Selective Toxicity of a Highly Potent Camptothecin Analogue: A Pilot Study with Glioblastoma Multiforme Cells

BACKGROUND/AIM

We developed a novel camptothecin analogue, CPT417, that yields reduced toxicity compared to other analogues used in chemotherapeutic regimens. In this pilot study, we assessed the activity of CPT417 against glioblastoma multiforme (GBM) cells and glioma stem cells.

MATERIALS AND METHODS

The human U251 GBM cell line and normal human astrocytes were cultured in parallel for clonogenic survival analysis following exposure to increasing concentrations of CPT417. Cell viability of a glioma stem cell line was assessed 5 days after exposure to a range of CPT417 concentrations.

RESULTS

CPT417 completely inhibited clonogenic survival of GBM cells at 10 nM, whereas this concentration only inhibited astrocytes by approximately 50%. Cell viability analysis of glioma stem cell cultures yielded a half-maximal response at 15 nM.

CONCLUSION

CPT417 acts selectively against GBM cells at concentrations that are at least an order of magnitude below reported values for related alkylating agents in clinical use.

Time-resolved ARPES with sub-15 fs temporal and near Fourier-limited spectral resolution

An experimental setup for time- and angle-resolved photoelectron spectroscopy with sub-15 fs temporal resolution is presented. A hollow-fiber compressor is used for the generation of 6.5 fs white light pump pulses, and a high-harmonic-generation source delivers 11 fs probe pulses at a photon energy of 22.1 eV. A value of 13 fs full width at half-maximum of the pump-probe cross correlation signal is determined by analyzing a photoemission intensity transient probing a near-infrared interband transition in 1T-TiSe₂. Notably, the energy resolution of the setup conforms to typical values reported in conventional time-resolved photoemission studies using high harmonics, and an ultimate resolution of 170 meV is feasible.

Observation of unusual topological surface states in half-Heusler compounds LnPtBi (Ln=Lu, Y)

Topological quantum materials represent a new class of matter with both exotic physical phenomena and novel application potentials. Many Heusler compounds, which exhibit rich emergent properties such as unusual magnetism, superconductivity and heavy fermion behaviour, have been predicted to host non-trivial topological electronic structures. The coexistence of topological order and other unusual properties makes Heusler materials ideal platform to search for new topological quantum phases (such as quantum anomalous Hall insulator and topological superconductor). By carrying out angle-resolved photoemission spectroscopy and ab initio calculations on rare-earth half-Heusler compounds LnPtBi (Ln=Lu, Y), we directly observe the unusual topological surface states on these materials, establishing them as first members with non-trivial topological electronic structure in this class of materials. Moreover, as LnPtBi compounds are non-centrosymmetric superconductors, our discovery further highlights them as promising candidates of topological superconductors.

Heusler compounds have been predicted to host topological order with other emergent properties, which yet awaits for experimental evidence. Here, Liu et al. report a direct observation of topological surface states on half-Heusler compounds LnPtBi.

Evolution of the Fermi surface of Weyl semimetals in the transition metal pnictide family

Topological Weyl semimetals (TWSs) represent a novel state of topological quantum matter which not only possesses Weyl fermions (massless chiral particles that can be viewed as magnetic monopoles in momentum space) in the bulk and unique Fermi arcs generated by topological surface states, but also exhibits appealing physical properties such as extremely large magnetoresistance and ultra-high carrier mobility. Here, by performing angle-resolved photoemission spectroscopy (ARPES) on NbP and TaP, we directly observed their band structures with characteristic Fermi arcs of TWSs. Furthermore, by systematically investigating NbP, TaP and TaAs from the same transition metal monopnictide family, we discovered their Fermiology evolution with spin-orbit coupling (SOC) strength. Our experimental findings not only reveal the mechanism to realize and fine-tune the electronic structures of TWSs, but also provide a rich material base for exploring many exotic physical phenomena (for example, chiral magnetic effects, negative magnetoresistance, and the quantum anomalous Hall effect) and novel future applications.

