Treatment of hepatic amyloid light‐chain amyloidosis with bortezomib and dexamethasone in a liver transplant patient

Hepatic amyloid light‐chain (AL) amyloidosis is characterized by abnormal deposition of amyloid fibrils in the liver. As this precursor protein is produced by a proliferative plasma cell clone in the bone marrow, liver transplantation (LT) does not affect the disease's progression. Here, we describe the successful treatment using bortezomib‐ and dexamethasone‐based chemotherapy, following LT, of hepatic AL amyloidosis in a 65‐year‐old woman with progressive liver failure. The patient presented with progressive hepatic dysfunction accompanied by hepatorenal syndrome requiring hemodialysis, and living donor LT was successfully performed. Histology revealed amyloid deposits in the liver and stomach, and serum immunofixation revealed AL amyloidosis (κ‐type). The patient began chemotherapy on day 45 after the LT, and remission was achieved after one course. She was subsequently discharged 83 days after the LT, with normal liver and renal function, and no clinical evidence of recurrent disease was observed at the latest follow up (22 months post‐LT).     

Structure and dynamics of SARS-CoV-2 proofreading exoribonuclease ExoN

High-fidelity replication of the large RNA genome of coronaviruses (CoVs) is mediated by a 3′-to-5′ exoribonuclease (ExoN) in nonstructural protein 14 (nsp14), which excises nucleotides including antiviral drugs misincorporated by the low-fidelity viral RNA-dependent RNA polymerase (RdRp) and has also been implicated in viral RNA recombination and resistance to innate immunity. Here, we determined a 1.6-Å resolution crystal structure of severe acute respiratory syndrome CoV 2 (SARS-CoV-2) ExoN in complex with its essential cofactor, nsp10. The structure shows a highly basic and concave surface flanking the active site, comprising several Lys residues of nsp14 and the N-terminal amino group of nsp10. Modeling suggests that this basic patch binds to the template strand of double-stranded RNA substrates to position the 3′ end of the nascent strand in the ExoN active site, which is corroborated by mutational and computational analyses. We also show that the ExoN activity can rescue a stalled RNA primer poisoned with sofosbuvir and allow RdRp to continue its extension in the presence of the chain-terminating drug, biochemically recapitulating proofreading in SARS-CoV-2 replication. Molecular dynamics simulations further show remarkable flexibility of multidomain nsp14 and suggest that nsp10 stabilizes ExoN for substrate RNA binding to support its exonuclease activity. Our high-resolution structure of the SARS-CoV-2 ExoN–nsp10 complex serves as a platform for future development of anticoronaviral drugs or strategies to attenuate the viral virulence.

