Ludmil B. Alexandrov

• BSc, MPhil, PhD
• Professor (Associate) at University of California, San Diego

Assessing smoke damage in cancer genomes We have known for over 60 years that smoking tobacco is one of the most avoidable risk factors for cancer. Yet the detailed mechanisms by which tobacco smoke damages the genome and creates the mutations that ultimately cause cancer are still not fully understood. Alexandrov et al. examined mutational signatu...

All cancers originate from a single cell that starts to behave abnormally, to divide uncontrollably, and, eventually, to invade adjacent tissues (1). The aberrant behavior of this single cell is due to somatic mutations—changes in the genomic DNA produced by the activity of different mutational processes (1). These mutational processes include expo...

During the course of a lifetime, somatic cells acquire mutations. Different mutational processes may contribute to the mutations accumulated in a cell, with each imprinting a mutational signature on the cell's genome. Some processes generate mutations throughout life at a constant rate in all individuals, and the number of mutations in a cell attri...

Targeting defects in the DNA repair machinery of neoplastic cells, for example, those due to inactivating BRCA1 and/or BRCA2 mutations, has been used for developing new therapies in certain types of breast, ovarian and pancreatic cancers. Recently, a mutational signature was associated with failure of double-strand DNA break repair by homologous re...

All cancers are caused by somatic mutations; however, understanding of the biological processes generating these mutations is limited. The catalogue of somatic mutations from a cancer genome bears the signatures of the mutational processes that have been operative. Here we analysed 4,938,362 mutations from 7,042 cancers and extracted more than 20 d...

Elucidating the role of microbes in precancer evolution could transform clinical risk prediction and management strategies. In the case of esophageal adenocarcinoma (EAC) progression, microbial communities have been detected across precancerous and neoplastic stages. However, unlike prior studies that statistically compare microbial abundances at s...

Inflammatory cytokine responsive apolipoprotein B mRNA-editing enzyme, catalytic polypeptide (APOBEC3) cytosine deaminases have been shown to be deregulated during cancer evolution, presenting as gene expression changes and inclusion of distinct C-to-T mutation patterns. However, the exact mechanisms by which APOBEC3 enzymes promote cancer initiati...

Mutational signatures in cancer genomes provide crucial insights into the etiology and progression of malignancies. While numerous signatures have been identified, many lack known causes, hindering our understanding of cancer development. This study presents a comprehensive analysis of mutational patterns induced by diverse environmental agents acr...

Introduction B cell acute lymphoblastic leukemia (B ALL) is the most common childhood malignancy with more than ninety percent cure rates and current research efforts are directed towards development of curative therapy in patients who relapse. Leukemia stem cell (LSC) persistence contributes to relapse. Whole genome sequencing and RNA sequencing (...

Myeloproliferative neoplasms (MPNs) are clonal hematopoietic stem cell (HSC)-derived disorders that often arise as a result of JAK2/STAT3 signal activating mutations. In the setting of microenvironmental inflammatory cytokines, MPNs also acquire splicing alterations that are associated with progression to rapidly lethal secondary acute myeloid leuk...

Tobacco smoke, alone or combined with alcohol, is the predominant cause of head and neck cancer (HNC). We explore how tobacco exposure contributes to cancer development by mutational signature analysis of 265 whole-genome sequenced HNC samples from eight countries. Six tobacco-associated mutational signatures were detected, including some not previ...

Understanding lung cancer evolution can identify tools for intercepting its growth. In a landscape analysis of 1024 lung adenocarcinomas (LUAD) with deep whole-genome sequencing integrated with multi-omic data, we identified 542 LUAD that displayed diverse clonal architecture. In this group, we observed an interplay between mobile elements, endogen...

(Abstracted from J Clin Oncol 2024;42:3550–3560) The field of precision medicine attempts to treat conditions with combinations that are tailored to the individual and the disease; precision oncology uses techniques to identify molecular defects in tumors and treat them with targeted interventions. For both breast and ovarian cancers, previous lite...

