Immediate intraoperative sentinel lymph node analysis by frozen section is predictive of lymph node metastasis in endometrial cancer.
Journal of robotic surgery
How to Quantify the Fraction of Photoactivated Fluorescent Proteins in Bulk and in Live Cells.
Journal of visualized experiments : JoVE
Sentinel lymph nodes sampling (SLN) in endometrial cancer is being evaluated as a means to gather prognostic information about lymphatic metastasis while avoiding the morbidity associated with complete lymphadenectomy. SLN ultrastaging has been advocated to identify low-volume metastases, but its value remains uncertain. This study aims to evaluate a pathological protocol for the immediate intraoperative SLN work-up using H&E staining alone. In this retrospective single-center study, patients received standardized cervical injection of indocyanine green, SLN mapping followed by pelvic lymphadenectomy with or without para-aortic lymphadenectomy. SLNs were entirely frozen, multiple H&E stained sections prepared and evaluated intraoperatively. No immunohistochemistry was performed. SLN results were compared with the complete lymphadenectomy specimen. Over 3.5 years, 90 patients were identified who underwent SLN mapping and subsequent complete pelvic lymphadenectomy. At least one SLN was detected in 79 (88%) patients. The median number of SLNs removed was 2.0. Para-aortic SLNs were detected in 7%. Final pathology showed 67% Type I tumors, 76% locally confined. The mean number of lymph nodes removed during complete lymphadenectomy was 21. In this series, only 6 patients had lymph node metastases. 5/6 were identified by the described SLN approach resulting in 83.3% sensitivity and a negative predictive value of 98.7%. Our approach permits immediate intraoperative results and helps guide the primary surgery. The immediate SLN work-up using frozen sections showed both high accuracy and negative predictive value. The comparably lower sensitivity may be related to the low number of patients with positive lymph nodes (7.6%).
View details for PubMedID 30687881
Sentinel lymph node biopsies in endometrial cancer - practice patterns among Gynecologic Oncologists in the United States.
Journal of minimally invasive gynecology
Photoactivatable and -convertible fluorescent proteins (PA-FPs) have been used in fluorescence live-cell microscopy for analyzing the dynamics of cells and protein ensembles. Thus far, no method has been available to quantify in bulk and in live cells how many of the PA-FPs expressed are photoactivated to fluoresce. Here, we present a protocol involving internal rulers, i.e., genetically coupled spectrally distinct (photoactivatable) fluorescent proteins, to ratiometrically quantify the fraction of all PA-FPs expressed in a cell that are switched on to be fluorescent. Using this protocol, we show that different modes of photoactivation yielded different photoactivation efficiencies. Short high-power photoactivation with a confocal laser scanning microscope (CLSM) resulted in up to four times lower photoactivation efficiency than hundreds of low-level exposures applied by CLSM or a short pulse applied by widefield illumination. While the protocol has been exemplified here for (PA-)GFP and (PA-)Cherry, it can in principle be applied to any spectrally distinct photoactivatable or photoconvertible fluorescent protein pair and any experimental set-up.
View details for PubMedID 30663670
Cytoplasmic self-organization established by internal lipid membranes in the interplay with either actin or microtubules
Robotic Olympics: A novel robotic surgical training experience for residents in an obstetrics and gynecology residency program
Internal rulers to assess fluorescent protein photoactivation efficiency.
Cytometry. Part A : the journal of the International Society for Analytical Cytology
To evaluate practice patterns among gynecologic oncologists with regards to sentinel lymph node injection and biopsy in endometrial cancer.Observational study with no control group.Active members of the Society of Gynecologic Oncology.After IRB approval, we performed an online survey amongst active members of the Society of Gynecologic Oncology. Members were contacted via email and their answers anonymously captured. Study data were collected using REDCap.318 of 1216 listed members completed the online survey, The majority of respondents (82.7%) perform sentinel lymph node sampling for endometrial cancer staging. Most technical aspects of sentinel lymph node sampling were consistently applied by the vast majority of respondents, including the choice of indocyanine green (ICG) as lymphatic tracer (97.3%) and its injection into the cervix (100%). Other technical aspects of sentinel lymph node sampling, such as the depth of injection, varied amongst respondents. While 50.9% of the respondents perform an intraoperative assessment of the uterus by frozen section, only 17.9% assess sentinel lymph nodes by frozen section and/or touch prep. Some of the respondents' approaches are based on limited data, including (i) the use of sentinel lymph node injection and biopsy for high-risk histologies (performed by 69 - 75% of the respondents dependent upon the histology), (ii) omitting side-specific completion lymphadenectomy in the absence of sentinel node mapping (in up to 57.8%) or (iii) when lymph node metastases are present (in 39.9%).In summary, despite the growing use of sentinel lymph node injection and biopsy in endometrial cancer, practice patterns vary considerably among providers sampled by this survey. Some of the decisions are based on limited evidence and, in some instances, deviate from current published guidelines.
