Practicalities of Cell Sorting.

Cell sorting is a technique commonly used in academic and biotechnology laboratories in order to separate out cells or particles of interest from heterogeneous populations. Cell sorters use the same principles as flow cytometry analyzers, but instead of cell populations passing to the waste of the instrument, they can be collected for further studies including DNA sequencing as well as other genomic, in vitro and in vivo experiments. This chapter aims to give an overview of cell sorting, the different types of cell sorters, details on how a cell sorter works, as well as protocols that are useful when embarking on a journey with cell sorting.

Lrig1 expression identifies airway basal cells with high proliferative capacity and restricts lung squamous cell carcinoma growth.

BACKGROUND: Lung squamous cell carcinoma (LUSC) accounts for a significant proportion of cancer deaths worldwide, and is preceded by the appearance of progressively disorganised pre-invasive lesions in the airway epithelium. Yet the biological mechanisms underlying progression of pre-invasive lesions into invasive LUSC are not fully understood. LRIG1 (leucine-rich repeats and immunoglobulin-like domains 1) is downregulated in pre-invasive airway lesions and invasive LUSC tumours and this correlates with decreased lung cancer patient survival. METHODS AND RESULTS: Using an Lrig1 knock-in reporter mouse and human airway epithelial cells collected at bronchoscopy, we show that during homeostasis LRIG1 is heterogeneously expressed in the airway epithelium. In basal airway epithelial cells, the suspected cell of origin of LUSC, LRIG1 identifies a subpopulation of progenitor cells with higher in vitro proliferative and self-renewal potential in both the mouse and human. Using the N-nitroso-tris-chloroethylurea (NTCU)-induced murine model of LUSC, we find that Lrig1 loss-of-function leads to abnormally high cell proliferation during the earliest stages of pre-invasive disease and to the formation of significantly larger invasive tumours, suggesting accelerated disease progression. CONCLUSION: Together, our findings identify LRIG1 as a marker of basal airway progenitor cells with high proliferative potential and as a regulator of pre-invasive lung cancer progression. This work highlights the clinical relevance of LRIG1 and the potential of the NTCU-induced LUSC model for functional assessment of candidate tumour suppressors and oncogenes.

Inhibition of Invasion by Polyphenols from Citrus Fruit and Berries in Human Malignant Glioma Cells In Vitro.

BACKGROUND/AIM: The outlook for patients with high grade glioma (HGG) remains dismal. Hence, attention has focused on numerous innovative treatments. Our group has proposed a strategy on the use of a combination of polyphenols, as anti-invasive agents for the management of these neoplasms. MATERIALS AND METHODS: The aim of this study was to evaluate the in vitro effects of citrus flavonoids (tangeretin, nobiletin, naringin and limonin) and berry extracts (chokeberry, elderberry and bilberry) on selected mediators of invasion in 2 HGG cell cultures. RESULTS: The IC50 values could only be determined for tangeretin and chokeberry extract. The rest were non-functional in this context. Immunocytochemistry and flow cytometry results showed that chokeberry extract was most effective in down-regulating the expression of CD44. Similarly, RT-PCR data supported its ability to reduce gene expression of MMP-14 and EGFR. 2D invasion assays confirmed that inhibition is greater with chokeberry extract. CONCLUSION: Both polyphenols have anti-invasive potential but chokeberry extract is a stronger agent for glioma management.

DRAQ7 as an Alternative to MTT Assay for Measuring Viability of Glioma Cells Treated With Polyphenols.

BACKGROUND/AIM: The tetrazolium-based MTT cytotoxicity assay is well established for screening putative anti-cancer agents. However, it has limitations including lack of reproducibility with glioma cells treated with polyphenols. The aim of this study was to evaluate whether a flow cytometric assay with the anthraquinone, DRAQ7, was a better alternative than the colorimetric MTT assay for measuring cell viability. MATERIALS AND METHODS: Two glioma cell lines (IPSB-18, U373) and 1 pancreatic cancer cell line (AsPC-1) were treated with 4 polyphenols, namely red grape seed extract, red clover extract, anthocyanin-rich extract and curcumin. Cell viability was assessed using MTT assay and DRAQ7 staining. RESULTS: Limitations of MTT assay included lack of sensitivity and interference with the structure and absorbance spectra of polyphenols. Also, DMSO was toxic to glioma cells. Microscopic observations of cells treated with polyphenols confirmed the range of IC50 values evaluated by DRAQ7, but not by the MTT assay. CONCLUSION: DRAQ7 is a better alternative than MTT for measuring viability of glioma cells treated with brightly coloured polyphenols.