The 29.9-kb single-stranded RNA genome of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of the global COVID-19 pandemic, is replicated and transcribed by the viral RNA-dependent RNA polymerase (RdRp, nsp12) (1–3). Unlike the high-fidelity cellular replicative DNA polymerases, viral RdRp enzymes, including the CoV RdRp, do not contain a proofreading exonuclease domain to ensure high fidelity. The resulting higher mutation rate (10⁻⁴ to 10⁻⁶ substitutions per nucleotide per round of replication) is generally thought to promote rapid viral adaptation in response to selective pressure (4–6). However, the lack of proofreading activity in RdRp poses a particular challenge for the replication of CoVs, which feature the largest known RNA virus genomes (27 to 32 kb, up to twice the length as the next-largest nonsegmented RNA viral genomes) (7, 8). It has been reported that SARS-CoV nsp12 is the fastest viral RdRp known but with an error rate more than one order of magnitude higher than the generally admitted error rate of viral RdRps (9), clearly necessitating a unique proofreading mechanism.To mitigate the low fidelity of RdRp, all coronaviruses encode a 3′-to-5′ exoribonuclease (ExoN) in multifunctional nsp14 (10–12), which forms a complex with nsp10 critical for the ExoN activity, and additionally contains a C-terminal guanine N7 methyl transferase (N7-MTase) domain. Mutations of SARS-CoV-2 nsp14 exhibit strong association with increased genome-wide mutation load (13, 14), and genetic inactivation of ExoN in engineered SARS-CoV and murine hepatitis virus (MHV) leads to 15- to 20-fold increases in mutation rates (7, 15, 16). Furthermore, in a mouse model, SARS-CoV with inactivated ExoN shows a mutator phenotype with decreased fitness and lower virulence over serial passage, suggesting a potential strategy for generating a live, impaired-fidelity coronavirus vaccine (17). Alternatively, recent studies show that ExoN inactivation abrogates replication of SARS-CoV-2 and Middle East Respiratory Syndrome CoV (18), hinting at additional functions for ExoN in viral replication. Indeed, ExoN activity has been reported to mediate the extensive viral RNA recombination required for subgenomic messenger RNA (mRNA) synthesis during normal replication of CoVs, including SARS-CoV-2 (19), and it was shown to be required for resistance to the antiviral innate immune response for MHV (20). ExoN inactivation also significantly increases the sensitivity of CoVs to nucleoside analogs that target RdRp, which is consistent with the biochemical activity of ExoN to excise mutagenic or chain-terminating nucleotides misincorporated by RdRp (21–23). These observations combine to suggest that chemical inhibition of ExoN could be an effective antiviral strategy against CoVs. In this study, we determined high-resolution crystal structures of the SARS-CoV-2 ExoN–nsp10 complex and studied its biochemical activities. Furthermore, we used molecular dynamics (MD) simulations to better understand the dynamics of nsp14, nsp10, and their interaction with RNA.     

Outcomes of outpatient breast cancer surgery at a private breast clinic

Advances in surgical and anesthetic techniques have allowed for outpatient treatment of breast cancer. We evaluated the feasibility, safety, efficacy, and surgical outcomes of outpatient surgery in 370 patients with breast cancer who underwent breast‐conserving surgery (BCS)/axillar lymph node (ALN) management. There were no deaths or severe intraoperative complications, but 41 complications were observed and disease recurrence occurred in 18 patients. The cumulative overall survival rate was 95.2%. Outpatient surgery was well tolerated, feasible, and safe in patients receiving BCS/ALN management.     

Rho-Associated Kinase Inhibitor Reduces Tumor Recurrence After Liver Transplantation in a Rat Hepatoma Model

Tumor recurrence after liver transplantation still remains a significant problem in patients with hepatocellular carcinoma. The small GTPase Rho/Rho-associated kinase (ROCK) pathway is involved in the motility and invasiveness of cancer cells. We investigated whether tacrolimus activated the Rho/ROCK signal pathway to promote the invasiveness of rat hepatocellular carcinoma cells. We also investigated whether the ROCK inhibitor Y-27632 suppressed tumor recurrence after experimental liver transplantation in a rat hepatocellular carcinoma model. Orthotopic liver transplantation was performed in hepatocellular carcinoma cell line McA-RH7777-bearing rats. Tacrolimus was administered to liver transplant rats and these rats were divided into two groups: the Y-27632-treated (10 mg/kg, for 28 days) group and the Y-27632-untreated group. Tacrolimus enhanced the cancer cell migration and stimulated phosphorylation of the myosin light chain (MLC), a downstream effector of Rho/ROCK signaling. Y-27632 suppressed the cancer cell migration and tacrolimus-induced MLC phosphorylation. Suppression of tumor recurrence after liver transplantation and significant prolongation of survival were observed in the Y-27632-treated rats in comparison with theY-27632-untreated rats. Tacrolimus stimulates the Rho/ROCK signal pathway to enhance the invasiveness of hepatocellular carcinoma, and the ROCK inhibitor Y-27632 can be used as a new antimetastatic agent for the prevention of tumor recurrence after liver transplantation.     

