Phosphorylation and dephosphorylation of Ser852 and Ser889 control the clustering, localization and function of PAR3.

Cell polarity is essential for various asymmetric cellular events, and the partitioning defective (PAR) protein PAR3 (encoded by PARD3 in mammals) plays a unique role as a cellular landmark to establish polarity. In epithelial cells, PAR3 localizes at the subapical border, such as the tight junction in vertebrates, and functions as an apical determinant. Although we know a great deal about the regulators of PAR3 localization, how PAR3 is concentrated and localized to a specific membrane domain remains an important question to be clarified. In this study, we demonstrate that ASPP2 (also known as TP53BP2), which controls PAR3 localization, links PAR3 and protein phosphatase 1 (PP1). The ASPP2-PP1 complex dephosphorylates a novel phosphorylation site, Ser852, of PAR3. Furthermore, Ser852- or Ser889-unphosphorylatable PAR3 mutants form protein clusters, and ectopically localize to the lateral membrane. Concomitance of clustering and ectopic localization suggests that PAR3 localization is a consequence of local clustering. We also demonstrate that unphosphorylatable forms of PAR3 exhibited a low molecular turnover and failed to coordinate rapid reconstruction of the tight junction, supporting that both the phosphorylated and dephosphorylated states are essential for the functional integrity of PAR3.

The novel PAR-1-binding protein MTCL1 has crucial roles in organizing microtubules in polarizing epithelial cells.

The establishment of epithelial polarity is tightly linked to the dramatic reorganization of microtubules (MTs) from a radial array to a vertical alignment of non-centrosomal MT bundles along the lateral membrane, and a meshwork under the apical and basal membranes. However, little is known about the underlying molecular mechanism of this polarity-dependent MT remodeling. The evolutionarily conserved cell polarity-regulating kinase PAR-1 (known as MARK in mammals), whose activity is essential for maintaining the dynamic state of MTs, has indispensable roles in promoting this process. Here, we identify a novel PAR-1-binding protein, which we call microtubule crosslinking factor 1 (MTCL1), that crosslinks MTs through its N-terminal MT-binding region and subsequent coiled-coil motifs. MTCL1 colocalized with the apicobasal MT bundles in epithelial cells, and its knockdown impaired the development of these MT bundles and the epithelial-cell-specific columnar shape. Rescue experiments revealed that the N-terminal MT-binding region was indispensable for restoring these defects of the knockdown cells. MT regrowth assays indicated that MTCL1 was not required for the initial radial growth of MTs from the apical centrosome but was essential for the accumulation of non-centrosomal MTs to the sublateral regions. Interestingly, MTCL1 recruited a subpopulation of PAR-1b (known as MARK2 in mammals) to the apicobasal MT bundles, and its interaction with PAR-1b was required for MTCL1-dependent development of the apicobasal MT bundles. These results suggest that MTCL1 mediates the epithelial-cell-specific reorganization of non-centrosomal MTs through its MT-crosslinking activity, and cooperates with PAR-1b to maintain the correct temporal balance between dynamic and stable MTs within the apicobasal MT bundles.

Development of a novel emergency hemostatic kit for severe hemorrhage.

Photocrosslinkable chitosan (Az-CH-LA) contains lactose moieties and photoreactive azide groups, and its viscous solution forms an insoluble hydrogel on exposure to UV irradiation. We previously developed an emergency hemostatic kit using the Az-CH-LA solution, calcium alginate, and a UV irradiation apparatus. However, a suitable UV irradiation apparatus is required to effectively convert the Az-CH-LA solution into a hydrogel, and power supply to use the UV irradiation apparatus may not always be available in a disaster area or battlefield. To address this problem, we produced a portable, battery-powered UV irradiation apparatus constituting a novel hemostatic kit for severe hemorrhage. When the hemostatic kit using the UV irradiation apparatus was examined using a rat model of severe hemorrhage, the survival rate increased up to 73%. Hematological values as markers of hemorrhage did not change significantly over the first 3 days. In this study, we describe the characteristics of a portable UV irradiation apparatus and its use in an emergency hemostatic kit prepared using Az-CH-LA and calcium alginate for severe hemorrhage.

