Ki-67 acts as a biological surfactant to disperse mitotic chromosomes.

Eukaryotic genomes are partitioned into chromosomes that form compact and spatially well-separated mechanical bodies during mitosis. This enables chromosomes to move independently of each other for segregation of precisely one copy of the genome to each of the nascent daughter cells. Despite insights into the spatial organization of mitotic chromosomes and the discovery of proteins at the chromosome surface, the molecular and biophysical bases of mitotic chromosome structural individuality have remained unclear. Here we report that the proliferation marker protein Ki-67 (encoded by the MKI67 gene), a component of the mitotic chromosome periphery, prevents chromosomes from collapsing into a single chromatin mass after nuclear envelope disassembly, thus enabling independent chromosome motility and efficient interactions with the mitotic spindle. The chromosome separation function of human Ki-67 is not confined within a specific protein domain, but correlates with size and net charge of truncation mutants that apparently lack secondary structure. This suggests that Ki-67 forms a steric and electrostatic charge barrier, similar to surface-active agents (surfactants) that disperse particles or phase-separated liquid droplets in solvents. Fluorescence correlation spectroscopy showed a high surface density of Ki-67 and dual-colour labelling of both protein termini revealed an extended molecular conformation, indicating brush-like arrangements that are characteristic of polymeric surfactants. Our study thus elucidates a biomechanical role of the mitotic chromosome periphery in mammalian cells and suggests that natural proteins can function as surfactants in intracellular compartmentalization.

Design, Synthesis, and Anticancer Screening for Repurposed Pyrazolo[3,4-d]pyrimidine Derivatives on Four Mammalian Cancer Cell Lines.

The present study reports the synthesis of new purine bioisosteres comprising a pyrazolo[3,4-d]pyrimidine scaffold linked to mono-, di-, and trimethoxy benzylidene moieties through hydrazine linkages. First, in silico docking experiments of the synthesized compounds against Bax, Bcl-2, Caspase-3, Ki67, p21, and p53 were performed in a trial to rationalize the observed cytotoxic activity for the tested compounds. The anticancer activity of these compounds was evaluated in vitro against Caco-2, A549, HT1080, and Hela cell lines. Results revealed that two (5 and 7) of the three synthesized compounds (5, 6, and 7) showed high cytotoxic activity against all tested cell lines with IC50 values in the micro molar concentration. Our in vitro results show that there is no significant apoptotic effect for the treatment with the experimental compounds on the viability of cells against A549 cells. Ki67 expression was found to decrease significantly following the treatment of cells with the most promising candidate: drug 7. The overall results indicate that these pyrazolopyrimidine derivatives possess anticancer activity at varying doses. The suggested mechanism of action involves the inhibition of the proliferation of cancer cells.

Whole tumor section quantitative image analysis maximizes between-pathologists' reproducibility for clinical immunohistochemistry-based biomarkers.

Pathologists have had increasing responsibility for quantitating immunohistochemistry (IHC) biomarkers with the expectation of high between-reader reproducibility due to clinical decision-making especially for patient therapy. Digital imaging-based quantitation of IHC clinical slides offers a potential aid for improvement; however, its clinical adoption is limited potentially due to a conventional field-of-view annotation approach. In this study, we implemented a novel solely morphology-based whole tumor section annotation strategy to maximize image analysis quantitation results between readers. We first compare the field-of-view image analysis annotation approach to digital and manual-based modalities across multiple clinical studies (~120 cases per study) and biomarkers (ER, PR, HER2, Ki-67, and p53 IHC) and then compare a subset of the same cases (~40 cases each from the ER, PR, HER2, and Ki-67 studies) using whole tumor section annotation approach to understand incremental value of all modalities. Between-reader results for each biomarker in relation to conventional scoring modalities showed similar concordance as manual read: ER field-of-view image analysis: 95.3% (95% CI 92.0-98.2%) vs digital read: 92.0% (87.8-95.8%) vs manual read: 94.9% (91.4-97.8%); PR field-of-view image analysis: 94.1% (90.3-97.2%) vs digital read: 94.0% (90.2-97.1%) vs manual read: 94.4% (90.9-97.2%); Ki-67 field-of-view image analysis: 86.8% (82.1-91.4%) vs digital read: 76.6% (70.9-82.2%) vs manual read: 85.6% (80.4-90.4%); p53 field-of-view image analysis: 81.7% (76.4-86.8%) vs digital read: 80.6% (75.0-86.0%) vs manual read: 78.8% (72.2-83.3%); and HER2 field-of-view image analysis: 93.8% (90.0-97.2%) vs digital read: 91.0 (86.6-94.9%) vs manual read: 87.2% (82.1-91.9%). Subset implementation and analysis on the same cases using whole tumor section image analysis approach showed significant improvement between pathologists over field-of-view image analysis and manual read (HER2 100% (97-100%), P=0.013 field-of-view image analysis and 0.013 manual read; Ki-67 100% (96.9-100%), P=0.040 and 0.012; ER 98.3% (94.1-99.5%), p=0.232 and 0.181; and PR 96.6% (91.5-98.7%), p=0.012 and 0.257). Overall, whole tumor section image analysis significantly improves between-pathologist's reproducibility and is the optimal approach for clinical-based image analysis algorithms.

