bims-tumhet Biomed News
on Tumor Heterogeneity
Issue of 2022–08–07
seventeen papers selected by
Sergio Marchini, Humanitas Research
  1. DiNAMIC.Duo: detecting somatic DNA copy number differences without a normal reference.
  2. cGAS-STING and the deadly CIN: how chronic inflammation represents a therapeutic vulnerability in chromosomally unstable cancers.
  3. SEMplMe: a tool for integrating DNA methylation effects in transcription factor binding affinity predictions.
  4. The impact of neoadjuvant chemotherapy on the tumor microenvironment in advanced high-grade serous carcinoma.
  5. A Systematic Review and Meta-Analysis on the Prognostic Value of BRCA Mutations, Homologous Recombination Gene Mutations, and Homologous Recombination Deficiencies in Cancer.
  6. Cancer: Slaying the 9-headed Hydra.
  7. Identification of a molecularly-defined subset of breast and ovarian cancer models that respond to WEE1 or ATR inhibition, overcoming PARP inhibitor resistance.
  8. Cancer cell states recur across tumor types and form specific interactions with the tumor microenvironment.
  9. Targeting KRAS mutant cancers: from druggable therapy to drug resistance.
  10. The vaginal microbiome is associated with endometrial cancer grade and histology.
  11. Single-cell analysis of a high-grade serous ovarian cancer cell line reveals transcriptomic changes and cell subpopulations sensitive to epigenetic combination treatment.
  12. KIAA1529 regulates RAD51 expression to confer PARP inhibitors resistance in ovarian cancer.
  13. DNA methylation: Precise modulation of chromatin structure and dynamics.
  14. Knowledge-graph-based cell-cell communication inference for spatially resolved transcriptomic data with SpaTalk.
  15. Sample-multiplexing approaches for single-cell sequencing.
  16. Circulating tumour DNA - looking beyond the blood.
  17. Practical Considerations for Single-Cell Genomics.
  1. Bioinformatics. 2022 Aug 04. pii: btac542. [Epub ahead of print]
    DiNAMIC.Duo: detecting somatic DNA copy number differences without a normal reference.
    Vonn Walter, Hyo Young Choi, Xiaobei Zhao, Yan Gao, Jeremiah Holt, D Neil Hayes.
       MOTIVATION: Somatic DNA copy number alterations (CNAs) arise in tumor tissue because of underlying genomic instability. Recurrent CNAs that occur in the same genomic region across multiple independent samples are of interest to researchers because they may contain genes that contribute to the cancer phenotype. However, differences in copy number states between cancers are also commonly of interest, for example when comparing tumors with distinct morphologies in the same anatomic location. Current methodologies are limited by their inability to perform direct comparisons of CNAs between tumor cohorts, and thus they cannot formally assess the statistical significance of observed copy number differences or identify regions of the genome where these differences occur.
    RESULTS: We introduce the DiNAMIC.Duo R package that can be used to identify recurrent copy number alterations in a single cohort or recurrent copy number differences between two cohorts, including when neither cohort is copy neutral. The package utilizes Python scripts for computational efficiency and provides functionality for producing figures and summary output files.
    AVAILABILITY: The DiNAMIC.Duo R package is available from CRAN at https://cran.r-project.org/web/packages/DiNAMIC.Duo/index.html.
    SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.
    DOI:  https://doi.org/10.1093/bioinformatics/btac542
  2. Trends Cancer. 2022 Jul 29. pii: S2405-8033(22)00159-5. [Epub ahead of print]
    cGAS-STING and the deadly CIN: how chronic inflammation represents a therapeutic vulnerability in chromosomally unstable cancers.
    Samuel F Bakhoum.
      Chromosomal instability (CIN) is a key genomic driver of human cancer. CIN generates genomic copy-number heterogeneity and tumor-derived inflammation. In a recent paper, Hong et al. identify the cGAS-STING innate immune pathway as a crucial dependency in cancer cells with CIN and pinpoint the IL6/STAT3 axis as a therapeutic vulnerability in these difficult-to-treat tumors.
    DOI:  https://doi.org/10.1016/j.trecan.2022.07.006
  3. BMC Bioinformatics. 2022 Aug 04. 23(1): 317
    SEMplMe: a tool for integrating DNA methylation effects in transcription factor binding affinity predictions.
