Longitudinal analysis of antibody profiles against plakins in severe drug eruptions: emphasis on correlation with tissue damage in drug-induced hypersensitivity syndrome and drug reaction with eosinophilia and systemic symptoms.

BACKGROUND: The evidence for severe drug eruption as a trigger for autoimmune disease has recently increased. No information is available on how tissue damage in severe drug eruptions can induce autoimmune responses. OBJECTIVES: To investigate whether the generation of autoantibodies (autoAbs) against plakin family proteins could be the cause or result of tissue damage in patients with severe drug eruptions and whether the generation of autoAbs could be prevented by systemic corticosteroids during the acute stage. METHODS: We retrospectively analysed alterations of serum levels of autoAbs against plakin family proteins in patients with Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN) and drug-induced hypersensitivity syndrome (DiHS)/drug reaction with eosinophilia and systemic symptoms (DRESS) during the acute stage and long after resolution over a period of more than 10 years. RESULTS: AutoAbs against plakin family proteins were detected in patients with either SJS/TEN or DiHS/DRESS regardless of the epidermal damage in the acute stage, and were sustained even long after resolution in DiHS/DRESS, indicating that those autoAbs are neither the cause nor the consequence of epidermal damage, at least in DiHS/DRESS. Severe liver damage and noncorticosteroid therapy during the early and acute stages of DiHS/DRESS were associated with the subsequent generation of these autoAbs. CONCLUSIONS: These autoAbs are neither necessarily the cause nor the result of epidermal damage in DiHS/DRESS, because the presence of these autoAbs was not restricted to patients with SJS/TEN but was also observed in those with DiHS/DRESS, which is characterized by lack of epidermal damage. Severe liver damage and/or immune responses that could be prevented by corticosteroids in the acute stage of DiHS/DRESS are among the causal factors contributing to the generation of autoimmune responses.

CD10 as a novel marker of therapeutic resistance and cancer stem cells in head and neck squamous cell carcinoma.

BACKGROUND: Cancer stem cells (CSCs) are responsible for treatment failure. However, their identification and roles in resistance are not well established in head and neck squamous cell carcinoma (HNSCC). METHODS: Three HNSCC cell lines (FaDu, Detroit562 and BICR6) were treated with cisplatin or radiation. Cell surface antigens were analysed by LyoPlate, a novel cell surface antigen array. The expression levels of antigens highly expressed after treatments were further compared between cisplatin-resistant Detroit562 cells and its parental line. Association of the candidate antigen with CSCs properties, namely sphere formation and in vivo tumourigenicity, was also examined. RESULTS: CD10, CD15s, CD146 and CD282 were upregulated across the treated cell lines, while the increased expression of CD10 was prominent in the cisplatin-resistant cell line. Isolation mediated by FACS revealed that the CD10-positive subpopulation was more refractory to cisplatin, fluorouracil and radiation than the CD10-negative subpopulation. It also showed an increased ability to form spheres in vitro and tumours in vivo. Moreover, the CD10-positive subpopulation expressed the CSC marker OCT3/4 at a higher level than that in the CD10-negative subpopulation. CONCLUSIONS: CD10 is associated with therapeutic resistance and CSC-like properties of HNSCC. CD10 may serve as a target molecule in the treatment of refractory HNSCC.

The dynamics of herpesvirus reactivations during and after severe drug eruptions: their relation to the clinical phenotype and therapeutic outcome.

BACKGROUND: Drug-induced hypersensitivity syndrome/drug rash with eosinophilia and systemic symptoms (DIHS/DRESS) and Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN) represent contrasting poles of severe drug eruptions, and sequential reactivations of several herpesviruses have exclusively been demonstrated in the former. No previous studies, however, were extended beyond the acute stage. We sought to investigate whether herpesvirus reactivations could also be observed in SJS/TEN and beyond the acute stage of both diseases. METHODS: Patients with SJS (n = 16), SJS/TEN overlap (n = 2), TEN (n = 10), and DIHS/DRESS (n = 34) were enrolled. We performed a retrospective analysis of Epstein-Barr virus (EBV), human herpesvirus 6 (HHV-6), and cytomegalovirus (CMV) DNA loads sequentially determined by real-time polymerase chain reaction during a 2-year period after onset. RESULTS: Persistently increased EBV loads were detected in SJS during the acute stage and long after resolution, but not in others. In contrast, high HHV-6 loads were exclusively detected in DIHS/DRESS during the acute stage. The dynamics of herpesvirus reactivation varied in DIHS/DRESS according to the use of systemic corticosteroids: While EBV loads were higher in patients not receiving systemic corticosteroids, CMV and HHV-6 loads were higher in those receiving them. CONCLUSIONS: Distinct patterns of herpesvirus reactivation according to the pathological phenotype and to the use of systemic corticosteroids were observed during the acute stage and follow-up period, which may contribute, at least in part, to the difference in the clinical manifestations and long-term outcomes. Systemic corticosteroids during the acute stage may improve the outcomes in DIHS/DRESS.

