Laser Scanning Cytometry and Its Applications: A Pioneering Technology in the Field of Quantitative Imaging Cytometry

Quantitative phase imaging of living red blood cells combining digital holographic microscopy and deep learning

Digital holographic microscopy as a non-contacting, non-invasive, and highly accurate measurement technology, is becoming a valuable method for quantitatively investigating cells and tissues. Reconstruction of phases from a digital hologram is a key step in quantitative phase imaging for biological and biomedical research. This study proposes a two-stage deep convolutional neural network named VY-Net, to realize the effective and robust phase reconstruction of living red blood cells. The VY-Net can obtain the phase information of an object directly from a single-shot off-axis digital hologram. We also propose two new indices to evaluate the reconstructed phases. In experiments, the mean of the structural similarity index of reconstructed phases can reach 0.9309, and the mean of the accuracy of reconstructions of reconstructed phases is as high as 91.54%. An unseen phase map of a living human white blood cell is successfully reconstructed by the trained VY-Net, demonstrating its strong generality.

Design, Synthesis, and Biological Evaluation of a Novel VEGFR-2 Inhibitor Based on a 1,2,5-Oxadiazole-2-Oxide Scaffold with MAPK Signaling Pathway Inhibition

Over the past few decades, the development of broad-spectrum anticancer agents with anti-angiogenic activity has witnessed considerable progress. In this study, a new series of pyrazolo[3,4-d]pyrimidines based on a phenylfuroxan scaffold were designed, synthesized, and evaluated, in terms of their anticancer activities. NCI-60 cell one-dose screening revealed that compounds 12a–c and 14a had the best MGI%, among the tested compounds. The target fluorinated compound 12b, as the most active one, showed better anticancer activity compared to the reference drug sorafenib, with IC₅₀ values of 11.5, 11.6, and 13 µM against the HepG-2, A2780CP, and MDA-MB-231 cell lines, respectively. Furthermore, compound 12b (IC₅₀ = 0.092 µM) had VEGFR-2-inhibitory activity comparable to that of the standard inhibitor sorafenib (IC₅₀ = 0.049 µM). Furthermore, the ability of compound 12b in modulating MAPK signaling pathways was investigated. It was found to decrease the level of total ERK and its phosphorylated form, as well as leading to the down-regulation of metalloproteinase MMP-9 and the over-expression of p21 and p27, thus leading to subG1 cell-cycle arrest and, thus, the induction of apoptosis. Additionally, compound 12b decreased the rate of wound healing in the absence of serum, in comparison to DMSO-treated cells, providing a significant impact on metastasis inhibition. The quantitative RT-PCR results for E-cadherin and N-cadherin showed lower expression of the neuronal N-cadherin and increased expression of epithelial E-cadherin, indicating the ability of 12b to suppress metastasis. Furthermore, 12b-treated HepG2 cells expressed a low level of anti-apoptotic BCL-2 and over-expressed proapoptotic Bax genes, respectively. Using the DAF-FM DA fluorescence probe, compound 12b produced NO intracellularly as efficiently as the reference drug JS-K. In silico molecular docking studies showed a structural similarity through an overlay of 12b with sorafenib. Interestingly, the drug-likeness properties of compound 12b met the expectations of Pfizer’s rule for the design of new drug candidates. Therefore, this study presents a novel anticancer lead compound that is worthy of further investigation and activity improvement.

Multiplex Stimulated Raman Scattering Imaging Cytometry Reveals Lipid-Rich Protrusions in Cancer Cells under Stress Condition

In situ measurement of cellular metabolites is still a challenge in biology. Conventional methods, such as mass spectrometry or fluorescence microscopy, would either destroy the sample or introduce strong perturbations to target molecules. Here, we present multiplex stimulated Raman scattering (SRS) imaging cytometry as a label-free single-cell analysis platform with chemical specificity and high-throughput capabilities. Using SRS imaging cytometry, we studied the metabolic responses of human pancreatic cancer cells under stress by starvation and chemotherapeutic drug treatments. We unveiled protrusions containing lipid droplets as a metabolic marker for stress-resistant cancer cells. Furthermore, by spectroscopic SRS mapping, we unveiled that triglyceride in lipid droplets are used for local energy production through lipolysis, autophagy, and β-oxidation. Our findings demonstrate the potential of targeting lipid metabolism for selective treatment of stress-resistant cancers. Collectively, these results highlight SRS imaging cytometry as a powerful label-free tool for biological discoveries with a high-throughput, high-content capacity.