    Sierra S Nishizaki, Alan P Boyle.
       MOTIVATION: Aberrant DNA methylation in transcription factor binding sites has been shown to lead to anomalous gene regulation that is strongly associated with human disease. However, the majority of methylation-sensitive positions within transcription factor binding sites remain unknown. Here we introduce SEMplMe, a computational tool to generate predictions of the effect of methylation on transcription factor binding strength in every position within a transcription factor's motif.
    RESULTS: SEMplMe uses ChIP-seq and whole genome bisulfite sequencing to predict effects of methylation within binding sites. SEMplMe validates known methylation sensitive and insensitive positions within a binding motif, identifies cell type specific transcription factor binding driven by methylation, and outperforms SELEX-based predictions for CTCF. These predictions can be used to identify aberrant sites of DNA methylation contributing to human disease.
    AVAILABILITY AND IMPLEMENTATION: SEMplMe is available from https://github.com/Boyle-Lab/SEMplMe .
    Keywords:  DNA methylation; Gene regulation; Noncoding variation; Open-source; Software; TFBS; Transcription factor
    DOI:  https://doi.org/10.1186/s12859-022-04865-x
  4. Oncogenesis. 2022 Jul 30. 11(1): 43
    The impact of neoadjuvant chemotherapy on the tumor microenvironment in advanced high-grade serous carcinoma.
    Yuanming Shen, Yan Ren, Kelie Chen, Yixuan Cen, Bo Zhang, Weiguo Lu, Junfen Xu.
      High-grade serous ovarian, fallopian tube or peritoneal carcinoma is an aggressive subtype of ovarian cancer that frequently develops resistance to chemotherapy. It remains contested whether the resistance is caused by the acquisition of novel molecular aberrations or alternatively through the selection of rare pre-existing tumor clones. To address this question, we applied single-cell RNA sequencing to depict the tumor landscape of 6 samples from a single case of advanced high-grade serous fallopian tube carcinoma during neoadjuvant chemotherapy (NACT). We analyzed a total of 32,079 single cells, with 17,249 cells derived from the pre-NACT multisite tumor tissue samples and 14,830 cells derived from the post-NACT multisite tumor tissue samples. We identified the diverse properties of the tumor, immune and stromal cell types between the pre-NACT and post-NACT tumors. The malignant epithelial cells displayed a high degree of intratumor heterogeneity in response to NACT. We showed that the primary resistant clone (clone 63) epithelial genotype was already present in the pre-NACT tumors, and was adaptively enriched after NACT. This clone 63 was correlated with a poor clinical prognosis. Furthermore, single-cell analysis of CD4+ T cells demonstrated that IL2RAhi-CCL22+-Tregs were selectively enriched in post-NACT tumors. Interestingly, this Treg subtype could recruit and enrich themselves through secreting the CCL22-CCR1 combination in pre-NACT and post-NACT tumors, and further express CD274 to suppress other CD4 and CD8 T cells through a CD274-PDCD1 axis in the post-NACT tumors, and this predicted an immunosuppressive state after NACT. Overall, our results provide important evidence for the adaptive resistance theory of HGSC, and for the potential development of therapeutic strategies to treat HGSC and improve the survival of patients with HGSC.
    DOI:  https://doi.org/10.1038/s41389-022-00419-1
  5. J Oncol. 2022 ;2022 5830475
    A Systematic Review and Meta-Analysis on the Prognostic Value of BRCA Mutations, Homologous Recombination Gene Mutations, and Homologous Recombination Deficiencies in Cancer.
    Changxia Shao, Michael S Chang, Fred C Lam, Andrew R Marley, Huilin Tang, Yiqing Song, Chelsey Miller, Madeline Brown, Isabella Wan, Jiali Han, Gboyega Adeboyeje.
