Next-generation Sequencing Of Genomic DNA Research Articles

Abstract 5250: Association between UGT1A1 gene polymorphism and safety and efficacy of irinotecan monotherapy as the second-line treatment for advanced gastric cancer

Abstract Objective: Uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1) is a key enzyme in irinotecan metabolism. However, the relationship between UGT1A1 genotype and the safety and efficacy of irinotecan monotherapy in the treatment of Chinese advanced gastric cancer remains unclear. Methods: A total of 110 patients were enrolled. Intravenous irinotecan was administered every 3 weeks. Irinotecan dose was selected according to the polymorphism of UGT1A1 gene, which was divided into 3 groups: UGT1A1*6 wild-type (GG type): 125mg/m2, d1, d8; UGT1A1*6 mutant heterozygosity (GA type) 100mg/m2, d1, d8; UGT1A1*6 homozygosity mutation (AA type) 75mg/m2, d1, d8 or paclitaxel 125mg/m2, d1, d8. UGT1A1 genotypes were determined by direct sequencing or next-generation sequencing of genomic DNA extracted from peripheral blood. Results: Among 110 patients of the subjects, the genotypes of UGT1A1*28 were wild-type in 78 patients (70.91%), mutant heterozygosity in 28 (25.45%) and mutant homozygosity in 4 (3.64%). UGT1A1*6 were GG in 67 cases (60.91%), GA in 35 cases (31.82%), and AA in 8 cases (7.27%). There were two heterozygous mutations in 3 patients, and no homozygous mutation was detected. A total of 10 cycles of irinotecan were administered, with a median of five cycles per patient. There was no significant difference in the risk of delayed diarrhea and granulocytopenia in patients with different UGT1A1*28 genotypes (P>0.05), while there was significant difference in the risk of delayed diarrhea and granulocytopenia in patients with different UGT1A1*6 genotypes (P<0.05). The dose intensity of irinotecan was different in patients with different subtypes of UGT1A1*6 gene, and the dose intensity of heterozygous mutant patients was lower than that of wild-type patients. However, there were no significant differences in PFS and OS among patients with different subtypes after dose adjustment and program adjustment (P>0.05). Conclusion: UGT1A1*6 gene polymorphism was significantly associated with diarrhea and neutropenia induced by irinotecan. The safety and effectiveness of antitumor therapy might be significantly improved by individualized drug administration according to the results of UGT1A1*6 gene polymorphism. Citation Format: Huifang Lv, Yunduan He, Caiyun Nie, Beibei Chen, Jianzheng Wang, Weifeng Xu, Jing Zhao, Xiaobing Chen, Junling Zhang. Association between UGT1A1 gene polymorphism and safety and efficacy of irinotecan monotherapy as the second-line treatment for advanced gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5250.

Identification of Novel UGT1A1 Variants Including UGT1A1 454C>A through the Genotyping of Healthy Participants of the HPTN 077 Study.

Cabotegravir (CAB) is an integrase strand-transfer inhibitor of HIV that has proven effective for HIV treatment and prevention in a long-acting injectable formulation, typically preceded by an oral formulation lead-in phase. Previous in vitro studies have demonstrated that CAB is primarily metabolized via glucuronidation by uridine diphosphate glucuronosyltransferase (UGT) 1A1 and 1A9. In this study, we performed next-generation sequencing of genomic DNA isolated from the HPTN 077 participants to explore the variants within UGT1A1 and UGT1A9. Additionally, to enable correlation of UGT1A1 and UGT1A9 genotypes with plasma CAB-glucuronide levels, we quantified glucuronidated CAB following both oral administration of CAB and intramuscular injection of long-acting CAB. From these studies, 48 previously unreported variants of UGT1A1 and UGT1A9 were detected. Notably, 5/68 individuals carried a UGT1A1 454C>A variant that resulted in amino acid substitution P152T, and the use of in silico tools predicted a deleterious effect of the P152T substitution. Thus, the impact of this mutant on a range of UGT1A1 substrates was tested using a COS-7 cell-based assay. The glucuronide conjugates of CAB, dolutegravir, and raltegravir, were not formed in the COS-7 cells expressing the UGT1A1 P152T mutant. Further, formation of glucuronides of raloxifene and 7-ethyl-10-hydroxycamptothecin were reduced in the cells expressing the UGT1A1 P152T mutant. Using the same approach, we tested the activities of two UGT1A9 mutants, UGT1A9 H217Y and UGT1A9 R464G, and found that these mutations were tolerated and decreased function, respectively. These data provide insight into previously unreported genetic variants of UGT1A1 and UGT1A9.

