Artificial confocal microscopy for deep label-free imaging.

Widefield microscopy of optically thick specimens typically features reduced contrast due to "spatial crosstalk", in which the signal at each point in the field of view is the result of a superposition from neighbouring points that are simultaneously illuminated. In 1955, Marvin Minsky proposed confocal microscopy as a solution to this problem. Today, laser scanning confocal fluorescence microscopy is broadly used due to its high depth resolution and sensitivity, but comes at the price of photobleaching, chemical, and photo-toxicity. Here, we present artificial confocal microscopy (ACM) to achieve confocal-level depth sectioning, sensitivity, and chemical specificity, on unlabeled specimens, nondestructively. We equipped a commercial laser scanning confocal instrument with a quantitative phase imaging module, which provides optical path-length maps of the specimen in the same field of view as the fluorescence channel. Using pairs of phase and fluorescence images, we trained a convolution neural network to translate the former into the latter. The training to infer a new tag is very practical as the input and ground truth data are intrinsically registered, and the data acquisition is automated. The ACM images present significantly stronger depth sectioning than the input (phase) images, enabling us to recover confocal-like tomographic volumes of microspheres, hippocampal neurons in culture, and 3D liver cancer spheroids. By training on nucleus-specific tags, ACM allows for segmenting individual nuclei within dense spheroids for both cell counting and volume measurements. In summary, ACM can provide quantitative, dynamic data, nondestructively from thick samples, while chemical specificity is recovered computationally.

Celastrol acts as a new histone deacetylase inhibitor to inhibit colorectal cancer cell growth via regulating macrophage polarity.

The tumorigenesis and progression of colorectal cancer are closely related to the tumor microenvironment, especially inflammatory response. Inhibitors of histone deacetylase (HDAC) have been reported as epigenetic regulators of the immune system to treat cancer and inflammatory diseases and our results demonstrated that Celastrol could act as a new HDAC inhibitor. Considering macrophages as important members of the tumor microenvironment, we further found that Celastrol could influence the polarization of macrophages to inhibit colorectal cancer cell growth. Specially, we used the supernatant of HCT116 and SW480 cells to induce Ana-1 cells in vitro and chose the spontaneous colorectal cancer model APCmin/+ mice as an animal model to validate in vivo. The results indicated that Celastrol could reverse the polarization of macrophages from M2 to M1 through impacting the colorectal tumor microenvironment both in vitro and in vivo. Furthermore, using bioinformatics analysis, we found that Celastrol might mechanistically polarize the macrophages through MAPK signaling pathway. In conclusion, our findings identified that Celastrol as a new HDAC inhibitor and suggested that Celastrol could modulate macrophage polarization, thus inhibiting colorectal cancer growth, which may provide some novel therapeutic strategies for colorectal cancer.

Live-dead assay on unlabeled cells using phase imaging with computational specificity.

Existing approaches to evaluate cell viability involve cell staining with chemical reagents. However, the step of exogenous staining makes these methods undesirable for rapid, nondestructive, and long-term investigation. Here, we present an instantaneous viability assessment of unlabeled cells using phase imaging with computation specificity. This concept utilizes deep learning techniques to compute viability markers associated with the specimen measured by label-free quantitative phase imaging. Demonstrated on different live cell cultures, the proposed method reports approximately 95% accuracy in identifying live and dead cells. The evolution of the cell dry mass and nucleus area for the labeled and unlabeled populations reveal that the chemical reagents decrease viability. The nondestructive approach presented here may find a broad range of applications, from monitoring the production of biopharmaceuticals to assessing the effectiveness of cancer treatments.

EGFR-IL-6 Signaling Axis Mediated the Inhibitory Effect of Methylseleninic Acid on Esophageal Squamous Cell Carcinoma.

