Roudabeh J. Jamasbi

Growth inhibition and DNA damage induced by benzo[a]pyrene and formaldehyde in primary cultures of rat tracheal epithelial cells

The effects of benzo[a]pyrene (BAP) and formaldehyde (HCHO), alone and combined, on cell growth and DNA damage were determined in primary cultures of rat tracheal epithelial cells dissociated from rat tracheas. Cell cultures treated with 25 microM BAP for 24 h or 200 microM HCHO for 90 min did not have a marked reduction in cell growth. However, their combined treatment reduced cell growth by 60% of control when cultures were exposed to BAP followed by HCHO as well as the reverse order. None of these treatments significantly decreased cell viability as judged by dye exclusion, nor did they enhance cell terminal differentiation as measured by cornified envelope formation. Alkaline elution analysis of DNA damage detected both DNA-protein crosslinks (DPC) and DNA single-strand breaks (SSB) as a result of HCHO treatment, whereas BAP treatment caused only SSB. While HCHO-induced SSB were repaired within 2 h, BAP-induced SSB were detected 3 days after treatment. Combined treatment of cell cultures with BAP followed by HCHO resulted in more SSB than was obtained from either agent alone, but less DPC than was detected from HCHO alone. The increased number of SSB obtained from this combined treatment may be related to the marked enhancement of carcinogenesis observed in earlier in vivo-in vitro studies.

Effects of curcumin on stem-like cells in human esophageal squamous carcinoma cell lines

BackgroundMany cancers contain cell subpopulations that display characteristics of stem cells. Because these cancer stem cells (CSCs) appear to provide resistance to chemo-radiation therapy, development of therapeutic agents that target CSCs is essential. Curcumin is a phytochemical agent that is currently used in clinical trials to test its effectiveness against cancer. However, the effect of curcumin on CSCs is not well established. The current study evaluated curcumin-induced cell death in six cancer cell lines derived from human esophageal squamous cell carcinomas. Moreover, these cell lines and the ones established from cells that survived curcumin treatments were characterized.MethodsCell loss was assayed after TE-1, TE-8, KY-5, KY-10, YES-1, and YES-2 cells were exposed to 20–80 μM curcumin for 30 hrs. Cell lines surviving 40 or 60 μM curcumin were established from these six original lines. The stem cell markers aldehyde dehydrogenase-1A1 (ALDH1A1) and CD44 as well as NF-κB were used to compare CSC-like subpopulations within and among the original lines as well as the curcumin-surviving lines. YES-2 was tested for tumorsphere-forming capabilities. Finally, the surviving lines were treated with 40 and 60 μM curcumin to determine whether their sensitivity was different from the original lines.ResultsThe cell loss after curcumin treatment increased in a dose-dependent manner in all cell lines. The percentage of cells remaining after 60 μM curcumin treatment varied from 10.9% to 36.3% across the six lines. The cell lines were heterogeneous with respect to ALDH1A1, NF-κB and CD44 expression. KY-5 and YES-1 were the least sensitive and had the highest number of stem-like cells whereas TE-1 had the lowest. The curcumin-surviving lines showed a significant loss in the high staining ALDH1A1 and CD44 cell populations. Tumorspheres formed from YES-2 but were small and rare in the YES-2 surviving line. The curcumin-surviving lines showed a small but significant decrease in sensitivity to curcumin when compared with the original lines.ConclusionOur results suggest that curcumin not only eliminates cancer cells but also targets CSCs. Therefore, curcumin may be an effective compound for treating esophageal and possibly other cancers in which CSCs can cause tumor recurrence.

