Tight junction membrane proteins regulate the mechanical resistance of the apical junctional complex

Epithelia must be able to resist mechanical force to preserve tissue integrity. While intercellular junctions are known to be important for the mechanical resistance of epithelia, the roles of tight junctions (TJs) remain to be established. We previously demonstrated that epithelial cells devoid of the TJ membrane proteins claudins and JAM-A completely lack TJs and exhibit focal breakages of their apical junctions. Here, we demonstrate that apical junctions fracture when claudin/JAM-A-deficient cells undergo spontaneous cell stretching. The junction fracture was accompanied by actin disorganization, and actin polymerization was required for apical junction integrity in the claudin/JAM-A-deficient cells. Further deletion of CAR resulted in the disruption of ZO-1 molecule ordering at cell junctions, accompanied by severe defects in apical junction integrity. These results demonstrate that TJ membrane proteins regulate the mechanical resistance of the apical junctional complex in epithelial cells.

Previous fracture and subsequent fracture risk: a meta-analysis to update FRAX

A large international meta-analysis using primary data from 64 cohorts has quantified the increased risk of fracture associated with a previous history of fracture for future use in FRAX.

INTRODUCTION

The aim of this study was to quantify the fracture risk associated with a prior fracture on an international basis and to explore the relationship of this risk with age, sex, time since baseline and bone mineral density (BMD).

METHODS

We studied 665,971 men and 1,438,535 women from 64 cohorts in 32 countries followed for a total of 19.5 million person-years. The effect of a prior history of fracture on the risk of any clinical fracture, any osteoporotic fracture, major osteoporotic fracture, and hip fracture alone was examined using an extended Poisson model in each cohort. Covariates examined were age, sex, BMD, and duration of follow-up. The results of the different studies were merged by using the weighted β-coefficients.

RESULTS

A previous fracture history, compared with individuals without a prior fracture, was associated with a significantly increased risk of any clinical fracture (hazard ratio, HR = 1.88; 95% CI = 1.72-2.07). The risk ratio was similar for the outcome of osteoporotic fracture (HR = 1.87; 95% CI = 1.69-2.07), major osteoporotic fracture (HR = 1.83; 95% CI = 1.63-2.06), or for hip fracture (HR = 1.82; 95% CI = 1.62-2.06). There was no significant difference in risk ratio between men and women. Subsequent fracture risk was marginally downward adjusted when account was taken of BMD. Low BMD explained a minority of the risk for any clinical fracture (14%), osteoporotic fracture (17%), and for hip fracture (33%). The risk ratio for all fracture outcomes related to prior fracture decreased significantly with adjustment for age and time since baseline examination.

CONCLUSION

A previous history of fracture confers an increased risk of fracture of substantial importance beyond that explained by BMD. The effect is similar in men and women. Its quantitation on an international basis permits the more accurate use of this risk factor in case finding strategies.

Tight junction formation by a claudin mutant lacking the COOH-terminal PDZ domain-binding motif

Claudin-based tight junctions (TJs) are formed at the most apical part of cell-cell contacts in epithelial cells. Previous studies suggest that scaffolding proteins ZO-1 and ZO-2 (ZO proteins) determine the location of TJs by interacting with claudins, but this idea is not conclusive. To address the role of the ZO proteins binding to claudins at TJs, a COOH-terminal PDZ domain binding motif-deleted claudin-3 mutant, which lacks the ZO protein binding, was stably expressed in claudin-deficient MDCK cells. The COOH-terminus-deleted claudin-3 was localized at the apicolateral region similar to full-length claudin-3. Consistently, freeze-fracture electron microscopy revealed that the COOH-terminus-deleted claudin-3-expressing cells reconstituted belts of TJs at the most apical region of the lateral membrane and restored functional epithelial barriers. These results suggest that the interaction of claudins with ZO proteins is not a prerequisite for TJ formation at the most apical part of cell-cell contacts.

Update of the fracture risk prediction tool FRAX: a systematic review of potential cohorts and analysis plan

We describe the collection of cohorts together with the analysis plan for an update of the fracture risk prediction tool FRAX with respect to current and novel risk factors. The resource comprises 2,138,428 participants with a follow-up of approximately 20 million person-years and 116,117 documented incident major osteoporotic fractures.

INTRODUCTION

The availability of the fracture risk assessment tool FRAX® has substantially enhanced the targeting of treatment to those at high risk of fracture with FRAX now incorporated into more than 100 clinical osteoporosis guidelines worldwide. The aim of this study is to determine whether the current algorithms can be further optimised with respect to current and novel risk factors.