Colorectal cancer incidence rates vary geographically and have changed over time. Notably, in the past two decades, the incidence of early-onset colorectal cancer, affecting individuals under the age of 50 years, has doubled in many countries. The reasons for this increase are unknown. Here, we investigate whether mutational processes contribute to...

Oncogene amplification is a key driver of cancer pathogenesis. Both breakage fusion bridge (BFB) cycles and extrachromosomal DNA (ecDNA) can lead to high oncogene copy numbers, but the impact of BFB amplifications on intratumoral heterogeneity, treatment response, and patient survival remains poorly understood due to detection challenges with DNA s...

Mutations in somatic cells are inflicted by both extrinsic and intrinsic sources and contribute over time to cancer. Tobacco smoke contains chemical carcinogens that have been causatively implicated with cancers of the lung and head & neck. APOBEC family DNA cytosine deaminases have emerged as endogenous sources of mutation in cancer, with hallmark...

Mathematical modeling of somatic evolution, a process impacting both host cells and microbial communities in the human body, can capture important dynamics driving carcinogenesis. Here we considered models for esophageal adenocarcinoma (EAC), a cancer that has dramatically increased in incidence over the past few decades in Western populations, wit...

The Mutographs Cancer Grand Challenge team aimed to discover unknown causes of cancer through mutational epidemiology, an alliance of cancer epidemiology and somatic genomics. By generating whole-genome sequences from thousands of cancers and normal tissues from more than 30 countries on five continents, it discovered unsuspected mutagenic exposure...

Most of the risk factors associated with chronic and complex diseases, such as cancer, stem from exogenous and endogenous exposures experienced throughout an individual’s life, collectively known as the exposome. These exposures can modify DNA, which can subsequently lead to the somatic mutations found in all normal and tumor tissues. Understanding...

Hepatocellular carcinoma (HCC) originates from differentiated hepatocytes undergoing compensatory proliferation in livers damaged by viruses or metabolic-dysfunction-associated steatohepatitis (MASH)¹. While increasing HCC risk², MASH triggers p53-dependent hepatocyte senescence³, which we found to parallel hypernutrition-induced DNA breaks. How th...

INTRODUCTION Leukemia stem cell (LSC) persistence contributes to relapse, which is the leading cause of death in pediatric patients with B cell acute lymphoblastic leukemia (B-ALL). As the most common childhood malignancy, identification of mechanisms of LSC persistence following therapy remains a pressing unmet medical need. Whole genome sequencin...

Introduction The International Space Station (ISS) is a uniquely accelerating environment to study micro- and macro-environmental stressors in the context of modeling human diseases by simulating inflammation, aging, immune dysfunction, and accumulation of mutations. Studies done in low earth orbit (LEO) may offer accelerated insights into human he...

Background: MCM8 and MCM9 are newly proposed cancer predisposition genes, linked to polyposis and early–onset cancer, in addition to their association with hypogonadism. Given the uncertain range of phenotypic manifestations and unclear cancer risk estimates, this study aimed to delineate the molecular and clinical characteristics of individuals wi...

Acral melanoma, which is not ultraviolet (UV)-associated, is the most common type of melanoma in several low- and middle-income countries including Mexico. Latin American samples are significantly underrepresented in global cancer genomics studies, which directly affects patients in these regions as it is known that cancer risk and incidence may be...

Background High‐grade endometrial cancers (EAC) are aggressive tumors with a high risk of progression after treatment. As EAC may harbor mutations in the RAS/MAPK pathways, we evaluated the preclinical in vitro and in vivo efficacy of avutometinib, a RAF/MEK clamp, in combination with the focal adhesion kinase (FAK) inhibitors defactinib or VS‐4718...

Treatment at a young age places survivors of childhood cancers at a significantly elevated risk of developing life-threatening conditions such as cardiac dysfunction and secondary neoplasms. To better define the genomic impact of cancer therapy in children, we studied a diverse cohort of childhood tumors that had been heavily treated with multiple...