The 8th and 9th tandem spectrin-like repeats of utrophin cooperatively form a functional unit to interact with polarity-regulating kinase PAR-1b.

Utrophin is a widely expressed paralogue of dystrophin, the protein responsible for Duchenne muscular dystrophy. Utrophin is a large spectrin-like protein whose C-terminal domain mediates anchorage to a laminin receptor, dystroglycan (DG). The rod domain, composed of 22 spectrin-like repeats, connects the N-terminal actin-binding domain and the C-terminal DG binding domain, and thus mediates molecular linkage between intracellular F-actin and extracellular basement membrane. Previously, we demonstrated that a cell polarity-regulating kinase, PAR-1b, interacts with the utrophin-DG complex, and positively regulates the interaction between utrophin and DG. In this study, we demonstrate that the 8th and 9th spectrin-like repeats (R8 and R9) of utrophin cooperatively form a PAR-1b-interacting domain, and that Ser1258 within R9 is specifically phosphorylated by PAR-1b. Substitution of Ser1258 to alanine reduces the interaction between utrophin and DG, suggesting that the Ser1258 phosphorylation contributes to the stabilization of the utrophin-DG complex. Interestingly, PAR-1b also binds and phosphorylates R8-9 of dystrophin, and colocalizes with dystrophin at the skeletal muscle membrane. These results reveal a novel function of the rod domain of utrophin beyond that of a passive structural linker connecting the N- and C-terminal domain.

Intracellular polarity protein PAR-1 regulates extracellular laminin assembly by regulating the dystroglycan complex.

Cell polarity depends on extrinsic spatial cues and intrinsic polarity proteins including PAR-aPKC proteins. In mammalian epithelial cells, cell-cell contacts provide spatial cues that activate the aPKC-PAR-3-PAR-6 complex to establish the landmark of the initial cellular asymmetry. PAR-1, a downstream target of the aPKC-PAR-3-PAR-6 complex, mediates further development of the apical and basolateral membrane domains. However, the relationships between the PAR-aPKC proteins and other extrinsic spatial cues provided by the extracellular matrix (ECM) remain unclear. Here, we show that PAR-1 colocalizes with laminin receptors and is required for the assembly of extracellular laminin on the basal surface of epithelial cells. Furthermore, PAR-1 regulates the basolateral localization of the dystroglycan (DG) complex, one of the laminin receptors essential for basement membrane formation. We also show that PAR-1 interacts with the DG complex and is required for the formation of a functional DG complex. These results reveal the presence of a novel inside-out pathway in which an intracellular polarity protein regulates the ECM organization required for epithelial cell polarity and tissue morphogenesis.

aPKC acts upstream of PAR-1b in both the establishment and maintenance of mammalian epithelial polarity.

BACKGROUND: aPKC and PAR-1 are required for cell polarity in various contexts. In mammalian epithelial cells, aPKC localizes at tight junctions (TJs) and plays an indispensable role in the development of asymmetric intercellular junctions essential for the establishment and maintenance of apicobasal polarity. On the other hand, one of the mammalian PAR-1 kinases, PAR-1b/EMK1/MARK2, localizes to the lateral membrane in a complimentary manner with aPKC, but little is known about its role in apicobasal polarity of epithelial cells as well as its functional relationship with aPKC. RESULTS: We demonstrate that PAR-1b is essential for the asymmetric development of membrane domains of polarized MDCK cells. Nonetheless, it is not required for the junctional localization of aPKC nor the formation of TJs, suggesting that PAR-1b works downstream of aPKC during epithelial cell polarization. On the other hand, aPKC phosphorylates threonine 595 of PAR-1b and enhances its binding with 14-3-3/PAR-5. In polarized MDCK cells, T595 phosphorylation and 14-3-3 binding are observed only in the soluble form of PAR-1b, and okadaic acid treatment induces T595-dependent dissociation of PAR-1b from the lateral membrane. Furthermore, T595A mutation induces not only PAR-1b leakage into the apical membrane, but also abnormal development of membrane domains. These results suggest that in polarized epithelial cells, aPKC phosphorylates PAR-1b at TJs, and in cooperation with 14-3-3, promotes the dissociation of PAR-1b from the lateral membrane to regulate PAR-1b activity for the membrane domain development. CONCLUSIONS: These results suggest that mammalian aPKC functions upstream of PAR-1b in both the establishment and maintenance of epithelial cell polarity.