METHODS

A computerised literature search was performed in PubMed from inception until May 17, 2019, to identify eligible cohorts for updating the FRAX coefficients. Additionally, we searched the abstracts of conference proceedings of the American Society for Bone and Mineral Research, European Calcified Tissue Society and World Congress of Osteoporosis. Prospective cohort studies with data on baseline clinical risk factors and incident fractures were eligible.

RESULTS

Of the 836 records retrieved, 53 were selected for full-text assessment after screening on title and abstract. Twelve cohorts were deemed eligible and of these, 4 novel cohorts were identified. These cohorts, together with 60 previously identified cohorts, will provide the resource for constructing an updated version of FRAX comprising 2,138,428 participants with a follow-up of approximately 20 million person-years and 116,117 documented incident major osteoporotic fractures. For each known and candidate risk factor, multivariate hazard functions for hip fracture, major osteoporotic fracture and death will be tested using extended Poisson regression. Sex- and/or ethnicity-specific differences in the weights of the risk factors will be investigated. After meta-analyses of the cohort-specific beta coefficients for each risk factor, models comprising 10-year probability of hip and major osteoporotic fracture, with or without femoral neck bone mineral density, will be computed.

CONCLUSIONS

These assembled cohorts and described models will provide the framework for an updated FRAX tool enabling enhanced assessment of fracture risk (PROSPERO (CRD42021227266)).

Assessment of Heating on Titanium Alloy Cerebral Aneurysm Clips during 7T MRI

BACKGROUND AND PURPOSE

Patients with cerebral aneurysms often undergo MR imaging after microsurgical clipping. Ultra-high-field MR imaging at 7T may provide high diagnostic capability in such clinical situations. However, titanium alloy clips have safety issues such as adverse interactions with static magnetic fields and radiofrequency-induced heating during 7T MR imaging. The purpose of this study was to quantitatively assess temperature increases on various types of titanium alloy aneurysm clips during 7T MR imaging.

MATERIALS AND METHODS

Five types of titanium alloy aneurysm clips were tested, including combinations of short, long, straight, angled, and fenestrated types. Each clip was set in a phantom filled with gelled saline mixed with polyacrylic acid and underwent 7T MR imaging with 3D T1WI with a spoiled gradient recalled acquisition in the steady-state technique. Temperature was chronologically measured at the tips of the clip blade and head, angled part of the clip, and 5 mm from the tip of the clip head using MR imaging-compatible fiber-optic thermometers.

RESULTS

Temperature increases at all locations for right-angled and short straight clips were <1°C. Temperature increases at the angled part for the 45° angled clip and the tip of the clip head for the straight fenestrated clip were >1°C. Temperature increases at all locations for the long straight clip were >2°C.

CONCLUSIONS

Temperature increases on the right-angled and short straight clips remained below the regulatory limit during 7T MR imaging, but temperature increases on the 45° angled, straight fenestrated, and long straight clips exceeded this limit.

Diagnostic Accuracy of Screening Arterial Spin-Labeling MRI Using Hadamard Encoding for the Detection of Reduced CBF in Adult Patients with Ischemic Moyamoya Disease

BACKGROUND AND PURPOSE

Adult patients with ischemic Moyamoya disease are advised to undergo selective revascularization surgery based on cerebral hemodynamics. The purpose of this study was to determine the diagnostic accuracy of arterial spin-labeling MR imaging using Hadamard-encoded multiple postlabeling delays for the detection of reduced CBF in such patients.

MATERIALS AND METHODS

Thirty-seven patients underwent brain perfusion SPECT and pseudocontinuous arterial spin-labeling MR imaging using standard postlabeling delay (1525 ms) and Hadamard-encoded multiple postlabeling delays. For Hadamard-encoded multiple postlabeling delays, based on data obtained from the 7 sub-boluses with combinations of different labeling durations and postlabeling delays, CBF corrected by the arterial transit time was calculated on a voxel-by-voxel basis. Using a 3D stereotaxic template, we automatically placed ROIs in the ipsilateral cerebellar hemisphere and 5 MCA territories in the symptomatic cerebral hemisphere; then, the ratio of the MCA to cerebellar ROI was calculated.

RESULTS

The area under the receiver operating characteristic curve for detecting reduced SPECT-CBF ratios (<0.686) was significantly greater for the Hadamard-encoded multiple postlabeling delays-CBF ratios (0.885) than for the standard postlabeling delay-CBF ratios (0.786) (P = .001). The sensitivity and negative predictive value for the Hadamard-encoded multiple postlabeling delays-CBF ratios were 100% (95% confidence interval, 100%-100%) and significantly higher than the sensitivity (95% CI, 44%-80%) and negative predictive value (95% CI, 88%-97%) for the standard postlabeling delay-CBF ratio, respectively.