The NADH-ubiquinone oxidoreductase 1 alpha subcomplex 5 (NDUFA5) gene variants are associated with autism.

OBJECTIVE: Autism appears to have a strong genetic component. The product of the NADH-ubiquinone oxidoreductase 1 alpha subcomplex 5 (NDUFA5) gene is included in the mitochondrial electron transport chain. METHOD: We performed a case-control study of 235 patients with autism and 214 controls and examined three single-nucleotide polymorphisms (SNPs) within this gene in a Japanese population. We then conducted a transmission disequilibrium test (TDT) analysis in 148 autistic trios. RESULTS: In the case-control study, two SNPs (rs12666974 and rs3779262) showed a significant association with autism (P=0.00064 and 0.00046 respectively). Furthermore, a haplotype containing these two SNPs showed a significant association (P-global=0.0013, individual haplotype A-A: P=0.010). In TDT analysis, the global and A-A haplotype P-values also indicated significant associations. Minor allele and genotype frequencies were decreased in the autistic subjects. CONCLUSION: We found significant association between the NDFA5 gene and autism.

Differences in immunological alterations and underlying viral infections in two well-defined severe drug eruptions.

BACKGROUND: Similar drugs (e.g. anticonvulsants) have been implicated in the development of two distinct forms of severe cutaneous drug reactions, Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN) and drug-induced hypersensitivity syndrome (DIHS)/drug rash with eosinophilia and systemic symptoms (DRESS). AIM: To investigate immunological alterations and underlying viral infections that could contribute to the variability in the clinical presentations of these diseases. METHODS: We retrospectively analysed clinical variables, serum immunoglobulin levels, numbers of circulating white blood cells, lymphocytes and their subsets, serum levels of several cytokines, and underlying viral infections in both drug reactions, using samples obtained at onset from 9 patients with SJS/TEN and 19 patients with DIHS/DRESS. RESULTS: There were significant differences between the two drug eruptions in the duration of drug intake before onset, the levels of IgG, IgA and IgM, the numbers of circulating white blood cell, lymphocyte, CD3+ T cell and CD8+ T cells, the serum levels of interferon-γ, and the titres of anti-herpes simplex virus IgG at onset. CONCLUSIONS: The difference in the pattern of immune responses shaped in part by previous and underlying viral infections at the time of drug exposure could cause a marked deviation in the pathological phenotype of severe drug eruptions. Elucidating these host factors may provide a basis for therapeutic approaches in patients with severe drug reactions.

Laparoscopic proximal gastrectomy with double-flap technique versus laparoscopic subtotal gastrectomy for proximal early gastric cancer.

BACKGROUND: Laparoscopic proximal gastrectomy with double-flap technique (LPG-DFT) and laparoscopic subtotal gastrectomy (LSTG) may replace laparoscopic total gastrectomy (LTG) for proximal early gastric cancer. The aim of this study was to evaluate short- and long-term outcomes after LPG-DFT and LSTG. METHODS: Patients who underwent LPG-DFT or LSTG at the Cancer Institute Hospital in Tokyo between January 2006 and April 2015 were included in this retrospective study. Operative procedures were selected based on the distance from the cardia to the proximal boundary of the tumour, tumour location and predicted remnant stomach volume. Patient characteristics, surgical data, markers of postoperative nutritional status, such as blood chemistry and bodyweight loss, and endoscopic findings were compared between procedures. The main study outcome was nutritional status. RESULTS: A total of 161 patients (LPG-DFT 51, LSTG 110) were included. Types of postoperative complication occurring more than 30 days after surgery differed between the two procedures. Remnant stomach ulcers, including anastomotic ulcers, were observed only after LPG-DFT, whereas complications involving the small intestine, such as internal hernia or small bowel obstruction, occurred more frequently after LSTG. Values for total protein, albumin, prealbumin and bodyweight loss were comparable between the two procedures at 36 months after surgery. Haemoglobin concentrations were higher after LPG-DFT than after LSTG at 24 months (13·4 versus 12·8 g/dl respectively; P = 0·045) and 36 months (13·5 versus 12·8 g/dl; P = 0·007) after surgery. The rate of Los Angeles grade B or more severe reflux oesophagitis was comparable. CONCLUSION: LPG-DFT and LSTG for proximal early gastric cancer have similar outcomes, but different types of complication.