Identification of KMT2D and KDM6A variants by targeted sequencing from patients with Kabuki syndrome and other congenital disorders

Kabuki syndrome (KS) is a rare congenital disorder characterized by distinctive facies, postnatal growth deficiency, cardiac defects and skeletal anomalies. Studies have determined that pathogenic variants of the lysine-specific methyltransferase 2D (KMT2D) and lysine-specific demethylase 6A (KDM6A) genes are the major causes of KS. The two genes encode different histone-modifying enzymes that are found in the same protein complex that is critical for cell differentiation during development. Here we report the results from next-generation sequencing of genomic DNA from 13 patients who had a clinical diagnosis of KS based on facial dysmorphism and other KS-specific cardinal phenotypes. Nine of the 13 patients were confirmed to be carrying heterozygous pathogenic KMT2D variants, seven of which were truncating and two were missense substitutions. Overall, we uncovered 11 novel variants – nine in KMT2D and two in KDM6A. Seven of the novel variants (all KMT2D) were likely causative of the KS phenotype. Our study expands the number of naturally occurring KMT2D and KDM6A variants. The discovery of novel pathogenic variants will add to the knowledge on disease-causing variants and the relevance of missense variants in KS.

IRF5 regulates unique subset of genes in dendritic cells during West Nile virus infection.

Pathogen recognition receptor (PRR) signaling is critical for triggering innate immune activation and the expression of immune response genes, including genes that impart restriction against virus replication. RIG-I-like receptors and TLRs are PRRs that signal immune activation and drive the expression of antiviral genes and the production of type I IFN leading to induction of IFN-stimulated genes, in part through the interferon regulatory factor (IRF) family of transcription factors. Previous studies with West Nile virus (WNV) showed that IRF3 and IRF7 regulate IFN expression in fibroblasts and neurons, whereas macrophages and dendritic cells (DCs) retained the ability to induce IFN-β in the absence of IRF3 and IRF7 in a manner implicating IRF5 in PRR signaling actions. Here we assessed the contribution of IRF5 to immune gene induction in response to WNV infection in DCs. We examined IRF5-dependent gene expression and found that loss of IRF5 in mice resulted in modest and subtle changes in the expression of WNV-regulated genes. Anti-IRF5 chromatin immunoprecipitation with next-generation sequencing of genomic DNA coupled with mRNA analysis revealed unique IRF5 binding motifs within the mouse genome that are distinct from the canonical IRF binding motif and that link with IRF5-target gene expression. Using integrative bioinformatics analyses, we identified new IRF5 primary target genes in DCs in response to virus infection. This study provides novel insights into the distinct and unique innate immune and immune gene regulatory program directed by IRF5.

Genetic Variation of the Kinases That Phosphorylate Tenofovir and Emtricitabine in Peripheral Blood Mononuclear Cells.