CONCLUSIONS

ASL MR imaging using Hadamard-encoded multiple postlabeling delays may be applicable as a screening tool because it can detect reduced CBF on brain perfusion SPECT with 100% sensitivity and a 100% negative predictive value in adult patients with ischemic Moyamoya disease.

Toxic effects of endoplasmic reticulum stress transducer BBF2H7-derived small peptide fragments on neuronal cells

Aggregation, fibril formation, and deposition of amyloid β (Aβ) protein are believed to be the central pathogeneses of Alzheimer's disease (AD). Numerous studies have shown that fibril formation is promoted by preformed seeds at the beginning of the aggregation process. Therefore, aggregated molecules that promote fibrillization of Aβ protein as seeds could affect the pathology. We recently found that approximately 40 amino acid hydrophobic peptides, BBF2H7-derived small peptide (BSP) fragments, are generated via intramembranous cleavage under endoplasmic reticulum (ER) stress conditions. Interestingly, similar to Aβ protein, the fragments exhibit a high aggregation propensity and form fibril structures. It has been noted that ER stress is involved in the pathogenesis of AD. In this study, we examined the effect of BSP fragments on aggregation and cytotoxicity of Aβ_1-40 protein, which is generated as a major species of Aβ protein, but has a lower aggregative property than Aβ_1-42 protein. We demonstrated that BSP fragments promote aggregation of Aβ_1-40 protein. Aggregates of Aβ_1-40 protein mediated by BSP fragments also exhibited potent neurotoxicity. Our findings suggest the possibility that BSP fragments affect accumulation of Aβ proteins and are involved in the pathogenesis of AD.

Disease-associated keratin mutations reduce traction forces and compromise adhesion and collective migration

Keratin intermediate filament (IF) proteins constitute the major cytoskeletal components in epithelial cells. Missense mutations in keratin 5 (K5; also known as KRT5) or keratin 14 (K14; also known as KRT14), highly expressed in the basal epidermis, cause the severe skin blistering disease epidermolysis bullosa simplex (EBS). EBS-associated mutations disrupt keratin networks and change keratinocyte mechanics; however, molecular mechanisms by which mutations shape EBS pathology remain incompletely understood. Here, we demonstrate that, in contrast to keratin-deficient keratinocytes, cells expressing K14R125C, a mutation that causes severe EBS, generate lower traction forces, accompanied by immature focal adhesions with an altered cellular distribution. Furthermore, mutant keratinocytes display reduced directionality during collective migration. Notably, RhoA activity is downregulated in human EBS keratinocytes, and Rho activation rescues stiffness-dependent cell-extracellular matrix (ECM) adhesion formation of EBS keratinocytes. Collectively, our results strongly suggest that intact keratin IF networks regulate mechanotransduction through a Rho signaling pathway upstream of cell-ECM adhesion formation and organized cell migration. Our findings provide insights into the underlying pathophysiology of EBS.This article has an associated First Person interview with the first author of the paper.

Acetazolamide-Loaded Dynamic 7T MR Quantitative Susceptibility Mapping in Major Cerebral Artery Steno-Occlusive Disease: Comparison with PET

BACKGROUND AND PURPOSE

Dynamic changes in cerebrovascular reactivity after acetazolamide administration vary markedly among patients with major cerebral arterial steno-occlusive disease. MR quantitative susceptibility mapping can dynamically quantify the cerebral magnetic susceptibility. The purpose of this study was to determine whether dynamic changes in susceptibility after administration of acetazolamide on 7T quantitative susceptibility mapping are associated with pre-existing states of CBV and the cerebral metabolic rate of oxygen in the cerebral hemispheres with major cerebral arterial steno-occlusive disease.

MATERIALS AND METHODS

Sixty-five patients underwent 7T MR imaging at baseline and at 5, 10, 15, and 20 minutes after acetazolamide administration. Differences between the susceptibility of venous structures and surrounding brain tissue were calculated in the quantitative susceptibility mapping images. Susceptibility differences at 5, 10, 15, and 20 minutes after acetazolamide administration relative to baseline were calculated in 97 cerebral hemispheres with major cerebral arterial steno-occlusive disease. CBV and the cerebral metabolic rate of oxygen were also calculated using ¹⁵O-gas PET in the resting state.