Survivors of pediatric cancer face lifelong battles with severe morbidities, including a significant risk of recurrence. Pre-existing genetic variation within primary tumors give certain cell populations an evolutionary advantage, increasing the likelihood of treatment resistance and relapse. The rarity of pediatric cancer and limited clinical meta...

Colorectal carcinoma (CRC) is a common cause of mortality¹, but a comprehensive description of its genomic landscape is lacking2–9. Here we perform whole-genome sequencing of 2,023 CRC samples from participants in the UK 100,000 Genomes Project, thereby providing a highly detailed somatic mutational landscape of this cancer. Integrated analyses ide...

PURPOSE Cancers with homologous recombination deficiency (HRD) can benefit from platinum salts and poly(ADP-ribose) polymerase inhibitors. Standard diagnostic tests for detecting HRD require molecular profiling, which is not universally available. METHODS We trained DeepHRD, a deep learning platform for predicting HRD from hematoxylin and eosin (H...

Breast and ovarian cancers harboring homologous recombination deficiency (HRD) are sensitive to PARP inhibitors and platinum chemotherapy. Conventionally, detecting HRD involves screening for defects in BRCA1 , BRCA2 , and other relevant genes. Recent analyses have shown that HRD cancers exhibit characteristic mutational patterns due to the activit...

Tobacco usage is linked to multiple cancer types and accounts for a quarter of all cancer-related deaths. Tobacco smoke contains various carcinogenic compounds, including polycyclic aromatic hydrocarbons (PAH), though the mutagenic potential of many tobacco-related chemicals remains largely unexplored. In particular, the highly carcinogenic tobacco...

Lung cancer in never smokers (LCINS) accounts for up to 25% of all lung cancers and has been associated with exposure to secondhand tobacco smoke and air pollution in observational studies. Here, we evaluate the mutagenic exposures in LCINS by examining deep whole-genome sequencing data from a large international cohort of 871 treatment-naïve LCINS...

International differences in the incidence of many cancer types indicate the existence of carcinogen exposures that have not yet been identified by conventional epidemiology make a substantial contribution to cancer burden¹. In clear cell renal cell carcinoma, obesity, hypertension and tobacco smoking are risk factors, but they do not explain the g...

Tobacco smoke, alone or combined with alcohol, is the predominant cause of head and neck cancer (HNC). Here, we further explore how tobacco exposure contributes to cancer development by mutational signature analysis of 265 whole-genome sequenced HNC from eight countries. Six tobacco-associated mutational signatures were detected, including some not...

High-grade neuroendocrine cervical cancers (NETc) are exceedingly rare, highly aggressive tumors. We analyzed 64 NETc tumor samples by whole-exome sequencing (WES). Human papillomavirus DNA was detected in 65.6% (42/64) of the tumors. Recurrent mutations were identified in PIK3CA, KMT2D/MLL2, K-RAS, ARID1A, NOTCH2, and RPL10. The top mutated genes...

APOBEC enzymes are part of the innate immunity and are responsible for restricting viruses and retroelements by deaminating cytosine residues. Most solid tumors harbor different levels of somatic mutations attributed to the off-target activities of APOBEC3A (A3A) and/or APOBEC3B (A3B). However, how APOBEC3A/B enzymes shape the tumor evolution in th...

The development of mutational signatures defined individually in the contexts of single/double base substitutions, insertions and deletions, structural variants and copy number variation have led to improved understanding of cancer mutagenesis and potential for improved patient stratification. We hypothesized that combining these contexts into a mu...

Survivors of pediatric cancer face lifelong battles with severe morbidities, which includes a significant risk of recurrence. Pre-existing genetic variation within primary tumors may offer certain cell populations an evolutionary advantage, increasing the likelihood that some will be resistant to treatment. But the inherent complexity of the tumor...

