abs and intensity of immunofluorescence is measured by flow cytometry. Concurrent measurement of cellular DNA content followed by multiparameter analysis allows one to correlate the extent of phosphorylation of these proteins in response to aphidicolin with the cell cycle phase.

Recombinant human beta 2-defensin fusion proteins as a tool to investigate defensin structure and function in small human intestinal tissue samples

OBJECTIVE

Effects of immune cells on the beta 2 (β2)-defensin (HBD2) expression and its antibacterial activity in the intestinal mucosa of patients with inflammatory bowel diseases remains unclear. The small size of these proteins presents a major challenge in localizing antibacterial activities in human intestinal tissue. In this study, we evaluated the detection limits at mRNA and protein level by approaching HBD2 from small tissue samples.

METHODS

HT-29 colonic epithelial cells were incubated with proinflammatory cytokines before HBD2 mRNA was investigated by quantitative polymerase chain reaction. The HBD2 protein was assessed by Western blot analysis using HBD2 fused with enhanced green fluorescent protein (HBD2-EGFP). Purified HBD2 fused with the glutathione-S-transferase (GST-HBD2) was used to detect antibacterial activity in a densitometric assay.

RESULTS

Interleukin (IL)-1β induced HBD2 mRNA in HT-29 cells; however, tumor necrosis factor-α, IL-6 and IL-17 did not. The Western blot had a sensitivity of 1.5 pmol to detect recombinant HBD2, but did not detect HBD2 in either human intestinal or IL-1β-treated HT-29 cells. HBD2-EGFP was detected by HBD2-specific Western blot within cell lysates and culture supernants of transfected HT-29 and primary cells. In nanomolar ranges, GST-HBD2 reduced bacterial growth. The HBD2 bioactivity depended on solution conditions, but not on the size of the fusion partner.

CONCLUSION

The established fusion proteins provide excellent tools to evaluate expression patterns and antibacterial effects of HBD2 in human intestinal tissue samples.

High-throughput cell cycle synchronization using inertial forces in spiral microchannels

Efficient synchronization and selection of cells at different stages of the cell replication cycle facilitates both fundamental research and development of cell cycle-targeted therapies. Current chemical-based synchronization methods are unfavorable as these can disrupt cell physiology and metabolism. Microfluidic systems developed for physical cell separation offer a potential alternative over conventional cell synchronization approaches. Here we introduce a spiral microfluidic device for cell cycle synchronization, using the combined effects of inertial forces and Dean drag force. By exploiting the relationship between cell diameter and cell cycle (DNA content/ploidy), we have successfully fractionated several asynchronous mammalian cell lines, as well as primary cells comprising bone marrow-derived human mesenchymal stem cells (hMSCs), into enriched subpopulations of G0/G1 (>85%), S, and G2/M phases. This level of cell cycle enrichment is comparable to existing microfluidic systems, but the throughput (∼ 15 × 10(6) cells per h) and viability (∼ 95%) of cells thus synchronized are significantly greater. Further, this platform provides rapid collection of synchronized cells or of diameter-sorted cells post-separation, to enable diverse applications in the study and manipulation of cell proliferation.

Cell synchronization by inhibitors of DNA replication induces replication stress and DNA damage response: analysis by flow cytometry

Cell synchronization is often achieved by inhibition of DNA replication. The cells cultured in the presence of such inhibitors as hydroxyurea, aphidicolin, or thymidine become arrested at the entrance to S phase and upon release from the block they synchronously progress through S, G(2), and M. We recently reported that exposure of cells to these inhibitors at concentrations commonly used to synchronize cell populations led to phosphorylation of histone H2AX on Ser139 (induction of γH2AX) through activation of ataxia telangiectasia mutated and Rad3-related protein kinase (ATR). These findings imply that the induction of DNA replication stress by these inhibitors activates the DNA damage response signaling pathways and caution about interpreting data obtained with use of cells synchronized such way as representing unperturbed cells. The protocol presented in this chapter describes the methodology of assessment of phosphorylation of histone H2AX-Ser139, ATM/ATR substrate on Ser/Thr at SQ/TQ cluster domains as well as ataxia telangiectasia mutated (ATM) protein kinase in cells treated with inhibitors of DNA replication. Phosphorylation of these proteins is detected in individual cell immunocytochemically with phospho-specific antibody (Ab) and measured by flow cytometry. Concurrent measurement of cellular DNA content and phosphorylated proteins followed by multiparameter cytometric analysis allows one to correlate extent of their phosphorylation with cell cycle phase.

Synchronization in the cell cycle by inhibitors of DNA replication induces histone H2AX phosphorylation: an indication of DNA damage

Several methods to synchronize cultured cells in the cell cycle are based on temporary inhibition of DNA replication. Previously it has been reported that cells synchronized this way exhibited significant growth imbalance and unscheduled expression of cyclins A and B1. We have now observed that HL-60 cells exposed to inhibitors of DNA replication (thymidine, aphidicolin and hydroxyurea), at concentrations commonly used to synchronize cell populations, had histone H2AX phosphorylated on Ser-139. This modification of H2AX, a marker of DNA damage (induction of DNA double-strand breaks; DSBs), was most pronounced in S-phase cells, and led to their apoptosis. Thus, to a large extent, synchronization was caused by selective kill of DNA replicating cells through induction of replication stress. In fact, similar synchronization has been achieved by exposure of cells to the DNA topoisomerase I inhibitor camptothecin, a cytotoxic drug known to target S-phase cells. A large proportion of the surviving cells 'synchronized' by DNA replication inhibitors at the G1/S boundary had phosphorylated histone H2AX. Inhibitors of DNA replication, thus, not only selectively kill DNA replicating cells, induce growth imbalance and alter the machinery regulating progression through the cycle, but they also cause DNA damage involving formation of DSBs in the surviving ('synchronized') cells. The above effects should be taken into account when interpreting data obtained with the use of cells synchronized by inhibitors of DNA replication.

RNAi-mediated depletion of the 15 KH domain protein, vigilin, induces death of dividing and non-dividing human cells but does not initially inhibit protein synthesis

Vigilin/Scp160p/DDP1 is a ubiquitous and highly conserved protein containing 15 related, but non-identical, K-homology (KH) nucleic acid binding domains. While its precise function remains unknown, proposed roles for vigilin include chromosome partitioning at mitosis, facilitating translation and tRNA transport, and control of mRNA metabolism, including estrogen-mediated stabilization of vitellogenin mRNA. To probe sites of vigilin action in vertebrate cells, we performed nucleic acid binding and RNA interference studies. Consistent with a potential role in chromosome partitioning, human vigilin exhibits a higher affinity for Drosophila dodecasatellite single-stranded DNA than for vitellogenin mRNA 3'-UTR. Direct observation and flow cytometry in non-mitotic, serum-starved, HeLa cells showed that RNAi-mediated vigilin knockdown is rapidly lethal, indicating an essential function for vigilin distinct from its proposed role in chromosome partitioning. Pulse labeling experiments revealed that rates of protein synthesis and degradation are unaffected by the several fold reduction in vigilin levels early in siRNA knockdown indicating that vigilin is not a global regulator of translation. These data show that vigilin is an essential protein in human cells, support the view that vigilin's most essential functions are neither chromosome partitioning nor control of translation, and are consistent with vigilin playing a critical role in cytoplasmic mRNA metabolism.