Tenofovir (TFV) disoproxil fumarate and emtricitabine (FTC) are used in combination for HIV treatment and pre-exposure prophylaxis (PrEP). TFV disoproxil fumarate is a prodrug that undergoes diester hydrolysis to TFV. FTC and TFV are nucleoside/nucleotide reverse transcriptase inhibitors that upon phosphorylation to nucleotide triphosphate analogs competitively inhibit HIV reverse transcriptase. We previously demonstrated that adenylate kinase 2, pyruvate kinase, muscle and pyruvate kinase, liver and red blood cell phosphorylate TFV in peripheral blood mononuclear cells (PBMC). To identify the kinases that phosphorylate FTC in PBMC, siRNAs targeted toward kinases that phosphorylate compounds structurally similar to FTC were delivered to PBMC, followed by incubation with FTC and the application of a matrix-assisted laser desorption ionization-mass spectrometry method and ultra high performance liquid chromatography-UV to detect the formation of FTC phosphates. Knockdown of deoxycytidine kinase decreased the formation of FTC-monophosphate, while siRNA targeted toward thymidine kinase 1 decreased the abundance of FTC-diphosphate. Knockdown of either cytidine monophosphate kinase 1 or phosphoglycerate kinase 1 decreased the abundance of FTC-triphosphate. Next-generation sequencing of genomic DNA isolated from 498 HIV-uninfected participants in the HIV Prevention Trials Network 069/AIDS Clinical Trials Group A5305 clinical study, revealed 17 previously unreported genetic variants of TFV or FTC phosphorylating kinases. Of note, four individuals were identified as simultaneous carriers of variants of both TFV and FTC activating kinases. These results identify the specific kinases that activate FTC in PBMC, while also providing further insight into the potential for genetic variation to impact TFV and FTC activation.

OR22 High-resolution HLA typing and identification of a novel allele with a splice variant using RNA-SEQ

Aim RNA sequencing (RNA-Seq) is a powerful next-generation sequencing method for discovering, profiling and quantifying RNA transcripts. RNA-Seq can also identify splice junctions and single nucleotide polymorphisms (SNP) in coding exons. In this study, we tested if RNA-Seq reads provide sufficient coverage and depth for high-resolution HLA genotyping. Methods RNA-Seq data was available from 24 individuals from an acutely infected HIV cohort. We used two methods to extract HLA reads from the RNA-Seq data: 1) FR-HIT recruited RNA-Seq reads to the IMGT coding sequence reference database; and 2) the SNP-tolerant aligner GSNAP aligned the reads to a constructed GMAP database consisting of cDNA from HLA genes. The resulting HLA-specific FASTQ reads that were generated were analyzed by commercial HLA typing software. Results We obtained 100% sequence coverage and a median sequence read depth of 331, which was sufficient to genotype 15 HLA loci from each of the donors. HLA genotypes for 8 classical HLA class I and II loci matched genotypes generated from the Sanger sequence-based typing method, as well as targeted next-generation sequencing of genomic DNA. We identified a novel HLA-DQB1 allele in the Thai population with a frequency greater than 5% that was identical to the 05:01:01 allele in all exons except exon 1, where it differed by one SNP at position 81. The DQB1 * 05:01:01 allele, like several other DQB1 alleles, has exon 5 spliced out. This deletion however, cannot be confirmed from the reads that are obtained by sequencing genomic DNA. RNA-Seq confirmed that the novel allele does not express exon 5, as the RNA-Seq data showed a complete absence of exon 5 reads compared to reads from targeted genomic sequences. Conclusions We have successfully genotyped 15 HLA loci and confirmed a splice variant in a novel allele using RNA-Seq. This method highlights the importance of mining RNA-Seq data for high-resolution HLA genotyping. Additional analysis methods may be able to identify allele-specific expression of HLA alleles from RNA-Seq data.

Differentiating sibling species of Zeugodacus caudatus (Insecta: Tephritidae) by complete mitochondrial genome.