Phase II study of weekly irinotecan and cisplatin for refractory or recurrent non-small cell lung cancer.

Even with the standard first-line chemotherapy, advanced non-small cell lung cancer (NSCLC) recurs in most cases. The purpose of this study is to develop a new chemotherapeutic regimen for patients with NSCLC that has relapsed or was refractory to previous chemotherapy. Patients with proven NSCLC refractory or recurrent after previous single-regimen chemotherapy, PS of 0-2, age of 15 years or older, adequate organ functions and measurable lesions were treated with irinotecan at 60 mg/m(2) and cisplatin at 25 mg/m(2) with 1000 ml hydration on day 1. This administration, considered as one cycle, was repeated every week without rest unless encountering defined skip and dose-reduction criteria. The treatment was administered for six cycles over a 49-day period, both median values, to 48 patients, with a response rate of 26%, progression free and median survival times of 3 and 11 months, respectively, and a 1-year survival rate of 46%. The most frequent grade 3 or 4 toxicities were neutropenia, anaemia and nausea, which were manageable. Subset analyses suggested that the response rate was independent of response to the first-line chemotherapy. In conclusion, second-line chemotherapy of weekly irinotecan and cisplatin with minimum hydration seemed effective, with tolerable toxicity, and is potentially useful irrespective of the outcome of previous chemotherapy.

Effect of treatment schedule on the interaction of Cisplatin and radiation in human lung cancer cells.

This study was designed to determine the effects of the treatment schedule on the interaction between cisplatin and radiation. Cells of a human squamous cell lung cancer cell line were treated with cisplatin and radiation using three treatment protocols: 1-h exposure to cisplatin immediately followed by irradiation (A), 4-day continuous exposure to cisplatin immediately followed by irradiation (B), and 1-h exposure to cisplatin followed by irradiation after a 4-day interval (C). The interactions were assessed by isobologram, cell cycle distribution and apoptosis. The combination resulted in a additive effect in every protocol. Cell cycle accumulation at G(2)/M phase before irradiation was observed in Protocols B and C, whereas no cell cycle shift in the limited time course was noted in Protocol A. Although a 4-day continuous exposure to cisplatin and a 1-h exposure to cisplatin followed by a 4-day interval before irradiation caused significantly increased apoptosis, an additional increase in apoptosis after irradiation was not observed in Protocols B and C, whereas Protocol A showed an additional increase. Despite a cell cycle shift favoring radiation sensitivity, the drug-radiation interactions in Protocols B and C were additive, possibly because of negative effects including induction of a durable G(2)/M-phase arrest and suppression of apoptosis by cisplatin.

Altered gene expression by cisplatin in a human squamous cell lung carcinoma cell line.

BACKGROUND: Substantial evidence has disclosed that some cytotoxic agents have complex activities in influencing signal transduction pathways in cells. MATERIALS AND METHODS: cDNA microarray analysis was performed after exposing a human squamous cell carcinoma cell line, RERF-LC-AI, to low-dose cisplatin for 5 days. Up-regulated gene expressions were suppressed by small interfering RNA to investigate phenotypic alteration of the cells. RESULTS: Among 30,000 genes screened, 42 genes showed increases or decreases in expression of more than 2-fold with cisplatin treatment. They included genes with functions involved in apoptosis, cell cycle regulation and DNA metabolism/repair. Suppression of the 5 most significantly altered genes by small interfering RNA resulted in partly reduced apoptosis without altering cytotoxicity of cisplatin. CONCLUSION: Besides direct cytotoxic effects on cells, cisplatin may have indirect effects involving drug resistance, and synergistic effects with other agents.

MTCL1 crosslinks and stabilizes non-centrosomal microtubules on the Golgi membrane.