View details for PubMedID 30980995
Simultaneous Endometrial Aspiration and Sonohysterography for the Evaluation of Endometrial Pathology in Women Aged 50 Years and Older
OBSTETRICS AND GYNECOLOGY
2015; 125 (2): 414-423
Photoactivatable fluorescent proteins (PA-FPs) have been widely used to assess the dynamics of cell biological processes. In addition, PA-FPs enabled single-molecule based super-resolution imaging (photoactivated localization microscopy) and thereby provided unprecedented structural insight. For the lack of tools, however, the fraction of PA-FPs that is, actually being switched on to fluoresce, that is, the photoactivation efficiency, has been difficult to assess. Uncertainty about photoactivation efficiency has hampered an understanding of the absolute amount of PA-FPs, that is, being examined. Here, we present internal rulers to assess photoactivation efficiencies of photoactivatable proteins. These internal rulers comprise a PA-FP that is genetically directly coupled to a spectrally distinct always-on fluorescent protein. Thus, these fluorescent proteins will be expressed in the bacterial and mammalian cell in a one-to-one ratio. With these tools, we describe photoactivation efficiencies of PA-GFP and PA-Cherry in intensity-based ratiometric ensemble studies and on the single-molecule level. In ratiometric ensemble studies, we show that photoactivation efficiency depends on how the PA-FPs are exposed to 405 nm light. Using a laser-scanning microscope, hundreds of iterative low-level exposures are up to four times more efficient than a short high-power exposure. Using wide-field illumination, photoactivation was similarly efficient and instantaneous. These findings suggest that the repetitive or stochastic exposure to photons of 405 nm light results in more efficient photoactivation than a continuous flow of photons. Because of the differential photoactivation efficiency, it is crucial to assess photoactivation efficiency for any given experimental set-up. The tools we provide can be applied to any genetically encoded photoactivatable protein. Determination of photoactivation efficiency is essential for an understanding of absolute molecule numbers in ensemble studies and, most importantly, quantitative superresolution imaging. © 2017 International Society for Advancement of Cytometry.
View details for PubMedID 29286574
Probing the Stochastic, Motor-Driven Properties of the Cytoplasm Using Force Spectrum Microscopy
2014; 158 (4): 822-832
To evaluate the performance of simultaneous endometrial aspiration at the time of sonohysterography for screening postmenopausal women at risk for endometrial cancer.A retrospective cohort study of women older than 50 years who underwent saline-infusion sonohysterography for the evaluation of their endometrium. On completion of imaging, the remaining intracavitary saline and endometrial tissue were aspirated through the saline-infusion sonohysterography catheter and submitted for pathologic evaluation. Based on the clinical, pathologic, and ultrasonographic results, the patients underwent surgical treatment with hysteroscopy, hysterectomy, or clinical observation. Follow-up results and outcomes were collected using electronic medical records. Sensitivity, specificity, and predictive values of saline-infusion sonohysterography, endometrial aspiration, and combined approaches for endometrial aspiration and sonohysterography were assessed.Six hundred three patients underwent endometrial aspiration at the time of sonohysterography. Endometrial tissue was present in 567 (94.0%) and outcome data were available for 540 (89.5%). In 194 (35.9%) patients, final pathology was obtained by surgical intervention. The remaining 346 (64.1%) patients were monitored for at least 6 months. Thirty patients (5.6%) had cancer or endometrial hyperplasia. A sequential model, in which endometrial aspiration was done only for positive saline-infusion sonohysterography findings, yielded sensitivity of 86.7% (95% confidence interval [CI] 69-96%) and specificity of 100% (95% CI 99-100%) for detecting endometrial hyperplasia or cancer (area under the curve 0.93). Considering proliferative endometrium as abnormal endometrial aspiration reduced specificity to 88.3% (95% CI 85-91%, P<.01) without significant increase in sensitivity (100%, 95% CI 88-100%, P=.13).The high sensitivity and specificity of the sequential endometrial aspiration at the time of sonohysterography make this approach a useful and reliable screening algorithm for detecting endometrial cancer or hyperplasia in postmenopausal women at risk. Endometrial aspiration at the time of sonohysterography should be considered as an initial one-stop endometrial evaluation in this population.
