Spatial and Temporal Heterogeneity in High-Grade Serous Ovarian Cancer: A Phylogenetic Analysis

Background

The major clinical challenge in the treatment of high-grade serous ovarian cancer (HGSOC) is the development of progressive resistance to platinum-based chemotherapy. The objective of this study was to determine whether intra-tumour genetic heterogeneity resulting from clonal evolution and the emergence of subclonal tumour populations in HGSOC was associated with the development of resistant disease.

Methods and Findings

Evolutionary inference and phylogenetic quantification of heterogeneity was performed using the MEDICC algorithm on high-resolution whole genome copy number profiles and selected genome-wide sequencing of 135 spatially and temporally separated samples from 14 patients with HGSOC who received platinum-based chemotherapy. Samples were obtained from the clinical CTCR-OV03/04 studies, and patients were enrolled between 20 July 2007 and 22 October 2009. Median follow-up of the cohort was 31 mo (interquartile range 22–46 mo), censored after 26 October 2013. Outcome measures were overall survival (OS) and progression-free survival (PFS). There were marked differences in the degree of clonal expansion (CE) between patients (median 0.74, interquartile range 0.66–1.15), and dichotimization by median CE showed worse survival in CE-high cases (PFS 12.7 versus 10.1 mo, p = 0.009; OS 42.6 versus 23.5 mo, p = 0.003). Bootstrap analysis with resampling showed that the 95% confidence intervals for the hazard ratios for PFS and OS in the CE-high group were greater than 1.0. These data support a relationship between heterogeneity and survival but do not precisely determine its effect size. Relapsed tissue was available for two patients in the CE-high group, and phylogenetic analysis showed that the prevalent clonal population at clinical recurrence arose from early divergence events. A subclonal population marked by a NF1 deletion showed a progressive increase in tumour allele fraction during chemotherapy.

Conclusions

This study demonstrates that quantitative measures of intra-tumour heterogeneity may have predictive value for survival after chemotherapy treatment in HGSOC. Subclonal tumour populations are present in pre-treatment biopsies in HGSOC and can undergo expansion during chemotherapy, causing clinical relapse.     

A variety of changes,including CRISPR/Cas9‐mediated deletions,in CENH3 lead to haploid induction on outcrossing

Creating true‐breeding lines is a critical step in plant breeding. Novel, completely homozygous true‐breeding lines can be generated by doubled haploid technology in single generation. Haploid induction through modification of the centromere‐specific histone 3 variant (CENH3), including chimeric proteins, expression of non‐native CENH3 and single amino acid substitutions, has been shown to induce, on outcrossing to wild type, haploid progeny possessing only the genome of the wild‐type parent, in Arabidopsis thaliana. Here, we report the characterization of 31 additional EMS‐inducible amino acid substitutions in CENH3 for their ability to complement a knockout in the endogenous CENH3 gene and induce haploid progeny when pollinated by the wild type. We also tested the effect of double amino acid changes, which might be generated through a second round of EMS mutagenesis. Finally, we report on the effects of CRISPR/Cas9‐mediated in‐frame deletions in the αN helix of the CENH3 histone fold domain. Remarkably, we found that complete deletion of the αN helix, which is conserved throughout angiosperms, results in plants which exhibit normal growth and fertility while acting as excellent haploid inducers when pollinated by wild‐type pollen. Both of these technologies, CRISPR mutagenesis and EMS mutagenesis, represent non‐transgenic approaches to the generation of haploid inducers.     

