Drug-tolerant persister cancer cells are vulnerable to GPX4 inhibition.

Acquired drug resistance prevents cancer therapies from achieving stable and complete responses. Emerging evidence implicates a key role for non-mutational drug resistance mechanisms underlying the survival of residual cancer 'persister' cells. The persister cell pool constitutes a reservoir from which drug-resistant tumours may emerge. Targeting persister cells therefore presents a therapeutic opportunity to impede tumour relapse. We previously found that cancer cells in a high mesenchymal therapy-resistant cell state are dependent on the lipid hydroperoxidase GPX4 for survival. Here we show that a similar therapy-resistant cell state underlies the behaviour of persister cells derived from a wide range of cancers and drug treatments. Consequently, we demonstrate that persister cells acquire a dependency on GPX4. Loss of GPX4 function results in selective persister cell ferroptotic death in vitro and prevents tumour relapse in mice. These findings suggest that targeting of GPX4 may represent a therapeutic strategy to prevent acquired drug resistance

A Chemical Glycoproteomics Platform Reveals O-GlcNAcylation of Mitochondrial Voltage-Dependent Anion Channel 2

SummaryProtein modification by O-linked β-N-acetylglucosamine (O-GlcNAc) is a critical cell signaling modality, but identifying signal-specific O-GlcNAcylation events remains a significant experimental challenge. Here, we describe a method for visualizing and analyzing organelle- and stimulus-specific O-GlcNAcylated proteins and use it to identify the mitochondrial voltage-dependent anion channel 2 (VDAC2) as an O-GlcNAc substrate. VDAC2−/− cells resist the mitochondrial dysfunction and apoptosis caused by global O-GlcNAc perturbation, demonstrating a functional connection between O-GlcNAc signaling and mitochondrial physiology through VDAC2. More broadly, our method will enable the discovery of signal-specific O-GlcNAcylation events in a wide array of experimental contexts

Live-Cell Imaging of Cellular Proteins by a Strain-Promoted Azide–Alkyne Cycloaddition

Live and let dye: Three coumarin-cyclooctyne conjugates have been used to label proteins tagged with azidohomoalanine in Rat-1 fibroblasts. All three fluorophores labeled intracellular proteins with fluorescence enhancements ranging from eight- to 20-fold. These conjugates are powerful tools for visualizing biomolecule dynamics in living cells

Drug Resistance to EGFR Inhibitors in Lung Cancer

BackgroundThe discovery of mutations in epidermal growth factor receptor (EGFR) has dramatically changed the treatment of patients with non-small-cell lung cancer (NSCLC), the leading cause of cancer deaths worldwide. EGFR-targeted therapies show considerable promise, but drug resistance has become a substantial issue.MethodsWe reviewed the literature to provide an overview of the drug resistance to EGFR tyrosine kinase inhibitors (TKIs) in NSCLC.ResultsThe mechanisms causing primary, acquired and persistent drug resistance to TKIs vary. Researchers and clinicians, who have used study findings to develop more effective therapeutic approaches, have found that the sequential use of single agents presents a formidable challenge, suggesting that multidrug combinations must be considered.ConclusionsIn the era of precision medicine, oncologists should promptly obtain an accurate diagnosis of drug resistance in each patient to be able to design the most relevant combination therapy to overcome patient-specific drug resistance

Pervasive Transcription of the Human Genome Produces Thousands of Previously Unidentified Long Intergenic Noncoding RNAs

<div><p>Known protein coding gene exons compose less than 3% of the human genome. The remaining 97% is largely uncharted territory, with only a small fraction characterized. The recent observation of transcription in this intergenic territory has stimulated debate about the extent of intergenic transcription and whether these intergenic RNAs are functional. Here we directly observed with a large set of RNA-seq data covering a wide array of human tissue types that the majority of the genome is indeed transcribed, corroborating recent observations by the ENCODE project. Furthermore, using <i>de novo</i> transcriptome assembly of this RNA-seq data, we found that intergenic regions encode far more long intergenic noncoding RNAs (lincRNAs) than previously described, helping to resolve the discrepancy between the vast amount of observed intergenic transcription and the limited number of previously known lincRNAs. In total, we identified tens of thousands of putative lincRNAs expressed at a minimum of one copy per cell, significantly expanding upon prior lincRNA annotation sets. These lincRNAs are specifically regulated and conserved rather than being the product of transcriptional noise. In addition, lincRNAs are strongly enriched for trait-associated SNPs suggesting a new mechanism by which intergenic trait-associated regions may function. These findings will enable the discovery and interrogation of novel intergenic functional elements.</p></div

Drug Resistance to EGFR Inhibitors in Lung Cancer

BACKGROUND: The discovery of mutations in epidermal growth factor receptor (EGFR) has dramatically changed the treatment of patients with non-small cell lung cancer (NSCLC)—the leading cause of cancer death worldwide. EGFR-targeted therapies show considerable promise, but drug resistance has become a substantial issue. METHODS: We reviewed the literature to provide an overview of the drug resistance to EGFR tyrosine kinase inhibitors (TKIs) in NSCLC. RESULTS: The mechanisms causing primary, acquired, and persistent drug resistance to TKIs vary. Researchers and clinicians, who have used study findings to develop more effective therapeutic approaches, have found that the sequential use of single agents presents a formidable challenge, suggesting that multi-drug combinations must be considered. CONCLUSIONS: In the era of precision medicine, oncologists should promptly obtain an accurate diagnosis of drug resistance in each patient to design the most relevant combination therapy to overcome patient-specific drug resistance

The human intergenic transcriptome.

<p>(A) 85.2% of the genome has evidence of transcription, with RNA-seq reads mapping directly to 78.9% of genomic sequence. The remaining genomic coverage is comprised of known genes, spliced ESTs and spliced cDNAs. The grey circle represents the portion of the genome (83.4%) that is uniquely mappable with RNA-seq reads. (B) Protein coding (NM gene) exon, intron and intergenic region expression level distribution. Regions that have high expression have a larger fraction of base calls appearing at higher read depths. Protein coding gene exons have the highest proportion of bases with high read depth, while introns and intergenic regions have relatively more bases of low read depth though each contain many highly expressed regions. Base calls = (# of genomic positions at a specific read depth)(read depth). (C) Most intergenic transcription is outside of annotated noncoding RNA genes. The fraction of intergenic base calls within RefSeq noncoding RNA genes (NR genes) compared to other intergenic regions are compared. In (A–C), only uniquely mappable portions of the genome are considered (see Methods).</p

LincRNAs are enriched for trait-associated SNPs.

<p>The number of trait-associated SNPs within RefSeq NM gene exons, lincRNA exons, or background loci (nonexpressed intergenic sequence) per tested SNP in genome wide association studies is compared (see Methods). *<i>P</i> = 0.0173, **<i>P</i><2.2E-16; error bars represent 95% binomial proportion confidence interval.</p