Zeugodacus caudatus is a pest of pumpkin flowers. It has a Palearctic and Oriental distribution. We report here the complete mitochondrial genome of the Malaysian and Indonesian samples of Z. caudatus determined by next-generation sequencing of genomic DNA and determine their taxonomic status as sibling species and phylogeny with other taxa of the genus Zeugodacus. The whole mitogenome of both samples possessed 37 genes (13 protein-coding genes-PCGs, 2 rRNA and 22 tRNA genes) and a control region. The mitogenome of the Indonesian sample (15,885bp) was longer than that of the Malaysian sample (15,866bp). In both samples, TΨC-loop was absent in trnF and DHU-loop was absent in trnS1. Molecular phylogeny based on 13 PCGs was concordant with 15 mitochondrial genes (13 PCGs and 2 rRNA genes), with the two samples of Z. caudatus forming a sister group and the genus Zeugodacus was monophyletic. The Malaysian and Indonesian samples of Z. caudatus have a genetic distance of p=7.8% based on 13 PCGs and p=7.0% based on 15 mitochondrial genes, indicating status of sibling species. They are proposed to be accorded specific status as members of a species complex.

Complete mitochondrial genome of Bactrocera arecae (Insecta: Tephritidae) by next-generation sequencing and molecular phylogeny of Dacini tribe.

The whole mitochondrial genome of the pest fruit fly Bactrocera arecae was obtained from next-generation sequencing of genomic DNA. It had a total length of 15,900 bp, consisting of 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes and a non-coding region (A + T-rich control region). The control region (952 bp) was flanked by rrnS and trnI genes. The start codons included 6 ATG, 3 ATT and 1 each of ATA, ATC, GTG and TCG. Eight TAA, two TAG, one incomplete TA and two incomplete T stop codons were represented in the protein-coding genes. The cloverleaf structure for trnS1 lacked the D-loop, and that of trnN and trnF lacked the TΨC-loop. Molecular phylogeny based on 13 protein-coding genes was concordant with 37 mitochondrial genes, with B. arecae having closest genetic affinity to B. tryoni. The subgenus Bactrocera of Dacini tribe and the Dacinae subfamily (Dacini and Ceratitidini tribes) were monophyletic. The whole mitogenome of B. arecae will serve as a useful dataset for studying the genetics, systematics and phylogenetic relationships of the many species of Bactrocera genus in particular, and tephritid fruit flies in general.

Mitochondrial Genome Supports Sibling Species of Angiostrongylus costaricensis (Nematoda: Angiostrongylidae).

Angiostrongylus costaricensis is a zoonotic parasitic nematode that causes abdominal or intestinal angiostrongyliasis in humans. It is endemic to the Americas. Although the mitochondrial genome of the Brazil taxon has been published, there is no available mitochondrial genome data on the Costa Rica taxon. We report here the complete mitochondrial genome of the Costa Rica taxon and its genetic differentiation from the Brazil taxon. The whole mitochondrial genome was obtained from next-generation sequencing of genomic DNA. It had a total length of 13,652 bp, comprising 36 genes (12 protein-coding genes—PCGs, 2 rRNA and 22 tRNA genes) and a control region (A + T rich non-coding region). It is longer than that of the Brazil taxon (13,585 bp). The larger mitogenome size of the Costa Rica taxon is due to the size of the control region as the Brazil taxon has a shorter length (265 bp) than the Costa Rica taxon (318 bp). The size of 6 PCGs and the start codon for ATP6, CYTB and NAD5 genes are different between the Costa Rica and Brazil taxa. Additionally, the two taxa differ in the stop codon of 6 PCGs. Molecular phylogeny based on 12 PCGs was concordant with two rRNA, 22 tRNA and 36 mitochondrial genes. The two taxa have a genetic distance of p = 16.2% based on 12 PCGs, p = 15.3% based on 36 mitochondrial genes, p = 13.1% based on 2 rRNA genes and p = 10.7% based on 22 tRNA genes, indicating status of sibling species. The Costa Rica and Brazil taxa of A. costaricensis are proposed to be accorded specific status as members of a species complex.

