Paul Salomon Mischel

All Publications

• Coupling antigens from multiple subtypes of influenza can broaden antibody and T cell responses. Science (New York, N.Y.) Mallajosyula, V., Chakraborty, S., Sola, E., Fong, R. F., Shankar, V., Gao, F., Burrell, A. R., Gupta, N., Wagar, L. E., Mischel, P. S., Capasso, R., Staat, M. A., Chien, Y. H., Dekker, C. L., Wang, T. T., Davis, M. M. 2024; 386 (6728): 1389-1395

  Abstract

  The seasonal influenza vaccine contains strains of viruses from distinct subtypes that are grown independently and then combined. However, most individuals exhibit a more robust response to one of these strains and thus are vulnerable to infection by others. By studying a monozygotic twin cohort, we found that although prior exposure is a factor, host genetics are a stronger driver of subtype bias to influenza viral strains. We found that covalent coupling of heterologous hemagglutinin (HA) from different viral strains could largely eliminate subtype bias in an animal model and in a human tonsil organoid system. We proposed that coupling of heterologous antigens improves antibody responses across influenza strains by broadening T cell help, and we found that using this approach substantially improved the antibody response to avian influenza HA.

  View details for DOI 10.1126/science.adi2396

  View details for PubMedID 39700292

• Engineered extrachromosomal oncogene amplifications promote tumorigenesis. Nature Pradella, D., Zhang, M., Gao, R., Yao, M. A., Gluchowska, K. M., Cendon-Florez, Y., Mishra, T., La Rocca, G., Weigl, M., Jiao, Z., Nguyen, H. H., Lisi, M., Ozimek, M. M., Mastroleo, C., Chen, K., Grimm, F., Luebeck, J., Zhang, S., Zolli, A. A., Sun, E. G., Dameracharla, B., Zhao, Z., Pritykin, Y., Sigel, C., Chang, H. Y., Mischel, P. S., Bafna, V., Antonescu, C. R., Ventura, A. 2024

  Abstract

  Focal gene amplifications are among the most common cancer-associated mutations1 but have proven challenging to engineer in primary cells and model organisms. Here we describe a general strategy to engineer large (more than 1 Mbp) focal amplifications mediated by extrachromosomal DNAs (ecDNAs)2 in a spatiotemporally controlled manner in cells and in mice. By coupling ecDNA formation with expression of selectable markers, we track the dynamics of ecDNA-containing cells under physiological conditions and in the presence of specific selective pressures. We also apply this approach to generate mice harbouring Cre-inducible Myc- and Mdm2-containing ecDNAs analogous to those occurring in human cancers. We show that the engineered ecDNAs spontaneously accumulate in primary cells derived from these animals, promoting their proliferation, immortalization and transformation. Finally, we demonstrate the ability of Mdm2-containing ecDNAs to promote tumour formation in an autochthonous mouse model of hepatocellular carcinoma. These findings offer insights into the role of ecDNA-mediated gene amplifications in tumorigenesis. We anticipate that this approach will be valuable for investigating further unresolved aspects of ecDNA biology and for developing new preclinical immunocompetent mouse models of human cancers harbouring specific focal gene amplifications.

  View details for DOI 10.1038/s41586-024-08318-8

  View details for PubMedID 39695225

  View details for PubMedCentralID 2826709

• Enhancing transcription-replication conflict targets ecDNA-positive cancers. Nature Tang, J., Weiser, N. E., Wang, G., Chowdhry, S., Curtis, E. J., Zhao, Y., Wong, I. T., Marinov, G. K., Li, R., Hanoian, P., Tse, E., Mojica, S. G., Hansen, R., Plum, J., Steffy, A., Milutinovic, S., Meyer, S. T., Luebeck, J., Wang, Y., Zhang, S., Altemose, N., Curtis, C., Greenleaf, W. J., Bafna, V., Benkovic, S. J., Pinkerton, A. B., Kasibhatla, S., Hassig, C. A., Mischel, P. S., Chang, H. Y. 2024; 635 (8037): 210-218

  Abstract

  Extrachromosomal DNA (ecDNA) presents a major challenge for cancer patients. ecDNA renders tumours treatment resistant by facilitating massive oncogene transcription and rapid genome evolution, contributing to poor patient survival1-7. At present, there are no ecDNA-specific treatments. Here we show that enhancing transcription-replication conflict enables targeted elimination of ecDNA-containing cancers. Stepwise analyses of ecDNA transcription reveal pervasive RNA transcription and associated single-stranded DNA, leading to excessive transcription-replication conflicts and replication stress compared with chromosomal loci. Nucleotide incorporation on ecDNA is markedly slower, and replication stress is significantly higher in ecDNA-containing tumours regardless of cancer type or oncogene cargo. pRPA2-S33, a mediator of DNA damage repair that binds single-stranded DNA, shows elevated localization on ecDNA in a transcription-dependent manner, along with increased DNA double strand breaks, and activation of the S-phase checkpoint kinase, CHK1. Genetic or pharmacological CHK1 inhibition causes extensive and preferential tumour cell death in ecDNA-containing tumours. We advance a highly selective, potent and bioavailable oral CHK1 inhibitor, BBI-2779, that preferentially kills ecDNA-containing tumour cells. In a gastric cancer model containing FGFR2 amplified on ecDNA, BBI-2779 suppresses tumour growth and prevents ecDNA-mediated acquired resistance to the pan-FGFR inhibitor infigratinib, resulting in potent and sustained tumour regression in mice. Transcription-replication conflict emerges as a target for ecDNA-directed therapy, exploiting a synthetic lethality of excess to treat cancer.

