Bispectral Index Changes Following Boluses of Commonly Used Intravenous Medications During Volatile Anesthesia Identified From Retrospective Data

BACKGROUND

Although patients are commonly monitored for depth of anesthesia, it is unclear to what extent administration of intravenous anesthetic medications may affect calculated bispectral (BIS) index values under general anesthesia.

METHODS

In a retrospective analysis of electronic anesthesia records from an academic medical center, we examined BIS index changes associated with 14 different intravenous medications, as administered in routine practice, during volatile-based anesthesia using a novel screening approach. Discrete-time windows were identified in which only a single drug bolus was administered, and subsequent changes in the BIS index, concentration of volatile anesthetic, and arterial pressure were analyzed. Our primary outcome was change in BIS index, following drug administration. Adjusted 95% confidence intervals were compared to predetermined thresholds for clinical significance. Secondary sensitivity analyses examined the same outcomes, with available data separated according to differences in baseline volatile anesthetic concentrations, doses of the administered medications, and length of time window.

RESULTS

The study cohort was comprised of data from 20,170 distinct cases, 54.7% of patients were men, with a median age of 55. In the primary analysis, ketamine at a median dose of 20 mg was associated with a median (confidence limits) increase in BIS index of 3.8 (2.5-5.0). Midazolam (median dose 2 mg) was associated with a median decrease in BIS index of 3.0 (1.5-4.5). Neither of these drug administrations occurred during time periods associated with changes in volatile anesthetic concentration. Analysis for dexmedetomidine was confounded by concomitant decreases in volatile anesthetic concentration. No other medication analyzed, including propofol and common opioids, was associated with a significant change in BIS index. Secondary analyses revealed that similar BIS index changes occurred when midazolam and ketamine were administered at different volatile anesthetic concentrations and different doses, and these changes persisted 11 to 20 minutes postadministration.

CONCLUSIONS

Modest, but persistent changes in BIS index occurred following doses of ketamine (increase) and midazolam (decrease) during periods of stable volatile anesthetic administration.

LINC00152 Promotes Invasion through a 3'-Hairpin Structure and Associates with Prognosis in Glioblastoma

Long noncoding RNAs (lncRNA) are increasingly implicated in oncogenesis. Here, it is determined that LINC00152/CYTOR is upregulated in glioblastoma multiforme (GBM) and aggressive wild-type IDH1/2 grade 2/3 gliomas and upregulation associates with poor patient outcomes. LINC00152 is similarly upregulated in over 10 other cancer types and associates with a poor prognosis in 7 other cancer types. Inhibition of the mostly cytoplasmic LINC00152 decreases, and overexpression increases cellular invasion. LINC00152 knockdown alters the transcription of genes important to epithelial-to-mesenchymal transition (EMT). PARIS and Ribo-seq data, together with secondary structure prediction, identified a protein-bound 121-bp stem-loop structure at the 3' end of LINC00152 whose overexpression is sufficient to increase invasion of GBM cells. Point mutations in the stem-loop suggest that stem formation in the hairpin is essential for LINC00152 function. LINC00152 has a nearly identical homolog, MIR4435-2HG, which encodes a near identical hairpin, is equally expressed in low-grade glioma (LGG) and GBM, predicts poor patient survival in these tumors, and is also reduced by LINC00152 knockdown. Together, these data reveal that LINC00152 and its homolog MIR4435-2HG associate with aggressive tumors and promote cellular invasion through a mechanism that requires the structural integrity of a hairpin structure.Implications: Frequent upregulation of the lncRNA, LINC00152, in glioblastoma and other tumor types combined with its prognostic potential and ability to promote invasion suggests LINC00152 as a potential biomarker and therapeutic target. Mol Cancer Res; 16(10); 1470-82. ©2018 AACR.

Expression of lncRNAs in Low-Grade Gliomas and Glioblastoma Multiforme: An In Silico Analysis

BACKGROUND

Each year, over 16,000 patients die from malignant brain cancer in the US. Long noncoding RNAs (lncRNAs) have recently been shown to play critical roles in regulating neurogenesis and brain tumor progression. To better understand the role of lncRNAs in brain cancer, we performed a global analysis to identify and characterize all annotated and novel lncRNAs in both grade II and III gliomas as well as grade IV glioblastomas (glioblastoma multiforme [GBM]).

METHODS AND FINDINGS

We determined the expression of all lncRNAs in over 650 brain cancer and 70 normal brain tissue RNA sequencing datasets from The Cancer Genome Atlas (TCGA) and other publicly available datasets. We identified 611 induced and 677 repressed lncRNAs in glial tumors relative to normal brains. Hundreds of lncRNAs were specifically expressed in each of the three lower grade glioma (LGG) subtypes (IDH1/2 wt, IDH1/2 mut, and IDH1/2 mut 1p19q codeletion) and the four subtypes of GBMs (classical, mesenchymal, neural, and proneural). Overlap between the subtype-specific lncRNAs in GBMs and LGGs demonstrated similarities between mesenchymal GBMs and IDH1/2 wt LGGs, with 2-fold higher overlap than would be expected by random chance. Using a multivariate Cox regression survival model, we identified 584 and 282 lncRNAs that were associated with a poor and good prognosis, respectively, in GBM patients. We developed a survival algorithm for LGGs based on the expression of 64 lncRNAs that was associated with patient prognosis in a test set (hazard ratio [HR] = 2.168, 95% CI = 1.765-2.807, p < 0.001) and validation set (HR = 1.921, 95% CI = 1.333-2.767, p < 0.001) of patients from TCGA. The main limitations of this study are that further work is needed to investigate the clinical relevance of our findings, and that validation in an independent dataset is needed to determine the robustness of our survival algorithm.