A fluctuation method to quantify in vivo fluorescence data

Quantitative in vivo measurements are essential for developing a predictive understanding of cellular behavior. Here we present a technique that converts observed fluorescence intensities into numbers of molecules. By transiently expressing a fluorescently tagged protein and then following its dilution during growth and division, we observe asymmetric partitioning of fluorescence between daughter cells at each division. Such partition asymmetries are set by the actual numbers of proteins present, and thus provide a means to quantify fluorescence levels. We present a Bayesian algorithm that infers from such data both the fluorescence conversion factor and an estimate of the measurement error. Our algorithm works for arbitrarily sized data sets and handles consistently any missing measurements. We verify the algorithm with extensive simulation and demonstrate its application to experimental data from Escherichia coli. Our technique should provide a quantitative internal calibration to systems biology studies of both synthetic and endogenous cellular networks.     

Warfarin pharmacogenetics: polymorphisms of the CYP2C9, CYP4F2, and VKORC1 loci in a genetically admixed Omani population

This is the first study to evaluate the spectrum and prevalence of dose-predictive genetic polymorphisms of the CYP2C9, CYP4F2 and VKORC1 loci together, in a geographically defined, ethnically admixed healthy adult Omani population sharing common lifestyle/environmental factors. Since the present-day Omani population is the result of an admixture of Caucasian, African and Asian ancestries, we compared the pharmacogenetic profile of these three loci in this population. Interestingly, the Omani pharmacogenetic profile, in terms of allele and genotype distribution, has values that are intermediate between Caucasians and African Americans, the African admixture further substantiated by the presence of the CYP2C9*8 allele. However, limitations and usefulness of such comparisons warrant caution, as the data from pharmacogenetic literature do not always represent bona fide population categories. Furthermore, definition of study population based on microgeographical scale would be more appropriate in pharmacogenetic research rather than the flawed racial, ethnic, or social categorizations since pharmacogenetic variation is clinal, and genetic influences will be further altered by lifestyle and environmental factors.     

Identification of pathogenic bacteria in blood cultures: Comparison between conventional and PCR methods

Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Acinetobacter baumanii, and Klebsiella pneumoniae were found to be the most prevalent bacteremia-causing bacteria in a survey in a medical center. A PCR method for identification of these five most common pathogens in blood cultures was developed. A unique sequence was chosen for each pathogen and used for primer design. Sixty-one blood samples (from hospitalized patients) in which bacterial growth was detected were processed in parallel by conventional microbiological methods and by the PCR method. The results obtained by PCR were identical to those obtained by conventional methods in 93.4% of the cases. PCR failed to identify bacteria which were found conventionally in only 6.6% of the cases (mostly bacteria not included in the PCR cassette). Another group of eighty-eight blood samples from patients were processed immediately upon their arrival at the laboratory by taking aliquots for the PCR method. The blood sample bottles were processed in parallel by conventional methods. In 78.4% of the cases the results of both methods were identical. In 12.5% of the cases, PCR afforded identification of bacteria but conventional methods showed no bacteria in the sample. On the other hand, PCR afforded 9.1% negative results while conventional methods identified bacteria not included in the PCR cassette. It is concluded that the molecular method appears to be a specific and precise method for identifying pathogenic bacteria in blood samples.     

Molecular features of heterogeneous vancomycin-intermediate Staphylococcus aureus strains isolated from bacteremic patients

Background  

Heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) bacteremia is an emerging infection. Our objective was to determine the molecular features of hVISA strains isolated from bacteremic patients and to compare them to methicillin resistant S. aureus (MRSA) and methicillin sensitive S. aureus (MSSA) blood isolates.     

Differential diagnosis of hepatocellular carcinoma from metastatic tumors in the liver using microRNA expression

Distinguishing hepatocellular carcinoma from metastatic tumors in the liver is of great practical importance, with significant therapeutic and prognostic implications. This differential diagnosis can be difficult because metastatic cancers in the liver, especially adenocarcinomas, may mimic the morphology and immunoexpression of hepatocellular carcinoma. Biomarkers that are specifically expressed in either hepatocellular carcinoma or metastatic adenocarcinoma can therefore be useful diagnostic tools. To find such biomarkers, we studied microRNA expression in 144 tumor samples using custom microarrays. Hsa-miR-141 and hsa-miR-200c, microRNAs that promote epithelial phenotypes, had significantly higher levels in non-hepatic epithelial tumors. In contrast, endothelial-associated hsa-miR-126 showed higher expression levels in hepatocellular carcinomas. Combinations of these microRNAs accurately identified primary hepatocellular carcinoma from metastatic adenocarcinoma in the liver. These findings were validated using quantitative real-time PCR to measure microRNA expression in additional samples. Thus, the tissue-specific expression patterns of microRNAs make them useful biomarkers for the diagnosis of liver malignancies.     