Light-Controlled Delivery of Monoclonal Antibodies for Targeted Photoinactivation of Ki-67.

The selective inhibition of intracellular and nuclear molecules such as Ki-67 holds great promise for the treatment of cancer and other diseases. However, the choice of the target protein and the intracellular delivery of the functional agent remain crucial challenges. Main hurdles are (a) an effective delivery into cells, (b) endosomal escape of the delivered agents, and (c) an effective, externally triggered destruction of cells. Here we show a light-controlled two-step approach for selective cellular delivery and cell elimination of proliferating cells. Three different cell-penetrating nano constructs, including liposomes, conjugates with the nuclear localization sequence (NLS), and conjugates with the cell penetrating peptide Pep-1, delivered the light activatable antibody conjugate TuBB-9-FITC, which targets the proliferation associated protein Ki-67. HeLa cells were treated with the photosensitizer benzoporphyrin monoacid derivative (BPD) and the antibody constructs. In the first optically controlled step, activation of BPD at 690 nm triggered a controlled endosomal escape of the TuBB-9-FITC constructs. In more than 75% of Ki-67 positive, irradiated cells TuBB-9-FITC antibodies relocated within 24 h from cytoplasmic organelles to the cell nucleus and bound to Ki-67. After a second light irradiation at 490 nm, which activated FITC, cell viability decreased to approximately 13%. Our study shows an effective targeting strategy, which uses light-controlled endosomal escape and the light inactivation of Ki-67 for cell elimination. The fact that liposomal or peptide-assisted delivery give similar results leads to the additional conclusion that an effective mechanism for endosomal escape leaves greater variability for the choice of the delivery agent.

Is there any relation between PET-CT SUVmax value and prognostic factors in locally advanced breast cancer?

PURPOSE: To investigate the relation between PET-CT SUVmax value and prognostic factors in locally advanced breast cancer. METHODS: Data of 73 patients were retrospectively analyzed. Relations between SUVmax value, clinical stage, tumor grade and breast cancer molecular subtypes were analyzed by using one-way ANOVA and x(2) tests. Correlations between age, ki-67 scores and SUVmax were evaluated by using Pearson's correlation test. A p value <0.05 was considered statistically significant. RESULTS: Median SUVmax values for clinical stages 1, 2 and 3 were 5 (range 2.1-4.1), 10.6 (range 2.9-19.6), and 12.2 (range 3.2-23.3), respectively. Statistically significant difference was noticed between stage 1 and 2 (p=0.014) and stage 1 and 3 (p=0.001). Median SUVmax values of triple negative, luminal A, luminal B and non-luminal HER2 positive groups were 14.4 (range 6.6-23.3), 8.2 (range 2.1-18.2), 10.1 (range 3.5-19.6), and 14 (range 4.1-22.9), respectively. Statistically significant differences were noticed in SUVmax values between triple-negative and luminal A groups (p=0.005) and between non-luminal HER2 positive and luminal A groups (p=0.02). Median SUVmax values of grade 1, 2 and 3 were 5.7 (range 2.1-18.2), 9.5 (range 2.2-21.3), and 11.6 (range 3.5-23), respectively. Statistically significant difference was noticed only between SUVmax values of grade 1 and 3 (p=0.035). There was negative correlation between age and SUVmax value (r=-0.23, p=0.047) and positive correlation between ki-67 and SUVmax value (r=0.43, p=0.016). CONCLUSION: There were significant positive relations between PET-CT SUVmax value and clinical stage, tumor grade, and certain breast cancer molecular subtypes (triple-negative and non-luminal HER2 positive groups. Moreover, positive correlation was found between SUVmax value and ki-67 and negative correlation between SUVmax value and age.