A Novel Microtubule-Disrupting Agent Induces Endoplasmic Reticular Stress-Mediated Cell Death in Human Hepatocellular Carcinoma Cells

Here, we present evidence of a novel microtubule-disrupting agent, N-deacetyl-N-(chromone-2-carbonyl)-thiocolchicine (TCD), exhibiting potent antitumor activity (with IC₅₀ values in the nanomolar range) against hepatocellular carcinoma cell lines. Cell cycle analysis revealed that TCD induced G₂/M cell-cycle arrest in a dose- and time-dependent manner in both Hep-J5 and Mahlavu HCC cell lines. TCD also induced a decrease in mitochondrial membrane potential (ΔΨm) and caused DNA damage. Mechanistically, TCD activated protein kinase RNA-like endoplasmic reticular kinase and several transcription factors, including activating transcription factor (ATF) 6, ATF4, ATF3, and the CCAAT-enhancer binding protein homologous protein. These data clearly demonstrate that the antitumor activity of TCD is mechanistically linked to its capacity to trigger both intrinsic and extrinsic apoptotic cell death via endoplasmic reticular stress pathway. The potent antitumor activity of TCD was similarly demonstrated in a hepatocellular carcinoma xenograft model, where 5 and 10 mg/kg doses of TCD significantly arrested Hep-J5 and Mahlavu tumor growth. Our finding suggests that TCD is a promising therapeutic agent against hepatocellular carcinoma; further translational assessment of its clinical usage is warranted.

Radiation-associated Cardiac Injury

Chest radiotherapy continues to play an important role in the treatment of breast cancer, Hodgkin's lymphoma, and other malignancies. Subsequent cardiac injury has been described involving essentially all structures of the heart, with most radiation-induced injury being progressive in nature. Our understanding over the multifactorial etiology and development of radiation-associated cardiac injury has advanced, leading to improved techniques aimed at decreasing cardiac radiation exposure and associated risks. Monitoring after radiotherapy clearly appears to be indicated; however, optimal recommendations regarding cardiac screening remain difficult to establish.

Recent developments in radiosensitization

Radiation therapy is essential for local tumor control for many types of cancer histologies. Technological advancements in recent years have allowed for precise irradiation of target tissues while minimizing the dose to non-target tissues. To enhance radiation damage to cancer cells and further limit the radiation effects on normal tissue, researchers have explored compounds that specifically target cancer cells and make them more sensitive to ionizing radiation. Recent radiosensitization research has focused on promising compounds that alter hypoxia, inhibit topoisomerases, interfere with microtubules, and activate caspases, among other mechanisms. Many such compounds have shown impressive results in pre-clinical trials against a variety of cell types, but their safety, efficacy and practicability in clinical trials remains to be demonstrated. This review seeks to provide an overview of recent research in radiosensitization, detailing some of the more successful compounds, and illustrating avenues for future research.

Cardiotoxicity of molecular-targeted drug therapy

Cardiotoxicity is a well-known side-effect described in patients receiving various antineoplastic agents. With the abundance of clinical research and a heavy focus on drug development over the past decade, there has been a major shift in the use of non-specific cytotoxic drugs to molecular-targeted drug therapy. However, as a result, it has become clear that these drugs have numerous adverse effects, both on-target and off-target. Small-molecule tyrosine kinase inhibitors and other molecular-targeted agents, including monoclonal antibodies, have been the primary agents associated with cardiotoxicity. As more molecular-targeted therapies are developed, early recognition and management of drug-related cardiotoxicity will be extremely important in order to reduce morbidity and mortality. Pre-treatment evaluation with a surface electrocardiogram, echocardiography, cardiac history, and comprehensive review of concomitant medications are the current mainstay of treatment. However, much is still unknown about the potential cardiotoxic side-effects of these drug and optimal management. In the present article, we aim to review the cardiovascular implications and related cardiotoxicities associated with molecular target-based chemotherapeutic agents, with special emphasis on hypertension, cardiac dysfunction, and QT prolongation. Their implication, mechanism, and management are discussed where possible.