Recent studies have revealed the presence of a microtubule subpopulation called Golgi-derived microtubules that support Golgi ribbon formation, which is required for maintaining polarized cell migration. CLASPs and AKAP450/CG-NAP are involved in their formation, but the underlying molecular mechanisms remain unclear. Here, we find that the microtubule-crosslinking protein, MTCL1, is recruited to the Golgi membranes through interactions with CLASPs and AKAP450/CG-NAP, and promotes microtubule growth from the Golgi membrane. Correspondingly, MTCL1 knockdown specifically impairs the formation of the stable perinuclear microtubule network to which the Golgi ribbon tethers and extends. Rescue experiments demonstrate that besides its crosslinking activity mediated by the N-terminal microtubule-binding region, the C-terminal microtubule-binding region plays essential roles in these MTCL1 functions through a novel microtubule-stabilizing activity. These results suggest that MTCL1 cooperates with CLASPs and AKAP450/CG-NAP in the formation of the Golgi-derived microtubules, and mediates their development into a stable microtubule network.

Angiogenesis following cell injection is induced by an excess inflammatory response coordinated by bone marrow cells.

The aim of this study was to identify novel angiogenic mechanisms underlying the regenerative process. To that end, interactions between adipose tissue-derived stromal cells (ASCs) and bone marrow cells (BMCs) were initially investigated using real-time fluorescence optical imaging. To monitor cell behavior in mice, we injected green fluorescent protein-positive (GFP(+)) BMCs into the tail vein and injected PKH26-labeled ASCs behind the ears. Angiogenesis and inflammation were observed at these sites via an optical imaging probe. Injected GFP(+) BMCs migrated from the blood vessels into the tissues surrounding the ASC injection sites. Many of the migrating GFP(+) BMCs discovered at the ASC injection sites were inflammatory cells, including Gr-1(+), CD11b(+), and F4/80(+) cells. ASCs cocultured with inflammatory cells secreted increased levels of chemokines such as macrophage inflammatory protein (MIP)-1α, MIP-1ß, keratinocyte-derived chemokines, and monocyte chemotactic protein 1. Similarly, these ASCs secreted increased levels of angiogenic growth factors such as hepatocyte growth factor and vascular endothelial growth factor. However, when anti-CXC chemokine receptor type 4 antibody was injected at regular intervals, the migration of GFP(+) BMCs (especially Gr-1(+) and CD11b(+) cells) to ASC injection sites was inhibited, as was angiogenesis. The collective influence of the injected ASCs and BMC-derived inflammatory cells promoted acute inflammation and angiogenesis. Together, the results suggest that the outcome of cell-based angiogenic therapy is influenced not only by the injected cells but also by the effect of intrinsic inflammatory cells.

Expansion and characterization of human bone marrow-derived mesenchymal stem cells cultured on fragmin/protamine microparticle-coated matrix with fibroblast growth factor-2 in low serum medium.

Fragmin/protamine microparticles (F/P MPs) can be stably coated onto plastic surfaces. A capability of F/P MP-coated plates was investigated to immobilize fibroblast growth factor (FGF)-2 as a substratum to expand human bone marrow-derived mesenchymal stem cells (BMMSCs). FGF-2 molecules in low (2%) human serum (HS) medium were immobilized onto F/P MP-coated plates, and the FGF-2 was gradually released into the medium with a half-releasing time of 4-5 days. BMMSCs adhered well to the F/P MP-coated plates, and grew at a doubling time of about 28 h in low (2%) HS medium with FGF-2 (5 ng/mL), while the cells grew at a doubling time of about 30 and 38 h in high (10%) HS medium and in low (2%) HS medium with FGF-2, respectively, without F/P MP coating. The expanded BMMSCs on the F/P MP-coated plates in low (2%) HS medium with FGF-2 maintained their multilineage potential for differentiation into adipocytes and osteoblasts.

Expansion and characterization of adipose tissue-derived stromal cells cultured with low serum medium.

Adipose tissue contains a population of cells that have extensive self-renewal capacity and the ability to differentiate along multiple lineages. In addition, adipose tissue-derived stromal cells (ATSCs) are able to differentiate into various cell types that may be useful for autologous cell transplantation for defects of bone, cartilage, adipose, and tendon, etc. Most protocols for in vitro cultures of ATSCs include fetal bovine serum (FBS) as a nutritional supplement. However, in some cell cultures, it involves multiple doses of FBS, which raises a concern over possible infections as well as immunological reactions that are caused by medium-derived FBS proteins, sialic acid, etc. In this study, we were able to expand mouse ATSCs using low mouse serum media containing collagen type I, heparin-carrying polystyrene, and fibroblast growth factor (FGF)-2. These expanded mouse ATSCs maintained their multilineage potential for differentiation into adipocytes, osteoblasts, and chondrocytes. Therefore, this method, which uses autologous cells and low serum media, may be able to be utilized for clinical cell therapies.