Perceptual clustering for automatic hotspot detection from Ki-67-stained neuroendocrine tumour images.

Hotspot detection plays a crucial role in grading of neuroendocrine tumours of the digestive system. Hotspots are often detected manually from Ki-67-stained images, a practice which is tedious, irreproducible and error prone. We report a new method to segment Ki-67-positive nuclei from Ki-67-stained slides of neuroendocrine tumours. The method combines minimal graph cuts along with the multistate difference of Gaussians to detect the individual cells from images of Ki-67-stained slides. It, then, automatically defines the composite function, which is used to determine hotspots in neuroendocrine tumour slide images. We combine modified particle swarm optimization with message passing clustering to mimic the thought process of the pathologist during hotspot detection in neuroendocrine tumour slide images. The proposed method was tested on 55 images of size 10 × 5 K and resulted in an accuracy of 94.60%. The developed methodology can also be part of the workflow for other diseases such as breast cancer and glioblastomas.

Molecular fixative enables expression microarray analysis of microdissected clinical cervical specimens.

Formalin-fixed tissue has been a mainstay of clinical pathology laboratories, but formalin alters many biomolecules, including nucleic acids and proteins. Meanwhile, frozen tissues contain better-preserved biomolecules, but tissue morphology is affected, limiting their diagnostic utility. Molecular fixatives promise to bridge this gap by simultaneously preserving morphology and biomolecules, enabling clinical diagnosis and molecular analyses on the same specimen. While previous reports have broadly evaluated the use of molecular fixative in various human tissues, we present here the first detailed assessment of the applicability of molecular fixative to both routine histopathological diagnosis and molecular analysis of cervical tissues. Ten specimens excised via the loop electrosurgical excision procedure, which removes conical tissue samples from the cervix, were cut into alternating pieces preserved in either formalin or molecular fixative. Cervical specimens preserved in molecular fixative were easily interpretable, despite featuring more eosinophilic cytoplasm and more recognizable chromatin texture than formalin-fixed specimens. Immunohistochemical staining patterns of p16 and Ki-67 were similar between fixatives, although Ki-67 staining was stronger in the molecular fixative specimens. The RNA of molecular fixative specimens from seven cases representing various dysplasia grades was assessed for utility in expression microarray analysis. Cluster analysis and scatter plots of duplicate samples suggest that data of sufficient quality can be obtained from as little as 50ng of RNA from molecular fixative samples. Taken together, our results show that molecular fixative may be a more versatile substitute for formalin, simultaneously preserving tissue morphology for clinical diagnosis and biomolecules for immunohistochemistry and gene expression analysis.

p16/Ki-67 dual staining in cervico-vaginal cytology: correlation with histology, Human Papillomavirus detection and genotyping in women undergoing colposcopy.