Direct Cytosolic Delivery of Proteins through Coengineering of Proteins and Polymeric Delivery Vehicles

Nanocarrier-mediated protein delivery is a promising strategy for fundamental research and therapeutic applications. However, the efficacy of the current platforms for delivery into cells is limited by endosomal entrapment of delivered protein cargo with concomitantly inefficient access to the cytosol and other organelles, including the nucleus. We report here a robust, versatile polymeric-protein nanocomposite (PPNC) platform capable of efficient (≥90%) delivery of proteins to the cytosol. We synthesized a library of guanidinium-functionalized poly(oxanorborneneimide) (PONI) homopolymers with varying molecular weights to stabilize and deliver engineered proteins featuring terminal oligoglutamate "E-tags". The polymers were screened for cytosolic delivery efficiency using imaging flow cytometry with cytosolic delivery validated using confocal microscopy and activity of the delivered proteins demonstrated through functional assays. These studies indicate that the PPNC platform provides highly effective and tunable cytosolic delivery over a wide range of formulations, making them robust agents for therapeutic protein delivery.

Recent advances in tissue imaging for cancer research

Image analysis in clinical research has evolved at fast pace in the last decade. This review discusses basic concepts ranging from immunohistochemistry to advanced techniques such as multiplex imaging, digital pathology, flow cytometry and intravital microscopy. Tissue imaging ex vivo is still one of the gold-standards in the field due to feasibility. We describe here different protocols and applications of digital analysis providing basic and clinical researchers with an overview on how to analyse tissue images. In vivo imaging is not easily accessible to researchers; however, it provides invaluable dynamic information. Overall, we discuss a plethora of techniques that - when combined - constitute a powerful platform for basic and translational cancer research.

Of Cytometry, Stem Cells and Fountain of Youth

Outlined are advances of cytometry applications to identify and sort stem cells, of laser scanning cytometry and ImageStream imaging instrumentation to further analyze morphometry of these cells, and of mass cytometry to classify a multitude of cellular markers in large cell populations. Reviewed are different types of stem cells, including potential candidates for cancer stem cells, with respect to their "stemness", and other characteristics. Appraised is further progress in identification and isolation of the "very small embryonic-like stem cells" (VSELs) and their autogenous transplantation for tissue repair and geroprotection. Also assessed is a function of hyaluronic acid, the major stem cells niche component, as a guardian and controller of stem cells. Briefly appraised are recent advances and challenges in the application of stem cells in regenerative medicine and oncology and their future role in different disciplines of medicine, including geriatrics.

High accuracy label-free classification of single-cell kinetic states from holographic cytometry of human melanoma cells

Digital holographic cytometry (DHC) permits label-free visualization of adherent cells. Dozens of cellular features can be derived from segmentation of hologram-derived images. However, the accuracy of single cell classification by these features remains limited for most applications, and lack of standardization metrics has hindered independent experimental comparison and validation. Here we identify twenty-six DHC-derived features that provide biologically independent information across a variety of mammalian cell state transitions. When trained on these features, machine-learning algorithms achieve blind single cell classification with up to 95% accuracy. Using classification accuracy to guide platform optimization, we develop methods to standardize holograms for the purpose of kinetic single cell cytometry. Applying our approach to human melanoma cells treated with a panel of cancer therapeutics, we track dynamic changes in cellular behavior and cell state over time. We provide the methods and computational tools for optimizing DHC for kinetic single adherent cell classification.

Greatwall promotes cell transformation by hyperactivating AKT in human malignancies

The PP2A phosphatase is often inactivated in cancer and is considered as a tumour suppressor. A new pathway controlling PP2A activity in mitosis has been recently described. This pathway includes the Greatwall (GWL) kinase and its substrates endosulfines. At mitotic entry, GWL is activated and phosphorylates endosulfines that then bind and inhibit PP2A. We analysed whether GWL overexpression could participate in cancer development. We show that GWL overexpression promotes cell transformation and increases invasive capacities of cells through hyperphosphorylation of the oncogenic kinase AKT. Interestingly, AKT hyperphosphorylation induced by GWL is independent of endosulfines. Rather, GWL induces GSK3 kinase dephosphorylation in its inhibitory sites and subsequent SCF-dependent degradation of the PHLPP phosphatase responsible for AKT dephosphorylation. In line with its oncogenic activity, we find that GWL is often overexpressed in human colorectal tumoral tissues. Thus, GWL is a human oncoprotein that promotes the hyperactivation of AKT via the degradation of its phosphatase, PHLPP, in human malignancies.

