Soft Agar Medium Research Articles

FlgV forms a flagellar motor ring that is required for optimal motility of Helicobacter pylori.

Flagella-driven motility is essential for Helicobacter pylori to colonize the human stomach, where it causes a variety of diseases, including chronic gastritis, peptic ulcer disease, and gastric cancer. H. pylori has evolved a high-torque-generating flagellar motor that possesses several accessories not found in the archetypical Escherichia coli motor. FlgV was one of the first flagellar accessory proteins identified in Campylobacter jejuni, but its structure and function remain poorly understood. Here, we confirm that deletion of flgV in H. pylori B128 and a highly motile variant of H. pylori G27 (G27M) results in reduced motility in soft agar medium. Comparative analyses of in-situ flagellar motor structures of wild-type, ΔflgV, and a strain expressing FlgV-YFP showed that FlgV forms a ring-like structure closely associated with the junction of two highly conserved flagellar components: the MS and C rings. The results of our studies suggest that the FlgV ring has adapted specifically in Campylobacterota to support the assembly and efficient function of the high-torque-generating motors.

The evaluation of tumorigenicity and characterization of colonies in a soft agar colony formation assay using polymerase chain reaction

In regenerative medicine, the tumorigenic potency of cells in cellular therapy products (CTPs) is a major concern for their application to patients. This study presents a method—the soft agar colony formation assay using polymerase chain reaction (PCR)—to evaluate tumorigenicity. MRC-5 cells, contaminated with HeLa cells, were cultured for up to 4 weeks in soft agar medium. Cell-proliferation-related mRNAs, Ki-67 and cyclin B, could be detected in 0.01% of HeLa cells after 5 days of culture, whereas cyclin-dependent kinase 1 (CDK1) could be detected after 2 weeks. On the other hand, CDK2, proliferating cell nuclear antigen (PCNA), and minichromosome maintenance protein 7 (MCM7) were not useful to detect HeLa cells even after 4 weeks of culture. The cancer stem cell (CSC) markers, aldehyde dehydrogenase 1 (ALDH1) and CD133 in 0.01% of HeLa cells, could be detected 2 and 4 weeks after culture, respectively. However, another CSC marker CD44 was not useful because its expression was also detected in MRC-5 cells alone. This study suggests that the application of the PCR method to the soft agar colony formation assay could evaluate not only the tumorigenic potency in the short-term but also characterize the colonies, eventually improving the safety of CTPs.

Anticancer effect of different rhizome extracts of the Lebanese Rheum ribes L. species on colorectal cancer cell lines

IntroductionColorectal cancer is the second leading cause of cancer-related mortality. Rheum ribes L. is one of the most important medicinal plants showing several biological activities. Few studies demonstrated anticancer potential of extracts of Turkish and Iranian Rheum ribes L. species rhizomes. We report for the first time the anticancer activity of different types of extracts of the rhizomes of the Lebanese Rheum ribes L. species against colorectal cancer cell lines. MethodsFive types of extracts were prepared using different solvents and cytotoxicity was assessed on colorectal cancer cell lines. Ethanolic and dichloromethane extracts were chosen for further studies and their effects on cell proliferation (MTT assay and trypan blue exclusion assay), colony forming ability (colony formation in soft agar), migration (scratch wound assay), and adhesion were assessed. ResultsOur results showed that ethanolic and dichloromethane extracts reduce HT-29 and HCT-116 cell viability in a dose and time dependent manner. They are also able to decrease colony-forming ability of these cells in soft agar medium. This anti-proliferative effect was accompanied by an increase in PARP cleavage suggesting a proapoptotic effect. Moreover, these extracts were also able to inhibit HT-29 and HCT-116 cell adhesion and migration suggesting their ability to reduce metastatic dissemination. ConclusionThese findings suggest a high therapeutic potential of the extracts of rhizomes of the Lebanese Rheum ribes L. species in the treatment of colorectal cancer.

Quorum Sensing and Cyclic di-GMP Exert Control Over Motility of Vibrio fischeri KB2B1.