A New Method for Identifying Stem-Like Cells in Esophageal Cancer Cell Lines

Cancer stem cells (CSCs) appear to resist chemo-radiotherapy and initiate tumor recurrence in patients. Isolation and further characterization of this subpopulation is important for targeting CSCs. Flow cytometry using Aldefluor, a fluorescent substrate of aldehyde dehydrogenase, has been used to isolate CSCs from various cancer cell lines. However, new techniques are needed to locate and identify CSCs in culture for live-cell analyses such as fluorescence microscopy without introducing artifacts during cell sorting and to observe CSC and non-CSC interactions. Previously, we characterized a distinct CSC subpopulation within human esophageal cancer cell lines (ESCC). In this study we introduce the attached-cell Aldefluor method (ACAM) to detect CSCs in ESCC cell lines (KY-5, KY-10, TE-1, TE-8, YES-1, YES-2). To validate this technique, we isolated CSCs from the YES-2 parental line using standard Aldefluor flow cytometry to create a cell line enriched in CSCs (YES-2CSC). This line showed significantly greater ACAM staining and higher CD44 levels than YES-2. ACAM also showed significantly higher ALDH activity in YES-2CSC than in YES-2S, a cell line that has a diminished CSC subpopulation after having survived treatment with curcumin. ACAM stained cells within tumorspheres made from the CSC-enriched line but not differentiating cells from the tumorspheres. This study also demonstrates a new method for generating and growing tumorspheres without the growth factor supplements normally used in medium to form tumorspheres. ACAM should be evaluated using other cancer cell lines to further substantiate its effectiveness and to characterize CSCs in culture through various imaging techniques.

Elevated mPer1 gene expression in tumor stroma imaged through bioluminescence

The tumor stroma has significant effects on cancer cell growth and metastasis. Interactions between cancer and stromal cells shape tumor progression through poorly understood mechanisms. One factor regulating tumor growth is the circadian timing system that generates daily physiological rhythms throughout the body. Clock genes such as mPer1 serve in molecular timing events of circadian oscillators and when mutated can disrupt circadian rhythms and accelerate tumor growth. Stimulation of mPer1 by cytokines suggests that the timing of circadian oscillators may be altered by these tumor‐derived signals. To explore tumor and stromal interactions, the pattern of mPer1 expression was imaged in tumors generated through subcutaneous injection of Lewis lung carcinoma (LLC) cells. Several imaging studies have used bioluminescent cancer cell lines expressing firefly luciferase to image tumor growth in live mice. In contrast, this study used non‐bioluminescent cancer cells to produce tumors within transgenic mice expressing luciferase controlled by the mPer1 gene promoter. Bioluminescence originated only in host cells and was significantly elevated throughout the tumor stroma. It was detected through the skin of live mice or by imaging the tumor directly. No effects on the circadian timing system were detected during three weeks of tumor growth according to wheel‐running rhythms. Similarly, no effects on mPer1 expression outside the tumor were found. These results suggest that mPer1 activity may play a localized role in the interactions between cancer and stromal cells. The effects might be exploited clinically by targeting the circadian clock genes of stromal cells.

Circadian Clock Genes Are Essential for Normal Adult Neurogenesis, Differentiation, and Fate Determination.

