Fibroblasts-dependent invasion of podoplanin-positive cancer stem cells in squamous cell carcinoma

To clear whether podoplanin-positive cancer stem cells in squamous cell carcinoma have higher invasion activity during a fibroblasts-dependent invasion. A collagen gel invasion assay was performed using fluorescent ubiquitination-based cell cycle indicator-labeled A431 cells. The total number and number of invading cells in S/G2/M phase were counted using time-lapse imaging cocultured with fibroblasts. There was no significant difference between the number of invading podoplanin-positive and negative A431 cells when fibroblasts did not exist. On the contrary, the number of invading podoplanin-positive cells was significantly higher when fibroblasts existed. The frequency of cells in S/G2/M phase among invasion was no difference. Knockdown of podoplanin decreased the number of invaded A431 cells significantly when fibroblasts existed. Podoplanin-positive A431 cells display higher invasion activity when fibroblasts exist, suggesting that some biological functions of cancer stem cells might become evident only within the fibrous tumor microenvironment.     

MREdictor: a two-step dynamic interaction model that accounts for mRNA accessibility and Pumilio binding accurately predicts microRNA targets

The prediction of pairing between microRNAs (miRNAs) and the miRNA recognition elements (MREs) on mRNAs is expected to be an important tool for understanding gene regulation. Here, we show that mRNAs that contain Pumilio recognition elements (PRE) in the proximity of predicted miRNA-binding sites are more likely to form stable secondary structures within their 3′-UTR, and we demonstrated using a PUM1 and PUM2 double knockdown that Pumilio proteins are general regulators of miRNA accessibility. On the basis of these findings, we developed a computational method for predicting miRNA targets that accounts for the presence of PRE in the proximity of seed-match sequences within poorly accessible structures. Moreover, we implement the miRNA-MRE duplex pairing as a two-step model, which better fits the available structural data. This algorithm, called MREdictor, allows for the identification of miRNA targets in poorly accessible regions and is not restricted to a perfect seed-match; these features are not present in other computational prediction methods.     

EGFR through STAT3 modulates ΔN63α expression to sustain tumor‐initiating cell proliferation in squamous cell carcinomas

Many squamous cell carcinomas (SCCs) are characterized by high levels of EGFR and by overexpression of the ΔNp63α isoform. Here, we investigated the regulation of ΔNp63α expression upon EGFR activation and the role of the EGFR–ΔNp63α axis in proliferation of SCC tumor‐initiating cells (TICs). SCC cell lines A‐431, Cal‐27, and SCC‐25 treated with EGF showed a time‐dependent increase in ΔNp63α expression at the protein and mRNA levels, which was blocked by the tyrosine kinase inhibitor (TKI) Lapatinib. RNA interference experiments suggested the role of STAT3 in regulating ΔNp63α expression downstream of EGFR. Inactivation of EGFR by the monoclonal antibody Cetuximab and RNA interference against STAT3 or ΔNp63α impaired the TICs ability to grow under non‐differentiating conditions. Radiation treatment, which triggers EGFR activation, induced ΔNp63α accumulation without affecting TICs proliferation, whereas the combination Cetuximab plus radiation significantly reduced TICs growth under non‐differentiating conditions. Together, our findings provide evidence that ΔNp63α expression is regulated by EGFR activation through STAT3 and that the EGFR–ΔNp63α axis is crucial for proliferation of TICs present in SCCs. J. Cell. Physiol. 228: 871–878, 2013. © 2012 Wiley Periodicals, Inc.     

Cell-Type-Specific Gene Expression Profiling in Adult Mouse Brain Reveals Normal and Disease-State Signatures

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A methylcellulose microculture assay for the in vitro assessment of drug toxicity on granulocyte/macrophage progenitors (CFU-GM)