Epidemiological and experimental evidence indicate that selenium is associated with a reduced risk of some cancers, including esophageal cancer. However, the exact mechanism is still unclear. In the present study, we used esophageal squamous cell carcinoma (ESCC) cell lines and animal models to explore the anti-cancer mechanism of methylseleninic acid (MSA). Firstly, MSA treatment dramatically attenuated Epidermal Growth Factor Receptor (EGFR) protein expression but did not alter mRNA levels in ESCC cells. On the contrary, EGFR overexpression partly abolished the inhibitory effect of MSA. With a microRNA-array, we found MSA up-regulated miR-146a which directly targeted EGFR, whereas miR-146a inhibitor antagonized MSA-induced decrease of EGFR protein. We further used 4-nitroquinoline-1-oxide (4NQO)-induced esophageal tumor mice model to evaluate the inhibitory effect of MSA in vivo. MSA treatment significantly decreased the tumor burden and EGFR protein expression in tumor specimens. Furthermore, MSA treatment inhibited EGFR pathway and subsequntly reduced Interleukin-6 (IL-6) secretion in the supernatant of cancer cell lines. MSA-induced IL-6 suppression was EGFR-dependent. To further evaluate the association of IL-6 and the anti-tumor effect of MSA on esophageal cancer, we established the 4NQO-induced esophageal tumor model in IL-6 knock-out (IL-6 KO) mice. The results showed that IL-6 deficiency did not affect esophageal tumorigenesis in mice, but the inhibitory effect of MSA was abolished in IL-6 KO mice. In conclusion, our study demonstrated that MSA upregulated miR-146a which directly targeted EGFR, and inhibited EGFR protein expression and pathway activity, subsequently decreased IL-6 secretion. The inhibitory effect of MSA on esophageal cancer was IL-6 dependent. These results suggested that MSA may serve as a potential drug treating esophageal cancer.

Harmonic optical tomography of nonlinear structures.

Second-harmonic generation microscopy is a valuable label-free modality for imaging non-centrosymmetric structures and has important biomedical applications from live-cell imaging to cancer diagnosis. Conventional second-harmonic generation microscopy measures intensity signals that originate from tightly focused laser beams, preventing researchers from solving the scattering inverse problem for second-order nonlinear materials. Here, we present harmonic optical tomography (HOT) as a novel modality for imaging microscopic, nonlinear and inhomogeneous objects. The HOT principle of operation relies on inter-ferometrically measuring the complex harmonic field and using a scattering inverse model to reconstruct the three-dimensional distribution of harmonophores. HOT enables strong axial sectioning via the momentum conservation of spatially and temporally broadband fields. We illustrate the HOT operation with experiments and reconstructions on a beta-barium borate crystal and various biological specimens. Although our results involve second-order nonlinear materials, we show that this approach applies to any coherent nonlinear process.

Epi-illumination gradient light interference microscopy for imaging opaque structures.

Multiple scattering and absorption limit the depth at which biological tissues can be imaged with light. In thick unlabeled specimens, multiple scattering randomizes the phase of the field and absorption attenuates light that travels long optical paths. These obstacles limit the performance of transmission imaging. To mitigate these challenges, we developed an epi-illumination gradient light interference microscope (epi-GLIM) as a label-free phase imaging modality applicable to bulk or opaque samples. Epi-GLIM enables studying turbid structures that are hundreds of microns thick and otherwise opaque to transmitted light. We demonstrate this approach with a variety of man-made and biological samples that are incompatible with imaging in a transmission geometry: semiconductors wafers, specimens on opaque and birefringent substrates, cells in microplates, and bulk tissues. We demonstrate that the epi-GLIM data can be used to solve the inverse scattering problem and reconstruct the tomography of single cells and model organisms.

LKB1 and YAP phosphorylation play important roles in Celastrol-induced ß-catenin degradation in colorectal cancer.

