ROS Induction Targets Persister Cancer Cells with Low Metabolic Activity in NRAS-Mutated Melanoma

Clinical management of melanomas with NRAS mutations is challenging. Targeting MAPK signaling is only beneficial to a small subset of patients due to resistance that arises through genetic, transcriptional, and metabolic adaptation. Identification of targetable vulnerabilities in NRAS-mutated melanoma could help improve patient treatment. Here, we used multiomics analyses to reveal that NRAS-mutated melanoma cells adopt a mesenchymal phenotype with a quiescent metabolic program to resist cellular stress induced by MEK inhibition. The metabolic alterations elevated baseline reactive oxygen species (ROS) levels, leading these cells to become highly sensitive to ROS induction. In vivo xenograft experiments and single-cell RNA sequencing demonstrated that intratumor heterogeneity necessitates the combination of a ROS inducer and a MEK inhibitor to inhibit both tumor growth and metastasis. Ex vivo pharmacoscopy of 62 human metastatic melanomas confirmed that MEK inhibitor-resistant tumors significantly benefited from the combination therapy. Finally, oxidative stress response and translational suppression corresponded with ROS-inducer sensitivity in 486 cancer cell lines, independent of cancer type. These findings link transcriptional plasticity to a metabolic phenotype that can be inhibited by ROS inducers in melanoma and other cancers.

SIGNIFICANCE

Metabolic reprogramming in drug-resistant NRAS-mutated melanoma cells confers sensitivity to ROS induction, which suppresses tumor growth and metastasis in combination with MAPK pathway inhibitors.

Molecular alterations in bone marrow mesenchymal stromal cells derived from acute myeloid leukemia patients

The contribution of molecular alterations in bone marrow mesenchymal stromal cells (BM-MSC) to the pathogenesis of acute myeloid leukemia (AML) is poorly understood. Thus we assessed genome-wide genetic, transcriptional and epigenetic alterations in BM-MSC derived from AML patients (AML BM-MSC). Whole-exome sequencing (WES) of AML BM-MSC samples from 21 patients revealed a non-specific pattern of genetic alterations in the stromal compartment. The only mutation present in AML BM-MSC at serial time points of diagnosis, complete remission and relapse was a mutation in the PLEC gene encoding for cytoskeleton key player Plectin in one AML patient. Healthy donor controls did not carry genetic alterations as determined by WES. Transcriptional profiling using RNA sequencing revealed deregulation of proteoglycans and adhesion molecules as well as cytokines in AML BM-MSC. Moreover, KEGG pathway enrichment analysis unravelled deregulated metabolic pathways and endocytosis in both transcriptional and DNA methylation signatures in AML BM-MSC. Taken together, we report molecular alterations in AML BM-MSC suggesting global changes in the AML BM microenvironment. Extended investigations of these altered niche components may contribute to the design of niche-directed therapies in AML.

Histology of the bone-cement interface in retrieved Oxford unicompartmental knee replacements

INTRODUCTION

Radiolucent lines (RLL) are commonly seen at the cement-bone interface of knee replacements, yet are poorly understood. Although thin RLL are not associated with implant loosening or poor patient outcome there is still concern that they indicate sub-optimal fixation. The primary study aim is to characterise the histology at the cement-tibia interface in Oxford unicompartmental knee replacement (UKR). The second aim is to assess whether a correlation exists between the presence of a RLL and the type of tissue that predominates at the interface.

METHODS

The radiology and histology of retrieved specimens of the interface from around firmly fixed tibial trays in ten patients undergoing revision between 1 and 19 years after Oxford UKR were studied.

RESULTS

Pre-revision radiographs showed the presence of both full and partial RLL. On contact radiographs of 5mm thick sections of the interface the total percentage of radiolucency ranged from 0 to 90% between patients. There was no consistent pattern for the distribution of radiolucency. Histological assessment demonstrated that under every tibial component there were areas where there was direct contact and interdigitation between bone and cement. The amount of direct bone-cement contact was between 19% and 95% of the tibial tray surface area. The remaining tissue was mainly fibrocartilage but there was also fibrous tissue. The presence of radiolucency was strongly inversely correlated with the percentage of cement-bone contact.

CONCLUSION

This study demonstrates that even with partial or complete RLL seen on radiographs there is still cement-bone contact, thus indicating that there is stable fixation.

The effect of high energy mechanochemical processing on the microstructure, piezoelectric, ferroelectric and mechanical properties of PLZT ceramics

Lead lanthanum zirconate titanate (PLZT) ceramics were synthesized using a high energy mechanochemical processing technique, using tungsten carbide grinding vials and balls. The ceramic powders were prepared using the constituent oxide powders, which were subjected to high energy milling, without the use of any excess PbO in the starting composition. TEM studies revealed the formation of very fine particles of the order of 30 nm, due to the milling effect. Highly dense ceramics could be prepared via sintering which resulted in ultra-high strains in these piezoelectric samples of up to 0.25%, a value which has not been reported hitherto by any other known process. The effect of the reduction in particle size on the microstructure, mechanical and electrical properties of PLZT ceramics were studied and are discussed herein.