View details for DOI 10.1097/AOG.0000000000000631
View details for Web of Science ID 000348595500021
View details for PubMedID 25568988
Fluorescence microscopy-A historical and technical perspective
CYTOMETRY PART A
2013; 83 (9): 767-779
Molecular motors in cells typically produce highly directed motion; however, the aggregate, incoherent effect of all active processes also creates randomly fluctuating forces, which drive diffusive-like, nonthermal motion. Here, we introduce force-spectrum-microscopy (FSM) to directly quantify random forces within the cytoplasm of cells and thereby probe stochastic motor activity. This technique combines measurements of the random motion of probe particles with independent micromechanical measurements of the cytoplasm to quantify the spectrum of force fluctuations. Using FSM, we show that force fluctuations substantially enhance intracellular movement of small and large components. The fluctuations are three times larger in malignant cells than in their benign counterparts. We further demonstrate that vimentin acts globally to anchor organelles against randomly fluctuating forces in the cytoplasm, with no effect on their magnitude. Thus, FSM has broad applications for understanding the cytoplasm and its intracellular processes in relation to cell physiology in healthy and diseased states.
View details for DOI 10.1016/j.cell.2014.06.051
View details for Web of Science ID 000340944700013
View details for PubMedID 25126787
Plasticity of the asialoglycoprotein receptor deciphered by ensemble FRET imaging and single-molecule counting PALM imaging
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2012; 109 (44): E2989-E2997
For a little more than a century, fluorescence microscopy has been an essential source of major discoveries in cell biology. Recent developments improved both visualization and quantification by fluorescence microscopy imaging and established a methodology of fluorescence microscopy. By outlining basic principles and their historical development, I seek to provide insight into and understanding of the ever-growing tools of fluorescence microscopy. Thereby, this synopsis may help the interested researcher to choose a fluorescence microscopic method capable of addressing a specific scientific question.
View details for DOI 10.1002/cyto.a.22295
View details for Web of Science ID 000323480200003
View details for PubMedID 23585290
Multiscale diffusion in the mitotic Drosophila melanogaster syncytial blastoderm
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2012; 109 (22): 8588-8593
The stoichiometry and composition of membrane protein receptors are critical to their function. However, the inability to assess receptor subunit stoichiometry in situ has hampered efforts to relate receptor structures to functional states. Here, we address this problem for the asialoglycoprotein receptor using ensemble FRET imaging, analytical modeling, and single-molecule counting with photoactivated localization microscopy (PALM). We show that the two subunits of asialoglycoprotein receptor [rat hepatic lectin 1 (RHL1) and RHL2] can assemble into both homo- and hetero-oligomeric complexes, displaying three forms with distinct ligand specificities that coexist on the plasma membrane: higher-order homo-oligomers of RHL1, higher-order hetero-oligomers of RHL1 and RHL2 with two-to-one stoichiometry, and the homo-dimer RHL2 with little tendency to further homo-oligomerize. Levels of these complexes can be modulated in the plasma membrane by exogenous ligands. Thus, even a simple two-subunit receptor can exhibit remarkable plasticity in structure, and consequently function, underscoring the importance of deciphering oligomerization in single cells at the single-molecule level.
View details for DOI 10.1073/pnas.1211753109
View details for Web of Science ID 000311149900008
View details for PubMedID 23043115
Probing protein heterogeneity in the plasma membrane using PALM and pair correlation analysis
2011; 8 (11): 969-975
Despite the fundamental importance of diffusion for embryonic morphogen gradient formation in the early Drosophila melanogaster embryo, there remains controversy regarding both the extent and the rate of diffusion of well-characterized morphogens. Furthermore, the recent observation of diffusional "compartmentalization" has suggested that diffusion may in fact be nonideal and mediated by an as-yet-unidentified mechanism. Here, we characterize the effects of the geometry of the early syncytial Drosophila embryo on the effective diffusivity of cytoplasmic proteins. Our results demonstrate that the presence of transient mitotic membrane furrows results in a multiscale diffusion effect that has a significant impact on effective diffusion rates across the embryo. Using a combination of live-cell experiments and computational modeling, we characterize these effects and relate effective bulk diffusion rates to instantaneous diffusion coefficients throughout the syncytial blastoderm nuclear cycle phase of the early embryo. This multiscale effect may be related to the effect of interphase nuclei on effective diffusion, and thus we propose that an as-yet-unidentified role of syncytial membrane furrows is to temporally regulate bulk embryonic diffusion rates to balance the multiscale effect of interphase nuclei, which ultimately stabilizes the shapes of various morphogen gradients.
View details for DOI 10.1073/pnas.1204270109
View details for Web of Science ID 000304881700050
View details for PubMedID 22592793
Bright Monomeric Photoactivatable Red Fluorescent Protein for Two-Color Super-Resolution sptPALM of Live Cells
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2010; 132 (18): 6481-6491
Photoactivated localization microscopy (PALM) is a powerful approach for investigating protein organization, yet tools for quantitative, spatial analysis of PALM datasets are largely missing. Combining pair-correlation analysis with PALM (PC-PALM), we provide a method to analyze complex patterns of protein organization across the plasma membrane without determination of absolute protein numbers. The approach uses an algorithm to distinguish a single protein with multiple appearances from clusters of proteins. This enables quantification of different parameters of spatial organization, including the presence of protein clusters, their size, density and abundance in the plasma membrane. Using this method, we demonstrate distinct nanoscale organization of plasma-membrane proteins with different membrane anchoring and lipid partitioning characteristics in COS-7 cells, and show dramatic changes in glycosylphosphatidylinositol (GPI)-anchored protein arrangement under varying perturbations. PC-PALM is thus an effective tool with broad applicability for analysis of protein heterogeneity and function, adaptable to other single-molecule strategies.