Bacterial motility is critical for symbiotic colonization by Vibrio fischeri of its host, the squid Euprymna scolopes, facilitating movement from surface biofilms to spaces deep inside the symbiotic organ. While colonization has been studied traditionally using strain ES114, others, including KB2B1, can outcompete ES114 for colonization for a variety of reasons, including superior biofilm formation. We report here that KB2B1 also exhibits an unusual pattern of migration through a soft agar medium: whereas ES114 migrates rapidly and steadily, KB2B1 migrates slowly and then ceases migration. To better understand this phenomenon, we isolated and sequenced five motile KB2B1 suppressor mutants. One harbored a mutation in the gene for the cAMP receptor protein (crp); because this strain also exhibited a growth defect, it was not characterized further. Two other suppressors contained mutations in the quorum sensing pathway that controls bacterial bioluminescence in response to cell density, and two had mutations in the diguanylate cyclase (DGC) gene VF_1200. Subsequent analysis indicated that (1) the quorum sensing mutations shifted KB2B1 to a perceived low cell density state and (2) the high cell density state inhibited migration via the downstream regulator LitR. Similar to the initial point mutations, deletion of the VF_1200 DGC gene increased migration. Consistent with the possibility that production of the second messenger c-di-GMP inhibited the motility of KB2B1, reporter-based measurements of c-di-GMP revealed that KB2B1 produced higher levels of c-di-GMP than ES114, and overproduction of a c-di-GMP phosphodiesterase promoted migration of KB2B1. Finally, we assessed the role of viscosity in controlling the quorum sensing pathway using polyvinylpyrrolidone and found that viscosity increased light production of KB2B1 but not ES114. Together, our data indicate that while the two strains share regulators in common, they differ in the specifics of the regulatory control over downstream phenotypes such as motility.

EML4-ALK induces cellular senescence in mortal normal human cells and promotes anchorage-independent growth in hTERT-transduced normal human cells

BackgroundChromosomal inversions involving anaplastic lymphoma kinase (ALK) and echinoderm microtubule associated protein like 4 (EML4) generate a fusion protein EML4-ALK in non-small cell lung cancer (NSCLC). The understanding of EML4-ALK function can be improved by a functional study using normal human cells.MethodsHere we for the first time conduct such study to examine the effects of EML4-ALK on cell proliferation, cellular senescence, DNA damage, gene expression profiles and transformed phenotypes.ResultsThe lentiviral expression of EML4-ALK in mortal, normal human fibroblasts caused, through its constitutive ALK kinase activity, an early induction of cellular senescence with accumulated DNA damage, upregulation of p16INK4A and p21WAF1, and senescence-associated β-galactosidase (SA-β-gal) activity. In contrast, when EML4-ALK was expressed in normal human fibroblasts transduced with telomerase reverse transcriptase (hTERT), which is activated in the vast majority of NSCLC, the cells showed accelerated proliferation and acquired anchorage-independent growth ability in soft-agar medium, without accumulated DNA damage, chromosome aberration, nor p53 mutation. EML4-ALK induced the phosphorylation of STAT3 in both mortal and hTERT-transduced cells, but RNA sequencing analysis suggested that the different signaling pathways contributed to the different phenotypic outcomes in these cells. While EML4-ALK also induced anchorage-independent growth in hTERT-immortalized human bronchial epithelial cells in vitro, the expression of EML4-ALK alone did not cause detectable in vivo tumorigenicity in immunodeficient mice.ConclusionsOur data indicate that the expression of hTERT is critical for EML4-ALK to manifest its in vitro transforming activity in human cells. This study provides the isogenic pairs of human cells with and without EML4-ALK expression.

Quorum quenching as a strategy for treating Methicillin Resistant S. aureus (MRSA) - Effect of ε-Polylysine, ethanolic extracts of guava leaves and mango seed kernel