Barrett’s esophagus (BE) is a non-obligate precursor of esophageal adenocarcinoma (EAC), often measuring multiple centimeters in length and characterized by columnar epithelium replacing normal squamous epithelium in the distal esophagus. Early studies in BE suggested that all cells within a patient’s Barrett’s segment are progenies of a single fou...

The geographical incidence of head and neck cancer (HNC) is heterogeneous, reflecting the prevalence of its main risk factors. Tobacco, either alone or combined with alcohol, is the predominant cause of HNC, while the potential of alcohol as an independent carcinogen is uncertain. Moreover, the etiology remains unknown for ~28% of cases. In this st...

Analysis of mutational signatures is a powerful approach for understanding the mutagenic processes that have shaped the evolution of a cancer genome. To evaluate the mutational signatures operative in a cancer genome, one first needs to quantify their activities by estimating the number of mutations imprinted by each signature, a process known as r...

Large-scale biorepositories and databases are essential to generate equitable, effective, and sustainable advances in cancer prevention, early detection, cancer therapy, cancer care, and surveillance. The Mutographs project has created a large genomic dataset and biorepository of over 7,800 cancer cases from 30 countries across five continents with...

Stem cell aging is accelerated by macroenvironmental and microenvironmental stressors, including inflammation. Previously, the NASA Twins study revealed inflammatory cytokine upregulation, chromosomal alterations, and telomere changes suggestive of accelerated aging in low-Earth orbit (LEO). To investigate the effects of spaceflight on human hemato...

The mutations found in a cancer genome are shaped by diverse processes, each displaying a characteristic mutational signature that may be influenced by the genome's architecture. While prior analyses have evaluated the effect of topographical genomic features on mutational signatures, there has been no computational tool that can comprehensively ex...

Arsenic enhances the carcinogenicity of ultraviolet radiation (UVR). However, the mechanisms of arsenic-driven oncogenesis are not well understood. Here, we utilize experimental systems to investigate the carcinogenic and mutagenic properties of co-exposure to arsenic and UVR. In vitro and in vivo exposures indicate that, by itself, arsenic is not...

Motivation Analysis of mutational signatures is a powerful approach for understanding the mutagenic processes that have shaped the evolution of a cancer genome. To evaluate the mutational signatures operative in a cancer genome, one first needs to quantify their activities by estimating the number of mutations imprinted by each signature. Results...

Oncogene amplification is a major driver of cancer pathogenesis. Breakage fusion bridge (BFB) cycles, like extrachromosomal DNA (ecDNA), can lead to high copy numbers of oncogenes, but their impact on intratumoral heterogeneity, treatment response, and patient survival are not well understood due to difficulty in detecting them by DNA sequencing. W...

Importance Proliferative verrucous leukoplakia (PVL) is an aggressive oral precancerous disease characterized by a high risk of transformation to invasive oral squamous cell carcinoma (OSCC), and no therapies have been shown to affect its natural history. A recent study of the PVL immune landscape revealed a cytotoxic T-cell–rich microenvironment,...

The single-stranded DNA cytosine-to-uracil deaminase APOBEC3B is an antiviral protein implicated in cancer. However, its substrates in cells are not fully delineated. Here APOBEC3B proteomics reveal interactions with a surprising number of R-loop factors. Biochemical experiments show APOBEC3B binding to R-loops in cells and in vitro. Genetic experi...

Background All cancers harbor somatic mutations in their genomes. In principle, mutations affecting between one and fifty base pairs are generally classified as small mutational events. Conversely, large mutational events affect more than fifty base pairs, and, in most cases, they encompass copy-number and structural variants affecting many thousan...

The somatic mutations found in a cancer genome are imprinted by different mutational processes. Each process exhibits a characteristic mutational signature, which can be affected by the genome architecture. However, the interplay between mutational signatures and topographical genomic features has not been extensively explored. Here, we integrate m...

