Platelets modulate the proteolysis of factor VIII:C protein by plasmin

Factor VIII coagulant protein (VIII:C) functions as a critical cofactor with factor IXa, calcium ions, and phospholipid during the activation of factor X. In the course of this reaction, the activity of VIII:C is first increased and then is destroyed by one or more serine proteases that are part of the coagulation sequence. In this study, we have investigated the influence of platelets on the inactivation of VIII:C by plasmin. Platelets were separated from plasma proteins in the presence of granule release inhibitors and were incubated with plasmin and isolated VIII:C or the complex of purified VIII:C/von Willebrand factor (vWF); VIII:C activity and antigen levels were assessed over time. In the presence of platelets, the isolated VIII:C showed an initial increase in VIII:C activity that was not present when platelets were absent, and the VIII:C/vWF showed an increase in VIII:C activity over that seen when platelets were absent. In addition, platelets stabilized VIII:C activity over a one-hour time course when compared with buffer. The VIII:C antigen did not increase and decreased slowly whether platelets were present or absent. Preincubating the platelets with ristocetin, collagen, or plasmin did not alter the results, and experiments using platelets from a patient with severe von Willebrand's disease also showed a pattern similar to that seen with normal platelets. Experiments using fixed platelets or phospholipid vesicles showed that they did not support the activation reaction or delay the inactivation reaction. These studies demonstrate that platelets modulate the activation and inactivation of VIII:C by plasmin, apparently by a mechanism that is independent of the platelet release reaction.     

Inverse relation between iodine intake and thyroid blood flow: color Doppler flow imaging in euthyroid humans

High intake of iodine inhibits iodide trapping, iodide organification, and hormone release from the human thyroid. We investigated whether iodine intake also affects thyroid blood flow, as was suggested by a recent study in euthyroid rats. With a Color Doppler device we made 14 consecutive Duplex-Doppler registrations of both superior thyroid arteries in 10 euthyroid volunteers during baseline iodine intake (1 week), iodine restriction (2 weeks), return to baseline (1 week), and iodine excess (1 week; 80 mumol sodium iodide/day). Vessel diameters and mean flow velocity were measured on videotape recordings by a "blinded" observer. Baseline iodide excretion was 0.88 +/- 0.38 (+/- SD) mumol/day. Mean flow velocity was 13.9 +/- 4.1 cm/s, and vessel diameter was 1.07 +/- 0.22 mm. Blood flow was 7.7 +/- 3.8 mL/min.superior thyroid artery. During the low iodine diet, excretion dropped to 0.49 +/- 0.16 mumol/day, and blood flow increased to 11.0 +/- 5.0 mL/min (P less than 0.001), remaining elevated (10.3 +/- 4.4 mL/min) during the second baseline diet. During high iodide intake, blood flow averaged 5.8 +/- 3.4 mL/min (P less than 0.001), and the expected decrease in thyroid hormone levels and increase in TSH were seen. We conclude that thyroid blood flow responds inversely, and independently from TSH, to changes in iodine intake in euthyroid humans.     

Detection of hepatitis C viral RNA sequences in fresh and paraffin-embedded liver biopsy specimens of non-A, non-B hepatitis patients.

In this study methods of HCV-RNA detection in fresh frozen and formalin-fixed, paraffin-embedded liver biopsies are described. Of 22 untreated chronic non-A, non-B hepatitis patients and 6 control patients, a plasma sample and part of a liver biopsy were freshly frozen for hepatitis C virus (HCV) cDNA-PCR. From 16 of the same non-A, non-B hepatitis patients and from 5 of the same control patients formalin-fixed, paraffin-embedded liver tissue from the same biopsy was available also for HCV cDNA-PCR. In 13 of 22 non-A, non-B hepatitis patients HCV-RNA could be detected in plasma as well as in liver tissue. In the other 9 non-A, non-B hepatitis patients and in 6 control patients, no HCV-RNA was detectable in either plasma or liver tissue. The comparison between HCV cDNA-PCR results in fresh frozen versus formalin-fixed, paraffin-embedded liver biopsies showed that although detection of HCV-RNA in both correlated 100% the quantity of HCV-RNA was lower in the formalin-fixed, paraffin-embedded liver biopsies of 5 of 8 patients for whom end-point dilution titration of liver RNA was performed. We conclude that using the procedures described HCV-RNA can be reliably detected in both fresh-frozen and formalin-fixed, paraffin-embedded liver biopsies and that HCV cDNA-PCR in liver tissue may become an important assay, especially for monitoring anti-viral therapy.     