      Patients with BRCA1/2 mutations (BRCAm), loss-of-function mutations in other homologous recombination repair (HRRm) genes, or tumors that are homologous recombination deficiency positivity (HRD+) demonstrate a robust response to PARPi therapy. We conducted a systematic literature review and meta-analysis to evaluate the prognostic value of BRCAm, HRRm, and HRD+ on overall survival (OS) among those treated by chemotherapy or targeted therapy other than PARPi across tumor types. A total of 135 eligible studies were included. Breast cancer (BC) patients with BRCA1/2m had a similar overall survival (OS) to those with wild-type BRCA1/2 (BRCA1/2 wt) across 18 studies. Ovarian cancer (OC) patients with BRCA1/2m had a significantly longer OS than those with BRCA1/2 wt across 24 studies reporting BRCA1m and BRCA2m, with an HR of 0.7 (0.6-0.8). Less OS data were reported for other tumors: 6 studies for BRCA2m compared with BRCA2 wt in prostate cancer with an HR of 1.9 (1.1-3.2) and 2 studies for BRCA1/2m compared with BRCA1/2 wt in pancreatic cancer with an HR of 1.5 (0.8-3.1). Only 4 studies reported HRD+ by either BRCA m or genomic instability score (GIS) ≥ 42 and OS by HRD status. The HR was 0.67 (0.43-1.02) for OS with HRD+ vs. HRD-. A total of 15 studies reported the association between HRRm and OS of cancers in which one or more HRR genes were examined. The HR was 1.0 (0.7-1.4) comparing patients with HRRm to those with HRR wild-type across tumors. Our findings are useful in improving the precision and efficacy of treatment selection in clinical oncology.
    DOI:  https://doi.org/10.1155/2022/5830475
  6. Ann Oncol. 2022 Aug 02. pii: S0923-7534(22)01861-0. [Epub ahead of print]
    Cancer: Slaying the 9-headed Hydra.
    J J Adashek, V Subbiah, C B Westphalen, A Naing, S Kato, R Kurzrock.
      Modern medicine continues to evolve, and the treatment armamentarium for various diseases grows more individualized across a breadth of medical disciplines. Cure rates for infectious diseases that were previously pan-fatal approach 100% because of the identification of the specific pathogen(s) involved and the use of appropriate combinations of drugs, where needed, to completely extinguish infection and hence prevent emergence of resistant strains. Similarly, with the assistance of technologies such as next-generation sequencing and immunomic analysis as part of the contemporary oncology armory, therapies can be tailored to each tumor. Importantly, molecular interrogation has revealed that metastatic cancers are distinct from each other and complex. Therefore, it is conceivable that rational personalized drug combinations will be needed to eradicate cancers, and eradication will be necessary to mitigate clonal evolution and resistance.
    Keywords:  cancer clinical trials; mixed response; novel therapeutics
    DOI:  https://doi.org/10.1016/j.annonc.2022.07.010
  7. Clin Cancer Res. 2022 Aug 03. pii: CCR-22-0568. [Epub ahead of print]
    Identification of a molecularly-defined subset of breast and ovarian cancer models that respond to WEE1 or ATR inhibition, overcoming PARP inhibitor resistance.
    Violeta Serra, Anderson T Wang, Marta Castroviejo-Bermejo, Urszula M Polanska, Marta Palafox, Andrea Herencia-Ropero, Gemma N Jones, Zhongwu Lai, Joshua Armenia, Filippos Michopoulos, Alba Llop-Guevara, Rachel Brough, Aditi Gulati, Stephen J Pettitt, Krishna C Bulusu, Jenni Nikkilä, Zena Wilson, Adina M Hughes, Paul W G Wijnhoven, Ambar Ahmed, Alejandra Bruna, Albert Gris-Oliver, Marta Guzman, Olga Rodriguez, Judit Grueso, Joaquín Arribas, Javier Cortés, Cristina Saura, Alan Lau, Susan E Critchlow, Brian Dougherty, Carlos Caldas, Gordon B Mills, J Carl Barrett, Josep V Forment, Elaine B Cadogan, Christopher J Lord, Cristina Cruz, Judith Balmaña, Mark J O'Connor.
       PURPOSE: PARP inhibitors (PARPi) induce synthetic lethality in homologous recombination repair (HRR) deficient tumors and are used to treat breast, ovarian, pancreatic and prostate cancers. Multiple PARPi resistance mechanisms exist, most resulting in restoration of HRR and protection of stalled replication forks. ATR inhibition was highlighted as a unique approach to reverse both aspects of resistance. Recently, however, a PARPi/WEE1 inhibitor combination demonstrated enhanced anti-tumor activity associated with the induction of replication stress, suggesting another approach to tackling PARPi resistance.