  View details for DOI 10.1038/s41586-024-07802-5

  View details for PubMedID 39506153

• Coordinated inheritance of extrachromosomal DNAs in cancer cells. Nature Hung, K. L., Jones, M. G., Wong, I. T., Curtis, E. J., Lange, J. T., He, B. J., Luebeck, J., Schmargon, R., Scanu, E., Bruckner, L., Yan, X., Li, R., Gnanasekar, A., Chamorro Gonzalez, R., Belk, J. A., Liu, Z., Melillo, B., Bafna, V., Dorr, J. R., Werner, B., Huang, W., Cravatt, B. F., Henssen, A. G., Mischel, P. S., Chang, H. Y. 2024; 635 (8037): 201-209

  Abstract

  The chromosomal theory of inheritance dictates that genes on the same chromosome segregate together while genes on different chromosomes assort independently1. Extrachromosomal DNAs (ecDNAs) are common in cancer and drive oncogene amplification, dysregulated gene expression and intratumoural heterogeneity through random segregation during cell division2,3. Distinct ecDNA sequences, termed ecDNA species, can co-exist to facilitate intermolecular cooperation in cancer cells4. How multiple ecDNA species within a tumour cell are assorted and maintained across somatic cell generations is unclear. Here we show that cooperative ecDNA species are coordinately inherited through mitotic co-segregation. Imaging and single-cell analyses show that multiple ecDNAs encoding distinct oncogenes co-occur and are correlated in copy number in human cancer cells. ecDNA species are coordinately segregated asymmetrically during mitosis, resulting in daughter cells with simultaneous copy-number gains in multiple ecDNA species before any selection. Intermolecular proximity and active transcription at the start of mitosis facilitate the coordinated segregation of ecDNA species, and transcription inhibition reduces co-segregation. Computational modelling reveals the quantitative principles of ecDNA co-segregation and co-selection, predicting their observed distributions in cancer cells. Coordinated inheritance of ecDNAs enables co-amplification of specialized ecDNAs containing only enhancer elements and guides therapeutic strategies to jointly deplete cooperating ecDNA oncogenes. Coordinated inheritance of ecDNAs confers stability to oncogene cooperation and novel gene regulatory circuits, allowing winning combinations of epigenetic states to be transmitted across cell generations.

  View details for DOI 10.1038/s41586-024-07861-8

  View details for PubMedID 39506152

• Origins and impact of extrachromosomal DNA. Nature Bailey, C., Pich, O., Thol, K., Watkins, T. B., Luebeck, J., Rowan, A., Stavrou, G., Weiser, N. E., Dameracharla, B., Bentham, R., Lu, W., Kittel, J., Yang, S. Y., Howitt, B. E., Sharma, N., Litovchenko, M., Salgado, R., Hung, K. L., Cornish, A. J., Moore, D. A., Houlston, R. S., Bafna, V., Chang, H. Y., Nik-Zainal, S., Kanu, N., McGranahan, N., Genomics England Consortium, Flanagan, A. M., Mischel, P. S., Jamal-Hanjani, M., Swanton, C., Ambrose, J. C., Arumugam, P., Bevers, R., Bleda, M., Boardman-Pretty, F., Boustred, C. R., Brittain, H., Brown, M. A., Caulfield, M. J., Chan, G. C., Giess, A., Griffin, J. N., Hamblin, A., Henderson, S., Hubbard, T. J., Jackson, R., Jones, L. J., Kasperaviciute, D., Kayikci, M., Kousathanas, A., Lahnstein, L., Lakey, A., Leigh, S. E., Leong, I. U., Lopez, F. J., Maleady-Crowe, F., McEntagart, M., Minneci, F., Mitchell, J., Moutsianas, L., Mueller, M., Murugaesu, N., Need, A. C., O'Donovan, P., Odhams, C. A., Patch, C., Perez-Gil, D., Pereira, M. B., Pullinger, J., Rahim, T., Rendon, A., Rogers, T., Savage, K., Sawant, K., Scott, R. H., Siddiq, A., Sieghart, A., Smith, S. C., Sosinsky, A., Stuckey, A., Tanguy, M., Taylor Tavares, A. L., Thomas, E. R., Thompson, S. R., Tucci, A., Welland, M. J., Williams, E., Witkowska, K., Wood, S. M., Zarowiecki, M. 2024; 635 (8037): 193-200

  Abstract

  Extrachromosomal DNA (ecDNA) is a major contributor to treatment resistance and poor outcome for patients with cancer1,2. Here we examine the diversity of ecDNA elements across cancer, revealing the associated tissue, genetic and mutational contexts. By analysing data from 14,778 patients with39 tumour types from the 100,000 Genomes Project, we demonstrate that 17.1% of tumour samples contain ecDNA. We reveal a pattern highly indicative of tissue-context-based selection for ecDNAs, linking their genomic content to their tissue of origin. We show that not only is ecDNA a mechanism for amplification of driver oncogenes, but it alsoa mechanism that frequently amplifies immunomodulatory and inflammatory genes, such as those that modulate lymphocyte-mediated immunity and immune effector processes. Moreover, ecDNAs carrying immunomodulatory genes are associated with reduced tumour T cell infiltration. We identify ecDNAs bearing only enhancers, promoters and lncRNA elements, suggesting the combinatorial power of interactions between ecDNAs in trans. We alsoidentify intrinsic and environmental mutational processes linked to ecDNA, including those linked to its formation, such as tobacco exposure, and progression, such as homologous recombination repair deficiency. Clinically, ecDNA detection was associated with tumour stage, more prevalent after targeted therapy and cytotoxic treatments, and associated with metastases and shorter overall survival. These results shed light on why ecDNA is a substantial clinical problem that can cooperatively drive tumour growth signals, alter transcriptional landscapes and suppress the immune system.