CONCLUSIONS

This work identifies a panel of lncRNAs that appear to be prognostic in gliomas and provides a critical resource for future studies examining the role of lncRNAs in brain cancers.

Biological Processes Discovered by High-Throughput Sequencing

Advances in DNA and RNA sequencing technologies have completely transformed the field of genomics. High-throughput sequencing (HTS) is now a widely used and accessible technology that allows scientists to sequence an entire transcriptome or genome in a timely and cost-effective manner. Application of HTS techniques has led to many key discoveries, including the identification of long noncoding RNAs, microDNAs, a family of small extrachromosomal circular DNA species, and tRNA-derived fragments, which are a group of small non-miRNAs that are derived from tRNAs. Furthermore, public sequencing repositories provide unique opportunities for laboratories to parse large sequencing databases to identify proteins and noncoding RNAs at a scale that was not possible a decade ago. Herein, we review how HTS has led to the discovery of novel nucleic acid species and uncovered new biological processes during the course.

The lncRNA DRAIC/PCAT29 Locus Constitutes a Tumor-Suppressive Nexus

Long noncoding RNAs (lncRNA) are emerging as major regulators of cellular phenotypes and implicated as oncogenes or tumor suppressors. Here, we report a novel tumor-suppressive locus on human chromosome 15q23 that contains two multiexonic lncRNA genes of 100 kb each: DRAIC (LOC145837) and the recently reported PCAT29. The DRAIC lncRNA was identified from RNA-seq data and is downregulated as prostate cancer cells progress from an androgen-dependent (AD) to a castration-resistant (CR) state. Prostate cancers persisting in patients after androgen deprivation therapy (ADT) select for decreased DRAIC expression, and higher levels of DRAIC in prostate cancer are associated with longer disease-free survival (DFS). Androgen induced androgen receptor (AR) binding to the DRAIC locus and repressed DRAIC expression. In contrast, FOXA1 and NKX3-1 are recruited to the DRAIC locus to induce DRAIC, and FOXA1 specifically counters the repression of DRAIC by AR. The decrease of FOXA1 and NKX3-1, and aberrant activation of AR, thus accounts for the decrease of DRAIC during prostate cancer progression to the CR state. Consistent with DRAIC being a good prognostic marker, DRAIC prevents the transformation of cuboidal epithelial cells to fibroblast-like morphology and prevents cellular migration and invasion. A second tumor-suppressive lncRNA PCAT29, located 20 kb downstream of DRAIC, is regulated identically by AR and FOXA1 and also suppresses cellular migration and metastasis. Finally, based on TCGA analysis, DRAIC expression predicts good prognosis in a wide range of malignancies, including bladder cancer, low-grade gliomas, lung adenocarcinoma, stomach adenocarcinoma, renal clear cell carcinoma, hepatocellular carcinoma, skin melanoma, and stomach adenocarcinoma.

IMPLICATIONS

This study reveals a novel tumor-suppressive locus encoding two hormone-regulated lncRNAs, DRAIC and PCAT29, that are prognostic for a wide variety of cancer types.

A new lncRNA, APTR, associates with and represses the CDKN1A/p21 promoter by recruiting polycomb proteins

Long noncoding RNAs (lncRNAs) have emerged as a major regulator of cell physiology, but many of which have no known function. CDKN1A/p21 is an important inhibitor of the cell-cycle, regulator of the DNA damage response and effector of the tumor suppressor p53, playing a crucial role in tumor development and prevention. In order to identify a regulator for tumor progression, we performed an siRNA screen of human lncRNAs required for cell proliferation, and identified a novel lncRNA, APTR, that acts in trans to repress the CDKN1A/p21 promoter independent of p53 to promote cell proliferation. APTR associates with the promoter of CDKN1A/p21 and this association requires a complementary-Alu sequence encoded in APTR. A different module of APTR associates with and recruits the Polycomb repressive complex 2 (PRC2) to epigenetically repress the p21 promoter. A decrease in APTR is necessary for the induction of p21 after heat stress and DNA damage by doxorubicin, and the levels of APTR and p21 are anti-correlated in human glioblastomas. Our data identify a new regulator of the cell-cycle inhibitor CDKN1A/p21 that acts as a proliferative factor in cancer cell lines and in glioblastomas and demonstrate that Alu elements present in lncRNAs can contribute to targeting regulatory lncRNAs to promoters.