David W. Ho

Significance of CD90+ cancer stem cells in human liver cancer.

This study characterized cancer stem cells (CSCs) in hepatocellular carcinoma (HCC) cell lines, tumor specimens, and blood samples. The CD90+ cells, but not the CD90(-) cells, from HCC cell lines displayed tumorigenic capacity. All the tumor specimens and 91.6% of blood samples from liver cancer patients bore the CD45(-)CD90+ population, which could generate tumor nodules in immunodeficient mice. The CD90+CD44+ cells demonstrated a more aggressive phenotype than the CD90+CD44(-) counterpart and formed metastatic lesions in the lung of immunodeficient mice. CD44 blockade prevented the formation of local and metastatic tumor nodules by the CD90+ cells. Differential gene expression profiles were identified in the CD45(-)CD90+ and CD45(-)CD90(-) cells isolated from tissue and blood samples from liver cancer patients and controls.

Identification of local and circulating cancer stem cells in human liver cancer.

Increasing evidence has revealed the importance of cancer stem cells (CSCs) in carcinogenesis. Although liver CSCs have been identified in hepatocellular carcinoma (HCC) cell lines, no data have shown the presence of these cells in human settings. The present study was designed to delineate CSCs serially from HCC cell lines, human liver cancer specimens to blood samples, using CD90 as a potential marker. The number of CD90+ cells increased with the tumorigenicity of HCC cell lines. CD45−CD90+ cells were detected in all the tumor specimens, but not in the normal, cirrhotic, and parallel nontumorous livers. In addition, CD45−CD90+ cells were detectable in 90% of blood samples from liver cancer patients, but none in normal subjects or patients with cirrhosis. A significant positive correlation between the number of CD45−CD90+ cells in the tumor tissues and the number of CD45−CD90+ cells in the blood samples was identified. CD90+ cells sorted from cell lines and CD45−CD90+ cells from the tumor tissues and blood samples of liver cancer patients generated tumor nodules in immunodeficient mice. Serial transplantation of CD90+ cells from tumor xenografts generated tumor nodules in a second and subsequently third batch of immunodeficient mice. Treatment of CD90+ CSCs with anti‐human CD44 antibody induced cell apoptosis in a dose‐dependent manner. Conclusion: Identification of CD45−CD90+ CSCs in both tumor tissues and circulation suggests that CD45−CD90+ could be used as a marker for human liver cancer and as a target for the diagnosis and therapy of this malignancy. (HEPATOLOGY 2008.)

European Stroke Initiative Recommendations for Stroke Management

This article summarises recommendations for acute management of stroke by the European Stroke Initiative (EUSI), on behalf of the European Stroke Council (ESC), the European Neurological Society (ENS), and the European Federation of Neurological Societies (EFNS).

Initial Clinical Experience with an Implantable Human Atrial Defibrillator

Low energy biatrial shock is an effective means of restoring sinus rhythm in patients with atril fibrillation (AF). Ventricular proarrhythmia is avoided provided that shocks are well synchronized to R waves that are not at closely coupled intervals or preceded by long‐short cycles. Based on these principles, an implantable atrial defibrillator has been developed and was implanted in three patients with drug refractory paroxysmal AF. The device detects AF via an actively fixed right atrial and a self‐retaining coronary sinus defibrillating leads, and delivers 3/3 ms biphasic shocks up to 300 V synchronized to the R wave. The mean implant threshold (ED50) was 195V (1.8 J), and minimum voltage at conversion during follow‐up assessments at 1, 3, and 6 months were 260 V, 2.5 J, 250 V, 2.3 J, and 300 V, 3.0 J respectively. Detection of AF was 100% specific and shocks were 100% synchronized, although only a proportion of synchronized R waves were considered suitable for shock delivery primarily because of closely coupled cycles. Three patients had 9 spontaneous AF episodes. 8/9 (89%) successfully defibrillated by shocks of 260–300 V. Sedation was not used in 4 out of 9 (45%) episodes. Backup ventricular pacing was initiated by the device in 6 out of(67%) episodes. One patient had more frequent AF after lead placement, which subsided after a change of medication. There was no ventricular proarrhythmia. It is concluded that an implantable atrial defibrillator is a viable therapy for selected patients with paroxysmal AF. The device is capable of accurate AF detection, R wave synchronization and ventricular support pacing after successful defibrillation of AF.