The N-terminal 33 amino acid domain of Siva-1 is sufficient for nuclear localization

Siva-1 induces apoptosis in multiple pathological processes and plays an important role in the suppression of tumor metastasis, protein degradation, and other functions. Although many studies have demonstrated that Siva-1 functions in the cytoplasm, a few have found that Siva-1 can relocate to the nucleus. In this study, we found that the first 33 amino acid residues of Siva-1 are required for its nuclear localization. Further study demonstrated that the green fluorescent protein can be imported into the nucleus after fusion with these 33 amino acid residues. Other Siva-1 regions and domains showed less effect on Siva-1 nuclear localization. By site-mutagenesis of all of these 33 amino acid residues, we found that mutants of the first 1-18 amino acids affected Siva-1 nuclear compartmentalization but could not complete this localization independently. In summary, we demonstrated that the N-terminal 33 amino acid residues were sufficient for Siva-1 nuclear localization, but the mechanism of this translocation needs additional investigation.

Activation of proacrosin accompanies upregulation of sp32 protein tyrosine phosphorylation in pig sperm

This study investigated the relationship between acrosin activation and pig sperm proacrosin binding protein (sp32) phosphorylation levels. Differently processed pig spermatozoa (fresh semen sperm, capacitation sperm, acrosome reaction sperm, capacitation-like sperm, and thawed sperm) were subjected to sodium dodecyl sulfate polyacrylamide gel electrophoresis and Western blot analysis. The fresh semen and capacitation sperm groups both produced proacrosin protein bands of 55 kDa; however, the result of the fresh semen sperm group was clearer than that of the capacitation sperm group. The thawed sperm group showed a shallow strip at 55 kDa. The capacitation and acrosome reaction sperm groups produced obvious proacrosin protein bands at 35 kDa, and the strips of the capacitation sperm group were again clearer. A faint band was visible at 32 kDa in the acrosome reaction sperm group. The capacitation, thawed, and acrosome reaction sperm groups showed significant strips in sp32, and the bands of the acrosome reaction sperm group were shallower than those of the 2 other groups. The capacitation and thawed sperm groups produced significant strips at 40 kDa, and the capacitation sperm group produced an additional strip at 55 kDa. In conclusion, sp32 phosphorylation levels can promote proacrosin activation into the active acrosin.

Radioprotectants to reduce the risk of radiation-induced carcinogenesis

PURPOSE

Development of radioprotective agents has focused primarily on cytoprotection from relatively high doses of therapeutic radiation and nuclear disasters. Epidemiological studies and radiobiological models report the potential for stochastic effects from relatively low-dose radiation exposure. Diagnostic studies like computed tomography (CT) expose the patient to a small but significant amount of radiation, which has been reported to increase the risk for carcinogenesis. Young patients expected to undergo multiple CT studies may benefit from a protective agent given prior to CT. This review includes published data of agents that have been shown to protect against radiation-induced carcinogenesis. A discussion follows regarding the data that describes the extent of radiation exposure during CT, as well as technical modifications, which also reduce radiation exposure.

RESULTS/CONCLUSIONS

Most experiments have used in vivo animal models or in vitro cell lines. Ethical barriers prevent large-scale human studies, although, there are two prospective human studies from the Chernobyl nuclear accident. Collectively, all of these studies provide evidence of statistically significant reductions in radiation-induced carcinogenesis. Protection is achieved by several mechanisms, which include free radical scavenging, caloric restriction, non-steroidal anti-inflammatory agents, humoral factors, and an oxidative agent. Enhanced efficacy is achieved when targeting multiple mechanisms. The data presented provides the scientific foundation for future development of a radioprotectant that may reduce the risk of carcinogenesis from low-dose exposure when certain at-risk populations undergo diagnostic studies like CT.