ANTECEDENTES: La gastrectomía proximal laparoscópica con técnica de doble derivación (double flap technique, LPG-DFT) y la gastrectomía subtotal laparoscópica (laparoscopic subtotal gastrectomy, LsTG) pueden sustituir a la gastrectomía total laparoscópica (laparoscopic total gastrectomy, LTG) para el cáncer gástrico precoz (early gastric cancer, EGC) proximal. El objetivo de este estudio fue evaluar los resultados a corto y a largo plazo tras LPG-DFT y LsTG. MÉTODOS: En este estudio retrospectivo se incluyeron pacientes que fueron sometidos a LPG-DFT o LsTG en el Hospital del Instituto del Cáncer de Tokio entre enero 2006 y abril 2015. Las técnicas quirúrgicas se seleccionaron en base a la distancia entre el cardias y el borde proximal del tumor, localización del tumor, y el volumen previsto del remanente gástrico. Las características de los pacientes, datos quirúrgicos, marcadores del estado nutricional postoperatorio, tales como la bioquímica sanguínea y la pérdida de peso corporal (body weight loss, BWL), y los hallazgos endoscópicos se compararon entre las técnicas. El resultado principal del estudio fue el estado nutricional. RESULTADOS: Se incluyeron un total de 161 pacientes (LPG-DFT 51, LsTG 110). Los tipos de complicaciones postoperatorias que aparecieron a más de 30 días después de la cirugía variaron entre ambas técnicas. Las úlceras en el remanente gástrico, incluyendo úlceras anastomóticas, solo se observaron tras una LPG-DFT, mientras las complicaciones relacionadas con el intestino delgado, como la hernia interna o la obstrucción de intestino delgado, sucedió con más frecuencia tras una LsTG. Los valores de proteínas totales, albúmina, prealbúmina, y BWL fueron comparables entre ambas técnicas a los 36 meses después de la cirugía. Las concentraciones de hemoglobina fueron más altas tras una LPG-DFT que tras una LsTG a los 24 (13,4 versus 12,8 mg/dL, P = 0,045) y 36 meses (13,5 versus 12,8 mg/mL, P = 0,007) después de la cirugía. Las incidencias de esofagitis por reflujo grado B Los Angeles o más grave fueron comparables. CONCLUSIÓN: La LPG-DFT y la LsTG para el EGC proximal presentan resultados bastante similares, pero difieren en el tipo de complicaciones.

Prevention of neural tube defects by loss of function of inducible nitric oxide synthase in fetuses of a mouse model of streptozotocin-induced diabetes.

AIMS/HYPOTHESIS: Maternal diabetes during pregnancy increases the risk of congenital malformations such as neural tube defects (NTDs). Although the mechanism of this effect is uncertain, it is known that levels of nitric oxide synthase (NOS) and nitric oxide are elevated in embryos of a mouse model of diabetes. We postulated that overproduction of nitric oxide causes diabetes-induced congenital malformations and that inhibition of inducible NOS (iNOS) might prevent diabetic embryopathy. METHODS: Mice were rendered hyperglycaemic by intraperitoneal injection of streptozotocin. The incidence of congenital malformations including NTDs was evaluated on gestational day 18.5. We assessed the involvement of iNOS in diabetes-induced malformation by administering ONO-1714, a specific inhibitor of iNOS, to pregnant mice with streptozotocin-induced diabetic mice and by screening mice with iNOS deficiency due to genetic knockout (iNos(-/-)). RESULTS: ONO-1714 markedly reduced the incidence of congenital anomalies, including NTDs, in fetuses of a mouse model of diabetes. It also prevented apoptosis in the head region of fetuses, indicating that iNOS is involved in diabetes-related congenital malformations. Indeed, no NTDs were observed in fetuses of diabetic iNos(-/-) mice and the incidence of other malformations was also markedly reduced. CONCLUSIONS/INTERPRETATION: We conclude that increased iNOS activity during organogenesis plays a crucial role in the pathogenesis of diabetes-induced malformations and suggest that inhibitors of iNOS might help prevent malformations, especially NTDs, in diabetic pregnancy.