Staphylococcus aureus accessory gene regulatory Quorum Sensing (QS) system facilitates biofilm formation and biofilms are major contributors for antimicrobial resistance. Quorum quenchers could be used as an adjunct to antibiotics to reduce the development of drug resistance. The objective of this study was to evaluate the sub-inhibitory concentration of ethanolic extracts of Mango Seed Kernel Extract (MSKE), Guava Leaf Extract (GLE) and ε-Polylysine (ε-PL) against quorum sensing mediated virulence factors of S. aureus. We evaluated the antibacterial and Quorum Quenching (QQ) activity of these compounds on 10 MRSA and 10 MSSA isolates. The antibacterial activity was tested by disc diffusion assay. The Minimum Inhibitory Concentrations (MIC) for MRSA isolates were: 20 µg/mL for ε-Polylysine, 20 µg/mL for MSKE extract and GLE and for MSSA isolates were:12.5 µg/mL for ε-Polylysine, 20 µg/mL for MSKE extract and GLE. Quorum Sensing Inhibition (QSI) activity was determined at sub-MIC of 10 µg/mL of all the compounds by studying inhibition of the delta hemolysin on sheep blood agar plate and motility on soft agar media. All these compounds affected the motility and expression of δ-hemolysin activity which confirms that these compounds interfere with the QS activity. The QQ effect was confirmed by quantitation of hld (delta hemolysin) transcript and rnaIII transcript by qPCR. The results of this study will be presented as proof of QQ activity by ε-PL, MSKE, and GLE on S. aureus in general and MRSA in particular, as an attractive proposition for adjunct therapy and anti-virulence therapy of MRSA infections.

Involvement of Heme in Colony Spreading of Staphylococcus aureus.

Staphylococcus aureus spreads rapidly on the surface of soft agar medium. The spreading depends on the synthesis of biosurfactants, i.e., phenol soluble modulins (PSMs), which facilitate colony spreading of S. aureus. Our earlier study demonstrated that water accumulates in a colony is important to modulate colony spreading of S. aureus. The current study screened a transposon-based mutant library of S. aureus HG001 and obtained four non-spreading mutants with mutations in hemY and ctaA, which are involved in heme synthesis. The spreading ability of these mutants was restored when the mutants are transformed with a plasmid encoding hemY or ctaA, respectively. HemY mutants, which do not synthesize heme B, were able to spread on agar medium supplemented with hemin, a heme B derivative. By contrast, hemin supplementation did not rescue the spreading of the ctaA mutant, which lacks heme B and heme A, indicating that heme A is also critical for colony spreading. Moreover, mutations in hemY and ctaA had little effect on PSMs production but affect ATP production and water accumulation in the colony. In conclusion, this study sheds light on the role of heme synthesis and energy production in the regulation of S. aureus colony spreading, which is important for understanding the movement mechanisms of bacteria lacking a motor apparatus.

Uji pigmen dan deteksi kapsul polisakarida pada Staphylococcus aureus isolat asal broiler PIGMENT TEST AND DETECTION OF POLISAKARIDA CAPSULES ON Staphylococcus aureus ISOLAT BROILER

Staphylococcus aureus is a pathogenic bacterium causing disease in humans and animals. In broilers it cause septicemia, tendosinovitis, dermatitis, endocarditis, wound infections and arthritis and bumblefoot. The ability of Staphylococcus aureus to cause disease depends on the virulence factors they bear. The purpose of this research is to investigate the distribution of pigment production type and the existence of genes of polysaccharide capsule phenotype and genotype as determinant factor of virulence of bacteria on 15 isolates of Staphylococcus aureus from broiler. Pigment production test showed that 86.7% of isolates producing yellow pigment and 13.3% isolates produce orange pigment. The detection of polysaccharide capsules was phenotypically performed with hydrophobicity test with serum soft agar medium (SSA) showed 53.3% isolate grow compact and 46,7% isolate grown difuse and hydrophobicity test by salt aggregation test method (SAT) showed 66,7% hydrophil and 33.3% are hydrophobic. Genotype detection of polysaccharide capsule genes by polymerase chain reaction (PCR) showed 66.7% detected cap5 (amplicon 361bp) and 33.3% detected cap8 (173bp ampliole). The type of pigment production and the presence of polysaccharide capsules are some of the virulent factors in Staphylococcus aureus.

Flagellum-mediated motility in Pelotomaculum thermopropionicum SI.

