No abstract

3D Dirac semimetals are an emerging class of materials that possess topological electronic states with a Dirac dispersion in their bulk. In nodal-line Dirac semimetals, the conductance and valence bands connect along a closed path in momentum space, leading to the prediction of pseudospin vortex rings and pseudospin skyrmions. Here, we use Fourier transform scanning tunneling spectroscopy (FT-STS) at 4.5 K to resolve quasiparticle interference (QPI) patterns at single defect centers on the surface of the line nodal semimetal zirconium silicon sulfide (ZrSiS). Our QPI measurements show pseudospin conservation at energies close to the line node. In addition, we determine the Fermi velocity to be ℏv = 2.65 ± 0.10 eV Å in the Γ-M direction ∼300 meV above the Fermi energy E and the line node to be ∼140 meV above E. More importantly, we find that certain scatterers can introduce energy-dependent nonpreservation of pseudospin, giving rise to effective scattering between states with opposite pseudospin deep inside valence and conduction bands. Further investigations of quasiparticle interference at the atomic level will aid defect engineering at the synthesis level, needed for the development of lower-power electronics via dissipationless electronic transport in the future.

No abstract

Recent reports of a large anomalous Hall effect (AHE) in ferromagnetic Weyl semimetals (FM WSMs) have led to a resurgence of interest in this enigmatic phenomenon. However, due to a lack of tunable materials, the interplay between the intrinsic mechanism caused by Berry curvature and extrinsic mechanisms due to scattering remains unclear in FM WSMs. In this contribution, we present a thorough investigation of both the extrinsic and intrinsic AHEs in a new family of FM WSMs, PrAlGe1−xSix, where x can be tuned continuously. Based on the first-principles calculations, we show that the two end members, PrAlGe and PrAlSi, have different Fermi surfaces, but similar Weyl node structures. Experimentally, we observe moderate changes in the anomalous Hall coefficient (RS), but significant changes in the ordinary Hall coefficient (R0) in PrAlGe1−xSix as a function of x. By comparing the magnitude of R0 and RS, we identify two regimes: |R0| < |RS| for x ≤ 0.5 and |R0| > |RS| for x > 0.5. Through a detailed scaling analysis, we uncover a universal anomalous Hall conductivity (AHC) from intrinsic contribution when x ≤ 0.5. Such a universal AHC is absent for x > 0.5. Our study, thus, reveals the significance of extrinsic mechanisms in FM WSMs and reports the first observation of the transition from the intrinsic to extrinsic AHE in PrAlGe1−xSix.

Background/Aims: Colorectal cancer (CRC) is the third most common type of cancer and the second leading cause of cancer-related deaths worldwide. PRDXs are antioxidant enzymes that play an important role in cell differentiation, proliferation and apoptosis and have diverse functions in malignancy development. However, the mechanism of aberrant overexpression of PRDX6 in CRC remains unclear. Methods: Boyden chamber assay, flow cytometry and a lentiviral shRNA targeting PRDX6 and transient transfection with pCMV-6-PRDX6 plasmid were used to examine the role of PRDX6 in the proliferation capacity and invasiveness of CRC cells. Immunohistochemistry (IHC) with tissue array containing 40 paraffin- embedded CRC tissue specimens and Western blot assays were used to detect target proteins. Results: PRDX6 was significantly up-expressed in different comparisons of metastasis of colorectal adenomas in node-positive CRC (P = 0.03). In in vitro HCT-116, PRDX6 silencing markedly suppressed CRC cell migration and invasiveness while also inducing cell cycle arrest as well as the generation of reactive oxygen species (ROS); specific overexpression of PRDX6 had the opposite effect. Mechanistically, the PRDX6 inactivation displayed decreased levels of PRDX6, N-cadherin, β-catenin, Vimentin, Slug, Snail and Twist-1 through the activation of the PI3K/ AKT/p38/p50 pathways, but they were also significantly inhibited by PRDX6 transfectants. There was also increased transcriptional activation of dimethylation of histone H3 lysine 4 (H3K4me3) of PRDX6 promoter via the activation of the PI3K/Akt/NFkB pathways. Conclusion: Our findings demonstrated that PRDX6 expression plays a characteristic growth-promoting role in CRC metastasis. This study suggests that PRDX6 may serve as a biomarker of node-positive status and may have a role as an important endogenous regulator of cancer cell tumorigenicity in CRC. PRDX6 may also be an effective therapeutic target.