Ossification of the ligamentum flavum of the thoracic spine in adult kyphosis

Summary Ossification of the ligamentum flavum has been recognised as a definite clinical entity as is ossification of the posterior longitudinal ligament. The incidence of both is high in Japan. This study demonstrates that the incidence of ossification of the ligamentum flavum in persons who have a kyphosis of the thoracic or lumbar spine is higher than in those who do not. It is considered that localised mechanical stress affecting the ligamentum flavum is a contributing factor to the development of ossification, together with the generalised factors which may favour bone formation. However, the aetiology of this lesion is still obscure as is that of ossification of the posterior longitudinal ligament.

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Résumé L'ossification du ligament jaune représente une entité clinique définie, de même que celle du ligament longitudinal postérieur. Les deux affections sont fréquentes au Japon. Cette étude montre que l'ossification du ligament jaune s'observe plus souvent chez les sujets qui présentent une cyphose dorsale ou lombaire. On peut penser que les contraintes mécaniques localisées au ligament jaune constituent un facteur contribuant au développement de l'ossification, et s'ajoutant aux facteurs généraux susceptibles de favoriser la formation osseuse. Cependant, l'étiologie de cette affection demeure mystérieuse de même que l'ossification du ligament longitudinal postérieur.

     

Laparoscopy-assisted proximal gastrectomy with gastric tube reconstruction for early gastric cancer

Background  

In this report, laparoscopy-assisted proximal gastrectomy (LAPG) and gastric tube reconstruction using a mini-loop retractor (MLR) is described for the treatment of early gastric cancer.     

Idiopathic sustained left ventricular tachycardia: clinical and electrophysiologic characteristics

Electrophysiologic studies were performed in 16 patients 11 to 45 years old (mean 33 years) with idiopathic sustained (lasting more than 5 min) ventricular tachycardia (VT) originating from the left ventricle. Endocardial mapping during VT showed that the earliest site of activation was at the apical inferior portion of the left ventricle in 14 patients whose QRS morphology during VT showed a right bundle branch block pattern and left-axis deviation, but at the apical anterosuperior portion of the left ventricle in two patients whose QRS morphology during VT showed a right bundle branch block and right-axis deviation. Single programmed ventricular stimulation induced VT in 13 patients, and rapid ventricular pacing induced VT in the remaining three patients. Rapid ventricular pacing terminated VT in all patients. The relationship between the coupling interval and the echo interval was inverse in all eight patients with a wide VT inducible zone. Entrainment was recognized in three of six patients. The initiation of VT by constant pacing depended on the number of pacing beats but not the duration of pacing in all four patients tested. Intravenous verapamil terminated the VT in 13 of 14 patients. Long-term oral verapamil was also effective in all five patients who required long-term oral therapy for their symptoms associated with VT. In conclusion (1) idiopathic left ventricular tachycardia has unique electrocardiographic, electrophysiologic, and electropharmacological properties, (2) the electrophysiologic characteristics suggest that the mechanism is reentry, and (3) verapamil is effective in both the short- and long-term treatment of VT.     

Progression of Renal Dysfunction in Patients with Cardiovascular Disease

It has been established that patients with chronic kidney disease (CKD) suffer from frequent cardiovascular events. On the other hand, recent studies suggest that renal damage tends to worsen in patients with cardiovascular diseases (CVD). Although the mechanisms for the cardiorenal association are unclear, the presence of arteriosclerotic risk factors common to both CVD and CKD is important. In arteriosclerosis, vascular derangement progresses not only in the heart but also in the kidney. In addition, heart failure, cardiac catheterization and hesitation of medical treatments due to renal dysfunction may explain the progression of renal damage. Therefore, the goal of treatments is a total control of arteriosclerotic risk factors. Medication should be selected among agents with protective effects on both heart and kidney. It is important to always consider the presence of CKD for the treatment of the cardiovascular disease and strictly control the risk factors.Key Words: CKD, angiotensin II, aldosterone, ARB, hypertension.