Hematopoietic growth factor expression and ATRA sensitivity in acute promyelocytic blast cells

Acute promyelocytic leukemia (APL) is a homogeneous subgroup of acute myeloid leukemias (AMLs) characterized by the presence of the t(15,17) translocation and the resulting promyelocytic myeloid leukemia/retinoic acid receptor alpha (PML/RAR alpha) fusion proteins. To date APL is the only AML that is sufficiently sensitive to all-trans retinoic acid's (ATRA) differentiating effect. In vivo ATRA alone achieves complete remission in most APL patients. However, failure or partial responses are observed and the molecular basis of the absence of ATRA response in these patients has not been determined. To gain insights in the cell growth and differentiation of APL cells, expression of hematopoietic growth factors (HGF) shown to be produced by leukemic cells (interleukin-1 beta [IL-1 beta], IL-6, tumor necrosis factor alpha (TNF alpha), granulocyte colony-stimulating factor [G-CSF], granulocyte- macrophage colony-stimulating factor [GM-CSF], and IL-3) was studied in 16 APL samples. Twelve APL cases expressed IL-1 beta, IL-6, and TNF alpha, but not G-CSF, GM-CSF, and IL-3. These cases achieved complete remission with ATRA therapy. The four remaining patients (either TNF alpha negative or G-CSF, GM-CSF or IL-3 positive) did not achieve complete remission with ATRA. In all cases, in vivo response to ATRA therapy was correlated to the in vitro differentiation effect of all- trans retinoic acid 10(-6) mol/L. Thus, ATRA differentiation induction was strongly correlated to the HGF expression (P < .0001). These results suggest that the presence or absence of HGF's expression by APL cells may contribute to the therapeutic effect of ATRA in this disease.     

Polyclonal breast cancer metastases arise from collective dissemination of keratin 14-expressing tumor cell clusters

Recent genomic studies challenge the conventional model that each metastasis must arise from a single tumor cell and instead reveal that metastases can be composed of multiple genetically distinct clones. These intriguing observations raise the question: How do polyclonal metastases emerge from the primary tumor? In this study, we used multicolor lineage tracing to demonstrate that polyclonal seeding by cell clusters is a frequent mechanism in a common mouse model of breast cancer, accounting for >90% of metastases. We directly observed multicolored tumor cell clusters across major stages of metastasis, including collective invasion, local dissemination, intravascular emboli, circulating tumor cell clusters, and micrometastases. Experimentally aggregating tumor cells into clusters induced a >15-fold increase in colony formation ex vivo and a >100-fold increase in metastasis formation in vivo. Intriguingly, locally disseminated clusters, circulating tumor cell clusters, and lung micrometastases frequently expressed the epithelial cytoskeletal protein, keratin 14 (K14). RNA-seq analysis revealed that K14⁺ cells were enriched for desmosome and hemidesmosome adhesion complex genes, and were depleted for MHC class II genes. Depletion of K14 expression abrogated distant metastases and disrupted expression of multiple metastasis effectors, including Tenascin C (Tnc), Jagged1 (Jag1), and Epiregulin (Ereg). Taken together, our findings reveal K14 as a key regulator of metastasis and establish the concept that K14⁺ epithelial tumor cell clusters disseminate collectively to colonize distant organs.During metastasis, cancer cells escape the primary tumor, travel through the circulation, and colonize distant organs. Conventional models of cancer progression propose that each metastasis arises from the clonal outgrowth of a single tumor cell and this conceptual framework is a foundation for models, such as epithelial-mesenchymal transition (EMT) and migratory cancer stem cells (1).Challenging the generality of the single-cell/single-metastasis model are long-standing clinical observations that tumor cell clusters (also termed “tumor clumps”) are also observed across the stages of metastasis. Tumor cell clusters are detected in the bloodstream of cancer patients (2), clusters can efficiently seed metastases (3), and though rare, circulating tumor cell (CTC) clusters have prognostic significance (4, 5). Furthermore, metastases are composed of multiple genetically distinct tumor cell clones, in mouse models of breast, pancreas, and small cell carcinoma (5–7), and in human metastatic prostate cancer patients (8). Taken together, these observations provide accumulating evidence that tumor cell clusters contribute to metastasis. However, they leave unresolved two important questions: how do tumor cell clusters emerge from the primary tumor, and which molecular features identify cell clusters that metastasize?An important clinical observation is that cancer cells invade the surrounding stroma as cohesive clusters in the majority of epithelial tumors, a process termed “collective invasion” (9, 10). In breast cancer, collective invasion is facilitated by invasive leader cells, a subpopulation of tumor cells that highly express keratin 14 (K14) and other basal epithelial markers (11). K14⁺ cells are migratory, protrusive, and lead trailing K14⁻ cells, while maintaining cell–cell cohesion and E-cadherin–based cell contacts.In this study, we sought to understand how these K14⁺ cells exit collective invasion strands in the primary tumor and travel to distant organs (12). One hypothesis is that collective invasion is an intermediate step toward eventual single-cell dissemination and monoclonal metastasis. However, tumor cell clusters are detected in circulation (5) and primary human breast tumors can disseminate collectively into the surrounding extracellular matrix in ex vivo assays (13–15). These data prompted an alternative hypothesis, that collectively invading K14⁺ cancer cells could initiate and complete the metastatic process as a cohesive multicellular unit. Here we define the clonal nature of metastases in a spontaneous mouse model of metastasis to the lungs (16, 17), in which the predominant invasive form in the primary tumor is collective invasion strands led by K14⁺ cells (11). We establish that the majority of metastases arise from polyclonal seeds, and show that disseminated tumor cell clusters are predominantly composed of K14⁺ cells. We propose a mechanism for polyclonal metastasis via the collective invasion, dissemination, and colonization of clusters of K14⁺ cancer cells.     