Wnt/ß-catenin and Hippo pathways play essential roles in the tumorigenesis and development of colorectal cancer. We found that Celastrol, isolated from Tripterygium wilfordii plant, exerted a significant inhibitory effect on colorectal cancer cell growth in vitro and in vivo, and further unraveled the molecular mechanisms. Celastrol induced ß-catenin degradation through phosphorylation of Yes-associated protein (YAP), a major downstream effector of Hippo pathway, and also Celastrol-induced ß-catenin degradation was dependent on liver kinase B1 (LKB1). Celastrol increased the transcriptional activation of LKB1, partially through the heat shock factor 1 (HSF1). Moreover, LKB1 activated AMP-activated protein kinase α (AMPKα) and further phosphorylated YAP, which eventually promoted the degradation of ß-catenin. In addition, LKB1 deficiency promoted colorectal cancer cell growth and attenuated the inhibitory effect of Celastrol on colorectal cancer growth both in vitro and in vivo. Taken together, Celastrol inhibited colorectal cancer cell growth by promoting ß-catenin degradation via the HSF1-LKB1-AMPKα-YAP pathway. These results suggested that Celastrol may potentially serve as a future drug for colorectal cancer treatment.

Optical excitation and detection of neuronal activity.

Optogenetics has emerged as an exciting tool for manipulating neural activity, which in turn, can modulate behavior in live organisms. However, detecting the response to the optical stimulation requires electrophysiology with physical contact or fluorescent imaging at target locations, which is often limited by photobleaching and phototoxicity. In this paper, we show that phase imaging can report the intracellular transport induced by optogenetic stimulation. We developed a multimodal instrument that can both stimulate cells with subcellular spatial resolution and detect optical pathlength (OPL) changes with nanometer scale sensitivity. We found that OPL fluctuations following stimulation are consistent with active organelle transport. Furthermore, the results indicate a broadening in the transport velocity distribution, which is significantly higher in stimulated cells compared to optogenetically inactive cells. It is likely that this label-free, contactless measurement of optogenetic response will provide an enabling approach to neuroscience.

IL-6 influences the polarization of macrophages and the formation and growth of colorectal tumor.

Macrophages play a crucial role in tumorigenesis depending upon the phenotype of macrophages found in tumor microenvironments. To date, how the tumor microenvironment affects the phenotypes of macrophages is not yet fully understood. In this study, we constructed a NIH3T3/Src cell line stably overexpresses the Src protein and found that conditioned medium from this cell line was able to induce polarization towards the M2 phenotype in primary bone marrow-derived macrophages (BMDM) and Ana-1 macrophages. Further investigation revealed that IL-6 produced by NIH3T3/Src cells plays a key role in M2 polarization. During the development of colorectal cancer in C57BL/6J-ApcMin/+ mice, increased IL-6 secretion in the interstitial fluid of the colorectal tissues was observed. Furthermore, tumorigenesis in IL-6tm1Kopf mice treated with AOM-DSS, an IL-6 knockout mouse strain, was significantly inhibited compared with the control group, suggesting the important role of IL-6 in promoting tumorigenicity. Our findings identify the target molecules and proinflammatory cytokines responsible for promoting polarization towards the M2 phenotype in macrophages present in tumor microenvironment, which may be useful for the design of novel therapeutic strategies for colorectal cancer.

Overexpression of KLF4 promotes cell senescence through microRNA-203-survivin-p21 pathway.

Krüppel-like factor 4 (KLF4) is a transcription factor and functions as a tumor suppressor or tumor promoter in different cancer types. KLF4 regulates many gene expression, thus affects the process of cell proliferation, differentiation, and apoptosis. Recently, KLF4 was reported to induce senescence during the generation of induced pluripotent stem (iPS) cells, but the exact mechanism is still unclear. In this study, we constructed two doxycycline-inducing KLF4 cell models, and demonstrated overexpression of KLF4 could promote cell senescence, detected by senescence-associated ß-galactosidase activity assay. Then we confirmed that p21, a key effector of senescence, was directly induced by KLF4. KLF4 could also inhibit survivin, which could indirectly induce p21. By miRNA microarray, we found a series of miRNAs regulated by KLF4 and involved in senescence. We demonstrated that KLF4 could upregulate miR-203, and miR-203 contributed to senescence through miR-203-survivin-p21 pathway. Our results suggest that KLF4 could promote cell senescence through a complex network: miR-203, survivin, and p21, which were all regulated by overexpression of KLF4 and contributed to cell senescence.