RESULTS

Dynamic changes of susceptibility after acetazolamide administration were classified into 3 patterns: abnormally increasing 5 or 10 minutes after acetazolamide administration; abnormally decreasing within 20 minutes after acetazolamide administration; and remaining unchanged after acetazolamide administration. CBV was significantly greater in the first pattern than in the latter 2. The cerebral metabolic rate of oxygen differed significantly in descending order from the first to middle to last pattern.

CONCLUSIONS

Dynamic changes of susceptibility after acetazolamide administration on 7T MR quantitative susceptibility mapping are associated with pre-existing states of CBV and the cerebral metabolic rate of oxygen in major cerebral arterial steno-occlusive disease.

The Rho-guanine nucleotide exchange factor Solo decelerates collective cell migration by modulating the Rho-ROCK pathway and keratin networks

Collective cell migration plays crucial roles in tissue remodeling, wound healing, and cancer cell invasion. However, its underlying mechanism remains unknown. Previously, we showed that the RhoA-targeting guanine nucleotide exchange factor Solo (ARHGEF40) is required for tensile force–induced RhoA activation and proper organization of keratin-8/keratin-18 (K8/K18) networks. Here, we demonstrate that Solo knockdown significantly increases the rate at which Madin-Darby canine kidney cells collectively migrate on collagen gels. However, it has no apparent effect on the migratory speed of solitary cultured cells. Therefore, Solo decelerates collective cell migration. Moreover, Solo localized to the anteroposterior regions of cell–cell contact sites in collectively migrating cells and was required for the local accumulation of K8/K18 filaments in the forward areas of the cells. Partial Rho-associated protein kinase (ROCK) inhibition or K18 or plakoglobin knockdown also increased collective cell migration velocity. These results suggest that Solo acts as a brake for collective cell migration by generating pullback force at cell–cell contact sites via the RhoA-ROCK pathway. It may also promote the formation of desmosomal cell–cell junctions related to K8/K18 filaments and plakoglobin.

Solo, a RhoA-targeting guanine nucleotide exchange factor, is critical for hemidesmosome formation and acinar development in epithelial cells

Cell-substrate adhesions are essential for various physiological processes, including embryonic development and maintenance of organ functions. Hemidesmosomes (HDs) are multiprotein complexes that attach epithelial cells to the basement membrane. Formation and remodeling of HDs are dependent on the surrounding mechanical environment; however, the upstream signaling mechanisms are not well understood. We recently reported that Solo (also known as ARHGEF40), a guanine nucleotide exchange factor targeting RhoA, binds to keratin8/18 (K8/K18) intermediate filaments, and that their interaction is important for force-induced actin and keratin cytoskeletal reorganization. In this study, we show that Solo co-precipitates with an HD protein, β4-integrin. Co-precipitation assays revealed that the central region (amino acids 330–1057) of Solo binds to the C-terminal region (1451–1752) of β4-integrin. Knockdown of Solo significantly suppressed HD formation in MCF10A mammary epithelial cells. Similarly, knockdown of K18 or treatment with Y-27632, a specific inhibitor of Rho-associated kinase (ROCK), suppressed HD formation. As Solo knockdown or Y-27632 treatment is known to disorganize K8/K18 filaments, these results suggest that Solo is involved in HD formation by regulating K8/K18 filament organization via the RhoA-ROCK signaling pathway. We also showed that knockdown of Solo impairs acinar formation in MCF10A cells cultured in 3D Matrigel. In addition, Solo accumulated at the site of traction force generation in 2D-cultured MCF10A cells. Taken together, these results suggest that Solo plays a crucial role in HD formation and acinar development in epithelial cells by regulating mechanical force-induced RhoA activation and keratin filament organization.

Preoperative Cerebral Oxygen Extraction Fraction Imaging Generated from 7T MR Quantitative Susceptibility Mapping Predicts Development of Cerebral Hyperperfusion following Carotid Endarterectomy

BACKGROUND AND PURPOSE

Preoperative hemodynamic impairment in the affected cerebral hemisphere is associated with the development of cerebral hyperperfusion following carotid endarterectomy. Cerebral oxygen extraction fraction images generated from 7T MR quantitative susceptibility mapping correlate with oxygen extraction fraction images on positron-emission tomography. The present study aimed to determine whether preoperative oxygen extraction fraction imaging generated from 7T MR quantitative susceptibility mapping could identify patients at risk for cerebral hyperperfusion following carotid endarterectomy.