Laser-scanning cytometry can quantify human adipocyte browning and proves effectiveness of irisin

Laser-scanning cytometry is presented as a tool allowing population scale analysis of ex vivo human brown adipogenic differentiation. It combines texture analysis and detection of Ucp1 protein content in single brown adipocytes of mixed cell populations with gene expression pattern and functional characteristics of browning. Using this method we could validate mouse data in human samples demonstrating the effectiveness of irisin to induce “beige” differentiation of subcutaneous white adipocytes.

AMG 900, a potent inhibitor of aurora kinases causes pharmacodynamic changes in p-Histone H3 immunoreactivity in human tumor xenografts and proliferating mouse tissues

BACKGROUND

The Aurora family of serine-threonine kinases are essential regulators of cell division in mammalian cells. Aurora-A and -B expression and kinase activity is elevated in a variety of human cancers and is associated with high proliferation rates and poor prognosis. AMG 900 is a highly potent and selective pan-aurora kinase inhibitor that has entered clinical evaluation in adult patients with advanced cancers. In mice, oral administration of AMG 900 blocks the phosphorylation of histone H3 on serine-10 (p-Histone H3), a proximal substrate of aurora-B and inhibits the growth of multiple human tumor xenografts, including multidrug-resistant models.

METHODS

In order to establish a preclinical pharmacokinetic-pharmacodynamic (PK-PD) relationship for AMG 900 that could be translated to the clinic, we used flow cytometry and laser scanning cytometry detection platforms to assess the effects on p-Histone H3 inhibition in terms of sensitivity, precision, and specificity, in human tumor xenografts in conjunction with mouse skin and bone marrow tissues. Mice with established COLO 205 tumors were administered AMG 900 at 3.75, 7.5, and 15 mg/kg and assessed after 3 hours.

RESULTS

Significant suppression of p-Histone H3 in mouse skin was only observed at 15 mg/kg (p <0.0001), whereas in mouse bone marrow and in tumor a dose-dependent inhibition was achieved at all three doses (p ≤ 0.00015). These studies demonstrate that AMG 900 inhibits p-Histone H3 in tumors and surrogate tissues (although tissues such as skin may be less sensitive for assessing PD effects). To further extend our work, we evaluated the feasibility of measuring p-Histone H3 using fine-needle aspirate (FNA) tumor xenograft biopsies. Treatment with AMG 900 significantly inhibited p-Histone H3 (>99% inhibition, p <0.0001) in COLO 205 tumors. Lastly, we illustrate this LSC-based approach can detect p-Histone H3 positive cells using mock FNAs from primary human breast tumor tissues.

CONCLUSION

Phosphorylation of histone H3 is a useful biomarker to determine the pharmacodynamics (PD) activity of AMG 900. FNA biopsies may be a viable approach for assessing AMG 900 PD effects in the clinic.

Attenuation of replication stress-induced premature cellular senescence to assess anti-aging modalities

Described is an in vitro model of premature senescence in pulmonary adenocarcinoma A549 cells induced by persistent DNA replication stress in response to treatment with the DNA damaging drug mitoxantrone (Mxt). The degree of cellular senescence, based on characteristic changes in cell morphology, is measured by laser scanning cytometry. Specifically, the flattening of cells grown on slides (considered the hallmark of cellular senescence) is measured as the decline in local intensity of DNA-associated DAPI fluorescence (represented by maximal pixels). This change is paralleled by an increase in nuclear area. Thus, the ratio of mean intensity of maximal pixels to nuclear area provides a very sensitive morphometric biomarker for the degree of senescence. This analysis is combined with immunocytochemical detection of senescence markers, such as overexpression of cyclin kinase inhibitors (e.g., p21(WAF1) ) and phosphorylation of ribosomal protein S6 (rpS6), a key marker associated with aging/senescence that is detected using a phospho-specific antibody. These biomarker indices are presented in quantitative terms defined as a senescence index (SI), which is the fraction of the marker in test cultures relative to the same marker in exponentially growing control cultures. This system can be used to evaluate the anti-aging potential of test agents by assessing attenuation of maximal senescence. As an example, the inclusion of berberine, a natural alkaloid with reported anti-aging properties and a long history of use in traditional Chinese medicine, is shown to markedly attenuate the Mxt-induced SI and phosphorylation of rpS6. The multivariate analysis of senescence markers by laser scanning cytometry offers a promising tool to explore the potential anti-aging properties of a variety agents.