  View details for DOI 10.1038/s41586-024-08107-3

  View details for PubMedID 39506150

• Disparate pathways for extrachromosomal DNA biogenesis and genomic DNA repair. Cancer discovery Rose, J. C., Belk, J. A., Wong, I. T., Luebeck, J., Horn, H. T., Daniel, B., Jones, M. G., Yost, K. E., Hung, K. L., Kolahi, K. S., Curtis, E. J., Kuo, C. J., Bafna, V., Mischel, P. S., Chang, H. Y. 2024

  Abstract

  Oncogene amplification on extrachromosomal DNA (ecDNA) is a pervasive driver event in cancer, yet our understanding of how ecDNA forms is limited. Here, we couple a CRISPR-based method for ecDNA induction with extensive characterization of newly formed ecDNA to examine their biogenesis. We find that DNA circularization is efficient, irrespective of 3D genome context, with formation of 800kb, 1 Mb, and 1.8 Mb ecDNAs reaching or exceeding 15%. We show non-homologous end joining and microhomology-mediated end joining both contribute to ecDNA formation, while inhibition of DNA-PKcs and ATM have opposing impacts on ecDNA formation. EcDNA and the corresponding chromosomal excision scar can form at significantly different rates and respond differently to DNA-PKcs and ATM inhibition. Taken together, our results support a model of ecDNA formation in which double strand break ends dissociate from their legitimate ligation partners prior to joining of illegitimate ends to form the ecDNA and excision scar.

  View details for DOI 10.1158/2159-8290.CD-23-1117

  View details for PubMedID 39109936

• Extrachromosomal DNA in cancer. Nature reviews. Cancer Yan, X., Mischel, P., Chang, H. 2024

  Abstract

  Extrachromosomal DNA (ecDNA) has recently been recognized as a major contributor to cancer pathogenesisthat is identified in most cancer types and isassociated with poor outcomes. When it wasdiscovered over 60years ago, ecDNA was considered to be rare, and its impact on tumour biology was not well understood. The application of modern imaging and computational techniques has yielded powerful new insights into the importance of ecDNA in cancer. The non-chromosomal inheritance of ecDNA during cell division results in high oncogene copy number, intra-tumoural genetic heterogeneity and rapid tumour evolution thatcontributes to treatment resistance and shorter patient survival. In addition, the circular architecture of ecDNA results in altered patterns of gene regulation that drive elevated oncogene expression, potentially enabling the remodelling of tumour genomes. The generation of clusters of ecDNAs, termed ecDNA hubs, results in interactions between enhancers and promoters in trans, yielding a new paradigm in oncogenic transcription. In this Review, we highlight the rapid advancements in ecDNA research, providing new insights into ecDNA biogenesis, maintenance andtranscription and itsrole in promoting tumour heterogeneity. To conclude, we delve into a set of unanswered questions whose answers will pave the way for the development of ecDNA targeted therapeutic approaches.

  View details for DOI 10.1038/s41568-024-00669-8

  View details for PubMedID 38409389

• Extrachromosomal DNA: Biogenesis and Functions in Cancer ANNUAL REVIEW OF CANCER BIOLOGY Curtis, E. J., Rose, J. C., Mischel, P. S., Chang, H. Y. 2024; 8: 135-153

  View details for DOI 10.1146/annurev-cancerbio-070620-092730

  View details for Web of Science ID 001278203900008

• Circular extrachromosomal DNA promotes tumor heterogeneity in high-risk medulloblastoma. Nature genetics Chapman, O. S., Luebeck, J., Sridhar, S., Wong, I. T., Dixit, D., Wang, S., Prasad, G., Rajkumar, U., Pagadala, M. S., Larson, J. D., He, B. J., Hung, K. L., Lange, J. T., Dehkordi, S. R., Chandran, S., Adam, M., Morgan, L., Wani, S., Tiwari, A., Guccione, C., Lin, Y., Dutta, A., Lo, Y. Y., Juarez, E., Robinson, J. T., Korshunov, A., Michaels, J. A., Cho, Y. J., Malicki, D. M., Coufal, N. G., Levy, M. L., Hobbs, C., Scheuermann, R. H., Crawford, J. R., Pomeroy, S. L., Rich, J. N., Zhang, X., Chang, H. Y., Dixon, J. R., Bagchi, A., Deshpande, A. J., Carter, H., Fraenkel, E., Mischel, P. S., Wechsler-Reya, R. J., Bafna, V., Mesirov, J. P., Chavez, L. 2023

  Abstract

  Circular extrachromosomal DNA (ecDNA) in patient tumors is an important driver of oncogenic gene expression, evolution of drug resistance and poor patient outcomes. Applying computational methods for the detection and reconstruction of ecDNA across a retrospective cohort of 481 medulloblastoma tumors from 465 patients, we identify circular ecDNA in 82 patients (18%). Patients with ecDNA-positive medulloblastoma were more than twice as likely to relapse and three times as likely to die within 5 years of diagnosis. A subset of tumors harbored multiple ecDNA lineages, each containing distinct amplified oncogenes. Multimodal sequencing, imaging and CRISPR inhibition experiments in medulloblastoma models reveal intratumoral heterogeneity of ecDNA copy number per cell and frequent putative 'enhancer rewiring' events on ecDNA. This study reveals the frequency and diversity of ecDNA in medulloblastoma, stratified into molecular subgroups, and suggests copy number heterogeneity and enhancer rewiring as oncogenic features of ecDNA.