Sourcing the immune system to induce immunogenic cell death in Kras-colorectal cancer cells.

BACKGROUND: Current approaches aimed at inducing immunogenic cell death (ICD) to incite an immune response against cancer neoantigens are based on the use of chemotherapeutics and other agents. Results are hampered by issues of efficacy, combinatorial approaches, dosing and toxicity. Here, we adopted a strategy based on the use of an immunomolecule that overcomes pharmachemical limitations. METHODS: Cytofluorometry, electron microscopy, RT-PCR, western blotting, apotome immunofluorescence, MLR and xenografts. RESULTS: We report that an ICD process can be activated without the use of pharmacological compounds. We show that in Kras-mut/TP53-mut colorectal cancer cells the 15 kDa ßGBP cytokine, a T cell effector with onco-suppressor properties and a potential role in cancer immunosurveillance, induces key canonical events required for ICD induction. We document ER stress, autophagy that extends from cancer cells to the corresponding xenograft tumours, CRT cell surface shifting, ATP release and evidence of dendritic cell activation, a process required for priming cytotoxic T cells into a specific anticancer immunogenic response. CONCLUSIONS: Our findings provide experimental evidence for a rationale to explore a strategy based on the use of an immunomolecule that as a single agent couples oncosuppression with the activation of procedures necessary for the induction of long term response to cancer.

International Society for Advancement of Cytometry (ISAC) flow cytometry shared resource laboratory (SRL) best practices.

The purpose of this document is to define minimal standards for a flow cytometry shared resource laboratory (SRL) and provide guidance for best practices in several important areas. This effort is driven by the desire of International Society for the Advancement of Cytometry (ISAC) members in SRLs to define and maintain standards of excellence in flow cytometry, and act as a repository for key elements of this information (e.g. example SOPs/training material, etc.). These best practices are not intended to define specifically how to implement these recommendations, but rather to establish minimal goals for an SRL to address in order to achieve excellence. It is hoped that once these best practices are established and implemented they will serve as a template from which similar practices can be defined for other types of SRLs. Identification of the need for best practices first occurred through discussions at the CYTO 2013 SRL Forum, with the most important areas for which best practices should be defined identified through several surveys and SRL track workshops as part of CYTO 2014. © 2016 International Society for Advancement of Cytometry.

Label-free cell cycle analysis for high-throughput imaging flow cytometry.

Imaging flow cytometry combines the high-throughput capabilities of conventional flow cytometry with single-cell imaging. Here we demonstrate label-free prediction of DNA content and quantification of the mitotic cell cycle phases by applying supervised machine learning to morphological features extracted from brightfield and the typically ignored darkfield images of cells from an imaging flow cytometer. This method facilitates non-destructive monitoring of cells avoiding potentially confounding effects of fluorescent stains while maximizing available fluorescence channels. The method is effective in cell cycle analysis for mammalian cells, both fixed and live, and accurately assesses the impact of a cell cycle mitotic phase blocking agent. As the same method is effective in predicting the DNA content of fission yeast, it is likely to have a broad application to other cell types.

Roles of SLX1-SLX4, MUS81-EME1, and GEN1 in avoiding genome instability and mitotic catastrophe.

The resolution of recombination intermediates containing Holliday junctions (HJs) is critical for genome maintenance and proper chromosome segregation. Three pathways for HJ processing exist in human cells and involve the following enzymes/complexes: BLM-TopoIIIα-RMI1-RMI2 (BTR complex), SLX1-SLX4-MUS81-EME1 (SLX-MUS complex), and GEN1. Cycling cells preferentially use the BTR complex for the removal of double HJs in S phase, with SLX-MUS and GEN1 acting at temporally distinct phases of the cell cycle. Cells lacking SLX-MUS and GEN1 exhibit chromosome missegregation, micronucleus formation, and elevated levels of 53BP1-positive G1 nuclear bodies, suggesting that defects in chromosome segregation lead to the transmission of extensive DNA damage to daughter cells. In addition, however, we found that the effects of SLX4, MUS81, and GEN1 depletion extend beyond mitosis, since genome instability is observed throughout all phases of the cell cycle. This is exemplified in the form of impaired replication fork movement and S-phase progression, endogenous checkpoint activation, chromosome segmentation, and multinucleation. In contrast to SLX4, SLX1, the nuclease subunit of the SLX1-SLX4 structure-selective nuclease, plays no role in the replication-related phenotypes associated with SLX4/MUS81 and GEN1 depletion. These observations demonstrate that the SLX1-SLX4 nuclease and the SLX4 scaffold play divergent roles in the maintenance of genome integrity in human cells.