Androgenesis from Festuca pratensis x Lolium multiflorum amphidiploid cultivars in order to select and stabilize rare gene combinations for grass breeding

Androgenesis using amphidiploid cultivars of Festuca pratensis x Lolium multiflorum as parents, overcame earlier problems that gave rise to widespread plant sterility amongst androgenic Festulolium populations. Two Festuca pratensis x Lolium multiflorum (2n = 4x = 28) cultivars, Sulino and Felopa, were highly amenable to androgenesis and 10% of plants, including some novel androgenic genotypes, had sufficient fertility to produce progeny and further generations. The genomes of amphidiploid cultivars, which represent the F8 generation, were the result of considerable intergeneric chromosome recombination. Moreover, during cultivar development, natural and breeders' selection pressures had led to the assembly of gene combinations that conferred good growth characters and fertility with the removal of putative deleterious gene combinations. Over 80% of the androgenic plants derived from the amphidiploid F. pratensis x L. multiflorum (2n = 4x = 28) had 14 chromosomes and were likely to be dihaploids with a single genome of Lolium and of Festuca. In contrast, hybrids of F. pratensis x L. multiflorum (2n = 2x = 14) found naturally are invariably sterile. Structural reorganization within the genomes of the androgenic Festulolium plants had restored fertility in genotypes expected to contain the haploid genome of Lolium and Festuca. This provided opportunities for their future incorporation in breeding programmes and the development of fertile diploid Lolium-Festuca hybrids. Amongst the androgenic plants, Festulolium genotypes were recovered that conferred excellent drought resistance or freezing tolerance and were thought to be highly suitable for entry into plant breeding programmes.

Effect of hyperinsulinaemia on the function of the pituitary-adrenal axis in healthy man

OBJECTIVE

Circulating insulin levels in themselves have been reported to influence the counter-regulatory hormone response to hypoglycaemia in man. The effect of insulin on a specific aspect of this response was examined during euglycaemia by stimulating the pituitary-adrenal axis with human corticotrophin-releasing hormone (CRH).

SUBJECTS

Eight healthy males.

DESIGN

Following an overnight fast, insulin was infused at 15 (low) and 60 (high) mU/kg/h from 0900 h for 180 minutes on separate occasions in random order. On each occasion, blood glucose was clamped at euglycaemia, and 1 microgram/kg (i.v. bolus) human CRH was administered at 120 minutes.

MEASUREMENTS

Circulating hormone concentrations were determined by radioimmunoassay. Peak cortisol and ACTH responses were compared for the two study conditions.

RESULTS

Mean serum insulin levels were threefold higher during the high compared with the low insulin infusion (mean difference 320 pmol/l, 95% confidence interval (CI) 150-490, P < 0.001). Blood glucose levels during the clamps were comparable (mean difference 0.15 mmol/l, 95% CI 0-0.63). Plasma cortisol levels increased following CRH, although the peak concentration was significantly lower during the high insulin infusion (mean difference 36 nmol/l, CI 0-110, P < 0.02). However, peak ACTH levels were comparable for the two insulin levels (mean difference 8 ng/l (1.8 pmol/l), CI 0-50).

CONCLUSIONS

The peak cortisol response to CRH was diminished at the higher circulating insulin levels. This was not dependent upon concurrent hypoglycaemia and did not appear to be mediated at the level of the pituitary gland.

Herpes simplex virus encephalitis during childhood: importance of brain biopsy diagnosis

Twelve consecutive pediatric patients 1 day to 11 years of age with suspected herpes simplex virus (HSV) encephalitis underwent brain biopsy. Five were proved to have HSV encephalitis; seven had subdural empyema, malignant glioma, enteroviral encephalitis, (one each), and presumed viral encephalitis, non-HSV (four). Neither epidemiologic, clinical, nor noninvasive laboratory tests were able to help differentiate the two groups of patients. The EEG was more sensitive than the CT scan in demonstrating focal lesions in early HSV encephalitis. In patients with HSV encephalitis, the mean time from hospital admission to appropriate antiviral chemotherapy was 3 days, and the outcome of HSV encephalitis was uniformly poor. In patients with febrile encephalitis-like syndromes with CSF pleocytosis, focal neurologic signs, or other localizing test results (EEG, CT), anticipatory antiviral chemotherapy and brain biopsy are the only hope to prevent the poor outcome associated with HSV encephalitis, to exclude other treatable conditions, and to avoid multiple types of unnecessary empiric therapies.