An Akt/Hypoxia-Inducible Factor-1α/Platelet-Derived Growth Factor-BB Autocrine Loop Mediates Hypoxia-Induced Chemoresistance in Liver Cancer Cells and Tumorigenic Hepatic Progenitor Cells

Purpose: The goals of the present study were to investigate the mechanism of hypoxia-mediated chemoresistance in liver cancer cells and tumorigenic hepatic progenitor (oval) cells and to determine whether disrupting an Akt/hypoxia-inducible factor-1α (HIF-1α)/platelet-derived growth factor (PDGF)-BB autocrine loop can enhance chemotherapeutic efficacy in hypoxia. Experimental Design: Five hepatocellular carcinoma (HCC) cell lines and two hepatic progenitor cell lines were treated in vitro with cisplatin under both normoxic and hypoxic conditions. To generate ischemic hypoxia for tumor cells in vivo, hepatic artery ligation was applied to an orthotopic HCC model. Cisplatin and YC1, which is a HIF-1α inhibitor, were administered by portal vein and intratumoral injections, respectively. Results: Cell viability was higher under hypoxic than normoxic conditions. HIF-1α and Akt were up-regulated under hypoxic conditions, forming an autocrine signaling loop with PDGF-BB. Akt/HIF-1α/PDGF-BB signaling regulated Akt to confer cisplatin resistance to HCC cell lines in vitro. This autocrine signaling loop also contributed to chemoresistance in the tumorigenic hepatic progenitor cell line PIL2 under hypoxic conditions but not in the nontumorigenic cell line PIL4. In an orthotopic HCC model, combining blockade of HIF-1α activity with ischemic hypoxia significantly enhanced the efficacy of chemotherapy, leading to suppression of tumor growth and prolongation of animal survival. Conclusion: Blockade of Akt/HIF-1α/PDGF-BB autocrine signaling could enhance the chemosensitivity of liver cancer cells and tumorigenic hepatic progenitor cells under hypoxic conditions and thus provide an effective therapeutic strategy for HCC.

Up-Regulation of Vascular Endothelial Growth Factor (VEGF) in Small-for-Size Liver Grafts Enhances Macrophage Activities through VEGF Receptor 2-Dependent Pathway

This study aims to investigate the potential role of vascular endothelial growth factor (VEGF) and VEGF-R2 (fetal liver kinase (Flk)-1) in mediating macrophage activities in small-for-size liver transplantation. A rat orthotopic liver transplantation model was performed using either whole, 50, or 30% liver grafts (both 50 and 30% were regarded as small-for-size) in syngeneic or allogeneic combinations, respectively. Firstly, the mRNA and protein levels of VEGF and Flk-1 in liver grafts were detected by RT-PCR and Western blot, and the number of Flk-1+ macrophages (labeled by ED1) was determined by flow cytometry. It was found that the small-for-size isografts and allografts presented higher levels of VEGF and Flk-1 expression than the whole isograft and allograft. In addition, a higher number of Flk-1+ED1+ cells were detected in the small-for-size isografts and allografts than the whole isograft and allograft. Secondly, our study revealed that macrophage cell lines did not initially express detectable Flk-1, but could be induced by VEGF, and the inducible expression of Flk-1 in macrophages was related to their migration and proliferation activities. Finally, our study demonstrated that the induction of Flk-1 expression on macrophages by VEGF was associated with the expression of NF-κB and heat shock protein 90. In conclusion, the present study showed that the up-regulated expression of VEGF and its interaction with Flk-1 in small-for-size liver grafts might facilitate the activities of macrophages.

Comparison of systemic responses of radiofrequency ablation, cryotherapy and surgical resection in a porcine liver model

Background:The degree of systemic response after hepatic radiofrequency ablation (RFA) has not been well investigated.Methods: An in vivo study was conducted on 23 domestic swine. Different hepatic procedures (RFA, cryotherapy, hepatic pedicle ligation, and hepatectomy) were performed on the medial lobe of the liver (30% of the liver volume). Systemic responses in terms of systemic inflammatory marker changes and end-organ functions were determined.Results: During the early postoperative period, the systemic inflammatory marker concentrations (tumor necrosis factor-α and interleukin-1β) in the RFA group were significantly lower than in the cryotherapy group but significantly higher than in the control group. The corresponding concentrations in the hepatectomy group remained similar to those in the control group. The pattern of changes of serum inflammatory marker concentrations in the pedicle ligation group followed the pattern in the RFA group. The serum intracellular content concentrations (lactate dehydrogenase and urate) of the cryotherapy group peaked at 6 hours after operation, which was significantly later than in the other groups. Liver function, renal function, and coagulation profiles remained normal in the RFA group. However, the renal function deteriorated in the cryotherapy group on day 1. Both platelet count and activated clotting time showed significant derangement in the cryotherapy group compared with the control group. There was more severe interstitial pneumonitic change of the porcine lung after cryotherapy than after RFA.Conclusions: The systemic responses of RFA were significantly less severe than those of cryotherapy in this porcine model. However, the increase in serum inflammatory markers and pneumonitis after RFA was substantial when compared with hepatectomy.