Adult neurogenesis creates new neurons and glia from stem cells in the human brain throughout life. It is best understood in the dentate gyrus (DG) of the hippocampus and the subventricular zone (SVZ). Circadian rhythms have been identified in the hippocampus, but the role of any endogenous circadian oscillator cells in hippocampal neurogenesis and their importance in learning or memory remains unclear. Any study of stem cell regulation by intrinsic circadian timing within the DG is complicated by modulation from circadian clocks elsewhere in the brain. To examine circadian oscillators in greater isolation, neurosphere cultures were prepared from the DG of two knockout mouse lines that lack a functional circadian clock and from mPer1::luc mice to identify circadian oscillations in gene expression. Circadian mPer1 gene activity rhythms were recorded in neurospheres maintained in a culture medium that induces neurogenesis but not in one that maintains the stem cell state. Although the differentiating neural stem progenitor cells of spheres were rhythmic, evidence of any mature neurons was extremely sparse. The circadian timing signal originated in undifferentiated cells within the neurosphere. This conclusion was supported by immunocytochemistry for mPER1 protein that was localized to the inner, more stem cell-like neurosphere core. To test for effects of the circadian clock on neurogenesis, media conditions were altered to induce neurospheres from BMAL1 knockout mice to differentiate. These cultures displayed unusually high differentiation into glia rather than neurons according to GFAP and NeuN expression, respectively, and very few BetaIII tubulin-positive, immature neurons were observed. The knockout neurospheres also displayed areas visibly devoid of cells and had overall higher cell death. Neurospheres from arrhythmic mice lacking two other core clock genes, Cry1 and Cry2, showed significantly reduced growth and increased astrocyte proliferation during differentiation, but they generated normal percentages of neuronal cells. Neuronal fate commitment therefore appears to be controlled through a non-clock function of BMAL1. This study provides insight into how cell autonomous circadian clocks and clock genes regulate adult neural stem cells with implications for treating neurodegenerative disorders and impaired brain functions by manipulating neurogenesis.

Development of Circadian Oscillators in Neurosphere Cultures during Adult Neurogenesis

Circadian rhythms are common in many cell types but are reported to be lacking in embryonic stem cells. Recent studies have described possible interactions between the molecular mechanism of circadian clocks and the signaling pathways that regulate stem cell differentiation. Circadian rhythms have not been examined well in neural stem cells and progenitor cells that produce new neurons and glial cells during adult neurogenesis. To evaluate circadian timing abilities of cells undergoing neural differentiation, neurospheres were prepared from the mouse subventricular zone (SVZ), a rich source of adult neural stem cells. Circadian rhythms in mPer1 gene expression were recorded in individual spheres, and cell types were characterized by confocal immunofluorescence microscopy at early and late developmental stages in vitro. Circadian rhythms were observed in neurospheres induced to differentiate into neurons or glia, and rhythms emerged within 3–4 days as differentiation proceeded, suggesting that the neural stem cell state suppresses the functioning of the circadian clock. Evidence was also provided that neural stem progenitor cells derived from the SVZ of adult mice are self-sufficient clock cells capable of producing a circadian rhythm without input from known circadian pacemakers of the organism. Expression of mPer1 occurred in high frequency oscillations before circadian rhythms were detected, which may represent a role for this circadian clock gene in the fast cycling of gene expression responsible for early cell differentiation.

Biological heterogeneity and radiation sensitivity of in vitro propagated lung metastatic lines originated from a transplantable squamous cell carcinoma of BALB/c mouse.

SummarySeven cell lines established from a diethylnitrosamine (DEN)-induced forestomach carcinoma (DEN3) of a BALB/c mouse and its six pulmonary metastatic foci were used to study the biological and functional diversity of tumor cells. DEN3 is a highly tumorigenic line capable of forming lung metastases readily. Six metastatic nodules were isolated from the lungs of syngeneic mice and six cell lines were established. The cell lines differed in characteristics such as tumorigenicity, metastatic capability, and in vivo and in vitro growth properties. Radiation sensitivity of these cell lines was examined by exposure, at ner confluency stage of in vitro growth, to doses of 2.5 to 50 Gray (Gy) X-rays (1 Gy=100 rads). Shortly after exposure (approximately 5 min), the cells were harvested and 105 cells were cultured or inoculated into syngeneic mice, or both. Growth of three of the six cell lines tested was prohibited by 5 Gy. However, some populations from the other cell lines were able to survive 5 or 10 Gy. Progenies of the cells that survived primary radiation exposure after several in vitro passages were able to withstand another exposure of the same magnitude but not a higher dose. The X-rayed survivor cells also maintained their tumorigenic potential.