  View details for DOI 10.1038/s41588-023-01551-3

  View details for PubMedID 37945900

  View details for PubMedCentralID 5334176

• Extrachromosomal DNA in the cancerous transformation of Barrett's oesophagus. Nature Luebeck, J., Ng, A. W., Galipeau, P. C., Li, X., Sanchez, C. A., Katz-Summercorn, A. C., Kim, H., Jammula, S., He, Y., Lippman, S. M., Verhaak, R. G., Maley, C. C., Alexandrov, L. B., Reid, B. J., Fitzgerald, R. C., Paulson, T. G., Chang, H. Y., Wu, S., Bafna, V., Mischel, P. S. 2023

  Abstract

  Oncogene amplification on extrachromosomal DNA (ecDNA) drives the evolution of tumours and their resistance to treatment, and is associated with poor outcomes for patients with cancer1-6. At present, it is unclear whether ecDNA is a later manifestation of genomic instability, or whether it can be an early event in the transition from dysplasia to cancer. Here, to better understand the development of ecDNA, we analysed whole-genome sequencing (WGS) data from patients with oesophageal ademocarcinoma (EAC) or Barrett's oesophagus. These data included 206 biopsies in Barrett's oesophagus surveillance and EAC cohorts from Cambridge University. We also analysed WGS and histology data from biopsies that were collected across multiple regions at 2 time points from 80 patients in a case-control study at the Fred Hutchinson Cancer Center. In the Cambridge cohorts, the frequency of ecDNA increased between Barrett's-oesophagus-associated early-stage (24%) and late-stage (43%) EAC, suggesting that ecDNA is formed during cancer progression. In the cohort from the Fred Hutchinson Cancer Center, 33% of patients who developed EAC had at least one oesophageal biopsy with ecDNA before or at the diagnosis of EAC. In biopsies that were collected before cancer diagnosis, higher levels of ecDNA were present in samples from patients who later developed EAC than in samples from those who did not. We found that ecDNAs contained diverse collections of oncogenes and immunomodulatory genes. Furthermore, ecDNAs showed increases in copy number and structural complexity at more advanced stages of disease. Our findings show that ecDNA can develop early in the transition from high-grade dysplasia to cancer, and that ecDNAs progressively form and evolve under positive selection.

  View details for DOI 10.1038/s41586-023-05937-5

  View details for PubMedID 37046089

  View details for PubMedCentralID 5334176

• Targeted profiling of human extrachromosomal DNA by CRISPR-CATCH. Nature genetics Hung, K. L., Luebeck, J., Dehkordi, S. R., Colon, C. I., Li, R., Wong, I. T., Coruh, C., Dharanipragada, P., Lomeli, S. H., Weiser, N. E., Moriceau, G., Zhang, X., Bailey, C., Houlahan, K. E., Yang, W., Gonzalez, R. C., Swanton, C., Curtis, C., Jamal-Hanjani, M., Henssen, A. G., Law, J. A., Greenleaf, W. J., Lo, R. S., Mischel, P. S., Bafna, V., Chang, H. Y. 2022

  Abstract

  Extrachromosomal DNA (ecDNA) is a common mode of oncogene amplification but is challenging to analyze. Here, we adapt CRISPR-CATCH, in vitro CRISPR-Cas9 treatment and pulsed field gel electrophoresis of agarose-entrapped genomic DNA, previously developed for bacterial chromosome segments, to isolate megabase-sized human ecDNAs. We demonstrate strong enrichment of ecDNA molecules containing EGFR, FGFR2 and MYC from human cancer cells and NRAS ecDNA from human metastatic melanoma with acquired therapeutic resistance. Targeted enrichment of ecDNA versus chromosomal DNA enabled phasing of genetic variants, identified the presence of an EGFRvIII mutation exclusively on ecDNAs and supported an excision model of ecDNA genesis in a glioblastoma model. CRISPR-CATCH followed by nanopore sequencing enabled single-molecule ecDNA methylation profiling and revealed hypomethylation of the EGFR promoter on ecDNAs. We distinguished heterogeneous ecDNA species within the same sample by size and sequence with base-pair resolution and discovered functionally specialized ecDNAs that amplify select enhancers or oncogene-coding sequences.

  View details for DOI 10.1038/s41588-022-01190-0

  View details for PubMedID 36253572

• Deciphering the evolutionary dynamics of extrachromosomal DNA in human cancer NATURE GENETICS Lange, J. T., Mischel, P. S. 2022

  View details for DOI 10.1038/s41588-022-01183-z

  View details for Web of Science ID 000860213100001

  View details for PubMedID 36151323

• Leveraging extrachromosomal DNA to fine-tune trials of targeted therapy for glioblastoma: opportunities and challenges. Nature reviews. Clinical oncology Noorani, I., Mischel, P. S., Swanton, C. 2022