International differences in the incidence of many cancer types indicate the existence of carcinogen exposures which make a substantial contribution to cancer burden, vary geographically, and have underlying agents thus far unidentified by conventional epidemiology. This pertains to clear cell renal cell carcinomas (ccRCC), for which obesity, hyper...

Chromothripsis, the shattering and imperfect reassembly of one (or a few) chromosome(s)¹, is an ubiquitous² mutational process generating localized and complex chromosomal rearrangements that drive genome evolution in cancer. Chromothripsis can be initiated by mis-segregation errors in mitosis3,4 or DNA metabolism5–7 that lead to entrapment of chro...

Whole genome sequencing (WGS) allows exploration of the complete compendium of oncogenic processes generating characteristic patterns of mutations. Mutational signatures provide clues to tumour aetiology and highlight potentially targetable pathway defects. Here, alongside single base substitution (SBS), double base substitution (DBS), small insert...

With the continued promise of immunotherapy for treating cancer, understanding how host genetics contributes to the tumor immune microenvironment (TIME) is essential to tailoring cancer screening and treatment strategies. Here, we study 1084 eQTLs affecting the TIME found through analysis of The Cancer Genome Atlas and literature curation. These TI...

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 c...

Epstein–Barr virus (EBV) is an oncogenic herpesvirus associated with several cancers of lymphocytic and epithelial origin1–3. EBV encodes EBNA1, which binds to a cluster of 20 copies of an 18-base-pair palindromic sequence in the EBV genome4–6. EBNA1 also associates with host chromosomes at non-sequence-specific sites⁷, thereby enabling viral persi...

Oncogene amplification on extrachromosomal DNA (ecDNA) drives rapid tumor evolution, treatment resistance, and poor outcomes for patients. Computational tools can detect ecDNA in whole-genome sequencing (WGS) data from biopsies. However, the lack of longitudinal studies tracking patients from pre-cancer to cancer have made it difficult to determine...

APOBEC enzymes are part of the innate immunity and are responsible for restricting viruses and retroelements by deaminating cytosine residues. Most solid tumors harbor different levels of somatic mutations attributed to the off-target activities of APOBEC3A (A3A) and/or APOBEC3B (A3B). However, how APOBEC3A/B interact with exogenous mutagenic proce...

Malignant pleural mesothelioma (MPM) is an aggressive cancer with rising incidence and challenging clinical management. Through a large series of whole-genome sequencing data, integrated with transcriptomic and epigenomic data using multiomics factor analysis, we demonstrate that the current World Health Organization classification only accounts fo...

Breast and ovarian cancers harboring homologous recombination deficiencies (HRD) can benefit from platinum-based chemotherapies and PARP inhibitors. Standard diagnostic tests for detecting HRD utilize molecular profiling, which is not universally available especially for medically underserved populations. Here, we trained a deep learning approach f...

Environmental co-exposures are widespread and are major contributors to carcinogenic mechanisms. Two well-established environmental agents causing skin cancer are ultraviolet radiation (UVR) and arsenic. Arsenic is a known co-carcinogen that enhances UVR's carcinogenicity. However, the mechanisms of arsenic co-carcinogenesis are not well understood...

Background All cancers harbor somatic mutations in their genomes. In principle, mutations affecting between one and fifty base pairs are generally classified as small mutational events. Conversely, large mutational events affect more than fifty base pairs, and, in most cases, they encompass copy-number and structural variants affecting many thousan...

Analysis of mutational signatures can reveal underlying molecular mechanisms of the processes that have imprinted the somatic mutations found in cancer genomes. Here, we analyze single base substitutions and small insertions and deletions in pediatric cancers encompassing 785 whole-genome sequenced tumors from 27 molecularly defined cancer subtypes...

Somatic mutations in cancer genomes are caused by multiple mutational processes, each of which generates a characteristic mutational signature1. Here, as part of the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium2 of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA), we characterized mutational signatures...