    EXPERIMENTAL DESIGN: We analyzed breast and ovarian patient-derived xenoimplant (PDX) models resistant to PARPi to quantify WEE1i and ATRi responses as single agents and in combination with PARPi. Biomarker analysis was conducted at the genetic and protein level. Metabolite analysis by mass spectrometry and nucleoside rescue experiments ex vivo were also conducted in patient-derived models.
    RESULTS: While WEE1i response was linked to markers of replication stress, including STK11/RB1 and phospho-RPA, ATRi response associated with ATM mutation. When combined with olaparib, WEE1i could be differentiated from the ATRi/olaparib combination, providing distinct therapeutic strategies to overcome PARPi resistance by targeting the replication stress response. Mechanistically, WEE1i sensitivity was associated with shortage of the dNTP pool and a concomitant increase in replication stress.
    CONCLUSION: Targeting the replication stress response is a valid therapeutic option to overcome PARPi resistance including tumors without an underlying HRR deficiency. These preclinical insights are now being tested in several clinical trials where the PARPi is administered with either the WEE1i or the ATRi.
    DOI:  https://doi.org/10.1158/1078-0432.CCR-22-0568
  8. Nat Genet. 2022 Aug;54(8): 1192-1201
    Cancer cell states recur across tumor types and form specific interactions with the tumor microenvironment.
    Dalia Barkley, Reuben Moncada, Maayan Pour, Deborah A Liberman, Ian Dryg, Gregor Werba, Wei Wang, Maayan Baron, Anjali Rao, Bo Xia, Gustavo S França, Alejandro Weil, Deborah F Delair, Cristina Hajdu, Amanda W Lund, Iman Osman, Itai Yanai.
      Transcriptional heterogeneity among malignant cells of a tumor has been studied in individual cancer types and shown to be organized into cancer cell states; however, it remains unclear to what extent these states span tumor types, constituting general features of cancer. Here, we perform a pan-cancer single-cell RNA-sequencing analysis across 15 cancer types and identify a catalog of gene modules whose expression defines recurrent cancer cell states including 'stress', 'interferon response', 'epithelial-mesenchymal transition', 'metal response', 'basal' and 'ciliated'. Spatial transcriptomic analysis linked the interferon response in cancer cells to T cells and macrophages in the tumor microenvironment. Using mouse models, we further found that induction of the interferon response module varies by tumor location and is diminished upon elimination of lymphocytes. Our work provides a framework for studying how cancer cell states interact with the tumor microenvironment to form organized systems capable of immune evasion, drug resistance and metastasis.
    DOI:  https://doi.org/10.1038/s41588-022-01141-9
  9. Mol Cancer. 2022 Aug 04. 21(1): 159
    Targeting KRAS mutant cancers: from druggable therapy to drug resistance.
    Chunxiao Zhu, Xiaoqing Guan, Xinuo Zhang, Xin Luan, Zhengbo Song, Xiangdong Cheng, Weidong Zhang, Jiang-Jiang Qin.
      Kirsten Rat Sarcoma Viral Oncogene Homolog (KRAS) is the most frequently mutated oncogene, occurring in a variety of tumor types. Targeting KRAS mutations with drugs is challenging because KRAS is considered undruggable due to the lack of classic drug binding sites. Over the past 40 years, great efforts have been made to explore routes for indirect targeting of KRAS mutant cancers, including KRAS expression, processing, upstream regulators, or downstream effectors. With the advent of KRAS (G12C) inhibitors, KRAS mutations are now druggable. Despite such inhibitors showing remarkable clinical responses, resistance to monotherapy of KRAS inhibitors is eventually developed. Significant progress has been made in understanding the mechanisms of drug resistance to KRAS-mutant inhibitors. Here we review the most recent advances in therapeutic approaches and resistance mechanisms targeting KRAS mutations and discuss opportunities for combination therapy.