  Abstract

  Glioblastoma evolution is facilitated by intratumour heterogeneity, which poses a major hurdle to effective treatment. Evidence indicates a key role for oncogene amplification on extrachromosomal DNA (ecDNA) in accelerating tumour evolution and thus resistance to treatment, particularly in glioblastomas. Oncogenes contained within ecDNA can reach high copy numbers and expression levels, and their unequal segregation can result in more rapid copy number changes in response to therapy than is possible through natural selection of intrachromosomal genomic loci. Notably, targeted therapies inhibiting oncogenic pathways have failed to improve glioblastoma outcomes. In this Perspective, we outline reasons for this disappointing lack of clinical translation and present the emerging evidence implicating ecDNA as an important driver of tumour evolution. Furthermore, we suggest that through detection of ecDNA, patient selection for clinical trials of novel agents can be optimized to include those most likely to benefit based on current understanding of resistance mechanisms. We discuss the challenges to successful translation of this approach, including accurate detection of ecDNA in tumour tissue with novel technologies, development of faithful preclinical models for predicting the efficacy of novel agents in the presence of ecDNA oncogenes, and understanding the mechanisms of ecDNA formation during cancer evolution and how they could be attenuated therapeutically. Finally, we evaluate the feasibility of routine ecDNA characterization in the clinic and how this process could be integrated with other methods of molecular stratification to maximize the potential for clinical translation of precision medicines.

  View details for DOI 10.1038/s41571-022-00679-1

  View details for PubMedID 36131011

• The evolutionary dynamics of extrachromosomal DNA in human cancers. Nature genetics Lange, J. T., Rose, J. C., Chen, C. Y., Pichugin, Y., Xie, L., Tang, J., Hung, K. L., Yost, K. E., Shi, Q., Erb, M. L., Rajkumar, U., Wu, S., Taschner-Mandl, S., Bernkopf, M., Swanton, C., Liu, Z., Huang, W., Chang, H. Y., Bafna, V., Henssen, A. G., Werner, B., Mischel, P. S. 2022

  Abstract

  Oncogene amplification on extrachromosomal DNA (ecDNA) is a common event, driving aggressive tumor growth, drug resistance and shorter survival. Currently, the impact of nonchromosomal oncogene inheritance-random identity by descent-is poorly understood. Also unclear is the impact of ecDNA on somatic variation and selection. Here integrating theoretical models of random segregation, unbiased image analysis, CRISPR-based ecDNA tagging with live-cell imaging and CRISPR-C, we demonstrate that random ecDNA inheritance results in extensive intratumoral ecDNA copy number heterogeneity and rapid adaptation to metabolic stress and targeted treatment. Observed ecDNAs benefit host cell survival or growth and can change within a single cell cycle. ecDNA inheritance can predict, a priori, some of the aggressive features of ecDNA-containing cancers. These properties are facilitated by the ability of ecDNA to rapidly adapt genomes in a way that is not possible through chromosomal oncogene amplification. These results show how the nonchromosomal random inheritance pattern of ecDNA contributes to poor outcomes for patients with cancer.

  View details for DOI 10.1038/s41588-022-01177-x

  View details for PubMedID 36123406

• Gene regulation on extrachromosomal DNA. Nature structural & molecular biology Hung, K. L., Mischel, P. S., Chang, H. Y. 2022

  Abstract

  Oncogene amplification on extrachromosomal DNA (ecDNA) is prevalent in human cancer and is associated with poor outcomes. Clonal, megabase-sized circular ecDNAs in cancer are distinct from nonclonal, small sub-kilobase-sized DNAs that may arise during normal tissue homeostasis. ecDNAs enable profound changes in gene regulation beyond copy-number gains. An emerging principle of ecDNA regulation is the formation of ecDNA hubs: micrometer-sized nuclear structures of numerous copies of ecDNAs tethered by proteins in spatial proximity. ecDNA hubs enable cooperative and intermolecular sharing of DNA regulatory elements for potent and combinatorial gene activation. The 3D context of ecDNA shapes its gene expression potential, selection for clonal heterogeneity among ecDNAs, distribution through cell division, and reintegration into chromosomes. Technologies for studying gene regulation and structure of ecDNA are starting to answer long-held questions on the distinct rules that govern cancer genes beyond chromosomes.

  View details for DOI 10.1038/s41594-022-00806-7

  View details for PubMedID 35948767

• Mapping clustered mutations in cancer reveals APOBEC3 mutagenesis of ecDNA. Nature Bergstrom, E. N., Luebeck, J., Petljak, M., Khandekar, A., Barnes, M., Zhang, T., Steele, C. D., Pillay, N., Landi, M. T., Bafna, V., Mischel, P. S., Harris, R. S., Alexandrov, L. B. 2022

  Abstract

  Clustered somatic mutations are common in cancer genomes and previous analyses reveal several types of clustered single-base substitutions, which include doublet- and multi-base substitutions1-5, diffuse hypermutation termed omikli6, and longer strand-coordinated events termed kataegis3,7-9. Here we provide a comprehensive characterization of clustered substitutions and clustered small insertions and deletions (indels) across 2,583 whole-genome-sequenced cancers from 30 types of cancer10. Clustered mutations were highly enriched in driver genes and associated with differential gene expression and changes in overall survival. Several distinct mutational processes gave rise to clustered indels, including signatures that were enriched in tobacco smokers and homologous-recombination-deficient cancers. Doublet-base substitutions were caused by at least 12 mutational processes, whereas most multi-base substitutions were generated by either tobacco smoking or exposure to ultraviolet light. Omikli events, which have previously been attributed to APOBEC3 activity6, accounted for a large proportion of clustered substitutions; however, only 16.2% of omikli matched APOBEC3 patterns. Kataegis was generated by multiple mutational processes, and 76.1% of all kataegic events exhibited mutational patterns that are associated with the activation-induced deaminase (AID)andAPOBEC3 family of deaminases. Co-occurrence of APOBEC3 kataegis and extrachromosomal DNA (ecDNA), termed kyklonas (Greek for cyclone), was found in 31% of samples with ecDNA. Multiple distinct kyklonic events were observed on most mutated ecDNA. ecDNA containing known cancer genes exhibited both positive selection and kyklonic hypermutation. Our results reveal the diversity of clustered mutational processes in human cancer and the role of APOBEC3 in recurrently mutating and fuelling the evolution of ecDNA.

