Using HapMap data: a cautionary note

The HapMap data are being widely used in human genetic studies. We show by direct resequencing of a 6-kb region of chromosome 1 that the HapMap data are unreliable for this region. This region contains a recent mitochondrial (mt) DNA insertion. The HapMap data report the corresponding mtDNA variation and not the nuclear DNA variation. In view of mtDNA insertions of varying lengths throughout the human genome and considerable segmental duplications, it is necessary to use the HapMap data cautiously

SARS-CoV-2 B.1.617.2 Delta variant replication and immune evasion

Abstract: The B.1.617.2 (Delta) variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first identified in the state of Maharashtra in late 2020 and spread throughout India, outcompeting pre-existing lineages including B.1.617.1 (Kappa) and B.1.1.7 (Alpha)1. In vitro, B.1.617.2 is sixfold less sensitive to serum neutralizing antibodies from recovered individuals, and eightfold less sensitive to vaccine-elicited antibodies, compared with wild-type Wuhan-1 bearing D614G. Serum neutralizing titres against B.1.617.2 were lower in ChAdOx1 vaccinees than in BNT162b2 vaccinees. B.1.617.2 spike pseudotyped viruses exhibited compromised sensitivity to monoclonal antibodies to the receptor-binding domain and the amino-terminal domain. B.1.617.2 demonstrated higher replication efficiency than B.1.1.7 in both airway organoid and human airway epithelial systems, associated with B.1.617.2 spike being in a predominantly cleaved state compared with B.1.1.7 spike. The B.1.617.2 spike protein was able to mediate highly efficient syncytium formation that was less sensitive to inhibition by neutralizing antibody, compared with that of wild-type spike. We also observed that B.1.617.2 had higher replication and spike-mediated entry than B.1.617.1, potentially explaining the B.1.617.2 dominance. In an analysis of more than 130 SARS-CoV-2-infected health care workers across three centres in India during a period of mixed lineage circulation, we observed reduced ChAdOx1 vaccine effectiveness against B.1.617.2 relative to non-B.1.617.2, with the caveat of possible residual confounding. Compromised vaccine efficacy against the highly fit and immune-evasive B.1.617.2 Delta variant warrants continued infection control measures in the post-vaccination era

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

Funder: NCI U24CA211006Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts

A large, systematic molecular-genetic study of G6PD in Indian populations identifies a new non-synonymous variant and supports recent positive selection

Malaria has been endemic in India. G6PD deficiency is known to confer resistance to malaria. Many G6PD deficiency variants, some of which are India-specific, are known to occur in high frequencies in India. This is the first systematic molecular-genetic study in multiple populations from India drawn from diverse ethnic, socio-cultural and geographical backgrounds. Resequencing of the G6PD gene was carried out in 80 males and then the polymorphic variants were genotyped in 400 individuals of both genders, drawn from 10 ethnic groups of India. Our study has identified one new exonic variant (M159I; exon-5), occurring in multiple populations, that is predicted to result in G6PD deficiency. A strong geographical sub-structuring of known G6PD variants has also been established. We have compared all available data from public-domain resources with those generated in this study to identify the nature and extent of natural selection. Our results (a) provide indication of weak negative selection, and (b) reveal signals of recent positive selection for the G6PD Orissa and G6PD Coimbra mutation bearing haplotypes. These inferences have been interpreted in the light of malarial protection to the populations that have been long exposed to plasmodium infection

Mutational landscape of cytokine genes across major tumour types identifies new targets

Introduction: Components of immune system communicate extensively in tumour micro environment. Normally, immune system engages with tumours to inhibit its further progression. Simultaneously, cancer cells learn cues derived from immune system to its own growth advantage. Cytokines are cell signaling messengers that affect disease pathogenesis, non-specific response to infection, specific response to antigen, etc. A battery of cytokines are produced in the tumour microenvironment, when released in response to infections and inflammations, can function to inhibit tumour development and progression. Cancer cells also release cytokines that promote growth, extenuate apoptosis and perform invasion and metastasis. Hypothesis: Alterations in cytokine signaling genes might help tumour to misguide immune system. The aim of the study is to identify such genomic alterations in cytokine genes that may drive major human cancers. Methods: We did extensive literature survey to prepare a list of known cytokine genes (n=776) which were validated in multiple databases. To know the baseline DNA variation in cytokine genes, we analyzed DNA variations in healthy human population from the 1000 Genome project dataset. Somatic mutational landscape for cytokine genes were analyzed in 32 different human cancer types (TCGA data). Significantly mutated genes were detected using MutSig2CV and Oncodrive FM analysis. Genes found significant in both analysis were  tabulated. Standard statistical  and bioinformatic analysis were done further to identify putative driver events. Result: We detected 9 significantly mutated cytokine genes across major tumor types. EDN1 was found to be most significantly mutated, in multiple tumour types; apart from genes like CDH1, B2M, HLA-B, IL4, TRIM22, TGFB1, GDF1 and CRABP2. Discussion: Our systematic survey of somatic mutations in cytokine genes, in major tumour types, identified novel genes targets such as EDN1 gene. EDN1 is a chemokine, also a potent vasoconstrictor. EDN1 signaling modifies tumour microenvironment by regulating contribution of cells around tumor stroma through both autocrine and paracrine mechanisms, by promoting tumour cell proliferation, neovascularization, etc. Other significantly mutated genes are associated with antigen presentation, cell proliferation and chemoattraction. Rational combination therapy with current inhibitors to disrupt these signaling networks in tumor microenvironment, may improve clinical outcomes in patients

Study of Caspase 8 mutation in oral cancer and adjacent precancer tissues and implication in progression.