OBJECTIVES: To evaluate the CINtec PLUS assay (mtm laboratories), a new immunocytochemical method for the simultaneous detection of p16(INK4a) and Ki-67, in liquid-based cervico-vaginal cytology, investigating the association of the dual staining with HPV infection and genotyping as well as cytological and histological abnormalities. METHODS: 140 women with a cervico-vaginal sample obtained immediately before the colposcopy were enrolled. This cytological sample was used for HPV testing with the Linear Array HPV Genotyping Test, the dual staining with the CINtec PLUS kit and the morphology assessment. RESULTS: Cytology results were 38 NILM, 16 ASC-US, 32L-SIL, 54H-SIL or worse. 113 patients also had a colposcopy-guided biopsy, classified as 14 negative, 35 CIN1, 24 CIN2, 37 CIN3, 3 invasive SCC. A strong association between p16/Ki-67 and HR-HPV infection was found (COR=6.86, 95% CI: 1.84-31.14). Importantly, the association between p16/Ki-67 positivity and HPV16 and/or 18 infection was 2-fold stronger compared to that with the infection by other HR-HPV types (COR=9.92, 95% CI: 2.39-47.77 vs COR=4.20, 95% CI: 0.99-20.87). In addition, p16/Ki-67 positivity rate significantly increased with the severity of the cytological and histological abnormalities (p<0.05 in both cases). p16/Ki-67 positivity resulted strongly associated with a CIN2+ diagnosis (COR=10.86 95% CI: 4.16-29.12). CONCLUSIONS: This preliminary study evidenced that p16/Ki-67 immunostaining might have a relevant clinical role, since the dual staining was significantly associated with HR-HPV infection, particularly with HPV 16 and 18, and the increasing grade of the cervical lesions, the positivity for this biomarker being strongly related to the presence of a CIN2+ lesion.

Temozolomide as second or third line treatment of patients with neuroendocrine carcinomas.

BACKGROUND: Knowledge of the clinical efficacy in recurrent neuroendocrine carcinomas is sparse. Treatment with temozolomide alone or in combination with capecitabine and bevacizumab has recently shown promising results. PATIENTS AND METHODS: Analysis of consecutive patients with neuroendocrine carcinomas (Ki-67 proliferation index >20%) and performance status 0-2 treated with temozolomide 200 mg/sqm orally days 1-5 every 28 days after at least one previous platin-containing chemotherapy regimen. RESULTS: Twenty-eight eligible patients received a median of 3 courses. Sixteen patients were evaluable for response: Six achieved stable disease and ten progressed. The median survival for the 28 patients was 3.5 months. Survival in patients with tumors of pancreatic origin (n = 7) was 7.0 months versus 2.9 months in non-pancreatic origin (n = 21). Patients in PS 0-1 (n = 22) had a median survival of 4.5 months versus 1.1 months in patients in PS 2 (n = 6). Ki-67 index ≥ 50% was associated with a significantly shorter median survival than Ki-67 index <50% (2.7 months versus 10.9 months). The treatment was well tolerated. CONCLUSION: Temozolomide monotherapy has limited effect in treatment of recurrent neuroendocrine carcinomas. Second line treatment with temozolomide in combination with other compounds should be further investigated in patients in good performance with Ki-67 index <50%.

Direct observations of shifts in the ß-sheet register of a protein-peptide complex using explicit solvent simulations.

Using explicit solvent molecular dynamics simulations, we were able to obtain direct observations of shifts in the hydrogen-bonding register of an intermolecular ß-sheet protein-peptide complex. The ß-sheet is formed between the FHA domain of cancer marker protein Ki67 (Ki67FHA) and a peptide fragment of the hNIFK signaling protein. Potential encounter complexes of the Ki67FHA receptor and hNIFK peptide are misregistered states of the ß-sheet. Rearrangements of one of these misregistered states to the native state were captured in three independent simulations. All three rearrangements occurred by a common mechanism: an aromatic residue of the peptide (F263) anchors into a transient hydrophobic pocket of the receptor to facilitate the formation of native hydrogen bonds. To our knowledge, these simulations provide the first atomically detailed visualizations of a mechanism by which nature might correct for errors in the alignment of intermolecular ß-sheets.

Higher levels of cell apoptosis and abnormal E-cadherin expression in the urothelium are associated with inflammation in patients with interstitial cystitis/painful bladder syndrome.