Rho-kinase--mediated contraction of isolated stress fibers.

It is widely accepted that actin filaments and the conventional double-headed myosin interact to generate force for many types of nonmuscle cell motility, and that this interaction occurs when the myosin regulatory light chain (MLC) is phosphorylated by MLC kinase (MLCK) together with calmodulin and Ca(2+). However, recent studies indicate that Rho-kinase is also involved in regulating the smooth muscle and nonmuscle cell contractility. We have recently isolated reactivatable stress fibers from cultured cells and established them as a model system for actomyosin-based contraction in nonmuscle cells. Here, using isolated stress fibers, we show that Rho-kinase mediates MLC phosphorylation and their contraction in the absence of Ca(2+). More rapid and extensive stress fiber contraction was induced by MLCK than was by Rho-kinase. When the activity of Rho-kinase but not MLCK was inhibited, cells not only lost their stress fibers and focal adhesions but also appeared to lose cytoplasmic tension. Our study suggests that actomyosin-based nonmuscle contractility is regulated by two kinase systems: the Ca(2+)-dependent MLCK and the Rho-kinase systems. We propose that Ca(2+) is used to generate rapid contraction, whereas Rho-kinase plays a major role in maintaining sustained contraction in cells.

Systemic lupus erythematosus presenting with Kikuchi-Fujimoto's disease as a long-term sequela of drug-induced hypersensitivity syndrome. A possible role of Epstein-Barr virus reactivation.

Drug-induced hypersensitivity syndrome (DIHS) is a severe form of drug eruptions associated with viral reactivations. Autoimmune diseases have been reported to develop several months or years after the resolution of DIHS. We describe a 36-year-old man with cervical lymphadenopathy and an erythematous eruption affecting the face and neck, which evolved into clinically evident systemic lupus erythematosus. He had had an episode of DIHS 4 years previously, in which human herpesvirus-6 and Epstein-Barr virus (EBV) were reactivated. Expression of EBV-encoded RNA was detected in the lymph node. On the basis of findings in this patient, we suggest that EBV is pathogenically important in the sequence of events leading to the onset of systemic lupus erythematosus and that patients with a history of DIHS may be at a risk of eventually developing autoimmune diseases.

Divergent cytotoxic effects of PKC412 in combination with conventional antileukemic agents in FLT3 mutation-positive versus -negative leukemia cell lines.

FMS-like tyrosine kinase-3 (FLT3) is a new therapeutic target for acute myelocytic leukemia (AML), because FLT3 mutations are the most common genetic alterations in AML and are directly related to leukemogenesis. We studied cytotoxic interactions of a FLT3 inhibitor, PKC412, with eight conventional antileukemic agents (cytarabine, doxorubicin, idarubicin, mitoxantrone, etoposide, 4-hydroperoxy-cyclophosphamide, methotrexate and vincristine) using three leukemia cell lines carrying FLT3 mutations (MOLM13, MOLM14 and MV4-11) and five leukemia cell lines without FLT3 mutations (KOPB-26, THP-1, BALL-1, KG-1 and U937). PKC412 showed synergistic effects with all agents studied except methotrexate for FLT3-mutated cell lines in isobologram analysis. In contrast, PKC412 was rather antagonistic to most drugs, except for 4-hydroperoxy-cyclophosphamide and vincristine, in leukemia cell lines without FLT3 mutations. Cell-cycle analysis revealed that PKC412 induced G1 arrest in leukemia cell lines carrying FLT3 mutations, whereas it arrested cells in G2/M phase in the absence of FLT3 mutations, which may underlie the divergent cytotoxic interactions. These results suggest that the simultaneous administration of PKC412 and other agents except methotrexate is clinically effective against FLT3 mutation-positive leukemias, whereas it would be of little benefit for FLT3 mutation-negative leukemias. Our findings may be of help for the design of PKC412-based combination chemotherapy.