  View details for DOI 10.1038/s41586-022-04398-6

  View details for PubMedID 35140399

• ecDNA hubs drive cooperative intermolecular oncogene expression. Nature Hung, K. L., Yost, K. E., Xie, L., Shi, Q., Helmsauer, K., Luebeck, J., Schopflin, R., Lange, J. T., Chamorro Gonzalez, R., Weiser, N. E., Chen, C., Valieva, M. E., Wong, I. T., Wu, S., Dehkordi, S. R., Duffy, C. V., Kraft, K., Tang, J., Belk, J. A., Rose, J. C., Corces, M. R., Granja, J. M., Li, R., Rajkumar, U., Friedlein, J., Bagchi, A., Satpathy, A. T., Tjian, R., Mundlos, S., Bafna, V., Henssen, A. G., Mischel, P. S., Liu, Z., Chang, H. Y. 2021

  Abstract

  Extrachromosomal DNA (ecDNA) is prevalent in human cancers and mediates high expression of oncogenes through gene amplification and altered gene regulation1. Gene induction typically involves cis-regulatory elements that contact and activate genes on the same chromosome2,3. Here we show that ecDNA hubs-clusters of around 10-100 ecDNAs within the nucleus-enable intermolecular enhancer-gene interactions to promote oncogene overexpression. ecDNAs that encode multiple distinct oncogenes form hubs in diverse cancer cell types and primary tumours. Each ecDNA is more likely to transcribe the oncogene when spatially clustered with additional ecDNAs. ecDNA hubs are tethered by the bromodomain and extraterminal domain (BET) protein BRD4 in a MYC-amplified colorectal cancer cell line. The BET inhibitor JQ1 disperses ecDNA hubs and preferentially inhibits ecDNA-derived-oncogene transcription. The BRD4-bound PVT1 promoter is ectopically fused to MYC and duplicated in ecDNA, receiving promiscuous enhancer input to drive potent expression of MYC. Furthermore, the PVT1 promoter on an exogenous episome suffices to mediate gene activation in trans by ecDNA hubs in a JQ1-sensitive manner. Systematic silencing of ecDNA enhancers by CRISPR interference reveals intermolecular enhancer-gene activation among multiple oncogene loci that are amplified on distinct ecDNAs. Thus, protein-tethered ecDNA hubs enable intermolecular transcriptional regulation and may serve as units of oncogene function and cooperative evolution and as potential targets for cancer therapy.

  View details for DOI 10.1038/s41586-021-04116-8

  View details for PubMedID 34819668

• Extrachromosomal DNA: An Emerging Hallmark in Human Cancer. Annual review of pathology Wu, S., Bafna, V., Chang, H. Y., Mischel, P. S. 2021

  Abstract

  Human genes are arranged on 23 pairs of chromosomes, but in cancer, tumor-promoting genes and regulatory elements can free themselves from chromosomes and relocate to circular, extrachromosomal pieces of DNA (ecDNA). ecDNA, because of its nonchromosomal inheritance, drives high-copy-number oncogene amplification and enables tumors to evolve their genomes rapidly. Furthermore, the circular ecDNA architecture fundamentally alters gene regulation and transcription, and the higher-order organization of ecDNA contributes to tumor pathogenesis. Consequently, patients whose cancers harbor ecDNA have significantly shorter survival. Although ecDNA was first observed more than 50 years ago, its critical importance has only recently come to light. In this review, we discuss the current state of understanding of how ecDNAs form and function as well as how they contribute to drug resistance and accelerated cancer evolution. Expected final online publication date for the Annual Review of Pathology: Mechanisms of Disease, Volume 17 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

  View details for DOI 10.1146/annurev-pathmechdis-051821-114223

  View details for PubMedID 34752712

• Targeting glioblastoma signaling and metabolism with a re-purposed brain-penetrant drug. Cell reports Bi, J., Khan, A., Tang, J., Armando, A. M., Wu, S., Zhang, W., Gimple, R. C., Reed, A., Jing, H., Koga, T., Wong, I. T., Gu, Y., Miki, S., Yang, H., Prager, B., Curtis, E. J., Wainwright, D. A., Furnari, F. B., Rich, J. N., Cloughesy, T. F., Kornblum, H. I., Quehenberger, O., Rzhetsky, A., Cravatt, B. F., Mischel, P. S. 2021; 37 (5): 109957

  Abstract

  The highly lethal brain cancer glioblastoma (GBM) poses a daunting challenge because the blood-brain barrier renders potentially druggable amplified or mutated oncoproteins relatively inaccessible. Here, we identify sphingomyelin phosphodiesterase 1 (SMPD1), an enzyme that regulates the conversion of sphingomyelin to ceramide, as an actionable drug target in GBM. We show that the highly brain-penetrant antidepressant fluoxetine potently inhibits SMPD1 activity, killing GBMs, through inhibition of epidermal growth factor receptor (EGFR) signaling and via activation of lysosomal stress. Combining fluoxetine with temozolomide, a standard of care for GBM, causes massive increases in GBM cell death and complete tumor regression in mice. Incorporation of real-world evidence from electronic medical records from insurance databases reveals significantly increased survival in GBM patients treated with fluoxetine, which was not seen in patients treated with other selective serotonin reuptake inhibitor (SSRI) antidepressants. These results nominate the repurposing of fluoxetine as a potentially safe and promising therapy for patients with GBM and suggest prospective randomized clinical trials.