OBJECTIVE: To investigate the relationships between suburothelial inflammation and urothelial dysfunction in interstitial cystitis/painful bladder syndrome (IC/PBlS). MATERIALS AND METHODS: Immunofluorescence staining of ki-67 (to assess cell proliferation), junction protein E-cadherin, tryptase (to assess mast cell activation) and TUNEL (to assess urothelial apoptosis) were performed in bladder tissues from 20 patients with IC/PBlS and from 6 control patients. The fluorescence intensity of E-cadherin was measured using the ImageJ method. The percentage of apoptotic cells, proliferated cells and activated mast cells were measured and quantified as positive cells (±SD) per area unit (4 µm(2)). RESULTS: The ratio of ki-67-positive cells in the bladder tissue of the patients with IC/PBlS was significantly down-regulated compared with that of the control patients (0.559 ± 0.658 vs. 1.23 ± 1.28, P = 0.001). TUNEL staining revealed a significantly higher number of apoptotic cells in the IC/PBlS bladder tissue compared with control bladder tissue (2.26 ± 2.04 v 0.051 ± 0.124, P = 0.000). The tryptase signal was significantly stronger in the IC/PBlS bladder tissue compared with that of control patients (6.16 ± 4.35 v 1.15 ± 0.436, P = 0.000). The apoptotic cell number in IC/PBlS bladder tissue correlated significantly with mast cell activation (P = 0.021). Immunofluorescence also showed a significantly lower distribution of E-cadherin in IC/PBlS bladder tissue compared with that of control patients (8.50 ± 6.83 v 17.2 ± 11.9, P = 0.000). Lower expression of E-cadherin in IC/PBlS bladder tissue was significantly correlated with higher visual analogue pain scores in patients with IC/PBlS (P= 0.008). CONCLUSIONS: The results of the present study suggest that urothelial homeostasis in IC/PBlS bladders was impaired, and abnormal urothelial function was significantly associated with chronic inflammation. The junctions between urothelial cells in IC/PBlS bladders were abnormal, which was associated with the patient's self-report pain scales.

The intrinsically disorderly story of Ki-67.

Ki-67 is one of the most famous marker proteins used by histologists to identify proliferating cells. Indeed, over 30 000 articles referring to Ki-67 are listed on PubMed. Here, we review some of the current literature regarding the protein. Despite its clinical importance, our knowledge of the molecular biology and biochemistry of Ki-67 is far from complete, and its exact molecular function(s) remain enigmatic. Furthermore, reports describing Ki-67 function are often contradictory, and it has only recently become clear that this proliferation marker is itself dispensable for cell proliferation. We discuss the unusual organization of the protein and its mRNA and how they relate to various models for its function. In particular, we focus on ways in which the intrinsically disordered structure of Ki-67 might aid in the assembly of the still-mysterious mitotic chromosome periphery compartment by controlling liquid-liquid phase separation of nucleolar proteins and RNAs.

Use of the Ki67 promoter to label cell cycle entry in living cells.

Genetic based reporters have distinct advantages over classical immunocytochemical techniques for probing cellular functions. Most importantly, they enable dynamic real-time visualization and quantification of cellular processes in living cells and tissue. This study was conducted to generate a genetic based reporter to label cells that transitioned from the G(0) to G(1)/S phases of the cell cycle, hypothesizing that the proximal promoter of the Ki67 (Ki67p) gene, a commonly used cytology marker induced during this transition, would contain the suitable regulatory elements to drive marker gene expression. This study reports the cloning and characterization of the 1.5 kb proximal promoter (Ki67p) of the human Ki67 gene. Ki67p driven GFP expression colocalizes in cells with endogenous Ki67 expression and is correlated with cells transitioning through S/G(2)/M phases of the cell cycle. Treatment Ki67p-GFP expressing HT1080 cells with mitomycin C, an antineoplastic agent, induces P21 and P27 expression, G(1)/S/G(2)M block and attenuates Ki67p activity. Attenuation of the Ki67p also occurs during cell-density induced cell cycle arrest. Taken together, these results indicate that the Ki67p can be used to identify proliferating subpopulations of live cells in intact complex three-dimensional cellular aggregates, such as embryoid bodies, thus providing some unique advantages over conventional immunohistochemical approaches.

Sequential phosphorylation and multisite interactions characterize specific target recognition by the FHA domain of Ki67.