    Keywords:  Combination therapy; Druggable; KRAS mutations; Resistance
    DOI:  https://doi.org/10.1186/s12943-022-01629-2
  10. Cancer Res Commun. 2022 Jun;2(6): 447-455
    The vaginal microbiome is associated with endometrial cancer grade and histology.
    Hesamedin Hakimjavadi, Sophia H George, Michael Taub, Leah V Dodds, Alex P Sanchez-Covarrubias, Marilyn Huang, J Matt Pearson, Brian M Slomovitz, Erin N Kobetz, Raad Gharaibeh, Ramlogan Sowamber, Andre Pinto, Srikar Chamala, Matthew P Schlumbrecht.
      The human microbiome has been strongly correlated with disease pathology and outcomes, yet remains relatively underexplored in patients with malignant endometrial disease. In this study, vaginal microbiome samples were prospectively collected at the time of hysterectomy from 61 racially and ethnically diverse patients from three disease conditions: 1) benign gynecologic disease (controls, n=11), 2) low-grade endometrial carcinoma (n=30), and 3) high-grade endometrial carcinoma (n=20). Extracted DNA underwent shotgun metagenomics sequencing, and microbial α and β diversities were calculated. Hierarchical clustering was used to describe community state types (CST), which were then compared by microbial diversity and grade. Differential abundance was calculated, and machine learning utilized to assess the predictive value of bacterial abundance to distinguish grade and histology. Both α- and β-diversity were associated with patient tumor grade. Four vaginal CST were identified that associated with grade of disease. Different histologies also demonstrated variation in CST within tumor grades. Using supervised clustering algorithms, critical microbiome markers at the species level were used to build models that predicted benign vs carcinoma, high-grade carcinoma versus benign, and high-grade versus low-grade carcinoma with high accuracy. These results confirm that the vaginal microbiome segregates not just benign disease from endometrial cancer, but is predictive of histology and grade. Further characterization of these findings in large, prospective studies is needed to elucidate their potential clinical applications.
    Keywords:  Endometrial cancer; high-grade; low-grade; metagenomics; microbiome
    DOI:  https://doi.org/10.1158/2767-9764.CRC-22-0075
  11. PLoS One. 2022 ;17(8): e0271584
    Single-cell analysis of a high-grade serous ovarian cancer cell line reveals transcriptomic changes and cell subpopulations sensitive to epigenetic combination treatment.
    Shruthi Sriramkumar, Tara X Metcalfe, Tim Lai, Xingyue Zong, Fang Fang, Heather M O'Hagan, Kenneth P Nephew.
      Ovarian cancer (OC) is a lethal gynecological malignancy with a five-year survival rate of only 46%. Development of resistance to platinum-based chemotherapy is a common cause of high mortality rates among OC patients. Tumor and transcriptomic heterogeneity are drivers of platinum resistance in OC. Platinum-based chemotherapy enriches for ovarian cancer stem cells (OCSCs) that are chemoresistant and contribute to disease recurrence and relapse. Studies examining the effect of different treatments on subpopulations of HGSOC cell lines are limited. Having previously demonstrated that combined treatment with an enhancer of zeste homolog 2 inhibitor (EZH2i) and a RAC1 GTPase inhibitor (RAC1i) inhibited survival of OCSCs, we investigated EZH2i and RAC1i combination effects on HGSOC heterogeneity using single cell RNA sequencing. We demonstrated that RAC1i reduced expression of stemness and early secretory marker genes, increased expression of an intermediate secretory marker gene and induced inflammatory gene expression. Importantly, RAC1i alone and in combination with EZH2i significantly reduced oxidative phosphorylation and upregulated Sirtuin signaling pathways. Altogether, we demonstrated that combining a RAC1i with an EZH2i promoted differentiation of subpopulations of HGSOC cells, supporting the future development of epigenetic drug combinations as therapeutic approaches in OC.
    DOI:  https://doi.org/10.1371/journal.pone.0271584
  12. Transl Oncol. 2022 Jul 30. pii: S1936-5233(22)00156-5. [Epub ahead of print]24 101497
    KIAA1529 regulates RAD51 expression to confer PARP inhibitors resistance in ovarian cancer.
    Yuan Qiao, Xuechen Yu, Bo Zhou, Kai Zhang, Juyuan Huang, Jing Liao.