The Relation between Asthma Control and Quality of Life in Children.

BACKGROUND: Asthma is a common chronic illness worldwide. Asthmatic children are forced to alter their way of living to avoid its complications or exacerbations, which negatively affects their psychological and social well-being. High prevalence of behavioral and emotional difficulties was noticed among children with asthma. METHODS: Cross-sectional study that was conducted over 8 months involving asthmatic children within the ages of 7-17 years presenting to two governmental hospitals in Jeddah, Saudi Arabia. Three questionnaires were used: asthma control test, the strengths and difficulties questionnaire, and the pediatrics asthma quality of life questionnaire. Using SPSS, Pearson's chi-square and independent sample t-tests were used to find associations. RESULTS: Among the 106 respondents, 84% of the sample had poor asthma control. Significantly poorer quality of life was observed in children with uncontrolled asthma (p = <0.001). Children with controlled and uncontrolled asthma were equally affected psychosocially with no relation between asthma control and their psychosocial well-being (p = 0.58). CONCLUSION: The majority of asthmatic children were uncontrolled with poor quality of life. This study recommends that the psychosocial well-being should be assessed during clinic visits for a better holistic approach and effective improvement of outcome. Further researches are needed to study the psychological effect of asthma.

Azathioprine-induced Agranulocytosis and Severe Alopecia After Kidney Transplantation Associated With a NUDT15 Polymorphism: A Case Report.

BACKGROUND: Azathioprine (AZA) is the drug recommended for the continuation of immunosuppressive treatment after renal transplant in women during pregnancy. CASE REPORT: A 37-year-old Japanese female developed agranulocytosis and severe alopecia after initiation of AZA (50 mg), used as an alternative to mycophenolate mofetil (MMF, 1000 mg) therapy in anticipation of a planned pregnancy. Within 4 days of the initiation of AZA therapy, the patient developed a high fever, leucopenia, and cranial alopecia. Genetic testing revealed a homozygous polymorphism of NUDT15 (rs116855232, NM_018283.3:c.415C>T: p.Arg139Cys), which has previously been identified as a risk factor for AZA-related complications in patients with inflammatory bowel disease. CONCLUSION: Genetic screening for NUDT15 could contribute to the prevention of serious adverse reactions to AZA and provide the opportunity for personalized medicine. Identification of a safe alternative to MMF during pregnancy after a renal transplant is a problem to be resolved in the future.

Effect of Systematic Conversion to Generic Mycophenolate Mofetil (MMF) in Kidney Transplantation: A Single-Center Clinical Experience from Japan.

INTRODUCTION: Recently, more and more generic drugs have been used for immunosuppressive drugs in the field of organ transplantation. Some reports have indicated that blood concentration of most generic drugs is difficult to maintain stability, and it may cause the difference in graft survival of transplanted organs between original drugs and generic drugs. In this article, we report the cases could not maintain blood concentration of generic drugs of mycophenolate mofetil (MMF). RESULTS: In 4 cases out of 5 cases that we had to change original MMF to generic MMF, there were cases that blood concentration level was not stabilized. There were possibility that the lowered blood concentration level of MMF caused a rejection, in two cases. Mean MMF trough level was decreased from 3.6 ± 1.9 µg/mL to 0.6 ± 0.4 µg/mL. Due to the early detection, it did not become severe or failure of graft function, however, we cannot deny the possibilities that side effects were increased and rejection rose. In these cases, we discontinued to use the generic drugs thereafter due to unstable plasma concentration of MMF. DISCUSSION: Some reports have indicated that failure to maintain plasma concentration of MMF leads to rejection. Therefore, maintenance of effective plasma concentration and prevention of rejection are essential to long-term graft survival in kidney transplant. CONCLUSION: Generic drug formulations may exhibit differences in effects and absorption compared to the brand-name drug. If the generic drug should be used, patients should be closely monitored.

Histone deacetylase inhibitor FK228 suppresses the Ras-MAP kinase signaling pathway by upregulating Rap1 and induces apoptosis in malignant melanoma.