Systemic but not topical TRAIL-expressing mesenchymal stem cells reduce tumour growth in malignant mesothelioma.

Malignant pleural mesothelioma is a rare but devastating cancer of the pleural lining with no effective treatment. The tumour is often diffusely spread throughout the chest cavity, making surgical resection difficult, while systemic chemotherapy offers limited benefit. Bone marrow-derived mesenchymal stem cells (MSCs) home to and incorporate into tumour stroma, making them good candidates to deliver anticancer therapies. Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) is a pro-apoptotic molecule that selectively induces apoptosis in cancer cells, leaving healthy cells unaffected. We hypothesised that human MSCs expressing TRAIL (MSCTRAIL) would home to an in vivo model of malignant pleural mesothelioma and reduce tumour growth. Human MSCs transduced with a lentiviral vector encoding TRAIL were shown in vitro to kill multiple malignant mesothelioma cell lines as predicted by sensitivity to recombinant TRAIL (rTRAIL). In vivo MSC homing was delineated using dual fluorescence and bioluminescent imaging, and we observed that higher levels of MSC engraftment occur after intravenous delivery compared with intrapleural delivery of MSCs. Finally, we show that intravenous delivery of MSCTRAIL results in a reduction in malignant pleural mesothelioma tumour growth in vivo via an increase in tumour cell apoptosis.

RhoC interacts with integrin α5ß1 and enhances its trafficking in migrating pancreatic carcinoma cells.

Human pancreatic ductal adenocarcinoma (PDAC) is characterized by early systemic dissemination. Although RhoC has been implicated in cancer cell migration, the relevant underlying molecular mechanisms remain unknown. RhoC has been implicated in the enhancement of cancer cell migration and invasion, with actions which are distinct from RhoA (84% homology), and are possibly attributed to the divergent C-terminus domain. Here, we confirm that RhoC significantly enhances the migratory and invasive properties of pancreatic carcinoma cells. In addition, we show that RhoC over-expression decreases cancer cell adhesion and, in turn, accelerates cellular body movement and focal adhesion turnover, especially, on fibronectin-coated surfaces. Whilst RhoC over-expression did not alter integrin expression patterns, we show that it enhanced integrin α5ß1 internalization and re-cycling (trafficking), an effect that was dependent specifically on the C-terminus (180-193 amino acids) of RhoC protein. We also report that RhoC and integrin α5ß1 co-localize within the peri-nuclear region of pancreatic tumor cells, and by masking the CAAX motif at the C-terminal of RhoC protein, we were able to abolish this interaction in vitro and in vivo. Co-localization of integrin α5ß1 and RhoC was demonstrable in invading cancer cells in 3D-organotypic cultures, and further mimicked in vivo analyses of, spontaneous human, (two distinct sources: operated patients and rapid autopsy programme) and transgenic murine (LSL-KrasG12D/+;LSL-Trp53R172H/+;Pdx-1-Cre), pancreatic cancers. In both cases, co-localization of integrin α5ß1 and RhoC correlated with poor differentiation status and metastatic potential. We propose that RhoC facilitates tumor cell invasion and promotes subsequent metastasis, in part, by enhancing integrin α5ß1 trafficking. Thus, RhoC may serve as a biomarker and a therapeutic target.

A method for evaluating the use of fluorescent dyes to track proliferation in cell lines by dye dilution.

Labeling nonquiescent cells with carboxyfluorescein succinimidyl ester (CFSE)-like dyes gives rise to a population width exceeding the threshold for resolving division peaks by flow cytometry. Width is a function of biological heterogeneity plus extrinsic and intrinsic error sources associated with the measurement process. Optimal cytometer performance minimizes extrinsic error, but reducing intrinsic error to the point of facilitating peak resolution requires careful fluorochrome selection and fluorescent cell sorting. In this study, we labeled the Jurkat and A549 cell lines with CFSE, CellTraceViolet (CTV), and eFluor 670 proliferation dye (EPD) to test if we could resolve division peaks in culture after reducing the labeled input widths by cell sorting. Reanalysis of the sorted populations to ascertain the level of reduction achieved always led to widths exceeding the gated limits due to the contribution of errors. Measuring detector-specific extrinsic error by sorting uniform fluorescent particles with similar spectral properties to the tracking dyes allowed us to determine the intrinsic error for each dye and cell type using a simple mathematical approach. We found that cell intrinsic error ultimately dictated whether we could resolve division peaks, and that as this increased, the required sort gate width to resolve any division peaks decreased to the point whereby issues with yield made A549 unsuitable for this approach. Finally, attempts to improve yields by setting two concurrent sort gates on the fluorescence distribution enriched for cells in different stages of the cell cycle that had nonequivalent proliferative properties in culture and thus should be practiced with caution.