Effect of controlled release of fibroblast growth factor-2 from chitosan/fucoidan micro complex-hydrogel on in vitro and in vivo vascularization.

We produced a chitosan/fucoidan micro complex-hydrogel as a carrier for controlled release of heparin binding growth factors such as fibroblast growth factor (FGF)-2. Material consisting of a soluble chitosan (CH-LA) mixed with fucoidan yielded a water-insoluble and injectable hydrogel with filamentous particles. In this study, we examined the ability of the chitosan/fucoidan complex-hydrogel to immobilize FGF-2 and to protect its activity, as well as the controlled release of FGF-2 molecules. The chitosan/fucoidan complex-hydrogel has high affinity for FGF-2 (K(d) = 5.4 x 10(-) (9)M). The interaction of FGF-2 with chitosan/fucoidan complex-hydrogel substantially prolonged the biological half-life time of FGF-2. It also protected FGF-2 from inactivation, for example by heat and proteolysis, and enhance FGF-2 activity. When FGF-2-containing complex-hydrogel was subcutaneously injected into the back of mice, significant neovascularization and fibrous tissue formation were induced near the site of injection at 1 week, and the complex-hydrogel was biodegraded and disappeared by 4 weeks. These findings indicate that controlled release of biologically active FGF-2 molecules is caused by both slow diffusion and biodegradation of the complex-hydrogel, and that subsequent induction of vascularization occurs. FGF-2-containing chitosan/fucoidan micro complex-hydrogel is thus useful and convenient for treatment of ischemic disease.

Enhanced healing of mitomycin C-treated wounds in rats using inbred adipose tissue-derived stromal cells within an atelocollagen matrix.

The aim of this study was to evaluate the potential accelerating effects of an adipose tissue-derived stromal cells (ATSC)-containing atelocollagen matrix with silicone membrane (ACMS) for repairing mitomycin C-treated healing-impaired wounds. Mitomycin C was applied to full-thickness skin incisions in this study to create a healing-impaired wound model in rat. After thoroughly washing out the mitomycin C from the wound, ACMS alone or ATSC-containing ACMS was applied to the wounds. Histological sections of the wounds were then prepared at indicated time periods after the treatments. These results indicated significantly advanced granulation tissue and capillary formations in the healing-impaired wounds treated with ATSC-containing ACMS compared with those treated with ACMS alone. Thus, this study suggested that transplantation of inbred ATSC-containing ACMS is effective for repairing healing-impaired wounds.

Phase II trial of amrubicin for treatment of refractory or relapsed small-cell lung cancer: Thoracic Oncology Research Group Study 0301.

PURPOSE: This multicenter, phase II study was conducted to evaluate the activity of amrubicin, a topoisomerase II inhibitor, against refractory or relapsed small-cell lung cancer (SCLC). PATIENTS AND METHODS: SCLC patients with measurable disease who had been treated previously with at least one platinum-based chemotherapy regimen and had an Eastern Cooperative Oncology Group performance status of 0 to 2 were eligible. Two groups of patients were selected: patients who experienced first-line treatment failure less than 60 days from treatment discontinuation (refractory group), and patients who responded to first-line treatment and experienced disease progression > or = 60 days after treatment discontinuation (sensitive group). Amrubicin was administered as a 5-minute daily intravenous injection at a dose of 40 mg/m2 for 3 consecutive days, every 3 weeks. RESULTS: Between June 2003 and December 2004, 60 patients (16 refractory and 44 sensitive) were enrolled. The median number of treatment cycles was four (range, one to eight). Grade 3 or 4 hematologic toxicities comprised neutropenia (83%), thrombocytopenia (20%), and anemia (33%). Febrile neutropenia was observed in three patients (5%). Nonhematologic toxicities were mild. No treatment-related death was observed. The overall response rates were 50% (95% CI, 25% to 75%) in the refractory group, and 52% (95% CI, 37% to 68%) in the sensitive group. The progression-free survival, overall survival, and 1-year survival in the refractory group and the sensitive group were 2.6 and 4.2 months, 10.3 and 11.6 months, and 40% and 46%, respectively. CONCLUSION: Amrubicin exhibits significant activity against SCLC, with predictable and manageable toxicities; this agent deserves to be studied more extensively in additional trials.