In a recent prevalidation study, the use of a methylcellulose colony-forming unit-granulocyte/macrophage (CFU-GM) macroassay for two independent in vitro tests (human and murine cell based) was suggested for quantifying the potential haematotoxicity of xenobiotics. In this paper, we describe the transfer of the macroassay to a 96-well plate microassay, in which the linearity of the response was studied (both in terms of CFU-GM and optical density [OD] versus the number of cells cultured), and the inhibitory concentration (IC) values for doxorubicin, 5-fluorouracil and taxol were determined and compared with those obtained by using the original macroassay. Fresh murine bone marrow and human umbilical cord blood mononuclear cells were used as a source of myeloid progenitors. The cells were cultured in methylcellulose containing granulocyte/macrophage-colony-stimulating factor, and in the presence of increasing drug concentrations. The cloning capacity of the progenitors was measured both as the number of colonies counted manually (CFU-GM), and as OD evaluated with an automated plate reader in an MTT test. Our results show that, in the microassay, up to 20 colonies/well could be easily counted, and that this range (20 to zero) gave a regression line from which IC values were calculated, which were very close to those obtained by using the macroassay (where the range of colony numbers was from 100 to zero). The test did not give good results when the OD (instead of the colony count) was used as the endpoint, because, although a high coefficient of determination was obtained, the OD values ranged from 0.6 to zero and the IC values determined were not comparable to those obtained by manual counts. The use of the microassay dramatically reduces the quantity of methylcellulose needed, and permits hundreds of cultures to be processed in the same experiment, contributing to significant reductions in both the work involved and the cost. A further important benefit is a reduction of the amount of drug needed for testing, which is crucial for screening new molecules, when many different toxicological tests have to be carried out. The microassay is therefore a useful and reproducible tool for screening compounds (chemicals, drugs and xenobiotics) for potential haematotoxicity directly on human myeloid progenitors, and could contribute significantly to reducing the use of animals in toxicity testing.     

Implementation of a molecular epidemiology approach to human pleural malignant mesothelioma

The carcinogenic effect of asbestos has been reported in the literature since 40 years, and early studies describing the epidemic occurrence of malignant mesothelioma (MM) in asbestos workers, have become a paradigm of occupational cancer research. Research on MM was abandoned for many years since MM was considered as an asbestos-related disease, interesting only from a perspective of disease control and preventive policies. The introduction of new biological endpoints in the epidemiological studies has boosted research in the field, providing new tools for the study of emerging priority in cancer research and in public health. This approach, known as molecular epidemiology has a great potential in the study of MM, contributing to the understanding of susceptibility factors, to the evaluation of cancer risk in people occupationally or environmentally exposed to carcinogens, and to the enhancement of diagnosis and therapy. A comprehensive approach based on the use of banks of biological samples is presented and its advantages discussed here. The application of innovative endpoints, such as oncoproteins in biologic fluids, genetic polimorphisms, or gene function is discussed, and relevant literature reviewed.     

Micronuclei frequency in children exposed to environmental mutagens: a review

Cytogenetic monitoring has been traditionally used for the surveillance of populations exposed to genotoxic agents. In recent years sensitivity problems emerged in surveys of populations exposed to low levels of mutagens, and therefore alternative approaches have been explored. Biomonitoring studies in children are a promising field, since because of evident differences in the uptake, metabolism, distribution and excretion of mutagens this population seems to be more susceptible than adults. Further, the effect of major confounders such as cigarettes smoking, occupation, life-style, and dietary factors plays a minor role. Among cytogenetic assays, the micronucleus assay (MN) has several advantages and is increasingly used. A review was then carried out to synthesize the published data on the occurrence of MN in children and adolescents (age range 0-18 years), and to assess the impact of genotoxic exposure on MN frequency. Overall, 20 papers from international literature and 8 Russian papers were included. An effect of age was found within this age range, while the influence of gender on MN frequency was irrelevant. These results were confirmed by the re-analysis of data for 448 children selected from the HUMN database. An effect of chronic and infectious diseases on MN levels has been reported by various authors. Most studies describing the effect of exposure to genotoxic agents (ionizing radiation, chemicals, drugs, environmental tobacco smoke) found an increase of MN in exposed children. The limited number of published papers indicates that the conduct of properly designed studies on the effect of environmental pollutants in children may be difficult. This review confirmed the usefulness of MN assay in biomonitoring studies conducted in children, revealing that in many circumstances investigating children increases the sensitivity of the study, even with low dose exposures.