Phenotypic and Genotypic Characteristics of Clinical Isolates of Pseudomonas aeruginosa: Rate of Occurrence and Distribution of Different Serotypes, Antimicrobial Susceptibility Profiles, and Molecular Typing

Background: In the current investigation, 167 clinical isolates of Pseudomonas aeruginosa obtained from a Northwest Ohio hospital were tested for phenotypic diversity using serotyping and antibiotic susceptibility testing. The genetic diversity of the selected strains was determined by DNA fingerprinting. Methods: The isolates were serotyped by slide agglutination. The susceptibility was measured by disk diffusion. To analyze genetic variability, 96 strains (serotypes O:1, O:2, O:6, and O:11) were studied by polymerase chain reaction (PCR)-based single primer DNA fingerprinting.

Genetic analysis of Pseudomonas aeruginosa by enterobacterial repetitive intergenic consensus polymerase chain reaction (PCR) and arbitrarily primed PCR: gel analysis compared with microchip gel electrophoresis.

OBJECTIVES To assess the applicability of a newly emerging microchip gel electrophoresis for rapid strain differentiation among clinical isolates of Pseudomonas aeruginosa, and to compare this technique with the traditional gel method for DNA separation. METHODS One hundred clinical strains of P. aeruginosa obtained from a hospital in northwestern Ohio were tested for reactivity to 3 serotype-specific monoclonal antibodies by enzyme-linked immunosorbent assay. Twelve strains (4 from each serogroup) were selected for DNA analysis by polymerase chain reaction (PCR)-based, single primer DNA fingerprinting methods with 3 different primers: 1 enterobacterial repetitive intergenic consensus PCR and 2 arbitrarily primed PCRs. The PCR products were analyzed by agarose slab gel and microchip gel electrophoresis. RESULTS Of the 100 clinical isolates tested, 39% (4%, 14%, and 21%) were found to be serotypes 0:3, 0:6, and 0:11, respectively. Twelve strains were chosen for DNA analysis by PCR. The PCR products were analyzed by agarose slab gel electrophoresis and on microchips to determine interspecies diversity. Both methods demonstrated that different serotypes exhibited different electrophoretic patterns. Two strains (clinical strains 6 and 7, serotype 0:6) showed identical patterns, indicating a high degree of relatedness. CONCLUSION In all cases, there was concordance between the electrophoretic patterns detected by the two methods. The capability of conducting both PCR and microchip gel electrophoresis offers an opportunity for an automated and rapid method for genetic analysis and differentiation among strains of P. aeruginosa and other microorganisms.

Properties of Lewis Lung Carcinoma Cells Surviving Curcumin Toxicity

The anti-inflammatory agent curcumin can selectively eliminate malignant rather than normal cells. The present study examined the effects of curcumin on the Lewis lung carcinoma (LLC) cell line and characterized a subpopulation surviving curcumin treatments. Cell density was measured after curcumin was applied at concentrations between 10 and 60 μM for 30 hours. Because of the high cell loss at 60 μM, this dose was chosen to select for surviving cells that were then used to establish a new cell line. The resulting line had approximately 20% slower growth than the original LLC cell line and based on ELISA contained less of two markers, NF-κB and ALDH1A, used to identify more aggressive cancer cells. We also injected cells from the original and surviving lines subcutaneously into syngeneic C57BL/6 mice and monitored tumor development over three weeks and found that the curcumin surviving-line remained tumorigenic. Because curcumin has been reported to kill cancer cells more effectively when administered with light, we examined this as a possible way of enhancing the efficacy of curcumin against LLC cells. When LLC cells were exposed to curcumin and light from a fluorescent lamp source, cell loss caused by 20 μM curcumin was enhanced by about 50%, supporting a therapeutic use of curcumin in combination with white light. This study is the first to characterize a curcumin-surviving subpopulation among lung cancer cells. It shows that curcumin at a high concentration either selects for an intrinsically less aggressive cell subpopulation or generates these cells. The findings further support a role for curcumin as an adjunct to traditional chemical or radiation therapy of lung and other cancers.