The basic functions of a propionate-oxidizing bacterium Pelotomaculum thermopropionicum flagellum, such as motility and chemotaxis, have not been studied. To investigate its motility, we compared with that of Syntrophobacter fumaroxidans, an aflagellar propionate-oxidizing bacterium, in soft agar medium. P. thermopropionicum cells spread, while S. fumaroxidans cells moved downward slightly, indicating flagellum-dependent motility in P. thermopropionicum SI. The motility of P. thermopropionicum was inhibited by the addition of carbonyl cyanide m-chlorophenyl hydrazone, a proton uncoupler, which is consistent with the fact that stator protein, MotB of P. thermopropionicum, shared sequence homology with proton-type stators. In addition, 5-N-ethyl-N-isopropyl amiloride, an Na+ channel blocker, showed no inhibitory effect on the motility. Furthermore, motAB of P. thermopropionicum complemented the defective swimming ability of Escherichia coli ∆motAB. These results suggest that the motility of P. thermopropionicum SI depends on the proton-type flagellar motor.

DEAD box protein DDX1 promotes colorectal tumorigenesis through transcriptional activation of the LGR5 gene.

DDX1, a member of the DEAD box RNA helicase family, plays a critical role in testicular tumors. However, it remains to be clarified whether DDX1 is involved in other types of malignant tumors such as colorectal cancer. We disrupted the DDX1 gene in a human colorectal cancer cell line LoVo using the CRISPR/Cas9‐mediated gene‐targeting system. DDX1‐KO LoVo cells exhibited a much slower growth rate, produced fewer colonies in soft agar medium, and generated smaller solid tumors in nude mice than parental LoVo cells. Such phenotypes of the DDX1‐KO cells were mostly reversed by exogenous expression of DDX1. These results indicate that DDX1 is required for tumorigenicity of colorectal cancer cells. In the DDX1‐KO cells, the cancer stem cell marker genes LGR5, CD133, ALDH1 and SOX2 were markedly suppressed. Among them, expression of LGR5, which is essential for tumorigenicity of colorectal cancer cells, was restored in the DDX1‐transfected DDX1‐KO cells. Consistently, the DDX1‐KO cells lost sphere‐forming capacity in a DDX1‐dependent fashion. Reporter and chromatin immunoprecipitation assays revealed that DDX1 directly bound to the −1837 to −1662 region of the enhancer/promoter region of the human LGR5 gene and enhanced its transcription in LoVo cells. Repression of LGR5 by DDX1 knockdown was observed in 2 other human colorectal cancer cell lines, Colo320 and SW837. These results suggest that LGR5 is a critical effector of DDX1 in colorectal cancer cells. The DDX1‐LGR5 axis could be a new drug target for this type of malignant cancer.

Overexpression of PER3 Inhibits Self-Renewal Capability and Chemoresistance of Colorectal Cancer Stem-Like Cells via Inhibition of Notch and β-Catenin Signaling.

PER3, a circadian clock gene, plays an important role in colorectal cancer, but its action and underlying mechanism in colorectal cancer stem-like cells (CSCs) remain unclear. In this study, the colorectal CSCs were enriched in colorectal HCT-116 sphere-forming cells, expressing lower levels of stem cell markers CD133, CD44, LGR5, and SOX2 compared with HCT-116 cells. A drug-resistant strain from HCT-116 was established. Western blot and qRT-PCR analysis showed that PER3 was downregulated in colorectal CSCs and drug-resistant HCT-116. Overexpression of PER3 could strengthen 5-FU-induced inhibitory effects on colorectal CSCs, but knockdown of PER3 decreased its inhibition of colorectal CSCs. In addition, overexpression of PER3 in colorectal CSCs resulted in reduced colony formation efficiency in a soft agar medium and self-renewal efficiency. Inversely, knockdown of PER3 enhanced self-renewal of colorectal CSCs. Overexpression of PER3 decreased stemness markers and Notch1, Jagged1, β-catenin, c-Myc, and LGR5 in colorectal CSCs. When Notch or β-catenin signaling was inhibited, the chemoresistance and self-renewal capability of colorectal CSCs were decreased. It was confirmed that PER3 can reduce chemoresistance and self-renewal capability of colorectal CSCs via inhibition of Notch and β-catenin signaling. Our results reveal that PER3 plays a critical role in maintaining the stemness of colorectal CSCs and may be a promising target for elimination of CSCs.