The forkhead-associated (FHA) domain of human Ki67 interacts with the human nucleolar protein hNIFK, recognizing a 44-residue fragment, hNIFK226-269, phosphorylated at Thr234. Here we show that high-affinity binding requires sequential phosphorylation by two kinases, CDK1 and GSK3, yielding pThr238, pThr234 and pSer230. We have determined the solution structure of Ki67FHA in complex with the triply phosphorylated peptide hNIFK226-269(3P), revealing not only local recognition of pThr234 but also the extension of the beta-sheet of the FHA domain by the addition of a beta-strand of hNIFK. The structure of an FHA domain in complex with a biologically relevant binding partner provides insights into ligand specificity and potentially links the cancer marker protein Ki67 to a signaling pathway associated with cell fate specification.

Two ways to inactivate the Ki-67 protein-Fragmentation by nanoparticles, crosslinking with fluorescent dyes.

Light can manipulate molecular biological processes with high spatial and temporal precision and optical manipulation has become increasingly popular during the last years. In combination with absorbing dyes or gold nanoparticles light is a valuable tool for cell and protein inactivation with high precision. Here we show distinct differences in the underlying mechanisms whether gold nanoparticles or fluorescent dyes are used for the inactivation of the Ki-67 protein. The proliferation-associated protein Ki-67 was addressed by the antibody MIB-1. In vitro studies showed a fragmentation of the Ki-67 protein after laser irradiation of 15 nm gold nanoparticle antibody conjugates with nanosecond pulsed laser, while continuous wave (cw) irradiation of fluorescein isothiocyanate (FITC)- and Alexa 488-labeled antibodies led to specific crosslinking of Ki-67. The irradiation energy for the gold nanoparticles was above cavitation bubble formation threshold. We observed a fragmentation of the target protein and also of the gold particles. The understanding of the underlying inactivation mechanisms is important for the application and further development of these two techniques, which can harness nanotechnology to introduce molecular selectivity to biological systems.

Pixel-to-Pixel Learning With Weak Supervision for Single-Stage Nucleus Recognition in Ki67 Images.

OBJECTIVE: Nucleus recognition is a critical yet challenging step in histopathology image analysis, for example, in Ki67 immunohistochemistry stained images. Although many automated methods have been proposed, most use a multi-stage processing pipeline to categorize nuclei, leading to cumbersome, low-throughput, and error-prone assessments. To address this issue, we propose a novel deep fully convolutional network for single-stage nucleus recognition. METHODS: Instead of conducting direct pixel-wise classification, we formulate nucleus identification as a deep structured regression model. For each input image, it produces multiple proximity maps, each of which corresponds to one nucleus category and exhibits strong responses in central regions of the nuclei. In addition, by taking into consideration the nucleus distribution in histopathology images, we further introduce an auxiliary task, region of interest (ROI) extraction, to assist and boost the nucleus quantification with weak ROI annotation. The proposed network can be learned in an end-to-end, pixel-to-pixel manner for simultaneous nucleus detection and classification. RESULTS: We have evaluated this network on a pancreatic neuroendocrine tumor Ki67 image dataset, and the experiments demonstrate that our method outperforms recent state-of-the-art approaches. CONCLUSION: We present a new, pixel-to-pixel deep neural network with two sibling branches for effective nucleus recognition and observe that learning with another relevant task, ROI extraction, can further boost individual nucleus localization and classification. SIGNIFICANCE: Our method provides a clean, single-stage nucleus recognition pipeline for histopathology image analysis, especially a new perspective for Ki67 image quantification, which would potentially benefit individual object quantification in whole-slide images.

CytoLyt fixation significantly inhibits MIB1 immunoreactivity whereas alternative Ki-67 clone 30-9 is not susceptible to the inhibition: Critical diagnostic implications.