Large-scale field application of RNAi technology reducing Israeli acute paralysis virus disease in honey bees (Apis mellifera, Hymenoptera: Apidae)

The importance of honey bees to the world economy far surpasses their contribution in terms of honey production; they are responsible for up to 30% of the world's food production through pollination of crops. Since fall 2006, honey bees in the U.S. have faced a serious population decline, due in part to a phenomenon called Colony Collapse Disorder (CCD), which is a disease syndrome that is likely caused by several factors. Data from an initial study in which investigators compared pathogens in honey bees affected by CCD suggested a putative role for Israeli Acute Paralysis Virus, IAPV. This is a single stranded RNA virus with no DNA stage placed taxonomically within the family Dicistroviridae. Although subsequent studies have failed to find IAPV in all CCD diagnosed colonies, IAPV has been shown to cause honey bee mortality. RNA interference technology (RNAi) has been used successfully to silence endogenous insect (including honey bee) genes both by injection and feeding. Moreover, RNAi was shown to prevent bees from succumbing to infection from IAPV under laboratory conditions. In the current study IAPV specific homologous dsRNA was used in the field, under natural beekeeping conditions in order to prevent mortality and improve the overall health of bees infected with IAPV. This controlled study included a total of 160 honey bee hives in two discrete climates, seasons and geographical locations (Florida and Pennsylvania). To our knowledge, this is the first successful large-scale real world use of RNAi for disease control.     

Diffusion of β-Lactam Antibiotics Through Oligomeric or Monomeric Porin Channels of Some Gram-Negative Bacteria

The penetration of anionic β-lactam antibiotics through porins was evaluated as a mechanism of drug resistance. The major proteins with porin activity were purified from the outer membranes of six bacteria. Three of the six porins were oligomeric porins. The molecular weights of their monomers were 37 kDa from Photobacterium damsela, 42 kDa from Serratia liquefaciens, and 36 kDa from E. coli B. The other three porins were heat-modifiable monomeric porins with molecular weights of 43 kDa from Porphyromonas asaccharolytica and Acinetobacter baumannii, and 37 kDa from Escherichia coli K12. Comparison of the six porin proteins revealed that, independent of their aggregation state, their amino acid content is similar but not identical. All have double the amount of negatively charged amino acids compared with positively charged amino acids. They have a similar polarity and polarity index. Two of the six tested bacteria do not produce β-lactamase. These two bacteria were sensitive to the different β-lactams tested. The other four bacteria were resistant to all or to several β-lactams. A modified liposome swelling method was used for determining the rate of penetration of charged β-lactam antibiotics. Zwitterionic β-lactams were found to penetrate into liposomes at a rate that more or less fits their molecular weight, whether the porins are monomeric or oligomeric. The penetration rates of negatively charged β-lactams are different for oligomeric and monomeric porins. Negatively charged β-lactams penetrate through oligomeric porins better than estimated by their molecular weight, whereas monomeric porins are less penetrable to negatively charged β-lactams than estimated by their molecular weight. The contribution of all types of porins to the susceptibility of bacteria to β-lactam antibiotics (zwitterionic or negatively charged) is apparently doubtful. The porins may decrease or increase bacterial penetration rates to β-lactams, and only the existence of a potential β-lactamase that can destroy the penetrating drug will cause resistance. Received: 28 January 2002 / Accepted: 4 May 2002