MATERIALS AND METHODS

Seventy-seven patients with unilateral internal carotid artery stenosis (≥70%) underwent preoperative 3D T2*-weighted imaging using a multiple dipole-inversion algorithm with a 7T MR imager. Quantitative susceptibility mapping images were then obtained, and oxygen extraction fraction maps were generated. Quantitative brain perfusion single-photon emission CT was also performed before and immediately after carotid endarterectomy. ROIs were automatically placed in the bilateral middle cerebral artery territories in all images using a 3D stereotactic ROI template, and affected-to-contralateral ratios in the ROIs were calculated on quantitative susceptibility mapping-oxygen extraction fraction images.

RESULTS

Ten patients (13%) showed post-carotid endarterectomy hyperperfusion (cerebral blood flow increases of ≥100% compared with preoperative values in the ROIs on brain perfusion SPECT). Multivariate analysis showed that a high quantitative susceptibility mapping-oxygen extraction fraction ratio was significantly associated with the development of post-carotid endarterectomy hyperperfusion (95% confidence interval, 33.5-249.7; P = .002). Sensitivity, specificity, and positive- and negative-predictive values of the quantitative susceptibility mapping-oxygen extraction fraction ratio for the prediction of the development of post-carotid endarterectomy hyperperfusion were 90%, 84%, 45%, and 98%, respectively.

CONCLUSIONS

Preoperative oxygen extraction fraction imaging generated from 7T MR quantitative susceptibility mapping identifies patients at risk for cerebral hyperperfusion following carotid endarterectomy.

Roles of the cytoskeleton, cell adhesion and rho signalling in mechanosensing and mechanotransduction

All cells sense and respond to various mechanical forces in and mechanical properties of their environment. To respond appropriately, cells must be able to sense the location, direction, strength and duration of these forces. Recent progress in mechanobiology has provided a better understanding of the mechanisms of mechanoresponses underlying many cellular and developmental processes. Various roles of mechanoresponses in development and tissue homeostasis have been elucidated, and many molecules involved in mechanotransduction have been identified. However, the whole picture of the functions and molecular mechanisms of mechanotransduction remains to be understood. Recently, novel mechanisms for sensing and transducing mechanical stresses via the cytoskeleton, cell-substrate and cell-cell adhesions and related proteins have been identified. In this review, we outline the roles of the cytoskeleton, cell-substrate and cell-cell adhesions, and related proteins in mechanosensing and mechanotransduction. We also describe the roles and regulation of Rho-family GTPases in mechanoresponses.

The effects of administration of the Lactobacillus gasseri strain CP2305 on quality of life, clinical symptoms and changes in gene expression in patients with irritable bowel syndrome

AIMS

To clarify the effects of Lactobacillus gasseri CP2305 (CP2305) on quality of life and clinical symptoms and its functional mechanisms in patients with irritable bowel syndrome (IBS).

METHODS AND RESULTS

After the patients were administered CP2305 daily for 4 weeks, the IBS-severity index score was significantly improved compared with that of the placebo group, and this improvement was accompanied by a reduction in health-related worry and changes in intestinal microbiota. The gene expression profiling of the peripheral blood leucocytes showed that CP2305 treatment significantly up-regulated genes related to eukaryotic initiation factor 2 (EIF2) signalling. Eighty-two genes were down-regulated in IBS patients compared with healthy controls. The expression of 23 of these genes exhibited a CP2305-dependent increase associated with an improvement in IBS severity. The majority of the restored genes were related to EIF2 signalling.

CONCLUSIONS

CP2305 administration is a potential candidate therapeutic option for patients with IBS.

SIGNIFICANCE AND IMPACT OF THE STUDY

Although probiotics have been proposed to benefit IBS patients, objective clinical evidence and elucidation of the functional mechanism remain insufficient. Our study demonstrated that CP2305 administration beneficially influences IBS patients in both subjective and objective evaluations, and gene expression profiling provided insights into the functional mechanism.

Controlling joint instability delays the degeneration of articular cartilage in a rat model

OBJECTIVE

Joint instability induced by anterior cruciate ligament (ACL) transection is commonly considered as a predisposing factor for osteoarthritis (OA) of the knee; however, the influence of re-stabilization on the protection of articular cartilage is unclear. The aim of this study was to evaluate the effect of joint re-stabilization on articular cartilage using an instability and re-stabilization ACL transection model.

DESIGN

To induce different models of joint instability, our laboratory created a controlled abnormal joint movement (CAJM) group and an anterior cruciate ligament transection group (ACL-T). Seventy-five Wistar male rats were randomly assigned to the CAJM (n = 30), ACL-T (n = 30), or no treatment (INTACT) group (n = 15). Cartilage changes were assessed with soft X-ray analysis, histological and immunohistochemistry analysis, and real-time polymerase chain reaction (PCR) analysis at 2, 4, and 12 weeks.