The new flagella-associated collagen-like proteins ClpB and ClpC of Bacillus amyloliquefaciens FZB42 are involved in bacterial motility

Collagen-like proteins (CLPs) share the distinctive Gly-X-Thr repeating amino acid sequence of animal collagens, and contain N- and C-terminal domain making a collagen-like structure in Bacillus amyloliquefaciens FZB42, a plant growth-promoting rhizobacterium. Our previous study demonstrated that CLPs play important roles in biofilm construction and adherence to the surfaces on plant roots. However, bacterial localization of the CLPs remains unclear. Here, disrupted strains on all four clp genes (clpA, clpB, clpC and clpD) shown fewer filament than wild-type bacteria in extracellular matrix under scanning electron microscope (SEM). Transmission electron microscopy (TEM) was used to observe the differences on filament which associated on the cell surface, then the CLPs mutation strains showed less flagella than the wild type. Immunogold labeling determined the location that ClpB and ClpC localized on the flagella surface. In addition, western blotting analysis of crude flagella extracts suggested that the ClpB and ClpC are associated to flagella as well. The mutation strains also reduced motility of swimming on the surface of soft agar medium and changed the architectural of microcolony biofilm edge. The study suggests that collagen-like protein ClpB and ClpC, as novel proteins, associated with flagella in B. amyloliquefaciens.

CBIO-40THREE-DIMENSIONAL ASSESSMENT OF BYSTANDER EFFECTS OF MESENCHYMAL STEM CELLS CARRYING A CYTOSINE DEAMINASE GENE ON GLIOMA CELLS

Stem cells carrying a suicide gene have emerged as therapeutic candidates for their cytotoxic bystander effects on neighboring cancers, while being non-toxic to other parts of the body. However, traditional cytotoxicity assays are unable to adequately assess the therapeutic effects of bystander cells. Here, we report a method to assess bystander effects of therapeutic stem cells against 3-dimensionally grown glioma cells in real time. U87 glioma cells were stably transduced to express a green fluorescence protein and co-cultivated with mesenchymal stem cells engineered to carry a bacterial cytosine deaminase gene (MSC/CD). Following addition of a 5-fluorocytine (5-FC) prodrug to the co-culture, fluorescence from U87 cells was obtained and analyzed in real time. Notably, the IC50 of 5-FC was higher when U87 cells were grown 3-dimensionally in soft agar medium for 3 weeks, as compared to those grown for one week in two-dimensional monolayer cultures. Additionally, more MSC/CD cells were required to maintain a similar level of efficacy. Since three-dimensional growth of glioma cells under our co-culture condition mimics the long-term expansion of cancer cells in vivo, our method can extend to an in vitro assay system to assess stem cell-mediated anti-cancer effects before advancing into preclinical animal studies.

Identification of Staphylococcus aureus colony-spreading stimulatory factors from mammalian serum.

Staphylococcus aureus forms giant colonies on soft-agar surfaces, which is called colony-spreading. In the present study, we searched for host factors that influence S. aureus colony-spreading activity. The addition of calf serum, porcine serum, or silkworm hemolymph to soft-agar medium stimulated S. aureus colony-spreading activity. Gel filtration column chromatography of calf serum produced a high molecular weight fraction and a low molecular weight fraction, both of which exhibited colony-spreading stimulatory activity. In the low molecular weight fraction, we identified the stimulatory factor as bovine serum albumin. The stimulatory fraction in the high molecular weight fraction was identified as high-density lipoprotein (HDL) particles. Delipidation of HDL abolished the stimulatory activity of HDL. Phosphatidylcholine, which is the major lipid component in HDL particles, stimulated the colony-spreading activity. Other phosphatidylcholine-containing lipoprotein particles, low-density lipoprotein and very low-density lipoprotein, also showed colony-spreading stimulatory activity. These findings suggest that S. aureus colony-spreading activity is stimulated by albumin and lipoprotein particles in mammalian serum.

Gamma-Fe2O3 nanoparticles increase therapeutic efficacy of combination with paclitaxel and anti-ABCG2 monoclonal antibody on multiple myeloma cancer stem cells in mouse model.