Biological evaluation of intervertebral disc cells in different formulations of gellan gum‐based hydrogels

Gellan gum (GG)‐based hydrogels are advantageous in tissue engineering not only due to their ability to retain large quantities of water and provide a similar environment to that of natural extracellular matrix (ECM), but also because they can gelify in situ in seconds. Their mechanical properties can be fine‐tuned to mimic natural tissues such as the nucleus pulposus (NP). This study produced different formulations of GG hydrogels by mixing varying amounts of methacrylated (GG‐MA) and high‐acyl gellan gums (HA‐GG) for applications as acellular and cellular NP substitutes. The hydrogels were physicochemically characterized by dynamic mechanical analysis. Degradation and swelling abilities were assessed by soaking in a phosphate buffered saline solution for up to 170 h. Results showed that as HA‐GG content increased, the modulus of the hydrogels decreased. Moreover, increases in HA‐GG content induced greater weight loss in the GG‐MA/HA‐GG formulation compared to GG‐MA hydrogel. Potential cytotoxicity of the hydrogel was assessed by culturing rabbit NP cells up to 7 days. An MTS assay was performed by seeding rabbit NP cells onto the surface of 3D hydrogel disc formulations. Viability of rabbit NP cells encapsulated within the different hydrogel formulations was also evaluated by Calcein‐AM and ATP assays. Results showed that tunable GG‐MA/HA‐GG hydrogels were non‐cytotoxic and supported viability of rabbit NP cells. Copyright © 2012 John Wiley & Sons, Ltd.     

Platelet glycoproteins IIb and IIIa as a calcium channel in liposomes

Human platelet membrane glycoproteins IIb and IIIa (GPIIb and IIIa) were incorporated into phospholipid vesicles by the reverse-phase technique to assess the ability of GPIIb and IIIa to function as a Ca2+ channel. Movement of Ca2+ across the lipid bilayer was quantitated by injection of proteoliposomes with encapsulated Fura-2 into Ca2+ buffers and measurement of Fura-2 fluorescence as an indicator of Ca2+ influx. Reciprocally, to assess the function of proteins in an inside-out orientation, Ca2+-loaded vesicles were injected into Ca2+-free buffer and Ca2+ efflux monitored by a calcium electrode. Incorporation of the IIb-IIIa complex produced significant facilitation of Ca2+ movement across the lipid bilayer. No net transmembrane Ca2+ movement was seen with dissociated IIb and IIIa. Movement of Ca2+ was proportional to the transmembrane Ca2+ gradient. Ca2+ movement into the vesicles was inversely proportional to extravesicular NaCl from 25 to 150 mmol/L, analogous to several studies in the intact platelet. Adenosine triphosphate had no effect on Ca2+ movement into or out of the vesicles. Specific inhibition of a Ca2+ shift into the vesicles was seen with M148, a monoclonal antibody to IIb/IIIa, while no inhibition was observed with a panel of other anti-IIb/IIIa monoclonal antibodies. This suggests that a specific site on the complex or orientation of the complex is essential for calcium channel function. These data demonstrate that the GPIIb/IIIa complex can serve as a passive Ca2+ channel across a phospholipid bilayer and has the potential to play a role in Ca2+ flux across the platelet plasma membrane.     

Factor V deficiency in Philadelphia-positive chronic myelogenous leukemia

Factor V deficiency has been identified in 8 of 8 patients 7--20 yr of age, with Philadelphia-positive (Ph1+) chronic myelogenous leukemia (CML). In these 8 patients, factor V deficiency was not due to hepatic dysfunction, factor V inhibitors, or disseminated intravascular coagulation. In 3 patients, factor V activity rose 10%--12% (0.10--0.12 U/ml) after the infusion of 28--31 ml/kg body weight of fresh frozen plasma (FFP). The rise persisted less than 14 hr. The mean measured postinfusion rise in factor V was 18% of the expected rise calculated from the volume of FFP infused in the patients' plasma volume. In 4 patients, a small transient rise in factor V activity occurred after splenectomy or plateletpheresis. Factor V deficiency was completely corrected after a marked reduction in bone marrow cellularity in 2 patients with Ph1+ CML treated with extensive chemotherapy, total body irradiation, and bone marrow transplantation. Factor V deficiency was retrospectively observed in 6 of 20 patients, ages 20--80 yr, with Ph1+ CML and 3 of 6 patients with other myeloproliferative disorders. The factor V deficiency appears to be associated with the large myeloid- megakaryocytic cell mass characteristic of CML and other myeloproliferative disorders.