RESULTS

Joint instability, as indicated by the difference in anterior displacement between the CAJM and ACL-T groups (P < 0.001), and cartilage degeneration, as evaluated according to the Osteoarthritis Research Society International (OARSI) score, were significantly higher in the ACL-T group than the CAJM group at 12 weeks (P < 0.001). Moreover, joint re-stabilization maintained cartilage structure (thickness [P < 0.001], surface roughness [P < 0.001], and glycosaminoglycan stainability [P < 0.001]) and suppressed tumor necrosis factor-alpha (TNF-α) and caspase-3 at 4 weeks after surgery.

CONCLUSION

Re-stabilization of joint instability may suppress inflammatory cytokines, thereby delaying the progression of OA. Joint instability is a substantial contributor to cartilage degeneration.

Hypofibrinolytic Activity after Total Joint Replacement

Tissue-type plasminogen activator (t-PA), tissue-type plasminogen activator inhibitor (t-PAI), and other factors (platelets, fibrinogen, fibrinogen degrada tion products, antithrombin-III, plasminogen, and α2-plasmin inhibitor [α2-PI]) related to the fibrinolytic system were studied in 21 patients undergoing total joint replacement.

Seventeen of the 21 patients revealed an impaired fibrinolytic activity from the first to seventh postoperative day and a subsequent return to the preopera tive level by the fourteenth postoperative day. There were accompanying increases in the level of α2-PI and in the t-PAI/t-PA ratio, and there was decrease in plas minogen level. Such hypofibrinolytic states may be related to a higher incidence of postoperative thrombosis in total joint replacement patients.

Abstract P3-05-10: Non-coding RNAs derived from near the ESR1 gene acts as a transcriptional regulator during estrogen deprivation adaptation of ER positive breast cancer cells

Endocrine therapies that blocks estrogen production are effective for estrogen receptor (ER)-positive breast cancer. However, endocrine therapy treated patients eventually experience relapse after a long period of estrogen deprivation. The mechanism underlying acquisition of estrogen independent growth by ER positive breast cancer cells remains unclear.

To understand such molecular mechanism, we used a cell model LTED (long term estrogen deprivation) which MCF7 cells were cultured under estrogen deprivation for 4-10 months. In LTED cells, we found that ER encoded gene ESR1 was up-regulated and ER overproduction was essential for estrogen-independent cell growth. We also revealed that RNA transcriptions of the ESR1 and several neighbor genes were co-induced from both coding and non-coding regions in LTED cells, using RNA-sequence. These highly transcribed regions were corresponded to active histone modifications and transcription factor bindings according to publically available genome-wide analyses data. Fluorescence in situ hybridization (FISH) analyses indicated that RNA from the chromatin domain region nearby ESR1 were co-localized and made foci in nucleus.

We found non-coding regions that are particularly highly transcribed. FISH analyses indicated that RNAs from these regions might interact with the parental ESR1 gene locus. Recent studies have shown that non-coding RNAs are involved in transcriptional regulation and chromatin regulation. To understand the role of the non-coding RNA, we have generated MCF7 cells lines that lack the non-coding site, using CRISPR/CAS9 system. We found that mRNA transcription of multiple genes including ESR1 were impaired by the deletion. These findings suggested that these non-coding RNAs may be involved in chromatin regulation of the chromatin domain nearby ESR1.

In this study, we found non-coding RNAs that control transcription of chromatin domain genes in ER positive breast cancer cells. Such non-coding RNA mediated transcriptional regulation might be critical for endocrine therapy resistance adaptation.

Citation Format: Fujiwara S, Saitoh N, Tomita S, Abdalla MO, Iwase H, Nakao M. Non-coding RNAs derived from near the ESR1 gene acts as a transcriptional regulator during estrogen deprivation adaptation of ER positive breast cancer cells. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-05-10.

Abstract P6-07-07: Clinical significance of ESR1 mutations using droplet digital polymerase chain reaction assay in 325 breast cancer samples

Purpose: We aimed to develop a droplet digital Polymerase Chain Reaction (ddPCR)-based method for the sensitive detection of estrogen receptor (ER) α (ESR1) mutations in the primary and recurrent/metastatic tumor tissues of breast cancer.