Cancer stem cells (CSCs) are thought to be responsible for the relapse of multiple myeloma (MM). The objective of this study was to target therapy of MM cancer stem cells using gamma-Fe2O3@DMSA magnetic nanoparticle combination with paclitaxel and anti-ABCG2 monoclonal antibody, and to evaluate the combined therapeutic efficacy. CSCs were isolated from human MM cell line RPMI 8226 based on negative expression of CD138 and CD34. In vivo and in vitro studies demonstrated that the isolated CD138-CD34- cells displayed certain stem cell characteristics, including significant increase in expression of ABCG2 transporter, proliferation, mobility, drug resistance, clonogenic potential in soft agar media and tumorigenecity in mice. Treatment with nanoparticles, paclitaxel and anti-ABCG2 antibody remarkably inhibited the growth of CD138-CD34- cells in vitro and their derived tumors in xenografts. The inhibition was also correlated with elevated expression of caspase-9, caspase-8 and caspase-3, and down-regulation of NF-KB. Our data indicate that the nanoparticle combination with paclitaxel and anti-ABCG2 monoclonal antibody offers an effective approach to treatment of MM CSCs through an apoptotic pathway.

MiR-375 targets the p53 gene to regulate cellular response to ionizing radiation and etoposide in gastric cancer cells

MicroRNAs (miRNAs) offer a new approach for molecular classification and individual therapy of human cancer due to their regulation of oncogenic pathways. In a previous report, elevated miR-375 was found in recurring gastric cancer, and it was predicted that miR-375 may be a regulator of p53 gene. However, its biological role and mechanism of actions remain unknown. In this study, we characterized the expression level of miR-375 in gastric cancer cell lines – BGC823, MGC803, SGC7901, AGS, N87, MKN45 – using RT-PCR. We found that exogenous expression of miR-375 promoted the growth of AGS cells in both liquid and soft agar media. In agreement with the previous report, overexpression of miR-375 in AGS cells reduced the p53 protein expression level. A luciferase assay demonstrated that miR-375 down-regulated p53 expression through an interaction with the 3′ UTR region of p53. In addition, the expression of miR-375 desensitizes cells to ionizing radiation and etoposide. Flow cytometry analyses showed that miR-375 abrogated the cell cycle arrest and apoptosis after DNA damage. These results demonstrate that miR-375 targets p53 to regulate the response to ionizing radiation and etoposide treatment.

Transient high level mammalian reovirus replication in a bat epithelial cell line occurs without cytopathic effect

Mammalian reoviruses exhibit a large host range and infected cells are generally killed; however, most studies examined only a few cell types and host species, and are probably not representative of all possible interactions between virus and host cell. Many questions thus remain concerning the nature of cellular factors that affect viral replication and cell death. In the present work, it was observed that replication of the classical mammalian reovirus serotype 3 Dearing in a bat epithelial cell line, Tb1.Lu, does not result in cell lysis and is rapidly reduced to very low levels. Prior uncoating of virions by chymotrypsin treatment, to generate infectious subviral particles, increased the initial level of infection but without any significant effect on further viral replication or cell survival. Infected cells remain resistant to virus reinfection and secrete an antiviral factor, most likely interferon, that is protective against the unrelated encephalomyocarditis virus. Although, the transformed status of a cell is believed to promote reovirus replication and viral “oncolysis”, resistant Tb1.Lu cells exhibit a classical phenotype of transformed cells by forming colonies in semisolid soft agar medium. Further transduction of Tb.Lu cells with a constitutively active Ras oncogene does not seem to affect cell growth or reovirus effect on these cells. Infected Tb1.Lu cells can produce low-level of infectious virus for a long time without any apparent effect, although these cells are resistant to reinfection. The results suggest that Tb1.Lu cells can mount an unusual antiviral response. Specific properties of bat cells may thus be in part responsible for the ability of the animals to act as reservoirs for viruses in general and for novel reoviruses in particular. Their peculiar resistance to cell lysis also makes Tb1.Lu cells an attractive model to study the cellular and viral factors that determine the ability of reovirus to replicate and destroy infected cells.