      PARP inhibitors (PARPi) are currently used as first-line therapy for advanced and recurrent ovarian cancer, but the clinical efficacy is limited by drug resistance. We aimed to investigate the role of KIAA1529 in PARPi resistance in ovarian cancer. The expression of KIAA1529 was determined in ovarian cancer cells using qRT‒PCR and western blotting. Immunohistochemistry was used to examine the expression of KIAA1529 in primary ovarian cancer and recurrent ovarian cancer tissues. The effects of KIAA1529 on PARPi resistance were evaluated by knocking down KIAA1529 expression in ovarian cancer cells and assessing cell viability by CCK8 assays, apoptosis by flow cytometry, and homologous recombination (HR) repair by immunofluorescence analysis. The interaction between KIAA1529 and RAD51 was examined by western blotting. KIAA1529 was confirmed to be expressed in all ovarian cancer cell lines, and high expression of KIAA1529 was observed in recurrent ovarian cancer tissues. Inhibiting KIAA1529 expression increased the sensitivity of ovarian cancer cells to PARPi treatment. Furthermore, KIAA1529 increased the expression of the downstream effector RAD51 via Aurora-A, and HR was restored in ovarian cancer cells. This study demonstrates that KIAA1529 regulates RAD51 expression through Aurora-A to restore HR, which confers resistance to PARPi in ovarian cancer cells. These findings could provide a novel therapeutic target to overcome PARPi resistance in ovarian cancer.
    Keywords:  KIAA1529; Ovarian cancer; PARP inhibitors; RAD51; Resistance
    DOI:  https://doi.org/10.1016/j.tranon.2022.101497
  13. Curr Opin Struct Biol. 2022 Jul 29. pii: S0959-440X(22)00109-9. [Epub ahead of print]75 102430
    DNA methylation: Precise modulation of chromatin structure and dynamics.
    Shuxiang Li, Yunhui Peng, Anna R Panchenko.
      DNA methylation plays a vital role in epigenetic regulation in both plants and animals, and typically occurs at the 5-carbon position of the cytosine pyrimidine ring within the CpG dinucleotide steps. Cytosine methylation can alter DNA's geometry, mechanical and physico-chemical properties - thus influencing the molecular signaling events vital for transcription, replication and chromatin remodeling. Despite the profound effect cytosine methylation can have on DNA, the underlying atomistic mechanisms remain enigmatic. Many studies so far have produced controversial findings on how cytosine methylation dictates DNA flexibility and accessibility, nucleosome stability and dynamics. Here, we review the most recent experimental and computational studies that provide precise characterization of structure and function of cytosine methylation and its versatile roles in modulating DNA mechanics, nucleosome and chromatin structure, stability and dynamics. Moreover, the review briefly discusses the relationship between DNA methylation and nucleosome positioning, and the crosstalk between DNA methylation and histone tail modifications.
    DOI:  https://doi.org/10.1016/j.sbi.2022.102430
  14. Nat Commun. 2022 Jul 30. 13(1): 4429
    Knowledge-graph-based cell-cell communication inference for spatially resolved transcriptomic data with SpaTalk.
    Xin Shao, Chengyu Li, Haihong Yang, Xiaoyan Lu, Jie Liao, Jingyang Qian, Kai Wang, Junyun Cheng, Penghui Yang, Huajun Chen, Xiao Xu, Xiaohui Fan.
      Spatially resolved transcriptomics provides genetic information in space toward elucidation of the spatial architecture in intact organs and the spatially resolved cell-cell communications mediating tissue homeostasis, development, and disease. To facilitate inference of spatially resolved cell-cell communications, we here present SpaTalk, which relies on a graph network and knowledge graph to model and score the ligand-receptor-target signaling network between spatially proximal cells by dissecting cell-type composition through a non-negative linear model and spatial mapping between single-cell transcriptomic and spatially resolved transcriptomic data. The benchmarked performance of SpaTalk on public single-cell spatial transcriptomic datasets is superior to that of existing inference methods. Then we apply SpaTalk to STARmap, Slide-seq, and 10X Visium data, revealing the in-depth communicative mechanisms underlying normal and disease tissues with spatial structure. SpaTalk can uncover spatially resolved cell-cell communications for single-cell and spot-based spatially resolved transcriptomic data universally, providing valuable insights into spatial inter-cellular tissue dynamics.