Experimental Design: We studied a total of 325 tumor specimens (270 primary breast cancer specimens and 55 ER-positive recurrent/metastatic tumor specimens). Because the recurrent/metastatic tumor specimens had much inflammatory and stromal cells, we captured only tumor cells using laser microdissection. We investigated the quantification of rare ESR1 mutations, four representative types, Y537S, Y537N, Y537C, and D538G in extracted genomic DNA using ddPCR system that simultaneously performed thousands of PCRs on a nanoliter scale.

Results: In 270 primary breast cancer samples, we analyzed each ESR1 alteration percentage in each subtype. ESR1 Y537C tended to be higher in hormone receptor-positive (HR+)/ human epidermal growth factor receptor 2-negative (HER2-) group (P = 0.06) and higher percentage of ESR1 D538G was statistically significant in HR+/ HER2- group (P = 0.027), compared with HER2+ group. There was no statistically different in each ESR1 alteration percentage between HR+/ HER2- group and HR-/ HER2- group. Whether each ESR1 alteration was dichotomized as positive or not, we used the percentage which HER2+ group and HR-/ HER2- were not identified, as a cutoff point. ESR1 mutations occurred in 7 samples (2.5%) out of 270 primary samples, but ESR1 mutations occurred in 11 samples (20%) out of 55 metastatic/ recurrent breast cancer samples.

Table 1 Patients characteristics of 11 metastatic ER-positive breast cancer cases with ESR1 mutationsCaseAge (years)HER2 statusKi67 LIER HSPgR HSBiopsy siteMutation472-102051Lymph nodeY537C 1610 A&gt;G only665-518218Lymph nodeY537S 1610 A&gt;C Y537N 1609 T&gt;A D538G 1613 A&gt;G1555-201105SkinY537C 1610 A&gt;G only1863-10162130Lymph nodeD538G 1613 A&gt;G only3354-417015Lymph nodeY537S 1610 A&gt;C Y537N 1609 T&gt;A D538G 1613 A&gt;G4268-516950SkinY537C 1610 A&gt;G only4466-24270159Lymph nodeY537N 1609 T&gt;A only4673-20224110Lymph nodeY537N 1609 T&gt;A and D538G 1613 A&gt;G4952-20275138SkinY537S 1610 A&gt;C and Y537C 1610 A&gt;G5040-101740Lymph nodeY537S 1610 A&gt;C only5140-101895IBTRY537S 1610 A&gt;C onlyAbbreviations: HER2, human epidermal growth factor receptor 2; LI, labeling index; ER, estrogen receptor; HS, histoscore; PgR, progesteron receptor; ET, endocrine therapy; IBTR, ipsilateral breast tumor recurrence; SD, stable disease; PD, progressive disease; MPA, medroxyprogesterone acetate

Two biopsies were performed in 8 women, in which four women had primary and recurrent/metastatic samples. Four out of these 8 women acquired ESR1 mutation, whereas no ESR1 mutation could be identified at first biopsy.

Conclusions: We demonstrated the sensitive detection and accurate quantification of low frequency ESR1 mutations in 270 primary breast cancer samples and 55 recurrent/metastatic samples using ddPCR assay. This technique could prove a useful method for the precise detection of ESR1 mutations in endocrine therapy resistant cases.

Citation Format: Takeshita T, Yamamoto Y, Yamamoto-Ibusuki M, Inao T, Sueta A, Fujiwara S, Iwase H. Clinical significance of ESR1 mutations using droplet digital polymerase chain reaction assay in 325 breast cancer samples. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-07-07.

Abstract P4-09-01: FGFR1 protein expression is associated with prognosis in primary breast cancer: A comprehensive analysis of gene copy number, mRNA and protein expression

Background: The Cancer Genome Atlas (TCGA) showed that copy number gain/amplification of FGFR1 was around 10% in primary breast cancer. FGFR1 gene amplification in breast cancer has been reported in some studies, more likely seen in ER-positive subtype. Several preclinical and clinical studies demonstrated that FGFR1 was one of novel targets of therapy for metastatic breast cancer. Previous studies suggested that aberrant FGFR1 expression was associated with poor prognosis, while there was no report that compared copy number aberration, mRNA and protein expression. The aim of this study is to analyze FGFR1 gene copy number, expression levels of FGFR1 mRNA and FGFR1 protein in ER-positive/HER2-negative primary breast cancer, and to examine the relationship between FGFR1 status and clinicopathological parameters including prognosis.

Methods: The cohort of this study included 307 ER-positive/HER2-negative primary invasive breast cancer patients treated with standard care at Kumamoto University Hospital between June 2000 and January 2011. We performed a comprehensive analysis of FGFR1 at the levels of gene copy number, mRNA and FGFR1 protein expression analyzed by qPCR, qRT-PCR and immunohistochemistry, respectively.