Methylseleninic acid activates Keap1/Nrf2 pathway via up-regulating miR-200a in human oesophageal squamous cell carcinoma cells.

Oesophageal squamous cell carcinoma (ESCC) occurs at a very high rates in certain regions of China. There are increasing evidences demonstrating that selenium could act as a potential anti-oesophageal cancer agent, but the precise mechanisms involved are still not completely understood. Methylseleninic acid (MSA), as a potent second-generation selenium compound, is a promising chemopreventive agent. Previous studies demonstrated that the kelch-like ECH-associated protein 1 (Keap1)/nuclear factor E2-related factor 2 (Nrf2) system plays a critical role in cancer prevention, but little is known about its association with MSA in ESCC cells. In the present study, we observed that MSA treatment significantly down-regulated Keap1, induced nuclear accumulation of Nrf2 and enhance the antioxidant response element (ARE) promoter activity in ESCC cells. MSA could also significantly induce miR-200a expression and inhibit Keap1 directly. Antagomir-200a could attenuate MSA treatment-induced Keap1 down-regulation in ESCC cells. Moreover, MSA-induced miR-200a expression was dependent on the mediation of Krüpple-like factor 4 (KLF4). These results reaffirm the potential role of MSA as a chemopreventive agent via the regulation of KLF4/miR-200a/Keap1/Nrf2 axis in ESCC cells.

Upregulation of KLF4 by methylseleninic acid in human esophageal squamous cell carcinoma cells: Modification of histone H3 acetylation through HAT/HDAC interplay.

Esophageal squamous cell carcinoma (ESCC) occurs at a very high frequency in certain areas of China. Supplementation with selenium-containing compounds was associated with a significantly lower cancer mortality rate in a study conducted in Linxia, China. Thus, selenium could be a potential anti-esophageal cancer agent. In this study, methylseleninic acid (MSA) could inhibit cell growth of ESCC cells in vitro and in vivo. Upon treated with MSA, the activity of histone deacetylases (HDACs) was decreased and general control nonrepressed protein 5 (GCN5) was upregulated in ESCC cells. Meanwhile, a significant increase of H3K9 acetylation (H3K9ac) was detected. Upregulation of Krüppel-like factor 4 (KLF4) was also observed after MSA treatment. Additionally, the acetylated histone H3 located more at KLF4 promoter region after MSA treatment, shown by chromatin immunoprecipitation (ChIP) assay. Moreover, knockdown of GCN5 decreased the protein level of both H3K9ac and KLF4, along with less cell growth inhibition. Taken all, our results indicated that MSA could inhibit ESCC cell growth, at least in part, by MSA-HDAC/GCN5-H3K9ac-KLF4 axis. To our best knowledge, this is the first report that MSA induced acetylation of histone H3 at Lys9, which might depend on the activities and the balance between HDACs and HATs.

P21-activated kinase 7 mediates cisplatin-resistance of esophageal squamous carcinoma cells with Aurora-A overexpression.

Aurora-A overexpression is common in various types of cancers and has been shown to be involved in tumorigenesis through different signaling pathways, yet how the deregulation affects cancer therapeutics remains elusive. Here we showed that overexpression of Aurora-A rendered esophageal cancer cells resistance to cisplatin (CDDP) by inhibiting apoptosis. By using an apoptosis array, we identified a downstream gene, p21-activated kinase 7 (PAK7). PAK7 was upregulated by Aurora-A overexpression at both mRNA and protein levels. Importantly, the expression levels of Aurora-A and PAK7 were correlated in ESCC primary samples. Chromatin immunoprecipitation (ChIP) assay revealed that binding of E2F1 to the promoter of PAK7 was significantly enhanced upon Aurora-A activation, and knockdown of transcription factor E2F1 decreased PAK7 expression, suggesting that Aurora-A regulated PAK7 through E2F1. Furthermore, we demonstrated that PAK7 knockdown led to increased apoptosis, and Aurora-A-induced resistance to CDDP was reversed by downregulation of PAK7, suggesting PAK7 was a downstream player of Aurora-A that mediated chemoresistance of ESCC cells to CDDP. Our data suggest that PAK7 may serve as an attractive candidate for therapeutics in ESCC patients with Aurora-A abnormality.