  View details for DOI 10.1016/j.celrep.2021.109957

  View details for PubMedID 34731610

• Altered cellular metabolism in gliomas - an emerging landscape of actionable co-dependency targets. Nature reviews. Cancer Bi, J., Chowdhry, S., Wu, S., Zhang, W., Masui, K., Mischel, P. S. 2020; 20 (1): 57-70

  Abstract

  Altered cellular metabolism is a hallmark of gliomas. Propelled by a set of recent technological advances, new insights into the molecular mechanisms underlying glioma metabolism are rapidly emerging. In this Review, we focus on the dynamic nature of glioma metabolism and how it is shaped by the interaction between tumour genotype and brain microenvironment. Recent advances integrating metabolomics with genomics are discussed, yielding new insight into the mechanisms that drive glioma pathogenesis. Studies that shed light on interactions between the tumour microenvironment and tumour genotype are highlighted, providing important clues as to how gliomas respond to and adapt to their changing tissue and biochemical contexts. Finally, a road map for the discovery of potential new glioma drug targets is suggested, with the goal of translating these new insights about glioma metabolism into clinical benefits for patients.

  View details for DOI 10.1038/s41568-019-0226-5

  View details for PubMedID 31806884

• Circular ecDNA promotes accessible chromatin and high oncogene expression. Nature Wu, S., Turner, K. M., Nguyen, N., Raviram, R., Erb, M., Santini, J., Luebeck, J., Rajkumar, U., Diao, Y., Li, B., Zhang, W., Jameson, N., Corces, M. R., Granja, J. M., Chen, X., Coruh, C., Abnousi, A., Houston, J., Ye, Z., Hu, R., Yu, M., Kim, H., Law, J. A., Verhaak, R. G., Hu, M., Furnari, F. B., Chang, H. Y., Ren, B., Bafna, V., Mischel, P. S. 2019

  Abstract

  Oncogenes are commonly amplified on particles of extrachromosomal DNA (ecDNA) in cancer1,2, but our understanding of the structure of ecDNA and its effect on gene regulation is limited. Here, by integrating ultrastructural imaging, long-range optical mapping and computational analysis of whole-genome sequencing, we demonstrate the structure of circular ecDNA. Pan-cancer analyses reveal that oncogenes encoded on ecDNA are among the most highly expressed genes in the transcriptome of the tumours, linking increased copy number with high transcription levels. Quantitative assessment of the chromatin state reveals that although ecDNA is packaged into chromatin with intact domain structure, it lacks higher-order compaction that is typical of chromosomes and displays significantly enhanced chromatin accessibility. Furthermore, ecDNA is shown to have a significantly greater number of ultra-long-range interactions with active chromatin, which provides insight into how the structure of circular ecDNA affects oncogene function, and connects ecDNA biology with modern cancer genomics and epigenetics.

  View details for DOI 10.1038/s41586-019-1763-5

  View details for PubMedID 31748743

• Oncogene Amplification in Growth Factor Signaling Pathways Renders Cancers Dependent on Membrane Lipid Remodeling. Cell metabolism Bi, J., Ichu, T., Zanca, C., Yang, H., Zhang, W., Gu, Y., Chowdhry, S., Reed, A., Ikegami, S., Turner, K. M., Zhang, W., Villa, G. R., Wu, S., Quehenberger, O., Yong, W. H., Kornblum, H. I., Rich, J. N., Cloughesy, T. F., Cavenee, W. K., Furnari, F. B., Cravatt, B. F., Mischel, P. S. 2019

  Abstract

  Advances in DNA sequencing technologies have reshaped our understanding of the molecular basis of cancer, providing a precise genomic view of tumors. Complementary biochemical and biophysical perspectives of cancer point toward profound shifts in nutrient uptake and utilization that propel tumor growth and major changes in the structure of the plasma membrane of tumor cells. The molecular mechanisms that bridge these fundamental aspects of tumor biology remain poorly understood. Here, we show that the lysophosphatidylcholine acyltransferase LPCAT1 functionally links specific genetic alterations in cancer with aberrant metabolism and plasma membrane remodeling to drive tumor growth. Growth factor receptor-driven cancers are found to depend on LPCAT1 to shape plasma membrane composition through enhanced saturated phosphatidylcholine content that is, in turn, required for the transduction of oncogenic signals. These results point to a genotype-informed strategy that prioritizes lipid remodeling pathways as therapeutic targets for diverse cancers.