Follicular lymphoma cells induce changes in T-cell gene expression and function: potential impact on survival and risk of transformation.

PURPOSE: Previous studies have demonstrated the prognostic importance of the immune microenvironment in follicular lymphoma (FL). To investigate the molecular mechanisms during which tumor-infiltrating T cells (TILs) are altered in the FL microenvironment, we studied highly purified CD4 and CD8 TILs from lymph node biopsies at diagnosis in treatment-naive patients with FL compared with reactive tonsils and the peripheral blood of healthy donors. PATIENTS AND METHODS: Gene expression profiling of highly purified CD4 and CD8 TILs was performed on the Affymetrix platform. Diagnostic tissue microarrays from an independent patient set (n = 172) were used to verify protein expression and analyze any impact of TIL-expressed genes on outcome. Time-lapse imaging was used to assess T-cell motility. RESULTS: The most upregulated genes in both CD4 and CD8 TILs were PMCH, ETV1, and TNFRSF9. PMCH is not expressed in peripheral blood T cells, but expression is highly induced on culture with FL. Both CD4 and CD8 TILs from patients with FL have significantly impaired motility compared with those of healthy TILs from reactive tonsils and this can be induced on healthy T cells by FL cells. During multivariate analysis, a model incorporating the number and location of T cells expressing PMCH, NAMPT, and ETV1 showed prognostic significance for overall survival and for time to transformation. CONCLUSION: We showed altered gene expression in TILs in FL and demonstrated that altering the immune microenvironment in FL affects overall survival and time to transformation in this disease.

Regulation of asymmetric cell division and polarity by Scribble is not required for humoral immunity.

The production of protective antibody requires effective signalling of naive B cells following encounter with antigen, and the divergence of responding B lymphocytes into distinct lineages. Polarity proteins have recently been proposed as important mediators of both the initial B cell response, and potentially of asymmetric cell division. Here we show that, although polarity proteins of the Scribble complex, Scribble, Dlg1 and Lgl1, are expressed and polarized during early B cell activation, their deficiency has no effect on the in vivo outcome of immunization or challenge with influenza infection. Furthermore, we find a striking correlation in the differentiation outcome of daughters of single founder B cells in vitro. Taken together, our results indicate that B cell differentiation does not require polarity proteins of the Scribble complex, and the findings do not support a role for asymmetric cell division in B cell activation and differentiation.

Induction of apoptosis and reduction of MMP gene expression in the U373 cell line by polyphenolics in Aronia melanocarpa and by curcumin.

Malignant brain tumours are rare but are the most challenging types of cancers to treat. Despite conventional multimodality approaches available for their management, the outlook for most patients remains dismal due to the ability of the tumour cells to invade the normal brain. Attention has now focused on novel therapeutic interventions such as as the use of micronutrients. Both chokeberry extract (Aronia melanocarpa), which is rich in natural pigments such as anthocyanins and curcumin (diferuloylmethane) found in turmeric (Curcuma longa) have been reported to possess anticancer properties in other cancers. The aim of this study was to extend our previous research to evaluate the therapeutic potential of these two agents by testing their ability to induce apoptosis in an established glioblastoma cell line (U373). This was accomplished by treating the cells for 48 h with either chokeberry extract or curcumin, and using the Annexin-V assay. Gene profiles of 8 MMPs (2, 9, 14, 15, 16, 17, 24 and 25) and 4 TIMPs (1, 2, 3 and 4) were analysed for effects of mediators of invasion by quantitative real-time polymerase chain reaction (RT-PCR). The IC50 values determined for curcumin and chokeberry extract were 15 and 200 µg/ml, respectively. Our results also suggest that curcumin induces apoptosis but chokeberry extract is necrotic to this cell line. It is possible that chokeberry extract kills the cells by other non-apoptotic pathways. In addition, the RT-PCR results show downregulation of the gene expression of MMP-2, -14, -16 and -17 for both micronutrients. Taken together, the comparative data suggest that both curcumin and chokeberry extract may exhibit their anticancer potential by inducing apoptosis and inhibiting invasion by reducing MMP gene expression.