Erinacine A, a major active component of a diterpenoid derivative isolated from Hericium erinaceus mycelium, has been demonstrated to exert anticancer effects. Herein, we present an investigation of the molecular mechanism of erinacine A induction associated with cancer cells’ aggressive status and death. A proteomic approach was used to purify and identify the differentially expressed proteins following erinacine A treatment and the mechanism of its action in apoptotic and the targets of erinacine A. Our results demonstrate that erinacine A treatment of HCT‐116 and DLD‐1 cells increased cell cytotoxicity and reactive oxygen species (ROS) production as well as decreased cell proliferation and invasiveness. Ten differentially displayed proteins were determined and validated in vitro and in vivo between the erinacine A‐treated and untreated groups. In addition, erinacine A time‐dependent induction of cell death and inhibitory invasiveness was associated with sustained phosphorylation of the PI3K/mTOR/p70S6K and ROCK1/LIMK2/Cofilin pathways. Furthermore, we demonstrated that erinacine A–induced HCT‐116 and DLD‐1 cells viability and anti‐invasion properties by up‐regulating the activation of PI3K/mTOR/p70S6K and production of ROS. Experiments involving specific inhibitors demonstrated that the differential expression of cofilin‐1 (COFL1) and profilin‐1 (PROF1) during erinacine A treatment could be involved in the mechanisms of HCT‐116 and DLD‐1 cells death and decreased aggressiveness, which occurred via ROCK1/LIMK2/Cofilin expression, with activation of the PI3K/mTOR/p70S6K signalling pathway. These findings elucidate the mechanism of erinacine A inhibiting the aggressive status of cells by activating PI3K/mTOR/p70S6K downstream signalling and the novel protein targets COF1 and PROF1; this could be a good molecular strategy to limit the aggressiveness of CRC cells.

CIL-102 (1-[4-(furo[2,3-b]quinolin-4-ylamino)phenyl]ethanone) is a well-known, major active agent of the alkaloid derivative of Camptotheca acuminata with valuable biological properties, including anti-tumorigenic activity. In this study, we investigated the molecular mechanisms by which CIL-102 mediated the induction of cell death, and we performed cell cycle G2/M arrest to clarify molecular changes in colorectal cancer cells (CRC). Treatment of DLD-1 cells with CIL-102 resulted in triggering the extrinsic apoptosis pathway through the activation of Fas-L, caspase-8 and the induction of Bid cleavage and cytochrome c release in a time-dependent manner. In addition, CIL-102 mediated apoptosis and G2/M arrest by phosphorylation of the Jun N-terminus kinase (JNK1/2) signaling pathway. This resulted in the expression of NFκB p50, p300 and CREB-binding protein (CBP) levels, and in the induction of p21 and GADD45 as well as the decreased association of cdc2/cyclin B. Furthermore, treatment with the JNK1/2 (SP600125), NFκB (PDTI) or the p300/CBP (C646) inhibitors abolished CIL-102-induced cell cycle G2/M arrest and reversed the association of cdc2 with cyclin B. Therefore, we demonstrated that there was an increase in the cellular levels of p21 and GADD45 by CIL-102 reduction in cell viability and cell cycle arrest via the activation of the JNK1/2, NFκB p50, p300 and CBP signaling modules. Collectively, our results demonstrated that CIL-102 induced cell cycle arrest and apoptosis of colon cancer cells by upregulating p21 and GADD45 expression and by activating JNK1/2, NFκB p50 and p300 to provide a new mechanism for CIL-102 treatment.

Background / Aims: Erinacine A, isolated from the ethanol extract of the Hericium erinaceus mycelium, has been demonstrated as a new alternative anticancer medicine. Drawing upon current research, this study presents an investigation of the molecular mechanism of erinacine A inhibition associated with gastric cancer cell growth. Methods: Cell viability was determined by Annexin V–FITC/propidium iodide staining and migration using a Boyden chamber assay to determine the effects of erinacine A treatment on the proliferation capacity and invasiveness of gastric cancer cells. A proteomic assay provided information that was used to identify the differentially-expressed proteins following erinacine A treatment, as well as the mechanism of its targets in the apoptotic induction of erinacine A. Results: Our results demonstrate that erinacine A treatment of TSGH 9201 cells increased cytotoxicity and the generation of reactive oxygen species (ROS), as well as decreased the invasiveness. Treatment of TSGH 9201 cells with erinacine A resulted in the activation of caspases and the expression of TRAIL. Erinacine A induction of apoptosis was accompanied by sustained phosphorylation of FAK/AKT/p70S6K and the PAK1 pathways, as well as the generation of ROS. Furthermore, the induction of apoptosis and anti-invasion properties by erinacine A could involve the differential expression of the 14-3-3 sigma protein (1433S) and microtubule-associated tumor suppressor candidate 2 (MTUS2), with the activation of the FAK/AKT/p70S6K and PAK1 signaling pathways. Conclusions: These results lead us to speculate that erinacine A may generate an apoptotic cascade in TSGH 9201 cells by activating the FAK/AKT/p70S6K/PAK1 pathway and upregulating proteins 1433S and MTUS2, providing a new mechanism underlying the anti-cancer effects of erinacine A in human gastric cancer cells.