  View details for DOI 10.1016/j.cmet.2019.06.014

  View details for PubMedID 31303424

• NAD metabolic dependency in cancer is shaped by gene amplification and enhancer remodelling. Nature Chowdhry, S., Zanca, C., Rajkumar, U., Koga, T., Diao, Y., Raviram, R., Liu, F., Turner, K., Yang, H., Brunk, E., Bi, J., Furnari, F., Bafna, V., Ren, B., Mischel, P. S. 2019; 569 (7757): 570-575

  Abstract

  Precision oncology hinges on linking tumour genotype with molecularly targeted drugs1; however, targeting the frequently dysregulated metabolic landscape of cancer has proven to be a major challenge2. Here we show that tissue context is the major determinant of dependence on the nicotinamide adenine dinucleotide (NAD) metabolic pathway in cancer. By analysing more than 7,000 tumours and 2,600 matched normal samples of 19 tissue types, coupled with mathematical modelling and extensive in vitro and in vivo analyses, we identify a simple and actionable set of 'rules'. If the rate-limiting enzyme of de novo NAD synthesis, NAPRT, is highly expressed in a normal tissue type, cancers that arise from that tissue will have a high frequency of NAPRT amplification and be completely and irreversibly dependent on NAPRT for survival. By contrast, tumours that arise from normal tissues that do not express NAPRT highly are entirely dependent on the NAD salvage pathway for survival. We identify the previously unknown enhancer that underlies this dependence. Amplification of NAPRT is shown to generate a pharmacologically actionable tumour cell dependence for survival. Dependence on another rate-limiting enzyme of the NAD synthesis pathway, NAMPT, as a result of enhancer remodelling is subject to resistance by NMRK1-dependent synthesis of NAD. These results identify a central role for tissue context in determining the choice of NAD biosynthetic pathway, explain the failure of NAMPT inhibitors, and pave the way for more effective treatments.

  View details for DOI 10.1038/s41586-019-1150-2

  View details for PubMedID 31019297

  View details for PubMedCentralID PMC7138021

• Extrachromosomal oncogene amplification in tumour pathogenesis and evolution. Nature reviews. Cancer Verhaak, R. G., Bafna, V., Mischel, P. S. 2019; 19 (5): 283-288

  Abstract

  Recent reports have demonstrated that oncogene amplification on extrachromosomal DNA (ecDNA) is a frequent event in cancer, providing new momentum to explore a phenomenon first discovered several decades ago. The direct consequence of ecDNA gains in these cases is an increase in DNA copy number of the oncogenes residing on the extrachromosomal element. A secondary effect, perhaps even more important, is that the unequal segregation of ecDNA from a parental tumour cell to offspring cells rapidly increases tumour heterogeneity, thus providing the tumour with an additional array of responses to microenvironment-induced and therapy-induced stress factors and perhaps providing an evolutionary advantage. This Perspectives article discusses the current knowledge and potential implications of oncogene amplification on ecDNA in cancer.

  View details for DOI 10.1038/s41568-019-0128-6

  View details for PubMedID 30872802

  View details for PubMedCentralID PMC7168519

• Extrachromosomal oncogene amplification drives tumour evolution and genetic heterogeneity NATURE Turner, K. M., Deshpande, V., Beyter, D., Koga, T., Rusert, J., Lee, C., Li, B., Arden, K., Ren, B., Nathanson, D. A., Kornblum, H. I., Taylor, M. D., Kaushal, S., Cavenee, W. K., Wechsler-Reya, R., Furnari, F. B., Vandenberg, S. R., Rao, P., Wahl, G. M., Bafna, V., Mischel, P. S. 2017; 543 (7643): 122-+

  Abstract

  Human cells have twenty-three pairs of chromosomes. In cancer, however, genes can be amplified in chromosomes or in circular extrachromosomal DNA (ecDNA), although the frequency and functional importance of ecDNA are not understood. We performed whole-genome sequencing, structural modelling and cytogenetic analyses of 17 different cancer types, including analysis of the structure and function of chromosomes during metaphase of 2,572 dividing cells, and developed a software package called ECdetect to conduct unbiased, integrated ecDNA detection and analysis. Here we show that ecDNA was found in nearly half of human cancers; its frequency varied by tumour type, but it was almost never found in normal cells. Driver oncogenes were amplified most commonly in ecDNA, thereby increasing transcript level. Mathematical modelling predicted that ecDNA amplification would increase oncogene copy number and intratumoural heterogeneity more effectively than chromosomal amplification. We validated these predictions by quantitative analyses of cancer samples. The results presented here suggest that ecDNA contributes to accelerated evolution in cancer.

  View details for DOI 10.1038/nature21356

  View details for Web of Science ID 000395671500045

  View details for PubMedID 28178237

  View details for PubMedCentralID PMC5334176

• Targeted therapy resistance mediated by dynamic regulation of extrachromosomal mutant EGFR DNA. Science (New York, N.Y.) Nathanson, D. A., Gini, B., Mottahedeh, J., Visnyei, K., Koga, T., Gomez, G., Eskin, A., Hwang, K., Wang, J., Masui, K., Paucar, A., Yang, H., Ohashi, M., Zhu, S., Wykosky, J., Reed, R., Nelson, S. F., Cloughesy, T. F., James, C. D., Rao, P. N., Kornblum, H. I., Heath, J. R., Cavenee, W. K., Furnari, F. B., Mischel, P. S. 2014; 343 (6166): 72-6

  Abstract

  Intratumoral heterogeneity contributes to cancer drug resistance, but the underlying mechanisms are not understood. Single-cell analyses of patient-derived models and clinical samples from glioblastoma patients treated with epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) demonstrate that tumor cells reversibly up-regulate or suppress mutant EGFR expression, conferring distinct cellular phenotypes to reach an optimal equilibrium for growth. Resistance to EGFR TKIs is shown to occur by elimination of mutant EGFR from extrachromosomal DNA. After drug withdrawal, reemergence of clonal EGFR mutations on extrachromosomal DNA follows. These results indicate a highly specific, dynamic, and adaptive route by which cancers can evade therapies that target oncogenes maintained on extrachromosomal DNA.

  View details for DOI 10.1126/science.1241328

  View details for PubMedID 24310612

  View details for PubMedCentralID PMC4049335