BACKGROUND: The Ki-67 proliferation marker has multiple diagnostic and prognostic applications. Although several clones to the Ki-67 antigen are commercially available, the MIB1 clone is widely recommended in the surgical pathology literature for neuroendocrine tumors. In our cytopathology practice, we have encountered unexpectedly low MIB1 immunoreactivity in CytoLyt-fixed cell blocks (CBs). The current study evaluated the impact of fixatives, CB processing, and immunocytochemical (ICC) procedures on Ki-67 immunoreactivity. METHODS: Test CBs were prepared from freshly resected tumors, and multiple variables in the MIB1 ICC procedure were tested, including CytoLyt versus formalin collection media, MIB1 versus other Ki-67 clones including 30-9, and other variables. MIB1 versus Ki-67 30-9 clones were tested in parallel on CytoLyt-fixed CBs from clinical samples of small cell lung carcinoma (SCLC). RESULTS: In the test CBs (n = 10), the mean MIB1 labeling index was 10% in CytoLyt versus 47% in formalin (P = .0116), with a mean loss of reactivity in matched CBs of 37% (up to 70%). None of the procedure modifications tested in 223 individual ICC reactions recovered MIB1 reactivity in CytoLyt except for switching to the Ki-67 30-9 antibody. In CytoLyt-fixed SCLC samples (n = 14), the Ki-67 30-9 antibody demonstrated expected ranges of reactivity (mean, 83%; range, 60%-100%), whereas MIB1 demonstrated markedly inhibited labeling (mean, 60%; range, 10%-95%) (P = .0058). CONCLUSIONS: CytoLyt fixation substantially inhibits MIB1 immunoreactivity, whereas the Ki-67 30-9 clone is not susceptible to inhibition. Markedly discrepant MIB1 reactivity may present a pitfall in the diagnosis of SCLC and may lead to the incorrect prognostic stratification of other tumor types. For laboratories using CytoLyt, we recommend using the Ki-67 30-9 antibody rather than the MIB1 antibody.

Role of Kif15 and its novel mitotic partner KBP in K-fiber dynamics and chromosome alignment.

Faithful segregation of the genetic material during the cell cycle is key for the continuation of life. Central to this process is the assembly of a bipolar spindle that aligns the chromosomes and segregates them to the two daughter cells. Spindle bipolarity is strongly dependent on the activity of the homotetrameric kinesin Eg5. However, another kinesin, Kif15, also provides forces needed to separate the spindle poles during prometaphase and to maintain spindle bipolarity at metaphase. Here we identify KBP as a specific interaction partner of Kif15 in mitosis. We show that KBP promotes the localization of Kif15 to the spindle equator close to the chromosomes. Both Kif15 and KBP are required for the alignment of all the chromosomes to the metaphase plate and the assembly of stable kinetochore fibers of the correct length. Taken together our data uncover a novel role for Kif15 in complex with KBP during mitosis.

Heat-induced Epitope Retrieval for Immunohistochemistry at High Altitude: A Quality Assurance Study.

INTRODUCTION: Heat-induced epitope retrieval (HIER) of formalin-fixed paraffin-embedded tissues is now a standard practice in immunohistochemistry (IHC). In this study, we aimed to test the effect of altering HIER temperature on IHC staining quality at high altitude, the hypothesis being that lower HIER temperatures would result in improved staining patterns. MATERIALS AND METHODS: In a laboratory at high altitude (Aurora, CO), we used a platform with automated onboard epitope retrieval, and systematically tested 3 different HIER temperatures (100°C, 95°C, 90°C) with 4 IHC stains that are commonly used in routine practice: CD3, Ki67, CK20, and Melan A (n=10 for each antibody/epitope retrieval temperature combination). A scoring system was devised, the slides were scored in a blinded manner, and statistical analysis was performed. For comparison, the same study was performed in a laboratory near sea level (Atlanta, GA). RESULTS: At high altitude, lower HIER temperatures resulted in improved staining patterns, as quantified by stronger staining intensity and greater area of the slides stained. The scores obtained with HIER temperatures of 95°C and 90°C were higher than those obtained with HIER of 100°C, and the difference was found to be statistically significantly for some antibody/epitope retrieval temperature combinations (P<0.05). This effect was not seen in the laboratory near sea level. CONCLUSIONS: We show that alternate epitope retrieval recommendations are warranted for laboratories at high altitude. Furthermore, we suggest that manufactures should consider how their instruments will perform at high altitude as they further automate the process of IHC.