Phase I study of cisplatin and irinotecan combined with concurrent hyperfractionated accelerated thoracic radiotherapy for locally advanced non-small cell lung carcinoma.

BACKGROUND: Irinotecan, when combined with cisplatin, is an effective treatment for advanced non-small cell lung cancer (NSCLC). This constitutes a rationale for conducting a phase I study of chemoradiotherapy including this combination for locally advanced NSCLC. PATIENTS AND METHODS: Patients with locally advanced NSCLC and a performance status of 0 or 1 were eligible. The protocol consisted of escalating doses of irinotecan on days 1 and 15, and daily low-dose cisplatin (6 mg/m(2) daily for a total dose of 120 mg/m(2)) combined with concurrent hyperfractionated accelerated thoracic irradiation (1.5 Gy twice daily for a total dose of 60 Gy). RESULTS: The maximum tolerable dose was 50 mg/m(2) of irinotecan, and the dose-limiting toxicity was esophagitis. Tumor response was observed in 50% of cases, and the median survival time of the 12 patients enrolled was 10.1 months, including two patients with 5-year disease-free survival. A pharmacokinetics study demonstrated an accumulation of total platinum, but not of free platinum, during the 26-day treatment period. CONCLUSION: The recommended dose for phase II studies was determined.

Self-association of PAR-3-mediated by the conserved N-terminal domain contributes to the development of epithelial tight junctions.

PAR-3 is a scaffold-like PDZ-containing protein that forms a complex with PAR-6 and atypical protein kinase C (PAR-3-atypical protein kinase C-PAR-6 complex) and contributes to the establishment of cell polarity in a wide variety of biological contexts. In mammalian epithelial cells, it localizes to tight junctions, the most apical end of epithelial cell-cell junctions, and contributes to the formation of functional tight junctions. However, the mechanism by which PAR-3 localizes to tight junctions and contributes to their formation remains to be clarified. Here we show that the N-terminal conserved region, CR1-(1-86), and the sequence 937-1,024 are required for its recruitment to the most apical side of the cell-cell contact region in epithelial Madin-Darby canine kidney cells. We also show that CR1 self-associates to form an oligomeric complex in vivo and in vitro. Further, overexpression of CR1 in Madin-Darby canine kidney cells disturbs the distribution of atypical protein kinase C and PAR-6 as well as PAR-3 and delays the formation of functional tight junctions. These results support the notion that the CR1-mediated self-association of the PAR-3-containing protein complex plays a role during the formation of functional tight junctions.

In vitro conversion of irinotecan to SN-38 in human plasma.

Irinotecan is an active cytotoxic agent for various cancers, and is converted to SN-38, its most active metabolite, by carboxylesterase converting enzyme (CCE) in vivo. Although the primary metabolic site is in the liver, ex vivo studies have proven that irinotecan is also converted to SN-38 in intestines, plasma and tumor tissues. The present study attempted to elucidate the in vitro conversion efficiency in human plasma, and to examine possible inter-individual variability and its clinical significance. Plasma samples were taken from 57 patients with lung cancer, 3 patients with benign pulmonary diseases and 9 healthy volunteers. After addition of 157 mM irinotecan to plasma, time courses of SN-38 concentration, measured by high-performance liquid chromatography (HPLC), were investigated. All subjects showed linear increase in SN-38 concentration during the first 60-min period, followed by a plateau. Mean and standard deviation of the conversion rate in the first 60 min were 515.9 +/- 50.1 pmol/ml/h (n = 69), with a coefficient of variation of 0.097. Although most of the subjects showed comparable conversion rates, 3 subjects had significantly higher conversion rates. In conclusion, the results of this study suggest that the enzyme activity of CCE in human plasma may show inter-individual variability.