A supplemented soft agar chemotaxis assay demonstrates the Helicobacter pylori chemotactic response to zinc and nickel

Directed motility, or chemotaxis, is required for Helicobacter pylori to establish infection in the stomach, although the full repertoire of this bacterium's chemotactic responses is not yet known. Here we report that H. pylori responds to zinc as an attractant and nickel as a repellent. To reach this conclusion, we employed both a temporal chemotaxis assay based on bacterial reversals and a supplemented soft agar spatial assay. We refined the temporal assay using a previously described chemorepellent, acid, and found that H. pylori requires rich media with serum to maintain optimal swimming motility. Surprisingly, we found that some strains respond to acid as an attractant, and that the TlpC chemoreceptor correlated with whether acid was sensed as an attractant or repellent. Using this same assay, we detected weak repellent responses to nickel and copper, and a varied response to zinc. We thus developed an alternative spatial chemotactic assay called the supplemented soft agar assay, which utilizes soft agar medium supplemented with the test compound. With Escherichia coli, the attractant serine slowed overall bacterial migration, while the repellent nickel increased the speed of overall migration. In H. pylori we detected slowed migration with doubled tryptone media, as well as zinc, consistent with an attractant response. In contrast, nickel increased migration, consistent with repulsion.

Characterization of cancer stem-like cells in chordoma

Chordomas are locally aggressive bone tumors known to arise from the remnants of the notochord. Because chordomas are rare, molecular studies aimed at developing new therapies are scarce and new approaches are needed. Chordoma cells and cancer stem-like cells share similar characteristics, including self-renewal, differentiation, and resistance to chemotherapy. Therefore, it seems possible that chordomas might contain a subpopulation of cancer stem-like cells. The aim of this study is to determine whether cancer stem-like cells might be present in chordomas. In this study, the authors used gene expression analysis for common cancer stem-like cellmarkers, including c-myc, SSEA-1, oct4, klf4, sox2, nanog, and brachyury, and compared chordoma cells and tissues with nucleus pulposus tissues (disc degenerated nontumorigenic tissues). Differentiation through agents such as all-trans retinoic acid and osteogenic differentiation medium was induced to the chordoma cells. Additionally, U-CH1 cells were sorted via magnetic cell sorting for stem cell markers CD133 and CD15. After separation, positive and negative cells for these markers were grown in a nonadherent environment, soft agar, to determine whether the presence of these cancer stem-like cells might be responsible for initiating chordoma. The results were compared with those of untreated cells in terms of migration, proliferation, and gene expression by using reverse transcriptase polymerase chain reaction. The results indicate that chordoma cells might be differentiating and committing into an osteogenic lineage when induced with the osteogenic differentiation agent. Chordoma cells that are induced with retinoic acid showed slower migration and proliferation rates when compared with the untreated cells. Chordoma cells that were found to be enriched by cancer stem-like cell markers, namely CD133 and CD15, were able to live in a nonadherent soft agar medium, demonstrating a self-renewal capability. To the authors' knowledge, this is the first time that cancer stem-like cell markers were also found to be expressed in chordoma cells and tissues. Cancer stem-like cell detection might be an important step in determining the recurrent and metastatic characteristics of chordoma. This finding may lead to the development of new approaches toward treatments of chordomas.

Using ABCG2-molecule-expressing side population cells to identify cancer stem-like cells in a human ovarian cell line

CSCs (cancer stem cells) are a small subset of cells within a tumour that possesses the characteristics of stem cells and are considered to be responsible for resistance to chemoradiation. Identification of CSCs through stem cell characteristics might have relevant clinical implications. In this study, SP (side population ) cells were sorted from a human ovarian cancer cell line by FACS to determine whether cancer stem cell-like SP cells were present. A very small fraction of SP cells (2.6%) was detected in A2780 cells. SP cells possessed the following characteristics: highly proliferative activity, marked ability for self-renewal in soft agar and culture medium, high expression of ABCG2, drug resistance to vinblastine in vitro, and strong tumourigenic potential in Balb/c nude mice. It is concluded that there exists in the A2780 cell line a small number of SP cells with high expression of ABCG2. The cells have the characteristics of cancer stem-like cells, and identification and cloning of such human SP cells can help in improving therapeutic approaches to ovarian cancer in patients.