Brentuximab vedotin: first-line agent for advanced Hodgkin lymphoma

Hodgkin lymphoma (HL) is characterized by malignant Reed-Sternberg cells which express CD30. Current National Comprehensive Cancer Network guidelines for patients with advanced HL (stage III/IV disease) recommend adriamycin, bleomycin, vinblastine, and dacarbazine (ABVD), or escalated bleomycin, etoposide, adriamycin, cyclophosphamide, vincristine, procarbazine, and prednisone (BEACOPP) as first-line regimens. ABVD appears to be as effective, with fewer side effects, as escalated BEACOPP. Escalated BEACOPP leads to a greater progression-free survival but no difference in overall survival. Recent advancements in technology have enabled an exciting shift to molecular-targeted cancer therapy. Brentuximab vedotin, a CD30-directed antibody conjugate, specifically targets malignant HL cells. It is approved by the Food and Drug Administration for the treatment of systemic anaplastic large-cell lymphoma and refractory HL that has progressed after autologous stem cell transplant, or after two prior multiagent chemotherapy regimens among patients ineligible to receive a transplant.

Current status in chemotherapy for advanced pancreatic adenocarcinoma

Pancreatic ductal adenocarcinoma (PDA) is one of the most lethal types of cancer in the United States. Surgical resection remains the only curative treatment, but fewer than 20% of patients qualify as candidates. The past two decades saw major changes in the treatment of advanced PDA, a shift of standard protocol from 5-fluorouracil to gemcitabine and gemcitabine-based combinations, the introduction of molecular target therapy and multi-agent regimens. However, even with advancements in medicine, PDA is still extremely resistant to currently available regimens, which results in poor prognosis, with only 5.2% of patients alive at three years. This provides a challenge to scientists as they seek to find the best active regimen with the least side-effects. In this article, we review the current recommended guidelines from the National Comprehensive Cancer Network. In addition, we highlight major clinical trials since 2011.

XBP1 promoter polymorphism modulates platinum-based chemotherapy gastrointestinal toxicity for advanced non-small cell lung cancer patients

BACKGROUND

The X-box binding protein 1 (XBP1) is a critical transcription factor in the endoplasmic reticulum stress response, which is essential for the maintenance of cellular homeostasis. Here, we investigated whether the regulatory variant rs2269577 of the XBP1 gene influences clinical outcome in advanced non-small cell lung cancer (NSCLC) patients undergoing platinum-based chemotherapy.

PATIENTS AND METHODS

We recruited 663 Chinese patients with advanced NSCLC treated with platinum-based regimens and assessed the association between rs2269577 and clinical outcome. Subsequent functional analyses, including real-time quantitative PCR and dual-luciferase assays, were performed to explore possible molecular mechanisms.

RESULTS

The G/G genotype of rs2269577 was significantly associated with severe gastrointestinal toxicity compared with the homozygous C/C genotype (P=0.012, odds ratio=2.755), particularly in the female, performance status 0-1, and adenocarcinoma subgroups. No significant relevance was found between rs2269577 and treatment efficacy. In gastric epithelial cells, in vitro molecular analyses demonstrated that XBP1 mRNA expression levels decreased after treatment with cisplatin and the G allele of rs2269577 weakened the transcriptional activity of the XBP1 promoter.

CONCLUSION

This is the first study to evaluate the effect of XBP1 polymorphism on severe chemotherapy-related adverse outcomes in platinum-treated advanced NSCLC patients using both pharmacogenomics and functional molecular analyses.

Improved chemotherapy for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common cancer and it is the third leading cause of cancer-related deaths worldwide. Once diagnosed with the disease, only 30-40% of patients are deemed eligible for curative intention with treatment modalities including surgical resection, liver transplantation, and chemoembolization. Eventually, most patients will receive some forms of chemotherapy in hope of prolonging life. Sorafenib is the first molecular inhibitor to be approved by the FDA for the treatment of advanced HCC. It is a tyrosine kinase inhibitor, targeting multiple molecular pathways. Prior to the arrival of sorafenib, doxorubicin was routinely used as a single drug for advanced HCC, but has shown inefficacy, with a response rate of about 15-20%. Other chemotherapy agents, such as epirubicin, cisplatin, 5-fluorouracil, etoposide and their combinations, demonstrate even lower efficacy. While being considered an advance over conventional chemotherapy, sorafenib only improves life expectancy approximately by 3 months over placebo. With that in mind, continuous efforts have been put into finding new targets and molecular pathways for possible new drug development. In this article, we summarize the current literature over the past year on chemotherapy treatment of advanced HCC.