Results: FGFR1 gain/amplification was identified in 43 (14.0%) out of 307 patients. FGFR1 gain/amplification had significantly associated with higher nuclear grade (p=0.010). No correlations between FGFR1 mRNA expression levels and any clinicopathological factors were found. Expression levels of FGFR1 protein was positively associated with invasive tumor size (p=0.039). Modest positive correlations between these three (FGFR1 gene gain/amplification, expression levels of FGFR1 mRNA and FGFR1 protein) were found. The univariate analysis revealed that high FGFR1 protein expression was significantly related to poor prognosis (p=0.0019, HR: 2.63, 95%CI: 1.17-5.98) in terms of relapse-free survival (RFS) but not breast cancer-specific survival. The univariate analysis did not show that any factors except FGFR1 protein expression were significantly associated with RFS in this cohort.

Conclusion: Expression levels of FGFR1 protein may be an independent prognostic factor in terms of RFS for ER-positive/HER2-negative breast cancer patients receiving standard care.

Citation Format: Tomiguchi M, Yamamoto Y, Yamamoto-Ibusuki M, Yamaguchi R, Fujiki Y, Fujiwara S, Sueta A, Takeshita T, Inao T, Iwase H. FGFR1 protein expression is associated with prognosis in primary breast cancer: A comprehensive analysis of gene copy number, mRNA and protein expression. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-09-01.

Interplay between Solo and keratin filaments is crucial for mechanical force-induced stress fiber reinforcement

Mechanical force-induced cytoskeletal reorganization is essential for cell and tissue remodeling and homeostasis; however, the underlying cellular mechanisms remain elusive. Solo (ARHGEF40) is a RhoA-targeting guanine nucleotide exchange factor (GEF) involved in cyclical stretch-induced human endothelial cell reorientation and convergent extension cell movement in zebrafish gastrula. In this study, we show that Solo binds to keratin-8/keratin-18 (K8/K18) intermediate filaments through multiple sites. Solo overexpression promotes the formation of thick actin stress fibers and keratin bundles, whereas knockdown of Solo, expression of a GEF-inactive mutant of Solo, or inhibition of ROCK suppresses stress fiber formation and leads to disorganized keratin networks, indicating that the Solo-RhoA-ROCK pathway serves to precisely organize keratin networks, as well as to promote stress fibers. Of importance, knockdown of Solo or K18 or overexpression of GEF-inactive or deletion mutants of Solo suppresses tensile force-induced stress fiber reinforcement. Furthermore, knockdown of Solo or K18 suppresses tensile force-induced RhoA activation. These results strongly suggest that the interplay between Solo and K8/K18 filaments plays a crucial role in tensile force-induced RhoA activation and consequent actin cytoskeletal reinforcement.

Rho guanine nucleotide exchange factors involved in cyclic-stretch-induced reorientation of vascular endothelial cells

Cyclic stretch is an artificial model of mechanical force loading, which induces the reorientation of vascular endothelial cells and their stress fibers in a direction perpendicular to the stretch axis. Rho family GTPases are crucial for cyclic-stretch-induced endothelial cell reorientation; however, the mechanism underlying stretch-induced activation of Rho family GTPases is unknown. A screen of short hairpin RNAs targeting 63 Rho guanine nucleotide exchange factors (Rho-GEFs) revealed that at least 11 Rho-GEFs – Abr, alsin, ARHGEF10, Bcr, GEF-H1 (also known as ARHGEF2), LARG (also known as ARHGEF12), p190RhoGEF (also known as ARHGEF28), PLEKHG1, P-REX2, Solo (also known as ARHGEF40) and α-PIX (also known as ARHGEF6) – which specifically or broadly target RhoA, Rac1 and/or Cdc42, are involved in cyclic-stretch-induced perpendicular reorientation of endothelial cells. Overexpression of Solo induced RhoA activation and F-actin accumulation at cell-cell and cell-substrate adhesion sites. Knockdown of Solo suppressed cyclic-stretch- or tensile-force-induced RhoA activation. Moreover, knockdown of Solo significantly reduced cyclic-stretch-induced perpendicular reorientation of endothelial cells when cells were cultured at high density, but not when they were cultured at low density or pretreated with EGTA or VE-cadherin-targeting small interfering RNAs. These results suggest that Solo is involved in cell-cell-adhesion-mediated mechanical signal transduction during cyclic-stretch-induced endothelial cell reorientation.