Diverse Genetic Lesions In Myelodysplastic Syndromes Originate Exclusively In Rare MDS Stem Cells

BackgroundThe popular concept that human cancers might be driven by rare self-renewing cancer stem cells (CSCs) has extensive implications for cancer biology and modelling, as well for development of more efficient and targeted therapies. However, experimental support for the existence of distinct and rare CSCs in human malignancies remain contentious, particularly in light of compelling evidence that cancer-propagating cells frequently fail to read out in existing human stem cell assays. Therefore, to unequivocally establish the existence and identity of human CSCs, the challenge is first to identify candidate CSCs, and to establish their unique ability to self-renew and replenish molecularly and functionally distinct non-tumorigenic progeny followed by functional in situ validation within the patients themselves. MethodsWe have in the hematological malignancy myelodysplastic syndromes (MDS) characterize candidate hematopoietic stem and progenitor stages in the bone marrow of low-intermediate risk MDS patients by flow cytometry. Distinct cell populations were functionally characterised for lineage commitment in standard colony forming cell (CFC) assays, and for self-renewal potential in long-term culture initiating cell (LTC-IC) assays and in immune-deficient (NSG) mice. Moreover, we tracked the cellular origin of all identified somatic genetic lesions identified in each patient by targeted next-generation sequencing of genomic DNA isolated from each purified MDS stem and progenitor cell population. ResultsIn low-intermediate risk MDS patients, regardless whether they were del(5q) (n=19) or non-del(5q) (n=11), we could identify rare but distinct Lin-CD34+CD38-CD90+CD45RA- candidate stem cells, granuclocyte-monocyte progenitors (GMPs) and megakaryocyte-erythroid progenitors (MEPs) with frequencies within total BM similar to that of normal age-matched controls. Global gene expression analysis by RNA sequencing of MDS stem cells, GMPs and MEPs suggested that these are molecularly distinct populations. Myeloid and erythroid gene expression signatures were restricted to the GMPs and MEPs, respectively, whereas a transcriptional stem cell signature was restricted to the MDS stem cells. GMPs and MEPs isolated from del(5q) (n=12) and non-del(5q) (n=8) MDS patients displayed lineage-restricted myeloid and erythroid differentiation potentials, respectively. Self-renewal in LTC-IC assay was restricted exclusively to MDS Lin-CD34+CD38-CD90+CD45RA- stem cells in del(5q) (n=11) and non-del(5q) (n=8) MDS patients. Xenotransplantation into NSG mice also confirmed that only Lin-CD34+CD38-CD90+CD45RA- MDS stem cells have in vivo self-renewal potential, and these experiments also demonstrated their ability to replenish downstream CMPs, GMPs and MEPs, establishing the hierarchical relationship of MDS stem and progenitor cells. Targeted DNA sequencing of 88 genes recurrently mutated in MDS and other myeloid malignancies was pursued to identify somatic genetic lesions within the bulk bone marrow of MDS patients (n=13). In total we identified 30 presumed genetic driver lesions, including del(5q) and mutations in key transcription factors (RUNX1), signalling pathways (JAK2, CSF3R), epigenetic regulators (TET2, ASXL1), apoptosis regulators (TP53), and spliceosome components (SF3B1, SRSF2, U2AF2, SRSF6). Importantly, in support of their unique ability to self-renew and replenish lineage-restricted MDS progenitors, all stable somatic genetic lesions identified could in each MDS patient be backtracked to the rare stem cell population as defined phenotypically by flow cytometry and functionally by LTC-IC or xenograft potential, unequivocally establishing their unique stem cell identity within the malignant clone. ConclusionsThese findings provide definitive evidence for the existence of rare and distinct stem cells in MDS, a finding with extensive implications for therapeutic strategies in MDS and other cancers whose existence might also strictly depend on the persistence of rare CSCs. MDS stem cells typically acquire multiple driver mutations, together conferring a competitive advantage over normal stem cells, while even in combination failing to inflict self-renewal ability on MDS myelo-erythroid progenitor cells. Disclosures:No relevant conflicts of interest to declare.