New insights into cell cycle and DNA damage response machineries through high-resolution AMICO quantitative imaging cytometry

OBJECTIVE

Progress in biology and medicine research is being driven by development of new instrumentation and associated methodologies which open analytical capabilities that expand understanding of complexity of biological systems. Application of cytometry, which is now widely used in so many disciplines of biology, is the best example of such a progress.

METHODOLOGY

Recent publications push the envelope in expanding capabilities of cytometry by introducing a high resolution imaging cytometry defined as Automated Microscopy for Image CytOmetry (AMICO). This instrumentation is utilized to further elucidate mechanisms of the cell cycle progression and also the DNA damage response. This approach is going beyond the presently possible analytical technologies regarding throughput and depth of information.

CONCLUSIONS

The possibility of multiparametric analysis combined with the high resolution mapping of individual constituents of cell cycle and DNA damage response machineries provides new tools to probe molecular mechanism of these processes. The capability of analysis of proximity of these constituents to each other offered by AMICO is a novel and potentially important approach that can be used to elucidate mechanisms of other biological processes.

HIPK1 drives p53 activation to limit colorectal cancer cell growth

HIPK1 (homeodomain interacting protein kinase 1) is a serine/threonine kinase that belongs to the CMGC superfamily. Emerging data point to the role of HIPK1 in cancer, but it is still not clear whether it acts as a tumor suppressor or promoter. Here we identified HIPK1 as a kinase that is significantly overexpressed in colorectal cancer (CRC) and whose expression is stage-dependent. Being abundantly expressed at the onset of the disease, the HIPK1 level gradually decreased as tumor stage progressed. To further uncover how this factor regulates tumorigenesis and establish whether it constitutes an early factor necessary for neoplastic transformation or for cellular defense, we studied the effect of its overexpression in vitro by investigating various cancer-related signaling cascades. We found that HIPK1 mostly regulates the p53 signaling pathway both in HCT116 and HeLa cells. By phosphorylating p53 on its serine-15, HIPK1 favored its transactivation potential, which led to a rise in p21 protein level and a decline in cell proliferation. Assuming that HIPK1 could impede CRC growth by turning on the p53/p21 pathway, we then checked p21 mRNA levels in patients. Interestingly, p21 transcripts were only increased in a subset of patients expressing high levels of HIPK1. Unlike the rest of the cohort, the majority of these patients hosted a native p53 protein, meaning that such a pro-survival pathway (HIPK1+ > p53 > p21) is active in patients, and that HIPK1 acts rather as a tumor suppressor.

Multiparameter flow cytometry: advances in high resolution analysis

Over the past 40 years, flow cytometry has emerged as a leading, application-rich technology that supports high-resolution characterization of individual cells which function in complex cellular networks such as the immune system. This brief overview highlights advances in multiparameter flow cytometric technologies and reagent applications for characterization and functional analysis of cells modulating the immune network. These advances significantly support high-throughput and high-content analyses and enable an integrated understanding of the cellular and molecular interactions that underlie complex biological systems.

HUMN project initiative and review of validation, quality control and prospects for further development of automated micronucleus assays using image cytometry systems

The use of micronucleus (MN) assays in in vitro genetic toxicology testing, radiation biodosimetry and population biomonitoring to study the genotoxic impacts of environment gene-interactions has steadily increased over the past two decades. As a consequence there has been a strong interest in developing automated systems to score micronuclei, a biomarker of chromosome breakage or loss, in mammalian and human cells. This paper summarises the outcomes of a workshop on this topic, organised by the HUMN project, at the 6th International Conference on Environmental Mutagenesis in Human Populations at Doha, Qatar, 2012. The aim of this paper is to summarise the outcomes of the workshop with respect to the set objectives which were: (i) Review current developments in automation of micronucleus assays by image cytometry; (ii) define the performance characteristics of automated MN scoring using image cytometry and methods of assessment for instrument validation and quality control and (iii) discuss the design of inter-laboratory comparisons and standardisation of micronucleus assays using automated image cytometry systems. It is evident that automated scoring of micronuclei by automated image cytometry using different commercially available platforms [e.g. Metafer (MetaSystems), Pathfinder™ (IMSTAR), iCyte(®) (Compucyte)], particularly for lymphocytes, is at a mature stage of development with good agreement between visual and automated scoring across systems (correlation factors ranging from 0.58 to 0.99). However, a standardised system of validation and calibration is required to enable more reliable comparison of data across laboratories and across platforms. This review identifies recent progress, important limitations and steps that need to be taken into account to enable the successful universal implementation of automated micronucleus assays by image cytometry.