    DOI:  https://doi.org/10.1038/s41467-022-32111-8
  15. Cell Mol Life Sci. 2022 Aug 05. 79(8): 466
    Sample-multiplexing approaches for single-cell sequencing.
    Yulong Zhang, Siwen Xu, Zebin Wen, Jinyu Gao, Shuang Li, Sherman M Weissman, Xinghua Pan.
      Single-cell sequencing is widely used in biological and medical studies. However, its application with multiple samples is hindered by inefficient sample processing, high experimental costs, ambiguous identification of true single cells, and technical batch effects. Here, we introduce sample-multiplexing approaches for single-cell sequencing in transcriptomics, epigenomics, genomics, and multiomics. In single-cell transcriptomics, sample multiplexing uses variants of native or artificial features as sample markers, enabling sample pooling and decoding. Such features include: (1) natural genetic variation, (2) nucleotide-barcode anchoring on cellular or nuclear membranes, (3) nucleotide-barcode internalization to the cytoplasm or nucleus, (4) vector-based barcode expression in cells, and (5) nucleotide-barcode incorporation during library construction. Other single-cell omics methods are based on similar concepts, particularly single-cell combinatorial indexing. These methods overcome current challenges, while enabling super-loading of single cells. Finally, selection guidelines are presented that can accelerate technological application.
    Keywords:  Cell Hashing; Multi-omics; Spatial transcriptomics; scATAC-seq; scRNA-seq
    DOI:  https://doi.org/10.1007/s00018-022-04482-0
  16. Nat Rev Clin Oncol. 2022 Aug 01.
    Circulating tumour DNA - looking beyond the blood.
    Ann Tivey, Matt Church, Dominic Rothwell, Caroline Dive, Natalie Cook.
      Over the past decade, various liquid biopsy techniques have emerged as viable alternatives to the analysis of traditional tissue biopsy samples. Such surrogate 'biopsies' offer numerous advantages, including the relative ease of obtaining serial samples and overcoming the issues of interpreting one or more small tissue samples that might not reflect the entire tumour burden. To date, the majority of research in the area of liquid biopsies has focused on blood-based biomarkers, predominantly using plasma-derived circulating tumour DNA (ctDNA). However, ctDNA can also be obtained from various non-blood sources and these might offer unique advantages over plasma ctDNA. In this Review, we discuss advances in the analysis of ctDNA from non-blood sources, focusing on urine, cerebrospinal fluid, and pleural or peritoneal fluid, but also consider other sources of ctDNA. We discuss how these alternative sources can have a distinct yet complementary role to that of blood ctDNA analysis and consider various technical aspects of non-blood ctDNA assay development. We also reflect on the settings in which non-blood ctDNA can offer distinct advantages over plasma ctDNA and explore some of the challenges associated with translating these alternative assays from academia into clinical use.
    DOI:  https://doi.org/10.1038/s41571-022-00660-y
  17. Curr Protoc. 2022 Aug;2(8): e498
    Practical Considerations for Single-Cell Genomics.
    Claire Regan, Jonathan Preall.
      The single-cell revolution in the field of genomics is in full bloom, with clever new molecular biology tricks appearing regularly that allow researchers to explore new modalities or scale up their projects to millions of cells and beyond. Techniques abound to measure RNA expression, DNA alterations, protein abundance, chromatin accessibility, and more, all with single-cell resolution and often in combination. Despite such a rapidly changing technology landscape, there are several fundamental principles that are applicable to the majority of experimental workflows to help users avoid pitfalls and exploit the advantages of the chosen platform. In this overview article, we describe a variety of popular single-cell genomics technologies and address some common questions pertaining to study design, sample preparation, quality control, and sequencing strategy. As the majority of relevant publications currently revolve around single-cell RNA-seq, we will prioritize this genomics modality in our discussion. © 2022 Wiley Periodicals LLC.
    Keywords:  genomics; scATAC-seq; scRNA-seq; sequencing; single-cell; transcriptomics
    DOI:  https://doi.org/10.1002/cpz1.498
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