Improved radiotherapy for primary and secondary liver cancer: stereotactic body radiation therapy

BACKGROUND

Radiation therapy for primary and secondary liver cancer has been limited due to dose-limiting radiation-associated liver injury. Stereotactic body radiation therapy (SBRT) permits higher dose to tumors while minimizing radiation to uninvolved liver. The purpose of this study was to assess the efficacy and safety of SBRT for treating primary and secondary hepatic neoplasms.

MATERIALS AND METHODS

We performed a systematic review of prospective clinical trials published in English.

RESULTS

Fifteen studies involving 158 patients with primary tumors and 341 patients with metastases to the liver were included. Treatment was performed in 1-10 fractions to total doses of 18-60 Gy. One year local control and overall survival rates were 50-100% and 33-100% respectively. There were 13 cases of radiation-induced liver disease and 4 grade 5, 6 grade 4, and 69 grade 3 adverse events reported.

CONCLUSION

For patients who are unable or unwilling to undergo local therapy, SBRT is safe and efficacious for treating primary and secondary liver cancer.

Expression of aberrant beta-catenin and impaired p63 in craniopharyngiomas

Craniopharyngiomas are rare, histologically benign, non-neuroepithelial epithelial tumors arising from the sellar region, the molecular pathogenesis of CPs is yet not understood. The aim of the present study was to assess expression of aberrant beta-catenin and impaired p63 in 66 craniopharyngiomas included 51 adamantinomatous craniopharyngiomas and 15 squamous papillary craniopharyngiomas. On immunohistochemistry, 47 out of 51 adamantinomatous craniopharyngiomas, but not squamous papillary craniopharyngiomas, showed strong nuclear/cytoplasmic expression for beta-catenin predominantly in compactly cohesive epithelial cells within the whorl-like arrays where ki-67 was almost absent and rarely in palisaded cells where ki-67 was mainly present. P63 overexpression was observed in 45 out of 51 adamantinomatous craniopharyngiomas and 14 out of 15 squamous papillary craniopharyngiomas. P63 stained not only in the nuclei of basal layer cells but also within the whorl-like arrays in adamantinomatous craniopharyngiomas and uniformly in squamous papillary craniopharyngiomas. Using quantitative real time polymerase chain reaction techniques to correlate p63 protein expression with p63 mRNA levels, TAp63 isoforms mRNA was reduced, whereas DeltaNp63 mRNA elevated at levels in 5 snap frozen tissue samples with multiple large p63 positive cell clusters compared with normal tissues. In conclusion, the present study confirmed that the two variants of CPs have genetically not only distinctive but also common feature. It demonstrated that cytoplasm/nuclear beta-catenin accumulation is an exclusively characteristic morphology of adaCPs. P63 immunohistochemical overexpression were found in both adaCPs and spCPs variant when analyzed in the same study. Taken together, the impaired p63 expression may be attributed to elevated DeltaNp63 mRNA and reduced TAp63mRNA in CPs.

Nodeless superconducting gap in A(x)Fe2Se2 (A=K,Cs) revealed by angle-resolved photoemission spectroscopy