DNA damage signaling assessed in individual cells in relation to the cell cycle phase and induction of apoptosis

Reviewed are the phosphorylation events reporting activation of protein kinases and the key substrates critical for the DNA damage signaling (DDS). These DDS events are detected immunocytochemically using phospho-specific Abs; flow cytometry or image-assisted cytometry provide the means to quantitatively assess them on a cell by cell basis. The multiparameter analysis of the data is used to correlate these events with each other and relate to the cell cycle phase, DNA replication and induction of apoptosis. Expression of γH2AX as a possible marker of induction of DNA double strand breaks is the most widely studied event of DDS. Reviewed are applications of this multiparameter approach to investigate constitutive DDS reporting DNA damage by endogenous oxidants byproducts of oxidative phosphorylation. Also reviewed are its applications to detect and explore mechanisms of DDS induced by variety of exogenous agents targeting DNA such as exogenous oxidants, ionizing radiation, radiomimetic drugs, UV light, DNA topoisomerase I and II inhibitors, DNA crosslinking drugs and variety of environmental genotoxins. Analysis of DDS induced by these agents provides often a wealth of information about mechanism of induction and the type of DNA damage (lesion) and is reviewed in the context of cell cycle phase specificity, DNA replication, and induction of apoptosis or cell senescence. Critically assessed is interpretation of the data as to whether the observed DDS events report induction of a particular type of DNA lesion.

Circulating tumor cells in hepatocellular carcinoma: detection techniques, clinical implications, and future perspectives

Hepatocellular carcinoma (HCC) is a primary liver cancer with a huge challenge in terms of its complex etiology and its management. The fact that the most common site of early tumor recurrence in liver transplantation for HCC is the transplanted allograft strongly suggests that circulating tumor cells (CTCs) are really an active source of HCC metastasis or recurrence. In the past decade, with the tremendous progress in the technology of CTC detection, there is convincing evidence that CTCs have great potential as a marker for metastatic disease and poor prognosis in patients with a malignancy. Currently some interesting and encouraging results have been achieved in HCC CTC detection, although the knowledge about its clinical relevance in HCC is lagging behind other major tumor types. Here we will review existing and developing methodologies for CTC detection, discuss future perspectives, and describe the potential clinical impact of the identification and molecular characterization of CTC subset or circulating cancer stem cells in HCC patients. Particular attention is given to the results based on the HCC CTC study.

Imaging flow cytometry: coping with heterogeneity in biological systems

Imaging flow cytometry (IFC) platforms combine features of flow cytometry and fluorescent microscopy with advances in data-processing algorithms. IFC allows multiparametric fluorescent and morphological analysis of thousands of cellular events and has the unique capability of identifying collected events by their real images. IFC allows the analysis of heterogeneous cell populations, where one of the cellular components has low expression (<0.03%) and can be described by Poisson distribution. With the help of IFC, one can address a critical question of statistical analysis of subcellular distribution of proteins in a cell. Here the authors review advantages of IFC in comparison with more traditional technologies, such as Western blotting and flow cytometry (FC), as well as new high-throughput fluorescent microscopy (HTFM), and discuss further developments of this novel analytical technique.

Analysis of cell cycle and replication of mouse macrophages after in vivo and in vitro Cryptococcus neoformans infection using laser scanning cytometry

We investigated the outcome of the interaction of Cryptococcus neoformans with murine macrophages using laser scanning cytometry (LSC). Previous results in our lab had shown that phagocytosis of C. neoformans promoted cell cycle progression. LSC allowed us to simultaneously measure the phagocytic index, macrophage DNA content, and 5-ethynyl-2'-deoxyuridine (EdU) incorporation such that it was possible to study host cell division as a function of phagocytosis. LSC proved to be a robust, reliable, and high-throughput method for quantifying phagocytosis. Phagocytosis of C. neoformans promoted cell cycle progression, but infected macrophages were significantly less likely to complete mitosis. Hence, we report a new cytotoxic effect associated with intracellular C. neoformans residence that manifested itself in impaired cell cycle completion as a consequence of a block in the G(2)/M stage of the mitotic cell cycle. Cell cycle arrest was not due to increased cell membrane permeability or DNA damage. We investigated alveolar macrophage replication in vivo and demonstrated that these cells are capable of low levels of cell division in the presence or absence of C. neoformans infection. In summary, we simultaneously studied phagocytosis, the cell cycle state of the host cell and pathogen-mediated cytotoxicity, and our results demonstrate a new cytotoxic effect of C. neoformans infection on murine macrophages: fungus-induced cell cycle arrest. Finally, we provide evidence for alveolar macrophage proliferation in vivo.