It is hypothesized that same driver gene mutations should be present in both oral leukoplakia and cancer tissues. So, we attempted to find out mutations at one of the driver genes, CASP8, in cancer and adjacent leukoplakia tissues. Patients (n = 27), affected by both of cancer and adjacent leukoplakia, were recruited for the study. Blood and tissue DNA samples were used to identify somatic mutations at CASP8 by next generation sequencing method. In total, 56% (15 out of 27) cancer and 30% (8 out of 27) leukoplakia tissues had CASP8 somatic mutations. In 8 patients, both cancer and adjacent leukoplakia tissues, located within 2-5 cm of tumor sites, had identical somatic mutations. But, in 7 patients, cancer samples had somatic mutations but none of the leukoplakia tissues, located beyond 5cm of tumor sites, had somatic mutations. Mutated allele frequencies at CASP8 were found to be more in cancer compared to adjacent leukoplakia tissues. This study provides mutational evidence that oral cancer might have progressed from previously grown leukoplakia lesion. Leukoplakia tissues, located beyond 5cm of cancer sites, were free from mutation. The study implies that CASP8 mutation could be one of the signatures for some of the leukoplakia to progress to oral cancer

NOTCH pathway inactivation reprograms stem-like oral cancer cells to JAK-STAT dependent state and provides the opportunity of synthetic lethality

Background: We have recently provided the evidence of interconvertible cellular states, driving non-genetic heterogeneity among stem-like oral cancer cells (oral-SLCCs). Here, NOTCH pathway-activity status is explored as one of the possible mechanisms behind this stochastic plasticity. Methods: Oral-SLCCs were enriched in 3D-spheroids. Constitutively-active and inactive status of NOTCH pathway was achieved by genetic or pharmacological approaches. RNA sequencing and real-time PCR was performed for gene expression studies. in vitro cytotoxicity assessments were performed by AlamarBlue assay and in vivo effects were studied by xenograft growth in zebrafish embryo. Results: We have observed stochastic plasticity in oral-SLCCs, spontaneously maintaining both NOTCH-active and inactive states. While cisplatin refraction was associated with post-treatment adaptation to the active-state of NOTCH pathway, oral-SLCCs with inactive NOTCH pathway status showed aggressive tumor growth and poor prognosis. RNAseq analysis clearly suggested the upregulation of JAK-STAT pathway in NOTCH pathway-inactive subset. The 3D-spheroids with lower NOTCH-activity status displayed significantly higher sensitivity to JAK-selective drugs, Ruxolitinib or Tofacitinib or siRNA mediated downregulation of tested partners STAT3/4. Oral-SLCCs were programmed to adapt the inactive status of NOTCH pathway by exposing to γ-secretase inhibitors, LY411575 or RO4929097, followed by targeting with JAK-inhibitors, Ruxolitinib or Tofacitinib. This approach resulted in a very significant inhibition in viability of 3D-spheroids as well as xenograft initiation in Zebrafish embryos. Conclusion: Study revealed for the first time that NOTCH pathway-inactive state exhibit activation of JAK-STAT pathways, as synthetic lethal pair. Therefore, co-inhibition of these pathway may serve as novel therapeutic strategy against aggressive oral cancer

Analysis of the whole transcriptome from gingivo-buccal squamous cell carcinoma reveals deregulated immune landscape and suggests targets for immunotherapy

<div><p>Background</p><p>Gingivo-buccal squamous cell carcinoma (GBSCC) is one of the most common oral cavity cancers in India with less than 50% patients surviving past 5 years. Here, we report a whole transcriptome profile on a batch of GBSCC tumours with diverse tobacco usage habits. The study provides an entire landscape of altered expression with an emphasis on searching for targets with therapeutic potential.</p><p>Methods</p><p>Whole transcriptomes of 12 GBSCC tumours and adjacent normal tissues were sequenced and analysed to explore differential expression of genes. Expression changes were further compared with those in TCGA head and neck cohort (n = 263) data base and validated in an independent set of 10GBSCC samples.</p><p>Results</p><p>Differentially expressed genes (n = 2176) were used to cluster the patients based on their tobacco habits, resulting in 3 subgroups. Immune response was observed to be significantly aberrant, along with cell adhesion and lipid metabolism processes. Different modes of immune evasion were seen across 12 tumours with up-regulation or consistent expression of <i>CD47</i>, unlike other immune evasion genes such as <i>PDL1</i>, <i>FUT4</i>, <i>CTLA4</i> and <i>BTLA</i> which were downregulated in a few samples. Variation in infiltrating immune cell signatures across tumours also indicates heterogeneity in immune evasion strategies. A few actionable genes such as <i>ITGA4</i>, <i>TGFB1</i> and <i>PTGS1/COX1</i> were over expressed in most samples.</p><p>Conclusion</p><p>This study found expression deregulation of key immune evasion genes, such as <i>CD47</i> and <i>PDL1</i>, and reasserts their potential as effective immunotherapeutic targets for GBSCC, which requires further clinical studies. Present findings reiterate the idea of using transcriptome profiling to guide precision therapeutic strategies.</p></div

Schematic view of fusion events.

<p>(A) ANO1-PLA2G16 fusion gene which retains exon 16 along with upstream exons of ANO1 and exon 3 along with downstream exons of PLA2G16 in tumour tissue (i.e. 23D) of the tumour-normal paired S23 sample. (B) S100A9-KRT17 fusion gene deduced from coding regions up to exon 3 of S100A9 and exon 1 to all other downstream exons of KRT17 in tumour tissue (i.e. 2D) of the tumour-normal paired S2 sample.</p