Pairing symmetry is a fundamental property that characterizes a superconductor. For the iron-based high-temperature superconductors, an s(±)-wave pairing symmetry has received increasing experimental and theoretical support. More specifically, the superconducting order parameter is an isotropic s-wave type around a particular Fermi surface, but it has opposite signs between the hole Fermi surfaces at the zone centre and the electron Fermi surfaces at the zone corners. Here we report the low-energy electronic structure of the newly discovered superconductors, A(x)Fe(2)Se(2) (A=K,Cs) with a superconducting transition temperature (Tc) of about 30 K. We found A(x)Fe(2)Se(2) (A=K,Cs) is the most heavily electron-doped among all iron-based superconductors. Large electron Fermi surfaces are observed around the zone corners, with an almost isotropic superconducting gap of ~10.3 meV, whereas there is no hole Fermi surface near the zone centre, which demonstrates that interband scattering or Fermi surface nesting is not a necessary ingredient for the unconventional superconductivity in iron-based superconductors. Thus, the sign change in the s(±) pairing symmetry driven by the interband scattering as suggested in many weak coupling theories becomes conceptually irrelevant in describing the superconducting state here. A more conventional s-wave pairing is probably a better description.

Electronic-structure-driven magnetic and structure transitions in superconducting NaFeAs single crystals measured by angle-resolved photoemission spectroscopy

The electronic structure of NaFeAs is studied with angle-resolved photoemission spectroscopy on high quality single crystals. Large portions of the band structure start to shift around the structural transition temperature and smoothly evolve as the temperature lowers through the spin density wave transition. Moreover, band folding due to magnetic order emerges slightly above the structural transition. Our observation provides direct evidence that the structural and magnetic transitions share the same origin and could both be driven by the electronic structure reconstruction in Fe-based superconductors instead of Fermi surface nesting. We did not observe any sign of a gap in the superconducting state, which is likely related to weakened superconductivity in the presence of the spin density wave.

Out-of-plane momentum and symmetry-dependent energy gap of the pnictide Ba0.6K0.4Fe2As2 superconductor revealed by angle-resolved photoemission spectroscopy

The three-dimensional band structure and superconducting gap of Ba0.6K0.4Fe2As2 are studied with angle-resolved photoemission spectroscopy. In contrast with previous results, we have identified three holelike Fermi surface sheets near the zone center with sizable out-of-plane or kz dispersion. The superconducting gap on certain Fermi surface sheets shows significant kz dependence. Moreover, the superconducting gap sizes are different at the same Fermi momentum for two bands with different spatial symmetries (one odd, one even). Our results further reveal the three-dimensional and orbital-dependent structure of the superconducting gap in iron pnictides, which facilitates the understanding of momentum-integrated measurements and provides a distinct test for theories.

Novel chemoradiosensitizers for cancer therapy

Combined modality therapy using both chemotherapy and radiation has proved superior over radiation therapy alone for a variety of cancer types. While the locoregional control and survival benefits have been established, there is still much room for improvement both in terms of cancer control and normal tissue toxicity, i.e. the therapeutic ratio. Recently, the pace of research and development of both conventional cytotoxic and molecularly targeted radiosensitizers has been staggering. The aim of this paper is to bring the reader up to date on the clinical status of four promising new radiosensitizers: novel camptothecin analogs and inhibitors of poly(ADP-ribose) polymerase, histone deacetylase, and heat-shock protein 90.

Enhancement of radiation-induced DNA damage and inhibition of its repair by a novel camptothecin analog