Serrated polyposis syndrome (SPS) is one of the most frequent polyposis syndromes characterized by an increased risk for developing colorectal cancer (CRC). Although SPS etiology has been mainly associated with environmental factors, germline predisposition to SPS could also be relevant for cases with familial aggregation or a family history of SPS...

Ultraviolet A light is commonly emitted by UV-nail polish dryers with recent reports suggesting that long-term use may increase the risk for developing skin cancer. However, no experimental evaluation has been conducted to reveal the effect of radiation emitted by UV-nail polish dryers on mammalian cells. Here, we show that irradiation by a UV-nail...

Li-Fraumeni syndrome (LFS) is a hereditary cancer predisposition syndrome associated with germline TP53 pathogenic variants. Here, we perform whole-genome sequence (WGS) analysis of tumors from 22 patients with TP53 germline pathogenic variants. We observe somatic mutations affecting Wnt, PI3K/AKT signaling, epigenetic modifiers and homologous reco...

Background: Carcinosarcoma of the ovary (OCS) and uterus (UCS) are rare highly aggressive malignancies. Ataxia-telangiectasia-and-Rad3-related (ATR) kinase and homologous recombination play a pivotal role in DNA damage repair. Homologous recombination deficiency (HRD) has been demonstrated in >30% of OCS/UCS. We investigated the preclinical activi...

Objectives Uterine leiomyosarcoma (uLMS) is a rare, aggressive gynecologic malignancy. Up to 51% of uLMS harbor somatic mutations in ATRX, a tumor suppressor in the transcription regulation pathway, which increase sensitivity to ATR inhibitors. We sought to investigate the in vivo activity of a novel ATR inhibitor, BAY 1895344, against ATRX altered...

To characterise the somatic alterations in colorectal cancer (CRC), we conducted whole-genome sequencing analysis of 2,023 tumours. We provide the most detailed high-resolution map to date of somatic mutations in CRC, and demonstrate associations with clinicopathological features, in particular location in the large bowel. We refined the mutational...

Although Barrett's metaplasia of the esophagus (BE) is the only known precursor lesion to esophageal adenocarcinomas (EACs), drivers of cellular transformation in BE remain incompletely understood. We use an artificial intelligence-guided network approach to study EAC initiation and progression. Key predictions are subsequently validated in a human...

Chromothripsis, the shattering and imperfect reassembly of one (or a few) chromosome(s)1, is an ubiquitous2 mutational process generating localized complex chromosomal rearrangements that drive genome evolution in cancer. Chromothripsis can be initiated by missegregation errors in mitosis3,4 or DNA metabolism5-7 that lead to entrapment of chromosom...

Background Up to 80% of cases of prostate cancer present with multifocal independent tumour lesions leading to the concept of a field effect present in the normal prostate predisposing to cancer development. In the present study we applied Whole Genome DNA Sequencing (WGS) to a group of morphologically normal tissue ( n = 51), including benign pros...

Mutational signature analysis is commonly performed in cancer genomic studies. Here, we present SigProfilerExtractor, an automated tool for de novo extraction of mutational signatures, and benchmark it against another 13 bioinformatics tools by using 34 scenarios encompassing 2,500 simulated signatures found in 60,000 synthetic genomes and 20,000 s...

Background Central conventional chondrosarcoma (CS) is the most common subtype of primary malignant bone tumour in adults. Treatment options are usually limited to surgery, and prognosis is challenging. These tumours are characterised by the presence and absence of IDH1 and IDH2 mutations, and recently, TERT promoter alterations have been reported...

Objectives: Carcinosarcoma (CS) of the ovary (OCS) and uterus (UCS) are highly aggressive malignancies, poorly responsive to currently available adjuvant treatment. Ataxia-telangiectasia and Rad3-related (ATR) kinase and homologous recombination play a pivotal role in DNA damage repair (DDR). Homologous recombination (HR) deficiency has been demons...