MicroRNA-mRNA functional pairs for cisplatin resistance in ovarian cancer cells.

Ovarian cancer is the leading cause of death in women worldwide. Cisplatin is the core of first-line chemotherapy for patients with advanced ovarian cancer. Many patients eventually become resistant to cisplatin, diminishing its therapeutic effect. MicroRNAs (miRNAs) have critical functions in diverse biological processes. Using miRNA profiling and polymerase chain reaction validation, we identified a panel of differentially expressed miRNAs and their potential targets in cisplatin-resistant SKOV3/DDP ovarian cancer cells relative to cisplatin-sensitive SKOV3 parental cells. More specifically, our results revealed significant changes in the expression of 13 of 663 miRNAs analyzed, including 11 that were up-regulated and 2 that were down-regulated in SKOV3/DDP cells with or without cisplatin treatment compared with SKOV3 cells with or without cisplatin treatment. miRNA array and mRNA array data were further analyzed using Ingenuity Pathway Analysis software. Bioinformatics analysis suggests that the genes ANKRD17, SMC1A, SUMO1, GTF2H1, and TP73, which are involved in DNA damage signaling pathways, are potential targets of miRNAs in promoting cisplatin resistance. This study highlights candidate miRNA-mRNA interactions that may contribute to cisplatin resistance in ovarian cancer.

miR-106a is frequently upregulated in gastric cancer and inhibits the extrinsic apoptotic pathway by targeting FAS.

Emerging evidence has shown the association of aberrantly expressed miR-106a with cancer development, however, little is known about its potential role in gastric carcinogenesis. In our present study, obviously overexpressed miR-106a was found in gastric cancer tissues compared with their nontumor counterparts. Suppression of miR-106a significantly inhibited gastric cancer cell proliferation and triggered apoptosis. Bioinformatic analysis combining with validation experiments identified FAS as a direct target of miR-106a. Rescue experiments and examination of caspase-8, PARP and caspase-3 further approved that miR-106a could inhibit gastric cancer cell apoptosis through interfering with FAS-mediated apoptotic pathway. Moreover, a significant inverse correlation was found between miR-106a and FAS expression not only in gastric cancer cell lines but also in gastric cancer specimens. Taken together, these findings suggest that ectopicly overexpressed miR-106a may play an oncogenic role in gastric carcinogenesis and impair extrinsic apoptotic pathway through targeting FAS.

Overexpression of the DEC1 protein induces senescence in vitro and is related to better survival in esophageal squamous cell carcinoma.

Esophageal squamous cell carcinoma (ESCC) is a leading cause of cancer-related death in China and has limited effective therapeutic options except for early surgery, since the underlying molecular mechanism driving its precursor lesions towards invasive ESCC is not fully understood. Cellular senescence is the state of the permanent growth arrest of a cell, and is considered as the initial barrier of tumor development. Human differentiated embryo chondrocyte expressed gene 1 (Dec1) is an important transcription factor that related to senescence. In this study, DEC1 immunohistochemical analysis was performed on tissue microarray blocks constructed from ESCC combined with adjacent precursor tissues of 241 patients. Compared with normal epithelia, DEC1 expression was significantly increased in intraepithelial neoplasia and DEC1 expression was significantly decreased in ESCC in comparison with intraepithelial neoplasia. In vitro, DEC1 overexpression induced cellular senescence, and it inhibited cell growth and colony formation in ESCC cell line EC9706. Fresh esophagectomy tissue sections from five ESCC patients were detected by immunohistochemistry of DEC1 and senescence-associated ß-galactosidase (SA-ß-Gal) activity, and strongly positive expression of DEC1 was correlated to more senescent cells in these fresh tissue sections. Kaplan-Meier method analysis of the 241 patients revealed that DEC1 expression levels were significantly correlated with the survival of ESCC patients after surgery. The expression levels of DEC1 were also correlated with age, tumor embolus, depth of invasion of ESCC, lymph metastasis status and pTNMs. These results suggest that DEC1 overexpression in precursor lesions of ESCC is a protective mechanism by inducing cellular senescence in ESCC initiation, and DEC1 may be a potential prognostic marker of ESCC.