Epileptic Seizures Attributed to Cerebral Hyperperfusion after Percutaneous Transluminal Angioplasty and Stenting of the Internal Carotid Artery

Cerebral hyperperfusion syndrome as a complication of carotid endarterectomy (CEA) has been widely reported in the surgical literature. It may occur within hours to 3 weeks after CEA and is characterized by symptoms ranging from headaches, fits, confusion, focal neurological signs to intracerebral hemorrhage. Although percutaneous transluminal angioplasty (PTA) and stenting are increasingly performed as an alternative to CEA in the treatment of carotid artery stenosis, few cases of cerebral hyperperfusion injury following carotid stenting have been reported. We describe 2 cases of cerebral hyperperfusion syndrome following PTA and stenting for high-grade internal carotid artery (ICA) stenosis. Both cases involved a lesion of 95% in severity. The first case was a 73-year-old man who developed generalized convulsion 7 h following stenting to the left ICA. The second case was an 80-year-old woman who developed recurrent right periorbital headache and confusion 16 h after stenting to the right ICA, followed by left upper limb seizure 14 days later. Both patients fully recovered without any intracerebral hemorrhage or infarction. To our knowledge, this is the first report of cerebral hyperperfusion injury after carotid stenting without associated intracranial hemorrhage and with full recovery. In the patient with neurological symptoms following carotid stenting, it is important to consider cerebral hyperperfusion syndrome as a differential diagnosis to embolic or hemorrhagic stroke since early recognition and meticulous control of blood pressure may prevent progression to cerebral hemorrhage and death.

The Potential Role of Hypoxia Inducible Factor 1α in Tumor Progression after Hypoxia and Chemotherapy in Hepatocellular Carcinoma

This study investigates the possible molecular basis leading to failure in a treatment that is composed of hypoxia and chemotherapy in a rat orthotopic hepatoma model. Hypoxia was induced by hepatic artery ligation, whereas chemotherapeutic effect was achieved by intraportal injection of cisplatin. High-dose sodium salicylate was administered to achieve transcriptional blockade. Significant prolongation of animal survival was observed in the groups receiving hepatic artery ligation with cisplatin or sodium salicylate. Massive tumor cell necrosis and apoptosis were found in the ligation and all of the combined treatment groups. Up-regulation of hypoxia inducible factor 1α (HIF-1α) and vascular endothelial growth factor (VEGF) at both mRNA and protein levels were detected in the groups receiving ligation and ligation with cisplatin, whereas a decreased level of von Hippel-Lindau tumor suppressor protein was identified in the group receiving ligation with cisplatin. Sodium salicylate enhanced expression of von Hippel-Lindau tumor suppressor protein but down-regulated HIF-1α and VEGF levels after ligation with or without cisplatin. An increased number of activated hepatic stellate cells in the tumors were observed in the ligation and ligation with cisplatin groups, whereas they were greatly reduced by sodium salicylate. In vitro study revealed that under hypoxic condition, both cisplatin and sodium salicylate could remarkably augment P53 and caspase 3 levels. Cisplatin stimulated HIF-1α up-regulation, whereas sodium salicylate suppressed HIF-1α expression. In conclusion, tumor progression after hypoxia and chemotherapy might be related to up-regulation of HIF-1α and subsequent VEGF production, and transcriptional blockade by sodium salicylate could enhance the therapeutic efficacy of hypoxia and chemotherapy.

Heme oxygenase-1 potentiates the survival of small-for-size liver graft

This study aims to clarify the role of heme oxygenase‐1 (HO‐1) in small‐for‐size liver transplantation. Transplantation was performed using 40% small‐for‐size or 100% whole liver grafts in rats. When no treatment was given, over‐expression of HO‐1 was detected predominantly in the small‐for‐size grafts at 6 hours after reperfusion as compared to whole grafts in both syngeneic and allogeneic combinations. Recombinant adenoviral vector encoding HO‐1 gene (AdHO‐1) administered to donors 48 hours before transplantation enhanced HO‐1 expression in both whole and small‐for‐size allografts, with a predominant augmentation in the small‐for‐size allografts, suggesting favorable conditions for the induction of HO‐1 expression in small‐for‐size allografts. In close relation to the expression level of HO‐1, AdHO‐1 significantly prolonged both whole and small‐for size allograft survivals, with a remarkable effect in the small‐for‐size allograft group. The prolongation of allograft survival was blocked by the HO‐1 inhibitor (zinc protoprophyrin IX). The non‐treated small‐for‐size allografts demonstrated impaired liver function during the early period after reperfusion, which could be improved by over‐expression of HO‐1, but reversed by the HO‐1 inhibitor. The markedly increase expression HO‐1 in small‐for‐size allografts was associated with lower levels of adhesion molecules and pro‐inflammatory cytokines in the early phase after reperfusion. These findings support the beneficial effects of HO‐1 on allograft survival. In conclusion, the ability of small‐for‐size grafts in the induction of HO‐1 expression might facilitate their own survival in liver transplantation. (Liver Transpl 2004;10:784–793.)