View details for DOI 10.1038/NMETH.1704
View details for Web of Science ID 000296891800022
View details for PubMedID 21926998
Dynamics of the CapG actin-binding protein in the cell nucleus studied by FRAP and FCS
2008; 16 (3): 427-437
Rapidly emerging techniques of super-resolution single-molecule microscopy of living cells rely on the continued development of genetically encoded photoactivatable fluorescent proteins. On the basis of monomeric TagRFP, we have developed a photoactivatable TagRFP protein that is initially dark but becomes red fluorescent after violet light irradiation. Compared to other monomeric dark-to-red photoactivatable proteins including PAmCherry, PATagRFP has substantially higher molecular brightness, better pH stability, substantially less sensitivity to blue light, and better photostability in both ensemble and single-molecule modes. Spectroscopic analysis suggests that PATagRFP photoactivation is a two-step photochemical process involving sequential one-photon absorbance by two distinct chromophore forms. True monomeric behavior, absence of green fluorescence, and single-molecule performance in live cells make PATagRFP an excellent protein tag for two-color imaging techniques, including conventional diffraction-limited photoactivation microscopy, super-resolution photoactivated localization microscopy (PALM), and single particle tracking PALM (sptPALM) of living cells. Two-color sptPALM imaging was demonstrated using several PATagRFP tagged transmembrane proteins together with PAGFP-tagged clathrin light chain. Analysis of the resulting sptPALM images revealed that single-molecule transmembrane proteins, which are internalized into a cell via endocytosis, colocalize in space and time with plasma membrane domains enriched in clathrin light-chain molecules.
View details for DOI 10.1021/ja100906g
View details for Web of Science ID 000277445400039
View details for PubMedID 20394363
Invasive breast cancer cells exhibit increased mobility of the actin-binding protein CapG
INTERNATIONAL JOURNAL OF CANCER
2008; 122 (7): 1476-1482
FRAP (fluorescence recovery after photobleaching) and FCS (fluorescence correlation spectroscopy) are spectroscopic methods for monitoring the dynamic distribution of proteins inside the nucleus of living cells. As an example we report our studies on the intracellular mobility of the actin-binding protein CapG in live breast cancer cells. This Gelsolin-related protein is a putative oncogene. It appears to be overexpressed especially in metastasizing breast cancer. Furthermore, the CapG protein is known to be involved in the motility control of non-muscle benign cells. Its increased expression triggers an increase in cell motility of benign cells. Thus it can be expected that in cancer cells overexpressing the CapG protein, motility, invasiveness and metastasis might be particularly promoted. Since the nuclear CapG fraction seems to be pivotal to the increase in cell motility, we focused our studies on the CapG mobility in cell nuclei of live breast cancer cells. Using FCS and FRAP we showed that the eGFP-tagged CapG is monomeric and characterized its diffusional properties on the microsecond to minute timescale. This information about the mobility and compartmentalization of CapG might help to provide insight into its function within the cell nucleus and give clues about its altered cellular function in malignant dedifferentiation.
View details for DOI 10.1007/s10577-008-1234-6
View details for Web of Science ID 000255680800007
View details for PubMedID 18461482
The CapG protein, a Gelsolin-related actin-binding protein, is expressed at higher levels in breast cancer, especially in metastasizing breast cancer, than in normal breast epithelium. Furthermore, it is known that an increased expression of the CapG protein triggers an increase in cell motility. According to in vitro experiments, it was supposed that it is the nuclear fraction of the protein, which causes the increase in cell motility. Here, we examined the dynamical distribution of the CapG protein within the living cell, i.e. the import of the CapG protein into the nucleus. The nuclear import kinetics of invasive, metastasizing breast cancer cells were compared to the import kinetics of non-neoplastic cells similar to normal breast epithelium. FRAP kinetics showed a highly significant increase in the recovery of photobleached CapG-eGFP in the cancer cells, so that a differentiation of invasive, metastasizing cells and non-invasive, non-metastasizing cells on the basis of transport processes of the CapG protein between the nucleus and the cytoplasm seems to be possible. Comprehension of the mobility and compartmentalization of the CapG protein in normal and in cancer cells in vivo could constitute a new basis to characterize the invasiveness and metastasizing potential of breast cancer.
View details for DOI 10.1002/ijc.23215
View details for Web of Science ID 000253441100004
View details for PubMedID 18059028