Histone deacetylase (HDAC) inhibitors are expected to be effective for refractory cancer because their mechanism of action differs from that of conventional antineoplastic agents. In this study, we examined the effect of the HDAC inhibitor FK228 on malignant melanoma, as well as its molecular mechanisms. FK228 was highly effective against melanoma compared with other commonly used drugs. By comparing the gene expression profiles of melanoma cells and normal melanocytes, we defined a subset of genes specifically upregulated in melanoma cells by FK228, which included Rap1, a small GTP-binding protein of the Ras family. The expression of Rap1 mRNA and protein increased in FK228-treated melanoma cells in both a dose- and a time-dependent manner. A decrease in the phosphorylation of c-Raf, MEK1/2, and ERK1/2 was accompanied by an increase in Rap1 expression in both FK228-treated and Rap1-overexpressing cells. Inhibition of Rap1 upregulation by small interfering RNA (siRNA) abrogated the induction of apoptosis and suppression of ERK1/2 phosphorylation in FK228-treated melanoma cells. These results indicate that the cytotoxic effects of FK228 are mediated via the upregulation of Rap1. Furthermore, we found that Rap1 was overexpressed and formed a complex with B-Raf in melanoma cell lines with a V599E mutation of B-Raf. The siRNA-mediated abrogation of Rap1 overexpression increased the viability of these cells, suggesting that Rap1 is also an endogenous regulator of Ras-MAP kinase signaling in melanomas.

Osmotic shock-induced neurite extension via activation of p38 mitogen-activated protein kinase and CREB.

Although it is known that sustained activation of classical mitogen-induced protein kinase (MAPK, also known as ERK) induced by nerve growth factor (NGF) plays an important role in the induction of neurite outgrowth, the role of p38 MAPK in neural cell function is still not clear. We developed two neuronal cell lines from PC12 cells, PC12m3 and PC12m32, in which NGF-induced neurite outgrowth is impaired and that show neurite outgrowth in response to hyperosmotic shock. The frequencies of neurite outgrowth of PC12m3 and PC12m32 cells induced by osmotic shock were approximately 10- and 12-fold greater, respectively, than that in PC12 parental cells. The p38 MAPK pathway inhibitor SB203580 but not the ERK pathway blocker U0126 inhibited the ability of PC12m3 and PC12m32 cells to induce neurite outgrowth in response to osmotic shock. Furthermore, expression of a nonactivable form of p38 but not that of wild-type p38 significantly blocked neurite outgrowth induced by osmotic shock. The extent of phosphorylation of p38 MAPK induced by osmotic shock in PC12m32 cells was much greater than that in PC12 parental cells. The upstream kinases MKK3 and MKK6, which phosphorylate and activate p38 MAPK, also showed higher levels in PC12m32 cells than in PC12 parental cells when treated with osmotic shock. Inhibition of p38 MAPK by SB203580 resulted in inhibition of the activity of the transcription factor CREB, which is activated by osmotic shock. These findings indicate that activation of CREB mediated by a p38 pathway distinct from the NGF signaling pathway may be required for neurite outgrowth.

Isolation and contraction of the stress fiber.

Stress fibers were isolated from cultured human foreskin fibroblasts and bovine endothelial cells, and their contraction was demonstrated in vitro. Cells in culture dishes were first treated with a low-ionic-strength extraction solution and then further extracted using detergents. With gentle washes by pipetting, the nucleus and the apical part of cells were removed. The material on the culture dish was scraped, and the freed material was forced through a hypodermic needle and fractionated by sucrose gradient centrifugation. Isolated, free-floating stress fibers stained brightly with fluorescently labeled phalloidin. When stained with anti-alpha-actinin or anti-myosin, isolated stress fibers showed banded staining patterns. By electron microscopy, they consisted of bundles of microfilaments, and electron-dense areas were associated with them in a semiperiodic manner. By negative staining, isolated stress fibers often exhibited gentle twisting of microfilament bundles. Focal adhesion-associated proteins were also detected in the isolated stress fiber by both immunocytochemical and biochemical means. In the presence of Mg-ATP, isolated stress fibers shortened, on the average, to 23% of the initial length. The maximum velocity of shortening was several micrometers per second. Polystyrene beads on shortening isolated stress fibers rotated, indicating spiral contraction of stress fibers. Myosin regulatory light chain phosphorylation was detected in contracting stress fibers, and a myosin light chain kinase inhibitor, KT5926, inhibited isolated stress fiber contraction. Our study demonstrates that stress fibers can be isolated with no apparent loss of morphological features and that they are truly contractile organelle.