High expression of survivin predicts poor prognosis in esophageal squamous cell carcinoma following radiotherapy.

Radiotherapy is one of the main treatments for esophageal squamous cell carcinoma, but there are still no biomarkers to differentiate patients who will benefit from radiation. Although treatment with a combination of radiotherapy with chemotherapy, and/or surgery improves the prognosis of patients, no biomarkers can distinguish between the responses obtained with the combined therapies. Therefore, in this study, we selected patients treated with radiotherapy alone to evaluate survivin as a predictor for radiotherapy. One hundred two biopsy samples collected by endoscopy were immunostained by survivin antibody. Positive staining for survivin was obtained in 60.8% tumor samples. Survivin expression, metastasis, and clinical stage correlated significantly with overall survival. In multivariate analysis, survivin was an independent prognostic factor for predicting overall survival of patients with esophageal cancer. Moreover, in esophageal cancer cell lines, overexpression of survivin reduced the percentage of cell death induced by radiation. Our data indicate that survivin could be a potential predictor to define those patients with esophageal squamous carcinoma who would benefit from radiotherapy.

TNF-α is a novel target of miR-19a.

Many studies have demonstrated the overexpression and amplification of the miR-17-92 cluster in malignant human cancers, including B-cell lymphomas and lung cancers. The purpose of this study was to investigate for the first time, the expression of the miR-17-92 cluster in esophageal squamous cell carcinoma (ESCC). The miR-17-92 cluster was found to be overexpressed in 21 out of 28 (75%) esophageal cancer samples. It was also found that overexpression of the miR-17-92 cluster could promote cellular growth in vivo and in vitro. Furthermore, inhibition of miR-19a by antisense oligonucleotides (ONs) induced apoptosis, while antisense ONs against miR-17-5p, miR-18a, miR-20a and miR-92-1 did not exhibit such an effect. In addition, it was found that antagomir-19a treatment could impair tumor growth in vivo. Using Human Apoptosis RT2 Profiler PCR Array 384HT, we found that tumor necrosis factor-α (TNF-α) was up-regulated 12-fold in cells transfected with miR-19a antisense ONs compared to the cells treated with the control scramble ONs. MiR-19a was predicted to target the 3' untranslated region of TNF-α mRNA, and this was confirmed by luciferase reporter assay. Taken together, we conclude that the miR-17-92 cluster is overexpressed in ESCC and that TNF-α is a novel target of miR-19a.

Suppression of p21 by c-Myc through members of miR-17 family at the post-transcriptional level.

The miR-17 family, composed of miR-17-5p, miR-20a/b, miR-106a/b and miR-93, has been demonstrated to take part in critical pathways that regulate cellular life and death decisions during normal development and in malignancy. Previous studies have shown that the expression of miR-17 family members has close relationship with the expression of c-Myc. Another study has reported p21 is a direct target of miR-17 family and their silencing of p21 contributes to tumor cell proliferation in part. Since c-Myc is a potent transcriptional repressor of p21, these findings suggest that c-Myc may negatively modulate p21 expression through an additional pathway except transcriptional suppression. In the study presented here, we compared p21 mRNA in the nucleus and cytoplasm of c-Myc stable transfectants with its control, which indicated further repression of p21 by c-Myc at the post-transcriptional level. Stem-loop and conventional real-time PCR showed elevated expression of some members in miR-17 family and their primary transcripts when c-Myc was stably overexpressed. To further investigate the relationship of c-Myc, miR-17 family and p21, we antagonized the expression of each miR-17 family member by transfection of their antisense oligonucleotides respectively in transfectants constitutively overexpressing c-Myc or not, and found that the restoration of p21 expression by treatment above was much stronger in the presence of c-Myc. These results suggest c-Myc could further repress p21 expression at the post-transcriptional level through some, but not all, members of miR-17 family.