A novel camptothecin derivative (TLC388) with higher efficacy and reduced toxicity has been synthesized and tested as a novel chemoradiosensitizing agent. This study investigated the mechanisms of the chemoradiosensitizing effects of TLC388 on H23 human non-small cell lung cancer (NSCLC) cells. Using the TUNEL assay, a significantly higher percentage of apoptotic cells was observed in the group treated with TLC388 plus X-ray radiation than those in groups treated with drug or radiation alone. The sensitizer enhancement ratio (SER) was 1.91. Apoptosis increased with drug concentration and radiation dose, exhibiting dose-dependent pattern. The results suggested that apoptosis could be a main mode of cell death that might underlie the increased chemoradio-sensitization of TLC388. Treatment with 30 nM of TLC388 plus 4 Gy X-ray also produced up to 42% of necrotic cells that were measured by trypan blue exclusion assay, but with TLC388 alone or 4 Gy radiation alone 9.8% or 11.1% necrotic cells were detected, respectively. An immunofluorescent staining method was employed to determine the levels of gamma-H2AX (phosphorylated H2AX, a variant of the H2A protein family, which is a component of the histone octomer in nucleosomes and is phosphorylated by kinases like ATM and ATR in the PI3K pathway, as the first step in recruiting and localizing DNA repair proteins) as a molecular biomarker of DNA double strand breaks (DSBs) in cells treated with TLC388 +/-radiation, or radiation alone. The formation of gamma-H2AX foci was observed after TLC388 or radiation exposure and when the cells were treated with 30 nM TLC388 plus radiation at a dose of 2 Gy, the percentage of cells containing gamma-H2AX foci increased significantly. Even more interesting, a markedly higher percentage (65.4%) of mitotic cells displayed gamma-H2AX foci after treatment with 30 nM TLC388 plus 0.5 Gy radiation, compared to only 5.9% or 26.1% of the M-phase cells treated with 30 nM TLC388 alone or 0.5 Gy radiation alone, respectively. It is suggested that mitotic cells become very sensitive to the production of DSBs after TLC388-radiation combined treatment and the formation of DSBs is strongly suggested to lead to the induction of apoptosis at doses lower than 4 Gy and to some necrosis at doses of 4 Gy or above. TLC388 enhances the production of DSBs and inhibits their repair, which contributes to the elucidation of the mechanisms of chemoradiosensitization of TLC388 and its development as a novel chemoradiosensitizing drug for improved radiotherapy.

Electronic structure and unusual exchange splitting in the spin-density-wave state of the BaFe2As2 parent compound of iron-based superconductors

The magnetic properties in the parent compounds are often intimately related to the microscopic mechanism of superconductivity. Here we report the first direct measurements on the electronic structure of a parent compound of the newly discovered iron-based superconductor, BaFe2As2, which provides a foundation for further studies. We show that the energy of the spin density wave in BaFe2As2 is mainly lowered through exotic exchange splitting of the band structure.

Primary role of the barely occupied states in the charge density wave formation of NbSe2

NbSe2 is a prototypical charge-density-wave (CDW) material, whose mechanism remains mysterious so far. With angle resolved photoemission spectroscopy, we recovered the long-lost nesting condition over a large broken-honeycomb region in the Brillouin zone, which consists of six saddle band point regions with high density of states (DOS), and large regions away from Fermi surfaces with negligible DOS at the Fermi energy. We show that the major contributions to the CDW formation come from these barely occupied states rather than the saddle band points. Our findings not only resolve a long-standing puzzle, but also overthrow the conventional wisdom that CDW is dominated by regions with high DOS.

Surgical treatment of esophageal leiomyoma located near or at the esophagogastric junction via a thoracoscopic approach

Esophageal leiomyoma can be enucleated safely and effectively by minimally invasive surgery. The laparoscopic approach has been a conventional option for this kind of tumor located near or at the esophagogastric (EG) junction. The aims of this study were to evaluate the surgical outcome of thoracoscopic resection of leiomyoma at the EG junction, and discuss factors affecting the incidence of postoperative gastroesophageal reflux. Fourteen patients who underwent thoracoscopic resection of esophageal leiomyoma located near or at the EG junction (<4 cm above the esophageal hiatus) from January 2002 to August 2007 were reviewed retrospectively. Tumor characteristics, surgical methods, and postoperative outcomes were evaluated. A left approach of video-assisted thoracoscopy was used in 13 patients; a right approach was used for the other patient, whose multiple tumors were located in the EG junction and mid-esophagus. Postoperative recovery was uneventful in all patients, with no mucosa leakage or other significant complications. Mean tumor size was 3.2 cm (1.2-6.0 cm). Of the 14 patients, two had serpiginous leiomyoma, two had multiple tumors, and the others had solitary tumors. Mean postoperative stay in hospital was 7 days (4-11 days). Postoperative dysphagia was not reported, although gastroesophageal reflux was noted in one patient. Thoracoscopic resection of esophageal leiomyomas near or at the EG junction is feasible, with a low prevalence of postoperative gastroesophageal reflux.